Power control method and system for virtual synchronous converter

Abstract

The invention discloses a power control method and system of a virtual synchronous converter, and belongs to the technical field of power control of the virtual synchronous converter, and the method comprises the steps: collecting the per unit value of the grid-connected point voltage of the virtual synchronous converter, and obtaining a voltage state signal; calculating a first active amplitude limiting value, a second active amplitude limiting value and a third active amplitude limiting value according to the voltage state signal; taking the minimum value as an equivalent mechanical power amplitude limiting value Pm, and limiting a mechanical power reference value of the virtual synchronous converter by using the Pm to realize active power output constraint; the voltage state is judged according to the voltage state signal, and different control means are adopted based on different voltage states. According to the method, active and reactive collaborative optimization control during a voltage fault period can be realized, stable operation of the converter and a power grid is guaranteed, and meanwhile, the voltage supporting capability and the frequency stability during low voltage ride through are improved.

Description

Technical Field

[0001] This application belongs to the field of power control technology for virtual synchronous converters, and specifically relates to a power control method and system for virtual synchronous converters. Background Technology

[0002] A virtual synchronous converter is a power regulation device that simulates the inertia, damping characteristics, and droop regulation law of a synchronous generator through power electronic conversion technology. It is widely used in new energy grid connection, microgrids, and energy storage systems. It can achieve flexible allocation of active and reactive power and provide frequency support and voltage regulation capabilities for the power grid.

[0003] Existing virtual synchronous converters have the following issues during voltage faults: 1) Limitations of active power control, such as directly limiting the active power reference value to avoid power angle instability, but sacrificing the ability to support the frequency during faults, and some schemes rely only on current limiting without considering the power angle stabilization mechanism of the synchronous machine, which is prone to instability. 2) Disjointed reactive power control: For example, traditional virtual synchronous inverters passively switch to low voltage ride-through mode when the voltage drops, failing to fully utilize reactive power potential and lacking dynamic compensation capability during mild voltage drops, resulting in slow voltage recovery. 3) Lack of multi-constraint coordination: For example, existing technologies do not comprehensively consider multi-dimensional constraints such as power angle stability, AC current limiting, and battery management, making it difficult to achieve global optimization of power output. Summary of the Invention

[0004] To address the aforementioned issues, this application provides a power control method and system for a virtual synchronous converter. By utilizing a collaborative control mechanism that combines voltage state hierarchical detection, multi-dimensional active power dynamic limiting, and reactive power three-stage switching, the power output can be precisely adjusted under different operating conditions such as normal voltage, slight voltage drop, and deep voltage drop. This avoids power angle instability and equipment overload, while also quickly compensating for grid voltage and supporting system frequency, thus achieving globally optimized power control.

[0005] A power control method for a virtual synchronous converter includes: Collect the per-unit value Ug of the voltage at the grid connection point of the virtual synchronous converter, and obtain the voltage state signal based on Ug; Based on the voltage state signal, calculate the first active power limit, the second active power limit, and the third active power limit; take the minimum value as the equivalent mechanical power limit value Pm, and use Pm to limit the mechanical power reference value of the virtual synchronous converter to achieve active power output constraint; The voltage status is determined based on the voltage status signal. When the voltage is within the normal range, the reactive power reference value Q is generated by the droop characteristic of the virtual synchronous converter. ref The virtual synchronous converter is based on Q. refAdjust reactive power output; When the voltage drops to the range of slight voltage drop, the output ΔQ of the voltage error PI regulator is superimposed on the generated Qref, and ΔQ is used to compensate the grid voltage to restore it. When the voltage drops to the voltage drop depth range, the active current command Id is set to 0, and the reactive current command value Iq is linearly increased according to the voltage drop depth. The active current command Id and the reactive current command value Iq are used to regulate the inner loop current output of the virtual synchronous converter to support the grid voltage. The active power output of the virtual synchronous converter is constrained by the Pm, so as to realize reactive power support and active power coordination during the low voltage ride-through period.

[0006] Furthermore, The normal range is defined as: Ug ≥ the first preset threshold. The voltage drop range is defined as: second preset threshold ≤ Ug < first preset threshold; The voltage drop range is: Ug < second preset threshold; The second preset threshold is less than the first preset threshold.

[0007] Furthermore, The first active power limit value is the power angle stability limit value Plim1; Plim1=K(Ug) Prated Where K(Ug) is the static stability coefficient related to Ug, and Prated is the rated power of the virtual synchronous converter; The second active power limiting value is the AC current limiting value Plim2; Plim2=min(Ug,1) λove Prated Where λove is the transient overload capacity of the converter; The third active power limit value is the battery management limit value Plim3; Plim3=min(Ibat Vbat η,Pbat_max) Where Ibat is the real-time battery current, Vbat is the real-time battery voltage, η is the operating efficiency of the virtual synchronous converter, and Pbat_max is the maximum power that the battery is allowed to output.

[0008] Furthermore, When the voltage is within the normal range, the reactive power reference value Q ref satisfy:

[0009] in, This is the voltage reference value; The reference voltage; The real-time actual reactive power output value of the virtual synchronous converter; n is the dynamic adjustment coefficient. ; In the formula, n0 is the initial reference value of the dynamic adjustment coefficient; k is the attenuation rate coefficient.

[0010] Furthermore, The input of the voltage error PI regulator is the difference between the rated voltage of the virtual synchronous converter and Ug. ΔQ is the reactive power compensation amount after the difference is PI regulated. The corrected reactive power output target is obtained by superimposing ΔQ. The virtual synchronous converter outputs reactive power according to the corrected reactive power output target.

[0011] in, The proportional gain of the PI controller. The integral coefficient of the PI controller. For operator symbols, This is the voltage reference value. This is the per-unit value of the grid connection point voltage for the virtual synchronous converter.

[0012] Furthermore, The commanded value of the reactive current Iq does not exceed the preset upper limit of reactive current, and increases as Ug decreases.

[0013] Furthermore, The static stability coefficient K(Ug) is obtained by fitting a preset functional relationship.

[0014] Furthermore, When acquiring Ug, one or more of the following are monitored simultaneously: voltage phase jump and frequency change rate, which are combined with Ug to generate a voltage state signal.

[0015] A power control system for a virtual synchronous converter, comprising: The voltage fault detection module is used to collect the per-unit value Ug of the voltage at the grid connection point of the virtual synchronous converter and obtain the voltage status signal based on Ug; The multi-dimensional power limiting module is used to calculate the first active power limiting value, the second active power limiting value, and the third active power limiting value based on the voltage state signal; the minimum value is taken as the equivalent mechanical power limiting value Pm, and Pm is used to limit the mechanical power reference value of the virtual synchronous converter to achieve active power output constraint. The dynamic mode switching module is used to determine the voltage status based on the voltage status signal. When the voltage is within the normal range, a reactive power reference value Q is generated by the droop characteristic of the virtual synchronous converter.ref The virtual synchronous converter is based on Q. ref Adjust reactive power output; When the voltage drops to the range of slight voltage drop, the output ΔQ of the voltage error PI regulator is superimposed on the generated Qref, and ΔQ is used to compensate the grid voltage to restore it. When the voltage drops to the voltage drop depth range, the active current command Id is set to 0, and the reactive current command value Iq is linearly increased according to the voltage drop depth. The active current command Id and the reactive current command value Iq are used to regulate the inner loop current output of the virtual synchronous converter to support the grid voltage. The active power output of the virtual synchronous converter is constrained by the Pm, so as to realize reactive power support and active power coordination during the low voltage ride-through period.

[0016] Furthermore, In the multidimensional power limiting module, the first active power limiting value is the power angle stable limiting value Plim1; Plim1=K(Ug) Prated Where K(Ug) is the static stability coefficient related to Ug, and Prated is the rated power of the virtual synchronous converter; The second active power limiting value is the AC current limiting value Plim2; Plim2=min(Ug,1) λove Prated Where λove is the transient overload capacity of the converter; The third active power limit value is the battery management limit value Plim3; Plim3=min(Ibat Vbat η,Pbat_max) Where Ibat is the real-time battery current, Vbat is the real-time battery voltage, η is the operating efficiency of the virtual synchronous converter, and Pbat_max is the maximum power that the battery is allowed to output.

[0017] Compared with the prior art, this application has the following advantages: By constructing a three-dimensional dynamic active power limiting mechanism consisting of power angle stabilization, AC current, and battery management, and taking the minimum value as the final limit, the limitations of existing technologies that only consider a single constraint (such as power angle stabilization or current limiting) are overcome. This achieves global optimized allocation of active power under multi-dimensional safety constraints, fundamentally avoids power angle instability, and ensures the safe operation of the converter and battery body.

[0018] By introducing a three-stage dynamic switching control strategy for reactive power based on voltage drop depth, especially by adopting a voltage compensation mode with superimposed PI regulation during mild drops, the traditional solution's passive or insufficient reactive power support during mild faults is changed. It can actively and quickly compensate for voltage and accelerate system voltage recovery.

[0019] In the low-voltage ride-through mode with deep voltage dips, by blocking active current and maximizing reactive current, the active power output capability dynamically constrained by the multi-dimensional limiting module is retained. This achieves the coordination of reactive power support and limited active power support during low-voltage ride-through, solving the problem that traditional solutions completely sacrifice active power support to meet low-voltage ride-through requirements, thus leading to deterioration of system frequency stability.

[0020] Other features and advantages of this application will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the application. The objectives and other advantages of this application may be realized and obtained by means of the structures pointed out in the description, claims and drawings. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 A schematic diagram of the method of this disclosure is shown; Figure 2 A schematic diagram of the system disclosed herein is shown; Figure 3 A schematic diagram illustrating the cooperative function of the active power limiting module according to an embodiment of this disclosure is shown. Figure 4 A logic diagram for switching reactive power control modes according to an embodiment of this disclosure is shown; Figure 5 A schematic diagram of a piecewise linear function K(Ug) according to an embodiment of the present disclosure is shown. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0024] This disclosure provides a method for coordinated active and reactive power control and multi-dimensional dynamic limiting during voltage faults based on virtual synchronization mechanisms. This method is applied to the control system of a virtual synchronous converter, aiming to achieve coordinated optimization control of active and reactive power during grid voltage faults, and to ensure system stability and equipment safety.

[0025] 1. Structural composition and functions of the technical solution The control system disclosed herein mainly includes three core modules: a voltage fault detection module, a multi-dimensional power limiting module, and a dynamic mode switching module.

[0026] (1) Voltage fault detection module Function: Real-time monitoring of the per-unit voltage Ug at the grid connection point to determine the grid voltage status. By comparing Ug with preset voltage thresholds (such as 0.95 pu and 0.9 pu), it identifies whether a voltage drop has occurred and the depth of the drop, and generates corresponding fault flag signals. Connection relationship: The input of this module is the grid connection point voltage measurement value, and its output voltage status signal and fault flag are simultaneously provided to the multi-dimensional power limiting module and the dynamic mode switching module as the decision basis for the operation of these two modules.

[0027] (2) Multidimensional power limiting module Function: Based on the voltage status provided by the voltage fault detection module, dynamically calculate and constrain the upper limit of the active power output of the converter from three different dimensions to ensure the static stability of the system and the safety of the equipment during faults.

[0028] Connection: This module receives voltage signals from the voltage fault detection module. The outputs of its three internal sub-modules are fed into a minimum value selector, which ultimately outputs a comprehensive equivalent mechanical power limit value Pm, used to limit the mechanical power reference value in the virtual synchronous machine control loop.

[0029] Submodule composition: The power angle stabilization and limiting submodule: Based on the power angle stability equation of the synchronous motor, it constructs a static stability coefficient K(Ug) related to the voltage drop depth Ug, and calculates the first active power limit value Plim1=K(Ug). Prated ensures that the active power output of the converter is always below the static stability limit, thus avoiding power angle instability.

[0030] Where Prated is the rated power of the virtual synchronous converter. AC current limiting submodule: Combining the transient overload capacity λover of the converter and the current voltage level, calculate the second active power limiting value Plim2=min(Ug,1)·λover·Prated to prevent the AC side current of the converter from exceeding its maximum allowable value.

[0031] Battery management limiting submodule: Responds to the real-time status of the battery energy storage system and, considering the converter efficiency h, calculates the third active power limit: Plim3=min(Ibat Vbat η, Pbat_max) are used to avoid battery overload. Where Ibat is the real-time battery current, Vbat is the real-time battery voltage, η is the operating efficiency of the virtual synchronous converter, and Pbat_max is the maximum allowable output power of the battery.

[0032] (3) Dynamic mode switching module Function: Based on the voltage drop depth provided by the voltage fault detection module, the reactive power control strategy is seamlessly switched to achieve layered and precise support for the grid voltage.

[0033] Connection relationship: This module receives the voltage status signal from the voltage fault detection module and outputs the corresponding reactive current or voltage reference value command to the inner loop control circuit of the converter.

[0034] Control Mode: Reactive power priority mode: Activated when voltage is normal (Ug≥0.95 pu). In this mode, the reactive power reference value Q... ref This is caused by the drooping characteristic of virtual synchronizers, namely: The dynamic adjustment coefficient is: It can adaptively change to suppress oscillations. Among them, This is the voltage reference value; The reference voltage; The real-time actual reactive power output value of the virtual synchronous converter; n is the dynamic adjustment coefficient. In the formula, n0 is the initial reference value of the dynamic adjustment coefficient; k is the decay rate coefficient. Voltage compensation mode: Activated when the voltage drops slightly (0.9≤Ug<0.95pu). In this mode, a PI regulator for voltage error is superimposed on the reactive power priority mode. Its output provides additional correction to the reactive power reference value, i.e.: This is to actively compensate for the voltage and accelerate its recovery. Among them, The proportional gain of the PI controller. The integral coefficient of the PI controller. For operator symbols, This is the voltage reference value. This is the per-unit value of the grid connection point voltage for the virtual synchronous converter.

[0035] Low-voltage sag mode: Activated when the voltage depth drops (Ug < 0.9pu). In this mode, the control strategy switches to current control. The active current Id is set to 0, and the reactive current Iq is linearly increased according to the voltage sag depth, i.e., Iq = min(1.05IN, kq(1-Ug)), but the upper limit does not exceed 1.05 times the rated current IN. At this time, the active power output is strictly constrained by the multi-dimensional power limiting module. kq is the reactive current compensation coefficient.

[0036] 2. Description of the implementation scheme and working principle with reference to the attached diagram. 1) Overall workflow (combined with...) Figure 2 System control block diagram): The system continuously monitors the grid connection voltage Ug through the voltage fault detection module. Once Ug is detected to be below 0.95pu, the multi-dimensional power limiting module is immediately activated. This module's three sub-modules calculate their respective limiting values ​​in parallel, ultimately taking the minimum value to obtain Pm, which dynamically limits the power command of the virtual synchronous machine. Simultaneously, the dynamic mode switching module switches between three reactive power control modes based on the precise value of Ug, achieving optimized reactive power control.

[0037] 2) Working principle of the multi-dimensional power limiting module (combined with...) Figure 3 , Figure 5 ): Power angle stabilization limiting: The power angle stabilization limiting submodule queries a preset piecewise linear function K(Ug) based on the detected Ug (its curve is shown in Figure 1). Figure 5 As shown in the figure, after the voltage falls below the start-up threshold Ustart, the value of K decreases as the voltage decreases, reflecting the decrease in the static stability limit. Then, Plim1=K(Ug) is calculated. This fundamentally guarantees synchronization stability during faults, compared to the simplistic and crude limitation of active power or consideration of only current in existing technologies.

[0038] AC current limiting: The AC current limiting submodule calculates Plim2=min(Ug,1). λove Prated. This formula takes into account the direct impact of voltage dips on the maximum output active power, ensuring that the AC side current of the converter will not exceed its transient overcurrent capacity under any voltage conditions, effectively preventing overcurrent damage.

[0039] Battery management limiting: The battery management limiting submodule uses Plim3=min(Ibat) to limit the battery speed. Vbat The calculation is performed using η and Pbat_max. It directly maps the real-time constraints on the battery side to the AC power output of the converter, solving the problem that the dynamic constraints of the DC side energy source are often ignored in existing technologies.

[0040] These three limiting values ​​compete for the minimum value, achieving globally optimal active power allocation under the triple constraints of power angle stability, converter safety, and battery management. This collaborative optimization capability is not available in existing technologies.

[0041] 3) Working principle of the dynamic mode switching module (combined with...) Figure 4 ): Mode switching logic: The module automatically switches according to the range where Ug is located, such as... Figure 4 The logic flowchart is shown below.

[0042] Differences and advantages compared to existing technologies: In voltage compensation mode, this disclosure does not passively wait for voltage recovery, but actively injects compensatory reactive power into the grid through a PI regulator. This can quickly raise the voltage during a slight voltage drop, making up for the shortcomings of traditional virtual synchronous machines in terms of insufficient dynamic response in this scenario.

[0043] In the low-voltage ride-through coordinated mode, this disclosure does not simply completely cut off active power or fix the current distribution. On the one hand, it prioritizes maximizing reactive current output to support the voltage; on the other hand, its active power output is dynamically constrained by the aforementioned multi-dimensional power limiting module Pm. This means that within the safety limits of the equipment, it can still provide a certain amount of active power to support the frequency, achieving coordination between "low-voltage ride-through" and "active power support," breaking through the dilemma of traditional solutions that cannot balance both.

[0044] 3. The following is a power control method for a virtual synchronous converter based on the above system, such as... Figure 1 As shown, it includes: Collect the per-unit value Ug of the voltage at the grid connection point of the virtual synchronous converter, and obtain the voltage state signal based on Ug; Based on the voltage state signal, calculate the first active power limit, the second active power limit, and the third active power limit; take the minimum value as the equivalent mechanical power limit value Pm, and use Pm to limit the mechanical power reference value of the virtual synchronous converter to achieve active power output constraint; The voltage status is determined based on the voltage status signal. When the voltage is within the normal range, the reactive power reference value Q is generated by the droop characteristic of the virtual synchronous converter. ref The virtual synchronous converter is based on Q. ref Adjust reactive power output; When the voltage drops below the first threshold, in the generated Q refBased on this, the output ΔQ of the voltage error PI regulator is superimposed, and ΔQ is used to compensate the grid voltage to restore it; When the voltage drops below the second threshold, the active current command Id is set to 0, and the reactive current command value Iq is linearly increased according to the voltage drop depth. The active current command Id and the reactive current command value Iq are used to regulate the inner loop current output of the virtual synchronous converter to support the grid voltage. The active power output of the virtual synchronous converter is constrained by the Pm, so as to realize reactive power support and active power coordination during the low voltage ride-through period. The second threshold is less than the first threshold.

[0045] The following are embodiments of this disclosure: Taking a power plant as an example, when Ug = 0.92pu (slight voltage drop), the system enters voltage compensation mode and limits Pm to 0.75MW through multi-dimensional limiting (determined by the most stringent power angle stability limit). Simultaneously, the PI regulator operates, restoring the voltage to 0.95pu within 10 seconds. When Ug = 0.7pu (deep voltage drop), the system switches to low-voltage recovery mode, outputting the maximum reactive current (1.05pu), while the active power is limited to 0.3MW (determined by the power angle stability limit). This process fully demonstrates the core advantages of active and reactive power coordination and multi-dimensional constraint protection, ultimately achieving a 35% reduction in frequency deviation and a 40% reduction in voltage recovery time.

[0046] Alternative solutions: 1) Alternative solution for voltage fault detection module: In addition to monitoring voltage amplitude, voltage phase transitions, frequency change rates, or combinations thereof can be introduced as supplementary fault criteria. The fault detection threshold can be dynamically adjusted based on specific power grid standards or application scenarios, rather than being a fixed value. Delayed acknowledgment or hysteresis comparison logic can be introduced to prevent malfunctions caused by transient disturbances and improve detection reliability.

[0047] 2) Alternatives to the multi-dimensional power limiting module: In the power angle stabilization limiting submodule, the function form of the stability coefficient is not limited to piecewise linear; a smooth curve function can be used for fitting, or dynamic limiting can be performed based on the real-time calculated power angle margin. In the AC current limiting submodule, in addition to considering transient overload capacity, a converter thermal accumulation model can be introduced to dynamically adjust the limiting value according to the operating temperature. In the battery management limiting submodule, in addition to real-time power, the battery's remaining capacity, health status, or temperature can be used as constraints to dynamically adjust the power upper limit. Taking the minimum value of the outputs of the three submodules is a preferred method; weighted averaging or other fusion logic can also be used to synthesize the final active power limiting value. Additional limiting submodules can be added; for example, limiting based on grid frequency deviation can be introduced to participate in adjusting active power when the frequency is abnormal.

[0048] 3) Alternative solution for the dynamic mode switching module: The voltage threshold for mode switching can be adaptively adjusted based on the grid strength or the real-time operating status of the system.

[0049] In reactive power priority mode, the adaptive variation law of the dynamic adjustment coefficient is not limited to a specific mathematical form; lookup table methods or other adaptive methods can be used. In voltage compensation mode, the controller used to generate reactive power compensation is not limited to a PI regulator; other types of regulators or control algorithms can be used. In low-voltage switching coordination mode, the active current command does not necessarily have to be set to zero; non-zero commands can be dynamically generated according to actual conditions. The generation strategy of reactive current command is not limited to linear increase; other nonlinear allocation strategies can be used.

[0050] 4) Alternatives to the overall architecture and implementation: The functions of each module described in this disclosure can be implemented through hardware circuits, software programs, or a combination of hardware and software. The control method can be applied to different types of grid-connected converters, including but not limited to energy storage converters and photovoltaic inverters.

[0051] In summary, this disclosure provides an active-reactive power coordinated control and multi-dimensional dynamic limiting system based on virtual synchronization mechanism during voltage faults. Through a voltage fault detection module, a multi-dimensional power limiting module, and a dynamic mode switching module, it achieves coordinated optimization of active and reactive power. This not only avoids power angle instability, AC current and battery current overload, but also prioritizes reactive power compensation to stabilize grid voltage, enhances the dual support of grid frequency and voltage, improves system transient stability, and reduces frequency deviation and voltage recovery time.

[0052] Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A power control method for a virtual synchronous converter, characterized in that, include: Collect the per-unit value Ug of the voltage at the grid connection point of the virtual synchronous converter, and obtain the voltage state signal based on Ug; Based on the voltage state signal, calculate the first active power limit, the second active power limit, and the third active power limit; take the minimum value as the equivalent mechanical power limit value Pm, and use Pm to limit the mechanical power reference value of the virtual synchronous converter to achieve active power output constraint; The voltage status is determined based on the voltage status signal. When the voltage is within the normal range, the reactive power reference value Q is generated by the droop characteristic of the virtual synchronous converter. ref The virtual synchronous converter is based on Q. ref Adjust reactive power output; When the voltage drops to the range of slight voltage drops, the generated Q ref Based on this, the output ΔQ of the voltage error PI regulator is superimposed, and ΔQ is used to compensate the grid voltage to restore it; When the voltage drops to the voltage drop depth range, the active current command Id is set to 0, and the reactive current command value Iq is linearly increased according to the voltage drop depth. The active current command Id and the reactive current command value Iq are used to regulate the inner loop current output of the virtual synchronous converter to support the grid voltage. The active power output of the virtual synchronous converter is constrained by the Pm, so as to realize reactive power support and active power coordination during the low voltage ride-through period.

2. The power control method for a virtual synchronous converter according to claim 1, characterized in that, The normal range is defined as: Ug ≥ the first preset threshold. The voltage drop range is defined as: second preset threshold ≤ Ug < first preset threshold; The voltage drop range is: Ug < second preset threshold; The second preset threshold is less than the first preset threshold.

3. The power control method for a virtual synchronous converter according to claim 1, characterized in that, The first active power limit value is the power angle stability limit value Plim1; Plim1=K(And) Prated Where K(Ug) is the static stability coefficient related to Ug, and Prated is the rated power of the virtual synchronous converter; The second active power limiting value is the AC current limiting value Plim2; Plim2=min(Ug,1) love Prated Where λove is the transient overload capacity of the converter; The third active power limit value is the battery management limit value Plim3; Plim3=min(Ibat Vbat (the,Pbat_max) Where Ibat is the real-time battery current, Vbat is the real-time battery voltage, η is the operating efficiency of the virtual synchronous converter, and Pbat_max is the maximum power that the battery is allowed to output.

4. The power control method for a virtual synchronous converter according to claim 1, characterized in that, When the voltage is within the normal range, the reactive power reference value Q ref satisfy: in, This is the voltage reference value; The reference voltage; The real-time actual reactive power output value of the virtual synchronous converter; n is the dynamic adjustment coefficient. ; In the formula, n0 is the initial reference value of the dynamic adjustment coefficient; k is the attenuation rate coefficient.

5. The power control method for a virtual synchronous converter according to claim 1, characterized in that, The input of the voltage error PI regulator is the difference between the rated voltage of the virtual synchronous converter and Ug. ΔQ is the reactive power compensation amount after the difference is PI regulated. The corrected reactive power output target is obtained by superimposing ΔQ. The virtual synchronous converter outputs reactive power according to the corrected reactive power output target. in, The proportional gain of the PI controller. The integral coefficient of the PI controller. For operator symbols, This is the voltage reference value. This is the per-unit value of the grid connection point voltage for the virtual synchronous converter.

6. The power control method for a virtual synchronous converter according to claim 1, characterized in that, The commanded value of the reactive current Iq does not exceed the preset upper limit of reactive current, and increases as Ug decreases.

7. The power control method for a virtual synchronous converter according to claim 3, characterized in that, The static stability coefficient K ( U g) Obtained by fitting a pre-defined functional relationship.

8. The power control method for a virtual synchronous converter according to claim 1, characterized in that, When acquiring Ug, one or more of the following are monitored simultaneously: voltage phase jump and frequency change rate, which are combined with Ug to generate a voltage state signal.

9. A power control system for a virtual synchronous converter, characterized in that, include: The voltage fault detection module is used to collect the per-unit value Ug of the voltage at the grid connection point of the virtual synchronous converter and obtain the voltage status signal based on Ug; The multi-dimensional power limiting module is used to calculate the first active power limiting value, the second active power limiting value, and the third active power limiting value based on the voltage state signal; the minimum value is taken as the equivalent mechanical power limiting value Pm, and Pm is used to limit the mechanical power reference value of the virtual synchronous converter to achieve active power output constraint. The dynamic mode switching module is used to determine the voltage status based on the voltage status signal. When the voltage is within the normal range, a reactive power reference value Q is generated by the droop characteristic of the virtual synchronous converter. ref The virtual synchronous converter is based on Q. ref Adjust reactive power output; When the voltage drops to the range of slight voltage drop, the output ΔQ of the voltage error PI regulator is superimposed on the generated Qref, and ΔQ is used to compensate the grid voltage to restore it. When the voltage drops to the voltage drop depth range, the active current command Id is set to 0, and the reactive current command value Iq is linearly increased according to the voltage drop depth. The active current command Id and the reactive current command value Iq are used to regulate the inner loop current output of the virtual synchronous converter to support the grid voltage. The active power output of the virtual synchronous converter is constrained by the Pm, so as to realize reactive power support and active power coordination during the low voltage ride-through period.

10. The power control system for the virtual synchronous converter according to claim 9, characterized in that, In the multidimensional power limiting module, the first active power limiting value is the power angle stable limiting value Plim1; Plim1=K(And) Prated Where K(Ug) is the static stability coefficient related to Ug, and Prated is the rated power of the virtual synchronous converter; The second active power limiting value is the AC current limiting value Plim2; Plim2=min(Ug,1) love Prated Where λove is the transient overload capacity of the converter; The third active power limit value is the battery management limit value Plim3; Plim3=min(Ibat Vbat (the,Pbat_max) Where Ibat is the real-time battery current, Vbat is the real-time battery voltage, η is the operating efficiency of the virtual synchronous converter, and Pbat_max is the maximum power that the battery is allowed to output.

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