CN101291069A - A photovoltaic grid-connected power generation system capable of online expansion - Google Patents

Abstract

The present invention is a photovoltaic grid-connected power generation system capable of realizing online expansion, which mainly includes at least one group of photovoltaic arrays, a centralized display control module, and two or more groups of grid-connected inverter modules. The DC bus realizes the transmission of electric energy, and the transmission of signal data is realized through the communication bus, and each grid-connected inverter module outputs electric energy to the grid bus; since the photovoltaic array group and the grid-connected inverter module perform MPPT centralized control and maximum Efficiency control, so that the whole machine can share a group of photovoltaic arrays, and can automatically adjust the opening and closing of the grid-connected inverter module by tracking the size of photovoltaic power, so that the system always works at the state of maximum efficiency; when users need to expand capacity, they can It is completed by adding photovoltaic array groups and grid-connected inverter modules; and because of the modular and hot-swappable design, it has certain practicability in maintenance and expansion.

Description

A photovoltaic grid-connected power generation system capable of online expansion

technical field

The invention relates to a photovoltaic grid-connected power generation system capable of realizing online expansion.

Background technique

Photovoltaic grid-connected power generation technology is a new technology emerging in recent years. Compared with traditional coal power and oil power, it has many advantages such as environmental protection and no energy consumption, and has become the focus of future development. However, as electronic products, there are also related problems of reliability and maintainability.

At present, the more popular photovoltaic power generation systems on the market all use single-machine operation, that is, the photovoltaic array can only supply power for one grid-connected inverter, and cannot supply power for multiple grid-connected inverters at the same time, because of the maximum power tracking. The distributed control method is used, so the sharing of photovoltaic arrays cannot be realized. When the user needs to expand the capacity, it can only be done by increasing the capacity of the photovoltaic array and grid-connected inverter, which obviously increases the secondary input cost. And the use of stand-alone work has significantly increased the amount of system work and maintenance. When a stand-alone unit works under low load, the conversion efficiency is obviously low.

With the popularization of photovoltaic power generation systems, small and medium-sized photovoltaic power generation systems enter households and villages, and the modular design of photovoltaic grid-connected inverters will become the trend of small and medium-sized photovoltaic power generation in the future.

Contents of the invention

The purpose of the present invention is to provide a photovoltaic grid-connected power generation system that can be expanded online according to needs, can realize the sharing of photovoltaic arrays, and adopts a modular design for grid-connected inverters.

The invention is a photovoltaic grid-connected power generation system capable of realizing online expansion, which mainly includes at least one group of photovoltaic arrays, a centralized display control module, and two or more groups of grid-connected inverter modules. The photovoltaic DC bus realizes the transmission of electric energy, and the transmission of signal data is realized through the communication bus, and each grid-connected inverter module outputs electric energy to the grid bus, among which:

The photovoltaic array outputs electric energy to the photovoltaic DC bus, outputs signal data to the communication bus and acquires control signal data from the communication bus;

The centralized display control module is mainly to carry out the centralized control of the maximum power point tracking of each photovoltaic array. According to the power of the photovoltaic array, it controls to turn on or off the grid-connected inverter module, so as to control the maximum efficiency and complete the integration with each grid-connected inverter. Variable module data communication, and centralized display of system operating parameters;

The grid-connected inverter module directly converts the output power of the photovoltaic array obtained from the photovoltaic DC bus into alternating current, and inputs it to the grid bus. The power incorporated into the grid is controlled by the centralized display control module. It is sent to the centralized display control module through the communication bus.

The centralized display control module is mainly composed of an SPI communication module, a signal acquisition control module, a grid-connected power calculation module, a centralized MPPT control module, a maximum efficiency control module, a state control and display module and a power supply; wherein:

The SPI communication module mainly completes the communication with other grid-connected inverter modules through the communication bus;

The signal acquisition control module mainly distinguishes and distributes the data transmitted by the SPI communication module, and decodes various signals and working state parameters required from the data for use by the grid-connected power calculation module or the state control and display module;

The grid-connected power calculation module accumulates and calculates the current signals decoded by the signal acquisition control module, and completes the calculation of the total grid-connected power of the whole machine and the power of each grid-connected inverter module. The calculation results are provided to the centralized MPPT control module or maximum power control module usage;

The centralized MPPT control module is used for the MPPT control of the whole machine, and tracks and scans the maximum power of at least one group of photovoltaic arrays, so as to determine its maximum power operating point and make the photovoltaic arrays output maximum power;

The maximum efficiency control module obtains the total power of the modules from the grid-connected power calculation module, and obtains the power adjustment parameters from the centralized MPPT control module, and then controls each grid-connected inverter module according to the number and working conditions of the grid-connected inverter modules , so that each working module is at full load to the maximum, thereby improving the efficiency of the whole machine;

The state control and display module mainly extracts the real-time working data of each grid-connected inverter module from the signal acquisition control module for display, so that users can understand the working state of the system;

The power supply is the control power supply part of the centralized display control module, which obtains electric energy from the photovoltaic DC busbar and the grid busbar, converts it, and supplies power to each control module.

Since the photovoltaic grid-connected power generation system of the present invention adopts a modular grid-connected inverter, by adding photovoltaic arrays and corresponding grid-connected inverter modules, online expansion can be realized, and due to the use of centralized maximum power tracking control In this way, the problem of mutual interference caused by the traditional distributed maximum power tracking control can be avoided, and the optimal maximum power tracking control can be realized. It has very practical use value for photovoltaic power generation system, avoids some shortcomings of traditional stand-alone work, can obtain the maximum conversion efficiency in any state, can maximize the use of solar energy, shorten maintenance time, and enhance the flexibility of use sex.

Description of drawings

Fig. 1 is the connection diagram of each part of the present invention;

Fig. 2 is the adjustment process of maximum power point tracking control in the present invention;

Fig. 3 is a control flowchart for realizing high-efficiency output in the present invention.

Detailed ways

As shown in Figure 1, the present invention mainly includes at least one group of photovoltaic arrays 1, a centralized display control module 2, and two or more groups of grid-connected inverter modules 3, each photovoltaic array 1 and each module are connected by a photovoltaic DC bus 4 To realize the transmission of electric energy, the transmission of signal data is realized through the communication bus 5, and each grid-connected inverter module 3 outputs electric energy to the grid bus 6, wherein:

The photovoltaic array 1 outputs electric energy to the photovoltaic DC bus 4, outputs signal data to the communication bus 5 and acquires control signal data from the communication bus 5;

The centralized display control module 2 is used for centralized maximum power point tracking (MPPT) control, maximum efficiency control, SPI communication and display. The master is to perform MPPT control on each photovoltaic array 1, and control the opening or closing of the grid-connected inverter module 3 according to the electric energy of the photovoltaic array 1, so as to control the maximum efficiency and complete the data communication with each grid-connected inverter module 3 , and centrally display system working parameters;

The grid-connected inverter module 3 directly converts the output power of the photovoltaic array 1 obtained from the photovoltaic DC bus 4 into alternating current, and inputs it to the grid bus 6, and the power incorporated into the grid is controlled by the centralized display control module 2, which The operating parameters and data are sent to the centralized display control module 2 through the communication bus 5 .

The centralized display control module 2 is mainly composed of an SPI communication module 201, a signal acquisition control module 202, a grid-connected power calculation module 203, a centralized MPPT control module 204, a maximum efficiency control module 205, a state control and display module 206 and a power supply 207. ;in:

The SPI communication module 201 completes communication with other grid-connected inverter modules 3 mainly through the communication bus 5 . The grid-connected inverter modules 3 are distinguished by addresses, and upload data to the SPI communication module 201 through the communication bus 5; the control of the centralized display control module 2 on each grid-connected inverter modules 3 is also distinguished by addresses, and the SPI communication The module 201 is electrically isolated from other control parts by optocouplers to reduce signal interference and has strong anti-interference characteristics.

The signal acquisition control module 202 mainly distinguishes and distributes the data transmitted by the SPI communication module 201, and decodes various signals and working state parameters required from the data for the grid-connected power calculation module 203 or the state control and display module 206 used.

The grid-connected power calculation module 203 accumulates and calculates the current signals decoded by the signal acquisition control module 202, and completes the calculation of the total grid-connected power of the whole machine and the power of each grid-connected inverter module 3, and the calculation results are provided to the centralized MPPT control module 204 or The maximum efficiency control module 205 is used.

The centralized MPPT control module 204 is used for the MPPT control of the whole machine, and uses the disturbance observation method to track and scan the maximum power of at least one group of photovoltaic arrays 1, so as to determine its maximum power operating point, so that the photovoltaic array 1 can output the maximum power; its MPPT The adjustment process is shown in Figure 2; first, obtain relevant data from the signal acquisition control module 202 and grid-connected power calculation module 203, and decide whether to adjust the grid-connected power to increase Or reduce the photovoltaic voltage, so as to realize the centralized control of the maximum power point.

The maximum efficiency control module 205 obtains the total power of the modules from the grid-connected power calculation module 203, obtains the power adjustment parameters from the centralized MPPT control module 204, and then inverts each grid-connected inverter module 3 according to the number and working conditions of the grid-connected inverter modules 3. Module 3 is controlled so that each working module is at full load to the maximum extent, thereby improving the working efficiency of the system.

The control flow is shown in Figure 3.

First, the total grid-connected power/rated power of a single grid-connected inverter module is obtained to obtain an integer N;

Then, each grid-connected inverter module 3 is controlled so that No. 1-No. N grid-connected inverter module 3 is in a full-load working state, and No. (N+1) grid-connected inverter module 3 is controlled by MPPT , turn off all the grid-connected inverter modules 3 whose number is larger than (N+1).

When the total rated power of the grid-connected inverter modules 3 of the entire system is much greater than the maximum power of the photovoltaic array, if all the grid-connected inverter modules are in the working state (that is, the module current sharing output scheme is adopted), low power conversion efficiency will occur low problem. Through the above-mentioned maximum efficiency control process, the present invention can make a corresponding number of grid-connected inverter modules 3 in a full-load working state according to the size of the total grid-connected power in real time, and close other redundant grid-connected inverter modules 3, thereby Improve the work efficiency of the whole system. In addition, when taking an integer N, the remaining part may be less than the rated power of a single module. Since MPPT adjustment is required, in order to avoid the problem of low power conversion efficiency caused by not allowing the module working at full load to perform MPPT adjustment , so another non-full-load grid-connected inverter module 3, that is, the (N+1) module is controlled by MPPT, so that the part of the power generated during MPPT regulation that is less than the rated power of the module can be integrated into the grid.

With the change of light intensity and ambient temperature, the electric energy of photovoltaic cells is changing all the time. The photovoltaic grid-connected power generation system of the present invention adopts MPPT technology, so at any moment there must be power disturbance and change, which is MPPT technology fixed features. Since grid-connected inverter modules 3 of Nos. 1 to N are all in the maximum power state (i.e. full-load working state), it can only rely on the grid-connected inverter modules 3 that are not at rated power to perform MPPT regulation, so that there will be no simultaneous MPPT adjustment causes the output power of each grid-connected inverter module 3 to be less than the rated power. The difference between the inverter module regulated by MPPT and other inverter modules working at full load is that the output power of the inverter module regulated by MPPT is always less than the rated power, because the grid-connected power is always changing in the process of MPPT regulation. . After adopting the output power control method of the present invention, all the inverter modules can be prevented from being disturbed at the same time to be in a non-full-load working state, thereby preventing the whole machine from being in a low-conversion-efficiency working state. Since a single grid-connected inverter module is independently regulated by MPPT, compared with the unified MPPT technology, the tracking accuracy of MPPT can be improved.

The status control and display module 206 mainly extracts the real-time working data of each grid-connected inverter module 3 from the signal acquisition control module 202 for display, so that the user can understand the working status of the system.

The power supply 207 is the control power supply part of the centralized display control module 2, which obtains electric energy from the photovoltaic DC bus 2 and the grid bus 6, converts it, and supplies power to each control module.

The focus of the design of the present invention is that the photovoltaic array group and the grid-connected inverter module are not in a one-to-one correspondence. They perform MPPT centralized control and maximum efficiency control through the centralized display control module, so that the whole machine (that is, all grid-connected inverter modules ) can share a group of photovoltaic square arrays, and can automatically adjust the opening and closing of the grid-connected inverter module by tracking the size of photovoltaic power, thus avoiding the problem of low power conversion efficiency caused by the use of module current sharing output, so that the system always works at maximum efficiency. When users need to expand capacity, it can be done by adding photovoltaic array groups and grid-connected inverter modules. Moreover, since the present invention adopts a modularized and hot-swappable design, it has certain practicability in maintenance, capacity expansion, and the like.

Claims (2)

1. A photovoltaic grid-connected power generation system capable of online expansion, characterized in that it includes at least one set of photovoltaic arrays, a centralized display control module, two or more sets of grid-connected inverter modules, each photovoltaic array and each module The transmission of electric energy is realized through the photovoltaic DC bus, and the transmission of signal data is realized through the communication bus. Each grid-connected inverter module outputs electric energy to the grid bus. Among them: The photovoltaic array outputs electric energy to the photovoltaic DC bus, outputs signal data to the communication bus and acquires control signal data from the communication bus; The centralized display control module is mainly to carry out the centralized control of the maximum power point tracking of each photovoltaic array. According to the power of the photovoltaic array, it controls to turn on or off the grid-connected inverter module, so as to control the maximum efficiency and complete the integration with each grid-connected inverter. Variable module data communication, and centralized display of system operating parameters; The grid-connected inverter module directly converts the output power of the photovoltaic array obtained from the photovoltaic DC bus into alternating current, and inputs it to the grid bus. The power incorporated into the grid is controlled by the centralized display control module. It is sent to the centralized display control module through the communication bus. 2. A photovoltaic grid-connected power generation system capable of online expansion according to claim 1, characterized in that: The centralized display control module is mainly composed of an SPI communication module, a signal acquisition control module, a grid-connected power calculation module, a centralized MPPT control module, a maximum efficiency control module, a state control and display module and a power supply; wherein: The SPI communication module mainly completes the communication with other grid-connected inverter modules through the communication bus; The signal acquisition control module mainly distinguishes and distributes the data transmitted by the SPI communication module, and decodes various signals and working state parameters required from the data for use by the grid-connected power calculation module or the state control and display module; The grid-connected power calculation module accumulates and calculates the current signals decoded by the signal acquisition control module, and completes the calculation of the total grid-connected power of the whole machine and the power of each grid-connected inverter module. The calculation results are provided to the centralized MPPT control module or maximum efficiency control module usage; The centralized MPPT control module is used for the MPPT control of the whole machine, and tracks and scans the maximum power of at least one group of photovoltaic arrays, so as to determine its maximum power operating point and make the photovoltaic arrays output maximum power; The maximum efficiency control module obtains the total power of the modules from the grid-connected power calculation module, and obtains the power adjustment parameters from the centralized MPPT control module, and then controls each grid-connected inverter module according to the number and working conditions of the grid-connected inverter modules , so that each working module is at full load to the maximum extent, so as to improve the conversion efficiency of the whole machine; The state control and display module mainly extracts the real-time working data of each grid-connected inverter module from the signal acquisition control module for display, so that users can understand the working state of the system; The power supply is the control power supply part of the centralized display control module, which obtains electric energy from the photovoltaic DC busbar and the grid busbar, converts it, and supplies power to each control module.

Images