WO2015036950A1

WO2015036950A1 - Power distribution hub

Info

Publication number: WO2015036950A1
Application number: PCT/IB2014/064423
Authority: WO
Inventors: Tiago ISIDORO FERNANDES; João MELO GUERREIRO
Original assignee: Frezite - Equipamentos Energéticos & Ambiente, Lda.
Priority date: 2013-09-12
Filing date: 2014-09-11
Publication date: 2015-03-19

Abstract

A method for controlling a power distribution hub, for distributing electrical power from one or more renewable energy sources. The power hub configured to carry out an algorithm and comprising a renewable power source connection, a mains connection, a backup power source connection and one or more loads, each with actuators control. The overall system determines when to adjust the power consumption, when to feed electrical load or loads, and doing that in terms of efficiency and needs.

Description

D E S C R I P T I O N

"POWER DISTRIBUTION HUB"

Technical field

The present invention relates to circuit arrangements or systems for supplying or distributing electric power; systems for storing electric energy, circuit arrangements for ac mains and dc distribution networks, by switching loads on to, or off from, network, in particular progressively balanced loading.

Background Art

Most renewable energy installations today are grid-tie, which means that all energy produced is placed on the main network. This is a problem to the network because this energy is not always needed and can lead to an excessive voltage increase on a specific area of the network. Today this is solved by limiting the amount of renewable source that can be installed.

The other types of applications are exclusively off-grid, which means that their purpose is to use only the energy produced locally many times only to a specific function. An example would be to pump water from a well in a location were no mains power is available. There are solutions that include energy accumulation on batteries as well as having a backup thermal power generator. These off grid solutions are normally composed of a renewable power source (photovoltaic solar panel, windmill, hydropower, etc.), a set of loads, an electronic controller and an energy accumulator (batteries, surface water tank for water accumulation, etc.).

GB2499345A describes a supervisory system controller for controlling and monitoring the generation of electrical energy from renewable sources and management methods for the storage of energy so generated, and interconnecting the energy-generating elements, storage and load. The supervisory system controller operates to maximum the power transfer from a wind turbine to a battery by automatically varying the threshold levels at which turbine dump loads are switched based on system inputs and measurements. GB2499345A describes managing the storage of energy by controlling the interconnections made between energy generating, storage, and load elements, the apparatus having a plurality of disconnect devices to allow independent disconnection of individual loads from a DC bus according to an algorithm that uses voltage levels, battery state of charge, time and override command.

GB2499345A does not describe connecting, disconnecting, redistributing power levels by individual loads and/or sources according to their efficiency maximizing renewable power source utilization, in particular such that the overall efficiency of the full system, (loads and energy source) is maximized, neither does it describe any kind of individual load control for this purpose.

US2011282514A1 describes a solar power forecasting system can provide forecasts of solar power output by photovoltaic plants and mitigation operations can include directing an energy management system to shed noncritical loads and/or ramping down the power produced by the photovoltaic plants at a rate that is acceptable to the utility to which the photovoltaic plants provide power.

US2011282514A1 does not describe connecting and/or disconnecting individual loads according to their efficiency, in particular such that the overall efficiency of the full system (loads and energy source) is maximized, neither does it describe any kind of individual load control for this purpose.

EP2325973A2 describes a control system a control device which calculates a charge/discharge efficiency of the electricity storage device and a working efficiency of each of several load devices, and regulates an amount of electrical power supplied from the electricity storage device to each of the load devices, so as to enhance an overall efficiency of the electricity storage device and the plurality of load.

EP2325973A2 only describes using an energy storage device, i.e. a battery, but does not describe a renewable source directly driving the loads, maximizing the efficiency by connecting and/or disconnecting and/or changing load level of individual loads according to their efficiency.

Summary

It is disclosed a method for adjusting the speed\load level between several loads such as the lowest power consumption for the required output is achieved increasing in such way the global system efficiency.

It is disclosed a method for controlling a power distribution hub for distributing electrical power from one or more renewable energy sources to one or more electrical loads supplying non-electrical outputs, said method comprising: adjusting the power consumption of the electrical load or loads, and/or switching on or off individual electrical loads, such that the total efficiency in terms of non-electrical output is maximized, feeding the electrical load or loads exclusively by the renewable energy source or sources, if the available power from the renewable energy source or sources is equal or higher than the required power by the one or more electrical loads for the required non-electrical outputs; or otherwise comprising feeding the electrical load or loads by the renewable energy source or sources in combination with one or more of: mains power, battery power, fuel generator.

It is disclosed a method for controlling a power distribution hub for distributing electrical power from one or more renewable energy sources to one or more electrical loads supplying non-electrical load storage, said method comprising feeding the electrical load or loads exclusively by the renewable energy source or sources, if the available non-electrical load storage is above a predetermined minimum threshold, or if the available power from the renewable energy source or sources is equal or higher than the required power by the one or more electrical loads to keep the non-electrical load storage from decreasing; or, otherwise comprising feeding the electrical load or loads by the renewable energy source or sources in combination with one or more of: mains power, battery power, fuel generator.

An embodiment comprises, when the electrical load or loads are exclusively fed by the renewable energy source or sources, adjusting the power consumption of the electrical load or loads such that it equals the available power from the renewable energy source or sources, if the available non-electrical load storage is below a predetermined maximum threshold.

An embodiment comprises, when the electrical load or loads are exclusively fed by the renewable energy source or sources, and if the available non-electrical load storage is above a predetermined maximum threshold, adjusting the power consumption of the electrical load or loads such that it equals the required power by the one or more electrical loads to keep the non-electrical load storage from decreasing.

An embodiment comprises, adjusting the power consumption of the electrical load or loads, and/or switching on or off individual electrical loads, such that the total efficiency in terms of non-electrical output is maximized.

It is also disclosed a power hub device comprising data processing module configured to carry out any of the above methods.

Description

The overall system working diagram is described in embodiment of figure 1. Several power sources are connected to a power hub which is also connected to a number of loads. Both loads, power sources and power hub are managed by a control method that prioritizes loads and power sources, as well as controlling each of them, to get the maximum output from the loads with the minimum input from the non-renewable power sources although, always assuring as much as possible the user minimum needs.

The disclosure includes the realization that electrical energy storage may not necessarily be the best option for optimizing renewable electrical energy sources. It is known that renewable electrical energy sources pose significant challenges - their power availability varies significantly and frequently, their power availability is very variable given their tension/current curves, significant non-linearities, etc. It is submitted that when load systems have themselves some type of non-electrical storage it may be more efficient in many situations to simply optimize load and source devices power curves and maximize efficiency by direct DC-DC connection without necessarily using inverters or DC-DC converters for storing electrical energy. Examples of storage at the load systems may be:

- pumping liquid into a reservoir - said reservoir acting as storage, such that instead of using available electrical power to charge a battery for future use, the available electrical power is optimally transmitted to the pump(s) for liquid storage in the reservoir for future use; for example, the reservoir may be slightly larger than normal usage would dictate.

- compressing air into a compress air tank - as above, instead of storing electrical energy in a battery for future use, the available electrical power is used to compress air in the tank for future use; for example the compressed air tank may be may be slightly larger or have a higher pressure limit than normal usage would dictate

- refrigerating a refrigerator and its contents - as above, instead of storing electrical energy in a battery for future use, the available electrical power is used to refrigerate the refrigerator and its contents for future use; for example, the refrigerator may be slightly larger, have a larger thermal inertia or simply have a lower minimum temperature (e.g. -25^C) than normal usage would dictate (e.g. -18^C). For these reasons, the power hub is preferably able to detect the total load being required (e.g. total pump load) and optionally must be able to vary the amount of power given to the load, in particular the amount of power given to each i ndividual load. Detecting the total load may be simply carried out by measuring the electrical characteristics (e.g. current) at the load inputs, the advantage being that there is no additional elements are required other than a single electrical connection to the load, in particular existing connections can be used.

Controlling the given power to the load, in particular the amount of power given to each individual load, may be carried out by controlling the electrical characteristics (e.g. tension) at the load inputs. Alternatively, the power give to each load may be controlled through a control circuit, for example by controlling the flow rate of a pump or compressor, e.g. by controlling the speed of an asynchronous motor.

The disclosure also includes the realization that a very robust and simple control may be carried out simply by defining thresholds levels of the non-electrical energy storage at the load(s) and by maximizing as much as possible the efficiency of the overall system - loads and renewable energy source(s) together.

The power hub, if multiple loads exist, must be able to switch these on or off or preferably set different power consumption levels individually.

The control method can also contain prediction routines based on historic values for both energy production and consumption and anticipate or delay load usage accordingly to avoid unnecessary consumption of non-renewable energy. The forecasting methods of US2011282514A1 may for example be used.

This control method can also monitor environmental variables in order to do a better management of the available energy.

One of the advantages of the present disclosure include is that the resulting system is extremely versatile as it can be used for plain off -grid applications, off-grid applications with backup, on-grid energy consumption reduction, on-grid backup and on-grid maximum simultaneous load management. The centralized power management where all the source control (MPPT, maximum power point tracking, algorithms), source prioritization, load management and control (ex. motor velocity reduction) is preferably done by the same equipment. This allows for a simpler layout on the installation as well as a more efficient result.

Main features of the disclosure:

- A power management system which controls not only the source, or the loads, but all of them, being able to improve efficiency by that.

- A Renewable Energy system that can have mains connection for function assurance.

- Control method for maximizing efficiency that comprises a MPPT for the source as well as simultaneous maximum efficiency for the loads.

An embodiment is presented in figure 2, comprising 2 renewable power sources - solar panels array and mains connection, 1 load and load inertia - air compressor + air tank.

The power hub selects the energy source based on the sensor feedback. When the power available from the renewable source is sufficient for the application (e.g. water flow required, compressor air flow required for maintaining air tank pressure) or the pressure level is above a predetermined minimum threshold, the compressor is only fed by the renewable, otherwise, mains energy is used.

Additionally, when using the renewable source, the power hub will adjust the compressor speed (or generically, adjust the power load level, for example of other applications, adjust the pump speed, or refrigerating power) so that the power consumption is adjusted to the maximum available power from the renewable power source. This situation will occur until a predetermined maximum pressure threshold is obtained and the compressor is either stopped or slowed down to meet only air consumption and avoid a pressure increase.

Another embodiment is presented in figure 3, comprising 2 power sources - solar panels array and mains connection, 2 or more loads - two pumps of equal electrical and mechanical attributes - power, efficiency, speed, etc. The power hub selects the energy source as in previous example considering only that in this case the feedback can come from different applications (multiple loads).

In this case, when using the renewable source, the power hub adjusts the total power of the two pumps according to the maximum power extractable from the renewable source.

The division of total available power between the pumps is done adjusting them individually so the global efficiency is best, or by other words, it is adjusted the speed of each pump individually in order to get the best flow\pressure\etc with the available power.

Depending on the available power from the renewable energy source, it may happen that powering a single pump will provide a better efficiency. The power hub calculates this alternative periodically or continuously or episodically such that if detected, then only one pump is operated.

In a scenario with multiple loads (e.g. multiple pumps), a suitable optimization method for deciding on how many pumps are necessary to be switch on may be used such that overall system efficiency is maximized. Alternatively, a simple heuristic may be used. Loads (e.g. pumps) are ordered by their overall efficiency. One of the pumps is determined for being switched on first. Additional pumps are then determined be switched on until. The actual efficiency of the system at the available operating conditions of the renewable energy source(s) is calculated or measured for the actual number of switched on pumps. Additional pumps are added just before calculated or measured efficiency starts to decrease. The pumps determined to be switched on can be all switched on at the same time, best if efficiency is previously calculated by the power hub, or sequentially, if efficiency is actually measured.

The total system efficiency may be preferably be defined or measured as the final system non-electrical output. For example, for a plurality of pumps or compressors the efficiency is preferably determined by maximizing the output fluid flow rate by the pumps or compressors, not by maximizing the total electrical power load consumption by the pumps or compressors. In a scenario with multiple loads and multiple applications (different pump systems), this may be treated in a similar way - each group of pumps for a specific application, or pump system, is prioritized according to usage needs. Then, within each group, the method above for maximizing efficiency is used. Based on the available renewable power source(s) available, load groups are prioritized for switching on and, for the groups that have been switched on, the number of loads is optimized based on the characteristics of the available renewable source as above described.

This power division can also be done while supplementing the renewable power source(s) with mains power in order to obtain the best efficiency point in all pumps.

Another embodiment is presented in figure 4, comprising 2 power sources - solar panels array and mains connection, 2 loads - two different pumps.

In this example the power source selection is done as in the previous embodiments.

Also when working with the renewable source the power used is defined by the maximum power available or the maximum power being needed.

The power division between the pump is similar to the previous one with the difference that the system will get a different efficiency curve for each pump.

In a scenario with multiple different loads (e.g. multiple different pumps), a suitable optimization method may be used for deciding on how many and which pumps are necessary to be switch on, such that overall system efficiency is maximized. Alternatively, a simple heuristic may be used. Loads (e.g. pumps) are ordered by their overall efficiency. The pump with the best overall efficiency is determined for being switched on first. Additional pumps are then determined by their order of overall efficiency to be additionally switched on. The actual efficiency of the system at the available operating conditions of the renewable energy source(s) is calculated or measured. Additional pumps are added until just before calculated or measured efficiency starts to decrease. The pumps determined to be switched on can be all switched at the same time, best if efficiency is previously calculated, or sequentially, if efficiency is actually measured. Another embodiment is presented in figure 5, comprising several power sources and several loads.

In a scenario with multiple different loads and multiple applications (different pump systems), this may be treated in a similar way - each group of pumps for a specific application, or pump system, is prioritized according to usage needs. Then, within each group, the method above for maximizing efficiency is used. Based on the available renewable power source(s) available, load groups are prioritized for switching on and, for the groups that have been switched on, the number of loads is optimized based on the characteristics of the available renewable source as above described.

The system can be configured using multiple power sources and loads.

The control principles applied are the same, but in this case it is possible to connect a different set of loads to each type of power source in order to get the highest efficiency on the system, e.g. in some situations .

There is also the possibility, when using a generator, the power hub also does the same efficiency tracking to obtain the best working point on the generator, also having the ability to start and stop it.

The above described embodiments are combinable.

Brief Description of the Drawings

The following figures provide preferred embodiments for illustrating the description and should not be seen as limiting the scope of invention.

Figure 1: Schematic representation of a preferred embodiment of the power hub configured to carry out a control algorithm, the power hub comprising a renewable power source connection, a mains connection, a backup power source connection, and one or more loads, each with actuator control. Figure 2: Schematic representation of a preferred embodiment of the power hub comprising 2 renewable power sources - solar panels array and mains connection, 1 load and load inertia - air compressor + air tank.

Figure 3: Schematic representation of a preferred embodiment of the power hub comprising 2 power sources - solar panels array and mains connection, 2 or more loads - two pumps of equal electrical and mechanical attributes - power, efficiency, speed, etc.

Figure 4: Schematic representation of a preferred embodiment of the power hub comprising 2 power sources - solar panels array and mains connection, 2 loads - two different pumps.

Figure 5: Schematic representation of a preferred embodiment of the power hub comprising several power sources and several loads.

Detailed description

An embodiment of the power hub is a small and low cost module with controller integrated circuit, IC, for power applications and may operate directly from the rectified universal mains input or from one of the renewable energy sources of from a backup power source. The device includes the necessary high power regulators and switches for controlling the loads and has been optimized to provide high-efficiency over the entire load range. The controller IC is preferably an IC with ultra-low power consumption when no load is present. The controller IC preferably has a start-up process able to detect the initial status and determine the load configuration according to the disclosure on power-up of the system. Instead or in addition to the high power load regulators and/or switches, the power hub may comprise load control interfaces, preferably digital, for connecting to load controllers which are then able to switch and/or regulate the load power. It is preferable to use available components, at minimum cost and with the minimum number of external components, for example using highly integrated controllers, as for example available from NXP semiconductors.

The controller IC may regulate output voltage and/or current with primary-side sensing which eliminates the need for an additional secondary feedback circuitry and simplifies the design. The controller IC may also control load power by frequency or phase control, or more generically any kind of electronic power or speed control, e.g. pulse width modulation.

Claims

C L A I M S

Method for controlling a power distribution hub for distributing electrical power from one or more renewable energy sources to one or more electrical loads supplying non-electrical outputs, said method comprising:

a. adjusting the power consumption of the electrical load or loads, and/or switching on or off individual electrical loads, such that the total efficiency in terms of non-electrical output is maximized,

b. feeding the electrical load or loads exclusively by the renewable energy source or sources, if the available power from the renewable energy source or sources is equal or higher than the required power by the one or more electrical loads for the required non-electrical outputs; or c. otherwise comprising feeding the electrical load or loads by the renewable energy source or sources in combination with one or more of: mains power, battery power, fuel generator.

Method according to claim 1 for controlling a power distribution hub for distributing electrical power from one or more renewable energy sources to one or more electrical loads supplying non-electrical load storage, said method comprising feeding the electrical load or loads exclusively by the renewable energy source or sources,

a. if the available non-electrical load storage is above a predetermined minimum threshold, or

b. if the available power from the renewable energy source or sources is higher than the required power by the one or more electrical loads to keep the non-electrical load storage from decreasing;

or otherwise comprising feeding the electrical load or loads by the renewable energy source or sources in combination with one or more of: mains power, battery power, fuel generator.

3. Method according to claim 2 further comprising when the electrical load or loads are exclusively fed by the renewable energy source or sources, adjusting the power consumption of the electrical load or loads such that it equals the available power from the renewable energy source or sources, if the available non-electrical load storage is below a predetermined maximum threshold.

4. Method according to claim 2 or 3 further comprising, when the electrical load or loads are exclusively fed by the renewable energy source or sources, and if the available non-electrical load storage is above a predetermined maximum threshold, adjusting the power consumption of the electrical load or loads such that it equals the required power by the one or more electrical loads to keep the non-electrical load storage from decreasing.

5. Method according to claims 2, 3 or 4 which comprises adjusting the power consumption of the electrical load or loads, and/or switching on or off individual electrical loads, such that the total efficiency in terms of non-electrical output is maximized.

6. Power hub device comprising data processing module configured to carry out the method of claim 1, 2, 3, 4 or 5.