A method, medium and device for power equalization control of a VSG frequency modulation channel

Abstract

The application discloses a VSG primary frequency modulation channel power equalization control method, medium and equipment, and relates to the technical field of inverters. The method comprises the following steps: collecting the local output active power and the local frequency of each VSG; calculating the local capacity occupancy rate, and constructing the primary frequency modulation coefficient of the load-throwing increase channel and the primary frequency modulation coefficient of the load-cutting decrease channel; identifying the load-throwing event or the load-cutting event according to the change rate of the local frequency, and calling the corresponding primary frequency modulation coefficient; in response to the triggering of the load-throwing event or the load-cutting event, recording the current event frequency and the primary frequency modulation power increment, and combining the called primary frequency modulation coefficient to generate the incremental primary frequency modulation power instruction. The medium and the equipment are used for implementing the above method. The application has the beneficial effects that: through the constructed primary frequency modulation coefficient, the capacity occupancy rate difference of each VSG changes in the decreasing direction in each load switching process, and the power equalization control of each VSG under the condition of no communication is realized.

Description

Technical Field

[0001] This application relates to the field of inverter technology, and in particular to a power sharing control method, medium and device for the primary frequency modulation channel of a VSG. Background Technology

[0002] Virtual Synchronous Generator (VSG) control technology, by simulating the rotor motion equations and electromagnetic transient characteristics of traditional synchronous generators, endows grid-connected inverters with inertial and damping support capabilities, and has become an important means to improve the frequency stability and power quality of microgrids. With the increasing penetration rate of distributed power sources, parallel operation of multiple VSGs has become a common networking configuration in microgrids. In multi-VSG parallel systems, how to achieve a reasonable distribution of load power among the VSGs is one of the core issues ensuring stable system operation. Existing technologies offer various methods for addressing the power distribution problem of multi-VSG parallel systems.

[0003] In one existing approach, a small-signal model of multiple VSGs operating in parallel can be established to obtain the transmission relationship between the output power of each VSG and the load power. Then, the control parameters of each VSG are determined based on parameter matching constraints to achieve reasonable power allocation during multi-unit parallel operation. This approach mainly relies on the small-signal model of the parallel system and parameter matching relationships, and belongs to a power allocation method based on parameter tuning. It is difficult to directly achieve the control effect of reducing the amount of power generated by high-occupancy VSGs during load commissioning and reducing the amount of power generated by high-occupancy VSGs during load shedding.

[0004] In another existing scheme, the VSG-based active-frequency control strategy exhibits droop characteristics in steady state. By setting an equivalent droop coefficient inversely proportional to the inverter capacity, active power of parallel inverters is allocated proportionally to capacity. Simultaneously, a distributed consensus algorithm is used to adjust the droop curve bias, achieving reactive power per-unit convergence. This scheme primarily achieves active power proportional allocation through the static matching relationship between the equivalent droop coefficient and capacity, and its power allocation pattern is essentially fixed after design. However, if the initial state differs due to current limiting or power commands, or if the actual available capacity decreases due to insufficient photovoltaic output, only capacity-based allocation of newly generated power can be achieved; the capacity-based power allocation relationship cannot be reconstructed.

[0005] Furthermore, existing primary frequency regulation control typically employs a single primary frequency regulation coefficient. Even in schemes that use variable primary frequency regulation coefficients, the changes are often based on state variables such as current available capacity, energy storage state of charge, operating margin, or frequency deviation. Essentially, this still generates a uniform primary frequency regulation coefficient at a specific moment. This coefficient applies to both the power generation and reduction processes simultaneously, without setting different frequency regulation coefficients for the power generation demand during frequency decreases and the power generation reduction demand during frequency increases. Therefore, in existing schemes, the same equipment often uses the same primary frequency regulation response strength during power generation and reduction, failing to achieve the asymmetrical control logic of reducing power generation of high-occupancy equipment during load commissioning and reducing power generation of high-occupancy equipment during load shedding. Summary of the Invention

[0006] One objective of this application is to provide a power sharing control method for the primary frequency modulation channel of a VSG that can solve at least one of the defects in the aforementioned background art.

[0007] Another object of this application is to provide a computer-readable storage medium capable of implementing a VSG primary frequency modulation channel power equalization control method that solves at least one of the defects in the above-mentioned background art.

[0008] Another object of this application is to provide an electronic device capable of implementing a VSG primary frequency modulation channel power equalization control method that solves at least one of the defects in the above-mentioned background art.

[0009] To achieve at least one of the above objectives, one aspect of this application provides a power sharing control method for primary frequency regulation channels of a VSG, applied to a multi-VSG parallel system, comprising the following steps: acquiring the local output active power and local frequency of each VSG; calculating the local capacity occupancy rate based on the local output active power, and constructing a primary frequency regulation coefficient for the load-increasing channel that decreases as the local capacity occupancy rate increases, and a primary frequency regulation coefficient for the load-canceling channel that increases as the local capacity occupancy rate increases; identifying a load-in event or a load-canceling event based on the rate of change of the local frequency, and calling the corresponding primary frequency regulation coefficient; responding to the triggering of a load-in event or a load-canceling event, acquiring the current event frequency and the primary frequency regulation power increment, and generating an incremental primary frequency regulation power command by combining the called primary frequency regulation coefficient; and superimposing the incremental primary frequency regulation power command onto the local active power reference to form an active power command for control.

[0010] Preferably, the primary frequency modulation coefficients corresponding to the load-increasing and load-reducing channels are related to the local capacity utilization rate by one or more combinations of linear, power, exponential, logarithmic, or S-shaped functions.

[0011] Preferably, the primary frequency modulation coefficients corresponding to the load-increasing and load-reducing channels are related to the local capacity utilization rate by a power function, and the specific calculation expressions are as follows: ; ; In the formula, This represents the primary frequency modulation coefficient of the additional transmission channel. This represents the primary frequency modulation coefficient of the load shedding and power reduction channel. This represents the lower limit of the primary frequency modulation coefficient. This represents the upper limit of the frequency modulation coefficient, and r represents the local machine's capacity utilization rate. This represents the nonlinear adjustment index.

[0012] Preferably, the upper limit of the primary frequency modulation coefficient corresponding to each VSG. and the lower limit of the primary frequency modulation coefficient It is directly proportional to the maximum power output of each VSG.

[0013] Preferably, the rate of change of the local frequency is negative when the system is loaded and positive when the system is unloaded. The process of identifying loading or unloading events based on the rate of change of the local frequency is as follows: a trigger threshold is set. When the rate of change of the local frequency is less than the negative trigger threshold, the system is determined to trigger a loading event. When the rate of change of the local frequency is greater than the positive trigger threshold, the system is determined to trigger a unloading event.

[0014] Preferably, when the system triggers a load-on event or a load-off event, the corresponding incremental primary frequency regulation power command is generated in the following ways: ; ; In the formula, and These represent the incremental primary frequency modulation power commands corresponding to the load activation and load deactivation events, respectively. This represents the frequency modulation power increment when the event is triggered. and These represent the primary frequency modulation coefficients for the load-increasing transmission channel and the load-reducing transmission channel, respectively. Indicates the frequency of events when an event is triggered. This indicates the local frequency.

[0015] Preferably, when the system triggers a load-up event, it switches to the load-up transmission channel; when the system triggers a load-cutting event, it switches to the load-cutting transmission reduction channel; after a valid event is identified and the corresponding channel switch is completed, the system enters a lockout state that prohibits channel switching; when the system enters a steady-state range based on the duration of the lockout state and / or the rate of change of the local frequency, the lockout state is released, allowing the system to switch channels again; otherwise, the lockout state is maintained.

[0016] Preferably, the determination of whether the system has entered the steady-state region includes the following process: setting a latching time threshold and a steady-state enable threshold, wherein the steady-state enable threshold is less than the trigger threshold; when the difference between the current time and the trigger time of the last valid event is greater than the latching time threshold, and the absolute value of the rate of change of the local frequency is less than the steady-state enable threshold, the system is determined to have entered the steady-state region.

[0017] Another aspect of this application provides a computer-readable storage medium storing a computer program; when the computer program is executed by a processor, it implements the above-described VSG primary frequency modulation channel power sharing control method.

[0018] Another aspect of this application provides an electronic device, including a processor and a memory; the memory is used to store a computer program, and the processor is used to execute the computer program to implement the above-described VSG primary frequency modulation channel power sharing control method.

[0019] Compared with the prior art, the beneficial effects of this application are as follows: (1) This application constructs the primary frequency modulation coefficients of the load-increasing transmission channel and the load-reducing transmission channel respectively, so that the high capacity utilization rate VSG increases transmission less when loading and reduces transmission more when shunting, and the low capacity utilization rate VSG increases transmission more when loading and reduces transmission less when shunting. Thus, the capacity utilization rate difference of each VSG changes in the direction of decreasing during each load switching process. When the capacity utilization rate of each VSG has become consistent, the subsequent load switching can still maintain the consistent capacity utilization rate, realizing the power distribution control of different capacity VSGs according to the highest available capacity ratio under the condition of no communication.

[0020] (2) This application adopts event-incremental power regulation. When a load or load shedding event is detected, the local frequency and the primary frequency modulation power increment at the moment the event is triggered are recorded. Subsequent power regulation is based on the change of the current frequency relative to the frequency at the moment the event is triggered, rather than the absolute deviation relative to the rated frequency. This effectively avoids the problem that traditional variable droop control may cause high occupancy rate VSG reverse generation when the frequency is rising but still lower than the rated frequency during the load shedding process.

[0021] (3) This application does not rely on the communication link. Each VSG can complete the control based only on its own output active power, local frequency, local frequency change rate and current power output, thus avoiding the impact of communication delay, packet loss and link failure on system performance and reducing system complexity and construction cost. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the traditional VSG control architecture.

[0023] Figure 2 This is a schematic diagram of the working steps of this application.

[0024] Figure 3 This is a schematic diagram of the VSG control architecture of this application.

[0025] Figure 4 This is a schematic diagram of the control logic of the primary frequency modulation power module in this application.

[0026] Figure 5 This is a schematic diagram illustrating the specific process of the blocking re-enabling mechanism for channel switching in this application.

[0027] Figure 6 This is a schematic diagram of the simulation results of this application. Detailed Implementation

[0028] The present application will now be further described in conjunction with specific embodiments. It should be noted that, in the description of this specification, the use of terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicates that the specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms should not be construed as necessarily referring to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0029] In the description of this application, it should be noted that the terms "center", "lateral", "longitudinal", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., which indicate the orientation and positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and should not be construed as limiting the specific protection scope of this application.

[0030] It should be noted that the terms "first," "second," etc., in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0031] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0032] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0033] The terms “comprising” and “having”, and any variations thereof, in the specification and claims of this application are intended to cover non-exclusive inclusion, for example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or device.

[0034] To facilitate understanding of the technical solution of this application, the traditional VSG control process with primary frequency modulation will be described in detail below.

[0035] It is important to know that, such as Figure 1 As shown, the traditional VSG control architecture simulates the rotor motion equation and excitation regulation characteristics of a synchronous generator, enabling the inverter to possess inertial response, primary frequency regulation, and damping support capabilities. The entire control process is divided into two relatively independent parts: an active power control loop and a reactive power control loop. These are ultimately synthesized into a three-phase voltage drive signal, which is then modulated by SVPWM to control the inverter's switching transistors.

[0036] Specifically, such as Figure 1 As shown, first collect the three-phase output voltage U of the inverter.o and three-phase output current I o According to the collected voltage U o and current I o Calculate instantaneous active power P o and instantaneous reactive power Q o The calculated power values ​​are fed into the active power control loop and the reactive power control loop, respectively. The reactive power control loop performs reactive power-voltage droop control; the active power control loop is the core of VSG control and is used to simulate the rotor motion characteristics of a synchronous generator.

[0037] In the reactive power control loop, based on the effective value U of the generator terminal voltage n With the inverter's three-phase output voltage U o The difference is expressed by the droop coefficient k. v It can generate reactive power regulation; the obtained reactive power regulation is compared with the rated reactive power reference value Q. ref The reactive power reference value Q* is obtained by superimposing the reactive power reference value Q* with the instantaneous reactive power Q. o Perform difference calculation to obtain reactive power deviation. Reactive power deviation is calculated using an integrator. The process yields the potential correction E. The integrator's transfer function is 1 / Ks, where K represents the reciprocal of the integral gain and s represents the Laplace operator.

[0038] The active control loop includes a frequency modulation stage and an inertia and damping stage, which are performed sequentially.

[0039] In a single frequency modulation cycle, the rated angular frequency ω is first calculated. n (i.e., the grid angular frequency) and the virtual angular frequency ω at the current moment o The deviation, the obtained deviation ω is obtained through the first frequency modulation coefficient k f The primary frequency modulation power increment P was calculated. ω After completing one frequency cycle, the resulting primary frequency modulation power increment P will be... ω With a given active reference power P ref The active power reference value P* for primary frequency regulation is obtained by superimposing the values; the active power reference value P* for primary frequency regulation is then compared with the instantaneous active power P. o The difference is calculated to obtain the active power command P after the first frequency modulation correction. set That is, virtual mechanical power instruction P m The initial value; the obtained active power command P set After 1 / ω n After conversion, the virtual mechanical torque command T is obtained. m It serves as the input for inertia and damping.

[0040] In the inertia and damping process, the obtained virtual mechanical torque command T m After feedback closed-loop control using the damping coefficient D and the integrator, the virtual angular frequency deviation is obtained. ω o The transfer function of the integrator is 1 / Js, where J represents the moment of inertia and s represents the Laplace operator; the resulting virtual angular frequency deviation is... ω o With the angular frequency ω of the quota n By superimposing the values, we obtain the virtual angular frequency ω at the next moment. o The virtual angular frequency ω at the next moment o After processing by the integrator, the output voltage phase of the VSG, i.e., the power angle θ, is obtained; where the transfer function of the integrator is 1 / s, and s represents the Laplace operator.

[0041] Finally, the power angle θ obtained from active power control and the potential correction E obtained from reactive power control are passed through current-voltage closed-loop control and then through space vector pulse width modulation (SVPWM) to generate the PWM signal for controlling the inverter switching transistors.

[0042] Based on the above traditional VSG control process, it can be seen that in the primary frequency regulation stage of the active power control loop, the primary frequency regulation coefficient k f The value is fixed, meaning that the primary frequency regulation coefficient k remains constant regardless of whether the system is under load or not. f The values ​​are all the same. This means that in a multi-VSG parallel system, when the frequency decreases, all VSGs increase power generation according to the same rule; when the frequency increases, all VSGs decrease power generation according to the same rule; when the actual usable capacity of a certain VSG decreases due to reasons such as a decrease in photovoltaic output or a low energy storage SOC, its frequency regulation participation cannot be automatically reduced.

[0043] To address the shortcomings of traditional VSG control, one aspect of this application provides a power-sharing control method for the primary frequency modulation channel of a VSG, applicable to a multi-VSG parallel system. For example... Figure 2 As shown, one preferred embodiment includes the following steps: S100: Collects the local output active power and local frequency of each VSG.

[0044] It should be understood that the output voltage and current are collected in real time by voltage and current sensors set at the VSG output terminal. After analog-to-digital conversion, the collected voltage and current signals are sent to a digital signal processor or microcontroller for active power calculation, thus obtaining the VSG's local output active power, i.e., the instantaneous active power P. o .

[0045] Local frequency f oThrough the virtual angular frequency ω of VSG o The calculation yields the following expression: f o =ω o / 2π; where the virtual angular frequency ω o The frequency signal generated internally by the VSG control algorithm can be obtained through a phase-locked loop or directly from the VSG active power loop.

[0046] S200: Calculate the local capacity utilization rate based on the local active power output, and construct the primary frequency regulation coefficient of the load-increasing transmission channel that decreases as the local capacity utilization rate increases, and the primary frequency regulation coefficient of the load-cutting and transmission-reducing channel that increases as the local capacity utilization rate increases.

[0047] It should be understood that the local capacity utilization rate *r* is used to characterize the proportion of capacity currently used by the VSG, reflecting its remaining issuance margin and current issuance reduction space. From the definition of local capacity utilization rate *r*, we know that: the larger the local capacity utilization rate *r*, the higher the capacity utilization rate of the VSG, the smaller its remaining issuance margin, but the larger its current issuance reduction space; conversely, the smaller the local capacity utilization rate *r*, the lower the capacity utilization rate of the VSG, the larger its remaining issuance margin, but the smaller its current issuance reduction space.

[0048] In this step, the primary frequency modulation coefficients for the load-increasing transmission channel and the load-reducing transmission channel are constructed using the aforementioned capacity utilization rate *r*. Specifically, the primary frequency modulation coefficient for the load-increasing transmission channel decreases as the local capacity utilization rate *r* increases, resulting in VSGs with higher capacity utilization rates transmitting less power during load activation. Conversely, the primary frequency modulation coefficient for the load-reducing transmission channel increases as the local capacity utilization rate *r* increases, resulting in VSGs with higher capacity utilization rates reducing power transmission more during load shedding. This achieves a capacity utilization-balanced power redistribution during load disturbances.

[0049] S300: Identifies load activation or load deactivation events based on the rate of change of the local frequency and calls the corresponding primary frequency modulation coefficient.

[0050] It should be understood that whether power should be increased or decreased depends on whether the frequency is decreasing or increasing, rather than simply on whether the current frequency is below the rated frequency. Therefore, this application uses the rate of change of the local frequency as the basis for identifying the direction of disturbance. Specifically, the reason for using the rate of change of the local frequency to identify the direction of disturbance is as follows: when the system is loaded, the load suddenly increases, and the VSG output power is insufficient to meet the load demand, causing the frequency to decrease, at which point the rate of change of frequency is negative; when the system is unloaded, the load suddenly decreases, and the VSG output power exceeds the load demand, causing the frequency to increase, at which point the rate of change of frequency is positive.

[0051] S400: In response to the triggering of a load-on event or a load-off event, obtain the current event frequency and primary frequency modulation power increment, and generate an incremental primary frequency modulation power command by combining the called primary frequency modulation coefficient.

[0052] It's important to understand that recording the primary frequency regulation power increment at the moment the event is triggered in this step means recording and maintaining the active power command output in step S500 at the current moment as the primary frequency regulation power increment. In other words, it records the power value that the primary frequency regulation channel has already output to the VSG active power loop at the time the event occurs. The purpose of recording this value is to serve as the starting reference value for subsequent incremental power regulation, ensuring that the power command remains continuous and without jumps during channel switching.

[0053] S500: The incremental primary frequency regulation power command is superimposed on the local active power reference to form an active power command for control.

[0054] It should be understood that the local active power reference is the active power reference given in the active power control loop. The local active power reference and the incremental primary frequency regulation power command are superimposed to obtain the primary frequency regulation active power reference value. The difference between the primary frequency regulation active power reference value and the local output active power is calculated to obtain the primary frequency regulation corrected active power command. This active power command is used for subsequent VSG active power loop control. Specifically, this active power command serves as the input to the inertia and damping stage of the VSG active power control loop. After passing through the inertia and damping stage, a virtual angular frequency and virtual phase are generated. Combined with the voltage amplitude command generated by the reactive power loop, they jointly generate the VSG PWM modulation wave to control the on / off switching of power switching devices in the inverter. Since this step is a conventional technique in the field of VSG control technology, those skilled in the art can implement it based on existing technology, so it will not be elaborated here.

[0055] Understandably, this application constructs primary frequency modulation coefficients for the load-increasing transmission channel and the load-out decreasing transmission channel respectively, so that high-capacity-occupancy VSGs increase transmission less during load-in and decrease transmission more during load-out, while low-capacity-occupancy VSGs increase transmission more during load-in and decrease transmission less during load-out. This causes the capacity occupancy difference of each VSG to decrease during each load switching process. When the capacity occupancy of each VSG has become consistent, subsequent load switching can still maintain a consistent capacity occupancy, realizing power distribution control of VSGs of different capacities according to the highest available capacity ratio under no-communication conditions.

[0056] Meanwhile, this application adopts event-incremental power regulation, which records the local frequency and primary frequency modulation power increment at the moment the event is triggered when a load or load shedding event is detected. Subsequent power regulation is based on the change of the current frequency relative to the frequency at the moment the event is triggered, rather than the absolute deviation relative to the rated frequency. This effectively avoids the problem that traditional variable droop control may cause high occupancy VSG reverse power generation when the frequency is rising but still below the rated frequency during the load shedding process.

[0057] Furthermore, this application does not rely on communication links. Each VSG can complete control based solely on its own output active power, local frequency, local frequency change rate, and current available power, thus avoiding the impact of communication delays, packet loss, and link failures on system performance and reducing system complexity and construction costs.

[0058] To further facilitate understanding of the technical solution of this application, the technical solution of this application will be described below from the perspective of VSG control architecture.

[0059] Specifically, such as Figure 3 As shown, the improvement of the VSG control architecture corresponding to the technical solution of this application compared with the traditional VSG control architecture lies in: improving the primary frequency modulation stage of the traditional VSG control into a variable primary frequency modulation control stage, that is, designing a primary frequency modulation power module in the variable primary frequency modulation control stage; the input of this module is the local frequency f. o and the active power output P of this machine o .

[0060] like Figure 4 As shown, in the primary frequency modulation power module, the input local output active power P is used to... o Combined with the machine's maximum power output P M Calculate the local capacity utilization rate r; based on the obtained local capacity utilization rate r, calculate the primary frequency modulation coefficient of the additional transmission channel. The primary frequency modulation coefficient of the load shedding and power reduction channel .

[0061] Meanwhile, in the primary frequency modulation power module, based on the input local frequency f o The system performs ROCOF (Rate of Change of Frequency) calculation and inputs the calculated ROCOF to the channel switching module for enable output based on disturbance direction identification. When the disturbance direction of the system is identified as loading based on the ROCOF, enable M=1 can be output; when the disturbance direction of the system is identified as unloading based on the ROCOF, enable M=0 can be output.

[0062] When the enable M=1 output by the channel switching module, the primary frequency modulation power module selects to activate the additional transmission channel, thus increasing the primary frequency modulation coefficient. As the output K of the primary frequency modulation power modulep Similarly, when the enable M output by the channel switching module is 0, the primary frequency modulation power module selects the load-cutting and power-reducing channel, thus reducing the primary frequency modulation coefficient. As the output K of the primary frequency modulation power module p .

[0063] In a specific embodiment, when performing step S200, the local capacity utilization rate r can be determined by the local output active power P. o With the highest power output P of this machine M The ratio is calculated as r = P. o / P M Among them, the highest power output of this machine is P. M The maximum power output of the VSG is determined by a combination of factors, including its rated hardware capacity, current available DC-side power, energy storage state of charge, system operating strategy, and equipment temperature. Specifically, when the DC side of the VSG is a photovoltaic power generation system, the maximum power output P of the unit is... M Limited by the current light intensity and the output power of the photovoltaic array; when the DC side is an energy storage system, the maximum power output of this unit is P. M Limited by the state of charge and maximum discharge current of the energy storage battery; when the equipment temperature is too high, the maximum power output P of this unit is limited. M It may also be subject to derating limitations imposed by thermal management strategies.

[0064] In a specific embodiment, when performing step S200, when constructing the primary frequency modulation coefficients corresponding to the load-up transmission channel and the load-cutting transmission channel based on the obtained local capacity occupancy rate r, there are multiple functional relationships between the local capacity occupancy rate r and the primary frequency modulation coefficients corresponding to the load-up transmission channel and the load-cutting transmission channel, which will be described in detail below through several examples.

[0065] In a specific example, the primary frequency modulation coefficient of the boost channel is used. The primary frequency modulation coefficient of the load shedding and power reduction channel All of these relationships exhibit a linear functional relationship with the local machine's capacity utilization rate, r. It's understandable that there are multiple possible linear functional expressions; for ease of understanding, we will describe one such expression below. The specific expression is as follows: ; .

[0066] In the formula, This represents the lower limit of the primary frequency modulation coefficient. This indicates the upper limit of the primary frequency modulation coefficient.

[0067] In another specific example, the primary frequency modulation coefficient of the additional transmission channel is loaded. The primary frequency modulation coefficient of the load shedding and power reduction channel All of these relationships exhibit a power function relationship with the local machine's capacity utilization rate, r. It's understandable that there are multiple specific power function expressions; for ease of understanding, we will describe one such expression below. The specific expression is as follows: ; .

[0068] In the formula, This represents the lower limit of the primary frequency modulation coefficient. This indicates the upper limit of the primary frequency modulation coefficient. This represents the nonlinear adjustment index. The specific value can be determined by those skilled in the art based on their actual needs, for example, a value of 0.5 to 3.

[0069] In another specific example, the primary frequency modulation coefficient of the additional transmission channel is loaded. The primary frequency modulation coefficient of the load shedding and power reduction channel All of these relationships exhibit an exponential function relationship with the local machine's capacity utilization rate, r. It's understandable that there are multiple specific exponential function expressions; for ease of understanding, one such expression will be described below: ; .

[0070] In the formula, This represents the lower limit of the primary frequency modulation coefficient. λ represents the upper limit of the primary frequency modulation coefficient, and λ represents the exponential coefficient. The specific value can be determined by those skilled in the art based on their actual needs, for example, a value of 0.5 to 2.

[0071] In another specific example, the primary frequency modulation coefficient of the additional transmission channel is loaded. The primary frequency modulation coefficient of the load shedding and power reduction channel All of these relationships exhibit a logarithmic function relationship with the local machine's capacity utilization rate, r. It's understandable that there are multiple specific logarithmic function expressions; for ease of understanding, we will describe one such expression below. The specific expression is as follows: ; .

[0072] In the formula, This represents the lower limit of the primary frequency modulation coefficient. This represents the upper limit of the primary frequency modulation coefficient, and α represents the logarithmic adjustment coefficient. The specific value can be determined by those skilled in the art based on their actual needs, for example, a value of 0.5 to 1.

[0073] In another specific example, the primary frequency modulation coefficient of the additional transmission channel is loaded. The primary frequency modulation coefficient of the load shedding and power reduction channel All of these relationships exhibit an S-shaped functional relationship with the local capacity utilization rate (r). It's understandable that there are multiple specific S-shaped functional expressions; for ease of understanding, one such expression will be used below: ; .

[0074] In the formula, This represents the lower limit of the primary frequency modulation coefficient. This represents the upper limit of the primary frequency modulation coefficient, and β represents the steepness coefficient, which is used to control the steepness of the curve. This indicates the inflection point of the machine's capacity utilization rate, which is usually taken as 0.5.

[0075] It should be noted that linear function relationships have the advantages of being simple to calculate and easy to implement in engineering, making them suitable for applications where high control precision is not required.

[0076] The frequency modulation coefficient K is determined based on the power function relationship. p When calculating, the primary frequency modulation coefficient K p The nonlinear adjustment index varies with the change in the unit's capacity utilization rate. Different values ​​can cover different application scenarios. For example, when the nonlinear adjustment index... When the value of is greater than 1, the primary frequency modulation coefficient K is... p The frequency modulation coefficient K changes non-linearly and accelerates with the change in local capacity utilization rate; that is, when the local capacity utilization rate deviates from the equilibrium point, the primary frequency modulation coefficient K... p The changes are more drastic, which helps to accelerate the convergence speed of power averaging, making it suitable for applications with high dynamic response requirements. When the nonlinear adjustment index... When the value of is less than 1 and greater than 0, the primary frequency modulation coefficient K is... p The change in machine capacity utilization is relatively rapid in the initial stage and tends to level off in the later stage, making it suitable for occasions where high steady-state accuracy is required and overshoot needs to be avoided.

[0077] The exponential function relationship allows the primary frequency modulation coefficient K to be... p The capacity utilization rate changes drastically when the machine is close to saturation, making it suitable for applications with high overload protection requirements.

[0078] The logarithmic function relationship can make the first frequency modulation coefficient K p It changes rapidly when the local capacity utilization is low and tends to level off when the local capacity utilization is high, making it suitable for application scenarios where the local capacity utilization is usually high.

[0079] The S-shaped function relationship makes the primary frequency modulation coefficient K pThe machine's capacity utilization rate is more sensitive to changes in the middle range, while the changes tend to be gradual at both ends, making it suitable for application scenarios that require distinguishing between normal and extreme operating conditions.

[0080] It is understandable that, when performing a frequency modulation coefficient K... p In this regard, those skilled in the art can select or combine the aforementioned functional relationships according to the actual application scenario; for example, using a power function for the load-increasing transmission channel and a linear function for the load-cutting and reducing transmission channel should both be considered as implementation methods covered by this application. Specifically, the key point in selecting the functional relationship is: the primary frequency modulation coefficient of the load-increasing transmission channel. The primary frequency modulation coefficient of the load shedding and transmission reduction channel decreases as the local capacity utilization rate r increases. The frequency modulation coefficient increases with the increase of the local capacity utilization rate r; any functional relationship that satisfies this monotonicity relationship can achieve the technical objective of this application and falls within the protection scope of this application. In the technical solution of this application, the primary frequency modulation coefficient of the additional transmission channel is... The primary frequency modulation coefficient of the load shedding and power reduction channel The preferred functional relationship between the local capacity utilization rate r and the local capacity utilization rate is a power function. The following content will also use a power function relationship as an example for detailed description.

[0081] It should be noted that in the above functional relationship, the upper limit of the primary frequency modulation coefficient is... and the lower limit of the primary frequency modulation coefficient These are all parameters pre-set for a single VSG. Specifically, since the capacities of each VSG are different, if all VSGs use the same upper and lower limits... and This means that the technical solution of this application can only optimize for cases of uneven power distribution, but each VSG cannot converge to a state that is perfectly squared according to the local capacity utilization ratio. Therefore, in the technical solution of this application, the upper limit of the primary frequency regulation coefficient corresponding to each VSG is specified. and the lower limit of the primary frequency modulation coefficient Preferably, each is related to the highest power output P of the machine. M It is directly proportional; to make it easier to understand, a specific example will be used to describe it in detail below.

[0082] In a specific example, we can set This represents the lower limit of the primary frequency modulation coefficient of the i-th VSG. Let represent the upper limit of the primary frequency modulation coefficient of the i-th VSG; let Let represent the maximum transmit power of the i-th VSG; let the upper and lower limits of the uniform primary frequency regulation coefficient per unit capacity be respectively... and ,in, .

[0083] Then the upper limit of the primary frequency modulation coefficient of the i-th VSG and lower limit The calculation expression is: ; .

[0084] Based on the above expression, the upper limit of the primary frequency modulation coefficient of each VSG can be determined. Corresponding to the highest power output of the machine The ratio remains consistent; similarly, the lower limit of the primary frequency modulation coefficient of each VSG remains consistent. Corresponding to the highest power output of the machine The ratio also remains consistent. That is, based on the above design, when VSGs of different capacities have the same capacity utilization rate, each VSG should have the same frequency response capability per unit capacity. To further facilitate understanding, the control effect will be described in detail below through specific parameter examples.

[0085] Specifically, taking two VSGs as an example, we can set the maximum transmit power of these two VSGs to P respectively. M1 and P M2 The active power output of the two VSG units is P respectively. o1 and P o2 Then the local capacity utilization rates r1 and r2 of these two VSGs are respectively: r1 = P o1 / P M1 r2=P o2 / P M2 .

[0086] It should be noted that the objective of the technical solution in this application is not to make P o1 =P o2 Instead, it makes the local capacity utilization of the two VSGs tend to be the same, that is, r1=r2, which is equivalent to: P o1 / P M1 = P o2 / P M2 Therefore, when the local capacity utilization rate is the same, the output active power of the two VSGs is allocated according to the proportion of the local maximum power output.

[0087] For ease of description, the upper limit of the primary frequency modulation coefficient corresponding to the two VSGs can be set as follows: and The lower limit of the primary frequency modulation coefficient is and Assume the maximum power output P of the two VSG units. M1 and P M2 Satisfy: P M1 :P M2=1:2; therefore, the upper limit of the primary frequency modulation coefficient is... and and the lower limit of the primary frequency modulation coefficient and It should also satisfy: , Only in this way, when the capacity utilization rates of the two VSGs are equal, will the unit capacity power increments of the two VSGs be equal under the same frequency deviation, thus maintaining a consistent capacity utilization rate. If the upper and lower limits of the primary frequency modulation coefficient are not set according to the proportion of the maximum power that the unit can generate, even if the initial capacity utilization rates of the two VSGs are consistent, this consistency will be disrupted during subsequent load switching due to differences in the unit capacity frequency modulation response capability.

[0088] (1) For system-triggered loading events.

[0089] At this time, the system load increases and the frequency decreases, requiring each VSG to increase its power; the power increase factor of the i-th VSG at this time is the primary frequency regulation factor. The calculation expression is: .

[0090] Will , Substituting into the above expression, we get: .

[0091] In the formula, This indicates the maximum transmit power of the i-th VSG. This represents the lower limit of the primary frequency modulation coefficient of the i-th VSG. This represents the upper limit of the primary frequency modulation coefficient of the i-th VSG. and These represent the upper and lower limits of the primary frequency regulation coefficient per unit capacity, respectively. This represents the local capacity utilization rate of the i-th VSG.

[0092] The unit capacity increase factor for the additional transmission channel of the i-th VSG can be defined as: The calculation expression is: .

[0093] From the above formula, we can see that the unit capacity issuance coefficient is: Local capacity utilization The increase in capacity decreases as the capacity increases. Assuming the initial capacity utilization rates of the two VSGs are inconsistent, and r1 > r2, then the unit capacity increase coefficients for the two VSGs are respectively: and satisfy: .

[0094] The input load can be set as The additional power generated by the two VSGs during deployment was respectively and The additional power is calculated according to the primary frequency modulation coefficients corresponding to the two VSGs. and If we allocate the resources, then: ; .

[0095] After deployment, the local capacity utilization rates of the two VSGs are as follows: and They are respectively: ; .

[0096] In the formula, and These are the maximum power outputs of the two VSG units.

[0097] The difference in utilization rate between the two VSG units after deployment is: .

[0098] Since the unit capacity expansion coefficients for the two VSGs are respectively... and satisfy: Therefore: .

[0099] The above results show that when the local capacity utilization rate of the first VSG is higher than that of the second VSG, the unit capacity increase of the first VSG after being put into operation is less than that of the second VSG. Therefore, the difference in capacity utilization rate between the two VSGs decreases, and the power allocation shifts towards the direction of consistent capacity utilization rate.

[0100] (2) For system-triggered cutting events.

[0101] At this point, the system load decreases and the frequency increases, requiring each VSG to reduce its transmission power; the cutting and reduction factor of the i-th VSG at this time is the primary frequency modulation factor. The calculation expression is: .

[0102] Will , Substituting into the above expression, we get: .

[0103] .

[0104] In the formula, This indicates the maximum transmit power of the i-th VSG. This represents the lower limit of the primary frequency modulation coefficient of the i-th VSG. This represents the upper limit of the primary frequency modulation coefficient of the i-th VSG. and These represent the upper and lower limits of the primary frequency regulation coefficient per unit capacity, respectively. This represents the local capacity utilization rate of the i-th VSG. This represents the unit capacity reduction coefficient of the load shedding and reduction channel of the i-th VSG.

[0105] From the above formula, we can see that the unit capacity reduction coefficient is... Local capacity utilization The reduction is proportional to the increase. Assuming that the local capacity utilization rates of the two VSGs are different before load shedding, and r1 > r2, then the unit capacity reduction coefficients for the two VSGs are respectively: and satisfy: .

[0106] The load to be removed can be set as The power reduction of the two VSGs during load shedding was respectively and Furthermore, the power reduction is based on the primary frequency modulation coefficients corresponding to the two VSGs respectively. and If we allocate the resources, then: ; .

[0107] After load shedding, the local capacity utilization rates of the two VSGs are as follows: and They are respectively: ; .

[0108] In the formula, and These are the maximum power outputs of the two VSG units.

[0109] The difference in utilization rate between the two VSGs after load switching is: .

[0110] Since the unit capacity reduction factor for the two VSGs is respectively... and satisfy: Therefore: .

[0111] The above results show that when the local capacity utilization rate of the first VSG is higher than that of the second VSG, the unit capacity reduction of the first VSG after load shedding is greater than that of the second VSG. Therefore, the difference in capacity utilization rate between the two VSGs decreases, and the power allocation shifts towards a direction where the capacity utilization rates are consistent.

[0112] (3) When the local capacity occupancy rate is consistent.

[0113] If both VSGs have reached their local capacity utilization rate r1=r2=r, then in the additional transmission channel, the unit capacity increase coefficients for the two VSGs are respectively: and satisfy: Therefore, the primary frequency modulation coefficients corresponding to the two VSGs are respectively and satisfy: ;in, and These are the maximum power outputs of the two VSG units.

[0114] Due to the increased power generated by the two VSGs during deployment and According to the primary frequency modulation coefficients corresponding to the two VSGs respectively and Therefore, we have: .

[0115] Therefore, after the load is applied, the local capacity utilization rates of the two VSGs are respectively... and satisfy: .

[0116] Similarly, in the load shedding and power reduction channel, after the load is removed, the local capacity utilization rates of the two VSGs are respectively... and Still satisfied: .

[0117] It should be noted that during actual operation, when the maximum power output of the VSG decreases due to changes in energy storage status, temperature rise, current limitations, or adjustments to operating strategies, the upper limit of the primary frequency regulation coefficient can be adjusted synchronously according to the ratio of the current allowable full power output to the factory-set maximum full power output. and the lower limit of the primary frequency modulation coefficient This ensures that the control method in this application always matches the actual available capacity, exhibiting good engineering adaptability and robustness.

[0118] In a specific embodiment, when performing step S300, the preferred method for calculating the rate of change of the local frequency is to set a fixed time delay T. d The local frequency f at time t is... o (t) and T d The local frequency f before the time o (tT d Perform differential operations to obtain the rate of change of the local frequency, ROCOF. The specific calculation expression is: ROCOF = [f] o (t)-f o (tT d )] / T d .

[0119] It should be understood that there are various methods for calculating the rate of change (ROCOF) of the local frequency. For example, a linear regression method with multi-point fitting can be used to calculate the rate of change, as can a frequency tracking differentiator using a phase-locked loop. The appropriate method can be selected based on the actual needs of those skilled in the art. Since the fixed-delay differential calculation method is simple and computationally inexpensive, suitable for real-time implementation of digital controllers, this embodiment preferably uses a fixed-delay differential calculation method for the rate of change of the local frequency.

[0120] In a specific embodiment, when executing step S300, as mentioned above, the rate of change of the local frequency (ROCOF) is negative when the system is loaded, and positive when the system is unloaded. Therefore, the process of identifying loading or unloading events based on the rate of change of the local frequency (ROCOF) in this embodiment is as follows: setting a positive trigger threshold R. th When the rate of change of the machine frequency ROCOF < -R th When the system triggers a load event, it determines that the rate of change of the local frequency ROCOF > R. th When this occurs, the system determines that a load shedding event has been triggered.

[0121] It is important to know the trigger threshold R. th The value should be determined comprehensively based on factors such as system capacity, load disturbance amplitude, frequency measurement accuracy, and control response speed. If the trigger threshold R... th If the value of R is too small, it may cause false triggering due to frequency measurement noise or slight load fluctuations; if the trigger threshold R is too small, it may cause false triggering. th If the value of is too large, it may be insensitive to small-amplitude load disturbances and unable to respond in a timely manner. In this embodiment, for the trigger threshold R... th The preferred value range is 0.05Hz / s to 0.5Hz / s. The trigger threshold R... thTaking 0.1 Hz / s as an example, when the rate of change of the local frequency ROCOF < -0.1 Hz / s, the system is determined to trigger a load event. At this time, the primary frequency modulation coefficient of the load-addition channel can be called. When the rate of change of the local frequency (ROCOF) is greater than 0.1 Hz / s, the system is deemed to have triggered a load shedding event. At this time, the primary frequency modulation coefficient of the load shedding and transmission reduction channel can be called. .

[0122] In a specific embodiment, when performing step S400, if the system triggers a load-on event or a load-off event, the local frequency f at the time of the event trigger can be recorded. s As the event frequency, it also records the incremental primary frequency regulation power command P of the primary frequency regulation power module input active power loop at the time of event triggering. s This is a frequency modulation power increment when the event is triggered.

[0123] like Figure 4 As shown, when the system triggers a load event, causing the channel switching module to output enable M=1 to open the load-addition channel, the primary frequency modulation power module outputs an incremental primary frequency modulation power command at this time. The generation method is as follows: .

[0124] In the formula, This represents the primary frequency modulation coefficient of the additional transmission channel. This indicates the local frequency.

[0125] When the system triggers a load shedding event, causing the channel switching module to output enable M=0 to open the load shedding and power reduction channel, the primary frequency modulation power module outputs an incremental primary frequency modulation power command at this time. The generation method is as follows: .

[0126] In the formula, This represents the primary frequency modulation coefficient of the load shedding and power reduction channel. This indicates the local frequency.

[0127] It is important to note that in the traditional method, the primary frequency modulation power command P is usually calculated as: P = k(f N -f o ); where k represents the primary frequency modulation coefficient with a fixed value, f N Indicates the rated frequency. This indicates the local frequency. The traditional method uses the absolute deviation between the rated frequency and the current frequency as the basis for adjustment; as long as the current frequency is lower than the rated frequency, it will continuously generate additional transmission commands.

[0128] In the technical solution of this application, the incremental primary frequency modulation power command is based on the frequency f at the instant of event triggering. s Calculate the power change. Specifically, for a load-on event, the frequency drops after load is applied, typically with... ,therefore It is positive; this is the primary frequency modulation coefficient. The larger the value, the more VSGs are issued; due to the primary frequency modulation coefficient... The frequency decreases as the local capacity utilization rate (r) increases; therefore, high utilization rates result in less VSG frequency increase, while low utilization rates result in more VSG frequency increase. For load shedding events, the frequency increases after load shedding, typically with... ,therefore It is positive; at this time, the primary frequency modulation coefficient The larger the value, the more the VSG will reduce its output; due to the primary frequency modulation coefficient... The value increases with the local capacity utilization rate (r), therefore, VSGs with high utilization rates experience greater reductions in power generation, while VSGs with low utilization rates experience less reductions.

[0129] It is understood that in the technical solution of this application, the direction of power increase or decrease is determined by the local frequency f after the event is triggered. o Relative to event frequency f s The direction of change is determined by the local frequency f, not by the local frequency f. o Relative to the rated frequency f N The absolute deviation determines the frequency. Therefore, even if the system frequency is still below the rated frequency during load shedding—for example, the grid frequency rises from 49.5Hz to 49.8Hz after load shedding, which is still below 50Hz—as long as its frequency is rising relative to the instant the event is triggered, this application will still generate a reduction command. This avoids the problem in traditional control where the frequency rises during load shedding but is still below the rated value, and high-occupancy VSGs need to increase their transmission in the opposite direction. This ensures that the control logic of this application meets the goal of evenly reducing the transmission of high-occupancy VSGs throughout the entire frequency recovery process.

[0130] It should be understood that, as described above regarding the operation of a primary frequency modulation power module, when the system triggers a load-on event, it switches to the load-on power-increasing channel; when the system triggers a load-off event, it switches to the load-off power-reducing channel. However, during load switching, the system frequency often experiences transient oscillations, i.e., the rate of frequency change is negative at the moment of load on, but may briefly become positive due to frequency overshoot. This may cause frequent switching between the load-on power-increasing channel and the load-off power-reducing channel after a valid event is triggered, leading to power oscillations or even system instability. Therefore, the technical solution of this application introduces a lockout re-enabling mechanism to restrict the system's channel switching and ensure a smooth channel switching process. For ease of understanding, the implementation process of the lockout re-enabling mechanism will be described in detail below.

[0131] In a specific embodiment, such as Figure 4 and Figure 5 As shown, the implementation process of the lockout re-enable mechanism is as follows: When a valid event is detected and the corresponding channel switching is completed, the system enters a lockout state that prohibits channel switching, meaning that the channel switching module cannot enable output in the lockout state. When the system enters the steady-state range based on the lockout state duration and / or the rate of change of the local frequency, the lockout state is released, allowing the system to switch channels again; otherwise, the lockout state remains in place.

[0132] It is understandable that after a valid event is triggered, the transient oscillation duration of the system frequency is finite. Therefore, the duration of the latched state can be used to determine whether the system has entered the steady-state region. Simultaneously, the rate of frequency change during transient oscillation is significantly higher than the rate of frequency change during steady-state operation; therefore, the rate of change of the local frequency can also be used as a criterion for determining whether the system has entered the steady-state region. Of course, to further ensure safety, this embodiment preferably uses both the latched state duration and the local frequency change rate as the criteria for determining whether the system has entered the steady-state region; that is, the system is only unlocked when both the latched state duration and the local frequency change rate simultaneously meet the criteria. For easier understanding, the specific process for determining whether the system has entered the steady-state region will be described in detail below.

[0133] In a specific example, such as Figure 5 As shown, the process for determining whether a system has entered the steady-state region includes the following steps: A latching time threshold T can be set. lock and steady-state enable threshold R st And the steady-state enable threshold R st Less than the trigger threshold R th The current time t and the time of the last valid event trigger t. s The difference is greater than the latching time threshold T lock Furthermore, the absolute value of the rate of change of the local frequency ROCOF is less than the steady-state enable threshold R. st When the system enters the steady-state region, it is determined that the system has entered the steady-state region.

[0134] Understandably, the latching time threshold T lock This ensures that no channel switching occurs for a certain period after a valid event is triggered, avoiding erroneous switching caused by frequency transient oscillations; steady-state enable threshold R st The system ensures that the next switching is only allowed when the frequency change rate tends to stabilize; the combination of these two conditions ensures the reliability and stability of channel switching.

[0135] For the latching time threshold T lock The value of can be determined comprehensively based on factors such as the system's inertia time constant, frequency recovery time, and control cycle. Lockout time threshold T lockIf the value is too short, it will be insufficient to shield transient oscillations; the latching time threshold T lock If the value of T is too long, it may delay the response to continuous load disturbances; therefore, in this embodiment, the latching time threshold T is... lock The preferred value range is 0.5s to 3s.

[0136] For the steady-state enable threshold R st The value is less than the trigger threshold R th This ensures that the system only allows the next channel switch after exiting the transient process. Therefore, in this embodiment, the steady-state enable threshold R... st The value of R can be (0.3~0.5). th The specific value can be determined by those skilled in the art based on their actual needs.

[0137] Specifically, such as Figure 4 As shown, a switching enable module can be set in the primary frequency modulation power module. The inputs of this module are the rate of change of the local frequency (ROCOF) and the system time (Time). When a valid event is detected by the rate of change of the local frequency (ROCOF), the current time can be recorded as the valid event trigger time (t). s At this point, switching the enable module can control the channel switching module to remain locked. Then, timing begins and the rate of change of the local frequency (ROCOF) is continuously acquired; as the locked state continues, when tt... s >T lock And |ROCOF| < R st When the switching enable module sends an enable drive signal En to the channel switching module, it releases the lockout on the channel switching module.

[0138] To further facilitate understanding of the technical solution of this application, the effect of the technical solution of this application can be verified by simulation below.

[0139] A simulation model of three VSGs running in parallel was built in the MATLAB / Simulink simulation platform. The three VSGs can be labeled VSG1, VSG2, and VSG3, respectively; the maximum local power output P of the three VSGs is [missing information]. M The initial loads of the three VSGs are 6kW, 8kW, and 12kW, respectively. Initially, each VSG carries a 3kW load, meaning their initial capacity utilization rates (r) are 50%, 37.5%, and 25%, respectively, indicating an unbalanced state. The upper limit K of the primary frequency regulation coefficient corresponding to VSG1 is... max The lower limit of the primary frequency modulation coefficient K is 15000W / Hz. min The maximum value for the primary frequency modulation coefficient K corresponding to VSG2 is 750W / Hz. max The lower limit of the primary frequency modulation coefficient K is 20000W / Hz. minThe maximum value for the primary frequency modulation coefficient K corresponding to VSG3 is 1000W / Hz. max The lower limit of the primary frequency modulation coefficient K is 30000W / Hz. min It is 1500W / Hz.

[0140] The simulation conditions are set as follows: 3kW load is applied at 0.1s; 3kW load is removed at 1.1s; 3kW load is removed at 2.1s; 3kW load is removed at 3.1s; 9kW load is applied at 4.1s; 9kW load is removed at 5.1s; 6kW load is applied at 6.1s.

[0141] Simulation results are as follows Figure 6 As shown in the figure, the result indicates that: When 3kW is applied in 0.1s, all three VSGs switch to the additional power application channel, and the corresponding primary frequency regulation coefficients are all increased. At the same time, the active power output of all three VSGs increases; based on the increase in active power, the local capacity utilization rate of all three VSGs increases; since the amount of active power increase of the three VSGs is different, the difference in capacity utilization rate among the three VSGs is reduced.

[0142] When the load is cut off at 3kW in 1.1s, all three VSGs switch to the load-cutting and power-reduction channel. The primary frequency regulation coefficients for VSG1 and VSG2 continue to increase, while the primary frequency regulation coefficient for VSG3 decreases. Simultaneously, the active power output of all three VSGs decreases. Based on this decrease in active power, the local capacity utilization rate of all three VSGs decreases. Because the amount of active power reduction differs among the three VSGs, the difference in their capacity utilization rates further diminishes.

[0143] When the load shedding continues at 3kW for 2.1 seconds, all three VSGs maintain their load shedding and power reduction channels, and their primary frequency regulation coefficients are all reduced to varying degrees. Simultaneously, the active power output of all three VSGs decreases; based on this reduction in active power, the capacity utilization rate of all three VSGs decreases; and because the reduction in active power varies among the three VSGs, the difference in capacity utilization rate among them is further reduced.

[0144] When the load shedding continues at 3kW for 3.1 seconds, all three VSGs maintain their load shedding and power reduction channels, and their primary frequency regulation coefficients are all reduced to varying degrees. Simultaneously, the active power output of all three VSGs decreases; based on this reduction in active power, the capacity utilization rate of all three VSGs decreases; and because the reduction in active power varies among the three VSGs, the difference in their capacity utilization rates is further reduced.

[0145] When 9kW is applied at 4.1s, all three VSGs switch to the additional power application channel, and the corresponding primary frequency regulation coefficients increase, albeit by different amounts. Simultaneously, the active power output of all three VSGs increases; based on this increase in active power, the local capacity utilization rate of all three VSGs increases; and because the amount of active power increase varies among the three VSGs, the difference in capacity utilization rate among them further decreases.

[0146] When the load was cut off at 9kW in 5.1 seconds, all three VSGs switched to the load-cutting and power-reduction channel, and the corresponding primary frequency regulation coefficients were reduced, but by different amounts. Simultaneously, the active power output of all three VSGs decreased; based on the reduction in active power, the local capacity utilization rate of all three VSGs decreased; because the reduction in active power of the three VSGs was different, the difference in capacity utilization rate among the three VSGs was further reduced to a uniform level.

[0147] When 6kW is applied at 6.1s, all three VSGs switch to the additional power supply channel, and the corresponding primary frequency regulation coefficient is increased. At the same time, the active power output of all three VSGs increases, and based on the increase in active power, the local capacity utilization rate of all three VSGs increases and remains consistent.

[0148] Another aspect of this application provides a computer-readable storage medium, in a preferred embodiment of which a computer program is stored on the storage medium; when the computer program is executed by a processor, it implements the above-described VSG primary frequency modulation channel power sharing control method.

[0149] Another aspect of this application provides an electronic device, in one preferred embodiment of which includes a processor and a memory; the memory is used to store a computer program, and the processor is used to execute the computer program to implement the above-described VSG primary frequency modulation channel power sharing control method.

[0150] The basic principles, main features, and advantages of this application have been described above. Those skilled in the art should understand that this application is not limited to the above embodiments. The embodiments and descriptions in the specification are merely the principles of this application. Various changes and modifications can be made to this application without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claims. The scope of protection claimed by this application is defined by the appended claims and their equivalents.

Claims

1. A power sharing control method for the primary frequency modulation channel of a VSG, applied to a multi-VSG parallel system, characterized in that, Includes the following steps: Collect the local output active power and local frequency of each VSG; The local capacity utilization rate is calculated based on the local active power output, and the primary frequency regulation coefficient of the load-increasing transmission channel is constructed as the local capacity utilization rate increases, and the primary frequency regulation coefficient of the load-cutting and transmission-reducing channel is constructed as the local capacity utilization rate increases. The load activation or load deactivation event is identified based on the rate of change of the local frequency, and the corresponding primary frequency modulation coefficient is invoked. In response to the triggering of a load-on event or a load-off event, the current event frequency and primary frequency modulation power increment are obtained, and an incremental primary frequency modulation power command is generated by combining the called primary frequency modulation coefficient. The incremental primary frequency regulation power command is superimposed on the local active power reference to form the active power command used for control.

2. The VSG primary frequency modulation channel power sharing control method as described in claim 1, characterized in that, The primary frequency modulation coefficients corresponding to the load increase channel and the load decrease channel are related to the local capacity utilization rate by one or more combinations of linear, power, exponential, logarithmic, or S-shaped functions.

3. The VSG primary frequency modulation channel power sharing control method as described in claim 2, characterized in that, The primary frequency modulation coefficients corresponding to the load-increasing and load-reducing channels are related to the local capacity utilization rate by a power function. The specific calculation expressions are as follows: ； ； In the formula, This represents the primary frequency modulation coefficient of the additional transmission channel. This represents the primary frequency modulation coefficient of the load shedding and power reduction channel. This represents the lower limit of the primary frequency modulation coefficient. This represents the upper limit of the frequency modulation coefficient, and r represents the local machine's capacity utilization rate. This represents the nonlinear adjustment index.

4. The VSG primary frequency modulation channel power sharing control method as described in claim 3, characterized in that, The upper limit of the primary frequency modulation coefficient corresponding to each VSG and the lower limit of the primary frequency modulation coefficient It is directly proportional to the maximum power output of each VSG.

5. The VSG primary frequency modulation channel power sharing control method as described in any one of claims 1-4, characterized in that, The rate of change of the local frequency is negative when the system is loaded, and positive when the system is unloaded. The process of identifying load-on or load-off events based on the rate of change of the local frequency is as follows: Set a trigger threshold. When the rate of change of the local frequency is less than the negative trigger threshold, the system is determined to trigger a load-on event; when the rate of change of the local frequency is greater than the positive trigger threshold, the system is determined to trigger a load-off event.

6. The VSG primary frequency modulation channel power sharing control method as described in claim 5, characterized in that, When the system triggers a load-on event or a load-off event, the corresponding incremental primary frequency regulation power command is generated as follows: ； ； In the formula, and These represent the incremental primary frequency modulation power commands corresponding to the load activation and load deactivation events, respectively. This represents the frequency modulation power increment when the event is triggered. and These represent the primary frequency modulation coefficients for the load-increasing transmission channel and the load-reducing transmission channel, respectively. Indicates the frequency of events when an event is triggered. This indicates the local frequency.

7. The VSG primary frequency modulation channel power sharing control method as described in claim 5, characterized in that, When the system triggers a load event, it switches to the load increase channel; when the system triggers a load cut event, it switches to the load cut and load reduction channel. Once a valid event is detected and the corresponding channel switch is completed, the system enters a locked state that prohibits channel switching. When the system is determined to have entered the steady-state range based on the duration of the lockout state and / or the rate of change of the local frequency, the lockout state is released, allowing the system to switch channels again; otherwise, the lockout state is maintained.

8. The VSG primary frequency modulation channel power sharing control method as described in claim 7, characterized in that, The process of determining whether a system has entered the steady-state region includes the following steps: Set the latching time threshold and steady-state enable threshold, and the steady-state enable threshold is less than the trigger threshold; When the difference between the current time and the time of the last valid event trigger is greater than the latching time threshold, and the absolute value of the rate of change of the local frequency is less than the steady-state enable threshold, the system is determined to have entered the steady-state range.

9. An electronic device, characterized in that, It includes a processor and a memory; the memory is used to store a computer program, and the processor is used to execute the computer program to implement the VSG primary frequency modulation channel power sharing control method as described in any one of claims 1-8.

10. A computer-readable storage medium, characterized in that, The storage medium stores a computer program; when the computer program is executed by a processor, it implements the VSG primary frequency modulation channel power sharing control method as described in any one of claims 1-8.

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