WO2018139164A1

WO2018139164A1 - Method for controlling linking system for accumulator cells and power conversion devices, and power conditioning system

Info

Publication number: WO2018139164A1
Application number: PCT/JP2017/047125
Authority: WO
Inventors: 古田　太; 俊祐松永
Original assignee: 株式会社日立産機システム
Priority date: 2017-01-27
Filing date: 2017-12-27
Publication date: 2018-08-02
Also published as: JP6781637B2; JP2018121479A

Abstract

Provided are a PCS configuration for implementing independent operation parallel control together with other accumulator cells-PCS and equalizing the charging ratio of the accumulator cells, and a control method, in a linking system for a PV and accumulator cells. To this end, proposed is a method for controlling a linking system for accumulator cells and power conversion devices in which the accumulator cells and the power conversion devices are connected one-to-one, and combinations thereof are connected on an AC-side. In this method, control is carried out such that the accumulator cell charging ratio is equal, by each of the power conversion devices determining the charging/discharging speed of the corresponding accumulator cells according to the charging ratio of the accumulator cells, and allocating charging/discharging power using the power conversion devices in accordance with the charging/discharging speed.

Description

Control method for cooperative system of storage battery and power converter, and power conditioning system

The present invention relates to a power conversion device such as an inverter and a power conditioning system, and a control method thereof.

With the recent increase in interest in renewable energy and the introduction of a power purchase system by the government, solar power generation systems using solar cells (PV: Photovoltaic) are rapidly spreading. The system can easily obtain power if there is solar radiation, but it is susceptible to power fluctuations due to solar radiation conditions and cannot generate electricity at night. Therefore, a solar battery-storage battery cooperation system has been proposed in which a storage battery capable of storing electric power is connected to a solar battery, and the fluctuation of electric power generated by the solar battery is covered by charging / discharging of the storage battery.

Especially in areas where systems are weak, such as inland areas far away from remote islands and coastal power stations, and when systems are lost in the event of accidents or disasters, this linkage system is a means to always secure power for important loads. As expected.

The key to the configuration of the solar cell-storage battery cooperation system is a power conditioning system (PCS) device, which is a kind of power conversion device. The PCS is connected between the solar battery and the AC power line, and between the storage battery and the AC power line, and performs optimization of power generation conditions, charge / discharge operation, and the like. The PCSs are connected on the AC side, and exchange power between PCSs and supply power to important loads. Depending on the scale of the cooperation system, a plurality of PV-PCSs and a plurality of storage batteries-PCS are connected to the AC side.

When there are no grids, multiple PCSs can be linked by a master-slave system in which one PCS is operated independently as a master and the remaining PCS is operated as a slave, or all PCSs are coordinated. There is a parallel operation method that allows independent operation.

In the former, the master PCS establishes voltage and frequency throughout the system. Since the remaining slave PCS can specify the contribution power, the PV-PCS can pursue the maximum power, and the storage battery PCS can perform the charge / discharge operation according to the charging rate. However, if the master PCS is stopped, the entire system including the remaining slave PCS must be stopped. Maintenance of the master PCS and its DC power supply (mainly storage battery) becomes difficult, and the reliability of the system decreases.

On the other hand, as a technique for realizing the latter parallel operation, a technique called drooping control is described in Non-Patent Document 1 and Patent Document 1. In each PCS, a characteristic that droops the frequency and voltage according to the effective power and reactive power to be contributed is created in the PCS. A plurality of PCSs having drooping characteristics are driven in parallel as a master, and the drooping frequency and voltage are shared by each PCS to share the load power fairly. Since any PCS can be disconnected and paralleled again without stopping the system for maintenance, the reliability of the system is maintained for a long time.

WO2014-098104 Publication JP 2014-207790 A

When charging / discharging is repeated in a system in which a plurality of storage batteries and PCS are connected, the charging rate of the storage batteries of each PCS varies. The reason for this is the difference in the charging rate caused by variations in the characteristics of the storage battery itself, when the battery module is replaced by maintenance of the storage battery, or when the charge / discharge operation is temporarily stopped by the maintenance of the PCS.

However, there are cases where the battery controller is attached to the storage battery, and there are some that monitor the failure of the storage battery and grasp the charge rate. In that case, the variation between the storage cells constituting the storage battery is corrected by this controller. However, when looking at each PCS, the variation between storage batteries cannot be resolved.

In the drooping control described above, the drooping rate is determined according to the PCS rating, and power is evenly distributed to PCS of the same standard. The same applies to charging. In a system in which a plurality of storage batteries and a PCS are connected, if charging is performed with the same power while the charging rates of the storage batteries are different, the storage battery-PCS having the highest charging rate must be stopped. In the case of discharging, the storage battery-PCS with the lowest charging rate must be stopped. For this reason, PCS which can be drive | operated decreases and the reliability which was the advantage of parallel operation falls.

If it is not limited to drooping control, information on the charging rate of each storage battery is sent to the centralized control device, and is integrated into one, compared, and fed back to the charge / discharge control of each PCS. 2 However, the PCS (inverter) used in these needs to be in a state where the charge / discharge power of the storage battery can be controlled. Furthermore, since it is necessary to aggregate all the charging rates, a dedicated control device is necessary, and the configuration thereof needs to be changed depending on the number of PCSs to be connected. In other words, there are difficulties in maintaining reliability and realizing a flexible PCS configuration.

Accordingly, an object of the present invention is to provide a storage battery-PCS configuration in which a parallel control is performed together with a plurality of storage batteries-PCS, and the charge rate of the storage batteries is uniformly controlled among the plurality of PCSs in a PV / storage battery cooperation system without a system. It is to provide a control method and to make the PCS operable as much as possible to improve the reliability of the system.

One aspect of the present invention is a control method for a linked system of a storage battery and a power conversion device in which a storage battery and a power conversion device are connected one-to-one, and a plurality of these sets are connected on the AC side. In this method, each of the power converters determines the charge / discharge speed of the storage battery according to the charge rate of the corresponding storage battery, and allocates the charge / discharge power in each of the power converters according to the charge / discharge speed. Thus, the charge rate of the storage battery is controlled to be equal.

Another aspect of the present invention is a storage battery block and a power conditioning system that is connected to the storage battery block in a one-to-one manner to form a storage battery-PCS pair, and in a cooperative system in which a plurality of such sets are connected on the AC side. , A power conditioning system. This power conditioning system includes a switching element that converts DC to AC between the storage battery block and the AC side, a power calculation unit that calculates active power from the AC voltage and AC current on the AC side, and a corresponding storage battery block Reflecting the charging rate and the active power, an oscillator that generates a target frequency and a feedback control unit that feeds back the output of the oscillator to the switching element are provided.

When controlling multiple storage batteries-PCS in parallel, the charge / discharge power distribution ratio is changed according to the charge rate of each storage battery, so the variation in charge rate can be corrected, and more power is charged to the linked system. And more power can be discharged from the system.

The block diagram of the cooperation system of the storage battery block and PV panel via PCS. The table which shows the operation method of PCS in a 1st Example. The block diagram of the configuration of the storage battery block in the first embodiment. The block diagram of the PCS in the first embodiment. The block diagram of the configuration of the droop rate calculation unit in the first embodiment. The graph figure explaining the characteristic of the drooping function in a 1st Example. The graph figure explaining the characteristic of the drooping function in a 1st Example. The graph which shows the drooping characteristic of PCS in the parallel control which fixed drooping characteristic. The graph which shows the drooping characteristic of PCS in the parallel control which fixed drooping characteristic. The graph explaining the electric power characteristic with respect to the drooping rate in a 1st Example. The graph explaining the electric power characteristic with respect to the drooping rate in a 1st Example. The graph explaining the electric power characteristic with respect to the drooping rate in a 1st Example. The graph explaining the time change of a charging rate at the time of performing fixed droop rate control. The graph explaining the time change of the charging rate in a 1st Example. The block diagram of the PCS in the second embodiment. The block diagram of the configuration of the rated value correction calculator in the second embodiment. The graph explaining the characteristic of rating value correction in the 2nd example. The graph explaining the characteristic of rating value correction in the 2nd example. The graph explaining the electric power characteristic with respect to the rated value correction in a 2nd Example. The graph explaining the electric power characteristic with respect to the rated value correction in a 2nd Example. The graph explaining the electric power characteristic with respect to the rated value correction in a 2nd Example. The block diagram of the PCS in the third embodiment. The block diagram of the configuration of the droop rate calculation unit in the fourth embodiment.

Hereinafter, the present invention will be described by way of examples. This embodiment is an example using the present invention, and the present invention is not limited by this example. In the following, in parallel control of a system in which a storage battery and a PCS are connected one-to-one and a plurality of them are connected in parallel, each PCS determines a droop rate according to the charge rate of the corresponding accumulator, and based on the droop rate An example of charge / discharge control will be mainly described. In a more specific example, the self-sustained operation control with drooping characteristics is performed in the storage battery-PCS, and the droop rate of the frequency with respect to the active power increases monotonously in the case of charging with respect to the charging rate of the accumulator and monotonously in the case of discharge Set by a function of decrease.

In the structure of the invention described below, the same portions or portions having similar functions are denoted by the same reference numerals in different drawings, and redundant description may be omitted.

FIG. 1A shows an example of a system configuration in which a solar battery and a storage battery cooperate. Each of the solar cell (PV) panel 101 and the storage battery block 102 is connected to an important load 103 and a system (for example, 200 V, 50 Hz) 104 via the PCS 100. The PCS 100 serves as an interface between the DC side and the AC side and controls the direction and amount of power. The PCS synchronizes with the system by matching the frequency and voltage. The PCS 100 controls charging / discharging of the storage battery block 102 according to the direction of power. In addition, the PCS 100 supplies the power generated by the PV panel 101 to the AC side under the control of, for example, maximum power tracking (MPPT: Maximum Power Point Tracking).

FIG. 1B is a table showing an example of the operation method of the PCS 100 by comparing the present embodiment with the master-slave method. As shown in FIG. 1B, in the case of the master-slave system, one of the storage battery blocks 102-PCS100 operates independently as the master PCS, and the PV panel 101-PCS100 operates in an interconnected manner. In the present embodiment, all of the plurality of storage battery blocks 102-PCS100 perform a self-sustained operation, and perform parallel control among the plurality of PCSs. Therefore, unlike the master-slave method, the entire system is not affected by the stop of the master. Whether the PV panel 101-PCS 100 participates in parallel operation in a self-sustained operation is not limited in the present embodiment.

FIG. 1C shows a configuration example of the storage battery block 102. As shown in FIG. 1C, the storage battery block 102 includes one or a plurality of assembled batteries 107 and a battery controller 106 that monitors them. The assembled battery 107 has a configuration obtained by connecting the storage battery cells 105, which are the minimum unit of the storage battery, in series connection, parallel connection, or a combination thereof. FIG. 1C shows a configuration with only series connection.

The battery controller 106 monitors the state (voltage, current and temperature) of each storage battery cell 105 and determines whether the assembled battery 107 is normal or deteriorated. At the same time, the charging rate of each storage battery cell 105 is estimated from the monitored state quantity. If it is a simple controller, let the average value of the charging rate of each storage battery cell 105 be the charging rate of the assembled battery 107. In a multi-function controller, when there is a variation in the charging rate between the storage battery cells 105, a mechanism that partially discharges or charges only the specific storage battery cell 105 is used to reduce the variation in the assembled battery 107 and average The value is the charge rate of the assembled battery. The estimated charging rate is output from the storage battery block 102. The stored power is supplied via the PCS.

FIG. 2 shows the configuration of the PCS 100 connected to the storage battery block 102 in the first embodiment of the present invention. The PCS 100 includes a main circuit 210 and a control block 220. The main circuit 210 performs desired cross flow conversion between the AC side and the DC side (the PV panel 101 or the storage battery block 102 side) under the control of the control block 220. The control block 220 is a block that performs various calculations and processes for control, and can take the form of an information processing apparatus including an input device, an output device, a processing device, and a storage device. The information processing device realizes each block for processing data input from the input device by executing a program stored in the storage device, and outputs a processing result from the output device. The equivalent function can also be configured by hardware such as an FPGA (Field-Programmable gate array).

The direct current is pulse width modulated by the switching action of the semiconductor element 211 of the main circuit 210, the harmonics are removed by the reactor 212, and the alternating current is 50 Hz / 60 Hz, for example. After that, it goes to the AC side via the transformer 213.

The control block 220 includes a voltage feedback control unit 221 and a voltage compensation control unit 222 as a configuration for performing the independent operation control. Here, main circuit 210 is controlled so as to generate an AC voltage based on a rated voltage (for example, 200 V) and a rated frequency (for example, 50 Hz). The voltage on the AC side is monitored by the AC voltage sensor 214 and is controlled by the voltage feedback control unit 221 so that the rated voltage is obtained. Since the voltage may decrease due to the current flowing through the reactor 212, monitoring is performed by the alternating current sensor 215, and the values of the alternating voltage and the alternating current are input to the voltage compensation control unit 222 to compensate for the voltage drop. To implement. Further, as a mechanism for dropping the rated frequency and the rated voltage, an AC side voltage is input to the oscillator 223, and the output phase of the oscillator 223 is controlled to be in phase with the AC on the PCS side.

Furthermore, there is a drooping control unit 225 as a mechanism for drooping the rated frequency and rated voltage. The amount of power (active power and reactive power) supplied by the PCS to the load side (local system) can be calculated by obtaining the inner product and outer product from the voltage and current on the AC side measured by the power calculator 224. In accordance with these amounts, the droop control unit 225 reduces the droop rate from the rated frequency and the rated voltage value so that a predetermined droop rate is obtained. At this time, the fixed droop control that is reduced by applying a fixed value so as to obtain a certain droop rate from the rated value can be configured similarly to the configuration of the parallel control in Non-Patent Document 1, for example.

The control block 220 of the present embodiment basically follows the parallel control configuration. However, in this embodiment, the drooping characteristic is not fixed, but is controlled based on the charging rate and active power of the storage battery. That is, as shown in FIG. 2, the frequency droop rate is determined by the droop rate calculation unit 226 based on the charge rate output from the storage battery block 102 and the sign of the active power calculated by the power calculation unit 224. decide.

FIG. 3 shows the configuration of the droop rate calculation unit 226. The code information is extracted from the active power output from the power calculation unit 224 by the code extraction unit 301. This is used to determine whether the current operation of the PCS 100 is a charging operation or a discharging operation. On the other hand, the charging rate information from the storage battery block 102 is input to the discharging droop function unit 302 or the charging droop function unit 303. Each is converted into a droop rate, and the droop rate corresponding to the charge / discharge operation is selected by the selection unit 304 based on the code information described above.

FIG. 4 shows an example of the droop function. In this embodiment, a monotonically increasing function as shown in FIG. 4A is used as the charging function, and a monotonically decreasing function as shown in FIG. 4B is used as the discharging droop function. The horizontal axis indicates the charging rate of the storage battery, and the vertical axis indicates the drooping rate. In the charging function, as the charging rate increases, the drooping rate increases and the output decreases. The reverse is true for the discharge function. In either case, the operating range of the storage battery is determined in terms of the charging rate, the maximum droop rate M _MAX and the minimum droop rate M _MIN are determined, and the operation is performed at M, M ′, etc. within the range.

In order to explain the parallel control using the variable droop rate of the present embodiment, first, the parallel control using the fixed droop rate will be explained.

FIG. 5A is a diagram illustrating drooping characteristics for one PCS in parallel control. As the physical quantity to be drooped, the frequency f for the active power P and the AC voltage V for the reactive power Q are selected by simulating the characteristics of the synchronous generator. FIG. 5A shows a diagram showing changes in frequency with respect to active power. In the following description, active power and frequency will be mainly described as an example, but a change in AC voltage with respect to reactive power can be similarly described. The frequency is lowered at a certain rate with respect to the active power to be output. This ratio is called the droop rate. The droop rate is a reduction amount per electric power and corresponds to the inclination θ. Normally, the frequency drop (the amount of drooping) is set within a range that is permissible with respect to the rated (specification maximum) power value of the PCS.

FIG. 5B shows the behavior when two PCSs having this drooping characteristic are connected on the AC side and active power is supplied to the load. The relationship between the active power and the frequency of each PCS moves so that the frequencies coincide with each other, and the sharing of the active power is automatically performed. When both droop rates are the same, the active power is equally shared. When the rating is different, the slope of the straight line of the drooping characteristic is different, so the sharing ratio is accordingly. For this reason, electric power sharing according to the rated active power of each PCS becomes possible. The sharing of reactive power can also be explained in the same manner by dropping the AC voltage.

This embodiment has a feature that the power distribution is changed for each PCS by making the droop rate of the active power variable according to the charge rate of the storage battery block. Specifically, the fixed drooping characteristics shown in FIGS. 5A and 5B are made variable by droop rate control based on the active power and the charging rate shown in FIG.

FIG. 6A shows the drooping characteristics for one PCS when the droop rate is varied. The initial droop rate M ₀ and the rated droop rate M _N are set so that the decrease in frequency is within the allowable range for the rated (maximum usage) power value P _N , and the droop rate is variable within that range. The drooping rate M is determined according to the increase / decrease of the charging rate. The rated frequency is f _N, a decrease in the frequency tolerance rated droop and (Δf) _N.

More specifically, according to the charging rate and drooping rate characteristics of FIG. 4A, the charging rate is set to increase as the charging rate increases. On the other hand, according to the charge rate and droop rate characteristics of FIG. 4B, during discharge, the droop rate is set to decrease as the charge rate increases. Hereinafter, a case where two PCSs are operated in parallel in this state will be considered.

FIG. 6B shows that the storage battery block 1-PCS1 having the drooping characteristics and the storage battery block 2-PCS2 having the drooping characteristics are connected on the AC side, and both PCS receive the power (charging power) obtained by another means. It is a figure which shows the behavior in case. When the charging rates of both storage battery blocks are the same, the drooping rate is the same between PCS1 and PCS2, as shown in FIG. 5B, and even power distribution is performed and charging is performed evenly.

However, as shown in FIG. 6B, when the charging rate of the storage battery block 1 is smaller than the charging rate of the storage battery block 2, the drooping rate M1 of PCS1 is set smaller than the dripping rate M2 of PCS2. For this reason, since the electric power allocated to PCS1 becomes larger than the electric power allocated to PCS2 among charging electric power, charge of the storage battery block 1 advances from the storage battery block 2. FIG. Since the state in which the power distribution is different is continued until there is no difference between the charging rates of both storage batteries, the charging rates of both storage batteries are finally the same. For this reason, equal charge of a storage battery block is realizable.

6C, on the other hand, the storage battery block 2-PCS2 having this drooping characteristic is connected on the AC side in the same manner as the storage battery block 1-PCS1 having this drooping characteristic, and both PCS load the electric power (discharge power) stored in the storage battery. It is a figure which shows the behavior in the case of outputting to. When the charging rates of both storage battery blocks are the same, the drooping rate is the same between PCS1 and PCS2 as shown in FIG. 5B, and even power distribution is performed and uniform discharging is performed.

However, as shown in FIG. 6C, when the charging rate of the storage battery block 1 is larger than the charging rate of the storage battery block 2, the drooping rate of the PCS1 is set smaller than the PCS2. For this reason, since the electric power allocated to PCS1 becomes larger than the electric power allocated to PCS2 among discharge electric power, discharge of storage battery block 1 advances from storage battery block 2. Since the state in which the power distribution is different is continued until there is no difference between the charging rates of both storage batteries, the charging rates of both storage batteries are finally the same. For this reason, the uniform discharge of a storage battery block is realizable.

The charging rate of the storage battery blocks connected to each PCS can be equalized by having a mechanism for changing the power distribution according to the charging rate as described above. Returning to FIG. 2, a droop rate calculation unit 226 for changing the power distribution according to the charging rate is involved in the system from the power calculation unit 224 to the oscillator 223 that droops the frequency by the active power. Active power is generated by power exchange between the AC side and the storage battery block 102. On the other hand, reactive power is generated between the reactance and the capacitance constituting the ACS and the PCS 100. Since the active power is involved in charging / discharging the storage battery block 102, only the active power side may be used, and the reactive power side may be a conventional fixed drooping control.

FIG. 7A is an image of a change in the charging rate with time in the charging operation of the storage battery block 102. Since the charging power is uniform, the variation in the charging rate generated in the initial stage develops as it is and cannot be solved. The storage battery block that has reached full charge first must be stopped.

FIG. 7B is an image of the change in charging rate over time in the charging operation of the present embodiment. The power distribution changes according to the variation in the charging rate that occurs in the initial stage. Since the PCS of the storage battery block with a low charging rate charges more electric power and the PCS of the storage battery block with a high charging rate charges less electric power, the operation continues until the charging rates match. For this reason, parallel operation can be continued until both PCSs are fully charged.

Furthermore, the following advantages can be expected from changing the power distribution continuously according to the charging rate. Longer life can be expected depending on the type of battery such as a lithium ion battery. If it is not limited to parallel operation, the charging rate can be made uniform by turning on / off the PCS while observing the charging rate even in the prior art. However, the operation of turning on / off the charging / discharging operation places a burden on the battery electrode of a battery whose electrode structure changes in the charging / discharging operation, such as a Li ion battery. The burden can be reduced by changing charging / discharging electric power continuously like this example. As a result, the battery is prevented from deteriorating, leading to a long battery life.

Furthermore, the following operations can be expected by combining a PCS or power supply with other drooping characteristics and the storage battery block-PCS of this example. By setting the droop rate so that the minimum power required for maintaining the operation of the PCS is required when the storage battery block is fully charged, the charging power can be kept almost zero while continuing the operation of the PCS. Can do. For this reason, in the prior art, when the storage battery block is fully charged, the PCS has to be stopped, but the operation can be continued while suppressing charging. For this reason, it is not necessary to stop the PCS, and the reliability in the parallel operation can be maintained.

FIG. 8 shows the configuration of the PCS 100-2 connected to the storage battery block 102 in the second embodiment of the present invention. In this PCS, the frequency droop rate is not variable with respect to the charge rate, but the rated frequency value is variable. The main circuit 210 and its control are the same as those in the first embodiment, and the control block 220 of this example substantially follows the configuration of the self-sustained operation of the first embodiment. Furthermore, as a mechanism for carrying out parallel control, the drooping characteristic is added to the above-described independent operation control.

The drooping control unit 225 of this embodiment substantially follows the parallel control configuration shown in FIG. However, in the present embodiment, the rated value of the frequency is not fixed as shown in FIG. 2, and the correction value output from the rated value correction calculation unit 826 is added as shown in FIG. This correction value is determined based on the magnitude of the charging rate and the sign of the active power.

FIG. 9 shows the configuration of the rated value correction calculation unit 826. The code extraction unit 901 extracts the code information of the active power output from the power calculation unit 224. This is used to determine whether the current operation of the PCS 100-2 is a charging operation or a discharging operation. On the other hand, the charging rate information from the storage battery block 102 is input to the discharging correction function unit 902 or the charging correction function unit 903. Each is converted into a frequency correction value, and a correction value corresponding to the charge / discharge operation is selected by the selection unit 904 based on the code information described above.

FIG. 10 shows an example of the correction function. In this example, a monotonically increasing function as shown in FIG. 10A is used as the correction function for discharging, and a monotonically decreasing function as shown in FIG. 10B is used as the correcting function for charging. The horizontal axis shows the charging rate of the storage battery, and the vertical axis shows the frequency. In the correction function for discharging, the larger the charging rate, the more the frequency to be added to the rated frequency is increased and the output is increased. The reverse is true for the charging correction function. In either case, the operating range of the storage battery is determined based on the charging rate, the corresponding maximum frequency f _MAX and minimum frequency f _MIN are determined, and the operation is performed at f, f ′, etc. within the range. As described above, this embodiment has a feature of correcting the rated value of the frequency according to the charging rate of the storage battery block.

FIG. 11A shows drooping characteristics for one PCS when the frequency rating value (rated frequency) is varied. Compared to FIG. 6 of the first embodiment, the slope of the droop rate _MN is fixed, while the rated frequency is changed. It has a minimum frequency rating value that sets the rated droop amount (Δf) _N so that the decrease in frequency is within the allowable range for the initial frequency rating value f _N and the rated (maximum usage) power value P _N The frequency rating value f ₀ is variable within the range, and the frequency rating value is determined according to the increase / decrease of the charging rate. More specifically, according to the charging rate and frequency rated value characteristics of FIG. 10A, the frequency rated value is set to increase as the charging rate increases during discharging. On the other hand, according to the charging rate and frequency rated value characteristics of FIG. 10B, during charging, the frequency rating value is set to decrease as the charging rate increases.

Referring to FIG. 11B, consider a case where two PCSs are operated in parallel. In FIG. 11B, the storage battery block 2-PCS2 having this drooping characteristic is connected to the AC side in the same manner as the storage battery block 1-PCS1 having this drooping characteristic, and both PCS receive power (charging power) obtained by another means. It is a figure which shows the behavior in case. When the charging rates of both storage battery blocks are the same, the drooping rate is the same between PCS1 and PCS2, as shown in FIG. 5B, and even power distribution is performed and charging is performed evenly.

However, as shown in FIG. 11B, when the charging rate of the storage battery block 1 is smaller than the charging rate of the storage battery block 2, the drooping amount of the PCS1 must be smaller than the PCS2. For this reason, the frequency rating value f1 of PCS1 is made larger than the frequency rating value f2 of PCS2. In this way, even if the droop rate _MN is fixed, the power allocated to the PCS 1 out of the charging power is greater than the power allocated to the PCS 2, so the charging of the storage battery block 1 proceeds more than the storage battery block 2. Since the state in which the power distribution is different is continued until there is no difference between the charging rates of both storage batteries, the charging rates of both storage batteries are finally the same. For this reason, equal charge of a storage battery block is realizable.

FIG. 11C shows a case where storage battery block 2-PCS2 having this drooping characteristic is connected on the AC side in the same manner as storage battery block 1-PCS1 having this drooping characteristic, and both PCS receive power (discharge power) stored in the storage batteries. It is a figure which shows a behavior. When the charging rates of both storage battery blocks are the same, the drooping rate is the same between PCS1 and PCS2 as shown in FIG. 5B, and even power distribution is performed and uniform discharging is performed.

However, as shown in FIG. 7A, when the charging rate of the storage battery block 1 is larger than the charging rate of the storage battery block 2, the drooping amount of the PCS1 must be set smaller than the PCS2. For this reason, the frequency rating value f1 of PCS1 is made larger than the frequency rating value f2 of PCS2. In this way, even if the droop rate _MN is fixed, the electric power distributed to the PCS 1 out of the discharged electric power is larger than the electric power distributed to the PCS 2, so that the discharging of the storage battery block 1 proceeds more than the storage battery block 2. Since the state in which the power distribution is different is continued until there is no difference between the charging rates of both storage batteries, the charging rates of both storage batteries are finally the same. For this reason, equal charge of a storage battery block is realizable.

The image of correcting the variation in the charging rate between the storage battery blocks by the control of the present embodiment is the same as FIG. 7B of the first embodiment. The advantages of extending the life of the storage battery and continuing the parallel operation when the storage battery block is fully charged, as described in the first embodiment, can also be expected in this example.

FIG. 12 shows the configuration of the PCS 100-3 connected to the storage battery block 102 in the third embodiment of the present invention. This example is a method of changing the frequency droop rate in accordance with the change of the charging rate as in the first embodiment. However, in this embodiment, the charging rate is not input from the storage battery block 102, but the voltage on the DC side is acquired by the voltage sensor 1216, converted into the charging rate by the charging rate estimation unit 1217, and the charging rate is drooped. This is input to the rate calculation unit 1226. The charging rate estimation unit 1217 prepares a table indicating the relationship between the DC voltage of the battery to be used and the charging rate in advance. The charging rate is estimated from the voltage via the table.

The present embodiment is applied to a low-budget simple type block where a battery controller is not mounted on the storage battery block 102. In this case, the system configuration of the storage battery block-PCS is only the assembled battery 107 and the PCS 100 connected to the storage battery cell 105 and the DC wiring therebetween. Other operations are the same as those in the first embodiment. The same charging rate estimation method can also be applied to the case of the rated value correction in the second embodiment.

FIG. 13 shows the configuration of the droop rate calculation unit 1326 in the fourth embodiment of the present invention. This droop rate calculation unit 1326 can be used in place of, for example, the droop rate calculation unit 226 of FIG. This example is a method of changing the frequency droop rate in accordance with the change in the charging rate as in the first embodiment. In the first embodiment, the algorithm of the droop rate calculation unit 226 of each PCS 100 is assumed to be the same. However, in this embodiment, the drooping function can be selected according to the type of battery of the storage battery block 102 to be connected. Depending on the type and number of batteries, a set of droop functions for charging and discharging 1226 ₁ to 1226 _N is prepared. Based on the battery information (type and number) of the storage battery, an appropriate drooping function set is obtained from the selection unit 1201 and set as the droop rate.

Battery information is acquired from the storage battery block 102 together with the charging rate. Or you may have as data separately. By adopting this configuration, the portion depending on the storage battery block 102 is gathered in the storage battery block, and the PCS 100 has an advantage that the same can be applied. Other operations are the same as those in the first embodiment. The same configuration can also be applied to the rating value correction of the second embodiment.

In the fifth embodiment of the present invention, an example in which a part for calculating the drooping rate according to the charging rate is implemented in a PLC (Program Logic Controller) instead of a control block. In general, the PCS includes a PLC as a mechanism for operation control. Therefore, by incorporating this embodiment into the PLC, uniform charge / discharge can be realized without modifying the PCS.

As described in the above embodiment, when the storage battery-PCS is controlled in parallel, the charge / discharge power distribution ratio is changed according to the charge rate of each storage battery, so that the variation in the charge rate can be corrected. Specifically, when charging, a large amount of power is distributed to the storage battery-PCS having a lower charging rate. When discharging, a large amount of power is supplied from the storage battery-PCS having a higher charging rate. By this operation, the variation in the charging rate of each storage battery is reduced. For this reason, more power can be charged to the linkage system, and more power can be discharged from the system.

Thus, in the parallel control of the system in which a plurality of storage batteries-PCS are connected in parallel, the power to be charged / discharged of the system is distributed according to the charge / discharge speed determined by the PCS. Thereby, even if it is parallel control, it can prevent that charge of one storage battery runs out and the whole system | strain stops, and can control stably.

The present invention is not limited to the above-described embodiment, and includes various modifications. For example, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, it is possible to add, delete, and replace the configurations of other embodiments with respect to a part of the configurations of the embodiments.

The present invention can be used for a power conversion device such as an inverter or a power conditioning system and a control method thereof.

100: PCS, 101: PV panel, 102: storage battery block, 103: important load, 104: system, 105: storage battery cell, 106: battery controller, 107: assembled battery, 210: main circuit, 211: semiconductor element, 212: Reactor, 213: Transformer, 214: AC voltage sensor, 215: AC current sensor, 220: Control block, 221: Voltage feedback controller, 222: Voltage compensation controller, 223: Oscillator, 224: Power calculator, 225: Droop Control unit, 226: droop rate calculation unit, 301: sign extraction unit, 302: discharge droop function unit, 303: charge droop function unit, 304: selection unit, 726: rated value correction calculation unit, 802: charge correction Function, 803: correction function for discharge, 901: sign extraction unit, 1226: droop rate calculation unit, 1201: selection unit

Claims

In the control method of the cooperation system of the storage battery and the power conversion device in which the storage battery and the power conversion device are connected on a one-to-one basis, and a plurality of these sets are connected on the AC side.
Each of the power converters determines the charge / discharge speed of the storage battery according to the charge rate of the corresponding storage battery,
By assigning the charge / discharge power in each of the power converters according to the charge / discharge speed,
Control so that the charge rate of the storage battery is equal,
The control method of the cooperation system of the storage battery and power converter device characterized by the above-mentioned.
The linkage system of the storage battery and the power conversion device is one in which each of the power conversion devices is independently controlled in parallel operation without a system,
Reflecting the charging rate of the storage battery connected to each power converter in the drooping characteristics used for controlling the parallel operation,
The control method of the cooperation system of the storage battery and power converter device of Claim 1 characterized by the above-mentioned.
The drooping characteristic is a droop rate, and the method for determining the droop rate differs between charging and discharging the storage battery,
The relationship between the magnitude of the charging rate and the drooping rate is
At the time of charging, the drooping rate increases monotonously with respect to the charging rate,
At the time of discharging, the drooping rate is monotonously decreasing with respect to the charging rate.
The control method of the cooperation system of the storage battery and power converter device of Claim 2 characterized by the above-mentioned.
The drooping characteristic is a correction value for correcting the frequency rating value, and the method for determining the correction value differs between charging and discharging of the storage battery,
The relationship between the magnitude of the charging rate and the rated frequency value corrected with the corrected value is:
At the time of charging, the frequency rating value monotonously decreases with respect to the charging rate,
At the time of discharging, the frequency rating value is monotonously increasing with respect to the charging rate.
The control method of the cooperation system of the storage battery and power converter device of Claim 2 characterized by the above-mentioned.
The charge rate is associated with the storage battery and utilizes the output of a battery controller that monitors the voltage, current and temperature of the storage battery,
The control method of the cooperation system of the storage battery and power converter device of Claim 1 characterized by the above-mentioned.
The charging rate is estimated from the voltage of the storage battery,
The control method of the cooperation system of the storage battery and power converter device of Claim 1 characterized by the above-mentioned.
A storage battery block and a power conditioning system connected to the storage battery block on a one-to-one basis to form a storage battery-PCS set, and the power conditioning system in a cooperative system in which a plurality of the sets are connected on the AC side. ,
A switching element that converts direct current and alternating current between the storage battery block and the alternating current side;
A power calculator for calculating active power from the AC voltage and AC current on the AC side;
Reflecting the charging rate of the corresponding storage battery block and the active power, an oscillator that generates a target frequency,
A feedback control unit that feeds back the output of the oscillator to the switching element;
Power conditioning system with
A droop rate calculation unit that inputs the charge rate and the active power,
The droop rate calculation unit
A code extraction unit that extracts code information of the active power and determines whether the current operation is a charging operation or a discharging operation;
A drooping function unit for charging that outputs a drooping rate for charging corresponding to the charging rate, and
A discharge drooping function unit that outputs a drooping rate for discharging corresponding to the charging rate; and
A selection unit that outputs one of the droop rate for charging or the droop rate for discharge based on the sign information; and
Based on the output of the droop rate calculation unit, the target frequency is generated by drooping a rated frequency,
The power conditioning system according to claim 7.
A rated value correction calculation unit that inputs the charging rate and the active power,
The rated value correction calculation unit is:
A code extraction unit that extracts code information of the active power and determines whether the current operation is a charging operation or a discharging operation;
A charging correction function unit that outputs a charging correction value corresponding to the charging rate; and
A discharge correction function unit that outputs a discharge correction value corresponding to the charging rate;
A selection unit that outputs one of the correction value for charging or the correction value for discharging based on the code information; and
Based on the output of the rated value correction calculation unit, the rated frequency is corrected to generate the target frequency,
The power conditioning system according to claim 7.
A control unit that inputs the charging rate and the active power;
The control unit determines a control value based on the charging rate and the active power,
Adjusting the rated frequency based on the control value to generate the target frequency;
The power conditioning system according to claim 7.
The controller is
Detecting the sign of the active power;
Different control values are determined based on the detected codes;
The power conditioning system according to claim 10.
The power calculation unit calculates reactive power from the AC voltage and AC current on the AC side,
A voltage command value generation circuit for determining a voltage droop amount using the reactive power and generating a voltage command value based on the voltage droop amount;
The feedback control unit feeds back the voltage command value to the switching element;
The power conditioning system of claim 11.