Distributed new energy electric energy quality treatment system and method

Abstract

The invention discloses a distributed new energy electric energy quality treatment system and method, relates to the field of new energy, and is used for realizing electric energy quality collaborative treatment of integrally outputting alternating current by a large-scale grid-connected distributed micro inverter. According to the invention, the distributed power generation units are connected with the control center through the Internet of Things communication module, the control center issues frequency and phase synchronization signals to each micro inverter unit in a broadcast mode, and in addition, the control center carries out power quality management according to a power quality management target and the topology and historical power quality indexes of each distributed power generation unit. And dynamically formulating an electric energy quality adjustment strategy of each micro-inverter unit according to the electric energy quality index detected at the public access point of the power grid and distributing the electric energy quality adjustment strategy to the corresponding micro-inverter unit until a treatment target is achieved. According to the invention, phase synchronization and electric energy quality cooperative treatment of large-scale and large-range distributed power generation units are realized, the specific adjustment process is locally executed in parallel in the micro-inverter unit, and the treatment efficiency is high.

Description

Technical Field

[0001] The present invention relates to the field of new energy, and in particular to a distributed new energy power quality management system and a distributed new energy power quality management method. Background Art

[0002] Photovoltaic panels / wind turbines and other new energy power generation modules usually generate direct current, which needs to be converted into alternating current through an inverter before it can be connected to the grid. Power quality indicators such as voltage, current, phase, active power, reactive power and harmonic components of alternating current are of great significance to the inverter output of the grid-connected inverter and the power quality indicators of the power grid. Poor inverter output power quality will seriously affect the operation of the power grid, increase grid consumption and may cause interruption of jumpers of other loads, other inverters, transformers and other devices connected to the grid. Therefore, through strategic management of the inverter output power quality, the optimization of the power quality of the power grid can be directly achieved.

[0003] Traditional centralized inverters and string inverters usually need to be connected to a special device that provides power quality management after connecting to a box transformer, switch station or booster station of multiple inverters to improve the power quality indicators related to AC power, such as the practical-scale power system for high-voltage energy collection and conversion of recyclable energy disclosed in CN103688436A and the visual monitoring and control system for the system. This solution has high construction costs, large equipment, and high site requirements. In another way, large-scale grid-connected micro-inverters usually have low output voltage and low power, and are usually connected in parallel to the low-voltage user power grid, or a large number of micro-inverters are connected in parallel to the AC bus in a centralized photovoltaic power station system, and then connected to box transformers, switch stations, booster stations and other equipment to manage the power quality of these devices. However, the power quality of the AC power output by a single micro-inverter is not consistent with the power quality of the AC power output after large-scale grid connection. Centralized power quality management cannot guarantee the synchronization between the micro-inverters, and the power quality on the AC bus will be greatly reduced. In addition, due to the large number of micro-inverters connected to the grid, it is easy to cause broadband oscillation of the power grid, AC circulating current, or overheating and burning of the transformer.

[0004] Centralized inverters, string inverters, and microinverters can use digitally controlled power electronics methods to control the inverter circuit using digital switches of power electronics to manage the output AC power quality indicators. However, when the number of microinverters participating in collaborative management in a power plant increases to a certain level (for example, more than 10, 100, or even 1,000), with the current centralized power quality management solution, a large number of control objects require a large amount of communication resources. The more control objects there are, the greater the delay, and the power quality management effect is difficult to guarantee. Summary of the invention

[0005] The purpose of the present invention is to provide a distributed renewable energy power quality management system and method to address the above-mentioned problems, so as to achieve coordinated management of the power quality of the overall output AC power of distributed micro-inverters connected to the grid on a large scale.

[0006] The technical solution adopted by the present invention is as follows:

[0007] A distributed new energy power quality management system includes a plurality of distributed new energy power generation modules; characterized in that each new energy power generation module is connected to a distributed energy storage unit and a micro-inverter unit, and the distributed energy storage unit and the micro-inverter unit are connected to each other; the micro-inverter unit of each new energy power generation module is connected to a control center via an Internet of Things communication unit; the low-voltage alternating current output by each micro-inverter unit is connected to the public access point of the power grid;

[0008] The control center is configured to: synchronously send low-voltage AC output frequency and phase synchronization signals to each micro-inverter unit; and, according to the power quality management target, based on the power quality indicators detected at the public access point of the power grid and the power quality indicators reported historically by each micro-inverter unit, dynamically formulate the power quality adjustment strategy of each micro-inverter unit and distribute it to the corresponding micro-inverter unit until the power quality indicators at the public access point of the power grid reach the power quality management target;

[0009] The micro-inverter is configured to: synchronize the frequency and phase of the low-voltage AC power output by the inverter according to the received synchronization signal; and adjust the power quality index of the low-voltage AC power output by its own inverter according to the received power quality adjustment strategy.

[0010] Furthermore, the power quality index includes at least one of voltage, current, frequency, phase, active power, reactive power and harmonic components.

[0011] Furthermore, the control center sends the synchronization signal to each micro-inverter unit by broadcasting.

[0012] Furthermore, the synchronization signal is an analog signal, which is obtained by modulating a frequency-modulated and phase-modulated sine wave for synchronization on a predetermined carrier signal.

[0013] Alternatively, the synchronization signal is a digital signal, which is obtained by transmitting a digital phase reference using the timing information used for synchronization as a reference on a predetermined digital signal.

[0014] Furthermore, the power quality regulation strategies formulated by the control center for each micro-inverter unit are not all the same or are completely different.

[0015] Furthermore, the control center sends the power quality regulation strategy by unicast, groupcast or multicast.

[0016] Furthermore, the power quality management target is given by the upper-level power grid regulation instructions received by the control center.

[0017] Furthermore, the micro-inverter unit uses the electric energy stored in the connected distributed energy storage unit and / or the electric energy output by the connected new energy power generation module to adjust the power quality index of the low-voltage alternating current output by its own inverter.

[0018] The present invention also provides a distributed renewable energy power quality management method, which is performed based on the above-mentioned distributed renewable energy power quality management system, and the method includes:

[0019] The control center sends synchronization signals of low-voltage AC output frequency and phase to each micro-inverter unit;

[0020] Each micro-inverter unit synchronizes the frequency and phase of the low-voltage alternating current output by the inverter according to the received synchronization signal;

[0021] The following process is executed cyclically until the power quality index at the public access point of the power grid reaches the power quality management target:

[0022] The control center obtains the power quality management target, formulates the power quality adjustment strategy of each micro-inverter unit and distributes it to the corresponding micro-inverter unit based on the current power quality indicators detected at the public access point of the power grid and the power quality indicators reported by each micro-inverter unit in history;

[0023] The micro-inverter unit that receives the power quality regulation strategy adjusts the power quality index of the low-voltage alternating current output by its own inverter according to the received power quality regulation strategy.

[0024] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0025] 1. The distributed renewable energy power quality management solution of the present invention can realize efficient synchronization of the frequency and phase of a large number of micro-inverter units through distributed Internet of Things communication units. Moreover, based on the distributed Internet of Things communication units, it is possible to realize power quality management of each micro-inverter unit separately, so as to utilize the power generation capacity of different renewable energy power generation modules as efficiently as possible, and then realize the coordinated management of the power quality of AC output by multiple micro-inverters distributed on a large scale and over a large range.

[0026] 2. The distributed renewable energy power quality management solution of the present invention reduces or even omits the dedicated high-power power quality management equipment in centralized power management, thereby reducing the cost of power generation, grid connection and network construction of renewable energy power generation modules.

[0027] 3. The distributed new energy power quality management solution of the present invention only generates a power quality adjustment strategy in the control center, and the specific real-time adjustment is performed simultaneously locally by the micro-inverter unit. The collaborative management of power quality is efficient, the computing load of the control center is low, and the power quality adjustment strategy can be updated more efficiently, thereby improving the closed-loop control efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention will now be described by way of example with reference to the accompanying drawings, in which:

[0029] Figure 1 It is a structural diagram of a distributed renewable energy power quality management system in one embodiment.

[0030] Figure 2 is a structural diagram of a distributed power generation unit in one embodiment.

[0031] Figure 3 is a structural diagram of a micro-inverter in one embodiment.

[0032] In the figure, 200 is an Internet of Things communication unit, 201 is a new energy power generation module, 202 is a power optimizer, 203 is a distributed energy storage unit, 204 is a micro-inverter unit, 300 is a distributed power generation unit, 301 is a control center, 302 is a transformer, 303 is a power quality controller / power regulation device, 304 is an inverter unit, 305 is a storage module, 306 is a micro-inverter controller, and 307 is a power quality measurement module. DETAILED DESCRIPTION

[0033] All features disclosed in this specification, or steps in all methods or processes disclosed, except mutually exclusive features and / or steps, can be combined in any manner.

[0034] Any feature disclosed in this specification (including any additional claims and abstract), unless otherwise stated, may be replaced by other equivalent or alternative features having similar purposes. That is, unless otherwise stated, each feature is only an example of a series of equivalent or similar features.

[0035] Example 1

[0036] The distributed renewable energy power quality management system is aimed at the power generation scenario of distributed power generation units. A power plant / power station includes a large number of distributed power generation units 300, such as Figure 2As shown, each distributed power generation unit 300 includes a new energy power generation module 201, and the new energy power generation module 201 includes at least one new energy power generation unit, the so-called new energy power generation unit, that is, the smallest power generation unit such as a photovoltaic panel, a wind turbine, etc. Each distributed power generation unit 300 is also configured with a distributed energy storage unit 203 and a micro-inverter unit 204. The new energy power generation module 201 is connected to the distributed energy storage unit 203 and the micro-inverter unit 204 respectively, and the micro-inverter unit 204 and the distributed energy storage unit 203 are connected to each other. The low-voltage alternating current output by each micro-inverter unit 204 is connected to the public access point of the power grid, for example Figure 1 The transformer 302 in the transformer 302. The direct current generated by each new energy power generation module 201 is inverted and converted into alternating current by the corresponding micro-inverter unit 204, and then connected to the grid and output to the load or the grid through the transformer 302, wherein the excess generated electric energy is transmitted to the distributed energy storage unit 203 for storage; when the electric energy generated by the new energy power generation module 201 is insufficient to support the load or the grid, the distributed energy storage unit 203 supplements the electric energy. In addition, due to the design of the distributed energy storage unit 203, when the micro-inverter unit 204 implements the adjustment of the power quality index of the low-voltage alternating current output by the inverter, if the electric energy provided by the new energy power generation module 201 is insufficient, the distributed energy storage unit 203 can also be used to supply power, or assist the new energy power generation module 201 in supplying power.

[0037] In addition, each distributed power generation unit 300 is usually also equipped with a power optimizer 202 (such as an MPPT controller), which is connected to the new energy power generation module 201 to output the electric energy generated by the new energy power generation module 201 at the highest power.

[0038] like Figure 3 The structure diagram of the micro-inverter unit 204 is shown. It includes a micro-inverter controller 306, a power quality measurement module 307, a storage module 305, and an inverter unit 304 controlled by the micro-inverter controller 306. The micro-inverter controller 306 is connected to the storage module 305, the inverter unit 304 and the power quality measurement module 307 respectively. The inverter unit 304 is responsible for inverting the direct current output by the new energy generation module 201 or the power optimizer 202 (if any) into alternating current; the storage module 305 is used to store the power quality regulation strategy and synchronization signal received by the Internet of Things communication unit 200, and the power quality indicators (such as voltage, current, frequency, phase, active power, reactive power and harmonic components) measured by the power quality control module 307; the power quality measurement module 307 is responsible for measuring the power quality indicators of the low-voltage alternating current output by the inverter. As mentioned in the background technology section, the micro-inverter controller 306 uses digital switches of power electronics to control the inverter circuit and adjust the power quality index of the output AC power.

[0039] Each distributed power generation unit 300 is equipped with an Internet of Things communication unit 200, which is connected to the control center 300 and serves as a bridge for communication between each distributed power generation unit 300 and the control center 301. The Internet of Things communication unit 200 is connected to one or more of the new energy generation module 201, the power optimizer 202, the distributed energy storage unit 203 and the micro-inverter unit 204, but at least the micro-inverter unit 204 must be connected. Figure 2 In the illustrated embodiment, the IoT communication unit 200 is respectively connected to the new energy power generation module 201 , the power optimizer 202 , the distributed energy storage unit 203 and the micro-inverter unit 204 .

[0040] At the transformer 302, a power quality detection device (not shown) on the grid side is configured, which is used to measure the power quality index at the public access point of the grid in real time and transmit it to the control center 301. In addition, Figure 1 As shown, a power quality controller / power regulation device 303 is also provided after the transformer 302. The power quality controller / power regulation device 303 is connected to the control center 301, and under the control of the control center 301, the power quality index of the AC power input from the transformer 302 to the power grid is adjusted.

[0041] The control center 301 is responsible for synchronizing the frequency and phase of the low-voltage AC power output by each micro-inverter unit 204, and is implemented by synchronously sending a synchronization signal of the low-voltage AC power output frequency and phase to each micro-inverter unit 204. The synchronization signal can be a predetermined timing information (timing error is less than 1ms), or one or more phase synchronization signals (50Hz or 60Hz power frequency). The synchronization signal may jump according to the upper-level power grid regulation instruction.

[0042] The synchronization signal can be one of two forms:

[0043] 1) Analog signal: The analog signal is obtained by modulating a sine wave for frequency modulation, phase modulation (or amplitude modulation) on a certain set carrier signal.

[0044] 2) Digital signal: The digital signal is obtained by periodically / non-periodically transmitting a digital phase reference on a predetermined digital signal. The digital phase reference uses the timing information used for synchronization as a reference. In addition, the digital phase reference can also be spread spectrum, frequency modulated, encrypted, etc. in a digital manner to prevent external attacks.

[0045] In addition, the control center 301 is also responsible for dynamically formulating the power quality adjustment strategy of each micro-inverter unit and distributing it to the corresponding micro-inverter unit 204 according to the power quality management target, based on the power quality indicators detected at the public access point of the power grid and the power quality indicators reported historically by each micro-inverter unit 204, until the power quality indicators at the public access point of the power grid reach the power quality management target. It should be noted that the power quality adjustment strategy issued is not a conditional instruction that needs to be executed in real time, but serves as reference information for adjusting the power quality indicators. It should be noted that the specific method for the control center 301 to formulate the power quality adjustment strategy varies according to different usage scenarios, and is a design that is configured according to actual needs. The present invention only proposes the concept of distributed collaborative management, and does not limit how to formulate the power quality adjustment strategy or what kind of power quality adjustment strategy to formulate.

[0046] The power quality management target based on the control center 301 can be a pre-set target, but it is usually given by the upper power grid regulation instruction issued by the upper computer to the control center 301. And the upper power grid regulation instruction may also be adjusted dynamically. Correspondingly, when the power quality management target changes, the power quality regulation strategy formulated by the control center 301 also needs to be adjusted synchronously.

[0047] Since each micro-inverter unit 204 has different topological structures, different environments, different power generation, and different electric energy stored in the distributed energy storage unit 203, the electric energy that can be contributed is also different. In order to support longer-term power quality adjustment capabilities and meet the power quality requirements at the public access point of the power grid, the control center 301 formulates different or completely different power quality adjustment strategies for each micro-inverter unit 204, and coordinates and manages the electric energy of each distributed power generation unit 300 as efficiently as possible through personalized management methods.

[0048] The so-called dynamic formulation of power quality regulation strategy is to formulate a set of power quality regulation strategies based on the power quality indicators detected at a certain moment. After being sent to the corresponding micro-inverter unit 204 for execution, at subsequent moments, the power quality indicators at the public access point of the power grid will change. At this time, it is necessary to formulate a new set of power quality regulation strategies based on the power quality indicators detected at subsequent moments, and this cycle is repeated until the power quality management goal is achieved.

[0049] The micro-inverter unit 204 synchronizes the frequency and phase of the low-voltage AC power output by the inverter according to the received synchronization signal, and adjusts the power quality index of the low-voltage AC power output by the inverter according to the received power quality adjustment strategy.

[0050] Specifically, according to the received power quality regulation strategy, the micro-inverter unit 204 controls the inverter circuit through the micro-inverter controller 306 using the digital switch of the power electronics to regulate the voltage, current, phase, active power, reactive power and harmonic components of the AC power output by the inverter unit 304.

[0051] Since in this embodiment, a large number of distributed power generation units 300 communicate with the control center 301 through the Internet of Things communication unit 200 respectively, the control center 301 can communicate with the target distributed power generation unit 300 in the form of broadcast, unicast, groupcast or multicast.

[0052] For example, the synchronization signal needs to be received and executed by each micro-inverter unit 204, so the control center 301 can send the synchronization signal to each micro-inverter unit 204 via broadcast, and load the synchronization information of frequency and phase (or amplitude) in the broadcast signal, and send it to each micro-inverter unit 204 synchronously via broadcast.

[0053] As the power quality regulation strategies of different micro-inverter units 204 are different, the control center 301 sends the power quality regulation strategy to the corresponding micro-inverter unit 204 through unicast, groupcast or multicast. In terms of specific implementation, by configuring a device ID for each micro-inverter unit 204 and adding the device ID of the target micro-inverter unit 204 to each sent power quality regulation strategy, only the target micro-inverter unit 204 with the corresponding device ID receives and parses the power quality regulation strategy for storage.

[0054] Example 2

[0055] Based on the system in Example 1, this embodiment proposes a distributed renewable energy power quality management method, which includes:

[0056] The control center 301 sends synchronization signals of low voltage AC output frequency and phase to each micro-inverter unit 204 respectively;

[0057] Each micro-inverter unit 204 synchronizes the frequency and phase of the low-voltage AC power output by the inverter according to the received synchronization signal;

[0058] The following process is executed cyclically until the power quality index at the public access point of the power grid reaches the power quality management target:

[0059] The control center 301 obtains the power quality management target (the target is usually given by the upper-level power grid regulation instruction and may change, and each change requires re-management), and formulates the power quality regulation strategy of each micro-inverter unit 204 according to the current power quality index detected at the public access point of the power grid and the power quality index reported by each micro-inverter unit 204 in history (the topology of the corresponding distributed generation unit 300 has been taken into account) and distributes it to the corresponding micro-inverter unit 204;

[0060] The micro-inverter unit 204 that receives the power quality regulation strategy adjusts the power quality index of the low-voltage alternating current output by its own inverter according to the received power quality regulation strategy.

[0061] The above embodiment does not limit the number of distributed generation units 300 arranged in the power plant / power station. In fact, each control center 301 of the above system supports power quality management of more than 100 distributed generation units 300 with a distribution diameter exceeding 100 meters.

[0062] The present invention is not limited to the above-mentioned specific embodiments, but extends to any new features or any new combination disclosed in this specification, as well as any new method or process steps or any new combination disclosed.

Claims

1. A distributed renewable energy power quality management system, comprising a plurality of distributed renewable energy power generation modules; It is characterized in that Each new energy power generation module is connected to a distributed energy storage unit and a micro-inverter unit, and the distributed energy storage unit and the micro-inverter unit are connected to each other; the micro-inverter unit of each new energy power generation module is connected to the control center via an Internet of Things communication unit; the low-voltage alternating current output by each micro-inverter unit is connected to the public access point of the power grid; The control center is configured to: synchronously send low-voltage AC output frequency and phase synchronization signals to each micro-inverter unit; and, according to the power quality management target, based on the power quality indicators detected at the public access point of the power grid and the power quality indicators reported historically by each micro-inverter unit, dynamically formulate the power quality adjustment strategy of each micro-inverter unit and distribute it to the corresponding micro-inverter unit until the power quality indicators at the public access point of the power grid reach the power quality management target; The micro-inverter is configured to: synchronize the frequency and phase of the low-voltage AC power output by the inverter according to the received synchronization signal; and adjust the power quality index of the low-voltage AC power output by its own inverter according to the received power quality adjustment strategy.

2. The distributed renewable energy power quality management system according to claim 1, It is characterized in that The power quality index includes at least one of voltage, current, frequency, phase, active power, reactive power and harmonic components.

3. The distributed renewable energy power quality management system according to claim 1, It is characterized in that The control center sends the synchronization signal to each micro-inverter unit by broadcasting.

4. The distributed renewable energy power quality management system according to claim 1, It is characterized in that The synchronization signal is an analog signal, which is obtained by modulating a frequency-modulated and phase-modulated sine wave for synchronization on a predetermined carrier signal.

5. The distributed renewable energy power quality management system according to claim 1, It is characterized in that The synchronization signal is a digital signal, which is obtained by transmitting a digital phase reference using the timing information for synchronization as a reference on a predetermined digital signal.

6. The distributed renewable energy power quality management system according to claim 1, It is characterized in that The power quality regulation strategies formulated by the control center for each micro-inverter unit are not all the same or are completely different.

7. The distributed renewable energy power quality management system according to claim 6, It is characterized in that The control center sends the power quality regulation strategy through unicast, groupcast or multicast.

8. The distributed renewable energy power quality management system according to claim 1, It is characterized in that The power quality management target is given by the upper-level power grid regulation instructions received by the control center.

9. The distributed renewable energy power quality management system according to claim 1, It is characterized in that The micro-inverter unit uses the electric energy stored in the connected distributed energy storage unit and / or the electric energy output by the connected new energy power generation module to adjust the power quality index of the low-voltage alternating current output by its own inverter.

10. A distributed renewable energy power quality management method based on the distributed renewable energy power quality management system according to any one of claims 1 to 9, It is characterized in that include: The control center sends synchronization signals of low-voltage AC output frequency and phase to each micro-inverter unit; Each micro-inverter unit synchronizes the frequency and phase of the low-voltage alternating current output by the inverter according to the received synchronization signal; The following process is executed cyclically until the power quality index at the public access point of the power grid reaches the power quality management target: The control center obtains the power quality management target, formulates the power quality adjustment strategy of each micro-inverter unit and distributes it to the corresponding micro-inverter unit based on the current power quality indicators detected at the public access point of the power grid and the power quality indicators reported by each micro-inverter unit in history; The micro-inverter unit that receives the power quality regulation strategy adjusts the power quality index of the low-voltage alternating current output by its own inverter according to the received power quality regulation strategy.

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