Distributed photovoltaic grid-connected inverter control method and system

Abstract

The invention belongs to the field of power control, and particularly discloses a distributed photovoltaic grid-connected inverter control method and system, and the method comprises the steps: enabling a step-up transformer node m in a plurality of transformer nodes of a distributed photovoltaic access power distribution network; the method comprises the following steps: acquiring a three-phase voltage difference mode component; the three-phase voltage difference-mode component is determined based on the effective value of the three-phase voltage fundamental component and a preset reference voltage; determining transient offset power at the node m of the transformer based on the three-phase voltage difference-mode component and the three-phase voltage and the three-phase current at the node m of the transformer; updating an active power reference value of the distributed photovoltaic grid-connected inverter by referring to the transient offset power; and controlling the grid-connected inverter based on the updated active power reference value. According to the application, the system disturbance can be quickly identified, and by preferentially adjusting the output power of the grid-connected inverter, the rotation speed change of the synchronous generator is reduced, the loss cost of the system is reduced, and the stability of the system is improved.

Description

Technical Field

[0001] The present application relates to the field of power control, and more specifically, to a distributed photovoltaic grid-connected inverter control method and system. Background Art

[0002] As the global energy transition toward a high proportion of renewable energy continues, the share of photovoltaic power generation in power systems continues to grow. However, the integration of large-scale photovoltaic power into traditional power systems containing synchronous generators has led to the thorny issue of system inertia loss. This is particularly true in areas with densely populated photovoltaic power plants. The electromagnetic transient processes driven by power electronic converters and the electromechanical transient processes of synchronous generators differ significantly in temporal and spatial scales. This makes traditional control strategies based on electromechanical wave theory inadequate for the dynamic propagation characteristics of system voltage waves during faults. This not only increases the losses of large synchronous generators due to frequent changes in dispatch instructions, but also reduces stability due to frequent fluctuations in system frequency, potentially triggering new stability crises such as cascading grid disconnections.

[0003] Control theories based on the electromechanical transient characteristics of synchronous generators have long dominated power system stability analysis. While the commonly used virtual synchronous generator technology can simulate the relevant characteristics of synchronous generators, it suffers from a phase lag exceeding 150ms when responding to voltage sags. Traditional regulators of the widely used vector control system suffer from tracking errors due to bandwidth limitations when facing voltage disturbances shorter than 10ms. Furthermore, with the increasing adoption of dual power electronics in power systems, converters are central to energy conversion on both the power source and grid sides. The rapid nature of converter control makes them particularly susceptible to electromagnetic transients. Low-voltage ride-through strategies designed based on electromechanical wave theory are prone to cumulative propagation delays in power systems containing run-of-the-river small hydropower and distributed photovoltaic systems, resulting in protection action time deviations exceeding 8ms. Although some existing research has explored electromechanical disturbances and voltage wave propagation, it suffers from significant errors in precursor signal detection. Summary of the Invention

[0004] In view of the defects of the existing technology, the purpose of this application is to provide a distributed photovoltaic grid-connected inverter control method and system, aiming to solve the problems of large synchronous generator losses and low distribution network stability in the existing distribution network including distributed photovoltaic.

[0005] To achieve the above objectives, in a first aspect, the present application provides a method for controlling a distributed photovoltaic grid-connected inverter, wherein the distributed photovoltaic access power distribution network includes a transformer node among a plurality of transformer nodes. m ,include: Get transformer node m The three-phase voltage differential mode component at the position; the differential mode component is determined based on the effective value of the three-phase voltage fundamental component and a preset reference voltage; Based on the three-phase voltage differential mode component, transformer node m The three-phase voltage and three-phase current at the transformer node are determined m The transient offset power at ; Updating an active power reference value of the distributed photovoltaic grid-connected inverter with reference to the transient offset power; The grid-connected inverter is controlled based on the updated active power reference value.

[0006] In one example, the differential mode component for:

[0007] in, 、 and Respectively represent the effective values ​​of the fundamental components of the three-phase voltage; Indicates the reference voltage.

[0008] In one example, the transformer node m The transient offset power at is: ; in, and Represents transformer nodes respectively m The three-phase voltage matrix and three-phase current matrix at .

[0009] In one example, the updated active power reference value is: ; Indicates the original active power reference value, Indicates transient offset power.

[0010] In one example, the reference voltage for: ; represents a constant term, Indicates the three-phase voltage unbalance; When the three-phase load impedance angles are equal, ; When the three-phase load impedance angles are not equal:

[0011] in, 、 and Represents the effective value of the fundamental component of the three-phase voltage L Represents an intermediate variable.

[0012] In the second aspect, the present application provides a distributed photovoltaic grid-connected inverter control system, wherein the distributed photovoltaic access distribution network includes a transformer node among multiple transformer nodes. m,include: Differential mode component acquisition module, used to obtain transformer nodes m The three-phase voltage differential mode component at the position; the differential mode component is determined based on the effective value of the three-phase voltage fundamental component and a preset reference voltage; The transient offset determination module is used to determine the transient offset based on the three-phase voltage differential mode component, the transformer node m The three-phase voltage and three-phase current at the transformer node are determined m The transient offset power at ; A control module is configured to update an active power reference value of the distributed photovoltaic grid-connected inverter with reference to the transient offset power; and to control the grid-connected inverter based on the updated active power reference value.

[0013] In one example, the differential mode component acquired by the differential mode component acquisition module for: ;in, 、 and Respectively represent the effective values ​​of the fundamental components of the three-phase voltage; Indicates the reference voltage.

[0014] In one example, the transformer node determined by the transient offset determination module m The transient offset power at is: ;in, and Represents transformer nodes respectively m The three-phase voltage matrix and three-phase current matrix at .

[0015] In one example, the active power reference value updated by the control module is: ; Indicates the original active power reference value, Indicates transient offset power.

[0016] In a third aspect, the present application provides an electronic device comprising: at least one memory for storing programs; and at least one processor for executing the programs stored in the memory. When the programs stored in the memory are executed, the processor is used to execute the method described in the first aspect or any one of the examples of the first aspect.

[0017] In a fourth aspect, the present application provides a computer-readable storage medium storing a computer program. When the computer program runs on a processor, the processor executes the method described in the first aspect or any one of the examples of the first aspect.

[0018] In a fifth aspect, the present application provides a computer program product, which, when executed on a processor, enables the processor to execute the method described in the first aspect or any one of the examples of the first aspect.

[0019] In general, the above technical solutions conceived by this application have the following beneficial effects compared with the existing technologies: The present application provides a distributed photovoltaic grid-connected inverter control method and system. From a cost perspective, based on the voltage wave propagation model and the grid-connected inverter control architecture, the power compensation control strategy proposed in this application identifies system disturbances at the microsecond level and preferentially adjusts the distributed photovoltaic output power, thereby reducing the speed variation of the synchronous generator, reducing its rotor mechanical loss, reducing system loss costs, and improving system stability.

[0020] The present application provides a distributed photovoltaic grid-connected inverter control method and system, which addresses the problem of a single fault signal transmission mode and slow perception speed in power systems containing run-of-river small hydropower and distributed photovoltaics. The present application takes into account the distributed parameter characteristics of the distribution line and proposes a voltage wave propagation model, which has less computational complexity than the traditional electromechanical wave propagation. It should be noted that according to the calculation formulas for electromechanical waves at nodes and non-nodes, in order to determine the current propagation location of the electromechanical wave, it is necessary to add a time window to the voltage waveform to measure the voltage phase on the line, thereby locating the propagation of the electromechanical wave. However, the voltage differential mode component proposed in the present application only needs to measure the instantaneous value of the three-phase voltage, and does not need to add a time window to the voltage waveform to measure the voltage phase. The removal of the time window effectively reduces the time lag caused by the measurement, thereby reducing the control response time.

[0021] The present application provides a distributed photovoltaic grid-connected inverter control method and system. From the perspective of applicability of rural distribution networks, due to the poor communication capabilities in rural areas, when a system failure occurs, the relevant indication signal transmission method is single. Therefore, the power compensation control strategy proposed in this application adopts local control without communication, which is suitable for rural distribution systems with high three-phase imbalance and relatively poor communication capabilities containing distributed renewable energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the response order of each time scale in the system proposed in the embodiment of the present application; Figure 2 This is a flow chart of the distributed photovoltaic grid-connected inverter control method proposed in the embodiment of the present application; Figure 3 This is a diagram of the overall structure of the power system including a photovoltaic power plant and a synchronous machine proposed in the embodiment of the present application; Figure 4This is a control block diagram of a distributed photovoltaic grid-connected inverter proposed in an embodiment of the present application; Figure 5 This is a block diagram of the power compensation control of the grid-connected inverter proposed in the embodiment of the present application; Figure 6 This is a schematic diagram of a 10-node power system including a photovoltaic power plant proposed in an embodiment of the present application; FIG7( a ) is a diagram showing the variation of node voltage amplitudes according to an embodiment of the present application; FIG7( b ) is a diagram showing phase angle changes of nodes connected to the synchronous machine according to an embodiment of the present application; Figure 8 This is a comparison diagram of the synchronous machine speed before and after adding the power compensation control method proposed in the embodiment of the present application; Figure 9 Schematic diagram of active power output of the grid-connected inverter proposed in the embodiment of the present application; Figure 10 This is a diagram of the distributed photovoltaic grid-connected inverter control system architecture proposed in the embodiment of the present application; Figure 11 This is an architectural diagram of an electronic device proposed in an embodiment of the present application. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0024] The term "and / or" in this application describes an association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, or B exists alone. The symbol " / " in this application indicates that the associated objects are in an "or" relationship, for example, A / B means A or B.

[0025] In the embodiments of this application, words such as "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of this application should not be interpreted as being preferred or advantageous over other embodiments or designs. Rather, the use of words such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner.

[0026] In the description of the embodiments of the present application, unless otherwise specified, “multiple” means two or more than two. For example, multiple transformer nodes refer to two or more transformer nodes, etc.

[0027] The embodiments of the present application are described below in conjunction with the drawings in the embodiments of the present application.

[0028] In response to existing technical deficiencies, this application proposes a transient power control strategy for distributed photovoltaic access distribution systems that considers phase-to-phase coupling. When the system structure changes, considering phase-to-phase electromagnetic coupling and the mutual coupling of voltages at all nodes in the distribution network not only more intuitively reflects the changes in active power and reactive power at key nodes in the system and provides a reference for the formulation of control strategies, but also ensures that distributed photovoltaics can restore system stability through faster adjustment methods. First, we explain the overall fault transmission mode of the power system from the perspective of time scale. When a system fault occurs, the fault will be manifested as an event transmitted to the entire power system through the distribution line. When all power injection sources along the way will respond in time sequence according to their own response bandwidth, such as Figure 1 As shown in the figure, after a power disturbance occurs, before the various controllers of the system start to act, the disturbance power is distributed. This stage usually takes 50 microseconds. Then, when the event is transmitted to the large synchronous generator connected to the fault line, the synchronous machine responds with inertia, resulting in a change in speed, thereby causing a large-scale change in the system frequency. This stage usually takes 400 microseconds. It should be noted that the frequencies of different nodes on the same distribution line of the power system are no longer the same at this time scale. Then, as the frequency of the entire line tends to be the same, all distributed renewable energy systems on this connected line perform frequency modulation according to their own control logic. This time scale is usually between 1 second and 30 seconds according to the requirements of various national standards.

[0029] Secondary frequency regulation typically occurs on a minute-scale event scale. Because the power system's terminal locations are geographically distant from central cities and lack communication equipment, the automation equipment involved in secondary frequency regulation cannot respond to faults in the low-voltage portion of the power system, rendering the low-voltage substations transparent to the power system. If the frequency of a key node or large power injection source equipped with power information detection devices at a higher voltage level deviates from the rated system frequency within the time scale of secondary frequency regulation, the relevant synchronous generators with adjustable capacity use secondary frequency regulation to track the frequency in real time within the allowable regulation deviation to meet system frequency stability requirements. If the impact of the fault is not eliminated within the secondary frequency regulation time scale, the power system will use the dispatch system to uniformly control the adjustable elements within the system, implement tertiary frequency regulation, and issue dispatch instructions. This time scale typically operates on the hourly scale.

[0030] Figure 2 The distributed photovoltaic grid-connected inverter control method proposed in the embodiment of the present application is a flow chart; the transformer node in the multiple transformer nodes included in the distributed photovoltaic access distribution network is m .like Figure 2 As shown, the control method includes the following steps: Step S101, obtaining a three-phase voltage differential mode component; the differential mode component is determined based on the effective value of the three-phase voltage fundamental component and a preset reference voltage; Step S102, based on the three-phase voltage differential mode component, transformer node m The three-phase voltage and three-phase current at the transformer node are determined m The transient offset power at ; Step S103, updating the active power reference value of the distributed photovoltaic grid-connected inverter with reference to the transient offset power; Step S104: controlling the grid-connected inverter based on the updated active power reference value.

[0031] For details of the above steps, please refer to the relevant descriptions in the following specific embodiments.

[0032] In a specific embodiment, in order to achieve the above purpose, the present application adopts the following technical solutions: 1. Fault transmission mode based on voltage wave: The reference topology of the fault transmission mode based on voltage wave along the distribution line proposed in this application is as follows Figure 3 As shown in the figure, for a power system consisting of distributed photovoltaics and synchronous generators, such as run-of-river hydroelectric units, when the load at the end of the line suddenly goes offline, the resulting impact is a sequential change in the voltage and current on the transmission line, which in turn affects the speed of the synchronous generator and ultimately causes a change in the system frequency. All distributed photovoltaics are connected to the distribution lines via grid-connected inverters. Since the only instantaneous data that can be directly measured in the power system are the amplitudes of the three-phase voltage and current, traditional grid-connected inverter control strategies measure these parameters through a phase-locked loop (PLL) and output the frequency and phase angle of the current node, which are used as references for the internal controller. Therefore, given the inherent characteristics of the PLL, this inevitably leads to hysteresis in the grid-connected inverter control.

[0033] When the three-phase load impedance angles are equal, the three-phase voltage unbalance It can be expressed using equation (1) that when the three-phase load impedance angles are not equal, since the line voltage does not contain the zero-sequence component, the three-phase voltage unbalance degree can be obtained based on the symmetrical component method. is the line voltage unbalance rate, and its expression is shown in equation (2).

[0034] (1) (2) Since the propagation speed of voltage fluctuation on the overhead line of the distribution network is 5×10 4km / s, which is consistent with the electromagnetic time scale. The power balance at the electromagnetic time scale can be measured using the information contained in the instantaneous voltage. Therefore, this application proposes a voltage wave propagation model that takes into account the distributed parameters of the distribution line, as shown in Equation (3).

[0035] (3) in, represents the differential mode component; 、 and Respectively represent the effective values ​​of the fundamental components of the three-phase voltage; Represents the voltage reference, which is dynamically set based on the bus voltage of the fault-free operating power system.

[0036] For example, the reference voltage It can be expressed as:

[0037] in, C is a constant term. When the three-phase load impedance angles are equal, Generally, it is set to 1. When the three-phase load impedance angles are not equal Generally, it is taken as 0.6.

[0038] As can be seen from Equation (1), the voltage wave only requires the historical voltage information and the current instantaneous voltage value during stable bus operation. Compared with electromechanical waves, it propagates faster and requires less computation. Because it does not require initial phase angle detection, it can be used directly for grid-connected inverter control. In addition, the voltage wave propagation model includes a voltage reference, making this model applicable to rural distribution systems containing distributed renewable energy sources with relatively high three-phase imbalance.

[0039] The current mainstream fault transmission description method is usually the fault transmission model based on electromechanical waves mentioned above. Since this application focuses on the system transient process of the disturbance power distribution time scale, the system evolution law within this time scale can be measured by electromechanical waves. The electromechanical wave propagation characteristics of non-bus nodes can be measured using Equation (4).

[0040] (4) in, represents the difference step size, Indicates time; 、 and Respectively represent the non-busbar positions of the distribution lines The voltage phase angle, the power injected into the network and the damping constant, Represents the inertial time constant per unit length of a uniform continuum and is the angular momentum per unit length half,x represents any position of a uniform continuum, It represents the difference between the rotor speed and the synchronous speed. and Respectively represent the non-busbar positions of the distribution lines and The conductance and susceptance per unit length between and Respectively represent the non-busbar positions of the distribution lines and The conductance and susceptance per unit length between them.

[0041] The electromechanical wave propagation characteristics of the busbar node can be measured using equation (5).

[0042] (5) (6) in, Represents the inertial time constant per unit length of a uniform continuum and is the angular momentum per unit length half of Representation and busbar The number of directly connected buses, and these buses are defined as , , 、 and Respectively represent the non-busbar positions of the distribution lines The voltage phase angle, the power injected into the network and the damping constant; and Respectively represent the non-busbar positions of the distribution lines and The conductance and susceptance per unit length between the busbars are the same as the busbars, so the propagation speed of the electromechanical wave can be measured by equation (6), where: v Indicates the propagation speed of electromechanical waves; represents the impedance angle; Indicates voltage amplitude; represents the inertia constant; represents the line impedance, Indicates the voltage phase. In actual power systems, measurements show that the propagation speed of electromechanical waves is 500 km / s.

[0043] 2. Power compensation control strategy: Based on the basic principle of distributed photovoltaic grid-connected inverter, traditional control strategies such as Figure 4 As shown in the figure, based on the parameter annotations in the figure, the control of the active power output on the distributed photovoltaic grid-connected inverter side is shown in equation (7).

[0044] (7) in, Indicates the active power reference value of the distributed photovoltaic grid-connected inverter; and Respectively represent the actual voltage amplitude and DC voltage reference value of the distributed photovoltaic DC bus; Represents the PI controller of the DC bus voltage loop in distributed photovoltaic; Indicates the power consumed by the DC side load. The current mainstream control strategy uses the four steps of "calculation-phase locking-modulation-output" to regulate the active power output of distributed photovoltaics. The "phase locking" step generally generates a signal with the same frequency as the grid voltage through a phase-locked loop to achieve the grid voltage phase. The measurement of It represents the angle between the voltage d-axis and the phase reference axis. A certain time window is required in this process, so there is control hysteresis, and the degree of hysteresis depends on the length of the time window.

[0045] This lag will result in the distributed photovoltaic grid-connected inverter being unable to respond immediately when a system fault occurs. Instead, the distributed photovoltaics will only begin to adjust their own output after the speed fluctuations of the synchronous generators in the distribution line cause the frequency to change. In fact, during this time, the uncertainty of the fault and the destructive power of the fault on the system continue to increase.

[0046] In order to solve the above control lag problem, based on the voltage wave propagation model, this application designs a new power compensation control architecture based on the original control strategy of distributed photovoltaics. Its control logic is as follows: Figure 5 As shown. When a system fault occurs, the inverter can collect the current three-phase voltage and three-phase current instantaneous values ​​on the electromagnetic time scale and re-adjust the active power input reference value based on this. The power compensation controller transfer function is thus obtained as shown in Equation (8). The new controller designed in this application simplifies the control strategy of distributed photovoltaics into three steps: "calculation-modulation-output", and the phase-locked link is carried out in parallel with the above three steps, thereby achieving microsecond-level disturbance identification and compensation.

[0047] (8) in, and They represent the readjusted active power reference value and the transient offset power calculated by the voltage wave transfer model, and Representing the three-phase voltage and three-phase current matrices, respectively. Therefore, from the moment a fault occurs to the current controller, action is taken. By adjusting the current distributed photovoltaic active power output, the overall transient power flow distribution of the system is improved, resulting in smaller swing amplitudes for the synchronous generators connected to the distribution lines compared to before, reducing mechanical damage caused by large speed changes, lowering system frequency fluctuations, and improving system stability.

[0048] Figure 6 The figure represents a 10-node power system consisting of three synchronous generators and a photovoltaic cluster. The blue box contains the three synchronous generators and their associated transformers, while the green box represents the photovoltaic cluster. Distributed photovoltaic grid connection point 10 is set between nodes 4 and 6. Its grid-connected capacity is 140MW, accounting for 20% of the total system capacity. The baseline power of this model is set to 100MVA and the nominal voltage is 230kV. The network topology is as follows: Figure 6 shown. Figure 6 The three synchronous generators each include a synchronous motor and associated automatic voltage regulator, exciter, power system stabilizer, speed governor and prime mover.

[0049] Depend on Figure 6 It can be seen that when the load at node 5 fluctuates, the distances between the remaining nodes and node 5 are node 5, node 4, node 7, node 6, node 8, and node 9 from closest to farthest. Therefore, based on the partial enlarged view in Figure 7(a), it is verified that the voltage amplitude of each node changes in the above order. And based on the calculation when the voltage amplitude exceeds 30% of the maximum value, considering the acceptable error of the system simulation, the voltage wave propagation speed is about 3.3×10 4 km / s, which is of the same order of magnitude as the theoretical value.

[0050] As shown in Figure 7(b), the phase angle changes by more than 30% of the maximum value, indicating that the propagation speed of the electromechanical wave in this event is about 4.1×10 3 km / s, which is on the same order of magnitude as the theoretical value, thus proving that voltage waves can be used as a reflection of the propagation of events in the system. It is important to note that the difference in propagation speed between voltage waves and electromechanical waves is not due to differences in the speed of voltage or phase angle changes in the system, but rather to the significant difference in perceived time due to the measurement method. However, the time lag caused by this measurement method is obviously unavoidable in practice.

[0051] Figure 8The blue, red, and green lines represent the speeds (in per unit) of the three synchronous generators in the system, respectively. The solid line represents the traditional phase-locked loop (PLL)-based grid-connected inverter control strategy, while the dashed line represents the distributed photovoltaic grid-connected inverter using a power compensation control strategy. When the load capacity at node 5 suddenly decreases, the speeds of all three synchronous generators increase. Synchronous generator No. 1, closest to node 5, is affected by this event earlier than the other synchronous generators, and its response time is the same as that of node 4 shown in Figure 7(b), indicating that the electromechanical wave propagation speed and inertia response time are essentially the same. However, since the inertia time constant of synchronous generator No. 2 is H = 6.4s, which is 27% of the inertia time constant of synchronous generator No. 1, its speed changes the most.

[0052] Figure 9 The red and blue lines represent the photovoltaic power output using the traditional power control strategy and the power compensation control strategy, respectively. When the distributed photovoltaic grid-connected inverter partially adopts the power compensation control strategy proposed in this application, the voltage-wave-based power compensation control strategy proposed in this application detects load fluctuations in the system 5ms earlier than the phase-locked loop-based control strategy. Because the grid-connected inverter connected to the photovoltaic system can sense load fluctuations more quickly, it can adjust its active power output, thereby reducing the maximum speed change of the synchronous generator caused by load fluctuations.

[0053] contrast Figure 8 From the peak value of the synchronous generator speed change, it can be seen that in the above simulation experiment, the speed change of the No. 1 synchronous machine was reduced by 28.7%, the speed change of the No. 2 synchronous machine was reduced by 25.4%, and the speed change of the No. 3 synchronous machine was reduced by 24.6%. This shows that the power compensation control strategy proposed in this application can effectively reduce the speed fluctuation of the synchronous machine and the rotor loss caused by the drastic speed change by adjusting the distributed photovoltaic active power output in advance, and improve the stability of the system. It should be noted that since the distributed photovoltaic grid connection point is set at node 4, which is closest to the No. 1 synchronous machine, the speed change of the No. 1 synchronous machine is smaller than that of other synchronous machines.

[0054] In summary, the power compensation control strategy proposed in this application identifies system disturbances at the microsecond level and preferentially adjusts the output power of distributed photovoltaics, thereby reducing the speed change of the synchronous generator, reducing its rotor mechanical loss, reducing system loss costs, and improving system stability.

[0055] Figure 10 This is a diagram of the distributed photovoltaic grid-connected inverter control system architecture proposed in the embodiment of the present application; Figure 10 As shown, including: The differential mode component acquisition module 1010 is used to obtain the differential mode component of the three-phase voltage; the differential mode component is determined based on the effective value of the fundamental wave component of the three-phase voltage and a preset reference voltage; The transient offset determination module 1020 is configured to determine the transient offset of the transformer based on the three-phase voltage differential mode component and the transformer node. m The three-phase voltage and three-phase current at the transformer node are determined m The transient offset power at ; The control module 1030 is configured to update an active power reference value of the grid-connected inverter with reference to the transient offset power; and control the grid-connected inverter based on the updated active power reference value.

[0056] For example, the differential mode component acquired by the differential mode component acquisition module 1010 for: ;in, 、 and Respectively represent the effective values ​​of the fundamental components of the three-phase voltage; Indicates the reference voltage.

[0057] For example, the transformer node determined by the transient offset determination module 1020 m The transient offset power at is: ;in, and Represents transformer nodes respectively m The three-phase voltage matrix and three-phase current matrix at .

[0058] For example, the active power reference value updated by the control module 1030 is: ; Indicates the original active power reference value, Indicates transient offset power.

[0059] It should be understood that the above-mentioned system is used to execute the method in the above-mentioned embodiment. The implementation principle and technical effect of the corresponding program module in the system are similar to those described in the above-mentioned method. The working process of the system can refer to the corresponding process in the above-mentioned method and will not be repeated here.

[0060] Based on the method in the above embodiment, the embodiment of the present application provides an electronic device, such as Figure 11 As shown, the electronic device may include: a processor 1110, a communication interface 1120, a memory 1130, and a communication bus 1140, wherein the processor 1110, the communication interface 1120, and the memory 1130 communicate with each other via the communication bus 1140. The processor 1110 may call the logic instructions in the memory 1130 to execute the method in the above embodiment.

[0061] In addition, the logic instructions in the aforementioned memory 1130 can be implemented in the form of a software functional unit and, when sold or used as an independent product, can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application, or the portion that contributes to the prior art, or the portion of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes a number of instructions for enabling a computer device (which can be a personal computer, server, or network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present application.

[0062] Based on the method in the above embodiment, an embodiment of the present application provides a computer-readable storage medium, which stores a computer program. When the computer program runs on a processor, the processor executes the method in the above embodiment.

[0063] Based on the method in the above embodiment, an embodiment of the present application provides a computer program product. When the computer program product runs on a processor, the processor executes the method in the above embodiment.

[0064] It is understood that the processor in the embodiments of the present application may be a central processing unit (CPU), other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field programmable gate arrays (FPGA), other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. The general-purpose processor may be a microprocessor or any conventional processor.

[0065] The method steps in the embodiments of the present application can be implemented by hardware or by a processor executing software instructions. The software instructions can be composed of corresponding software modules, which can be stored in random access memory (RAM), flash memory, read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), registers, hard disks, mobile hard disks, CD-ROMs, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor so that the processor can read information from the storage medium and write information to the storage medium. Of course, the storage medium can also be an integral part of the processor. The processor and storage medium can be located in an ASIC.

[0066] The above embodiments can be implemented in whole or in part using software, hardware, firmware, or any combination thereof. When implemented using software, they can be implemented in whole or in part in the form of a computer program product. The computer program product comprises one or more computer instructions. When loaded and executed on a computer, the computer program instructions fully or partially produce the processes or functions described in the embodiments of this application. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted via the computer-readable storage medium. The computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium accessible by a computer or a data storage device such as a server or data center that integrates one or more available media. The available medium can be magnetic media (e.g., floppy disk, hard disk, tape), optical media (e.g., DVD), or semiconductor media (e.g., solid-state drive (SSD)).

[0067] It will be understood that the various numerical numbers involved in the embodiments of the present application are merely distinctions for the convenience of description and are not intended to limit the scope of the embodiments of the present application.

[0068] It is easy for those skilled in the art to understand that the above is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A distributed photovoltaic grid-connected inverter control method, wherein the distributed photovoltaic access distribution network includes a transformer node among multiple transformer nodes m , characterized in that, include: Obtain the three-phase voltage differential mode component; The three-phase voltage differential mode component is determined based on the effective value of the three-phase voltage fundamental component and a preset reference voltage; Based on the three-phase voltage differential mode component, transformer node m The three-phase voltage and three-phase current at the transformer node are determined m The transient offset power at ; Updating an active power reference value of the distributed photovoltaic grid-connected inverter with reference to the transient offset power; The distributed photovoltaic grid-connected inverter is controlled based on the updated active power reference value.

2. The method according to claim 1, characterized in that The three-phase voltage differential mode component for: in, 、 and Respectively represent the effective values ​​of the fundamental components of the three-phase voltage; Indicates the reference voltage.

3. The method according to claim 1, characterized in that Transformer Node m The transient offset power at is: ; in, and Represents transformer nodes m The three-phase voltage matrix and three-phase current matrix at Represents the differential mode component of the three-phase voltage.

4. The method according to claim 1, wherein The updated active power reference value is: ; Indicates the original active power reference value, Indicates transient offset power.

5. The method according to claim 1 or 2, characterized in that Reference voltage for: ; represents a constant term, Indicates the three-phase voltage unbalance; When the three-phase load impedance angles are equal, ; When the three-phase load impedance angles are not equal: in, 、 and Respectively represent the effective values ​​of the fundamental components of the three-phase voltage; L Represents an intermediate variable.

6. A distributed photovoltaic grid-connected inverter control system, wherein the distributed photovoltaic access distribution network includes a transformer node among multiple transformer nodes m , characterized in that, include: A differential mode component acquisition module is used to obtain the three-phase voltage differential mode components; The three-phase voltage differential mode component is determined based on the effective value of the three-phase voltage fundamental component and a preset reference voltage; The transient offset determination module is used to determine the transient offset based on the three-phase voltage differential mode component, the transformer node m The three-phase voltage and three-phase current at the transformer node are determined m The transient offset power at ; A control module, configured to update an active power reference value of a distributed photovoltaic grid-connected inverter with reference to the transient offset power; and controlling the grid-connected inverter based on the updated active power reference value.

7. The system according to claim 6, characterized in that The three-phase voltage differential mode components acquired by the differential mode component acquisition module for: ;in, 、 and Respectively represent the effective values ​​of the fundamental components of the three-phase voltage; Indicates the reference voltage.

8. The system according to claim 6, wherein: The transformer node determined by the transient offset determination module m The transient offset power at is: ;in, and Represents transformer nodes m The three-phase voltage matrix and three-phase current matrix at Represents the differential mode component of the three-phase voltage.

9. The system according to claim 6, wherein: The active power reference value updated by the control module is: ; Indicates the original active power reference value, Indicates transient offset power.

10. An electronic device, characterized in that: include: at least one memory for storing a computer program; At least one processor is used to execute the program stored in the memory. When the program stored in the memory is executed, the processor is used to execute the method according to any one of claims 1 to 5.

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