A virtual synchronous generator system based on a network-forming converter

Abstract

The application relates to the technical field of virtual synchronous generators (VSG), and particularly discloses a virtual synchronous generator system based on a network-constructing converter, which comprises a power supply U dc , a capacitor C dc , a three-phase bridge inverter and an LC filter connected in sequence, and further comprises a power calculation module, a VSG control module and a PSWM modulation module. The VSG control module uses a VSG control equation to obtain a reference voltage E according to instantaneous active power P and reactive power Q, in combination with a VSG given reactive power Q ref , an instruction value U ref of a VSG output voltage effective value and a reference active power P ref , and further obtains the reference voltage E according to a reference voltage comprehensive calculation formula. The system takes a virtual synchronous generator as a main research object, designs a new control strategy, provides inertia and damping of a synchronous generator, can maximally compensate for the performance of the SG, provides voltage support and inertia support characteristics, improves the anti-interference and robustness of the system, and has wide development and application prospects.

Description

Technical Field

[0001] This invention relates to the field of virtual synchronous generator (VSG) technology, and more particularly to a virtual synchronous generator system based on a grid-type converter. Background Technology

[0002] With the increasing scarcity of non-renewable resources, developing new energy power generation methods such as wind power and photovoltaics has become an inevitable trend. Therefore, microgrid systems, centered on new energy power generation and grid-connected converters, have become a hot topic in the power system. Traditional converters have relatively fast response times, but their ability to suppress disturbances in the power grid is poor, failing to effectively stabilize the system. Power grid stability relies heavily on synchronous generators (SGs), whose inertia and damping contribute to maintaining grid stability. Microgrids cannot provide the high damping and high rotational inertia of SGs, posing a significant threat to system stability.

[0003] Synchronous generators are the main generating units in power networks, and their damping and inertia play a significant role in supporting system stability. Furthermore, with speed governors and excitation control, they can effectively adjust frequency and voltage regulation. With the integration of large amounts of wind and solar power into the system, the characteristics of the power grid structure and control mechanisms will inevitably undergo changes. Power systems are gradually developing towards a higher proportion of new energy sources and power electronic equipment systems. However, currently, most new energy generation is connected to the grid through converters, and the capacity of new energy units is constantly increasing. Converter control uses control algorithms rather than physical characteristics. Its response speed is faster and its controllability is better than that of synchronous generators. However, the low interface damping and low inertia of converters can negatively impact system stability, and their limited frequency and voltage regulation capabilities can affect the stability of microgrid systems.

[0004] The higher the penetration rate of new energy power generation, the higher the proportion of converters, which leads to a significant reduction in system inertia and a decrease in frequency quality. Summary of the Invention

[0005] This invention provides a virtual synchronous generator system based on a grid-type converter. The technical problem it solves is that the higher the penetration rate of new energy power generation, the higher the proportion of converters, which leads to a significant reduction in system inertia and a decrease in frequency quality.

[0006] To address the above technical problems, this invention provides a virtual synchronous generator system based on a grid-connected converter, comprising sequentially connected power supplies U dc Capacitor C dc The system includes a three-phase bridge inverter, an LC filter, a power calculation module, a VSG control module, and a PSWM modulation module; the power calculation module is used to calculate the instantaneous active power P and reactive power Q of the three-phase bridge inverter based on the output voltage and output current of the three-phase bridge inverter.

[0007] The VSG control module is used to determine the instantaneous active power P and reactive power Q, in conjunction with the reactive power Q given by the VSG. ref The instruction value U of the VSG output voltage RMS value ref Reference active power P ref The amplitude E of the reference voltage E is obtained using the VSG control equation. m And the phase angle δ, and further calculate the reference voltage E according to the comprehensive calculation formula of the reference voltage;

[0008] The PSWM modulation module is used to calculate the reference current based on the reference voltage E through voltage and current loop control, and to track the reference current to output the final reference modulation voltage wave applied to the three-phase bridge inverter.

[0009] Specifically, the amplitude E of the reference voltage E is obtained in the VSG control equation. m The formula is expressed as follows:

[0010]

[0011] Where, k u k is the voltage regulation coefficient. q Here, E0 is the reactive power regulation coefficient, E0 is the effective value of the grid voltage, ΔE is the reactive power given by VSG, U is the effective value of the output voltage of the three-phase bridge inverter, and ΔE is the reactive power regulation coefficient. U Indicates the voltage regulation value, ΔE Q This indicates the reactive power adjustment value.

[0012] Specifically, the comprehensive calculation formula for the reference voltage is expressed as follows:

[0013]

[0014] e a e b e c This represents the three-phase voltage of the reference voltage E.

[0015] Specifically, the formula for obtaining the phase angle δ of the reference voltage E in the VSG control equation is expressed as follows:

[0016]

[0017] Where J is the inertia coefficient; D is the virtual damping coefficient corresponding to the damping torque; ω0 is the VSG rated angular velocity in rad / s, and ω is the instantaneous angular velocity of the virtual rotor; T m T e T d These are the mechanical, electromagnetic, and damping torques of the VSG, respectively, and P is the instantaneous output power of the VSG.

[0018] Specifically, the voltage and current loop control includes an outer voltage loop control and an inner current loop control;

[0019] The voltage outer loop control specifically involves: taking the difference between the grid connection point voltage and the reference voltage E, and then passing it through a virtual impedance circuit to obtain the three-phase grid connection reference current;

[0020] The current inner loop control specifically involves outputting the final reference modulation voltage wave by passing the three-phase grid-connected reference current through the current inner loop controller.

[0021] Specifically, the current inner loop controller adopts a PR controller.

[0022] Specifically, the LC filter includes a-phase inductor L1, b-phase inductor L2, and c-phase inductor L3 connected in series in the circuit, and also includes a-phase capacitor C1, b-phase capacitor C2, and c-phase capacitor C3 connected in parallel in the circuit.

[0023] Specifically, let C1 = C2 = C3 = C, the transfer function of the PR controller is expressed as follows:

[0024]

[0025] Among them, K C This represents the current loop control coefficient. U represents the transfer function of the three-phase bridge inverter. in The voltage amplitude of the triangular carrier wave output by the three-phase bridge inverter is represented by s, where s represents the Laplace operator.

[0026] Specifically, the PSWM modulation module uses SVPWM modulation to modulate the reference current.

[0027] This invention provides a virtual synchronous generator system based on a grid-type converter. Taking the virtual synchronous generator as the main research object, a new control strategy is designed to combine the grid-type converter with the control strategy. This control provides the inertia and damping of the synchronous generator, which can maximize the performance compensation of the SG, provide voltage support and inertia support characteristics, improve the anti-interference and robustness of the system, and has broad development and application prospects. Attached Figure Description

[0028] Figure 1 This is a topology diagram of a virtual synchronous generator system based on a grid-type converter provided in an embodiment of the present invention;

[0029] Figure 2 This is a waveform diagram of the output active power under steady state provided in an embodiment of the present invention;

[0030] Figure 3This is a waveform diagram of the output angular frequency under steady state provided in an embodiment of the present invention;

[0031] Figure 4 This is a steady-state output voltage waveform diagram provided in an embodiment of the present invention;

[0032] Figure 5 This is a steady-state output current waveform diagram provided in an embodiment of the present invention;

[0033] Figure 6 This is a diagram showing the percentage of fundamental harmonics under steady-state conditions provided in an embodiment of the present invention.

[0034] Figure 7 This is the output active power waveform diagram of a 5kW load being cut off in 0.5s, provided in an embodiment of the present invention.

[0035] Figure 8 This is a waveform diagram of the output reactive power when a 5kW load is cut off in 0.5s, provided in an embodiment of the present invention.

[0036] Figure 9 This is an angular frequency waveform diagram of a 5kW load being cut off in 0.5s, provided in an embodiment of the present invention.

[0037] Figure 10 This is a diagram showing the percentage of fundamental harmonics when a 5kW load is cut off in 0.5s, provided in an embodiment of the present invention.

[0038] Figure 11 This is the output active power waveform diagram provided by an embodiment of the present invention, showing a step increase in power value to 8kW in 0.5s;

[0039] Figure 12 This is an angular frequency waveform diagram of the power value stepping to 8kW in 0.5s, provided by an embodiment of the present invention;

[0040] Figure 13 This is an example of the output voltage waveform diagram provided by an embodiment of the present invention, showing a step increase in power value to 8kW in 0.5s.

[0041] Figure 14 This is the output current waveform diagram provided by an embodiment of the present invention, showing a step increase in power value to 8kW in 0.5s;

[0042] Figure 15 This is a diagram showing the percentage of fundamental harmonics when the power value jumps to 8kW in 0.5s, as provided in an embodiment of the present invention.

[0043] Figure 16 This is the waveform diagram of the output active power when a 3kW active load is applied in 0.5s, provided by an embodiment of the present invention.

[0044] Figure 17 This is a waveform diagram of the output reactive power when a 3kW active load is applied in 0.5s, as provided in an embodiment of the present invention.

[0045] Figure 18 This is the angular frequency waveform diagram of a 3kW active load being applied in 0.5s, provided in an embodiment of the present invention.

[0046] Figure 19 This is an angular frequency waveform diagram provided in an embodiment of the present invention when 3000Var is applied;

[0047] Figure 20 This is a waveform diagram of the output reactive power when 3000Var is applied, provided in an embodiment of the present invention.

[0048] Figure 21 This is a diagram showing the percentage of fundamental harmonics when 3000Var is applied, provided in an embodiment of the present invention.

[0049] Figure 22 This is the output voltage waveform diagram provided in the embodiment of the present invention when 3000Var is applied;

[0050] Figure 23 This is the output current waveform diagram provided in the embodiment of the present invention when 3000Var is applied;

[0051] Figure 24 This is a waveform diagram of the active power output during constant D time provided in an embodiment of the present invention;

[0052] Figure 25 This is a waveform diagram of the reactive power output during constant D time provided in an embodiment of the present invention;

[0053] Figure 26 This is an angular frequency waveform diagram of constant D provided in an embodiment of the present invention;

[0054] Figure 27 This is a waveform diagram of the constant J output active power provided in an embodiment of the present invention;

[0055] Figure 28 This is the angular frequency waveform diagram under constant J provided in the embodiment of the present invention. Detailed Implementation

[0056] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. The embodiments are given for illustrative purposes only and should not be construed as limiting the present invention. The accompanying drawings are for reference and illustration only and do not constitute a limitation on the scope of patent protection of the present invention, because many changes can be made to the present invention without departing from the spirit and scope of the present invention.

[0057] Virtual synchronous generator (VSG) technology simulates the operating characteristics of a synchronous generator, essentially combining conventional inverter hardware structure with VSG control methods. Although the core concepts of VSG control differ significantly from PQ or Vf control, the inverter main circuit upon which these control strategies rely can adopt the same topology. For example... Figure 1 The diagram shows the main circuit topology of a virtual synchronous generator, which is also the main circuit topology of a virtual synchronous generator system based on a grid-type converter provided in this embodiment of the invention. It includes sequentially connected power supplies U... dc Capacitor C dc The system includes a three-phase bridge inverter, an LC filter, a power calculation module, a VSG control module, and a PSWM modulation module. The LC filter includes a-phase inductors L1, L2, and L3 connected in series in the circuit, and a-phase capacitors C1, C2, and C3 connected in parallel in the circuit.

[0058] The power calculation module is used to calculate the instantaneous active power P and reactive power Q of the three-phase bridge inverter based on the output voltage (three-phase voltage) and output current (three-phase current) of the three-phase bridge inverter.

[0059] The VSG control module is used to determine the instantaneous active power P and reactive power Q, in conjunction with the reactive power Q given by VSG. ref The instruction value U of the VSG output voltage RMS value ref Reference active power P ref The amplitude E of the reference voltage E is obtained using the VSG control equation. m And the phase angle δ, and then the reference voltage E is calculated based on the comprehensive calculation formula of the reference voltage.

[0060] The PSWM modulation module is used to determine the reference current based on the reference voltage E through voltage and current loop control, and to track the reference current to output the final reference modulation voltage wave that acts on the three-phase bridge inverter.

[0061] To improve the system's anti-interference and robustness, this invention improves the control strategy, which is reflected in three aspects: VSG control equation, reference voltage comprehensive calculation formula, and voltage-current loop control.

[0062] The VSG's active-frequency controller provides the phase angle (phase angle δ) of the reference voltage, while the reactive-voltage controller provides the amplitude (E) of the reference voltage. m The reference voltage E of VSG is obtained from the comprehensive calculation formula of the reference voltage.

[0063] The amplitude E of the reference voltage E is obtained in the VSG control equation. m The formula is expressed as follows:

[0064]

[0065] Where, k u k is the voltage regulation coefficient. q E0 is the reactive power regulation coefficient, U is the effective value of the grid voltage, and ΔE is the true value of the effective output voltage of the three-phase bridge inverter. U Indicates the voltage regulation value, ΔE Q This indicates the reactive power adjustment value.

[0066] The formula for obtaining the phase angle δ of the reference voltage E in the VSG control equations is expressed as follows:

[0067]

[0068] Where J is the inertia coefficient; D is the virtual damping coefficient corresponding to the damping torque; ω0 is the VSG rated angular velocity in rad / s, and ω is the instantaneous angular velocity of the virtual rotor; T m T e T d These are the mechanical, electromagnetic, and damping torques of the VSG, respectively, and P is the instantaneous output power of the VSG.

[0069] Finally, the formula for calculating the reference voltage is expressed as follows:

[0070]

[0071] e a e b e c This represents the three-phase voltage of the reference voltage E.

[0072] Voltage and current loop control includes voltage outer loop control and current inner loop control.

[0073] The outer loop voltage control specifically involves: taking the difference between the grid connection point voltage and the reference voltage E, and then passing it through a virtual impedance circuit to obtain the three-phase grid connection reference current;

[0074] The current inner loop control specifically involves passing the three-phase grid-connected reference current through the current inner loop controller to output the final reference modulation voltage wave.

[0075] In this example, the inner current loop controller uses a PR controller. Let C1 = C2 = C3 = C, the transfer function of the PR controller is designed as follows:

[0076]

[0077] Among them, K C This represents the current loop control coefficient. U represents the transfer function of a three-phase bridge inverter. in represents the voltage amplitude of the triangular carrier wave output by the three-phase bridge inverter, and s represents the Laplace operator.

[0078] The system is set to operate at a constant reference power, with a given active power of 10kW, a given reactive power of 0, and a reference frequency f of 50Hz. The following simulation studies investigate the system's operation under different conditions.

[0079] The VSG strategy was simulated within 0–1 s. The steady-state system output power and output angular frequency were obtained without any added disturbance, as shown below. Figure 2 , Figure 3 As shown. From Figure 2 It can be seen that the system output power gradually reaches a stable value of 10kW after 0.201s, at which point the output tracks the input value. Figure 3 It can be seen that the system output angular frequency reaches a stable value after 0.216s, and the value reaches a steady state at 314.15 (rad / s).

[0080] Figure 4 , Figure 5 The following are waveforms of the system output voltage and current under VSG control. It can be seen that both the output voltage and output current are sinusoidal waves with the same phase.

[0081] Figure 6 The graph showing the percentage change of the fundamental harmonic frequency of the system shows that the grid-connected current distortion rate is 1.62%, which meets the requirements for grid-connected synchronization.

[0082] Figures 2-6 This demonstrates that under steady-state conditions, the system quickly reaches a stable state and easily meets the requirements, proving the reliability of the virtual synchronous generator strategy under normal circumstances. The transient processes under other operating conditions will be studied and analyzed below.

[0083] Set up a simulation condition under power disturbance, initially setting the power to 10kW. Disconnect a 5kW load in 0.5s and observe the simulated active power waveform output. Figure 7 As shown. Figure 7 The waveform observed shows that under a large disturbance such as the instantaneous removal of half the load, the output active power drops rapidly after the load is removed in 0.5s, reaching the overshoot peak at 0.603s, and then stabilizing at the given input value in 0.682s. From 0s to 0.2s, the VSG output active power rises to 10kW according to the given value, and after a transient process of 0.5s to 0.69s, it reaches 5kW after the load removal, and then maintains the given steady-state output. The active power overshoot is 5.25%, and the angular frequency overshoot is 0.33%. Both the voltage and current outputs before and after the disturbance are sinusoidal waves. Figure 10 As shown, the system's grid current distortion rate is 3.21%, which meets the national standard requirements.

[0084] After the load is removed in 0.5 seconds, through Figure 8 As expected, reactive power increases due to the decrease in active power, reaching a steady state in 0.615s. According to the principles of motor drive, frequency and speed are linearly related. Changes in speed affect the generator's torque balance, which is in turn influenced by the input mechanical power and output electromagnetic power. When active power decreases, the frequency therefore decreases, such as... Figure 9 As shown, the system recovered to a stable state after 0.615s.

[0085] The simulation is set up with a power disturbance, initially set to 10kW, and then the power value jumps to 8kW in 0.5s. The active power and angular frequency waveforms of the simulation are observed, as shown below. Figure 11 , Figure 12 As shown. The waveforms of the system's output voltage and load current are respectively shown in the figure. Figure 13 , 14 As shown.

[0086] like Figure 11 As shown, when a 2kW load is instantaneously removed, the waveform shows that after 0.5s of load removal, the output active power drops rapidly, reaching the overshoot peak at 0.603s, and then the output stabilizes at the given input value. From 0s to 0.2s, the VSG output active power rises to 10kW according to the given value. After a transient process of 0.5s to 0.7s, it reaches 8kW after the load removal, and then maintains the given steady-state output. The active power overshoot is 2.5%, and the angular frequency overshoot is 0.14%.

[0087] Figure 12 same Figure 9 When active power decreases, both rotational speed and angular frequency decrease. Compared to... Figure 9 In this operating condition with smaller disturbances, the overshoot peak appears earlier, and the system stabilizes earlier as well. Under these circumstances, the system is more stable.

[0088] like Figure 13 , Figure 14 As shown, both the voltage and current outputs before and after the disturbance are sinusoidal waves with consistent phase.

[0089] like Figure 15 As shown, the system's grid current distortion rate is 2.07%, which meets the national standard requirements.

[0090] Set up the simulation conditions, initially setting the power to 10kW. Apply a 3kW active load at 0.5s and observe the simulated waveform output. The corresponding active power, reactive power, and angular frequency waveforms are as follows: Figure 16 , Figure 17 , Figure 18As shown, from 0s to 0.2s, the active power output of VSG rises to 10kW according to the given input, with an overshoot of 9%. At 0.5s, a 3kW active load is applied, and after a transient process of 0.15s, it reaches the given input of 13kW. Subsequently, it maintains the given steady-state output with an overshoot of 2.8% and an angular frequency overshoot of 0.2%. Before and after the disturbance, both the voltage and current outputs are sinusoidal waves with consistent phase.

[0091] To verify whether the QV characteristics of the constructed VSG model can achieve the expected goals, the verification is now carried out on a single-machine infinite bus system. During the simulation system, only load 1 is connected within the time period of 0s to 0.3s, and its reactive power is set to 5000Var; at t=0.3s, load 2 is connected, and its reactive power is Q=3000Var; the load connection process is completed instantaneously. Figure 19 The waveform of the angular frequency when 3000Var is applied. Figure 20 The waveform diagram of reactive power when 3000Var is applied. Figure 21 A graph showing the percentage of fundamental harmonic frequencies when 3000Var is applied. Figure 22 The output voltage waveform is shown when 3000Var is applied. Figure 23 The output current waveform is shown when 3000Var is applied.

[0092] from Figures 19-23 As can be seen, before the first load switch, the rated power of the VSG output load was 5000Var, consistent with the given power. After 0.3s of simulation, the reactive power Q of the VSG output gradually increased, reaching 8000Var at 0.5s, essentially consistent with the given power. It then remained stable. Both the voltage and current outputs before and after the disturbance were sinusoidal and in phase. The grid current distortion rate was 1.54%, meeting national standards.

[0093] This section extends the simulation using the constructed active and reactive power modules. Finally, the simulation results verify the impact of active and reactive power characteristics, as well as the magnitude of rotational inertia, on the frequency regulation characteristics of the VSG control system. This intuitively demonstrates the feasibility of the designed VSG algorithm for inverter system control. As can be seen above, under VSG control, the system can quickly recover to a new steady state after a disturbance, verifying the good disturbance rejection and robustness of the VSG control strategy.

[0094] Next, we will analyze the impact of the inertia damping coefficient on the system output.

[0095] When the damping coefficient is constant at D = 10 and the inertia coefficient J is changed from 0.2 to 0.05, the corresponding active power waveform is as follows: Figure 24 As shown, the reactive power waveform is as follows: Figure 25 As shown, the angular frequency waveform is as follows Figure 26 As shown. From Figure 24 It can be seen that the active power fluctuation and active power overshoot peak value are highest when J=0.5, while the active power fluctuation and overshoot peak value are low when J=0.05, and J=0.2 is in the middle. (Observation) Figure 25 The reactive power fluctuation and overshoot were highest at J=0.5, while the reactive power and overshoot peak fluctuations were lowest at J=0.05, with J=0.2 falling in the middle. (Observation) Figure 26 The angular frequency fluctuation and overshoot are highest when J = 0.05, while the angular frequency and overshoot peak fluctuation are lowest when J = 0.5, with J = 0.2 being in the middle. This shows that when the damping coefficient D is constant, for the same change in active power, the lower the value of the moment of inertia J, the slower the frequency change; the larger the value of J, the faster the frequency change. From the above results, it can be seen that the frequency change is directly related to the magnitude of the moment of inertia. By choosing an appropriate J, the system's frequency output can be stabilized, thus accurately reflecting the medium-to-large inertia characteristics of the VSG control system.

[0096] Next, we will analyze the transient synchronization characteristics of the variable damping coefficient D.

[0097] To verify the effect of the damping coefficient on the system output, the moment of inertia coefficient was kept constant at J = 0.2, and the damping coefficient D ranged from 10 to 20. The system output was observed, and the corresponding active power and angular frequency output waveforms are shown below. Figure 27 , Figure 28 As shown.

[0098] observe Figure 27 The active power output waveforms shown have the highest ripple and overshoot for the waveform with D=10, the lowest for D=20, and D=15 is in the middle. As for the time to reach stability, the waveform with D=10 takes the longest, the waveform with D=20 takes the shortest, and D=15 is in the middle.

[0099] observe Figure 28 As shown in the angular frequency output waveform, the angular frequency is positively correlated with the rotational speed and active power. It is worth noting that when D = 10, the fluctuations in active power and angular frequency are already large. Therefore, the fluctuations will cause losses for the system, and a larger damping coefficient should be selected.

[0100] As the damping coefficient increases, the system's volatility decreases, and the time to reach stability becomes shorter. When the moment of inertia J remains constant, an increase in the damping coefficient D reduces the system's active power overshoot and accelerates the oscillation decay rate. Analysis of the VSG leads to the following conclusions: the oscillation frequency of the VSG during active power response is determined by the VSG's rotational inertia J, while the damping coefficient D is the primary factor determining its oscillation decay rate.

[0101] This embodiment uses modeling and simulation analysis to obtain the influence of the moment of inertia J on the oscillation frequency of the VSG output power. The damping coefficient D has a significant impact on the output power oscillation decay rate. Furthermore, this simulation simulated power surges and instantaneous switching of active and reactive power. The simulation results all meet national standards, and the output voltage and current waveforms are both sinusoidal with consistent phase. According to the national standard GB / 14549-1993, the voltage harmonic distortion rate should be controlled within 5%. The current harmonic distortion rate varies depending on the harmonic order. Generally, the 5th harmonic current is less than 62A, and the 7th harmonic current is less than 32A; therefore, the harmonic current distortion rate should also be controlled within 5%. For high-voltage grids above 10KV, the harmonic requirement is even higher, not exceeding 4%. In the simulation, the highest current distortion rate was 3.21%, all meeting national standards. This design introduces the mechanical equations of the synchronous generator into the converter control, realizing the simulation of the converter's characteristics for synchronous machine inertia, damping, voltage regulation, and frequency regulation. This VSG control improves the system's anti-interference and robustness, reduces the system's active power overshoot, and accelerates the oscillation decay rate.

[0102] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A virtual synchronous generator system based on a grid-connected converter, comprising sequentially connected power supplies. ,capacitance The system includes a three-phase bridge inverter, an LC filter, a power calculation module, a VSG control module, and a PSWM modulation module; the power calculation module is used to calculate the instantaneous active power P and reactive power Q of the three-phase bridge inverter based on the output voltage and output current of the three-phase bridge inverter; characterized in that: The VSG control module is used to determine the instantaneous active power P and reactive power Q, in conjunction with the reactive power given by the VSG. Command value of VSG output voltage RMS value Reference active power The amplitude of the reference voltage E is determined using the VSG control equations. and phase angle The reference voltage E is then calculated using the comprehensive formula for the reference voltage. The PSWM modulation module is used to calculate the reference current based on the reference voltage E through voltage and current loop control, and to track the reference current to output the final reference modulation voltage wave applied to the three-phase bridge inverter. The amplitude of the reference voltage E is determined in the VSG control equation. The formula is expressed as follows: ， in, This is the voltage regulation coefficient. This is the reactive power regulation coefficient. Here, represents the effective value of the grid voltage, and represents the reactive power given by the VSG. The effective value of the output voltage of the three-phase bridge inverter is given. Indicates the voltage adjustment value. Indicates the reactive power adjustment value; The voltage and current loop control includes an outer voltage loop control and an inner current loop control. The voltage outer loop control specifically involves: taking the difference between the grid connection point voltage and the reference voltage E, and then passing it through a virtual impedance circuit to obtain the three-phase grid connection reference current; The current inner loop control specifically involves: passing the three-phase grid-connected reference current through the current inner loop controller to output the final reference modulation voltage wave; The current inner loop controller uses a PR controller.

2. The virtual synchronous generator system based on a grid-type converter according to claim 1, characterized in that, The comprehensive calculation formula for the reference voltage is expressed as follows: ， , , This represents the three-phase voltage of the reference voltage E.

3. A virtual synchronous generator system based on a grid-type converter according to claim 1, characterized in that, The phase angle for obtaining the reference voltage E in the VSG control equations The formula is expressed as follows: ， Where J is the inertia coefficient; D is the virtual damping coefficient corresponding to the damping torque; The rated angular velocity of the VSG is expressed in rad / s. It is the instantaneous angular velocity of the virtual rotor. , These are the mechanical, electromagnetic, and damping torques of the VSG. It is the instantaneous output power of the VSG.

4. A virtual synchronous generator system based on a grid-type converter according to claim 1, characterized in that, The LC filter includes a-phase inductor L1, b-phase inductor L2, and c-phase inductor L3 connected in series in the circuit, and also includes a-phase capacitor C1, b-phase capacitor C2, and c-phase capacitor C3 connected in parallel in the circuit.

5. A virtual synchronous generator system based on a grid-type converter according to claim 4, characterized in that, Let C1=C2=C3=C, the transfer function of the PR controller is expressed as follows: ， in, This represents the current loop control coefficient. This represents the transfer function of a three-phase bridge inverter. This indicates the voltage amplitude of the triangular carrier wave output by the three-phase bridge inverter. This represents the Laplace operator.

6. A virtual synchronous generator system based on a grid-type converter according to claim 1, characterized in that: The PSWM modulation module uses SVPWM modulation to modulate the reference current.

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