Electromagnetic transient modeling method and system for distributed photovoltaic inverter wave sealing strategy

Abstract

The invention provides an electromagnetic transient modeling method and system for a wave sealing strategy of a distributed photovoltaic inverter, and the method comprises the steps: obtaining a current and voltage reference value of the distributed photovoltaic inverter outside a wave sealing state based on the power data and current data of the distributed photovoltaic inverter; setting a dq-axis current reference value to be zero, and setting a virtual resistor in the electromagnetic transient model, so that the simulation current is reduced, and a wave sealing state is simulated; based on the three-phase voltage of the virtual resistor, calculating a three-phase modulation voltage reference value in a wave sealing state, and completing electromagnetic transient modeling; according to the method and the system, the simulation current is reduced by introducing the virtual resistor, so that the wave sealing characteristic of the inverter is simulated, the electromagnetic transient model of the distributed photovoltaic inverter wave sealing strategy can be constructed without depending on a detailed topological structure and an actual wave sealing strategy and establishing a detailed switch model, and the method and the system have the advantages of being simple in structure and convenient to operate. Therefore, a large simulation step length can be adopted, the simulation scale and the simulation speed are improved, and the electromagnetic transient simulation requirement of a large power grid is met.

Description

Technical Field

[0001] The present invention belongs to the fields of new energy power generation technology and power system technology, and particularly relates to an electromagnetic transient modeling method and system for a distributed photovoltaic inverter wave blocking strategy. Background Art

[0002] Distributed photovoltaic power generation has experienced rapid growth in recent years, with new installations exceeding those of centralized photovoltaic systems. Distributed photovoltaic capacity has become one of the primary power sources for the power grid. Unlike centralized photovoltaic inverters, many distributed photovoltaic inverters generally do not include low- and high-voltage ride-through modes. When a short circuit occurs in the power grid, the grid voltage drops momentarily, potentially causing overcurrent in the inverter. Limited by the capacity of the inverter's switching transistors, the inverter's overcurrent capability is relatively weak, typically with a maximum overcurrent capability of 1.1 to 1.3 times the rated current. To prevent permanent damage to the equipment due to overcurrent, the inverter adjusts the sequence of high-frequency switching pulses to implement wave blocking control, rapidly reducing the output current to zero.

[0003] When inverters are in a power-off state, they do not output active or reactive power, significantly impacting the power grid. In areas with high penetrations of distributed photovoltaics, power-off characteristics have a significant impact on the grid. Accurately modeling the power-off characteristics of distributed photovoltaics is essential for analyzing grid transient stability.

[0004] Because the actual blocking strategy is closely related to the inverter topology, existing technologies require precise adjustment of the sequence of high-frequency switching pulses. Directly adopting the actual blocking strategy in the model would limit the simulation step size and increase the amount of computational data. Furthermore, because different manufacturers use different blocking strategies, establishing separate simulation models for different models would complicate the modeling process. Therefore, achieving universal modeling is a pressing issue. Summary of the Invention

[0005] To overcome the above-mentioned deficiencies of the prior art, the present invention proposes an electromagnetic transient modeling method for a distributed photovoltaic inverter wave blocking strategy, comprising:

[0006] Based on the power data and current data of the distributed photovoltaic inverter, obtaining the current and voltage reference values ​​of the distributed photovoltaic inverter outside the closed wave state;

[0007] Setting the dq axis current reference value of the distributed photovoltaic inverter to zero, and setting a virtual resistance in the electromagnetic transient model to reduce the simulated current of the distributed photovoltaic inverter to simulate a closed wave state;

[0008] Determine the three-phase voltage of the virtual resistor based on the current data, and obtain the three-phase modulation voltage reference value in the closed-wave state using a preset closed-wave voltage reference value calculation formula based on the three-phase voltage of the virtual resistor;

[0009] Based on the current and voltage reference values ​​outside the wave-enclosed state and the three-phase modulation voltage reference values ​​in the wave-enclosed state, electromagnetic transient modeling is completed.

[0010] Preferably, the setting of a virtual resistor in the electromagnetic transient model to reduce the simulated current of the distributed photovoltaic inverter and simulate the blocked wave state includes:

[0011] Based on the simulated current waveform in the current data, a virtual resistance is set in the electromagnetic transient model so that the simulated current drops to zero and converges within a set time, simulating a wave-enclosing state.

[0012] Preferably, the three-phase voltage of the virtual resistor is determined based on the current data, and a preset wave-blocking voltage reference value calculation formula is used based on the three-phase voltage of the virtual resistor to obtain a three-phase modulation voltage reference value in a wave-blocking state, including:

[0013] Determine the three-phase voltage of the virtual resistor based on the current data, and substitute the three-phase voltage of the virtual resistor into a preset wave-enclosing voltage reference value calculation formula;

[0014] Based on the closed-wave voltage reference value calculation formula, the three-phase voltage difference between the three-phase terminal voltage of the distributed photovoltaic inverter and the three-phase voltage of the virtual resistor is calculated, and after coefficient conversion is performed on the three-phase voltage difference, the three-phase modulation voltage reference value under the closed-wave state is obtained.

[0015] Preferably, the calculation formula of the sealing wave voltage reference value is expressed as:

[0016]

[0017] Among them, u abcref2 is the three-phase modulation voltage reference value in the blocked state, u termabc is the three-phase terminal voltage of the distributed photovoltaic inverter, i abc is the three-phase current of the distributed photovoltaic inverter, R V is the virtual resistance, i abc R V is the three-phase voltage of the virtual resistor, K PWM is the pulse width modulation gain coefficient.

[0018] Preferably, the power data and current data of the distributed photovoltaic inverter are based on the power and current dual-loop control principle to obtain the current and voltage reference values ​​of the distributed photovoltaic inverter outside the closed-wave state, including:

[0019] Obtain power and current data of distributed photovoltaic inverters;

[0020] Determining an operating state of the distributed photovoltaic inverter based on the power data and the current data; the operating state includes a normal operating state, a blocking state, and a power recovery state;

[0021] Based on the power data under the normal operating state, using a power controller, obtaining a dq axis current reference value under the normal operating state;

[0022] Based on the dq axis current reference value and the current data in the normal operating state, using a current controller, obtaining a three-phase modulation voltage reference value in the normal operating state;

[0023] Based on the dq axis current reference values ​​at the normal operating state before the power recovery state begins, using a set slope, obtain the dq axis current reference values ​​at each moment in the power recovery state;

[0024] Based on the current data in the power recovery state and the dq-axis current reference values ​​at each moment, a current controller is used to obtain the three-phase modulation voltage reference values ​​at each moment in the power recovery state.

[0025] Preferably, obtaining the dq axis current reference values ​​under the normal operating state by using a power controller based on the power data under the normal operating state includes:

[0026] Based on the power data under the normal operating state, obtaining a power deviation of the distributed photovoltaic inverter under the normal operating state;

[0027] After the power deviation passes through the power controller, the dq axis current reference value under the normal operating state is obtained.

[0028] Preferably, the obtaining of the three-phase modulation voltage reference value under the normal operating state by using a current controller based on the dq axis current reference value under the normal operating state and the current data includes:

[0029] Based on the current data, obtaining the dq axis current of the distributed photovoltaic inverter in the normal operating state;

[0030] Calculating the difference between the dq axis current reference value and the dq axis current in the normal operating state to obtain the dq axis current deviation;

[0031] The dq axis current deviation is subjected to a reverse Peek transformation by a current controller to obtain a three-phase modulation voltage reference value under the normal operating state.

[0032] Preferably, the dq axis current reference values ​​at each moment in the power recovery state are obtained based on the dq axis current reference values ​​at the normal operating state before the power recovery state starts, using a set slope, including:

[0033] The dq axis current reference value in the power recovery state starts from 0 and gradually recovers to the dq axis current reference value in the normal operation state before the wave blocking state begins according to the set slope, and obtains the dq axis current reference value at each moment in the power recovery state.

[0034] Preferably, the obtaining of the three-phase modulation voltage reference value at each moment in the power recovery state by using a current controller based on the current data in the power recovery state and the dq-axis current reference value at each moment includes:

[0035] Based on the current data in the power recovery state, obtaining the dq-axis current of the distributed photovoltaic inverter at each moment in the power recovery state;

[0036] Based on each of the moments in the power recovery state, calculating a difference between a dq axis current reference value at the moment and the dq axis current at the moment to obtain a moment current deviation;

[0037] The current deviation at the moment is subjected to a reverse Peek transformation by a current controller to obtain a three-phase modulation voltage reference value at the moment.

[0038] Based on the same inventive concept, the present invention also provides an electromagnetic transient modeling system for a distributed photovoltaic inverter wave blocking strategy, comprising:

[0039] A first parameter determination module is configured to obtain current and voltage reference values ​​of the distributed photovoltaic inverter outside a closed-wave state based on power data and current data of the distributed photovoltaic inverter;

[0040] A wave blocking simulation module is used to set the dq axis current reference value of the distributed photovoltaic inverter to zero and set a virtual resistance in the electromagnetic transient model to reduce the simulated current of the distributed photovoltaic inverter to simulate the wave blocking state;

[0041] a second parameter determination module, configured to determine the three-phase voltage of the virtual resistor based on the current data, and obtain a three-phase modulation voltage reference value in a wave-sealed state using a preset wave-sealed voltage reference value calculation formula based on the three-phase voltage of the virtual resistor;

[0042] Based on the current and voltage reference values ​​outside the wave-enclosed state and the three-phase modulation voltage reference values ​​in the wave-enclosed state, electromagnetic transient modeling is completed.

[0043] Preferably, the wave envelope simulation module is specifically used to:

[0044] Based on the simulated current waveform in the current data, a virtual resistance is set in the electromagnetic transient model so that the simulated current drops to zero and converges within a set time, simulating a wave-enclosing state.

[0045] Preferably, the second parameter determination module is specifically used to:

[0046] Determine the three-phase voltage of the virtual resistor based on the current data, and substitute the three-phase voltage of the virtual resistor into a preset wave-enclosing voltage reference value calculation formula;

[0047] Based on the closed-wave voltage reference value calculation formula, the three-phase voltage difference between the three-phase terminal voltage of the distributed photovoltaic inverter and the three-phase voltage of the virtual resistor is calculated, and after coefficient conversion is performed on the three-phase voltage difference, the three-phase modulation voltage reference value under the closed-wave state is obtained.

[0048] Preferably, the calculation formula of the sealing wave voltage reference value is expressed as:

[0049]

[0050] Among them, u abcref2 is the three-phase modulation voltage reference value in the blocked state, u termabc is the three-phase terminal voltage of the distributed photovoltaic inverter, i abc is the three-phase current of the distributed photovoltaic inverter, R V is the virtual resistance, i abc R V is the three-phase voltage of the virtual resistor, K PWM is the pulse width modulation gain coefficient.

[0051] Preferably, the first parameter determination module includes:

[0052] A data acquisition unit, used to acquire power data and current data of distributed photovoltaic inverters;

[0053] A state determination unit, configured to determine an operating state of the distributed photovoltaic inverter based on the power data and the current data; the operating state includes a normal operating state, a blocked wave state, and a power recovery state;

[0054] a first current reference value determining unit, configured to obtain, based on the power data under the normal operating state, a dq-axis current reference value under the normal operating state using a power controller;

[0055] a first voltage reference value determining unit, configured to obtain a three-phase modulation voltage reference value under the normal operating state using a current controller based on the dq axis current reference value under the normal operating state and the current data;

[0056] a second current reference value determining unit, configured to obtain, based on the dq axis current reference values ​​at the time of the normal operation state before the power recovery state begins, the dq axis current reference values ​​at each time in the power recovery state using a set slope;

[0057] The second voltage reference value determining unit is configured to obtain the three-phase modulation voltage reference value at each moment in the power recovery state using a current controller based on the current data in the power recovery state and the dq axis current reference values ​​at each moment.

[0058] Preferably, the first current reference value determining unit is specifically configured to:

[0059] Based on the power data under the normal operating state, obtaining a power deviation of the distributed photovoltaic inverter under the normal operating state;

[0060] After the power deviation passes through the power controller, the dq axis current reference value under the normal operating state is obtained.

[0061] Preferably, the first voltage reference value determining unit is specifically configured to:

[0062] Based on the current data, obtaining the dq axis current of the distributed photovoltaic inverter in the normal operating state;

[0063] Calculating the difference between the dq axis current reference value and the dq axis current in the normal operating state to obtain the dq axis current deviation;

[0064] The dq axis current deviation is subjected to a reverse Peek transformation by a current controller to obtain a three-phase modulation voltage reference value under the normal operating state.

[0065] Preferably, the second current reference value determining unit is specifically configured to:

[0066] The dq axis current reference value in the power recovery state starts from 0 and gradually recovers to the dq axis current reference value in the normal operation state before the wave blocking state begins according to the set slope, and obtains the dq axis current reference value at each moment in the power recovery state.

[0067] Preferably, the second voltage reference value determining unit is specifically configured to:

[0068] Based on the current data in the power recovery state, obtaining the dq-axis current of the distributed photovoltaic inverter at each moment in the power recovery state;

[0069] Based on each of the moments in the power recovery state, calculating a difference between a dq axis current reference value at the moment and the dq axis current at the moment to obtain a moment current deviation;

[0070] The current deviation at the moment is subjected to a reverse Peek transformation by a current controller to obtain a three-phase modulation voltage reference value at the moment.

[0071] Based on the same inventive concept, the present invention also provides an electromagnetic transient modeling method and system computer device for a distributed photovoltaic inverter wave-closing strategy, comprising: one or more processors;

[0072] a memory for storing one or more programs;

[0073] When the one or more programs are executed by the one or more processors, the electromagnetic transient modeling method of the distributed photovoltaic inverter blocking strategy as described above is implemented.

[0074] Based on the same inventive concept, the present invention also provides an electromagnetic transient modeling method for a distributed photovoltaic inverter wave-closing strategy and a system computer-readable storage medium, on which a computer program is stored. When the computer program is executed, the electromagnetic transient modeling method for a distributed photovoltaic inverter wave-closing strategy as described above is implemented.

[0075] Compared with the closest prior art, the present invention has the following beneficial effects:

[0076] The present invention provides an electromagnetic transient modeling method and system for a distributed photovoltaic inverter's wave-blocking strategy, comprising acquiring power data and current data of the distributed photovoltaic inverter, and obtaining current and voltage reference values ​​of the distributed photovoltaic inverter outside a wave-blocking state by utilizing a power-current dual-loop control principle; when the distributed photovoltaic inverter enters the wave-blocking state, setting the dq-axis current reference values ​​of the distributed photovoltaic inverter to zero, and setting a virtual resistor to reduce the simulated current of the distributed photovoltaic inverter to simulate the wave-blocking state; determining the three-phase voltage of the virtual resistor based on the current data, and obtaining a three-phase modulation voltage reference value in the wave-blocking state by utilizing a wave-blocking voltage reference value calculation formula based on the three-phase voltage of the virtual resistor to complete electromagnetic transient modeling; the method and system simulate the wave-blocking characteristics of the inverter by reducing the simulated current by introducing the virtual resistor, and do not rely on a detailed topological structure and an actual wave-blocking strategy, and do not require the establishment of a detailed switch model, so as to construct an electromagnetic transient model for the wave-blocking strategy of the distributed photovoltaic inverter, thereby enabling the use of a larger simulation step size, improving the simulation scale and simulation speed, and meeting the electromagnetic transient simulation requirements of large power grids. BRIEF DESCRIPTION OF THE DRAWINGS

[0077] Figure 1 A schematic flow chart of an electromagnetic transient modeling method for a distributed photovoltaic inverter wave blocking strategy provided by the present invention;

[0078] Figure 2A schematic diagram of a flow chart for determining the operating status of a distributed photovoltaic inverter provided by the present invention;

[0079] Figure 3 The electromagnetic transient model block diagram of the distributed photovoltaic inverter wave blocking strategy provided by the present invention;

[0080] Figure 4 This is a simulation waveform diagram of the distributed photovoltaic inverter provided by the present invention when the wave is closed;

[0081] Figure 5 A comparison chart of the test and simulation results of the distributed photovoltaic inverter voltage provided by the present invention;

[0082] Figure 6 A comparison chart of the test and simulation results of the distributed photovoltaic inverter current provided by the present invention;

[0083] Figure 7 A comparison chart of the test and simulation results of the active power of the distributed photovoltaic inverter provided by the present invention;

[0084] Figure 8 A comparison chart of the test and simulation results of the reactive power of the distributed photovoltaic inverter provided by the present invention;

[0085] Figure 9 A schematic diagram of the electromagnetic transient modeling system structure of a distributed photovoltaic inverter wave blocking strategy provided by the present invention;

[0086] Figure 10 This is a structural schematic diagram of an electronic device provided by the present invention. DETAILED DESCRIPTION

[0087] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0088] Example 1:

[0089] The present invention provides an electromagnetic transient modeling method for a distributed photovoltaic inverter blocking strategy, such as Figure 1 As shown, including:

[0090] S1. Based on the power data and current data of the distributed photovoltaic inverter, obtain the current and voltage reference values ​​of the distributed photovoltaic inverter outside the closed wave state;

[0091] S2. Set the dq axis current reference value of the distributed photovoltaic inverter to zero, and set a virtual resistance in the electromagnetic transient model to reduce the simulated current of the distributed photovoltaic inverter to simulate the closed wave state;

[0092] S3. Determine the three-phase voltage of the virtual resistor based on the current data, and obtain the three-phase modulation voltage reference value in the closed-wave state using a preset closed-wave voltage reference value calculation formula based on the three-phase voltage of the virtual resistor;

[0093] S4. Complete electromagnetic transient modeling based on the current and voltage reference values ​​outside the wave-blocking state and the three-phase modulation voltage reference values ​​in the wave-blocking state.

[0094] This method simulates the blocking characteristics of the inverter by introducing a virtual resistor to reduce the simulated current. It does not rely on the detailed topology structure and actual blocking strategy, and does not require the establishment of a detailed switching model. It can construct an electromagnetic transient model of the blocking strategy of a distributed photovoltaic inverter, thereby allowing the use of a larger simulation step size, improving the simulation scale and speed, and meeting the electromagnetic transient simulation needs of large power grids.

[0095] Considering that the electromagnetic transient model of the distributed photovoltaic inverter not only needs to construct the process of determining the simulated current in the wave-blocking state, but also needs to construct the process of determining the current and voltage reference values ​​outside the wave-blocking state, the power and current dual-loop control principle is used in the above S1 to determine the current and voltage reference values ​​outside the wave-blocking state, making the construction process of the entire electromagnetic transient model more complete.

[0096] In this embodiment, when determining the current and voltage reference values ​​outside the wave blocking state, the above S1 may include:

[0097] S101. Obtain power data and current data of distributed photovoltaic inverters;

[0098] S102: Determine the operating state of the distributed photovoltaic inverter based on the power data and the current data; the operating state includes a normal operating state, a blocking state, and a power recovery state;

[0099] S103, based on the power data under normal operating conditions, using a power controller to obtain dq axis current reference values ​​under normal operating conditions;

[0100] S104, based on the dq axis current reference value and current data under normal operating conditions, using a current controller to obtain a three-phase modulation voltage reference value under normal operating conditions;

[0101] S105, based on the dq axis current reference values ​​at the normal operating state before the power recovery state begins, using a set slope, obtaining the dq axis current reference values ​​at each moment in the power recovery state;

[0102] S106 , based on the current data in the power recovery state and the dq-axis current reference values ​​at each moment, using a current controller, obtain a three-phase modulation voltage reference value at each moment in the power recovery state.

[0103] In this embodiment, Figure 2 As shown, in the above S102, when determining the operating status of the distributed photovoltaic inverter, it may include:

[0104] When the three-phase current i abc Less than or equal to the overcurrent threshold i block When the distributed photovoltaic inverter is operating in normal operation, the status flag Flag_mode is set to 1;

[0105] When any phase current i a 、i b or i c Greater than the overcurrent threshold i block When the distributed photovoltaic inverter enters the closed wave state, the timing starts once the inverter enters the closed wave state and maintains the closed wave state. The status flag Flag_mode is set to 2;

[0106] When the duration of the wave envelope reaches the set value T block After that, it enters the power recovery state, and the state flag Flag_mode is set to 3;

[0107] If the difference between the real-time power and the power at the time of normal operation before the fault is less than the threshold, the power recovery is completed, the system switches back to normal operation, and the status flag Flag_mode is set to 1.

[0108] In this embodiment, the above S103 may include:

[0109] Based on the power data under normal operating conditions, the power deviation of the distributed photovoltaic inverter under normal operating conditions is obtained;

[0110] After the power deviation passes through the power controller, the dq axis current reference value under normal operating conditions is obtained.

[0111] Specifically, such as Figure 3 As shown, under normal operating conditions, the dq axis current reference values ​​come from the active power outer loop and the reactive power outer loop. For the active power outer loop, the active power reference value P ref The difference between the active power P and the active power P is passed through the active power controller to obtain the d-axis current reference value i dref1 The process of determining the d-axis current reference value under normal operating conditions satisfies the following formula:

[0112]

[0113] Where K pP and K iP are the proportional coefficient and integral coefficient of the active power controller respectively;

[0114] For the reactive power outer loop, the reactive power reference value Q ref The difference between the reactive power Q and the current Q is passed through the reactive power controller to obtain the q-axis current reference value i qref1 The determination process of the q-axis current reference value under normal operating conditions satisfies the following formula:

[0115]

[0116] Where K pQ and K iQ are the proportional coefficient and integral coefficient of the reactive power controller respectively.

[0117] In this embodiment, the above S104 may include:

[0118] Based on the current data, the dq axis current of the distributed photovoltaic inverter under normal operating conditions is obtained;

[0119] Calculate the difference between the dq axis current reference value and the dq axis current under normal operating conditions to obtain the dq axis current deviation;

[0120] The dq axis current deviation is subjected to a reverse Pike transformation by the current controller to obtain the three-phase modulation voltage reference value under normal operating conditions.

[0121] Specifically, the d-axis current reference value i under normal operating conditions is dref1 and the d-axis current i d The difference between the d-axis current deviation and the d-axis current deviation is obtained after the d-axis current controller obtains the d-axis modulation voltage reference value u under normal operating conditions. dref1 , expressed as:

[0122]

[0123] Where K pi and K ii are the proportional coefficient and integral coefficient of the current controller respectively;

[0124] The q-axis current reference value i under normal operating conditions qref and q-axis current i q The difference between the q-axis current deviation and the q-axis current deviation is obtained after the q-axis current controller obtains the q-axis modulation voltage reference value u under normal operating conditions. qref1 , expressed as:

[0125]

[0126] D-axis modulation voltage reference value u under normal operating conditions dref1 and q-axis modulation voltage reference value u qref1 After the dq-abc reverse Pike transformation, the abc three-phase modulation voltage reference value u is obtained under normal operating conditions.abcref1 .

[0127] In this embodiment, the above S105 may include:

[0128] The dq axis current reference value in the power recovery state starts from 0 and gradually recovers to the dq axis current reference value in the normal operation state before the wave blocking state begins according to the set slope, and the dq axis current reference value at each moment in the power recovery state is obtained.

[0129] It should be noted that the dq axis current reference values ​​at the time of the normal operation state before the start of the wave blocking state are obtained from the operation result of S103.

[0130] Specifically, in the power recovery state, the dq axis current reference value i dref3 and i qref3 Starting from 0, it gradually recovers to the initial set value before the fault according to the fixed slope, that is, the set slope, which is expressed as:

[0131]

[0132] Where i dref3_k and i dref3_k+1 are the d-axis current reference values ​​at the kth and k+1th control moments in the power recovery state, i qref3_k and i qref3_k+1 are the q-axis current reference values ​​at the kth and k+1th control moments in the power recovery state, K id and K iq are the recovery slopes of the d-axis and q-axis current reference values, respectively, and dt is the control cycle time.

[0133] In this embodiment, the above S106 may include:

[0134] Based on the current data in the power recovery state, the dq axis current of the distributed photovoltaic inverter at each moment in the power recovery state is obtained;

[0135] Based on each moment in the power recovery state, the difference between the dq axis current reference value at the moment and the dq axis current at the moment is calculated to obtain the current deviation at the moment;

[0136] The current deviation at each moment is subjected to a reverse Peek transformation by the current controller to obtain the three-phase modulation voltage reference value at each moment.

[0137] It should be noted that the current deviation at each moment is passed through the current controller to obtain the dq axis modulation voltage reference value u at each moment. dref3 and u qref3 After the dq axis modulation voltage reference value at each moment is reversed and transformed, the abc three-phase modulation voltage reference value u at each moment in the power recovery state is obtained. abcref3This process is similar to the process of performing a reverse Pike transformation on the dq axis current deviation after passing it through the current controller in S104.

[0138] In the Parker transformation, Figure 3 The parameter θ in represents the angle of the d-axis in the Park transform.

[0139] In this embodiment, in the above S2, the dq axis current reference value of the distributed photovoltaic inverter is set to zero, which is expressed as:

[0140] Let the d-axis current reference i of the distributed photovoltaic inverter in the closed-wave state be dref2 =0, the q-axis current reference i of the distributed photovoltaic inverter in the blocked state qref2 =0.

[0141] In this embodiment, in the above S2, a virtual resistor is set in the electromagnetic transient model to reduce the simulated current of the distributed photovoltaic inverter. When simulating the blocked wave state, the following steps may be included:

[0142] Based on the simulated current waveform in the current data, a virtual resistance is set in the electromagnetic transient model so that the simulated current drops to zero and converges within the set time, simulating the wave-enclosing state.

[0143] It should be noted that because we do not know the inverter's internal control strategy and only want to simulate its external grid-connected characteristics, we create a fictitious resistor to reduce the current amplitude and thus simulate a closed wave. The value of the fictitious resistor parameter is determined by the simulated waveform. The larger the fictitious resistor, the faster the current decreases. However, because discrete controllers have a one-beat delay, although the controller input is the current measurement, the actual output lags behind by one control cycle. Excessively large fictitious resistors can cause undesirable oscillations. Therefore, if the fictitious resistor is too small, the current decreases too slowly and the effect is poor. If the fictitious resistor is too large, oscillations may occur.

[0144] For example, a 2-pu virtual resistor is selected to simulate the blocking wave. The current can drop to near 0 within the set time of 500μs. The simulation results are as follows: Figure 4 shown.

[0145] In this embodiment, the above S3 may include:

[0146] Determine the three-phase voltage of the virtual resistor based on the current data, and substitute the three-phase voltage of the virtual resistor into the preset wave-enclosing voltage reference value calculation formula;

[0147] Based on the calculation formula of the closed-wave voltage reference value, the three-phase voltage difference between the three-phase terminal voltage of the distributed photovoltaic inverter and the three-phase voltage of the virtual resistor is calculated. After the coefficient conversion of the three-phase voltage difference, the three-phase modulation voltage reference value under the closed-wave state is obtained.

[0148] In this embodiment, the calculation formula of the sealing wave voltage reference value is expressed as:

[0149]

[0150] Among them, u abcref2 is the three-phase modulation voltage reference value in the blocked state, u termabc is the abc three-phase terminal voltage of the distributed photovoltaic inverter, i abc is the three-phase current of the distributed photovoltaic inverter, R V is the virtual resistance, i abc R V is the three-phase voltage of the virtual resistor, K PWM is the pulse width modulation gain coefficient.

[0151] According to the operating status of the inverter, calculate the actual three-phase modulation voltage u abcref , expressed as:

[0152]

[0153] According to the above steps, Figure 3 The electromagnetic transient model of the distributed photovoltaic inverter is shown in the figure. The simulation step size is set to 50μs. The simulation results of the distributed photovoltaic inverter when the wave is blocked are as follows: Figure 4 As shown, within about 500μs, the three-phase current I a , I b and I c The value of the inverter is then reduced to near zero and converged, avoiding undesirable oscillations and effectively simulating actual blocking characteristics. By introducing virtual resistors to simulate the blocking characteristics of the inverter, it is independent of the detailed topology and actual blocking strategy, eliminating the need for a detailed switching model. This allows for a larger simulation step size, improving simulation scale and speed, and meeting the simulation requirements of large power grids.

[0154] Comparison of test results and simulation results of distributed photovoltaic blocking wave, such as Figure 5-8 As shown in the figure, the comparison between the experimental and simulation results of voltage, current, active power and reactive power is shown respectively. The experimental results are basically consistent with the simulation results, which verifies the effectiveness of the electromagnetic transient modeling method.

[0155] Example 2:

[0156] Based on the same inventive concept, the present invention also provides an electromagnetic transient modeling system for a distributed photovoltaic inverter wave blocking strategy, such as Figure 9 As shown, including:

[0157] The first parameter determination module is used to obtain the current and voltage reference values ​​of the distributed photovoltaic inverter outside the closed wave state based on the power data and current data of the distributed photovoltaic inverter and the power and current dual-loop control principle;

[0158] The wave blocking simulation module is used to set the dq axis current reference value of the distributed photovoltaic inverter to zero and set a virtual resistance in the electromagnetic transient model to reduce the simulated current of the distributed photovoltaic inverter to simulate the wave blocking state;

[0159] A second parameter determination module is used to determine the three-phase voltage of the virtual resistor based on the current data, and to obtain the three-phase modulation voltage reference value under the wave-sealing state using a preset wave-sealing voltage reference value calculation formula based on the three-phase voltage of the virtual resistor;

[0160] Based on the current and voltage reference values ​​outside the wave-enclosed state and the three-phase modulation voltage reference values ​​in the wave-enclosed state, electromagnetic transient modeling is completed.

[0161] In this embodiment, the wave envelope simulation module is specifically used to:

[0162] Based on the simulated current waveform in the current data, a virtual resistance is set in the electromagnetic transient model to make the simulated current drop to zero and converge in the shortest time, simulating the wave-enclosing state.

[0163] In this embodiment, the second parameter determination module is specifically configured to:

[0164] Determine the three-phase voltage of the virtual resistor based on the current data, and substitute the three-phase voltage of the virtual resistor into the preset wave-enclosing voltage reference value calculation formula;

[0165] Based on the calculation formula of the closed-wave voltage reference value, the three-phase voltage difference between the three-phase terminal voltage of the distributed photovoltaic inverter and the three-phase voltage of the virtual resistor is calculated. After the coefficient conversion of the three-phase voltage difference, the three-phase modulation voltage reference value under the closed-wave state is obtained.

[0166] In this embodiment, the calculation formula of the sealing wave voltage reference value is expressed as:

[0167]

[0168] Among them, u abcref2 is the three-phase modulation voltage reference value in the blocked state, u termabc is the three-phase terminal voltage of the distributed photovoltaic inverter, i abc is the three-phase current of the distributed photovoltaic inverter, R V is the virtual resistance, i abc R V is the three-phase voltage of the virtual resistor, K PWM is the pulse width modulation gain coefficient.

[0169] In this embodiment, the first parameter determination module includes:

[0170] A data acquisition unit, used to acquire power data and current data of distributed photovoltaic inverters;

[0171] A state determination unit is used to determine the operating state of the distributed photovoltaic inverter based on power data and current data; the operating state includes normal operating state, wave blocking state and power recovery state;

[0172] a first current reference value determining unit, configured to obtain dq axis current reference values ​​under normal operating conditions using a power controller based on power data under normal operating conditions;

[0173] a first voltage reference value determining unit, configured to obtain a three-phase modulation voltage reference value under normal operating conditions using a current controller based on the dq axis current reference values ​​and current data under normal operating conditions;

[0174] a second current reference value determining unit, configured to obtain, based on the dq axis current reference values ​​at the time of the normal operation state before the power recovery state begins, the dq axis current reference values ​​at each time in the power recovery state by using a set slope;

[0175] The second voltage reference value determining unit is used to obtain the three-phase modulation voltage reference value at each moment in the power recovery state using the current controller based on the current data in the power recovery state and the dq axis current reference values ​​at each moment.

[0176] In this embodiment, the first current reference value determining unit is specifically configured to:

[0177] Based on the power data under normal operating conditions, the power deviation of the distributed photovoltaic inverter under normal operating conditions is obtained;

[0178] After the power deviation passes through the power controller, the dq axis current reference value under normal operating conditions is obtained.

[0179] In this embodiment, the first voltage reference value determining unit is specifically configured to:

[0180] Based on the current data, the dq axis current of the distributed photovoltaic inverter under normal operating conditions is obtained;

[0181] Calculate the difference between the dq axis current reference value and the dq axis current under normal operating conditions to obtain the dq axis current deviation;

[0182] The dq axis current deviation is subjected to a reverse Pike transformation by the current controller to obtain the three-phase modulation voltage reference value under normal operating conditions.

[0183] In this embodiment, the second current reference value determining unit is specifically configured to:

[0184] The dq axis current reference value in the power recovery state starts from 0 and gradually recovers to the dq axis current reference value in the normal operation state before the wave blocking state begins according to the set slope, and the dq axis current reference value at each moment in the power recovery state is obtained.

[0185] In this embodiment, the second voltage reference value determining unit is specifically configured to:

[0186] Based on the current data in the power recovery state, the dq axis current of the distributed photovoltaic inverter at each moment in the power recovery state is obtained;

[0187] Based on each moment in the power recovery state, the difference between the dq axis current reference value at the moment and the dq axis current at the moment is calculated to obtain the current deviation at the moment;

[0188] The current deviation at each moment is subjected to a reverse Peek transformation by the current controller to obtain the three-phase modulation voltage reference value at each moment.

[0189] Example 3

[0190] like Figure 10 As shown, the present invention also provides an electronic device, which may be a computer, a single-chip microcomputer, a smart mobile device, or the like. The electronic device in this embodiment may include a processor, a memory, a transceiver component, and the like. The memory, processor, and transceiver component are connected via a bus; the memory may be used to store an execution program, which may include instructions; and the processor may be used to execute the instructions stored in the memory. The memory may also be used to store data, which may be accessed and / or modified during the execution of the instructions.

[0191] The processor may be a central processing unit (CPU), or may be other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, which is suitable for implementing one or more instructions, specifically suitable for loading and executing one or more instructions in a storage medium to implement the corresponding method flow or corresponding function, so as to implement the steps of the electromagnetic transient modeling method of a distributed photovoltaic inverter sealing strategy in the above embodiment.

[0192] Example 4

[0193] Based on the same inventive concept, the present invention also provides a readable storage medium, specifically an electronic device readable storage medium (Memory), which is a memory device in the electronic device for storing programs and data. It can be understood that the storage medium here can include both the built-in storage medium in the electronic device and, of course, the extended storage medium supported by the electronic device. The storage medium provides a storage space, which stores the operating system of the terminal. In addition, one or more instructions suitable for being loaded and executed by the processor are also stored in the storage space. These instructions can be one or more execution programs (including program codes). It should be noted that the storage medium here can be a high-speed RAM memory or a non-volatile memory, such as at least one disk memory. The processor loads and executes one or more instructions stored in the storage medium, which can implement the steps of the electromagnetic transient modeling method of a distributed photovoltaic inverter sealing strategy in the above embodiment.

[0194] It will be understood by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Thus, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0195] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0196] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1The function specified in one or more boxes.

[0197] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0198] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit its scope of protection. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that after reading the present invention, those skilled in the art may still make various changes, modifications or equivalent substitutions to the specific implementation methods of the application, but these changes, modifications or equivalent substitutions are all within the scope of protection of the claims of the present invention.

Claims

1. An electromagnetic transient modeling method for a distributed photovoltaic inverter wave blocking strategy, characterized in that: include: Based on the power data and current data of the distributed photovoltaic inverter, obtaining the current and voltage reference values ​​of the distributed photovoltaic inverter outside the closed wave state; Setting the dq axis current reference value of the distributed photovoltaic inverter to zero, and setting a virtual resistance in the electromagnetic transient model to reduce the simulated current of the distributed photovoltaic inverter to simulate a closed wave state; Determine the three-phase voltage of the virtual resistor based on the current data, and obtain the three-phase modulation voltage reference value in the closed-wave state using a preset closed-wave voltage reference value calculation formula based on the three-phase voltage of the virtual resistor; The electromagnetic transient model is modeled based on the current and voltage reference values ​​outside the wave-enclosed state and the three-phase modulation voltage reference values ​​in the wave-enclosed state.

2. The method according to claim 1, wherein The setting of a virtual resistor in the electromagnetic transient model to reduce the simulated current of the distributed photovoltaic inverter and simulate the blocked wave state includes: Based on the simulated current waveform in the current data, a virtual resistance is set in the electromagnetic transient model so that the simulated current drops to zero and converges within a set time, simulating a wave-enclosing state.

3. The method according to claim 1 or 2, wherein: The determining of the three-phase voltage of the virtual resistor based on the current data, and obtaining the three-phase modulation voltage reference value in the closed-wave state by using a preset closed-wave voltage reference value calculation formula based on the three-phase voltage of the virtual resistor include: Determine the three-phase voltage of the virtual resistor based on the current data, and substitute the three-phase voltage of the virtual resistor into a preset wave-enclosing voltage reference value calculation formula; Based on the closed-wave voltage reference value calculation formula, the three-phase voltage difference between the three-phase terminal voltage of the distributed photovoltaic inverter and the three-phase voltage of the virtual resistor is calculated, and after coefficient conversion is performed on the three-phase voltage difference, the three-phase modulation voltage reference value under the closed-wave state is obtained.

4. The method according to claim 3, wherein The calculation formula of the reference value of the sealing wave voltage is expressed as: Among them, u abcref2 is the three-phase modulation voltage reference value in the blocked state, u termabc is the three-phase terminal voltage of the distributed photovoltaic inverter, i abc is the three-phase current of the distributed photovoltaic inverter, R V is the virtual resistance, i abc R V is the three-phase voltage of the virtual resistor, K PWM is the pulse width modulation gain coefficient.

5. The method according to claim 1 or 2, wherein: The obtaining of current and voltage reference values ​​of the distributed photovoltaic inverter outside the closed-wave state based on the power data and current data of the distributed photovoltaic inverter includes: Obtain power and current data of distributed photovoltaic inverters; Determining an operating state of the distributed photovoltaic inverter based on the power data and the current data; the operating state includes a normal operating state, a blocking state, and a power recovery state; Based on the power data under the normal operating state, using a power controller, obtaining a dq axis current reference value under the normal operating state; Based on the dq axis current reference value and the current data in the normal operating state, using a current controller, obtaining a three-phase modulation voltage reference value in the normal operating state; Based on the dq axis current reference values ​​at the normal operating state before the power recovery state begins, using a set slope, obtain the dq axis current reference values ​​at each moment in the power recovery state; Based on the current data in the power recovery state and the dq-axis current reference values ​​at each moment, a current controller is used to obtain the three-phase modulation voltage reference values ​​at each moment in the power recovery state.

6. The method according to claim 5, wherein The obtaining, based on the power data in the normal operating state, using a power controller, the dq axis current reference values ​​in the normal operating state includes: Based on the power data under the normal operating state, obtaining a power deviation of the distributed photovoltaic inverter under the normal operating state; After the power deviation passes through the power controller, the dq axis current reference value under the normal operating state is obtained.

7. The method according to claim 5, wherein The obtaining of the three-phase modulation voltage reference value under the normal operating state by using a current controller based on the dq axis current reference value under the normal operating state and the current data includes: Based on the current data, obtaining the dq axis current of the distributed photovoltaic inverter in the normal operating state; Calculating the difference between the dq axis current reference value and the dq axis current in the normal operating state to obtain the dq axis current deviation; The dq axis current deviation is subjected to a reverse Peek transformation by a current controller to obtain a three-phase modulation voltage reference value under the normal operating state.

8. The method according to claim 5, wherein The step of obtaining the dq axis current reference values ​​at each moment in the power recovery state based on the dq axis current reference values ​​at the normal operating state before the power recovery state starts and using a set slope includes: The dq axis current reference value in the power recovery state starts from 0 and gradually recovers to the dq axis current reference value in the normal operation state before the wave blocking state begins according to the set slope, and obtains the dq axis current reference value at each moment in the power recovery state.

9. The method according to claim 5, wherein The method of obtaining the three-phase modulation voltage reference value at each moment in the power recovery state by using a current controller based on the current data in the power recovery state and the dq-axis current reference value at each moment includes: Based on the current data in the power recovery state, obtaining the dq-axis current of the distributed photovoltaic inverter at each moment in the power recovery state; Based on each of the moments in the power recovery state, calculating a difference between a dq axis current reference value at the moment and the dq axis current at the moment to obtain a moment current deviation; The current deviation at the moment is subjected to a reverse Peek transformation by a current controller to obtain a three-phase modulation voltage reference value at the moment.

10. An electromagnetic transient modeling system for a distributed photovoltaic inverter wave blocking strategy, characterized in that: include: A first parameter determination module is configured to obtain current and voltage reference values ​​of the distributed photovoltaic inverter outside a closed-wave state based on power data and current data of the distributed photovoltaic inverter; A wave blocking simulation module is used to set the dq axis current reference value of the distributed photovoltaic inverter to zero and set a virtual resistance in the electromagnetic transient model to reduce the simulated current of the distributed photovoltaic inverter to simulate the wave blocking state; a second parameter determination module, configured to determine the three-phase voltage of the virtual resistor based on the current data, and obtain a three-phase modulation voltage reference value in a wave-sealed state using a preset wave-sealed voltage reference value calculation formula based on the three-phase voltage of the virtual resistor; Electromagnetic transient modeling is completed based on the current and voltage reference values ​​outside the wave-enclosed state and the three-phase modulation voltage reference values ​​in the wave-enclosed state.

11. The system according to claim 10, wherein: The wave envelope simulation module is specifically used for: Based on the simulated current waveform in the current data, a virtual resistance is set in the electromagnetic transient model so that the simulated current drops to zero and converges within a set time, simulating a wave-enclosing state.

12. The system according to claim 10 or 11, characterized in that The second parameter determination module is specifically configured to: Determine the three-phase voltage of the virtual resistor based on the current data, and substitute the three-phase voltage of the virtual resistor into a preset wave-enclosing voltage reference value calculation formula; Based on the closed-wave voltage reference value calculation formula, the three-phase voltage difference between the three-phase terminal voltage of the distributed photovoltaic inverter and the three-phase voltage of the virtual resistor is calculated, and after coefficient conversion is performed on the three-phase voltage difference, the three-phase modulation voltage reference value under the closed-wave state is obtained.

13. The system according to claim 12, wherein: The calculation formula of the reference value of the sealing wave voltage is expressed as: Among them, u abcref2 is the three-phase modulation voltage reference value in the blocked state, u termabc is the three-phase terminal voltage of the distributed photovoltaic inverter, i abc is the three-phase current of the distributed photovoltaic inverter, R V is the virtual resistance, i abc R V is the three-phase voltage of the virtual resistor, K PWM is the pulse width modulation gain coefficient.

14. The system according to claim 10 or 11, characterized in that The first parameter determination module includes: A data acquisition unit, used to acquire power data and current data of distributed photovoltaic inverters; A state determination unit, configured to determine an operating state of the distributed photovoltaic inverter based on the power data and the current data; the operating state includes a normal operating state, a blocked wave state, and a power recovery state; a first current reference value determining unit, configured to obtain, based on the power data under the normal operating state, a dq-axis current reference value under the normal operating state using a power controller; a first voltage reference value determining unit, configured to obtain a three-phase modulation voltage reference value under the normal operating state using a current controller based on the dq axis current reference value under the normal operating state and the current data; a second current reference value determining unit, configured to obtain, based on the dq axis current reference values ​​at the time of the normal operation state before the power recovery state begins, the dq axis current reference values ​​at each time in the power recovery state using a set slope; The second voltage reference value determining unit is configured to obtain the three-phase modulation voltage reference value at each moment in the power recovery state using a current controller based on the current data in the power recovery state and the dq axis current reference values ​​at each moment.

15. The system according to claim 14, wherein: The first current reference value determining unit is specifically configured to: Based on the power data under the normal operating state, obtaining a power deviation of the distributed photovoltaic inverter under the normal operating state; After the power deviation passes through the power controller, the dq axis current reference value under the normal operating state is obtained.

16. The system of claim 14, wherein: The first voltage reference value determining unit is specifically configured to: Based on the current data, obtaining the dq axis current of the distributed photovoltaic inverter in the normal operating state; Calculating the difference between the dq axis current reference value and the dq axis current in the normal operating state to obtain the dq axis current deviation; The dq axis current deviation is subjected to a reverse Peek transformation by a current controller to obtain a three-phase modulation voltage reference value under the normal operating state.

17. The system of claim 14, wherein: The second current reference value determining unit is specifically configured to: The dq axis current reference value in the power recovery state starts from 0 and gradually recovers to the dq axis current reference value in the normal operation state before the wave blocking state begins according to the set slope, and obtains the dq axis current reference value at each moment in the power recovery state.

18. The system of claim 14, wherein: The second voltage reference value determining unit is specifically configured to: Based on the current data in the power recovery state, obtaining the dq-axis current of the distributed photovoltaic inverter at each moment in the power recovery state; Based on each of the moments in the power recovery state, calculating a difference between a dq axis current reference value at the moment and the dq axis current at the moment to obtain a moment current deviation; The current deviation at the moment is subjected to a reverse Peek transformation by a current controller to obtain a three-phase modulation voltage reference value at the moment.

19. An electronic device, characterized in that: include: at least one processor and memory; The memory and the processor are connected via a bus; The memory is used to store one or more programs; When the one or more programs are executed by the at least one processor, the electromagnetic transient modeling method of the distributed photovoltaic inverter sealing strategy according to any one of claims 1 to 9 is implemented.

20. A readable storage medium, characterized in that An execution program is stored thereon, and when the execution program is executed, an electromagnetic transient modeling method of a distributed photovoltaic inverter sealing strategy according to any one of claims 1 to 9 is implemented.

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