Virtual synchronous generator control method based on discontinuous control strategy

Abstract

The invention relates to the field of power systems and energy management, and discloses a discontinuous control strategy-based virtual synchronous generator control method, which comprises the following steps of S1, initializing parameter setting of each inverter; s2, setting a reference frequency and a reference voltage of the system; s3, before the new inverter is connected, pre-synchronization control is carried out through the pre-synchronization input quantity, so that the output frequency and voltage of the new inverter are synchronized with those of the existing system; s4, monitoring system frequency and voltage in real time, and detecting and calculating frequency deviation and voltage deviation; s5, when the frequency deviation or the voltage deviation exceeds a preset threshold value, starting an adjustment mechanism, and recalculating the frequency adjustment coefficient and the voltage adjustment coefficient; and S6, adjusting the output of each inverter to maintain power balance and ensure that the frequency and the voltage are consistent with the reference frequency and the reference voltage. By dynamically adjusting the output response system change of the inverter, the stability of the micro-grid and the parallel connection efficiency of the inverter are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of power system and energy management, and in particular to a virtual synchronous generator control method based on a discontinuous control strategy. Background Art

[0002] Inverter parallel control in microgrid is one of the key technologies to ensure stable operation of the power grid.

[0003] In peer-to-peer control without interconnected signal lines, the lack of direct instructions for active and reactive power often leads to static errors in voltage and frequency, which affects the stability and efficiency of the system. In addition, power balance is an important indicator to measure the effect of inverter parallel connection, but in actual operation, it often faces current sharing problems caused by unequal inverter capacities. Therefore, how to achieve power balance and maintain a small static error in the parallel operation of inverters of different capacities is a difficult problem that needs to be solved in the current development of microgrid technology.

[0004] In conventional virtual synchronous generator control methods, time-continuous control methods are usually used, so the adjustment coefficient correction is a real-time change intervention. This method can ensure output continuity and reduce fluctuations, but it will accumulate error variables over time and easily produce large static errors when multiple inverters are connected in parallel. The present invention adopts a time-discontinuous control method, and the intervention of the adjustment coefficient correction is only when the output power detects that the frequency or voltage fluctuates and exceeds the threshold f thr , U thr is triggered when it is below the threshold value f thr , U thr This method can effectively eliminate the error variables caused by the accumulation of time factors, thereby achieving power balance and maintaining a small static error. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a virtual synchronous generator control method based on a discontinuous control strategy, which solves the problems of power balance and voltage and frequency stability when inverters are connected asynchronously in a microgrid.

[0006] To achieve the above objectives, the present invention proposes a virtual synchronous generator control method based on a discontinuous control strategy to solve the problem of power balance and static error reduction of the inverter asynchronously connected to the power grid system, including the following steps:

[0007] Initialize the virtual moment of inertia J, damping coefficient D, active-frequency droop coefficient m, reactive-voltage droop coefficient n, line impedance X and rated output power P of each inverter Ni ;

[0008] Set the system reference frequency f ref and reference voltage U ref, where the reference angular frequency ω ref Defined as 2πf ref ;

[0009] Before the new inverter is connected, the pre-synchronization input quantity P com and Q com Perform pre-synchronization control to synchronize the output frequency and voltage of the new inverter with the existing system;

[0010] Monitor system frequency and voltage in real time, detect and calculate frequency deviation f e And voltage deviation U e ;

[0011] When f e or U e Exceeding the preset threshold f thr , U thr When the frequency adjustment factor f is recalculated, the adjustment mechanism is started based on the discontinuous control strategy. adj And the voltage regulation factor U adj :

[0012]

[0013] Among them, k p is the proportionality coefficient, k i is the integral coefficient, P Ni is the rated output power of each inverter, t0 is the time when adjustment starts, C0 is the compensation constant, f e (τ) and U e (τ) are the frequency and voltage deviation at time τ, respectively;

[0014] Dynamically adjust the output of each inverter according to the system load and operating conditions to adapt to different operating environments, maintain power balance and ensure that frequency and voltage are consistent with f ref and U ref Consistent.

[0015] The present invention also provides a virtual synchronous generator control system based on a discontinuous control strategy, comprising:

[0016] Multiple parallel inverters, each inverter has a virtual moment of inertia J, a damping coefficient D, an active-frequency droop coefficient m, a reactive-voltage droop coefficient n, a line impedance X, and a rated output power P Ni ;

[0017] Monitoring module, used to monitor the frequency and voltage of the microgrid in real time;

[0018] The pre-synchronization control module is used to calculate the pre-synchronization input quantity P before the new inverter is connected com and Q com , and adjust the output frequency and voltage of the new inverter;

[0019] Adjustment module, used to calculate and adjust the frequency adjustment coefficient f adj And the voltage regulation factor U adj And ensure the output power of each inverter is balanced;

[0020] The control module adopts a discontinuous control strategy to ensure that the adjustment f is recalculated and adjusted when frequency or voltage fluctuations are detected. adj and U adj , until the frequency or voltage fluctuation is lower than the threshold f thr , U thr .

[0021] The present invention also provides a computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the above method is implemented.

[0022] The present invention also provides a storage medium on which a computer program is stored. When the computer program is executed by a processor, the method described above is implemented.

[0023] The present invention provides a method for controlling a virtual synchronous generator based on a discontinuous control strategy for an inverter asynchronously connected to a power grid system. The method has the following beneficial effects:

[0024] 1. The control method of the present invention improves the stability of the microgrid and the parallel efficiency of the inverter by dynamically adjusting the output of the inverter to respond to system changes. In addition, the pre-synchronization control step reduces the impact of the new inverter access to the system and reduces the risk caused by frequency and voltage mismatch. Through real-time monitoring and adaptive adjustment, the method enhances the system's adaptability to load changes and ensures the continuity and high quality of power supply.

[0025] 2. The present invention significantly improves the response speed and sensitivity of the microgrid to load changes, equipment failures, or the incorporation of new inverters by real-time monitoring of the system's frequency and voltage and timely adjusting the inverter output. This high degree of system responsiveness ensures the continuity and stability of power supply and reduces grid failures caused by frequency and voltage fluctuations.

[0026] 3. The present invention effectively promotes the balanced distribution of power in the entire microgrid by accurately controlling the power output of each inverter to match its load demand. This not only reduces the circulating current and energy loss in the system, but also optimizes the efficiency of resource utilization, helping to reduce operating costs and environmental impact.

[0027] 4. The present invention supports asynchronous access of new inverters and ensures seamless integration of new inverters into the microgrid through a pre-synchronization control mechanism, thereby enhancing the scalability and flexibility of the system. This allows the microgrid to easily adapt to changing energy demands and technology upgrades, and supports the access of more renewable energy and distributed energy resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the method flow of the present invention;

[0029] Figure 2 This is a block diagram of the improved active power-frequency droop control of the present invention;

[0030] Figure 3 This is a block diagram of the improved reactive power-voltage droop control of the present invention;

[0031] Figure 4 A schematic diagram of a microgrid according to the present invention;

[0032] Figure 5 This is the f0 correction flow chart of the present invention;

[0033] Figure 6 It is the U0 correction flow chart of the present invention;

[0034] Figure 7 A simulation test circuit diagram of an embodiment of the present invention;

[0035] Figure 8 The inverter output active power curve diagram of the embodiment of the present invention;

[0036] Fig. 9 The inverter output reactive power curve diagram of the embodiment of the present invention;

[0037] Fig.10 Schematic diagram of the ratio of the output frequency to the rated frequency of an embodiment of the present invention;

[0038] Fig.11 Schematic diagram of the ratio of the output voltage to the rated voltage of an embodiment of the present invention;

[0039] Fig.12 It is a schematic diagram of the structure of the device of the present invention;

[0040] Fig.13 It is a schematic diagram of the computer device structure of the present invention.

[0041] Among them, 100, multiple parallel inverters; 200, monitoring module; 300, pre-synchronization control module; 400, adjustment module; 500, control module; 40, computer equipment; 41, processor; 42, memory; 43, storage medium. DETAILED DESCRIPTION

[0042] The following will be combined with the drawings in the specification of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] Please refer to the attached Figure 1 The embodiment of the present invention provides a virtual synchronous generator control method based on a discontinuous control strategy, aiming to optimize the coordinated operation of multiple inverters in a microgrid, especially to maintain the stability and power balance of the grid when the inverters are connected at different times.

[0044] Specifically, the method comprises the following steps:

[0045] S1. Initialization settings

[0046] In this step, set the key control parameters for each inverter:

[0047] Virtual moment of inertia J: simulates the moment of inertia of the synchronous generator and provides the inverter with the necessary inertial response capability to resist the frequency fluctuation caused by sudden load changes.

[0048] Damping coefficient D: Provides system damping and reduces frequency and voltage oscillations.

[0049] Active-frequency droop coefficient m and reactive-voltage droop coefficient n: These two coefficients determine the sensitivity of the inverter in adjusting active and reactive output when the grid frequency or voltage changes.

[0050] Line impedance X: reflects the electrical connection characteristics between the inverter and other parts of the power grid.

[0051] Rated output power P Ni : Determine the rated output capacity of each inverter.

[0052] The correct setting of these parameters is the basis for achieving efficient and stable control, ensuring that the inverter can adapt to different grid conditions and load changes.

[0053] In this embodiment, the specific setting methods of these parameters are as follows:

[0054] 1. Active power-frequency droop control:

[0055] Active power-frequency droop control combines the prime mover regulation equation and the rotor motion equation. The details are as follows:

[0056] Prime mover regulation equation:

[0057]

[0058] Where: P m is the output power of the prime mover; P com is the pre-synchronization input active power command; m is the active-frequency droop coefficient; ω0, ω are the rated rotor angular velocity and the actual rotor angular velocity respectively, where ω0 = 2πf N .

[0059] The rotor motion equation based on the discontinuous control strategy is:

[0060]

[0061] Where: P is the instantaneous active power; J is the virtual moment of inertia; D is the damping coefficient; δ is the power angle; ω ref Reference angular frequency; ω0 Rated angular frequency; f adj Frequency adjustment factor.

[0062] Based on the virtual synchronous generator control method under the discontinuous control strategy, active power equalization of multiple inverters in parallel can be achieved through active-frequency control to keep the output frequency consistent.

[0063] like Figure 7 As shown in FIG. 1 , it is a block diagram of active power-frequency droop control based on discontinuous control strategy. Based on the virtual synchronous generator control method under discontinuous control strategy, active power sharing of multiple inverters in parallel can be achieved through active power-frequency droop control to keep the output frequency consistent.

[0064] 2. Reactive power-voltage droop control:

[0065] Under the condition that the circuit impedance is inductive, the reactive power-voltage droop control equation of the virtual synchronous generator control method based on the discontinuous control strategy is as follows:

[0066] U=n(Q com -Q)+U ref +U adj (3)

[0067] Where: n is the reactive power-voltage droop coefficient; Q com Pre-synchronization input reactive power command; Q is instantaneous reactive power; U ref is the reference voltage; U is the actual output voltage; U adj Voltage regulation factor.

[0068] Based on the virtual synchronous generator control method under the discontinuous control strategy, reactive power equalization of multiple inverters in parallel can be achieved through reactive-voltage droop control to keep the output voltage consistent.

[0069] like Figure 8As shown in FIG. 1 , it is a reactive power-voltage droop control block diagram based on a discontinuous control strategy. It can realize reactive power sharing of multiple inverters in parallel and keep the output voltage consistent.

[0070] 3. Parameter selection:

[0071] The values ​​of droop coefficients m and n are:

[0072]

[0073]

[0074] Where: f N ,U N ,S N They are rated frequency, rated voltage, and rated inverter capacity respectively.

[0075] The values ​​of virtual moment of inertia J and damping coefficient D are:

[0076]

[0077] Where: ΔP max is the maximum power change, Δf max is the maximum frequency change.

[0078] 4. Set the line impedance X:

[0079] The line impedance X needs to be set according to the line parameters of the actual system to ensure the accuracy of power distribution when the inverters are running in parallel.

[0080] 5. Set the rated output power P Ni :

[0081] Rated output power P of each inverter Ni It needs to be set according to the specific inverter model and the overall design requirements of the system to ensure that each inverter can reasonably share the system load during parallel operation.

[0082] Through the above settings, the virtual synchronous generator control method based on the discontinuous control strategy can achieve precise control of active and reactive power in the microgrid, thereby ensuring power balance between inverters and stable operation of the power grid.

[0083] S2, set reference frequency and voltage

[0084] Based on the virtual synchronous generator control method under the discontinuous control strategy, it is crucial to set the system reference frequency and reference voltage, because these parameters define the reference point for the entire grid operation. This step ensures that all parallel inverters operate with consistent electrical characteristics, thereby maintaining the stability and power quality of the grid.

[0085] In this embodiment, the method for setting the reference frequency and voltage is as follows:

[0086] 1. Reference frequency f ref Choices:

[0087] The reference frequency of the system is usually set to the standard frequency of the power grid, such as 50Hz or 60Hz, depending on the power grid standard in the area.

[0088] Reference frequency f ref The setting of is crucial to the synchronous operation of the entire power grid, because all inverter control strategies will adjust their output according to this frequency to ensure seamless parallel connection with the power grid.

[0089] 2. Reference voltage U ref Choices:

[0090] The reference voltage setting should comply with the standard operating voltage of the power grid, such as 400V, 230V, 110kV, etc. The specific value depends on the level and operating requirements of the power grid.

[0091] Setting an accurate reference voltage is the key to ensuring grid voltage stability and correct inverter operation, which affects the inverter's reactive power regulation and the voltage quality of the entire system.

[0092] 3. Reference angular frequency ω ref Calculation:

[0093] Reference angular frequency ω ref is based on the reference frequency f ref Calculated, using the formula ω ref =2πf ref .

[0094] This angular frequency will be used in various dynamic calculations and control strategies of the inverter, especially when dealing with frequency-dependent dynamic responses.

[0095] S3, pre-synchronization control

[0096] This step is the key link of the virtual synchronous generator control method based on the discontinuous control strategy in the microgrid. It aims to prepare the grid connection of the new inverter through pre-synchronization control to ensure that it will not interfere with the existing power grid when connected.

[0097] In this embodiment, pre-synchronization control is a key step to ensure that the impact on system stability is reduced when a new inverter is connected to the microgrid system. com and Q com , the new inverter can be synchronized with the frequency and voltage of the existing system before being connected. The specific steps are as follows:

[0098] 1. Pre-synchronization input quantity P com and Q com :

[0099] Pre-synchronization input quantity P com and U com It means that before the new inverter is connected to the system, the current frequency and voltage of the system are measured in real time to calculate the active and reactive power corresponding to the new inverter as the pre-synchronization input.

[0100] In this embodiment, the pre-synchronization input quantity P is calculated com and Q com Reasonable adjustments are mainly made based on the current system operating status and the parameters of the new inverter.

[0101] 2. Execution of pre-synchronization control:

[0102] Before the new inverter is connected, the pre-synchronization input quantity P com and Q com As input parameter, a presynchronization control is performed.

[0103] Adjust the output of the new inverter so that its frequency and voltage gradually approach the reference frequency f of the system ref and reference voltage U ref , to achieve synchronization.

[0104] 3. Frequency and voltage synchronization:

[0105] Through pre-synchronization control, the output frequency and voltage of the new inverter are made consistent with the frequency and voltage of the existing system.

[0106] Ensure that during the integration process, the new inverter will not cause significant fluctuations in system frequency and voltage, reducing the impact on system stability.

[0107] 4. Verify the synchronization status:

[0108] Before a new inverter is connected to the system, verify whether its output frequency and voltage are consistent with the system reference value f ref and U ref Consistent.

[0109] If they are consistent, the new inverter is allowed to be connected to the system; if they are inconsistent, the adjustment will continue until the synchronization state is achieved.

[0110] 5. Access system:

[0111] Once the output frequency and voltage of the new inverter are synchronized with the system, the integration operation is performed to connect the new inverter to the microgrid system.

[0112] After connection, the operating status of the new inverter is continuously monitored to ensure its stable operation and maintain the power balance of the system.

[0113] By implementing the above steps, it is ensured that the new inverter can be smoothly connected to the microgrid system and synchronize the frequency and voltage with the existing system, thereby reducing the system instability caused by asynchronous access and ensuring the overall stable operation of the system.

[0114] S4. Real-time monitoring and deviation calculation

[0115] The system continuously monitors the current frequency and voltage and calculates the relative value f ref and U ref The deviation f e and U e This step is the basis for dynamically responding to system changes and making necessary adjustments.

[0116] S5. Start the adjustment mechanism

[0117] When the detected frequency deviation f e Or voltage deviation U e Exceeding the preset threshold f thr , U thr When the adjustment mechanism is started, the frequency adjustment coefficient f is recalculated. adj And the voltage regulation factor U adj This step ensures that the microgrid can respond quickly under dynamic conditions and maintain the stable operation of the system.

[0118] The specific steps are as follows:

[0119] 1. Start the adjustment mechanism:

[0120] In this embodiment, once the frequency deviation f e Or voltage deviation U e Exceeds the pre-set threshold value f thr , U thr , the system automatically triggers the adjustment mechanism. These thresholds are preset based on system stability and sensitivity requirements.

[0121] 2. Recalculate the frequency adjustment coefficient f adj And the voltage regulation factor U adj :

[0122] Frequency adjustment factor f adj And the voltage regulation factor U adj The recalculation uses the following formula:

[0123]

[0124] Among them, k p is the proportionality coefficient, k i is the integral coefficient, P Niis the rated output power of each inverter, t0 is the time when adjustment starts, C0 is the compensation constant, f e (τ) and U e (τ) are the frequency and voltage deviation at time τ, respectively;

[0125] 3. Selection and setting of adjustment parameters:

[0126] Proportional coefficient k p and the integration coefficient k i The settings of are determined according to the specific needs and response characteristics of the system. These parameters affect the sensitivity and stability of the adjustment process.

[0127] Specifically, according to equations (1) and (2), the pre-synchronization input power command P com ,Q com Corresponding to the frequency and voltage regulation coefficient f adj , U adj From the perspective of power balancing, it is easy to obtain the f that each inverter needs to dynamically maintain consistency adj , U adj . This is the f of the inverter before parallel connection. adj , U adj It can be inconsistent, as long as the f adj , U adj The same can achieve power balance.

[0128] like Figure 4 The figure shows a schematic diagram of a microgrid, assuming that each inverter in the figure operates based on a virtual synchronous generator control method under a discontinuous control strategy. When the load changes dynamically or a new inverter is added to or removed from the grid, a new power balance needs to be established, which will inevitably lead to frequency and voltage fluctuations. adj , U adj Discontinuous control is adopted. When the frequency and voltage fluctuations are detected to exceed the threshold value f thr , U thr Reset f adj , U adj , calculate and adjust f according to equations (8) and (9) adj , U adj , until the difference between frequency and voltage and rated value is e , U e If it is less than a certain threshold, stop calculating and keep f adj , U adj Output.

[0129] Since the dynamic change of load is different from the power flow direction of the new inverter connected to the grid, the frequency regulation coefficient f adj The adjustment time period required for restarting the calculation also has obvious differences. Therefore, the present invention defines a new variable Pk After the new inverter is connected to the grid, its instantaneous frequency is derived and then divided by the rated power P Ni , and after filtering, find its absolute value to obtain the P of the new inverter k P can be plotted against time. k The curve is used as the frequency adjustment factor f adj The basis for determining whether to restart the calculation.

[0130] P k The curve will show an obvious single peak phenomenon and gradually approach 0 as time goes by, entering a steady state. In order to accelerate convergence, the frequency adjustment coefficient f is defined adj Restart calculation period T set , and set P set , requiring that f +T set Within the time, its value is less than and close to P k Curve value.

[0131] When the frequency and voltage fluctuations exceed the threshold value f thr , U thr When f adj and U adj If it exceeds T set Time, inverter P k The value is still greater than P set , then the frequency adjustment coefficient f adj The calculation must be restarted.

[0132] The core of the virtual synchronous generator control method based on the discontinuous control strategy described above is f adj , U adj Calculation method, determination of reset and hold time, frequency adjustment coefficient f adj Resetting judgment. Because its judgment is based on the frequency and voltage values ​​on the microgrid line, it can ensure the consistency of the adjustment time of each parallel inverter, achieve synchronous adjustment, ensure power balance, and the two calculations are independent and do not interfere with each other. The overall process Figure 5 and 6 shown.

[0133] In terms of design, Figure 5 and 6 It means that if the newly cut-in load or inverter capacity is not enough to cause the frequency and voltage fluctuation to reach the threshold, then f adj , U adjIt will not enter into readjustment, and will maintain the original parameters until the next event occurs. And this adjustment is not affected by the previous adjustment. In other words, even if the effect of this adjustment does not meet expectations and there is a certain static error, it can be corrected in the next adjustment. Therefore, the virtual synchronous generator control method based on the discontinuous control strategy of the present invention has a certain redundancy.

[0134] S6. Maintain power balance

[0135] Adjust the output of each inverter to ensure that the power is balanced and consistent with the system's reference frequency and voltage. This step ensures that even if a new inverter is connected or the load changes suddenly, the system can quickly restore the balance state and maintain the continuity and reliability of operation.

[0136] In this embodiment, the output of each inverter is adjusted to maintain power balance and ensure that the frequency and voltage are consistent with the system reference frequency f ref and reference voltage U ref This step is the terminal implementation of dynamic adjustment of the system to ensure the stable operation and efficient energy distribution of the microgrid.

[0137] The specific steps are as follows:

[0138] 1. Adjust output power and voltage:

[0139] In this embodiment, according to the frequency adjustment coefficient f recalculated in step S5 adj And the voltage regulation factor U adj , adjust the active and reactive output of each inverter. This adjustment ensures that the frequency and voltage output of all inverters meet the reference values ​​set by the system.

[0140] 2. Power balance control:

[0141] Power balancing between inverters is achieved by adjusting active and reactive output. Power balancing is a key stability factor in microgrids, especially in multi-inverter systems. Proper power distribution can reduce circulating currents and potential imbalances within the system.

[0142] 3. Ensure frequency and voltage consistency:

[0143] System monitoring ensures that all inverters adjust their output frequency and voltage to the same level as f ref and U ref Consistency. The consistency of frequency and voltage is the key to maintaining system stability and power quality.

[0144] 4. Continuous monitoring and adjustment:

[0145] In this embodiment, the system will continuously monitor the output of each inverter and the status of the entire microgrid. Any deviation from the preset parameters will trigger readjustment to ensure the long-term stability and reliability of the system.

[0146] This step uses a closed-loop control strategy to adjust the inverter output through continuous feedback to achieve the preset system parameters. The closed-loop control system provides a dynamic self-adjustment method that can cope with various changes and disturbances inside and outside the system.

[0147] This step not only enhances the stability of the microgrid by maintaining power balance and consistency of frequency and voltage, but also optimizes the efficiency of energy utilization. This is especially important for modern microgrids that include renewable energy and multiple energy storage devices, as these factors usually introduce more changes and uncertainties.

[0148] The control method of the present invention improves the stability of the microgrid and the parallel efficiency of the inverter by dynamically adjusting the output of the inverter to respond to system changes. In addition, the pre-synchronization control step reduces the impact of the new inverter access on the system and reduces the risk caused by frequency and voltage mismatch. Through real-time monitoring and adaptive adjustment, the method enhances the system's adaptability to load changes and ensures the continuity and high quality of power supply.

[0149] Example: Simulation Verification

[0150] Experimental simulation circuit Figure 7 As shown, it is based on a 380V / 50Hz island microgrid.

[0151] according to Figure 7 As shown in the simulation test circuit, the power supply in the microgrid system is equivalent to a DC power supply; the impedance network Lfi1, Lfi2, Rfi, Cfi (i = 1, 2, 3 ...) together constitute an LCL filter; the impedance Rgi, Lgi (i = 1, 2, 3 ...) is the transmission line impedance, and the parameters are shown in Table 1:

[0152] Table 1 Simulation test parameters

[0153]

[0154] Load 1 is a normally connected load, with a rated capacity of active power: 20kW, reactive power: 10kVAR; load 2 is connected at 3s and cut off at 4s, with a rated capacity of active power: 10kW, reactive power: 5kVAR.

[0155] The experimental test results are as follows: Figure 8 , Fig. 9It can be seen that when the new inverter is connected, after a period of adjustment, the system can tend to be stable and achieve equal distribution of active power and reactive power. And because the line impedance of inverter 1 and inverter 2 is inconsistent, there is a deviation in the equal distribution of reactive power, but it does not affect the equal distribution of active power. In the face of load 2 switching in and out in 3s to 4s, the three inverters can respond quickly. And after the inverter is connected and adjusted again, the equal distribution error existing in the early stage is optimized again, and the equal distribution effect is effectively improved, which verifies the effectiveness of the present invention.

[0156] like Fig.10 As shown in the figure, the virtual synchronous generator control method based on the discontinuous control strategy is used every time the frequency fluctuation reaches the threshold value f thr , U thr The actual frequency changes less than 0.4% each time an event is triggered, and it can quickly stabilize. The frequency static error is very small in steady state, and the ratio of the output frequency to the rated frequency is close to 1. The experimental results show that the system has good stability.

[0157] like Fig.11 As shown, the voltage adjustment is basically consistent with the frequency adjustment, the voltage variation range is less than 3%, and the ratio of the voltage to the rated voltage is within ±1% in the steady state, with good stability and low voltage static error.

[0158] Through correlation analysis, the correlation coefficient between the output power of each inverter after f0 and U0 adjustment and the output power without f0 and U0 adjustment was calculated, and the results are shown in Table 2. The values ​​are all greater than 0.99, which shows that there is a significant positive correlation between the inverter output power before and after adjustment.

[0159] Table 2 P, Q correlation analysis

[0160] <![CDATA[P1 cor ]]> <![CDATA[P2 cor ]]> <![CDATA[P3 cor ]]> 0.9955 0.9980 0.9975 <![CDATA[Q1 cor ]]> <![CDATA[Q2 cor ]]> <![CDATA[Q3 cor ]]> 0.9969 0.9978 0.9907

[0161] The correlation coefficient shows that: (1) the results after adjustment are highly consistent with those before adjustment, and the adjustment process has a low impact on each inverter, that is, the adjustment method has a high consistency for the inverter group; (2) the output power after adjustment maintains a similar trend to that before adjustment, and the adjustment method does not destroy the original power output characteristics, but optimizes them; (3) after adjustment, the inverter still retains the original output characteristics, which is conducive to maintaining the integrity and stability of the system.

[0162] The virtual synchronous generator control system based on the discontinuous control strategy described below and the virtual synchronous generator control method based on the discontinuous control strategy described above can be referred to each other.

[0163] Please refer to the attached Fig.12The present invention also provides a virtual synchronous generator control system based on a discontinuous control strategy, comprising:

[0164] Multiple parallel inverters 100, each inverter has a virtual moment of inertia J, a damping coefficient D, an active-frequency droop coefficient m, a reactive-voltage droop coefficient n, a line impedance X, and a rated output power P Ni ;

[0165] Monitoring module 200, used for real-time monitoring of the frequency and voltage of the microgrid;

[0166] The pre-synchronization control module 300 is used to calculate the pre-synchronization input quantity P before the new inverter is connected. com and Q com , and adjust the output frequency and voltage of the new inverter;

[0167] The adjustment module 400 is used to calculate and adjust the frequency adjustment coefficient f adj And the voltage regulation factor U adj And ensure the output power of each inverter is balanced;

[0168] The control module 500 adopts a discontinuous control strategy to ensure that f is recalculated and adjusted when frequency or voltage fluctuations are detected. adj and U adj , until the frequency or voltage fluctuation is lower than the threshold f thr , U thr .

[0169] The system of this embodiment can be used to execute the above method embodiments, and its principles and technical effects are similar, which will not be repeated here.

[0170] Please refer to the attached Fig.13 The present invention further provides a computer device 40, comprising: a processor 41 and a memory 42, wherein the memory 42 stores a computer program executable by the processor, and when the computer program is executed by the processor, the above method is executed.

[0171] The present invention further provides a storage medium 43 on which a computer program is stored. When the computer program is run by the processor 41, the above method is executed.

[0172] Among them, the storage medium 43 can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable red-only memory (PROM), read-only memory (ROM), magnetic storage, flash memory, disk or optical disk.

[0173] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A virtual synchronous generator control method based on a discontinuous control strategy, characterized in that: The following steps are involved: Initialize the virtual moment of inertia J, damping coefficient D, active-frequency droop coefficient m, reactive-voltage droop coefficient n, line impedance X and rated output power P of each inverter Ni ; Set the system reference frequency f ref and reference voltage U ref , where the reference angular frequency ω ref Defined as 2πf ref ; Before the new inverter is connected, the pre-synchronization input quantity P com and Q com Perform pre-synchronization control to synchronize the output frequency and voltage of the new inverter with the existing system; Monitor system frequency and voltage in real time, detect and calculate frequency deviation f e And voltage deviation U e ; When f e or U e Exceeding the preset threshold f thr , U thr When the frequency adjustment factor f is recalculated, the adjustment mechanism is started based on the discontinuous control strategy. adj And the voltage regulation factor U adj : Among them, k p is the proportionality coefficient, k i is the integral coefficient, P Ni is the rated output power of each inverter, t0 is the time when adjustment starts, C0 is the compensation constant, f e (τ) and U e (τ) are the frequency and voltage deviation at time τ, respectively; Dynamically adjust the output of each inverter according to the system load and operating conditions to adapt to different operating environments, maintain power balance and ensure that frequency and voltage are consistent with f ref and U ref Consistent.

2. The method according to claim 1, characterized in that: The initial value of the virtual moment of inertia J is set according to the following conditions: Among them, P max is the maximum output power of the inverter, ω is the angular velocity of the inverter, and dω / dt is the time derivative of the angular velocity of the inverter, that is, the angular acceleration.

3. The method according to claim 1, characterized in that: The initial value of the damping coefficient D is set according to the following conditions: Among them, ΔP max is the maximum allowable power variation, Δf max is the maximum frequency variation allowed.

4. The method according to claim 1, characterized in that: The initial values ​​of the active-frequency droop coefficient m and the reactive-voltage droop coefficient n are set according to the following conditions: Among them, f N is the nominal frequency of the system, U N is the nominal voltage of the system, S N is the rated capacity of the inverter.

5. The method according to claim 1, characterized in that: The frequency adjustment factor f adj And the voltage regulation factor U adj The calculation adopts the proportional integral controller, and its proportional coefficient k p and the integration coefficient k i Optimize based on real-time data.

6. The method according to claim 1, characterized in that: The threshold setting is dynamically adjusted according to the system load and operating conditions to adapt to different operating environments.

7. The control method according to claim 1, characterized in that: The pre-synchronization input quantity P com and Q com The setting is based on real-time monitoring data of the current system frequency and voltage to ensure a smooth transition when a new inverter is connected.

8. The method according to claim 1, characterized in that: The output of each inverter is adjusted to maintain power balance and ensure that the frequency and voltage are consistent with f ref and U ref The consistent step is to adopt a discontinuous control strategy. When the frequency or voltage fluctuation exceeds the threshold value f thr and U thr When f is recalculated and adjusted adj and U adj If the newly cut-in load or inverter capacity is not enough to cause the frequency and voltage fluctuations to reach the threshold value f thr , U thr , then f adj , U adj It will not enter into readjustment and will maintain the original parameters until the next event occurs.

9. A virtual synchronous generator control system based on a discontinuous control strategy, used to implement the method according to any one of claims 1 to 8, characterized in that: include: Multiple parallel inverters, each inverter has a virtual moment of inertia J, a damping coefficient D, an active-frequency droop coefficient m, a reactive-voltage droop coefficient n, a line impedance X, and a rated output power P Ni ; Monitoring module, used to monitor the frequency and voltage of the microgrid in real time; The pre-synchronization control module is used to calculate the pre-synchronization input quantity P before the new inverter is connected com and Q com , and adjust the output frequency and voltage of the new inverter; Adjustment module, used to calculate and adjust the frequency adjustment coefficient f adj And the voltage regulation factor U adj And ensure the output power of each inverter is balanced; The control module adopts a discontinuous control strategy to ensure that the adjustment f is recalculated and adjusted when frequency or voltage fluctuations are detected. adj and U adj , until the frequency or voltage fluctuation is lower than the threshold f thr , U thr .

10. A storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method according to any one of claims 1 to 7 is implemented.

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