Network construction type VSG output power decoupling method based on voltage signal composite feedforward

Abstract

The invention discloses a network construction type VSG output power decoupling method based on voltage signal composite feedforward, relates to the technical field of power electronic control, and provides a network construction type converter grid-connected system and a method for realizing converter output power decoupling through converter output voltage signal composite feedforward for network construction type VSG power synchronous control. Comprising a network construction type VSG power control module, a power grid parameter detection unit, a line impedance observer, a virtual impedance voltage drop feedforward loop and a voltage signal secondary feedforward loop. According to the composite feed-forward control strategy, virtual impedance and voltage amplitude and power angle compensation are combined, the coupling effect of active power and reactive power is remarkably weakened, efficient decoupling is achieved, and the method is suitable for a complex power grid environment.

Description

Technical Field

[0001] The present invention belongs to the technical field of power electronics control, and particularly relates to a decoupling method for the output power of a grid-forming VSG based on voltage signal composite feedforward. Background Art

[0002] The converter with grid-forming control is crucial for the power system. By generating a virtual excitation voltage signal to maintain the stable response of the system, it no longer depends on the phase-locked loop (PLL) to synchronize system information, presents a stable voltage characteristic externally, and provides voltage support for the system.

[0003] The power synchronization link of VSG control enables it to synchronize with the power grid during grid connection and has the ability to support the power grid. This method can improve the operation stability of a power system with a large new energy penetration rate. VSG control is the power loop of a grid-forming converter, making the converter device have damping and inertia, and can improve the transient stability of power electronics.

[0004] The related research on grid-forming VSG control is based on the premise of ideal line impedance characteristics. In fact, the line from the output voltage of the inverter to the grid connection point voltage presents an inductive impedance characteristic rather than a purely resistive one, and this phenomenon is more serious in medium and low voltage lines; and due to the voltage drop in the line, the change of power angle is difficult to ignore, and the P-f and Q-U characteristics simulating a synchronous generator are no longer applicable, and there is a serious coupling between active power and reactive power.

[0005] In the actual line under medium and low voltage environment, the output power of the converter based on grid-forming VSG control is limited by the combined influence of line impedance characteristics and voltage signal fluctuations. There is a strong coupling between active power and reactive power, and the operation stability of the system is challenged. Therefore, it is necessary to design a scheme to meet the actual requirements, decouple the output power of the grid-forming converter in the grid-connected operation state, and reduce the output power fluctuation. Summary of the Invention

[0006] In order to solve the technical problems existing in the background art, the present invention aims to provide a decoupling method for the output power of a grid-forming VSG based on voltage signal composite feedforward. To suppress the coupling of output power, a power decoupling strategy with a composite structure is designed for the grid-connected state of the grid-forming converter. The virtual impedance link is used to reconstruct the line impedance, and the feedforward link is used to suppress the power coupling caused by voltage amplitude and phase angle fluctuations.

[0007] To solve the technical problems, the technical solution of the present invention is as follows:

[0008] A decoupling method for the output power of a grid-forming VSG based on voltage signal composite feedforward, the method comprising:

[0009] S1: Obtain power grid parameters, system static parameters and line impedance information, build a grid-forming VSG control grid-connected model, identify the line impedance from the VSG terminal bus to the grid-connection point bus through a state observer, construct a power relationship matrix and calculate the steady-state operating point;

[0010] S2: Based on the line impedance parameters estimated in step S1, considering the actual offset coefficient, calculate the virtual negative resistance and inductance, and generate the first virtual voltage drop feedforward signal to adjust the VSG power synchronization link, so as to compensate for the influence of line impedance on power output;

[0011] S3: Collect the fluctuations of the electromotive force amplitude and phase angle after the first voltage feedforward. This feedforward signal provides a basis for the secondary feedforward compensation. Calculate the secondary feedforward value based on the system static operating point, further adjust the voltage response, and provide a stable voltage reference for the subsequent decoupling of current and voltage;

[0012] S4: Use the voltage signal after composite feedforward as a reference to participate in the decoupling of the filter inductor current and capacitor voltage. The decoupled voltage signal is used for SVPWM modulation to accurately control the operation of the inverter, and finally achieve stable power output and grid voltage.

[0013] Furthermore, step S1 includes:

[0014] The grid-forming converter grid-connected system consists of a bridge voltage source inverter composed of 4 IGBTs with anti-parallel freewheeling diodes, an LC filter and a line impedance; the power synchronization part of the grid-forming converter is composed of VSG control. The active loop has damping D and inertia J, simulating the mechanical motion equation of a synchronous generator, enabling the system to have frequency support ability, and the reactive loop retains the droop characteristic; its specific expression is:

[0015]

[0016] Among them, P m 、P e respectively represent the mechanical power and electromagnetic power of the system, ω and ω n respectively represent the system angular frequency and rated angular frequency; J and D respectively represent the virtual moment of inertia and system damping coefficient of the synchronous generator simulated in the VSG strategy; δ represents the phase of the generated excitation electromotive force, which is called the power angle;

[0017] By default, the impedance between transmission lines is purely inductive, and the impedance angle between lines can be considered 90°. To accurately describe the output power characteristics of the grid-forming converter in medium- and low-voltage lines, considering the coexistence of line resistance and reactance, the terminal electromotive force E of the grid-forming VSG-controlled converter is a controllable quantity, the grid voltage U and the transmission current I between lines are given quantities, and the corresponding information can be obtained by the sampling measurement module in the simulation platform. In practice, the terminal voltage amplitude and phase angle can be sampled by the synchronous vector measurement device at the bus. The difference between the phase angle of the terminal voltage E and the phase angle of the grid voltage U is regarded as the power angle δ, and a mathematical model of the grid-forming output power is constructed, which is specifically expressed as follows:

[0018]

[0019] Where P and Q represent the active power and reactive power output by the grid-forming converter respectively; E and U represent the terminal voltage of the inverter and the grid connection point voltage respectively; φ represents the line impedance angle; X eq and R eq represent the equivalent inductance and equivalent resistance of the line respectively;

[0020] The power monitoring module is responsible for measuring the active power and reactive power output of the photovoltaic and energy storage system in real time, which refers to a calculation program or device capable of performing power calculations. By monitoring the power flow at the grid connection point, this module helps the system understand the current power exchange situation, so as to accurately adjust the output of active and reactive power, ensuring the stable operation of the system and coordination with the grid;

[0021] The static operating point of the grid-forming converter can well reflect the rated operating state of the system. The static operating voltage Es represents the amplitude of the electromotive force at the terminal bus of the grid-forming converter, δs represents the phase angle of the electromotive force at the terminal bus of the grid-forming converter, Ps represents the value of the active power output by the grid-forming converter during steady-state operation, and Qs represents the value of the reactive power output by the grid-forming converter during steady-state operation; the above values are all constant values and can be obtained by sampling with measuring equipment;

[0022] The voltage vector and current vector collected by the synchronous vector measurement device at the bus on the grid-forming converter side and the grid connection point side are used. The sampling frequency needs to meet the Nyquist sampling theorem to ensure signal integrity; a robust state observer is designed to estimate the current and voltage states of the line online. The state estimation process is specifically expressed as follows:

[0023]

[0024] Where is the observed state, that is, the output state, y is the input state provided by the state observer, and L is the observer gain matrix, which is designed through the optimal control theory;

[0025] Estimate the resistance R of the line by combining the output of the state observer with the recursive least squares method line and reactance X line , and the specific expression is:

[0026] θ = [R, X] T

[0027] θ k+1 = θ k + L k (y k - φ k T θ k )

[0028] where L k is the gain matrix; y k is the actual sampled data, φ k is the regression variable, θ k is the parameter to be estimated;

[0029] According to the real-time measurement data, dynamically adjust the observer parameter L to improve the system robustness and accuracy; the result accuracy is affected by the measurement device, and the final result is fed back to the power grid control system online, and R line and X line are updated in real time;

[0030] The output power relationship matrix of the grid-forming VSG control will be used for subsequent program calculations, and the specific expression is:

[0031]

[0032] The output power depends on the P-f and Q-U characteristics. In the relationship matrix, is used as the output power decoupled quantity, which is characterized as the direct power representation under the independent control part; is the output power coupling quantity, that is, the output power to be decoupled. In order to satisfy the independent control of active power and reactive power, the coupling quantity should be weakened from two aspects They are the impedance angle caused by the line impedance and the amplitude and phase angle fluctuations of the generated voltage signal on the grid-forming converter side in turn.

[0033] Furthermore, the step S2 includes:

[0034] Based on the line impedance estimated in step S1, it is directly used for the calculation of the virtual negative resistance value Rv and the virtual inductance value Lv. Considering the impedance offset phenomenon, if the equivalent value after the system accesses the virtual resistance Rv is less than zero, it may cause system instability. In addition, due to the existence of parasitic resistance in the actual line, the transmission line will not present pure inductance. In engineering, the resistance-inductance ratio The transmission line with a value less than 0.12 can be regarded as an inductive line; by using the setting method of the virtual negative resistance Rv, the value of the virtual negative resistance should avoid this situation, that is, the value of the virtual negative resistance Rv should be less than the sum of the actual output resistance and the line resistance. The method should be applicable to general detection equipment and general measurement accuracy, and the maximum offset in the actual environment does not exceed 10%. The specific expression of the virtual negative resistance Rv setting method is:

[0035]

[0036] The bus voltage vector E on the grid-forming converter side and the line current vector I collected in step S1 are transformed from the time domain to the two-phase rotating coordinate through the Park transformation; calculate the virtual voltage drop generated by the virtual impedance with the set virtual impedance value. The specific expression of the virtual voltage drop is:

[0037]

[0038] where, E d* 、E q* are the d-axis and q-axis voltage reference values after passing through the virtual impedance link respectively; E d 、E q are the d-axis and q-axis reference values of the virtual electromotive force respectively, and I d 、I q are the d-axis and q-axis inductor currents respectively;

[0039] The voltage signal after feeding in the virtual voltage drop for the first time is then transformed back to the three-phase coordinate system through the inverse Park transformation. The virtual negative resistance is introduced to eliminate the resistance component in the output impedance of the inverter sending end and the line impedance, and the virtual inductor is used to further increase the equivalent impedance angle of the system, so as to decouple the transmission power caused by the impedance angle.

[0040] Furthermore, step S3 includes:

[0041] The three-phase voltage signal E obtained by the transformation in step S2 is controllable and measurable. According to the system static operating point calculated in step S1, determine the static operating voltage amplitude Es and phase angle δ s at the bus of the grid-forming converter, as well as the active power Ps and reactive power Qs output during steady-state operation;

[0042] Assume that the reactive power command is constant and the active power has a step change at a certain moment. Then, the active power control will increase the phase angle to track the active power command. Since the reactive power command does not change, the reactive power control will passively reduce the voltage amplitude through feedback. This feedback is limited by the bandwidth of the power loop, resulting in a system delay in response and thus reactive power fluctuations. Similarly, assume that the active power command remains unchanged and the reactive power has a step change. The reactive power loop will increase the voltage amplitude to track the reactive power command, and then the active power loop will reduce the phase angle through the feedback mechanism to maintain the stability of the active power.

[0043] Then, it is proposed that introducing a power angle feedforward term in the active power control loop and an amplitude feedforward term in the reactive power control loop can cancel the inherent power coupling relationship. The purpose of this minimization is to ensure that the active power is mainly affected by the phase difference and the reactive power is mainly affected by the voltage amplitude, enhancing the P-f and Q-U characteristics of the VSG system. The specific decoupling control expression is:

[0044]

[0045] where Δδ and ΔE are the fluctuations of the potential phase angle and amplitude on the grid-forming converter side, respectively.

[0046] When the voltage phase angle is difficult to measure, the compensation amounts of the voltage amplitude and phase angle compensation are also equivalently characterized by the line impedance. The specific expression is:

[0047]

[0048] In the feedforward compensation, the changes in the voltage amplitude ΔE and the power angle Δδ are system measurement values, that is, the differentials of the voltage signal amplitude and phase angle. In actual measurement, it is difficult to capture the change in the phase angle. Considering the inherent integral relationship between the phase and frequency, the phase difference detection can also be converted into frequency detection, and the generated phase feedforward can also be converted into frequency feedforward, which is equivalent to directly introducing the VSG-side frequency quantity to compare with the grid frequency. The feedforward quantities ΔE f and Δδ f are calculated based on the system state and external disturbances in the current sampling period and are only valid in the current current control period. Therefore, there is a delay effect in the data compensation in actual applications. An integral link is added in the continuous system to ensure that the feedforward value is continuously effective throughout the control process. The calculated voltage amplitude feedforward value ΔE f and the power angle feedforward Δδ f are compensated to E if and δ if . The obtained secondary compensation values E sf and δ sf . The specific expression of the compensated voltage signal is:

[0049]

[0050] The feedforward control can quickly compensate when the power or voltage changes, reducing the system response delay. This fast response characteristic is particularly important when the load fluctuates or the PV output is unstable, which helps to improve the dynamic performance of the system.

[0051] Further, step S4 includes:

[0052] The voltage signal after composite feedforward is used as a reference value and first participates in the decoupling control of the filter inductor current. Through the decoupling equation, the reference voltage E sfdq is converted into the target inductor current I Ldq . During this process, the coupling term of the filter inductor is dynamically compensated to eliminate the cross influence between the d-axis and q-axis currents, ensuring that the inductor current is consistent with the voltage reference value and improving the system control accuracy and dynamic performance.

[0053] Next, the decoupled inductor current signal is used for the decoupling control of the filter capacitor voltage. Through dynamic compensation, the final target output voltage V odq is calculated. This decoupling process effectively reduces the voltage fluctuation caused by the non-linear dynamic characteristics of the capacitor, ensuring the stability and fast response ability of the output voltage.

[0054] Subsequently, the decoupled target voltage signal V odq is converted into the three-phase instantaneous reference voltage V oabc , and is input into the space vector pulse width modulation algorithm. This algorithm generates the three-phase PWM control signals S a , S b and S c . SVPWM optimizes the switching sequence to make the output voltage waveform close to a sine wave, while reducing the harmonic distortion rate, ensuring high-precision regulation of the inverter output voltage in terms of amplitude, frequency, and phase.

[0055] To ensure the safety and stability of the system, the circuit forms a closed-loop feedback regulation mechanism by real-time sampling the output voltage and current signals and dynamically comparing them with the reference signals. At the same time, the system is equipped with a protection module that can automatically adjust or cut off the PWM signal when detecting abnormal states such as overvoltage, overcurrent, or short circuit, to prevent damage to the power devices and ensure the stable operation of the system.

[0056] Through the above steps, the combination of composite feedforward and the decoupling control of the filter inductor and capacitor with SVPWM modulation finally realizes the efficient, stable, and safe control of the inverter operating state.

[0057] A grid-forming VSG output power decoupling system based on voltage signal composite feedforward. The system is used to execute any of the methods described above. The system includes: a grid parameter detection unit, a line impedance observer, a voltage signal secondary feedforward loop, a virtual impedance voltage drop feedforward loop, and a grid-forming VSG power control module. The grid-forming VSG control architecture is adopted. The voltage, current, and frequency signals are collected in real time through the grid parameter detection unit, and the line parameters are estimated online by the line impedance observer. The virtual impedance voltage drop feedforward loop simulates the line impedance characteristics for voltage drop compensation, and the voltage signal secondary feedforward loop further adjusts the influence of voltage changes on power. The grid-forming VSG power control module realizes active and reactive decoupling control based on the P-f and Q-U droop characteristics, and combines virtual inertia and a double closed-loop structure to significantly improve the dynamic response ability and grid support performance of the inverter.

[0058] Furthermore, the grid parameter detection unit collects key electrical parameters of the grid through voltage transformers and current transformers. The signal processing module extracts the effective value and harmonic information based on digital filtering and fast Fourier transform. The data communication module uploads the processing results to the control system or cloud platform. This unit supports high-frequency sampling and abnormal state detection, and can realize multi-point distributed monitoring through wireless or bus protocols, and is applicable to smart grid, distributed generation, and microgrid application scenarios.

[0059] The line impedance observer constructs a line state space model based on the voltage and current signals collected in real time and combines with the state estimation algorithm to achieve online high-precision estimation of the equivalent resistance and reactance. This observer has high robustness and fast response ability, can adapt to complex grid environments, and provides basic support for subsequent compensation control and system stability.

[0060] On the basis of primary compensation, the voltage signal secondary feedforward loop further collects and analyzes the voltage amplitude and phase angle changes, provides more accurate dynamic compensation, weakens the power imbalance caused by external disturbances or load fluctuations by adjusting the system state in real time, improves the voltage control accuracy and system dynamic response speed, ensures that the inverter output voltage is stable within the set range, and enhances the system power supply reliability and power regulation performance.

[0061] The virtual impedance voltage drop feedforward loop introduces a virtual resistor and inductor to simulate the line impedance characteristics and realizes voltage drop compensation for the inverter output voltage. It actively calculates the voltage changes caused by the line impedance and implements compensation, effectively improving the system equivalent impedance characteristics and power decoupling performance, and suppressing the power coupling problems caused by line parameter fluctuations or load disturbances, thereby enhancing the system stability and power supply quality.

[0062] The grid-forming VSG power control module realizes precise regulation of active and reactive power by simulating the rotor motion equation of a synchronous generator, thereby improving the system's dynamic response performance and operation stability. The control strategy adopts a double-closed-loop structure based on P-f and Q-U droop characteristics, achieving active power output control through frequency regulation and reactive power balance through voltage regulation. The virtual inertia and virtual damping mechanisms are introduced to endow the inverter with inertia support and voltage regulation capabilities.

[0063] A computer device includes a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the program, it implements a method for decoupling the output power of a grid-forming VSG based on voltage signal composite feedforward as described in any one of the above.

[0064] A computer-readable storage medium stores a computer program, and when the program is executed by a processor, it implements a method for decoupling the output power of a grid-forming VSG based on voltage signal composite feedforward as described in any one of the above.

[0065] Compared with the prior art, the advantages of the present invention are as follows:

[0066] (1) The composite feedforward control strategy designed in the present invention, combined with virtual impedance and feedforward compensation of voltage amplitude and power angle, significantly weakens the coupling effect between active power and reactive power, ensuring their independent control. Compared with traditional methods, it considers actual line problems, gets rid of the limitation of medium and low voltage line power based on line impedance parameters, realizes more efficient power decoupling, and is applicable to complex power grid environments.

[0067] (2) Through dynamic compensation and fast feedforward control, the present invention significantly improves the response speed of the system, can quickly respond to photovoltaic power generation fluctuations and load changes, and avoids power fluctuations or control instability problems caused by delays.

[0068] (3) The present invention uses virtual impedance to reconstruct the line impedance and combines feedforward control to suppress system oscillations and instability problems caused by complex line impedance characteristics and dynamic load changes. At the same time, feedforward compensation reduces the nonlinear influence in the power control process, enhancing the system's adaptability and robustness to power grid disturbances. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 is the flowchart of the steps of the present invention;

[0070] Figure 2 is the main circuit and system control design diagram of the present invention;

[0071] Figure 3 is the overall system structure diagram of the present invention;

[0072] Figure 4 Schematic diagram for small-signal analysis of the output power and solution of the static operating point of the present invention;

[0073] Figure 5 Schematic diagram of the first compensation scheme for virtual voltage drop of the present invention;

[0074] Figure 6 Schematic diagram of the cross-feedforward secondary voltage compensation scheme of the present invention. Specific embodiments

[0075] The following describes the specific embodiments of the present invention in conjunction with the embodiments:

[0076] It should be noted that the structures, ratios, sizes, etc. illustrated in this specification are only used to cooperate with the content disclosed in the specification for those skilled in this technology to understand and read, and are not used to limit the implementation conditions of the present invention. Any modification of the structure, change of the proportional relationship, or adjustment of the size, without affecting the effects that the present invention can produce and the purposes that can be achieved, should still fall within the scope covered by the technical content disclosed in the present invention.

[0077] At the same time, the terms such as "upper", "lower", "left", "right", "middle", and "one" cited in this specification are only for the convenience of clear narration, and are not used to limit the scope of implementation of the present invention. The change or adjustment of their relative relationships, without substantial change in the technical content, should also be regarded as the scope that the present invention can implement.

[0078] Embodiment 1:

[0079] A decoupling method for the output power of a grid-connected system with a grid-forming VSG control of the present invention, the overall steps are as Figure 1 shown, and the design method is as Figure 3 shown. The technical solution steps are as follows:

[0080] S1, build a grid-connected model with grid-forming converter VSG control (as Figure 2 shown), construct a mathematical model of the output power of the grid-forming VSG, calculate the corresponding steady-state operating point, and identify the line impedance from the VSG output bus to the grid connection point bus through a state observer. List the relationship matrix of active power and reactive power.

[0081] S2, considering the actual impedance offset coefficient of the line, calculate the corresponding virtual negative resistance value and virtual inductance value from the line impedance observation value, and calculate and give the first virtual voltage drop feedforward value (as Figure 5 shown), which acts on the VSG power synchronization link.

[0082] S3. Collect the amplitude and phase angle of the electromotive force of the system after adding the first voltage feedforward, obtain the corresponding fluctuation amount by taking the difference based on the sampling frequency, and determine the secondary feedforward value according to the static operating voltage of the system (as Figure 6 shown), and act on the power synchronization link of the VSG.

[0083] S4. The voltage signal after composite feedforward is used as a reference value to participate in the decoupling of the filter inductor current and the filter capacitor voltage. The decoupled voltage signal participates in the modulation of the PWM signal to control the operating state of the inverter.

[0084] The specific method in the step S1 is as follows:

[0085] The converter with grid-forming VSG control is a bridge-type voltage source inverter composed of 4 IGBTs with anti-parallel freewheeling diodes. The IGBT is a multiplexed switch tube. The front side of the converter is connected to a new energy power generation device, and the input power is direct current. The capacity of the inverter matches the capacity of the new energy power generation device and is slightly larger than the capacity of the power generation equipment. The output side is connected to the grid, and essentially provides alternating current power for the grid. The power synchronization link adopts grid-forming VSG control. The mathematical model of the converter output power is written based on the relationship between the voltage signal generated by grid-forming power control, the voltage at the point of common coupling (PCC point), and the line impedance. When the grid-connected system of the grid-forming converter operates stably, the steady-state operating parameters of the system are measured, and the relationship matrix is deduced from the active power, reactive power, and the generated voltage signal. The line impedance parameters are estimated through a state observer.

[0086] Further specifically, in step S1, (as Figure 2 shown) the grid-connected system of the grid-forming converter consists of a voltage source bridge formed by IGBTs, an LC filter, and a line impedance; the power synchronization part of the grid-forming converter is composed of VSG control. The active power loop has damping D and inertia J, simulating the mechanical motion equation of a synchronous generator, enabling the system to have frequency support ability, and the reactive power loop retains the droop characteristic. Its specific expression is:

[0087]

[0088] where, P m , P e represent the mechanical power and electromagnetic power of the system respectively, ω and ω n represent the angular frequency of the system and the rated angular frequency respectively; J and D represent the virtual moment of inertia and the system damping coefficient of the synchronous generator simulated in the VSG strategy respectively; δ represents the phase of the generated excitation electromotive force, which is called the power angle in this application.

[0089] In the related art, it is default that the transmission lines are purely inductive, and the impedance angle between the lines can be considered as 90°. In order to accurately describe the output power characteristics of the grid-forming converter in medium- and low-voltage lines, this application considers the coexistence of line resistance and reactance. The terminal potential E of the converter controlled by the grid-forming VSG is a controllable quantity, the grid voltage U and the transmission current I between the lines are given quantities, and the corresponding information can be obtained by the sampling measurement module in the simulation platform. In practice, the terminal voltage amplitude and phase angle can be sampled by the synchronous vector measurement device (phasormeasurement unit) at the busbar. The difference between the phase angle of the terminal voltage E and the phase angle of the grid voltage U is regarded as the power angle, which is marked with the symbol deta. A mathematical model of the grid-forming output power is constructed, and its specific expression is:

[0090]

[0091] Among them, P and Q respectively represent the active power and reactive power output by the grid-forming converter; E and U respectively represent the terminal voltage of the inverter and the grid connection point voltage; φ represents the line impedance angle; X eq 、R eq respectively represent the equivalent inductance and equivalent resistance of the line.

[0092] The power monitoring module is responsible for measuring the active power and reactive power output of the energy storage system in real time. In this application, it mainly refers to a calculation program or device that can perform power calculation. By monitoring the power flow at the grid connection point, this module can help the system understand the current power exchange situation, so as to accurately adjust the output of active power and reactive power, and ensure the stable operation of the system and coordination with the grid.

[0093] The static operating point of the grid-forming converter can well reflect the rated operating state of the system. The static operating voltage Es represents the amplitude of the electromotive force at the terminal busbar of the grid-forming converter, δs represents the phase angle of the terminal busbar electromotive force of the grid-forming converter, Ps represents the value of the active power output by the grid-forming converter during steady-state operation, and Qs represents the value of the reactive power output by the grid-forming converter during steady-state operation. The above values are all constant values and can be obtained by sampling with measuring equipment. The acquisition method is simple and the cost is low.

[0094] Similarly, using the voltage vector and current vector collected by the synchronous vector measurement device (phasormeasurement unit) at the busbars on the grid-forming converter side and the grid connection point side, the sampling frequency needs to meet the Nyquist sampling theorem to ensure signal integrity. A robust state observer is designed to estimate the current and voltage states of the line online. The specific expression of the state estimation process is:

[0095]

[0096] Among them, For the observation state, L is the observer gain matrix, which is designed through optimal control theory.

[0097] Using the output of the state observer and combining the recursive least squares method, estimate the resistance R of the line line and reactance X line , and the specific expression is:

[0098] θ = [R, X] T

[0099] θ k+1 = θ k + L k (y k - φ k T θ k )

[0100] where L k is the gain matrix, and f aik is the input-output state provided by the state observer.

[0101] According to the real-time measurement data, dynamically adjust the observer parameter L to improve the system robustness and accuracy. The state observer has the advantages of strong robustness and high real-time performance in measuring the line impedance parameters. Its result accuracy is affected by the measuring device, and the final result can be fed back to the power grid control system online. R line and X line are updated in real time to achieve intelligent monitoring and optimal scheduling.

[0102] Combined with Figure 4 , the output power relationship matrix of the grid-forming VSG control will be used for the subsequent program calculation of this application, and the specific expression is:

[0103]

[0104] The output power depends on the P-f and Q-U characteristics. In the relationship matrix, is used as the non-coupled quantity of the output power, which is characterized as the direct power representation under the independent control part; is the coupled quantity of the output power, that is, the quantity to be decoupled of the output power. In order to meet the independent control of active power and reactive power, the coupled quantity should be weakened from two aspects, which are the impedance angle caused by the line impedance and the amplitude and phase angle fluctuations of the generated voltage signal on the grid-forming converter side.

[0105] The specific method in step S2 is:

[0106] The line impedance estimated in step S1 is directly used for the calculation of the virtual negative resistance value Rv and the virtual inductance value Lv in this application. Since the line impedance parameter estimation process is limited by the accuracy of the general monitoring module or detection equipment, the measurement results are always updated in real time and time-varying. Therefore, there is an impedance offset phenomenon. If the equivalent value after the system accesses the virtual resistor Rv is less than zero, it may cause system instability. In addition, due to the existence of parasitic resistance in the actual line, the transmission line will not present pure inductance. In engineering, a transmission line with a resistance-inductance ratio less than 0.12 can be regarded as an inductive line. This application provides a setting method for the virtual negative resistance Rv. The value of the virtual negative resistance should avoid this situation, that is, the virtual negative resistance value Rv should be less than the sum of the actual output resistance and the line resistance. The method needs to be applicable to general detection equipment and general measurement accuracy, and the maximum offset in the actual environment does not exceed 10%. The specific expression of the virtual negative resistance Rv setting method is:

[0107]

[0108] Combined with Figure 5 , the bus voltage vector E and the line current vector I on the grid-forming converter side collected in step S1 are transformed from the time domain to the two-phase rotating coordinate through the Park transformation. This transformation enables the time-varying voltage and current vectors to be transformed into constant values for calculation, avoiding the complex control of three-phase alternating quantities and having the characteristics of simplicity and easy control. The virtual voltage drop generated by calculating the virtual impedance with the set virtual impedance value is as follows:

[0109]

[0110] Among them, E d* , E q* are the d-axis and q-axis voltage reference values after passing through the virtual impedance link respectively; E d , E q are the d-axis and q-axis reference values of the virtual electromotive force respectively, and I d , I q are the d-axis and q-axis inductor currents respectively.

[0111] The voltage signal after the first feed-in of the virtual voltage drop is then transformed back to the three-phase coordinate system through the inverse Park transformation. The virtual negative resistance is introduced to eliminate the resistance component in the inverter sending-end output impedance and the line impedance, and the virtual inductance is used to further increase the equivalent impedance angle of the system, so as to decouple the transmission power caused by the impedance angle.

[0112] The specific method in step S3 is as follows:

[0113] From E in step S2 d* , E q*The transformed three-phase voltage signal E is controllable and measurable. The system static operating point calculated by step S1 is as follows:

[0114] The static operating voltage amplitude Es and phase angle δs at the terminal bus of the grid-forming converter, the active power value Ps and reactive power value Qs output by the grid-forming converter during steady-state operation. Assuming that the reactive power command is constant and the active power undergoes a step change at a certain moment, the active power control will increase the phase angle to track the active power command. Since the reactive power command does not change, the reactive power control passively reduces the voltage amplitude through feedback. This feedback is limited by the bandwidth of the power loop, resulting in system delay in response and thus reactive power fluctuations. Similarly, assuming that the active power command remains unchanged and the reactive power undergoes a step change, the reactive power loop will increase the voltage amplitude to track the reactive power command, then the active power loop will reduce the phase angle through the feedback mechanism to maintain the stability of the active power. Due to the delayed response, there will still inevitably be fluctuations in the active power during this process.

[0115] To achieve decoupled power control, fundamentally, it is to minimize the non-diagonal elements in the relationship matrix. Therefore, this paper proposes to introduce a power angle feedforward term (as shown in Figure 6 ) in the active power control loop and introduce an amplitude feedforward term in the reactive power control loop to cancel the inherent power coupling relationship. The purpose of this minimization is to ensure that the active power is mainly affected by the phase difference and the reactive power is mainly affected by the voltage amplitude, enhancing the P-f and Q-U characteristics of the VSG system. The specific expression of the decoupled control is:

[0116]

[0117] where Δδ and ΔE are the fluctuations in the phase angle and amplitude of the potential on the grid-forming converter side, respectively.

[0118] When the voltage phase angle is difficult to measure, the compensation amounts of the voltage amplitude and phase angle compensation can also be equivalently characterized by the line impedance. The specific expression is:

[0119]

[0120] In the feedforward compensation, the voltage amplitude ΔE and the change in the power angle Δδ are system measurement values, that is, the differentials of the voltage signal amplitude and phase angle. In actual measurement, it is difficult to capture the change in the phase angle. And considering the inherent integral relationship between the phase and frequency, the phase difference detection can also be converted into frequency detection, and the generated phase feedforward can also be converted into frequency feedforward, which is equivalent to directly introducing the VSG side frequency quantity for comparison with the grid frequency. The feedforward quantities ΔE f and Δδ fThe calculation is based on the system state and external disturbances in the current sampling period and is only valid in the current current control period. Therefore, there is a time delay effect in data compensation in practical applications, and an integral link is added to the continuous system to ensure the continuous effectiveness of the feedforward value throughout the control process. The calculated feedforward value of the voltage amplitude ΔE f and the feedforward of the power angle Δδ f are compensated to E if and δ if . The obtained secondary compensation value (second feed) E sf and δ sf . The specific expression of the compensated voltage signal is:

[0121]

[0122] Feedforward control can quickly compensate when the power or voltage signal changes, reducing the response delay and adjustment time of the system. This fast response characteristic is particularly important in the case of load fluctuations or unstable photovoltaic output, which helps to improve the dynamic performance of the system.

[0123] The specific method in the step S4 is as follows:

[0124] The voltage signal after composite feedforward is used as a reference value and first participates in the decoupling control of the filter inductor current. The reference voltage E sfdq is converted into the target inductor current I Ldq . In this process, the coupling term of the filter inductor is dynamically compensated, thereby eliminating the cross influence between the d-axis and q-axis currents, ensuring the consistency between the inductor current and the voltage reference value, and improving the control accuracy and dynamic performance of the system. Subsequently, the decoupled inductor current signal is further used for the decoupling control of the filter capacitor voltage. By dynamically compensating the capacitor voltage, the final target output voltage V odq is calculated. This decoupling process effectively reduces the voltage fluctuation caused by the nonlinear dynamic characteristics of the capacitor, ensuring the smoothness and fast response ability of the output voltage.

[0125] The decoupled target voltage signal V odq is converted into a three-phase instantaneous reference voltage V oabc , and is input into the space vector pulse width modulation (SVPWM) algorithm to generate three-phase PWM control signals Sa, Sb, Sc for driving the power switch devices of the inverter. SVPWM makes the output voltage waveform close to sine by optimizing the switching sequence, while reducing the harmonic distortion rate, ensuring high-precision regulation of the inverter output voltage in terms of amplitude, frequency and phase. In addition, the generated PWM signal drives the conduction and turn-off of the power switch devices, thereby realizing precise control of the inverter output voltage and current.

[0126] To ensure the security and stability of the system, the circuit dynamically compares the voltage and current signals at the output terminal through real-time sampling, forms a closed-loop feedback regulation mechanism with the reference signal. At the same time, a protection module is added to the system. When abnormal conditions such as overvoltage, overcurrent or short circuit are detected, the PWM signal is automatically adjusted or cut off to prevent damage to the power devices and ensure the stable operation of the system. Through this series of steps, the combined feedforward combines the decoupling control of the filter inductor and capacitor with PWM modulation, and finally realizes the efficient, stable and safe control of the inverter operating state.

[0127] Embodiment 2:

[0128] The method for decoupling the grid-connected output power of an inverter based on the grid-forming VSG control proposed by the present invention includes a grid-forming VSG power control module, a grid parameter detection unit, a line impedance observer, a virtual impedance voltage drop feedforward loop, and a voltage signal secondary feedforward loop.

[0129] Specifically, the grid-forming VSG power control module realizes the precise regulation of active power and reactive power by simulating the rotor motion equation of a synchronous generator to improve the dynamic response and operating stability of the system. This control strategy is based on the P-f and Q-U droop characteristics, controls the active power output through frequency regulation, and realizes the dynamic balance of reactive power by voltage regulation. The system adopts a virtual inertia and virtual damping mechanism, combined with a double closed-loop control structure (including a power loop and a voltage loop), enabling the inverter to provide inertial support and voltage stability for the power grid.

[0130] Specifically, the line impedance observer realizes the online measurement and dynamic observation of the line impedance parameters by collecting the grid voltage and current signals in real time and combining with a state estimation algorithm. A state space model is constructed to characterize the dynamic characteristics of the line, and the equivalent resistance and reactance values of the line impedance are estimated with high precision by the least squares method. The line impedance observer has high robustness and fast response ability, can adapt to complex grid environments, and provides key support for system stability and control optimization.

[0131] Specifically, the virtual impedance voltage drop feedforward loop simulates the impedance characteristics of the line by introducing a virtual resistance and a virtual inductor, compensates for the voltage drop of the inverter output voltage, thereby optimizing the equivalent impedance characteristics of the system. This loop actively calculates and compensates for the voltage changes caused by the line impedance during the control process, weakens the influence of voltage amplitude and power angle fluctuations on system stability, and further improves the power decoupling performance. Through virtual impedance voltage drop feedforward, the system can effectively suppress the power coupling problems caused by line parameter changes or load fluctuations, ensure the stable operation of the inverter in complex grid environments, and improve the dynamic response performance and power supply quality.

[0132] Specifically, the secondary feedforward loop of the voltage signal further compensates for the changes in voltage amplitude and phase angle, improving the system's adaptability to voltage fluctuations and control accuracy. Based on the primary feedforward compensation, this loop combines the real-time sampled voltage signal to make more precise dynamic adjustments to the system state, reducing the impact of voltage changes on power output. The secondary feedforward loop of the voltage signal can significantly weaken the power imbalance phenomenon caused by external disturbances or load fluctuations, further optimizing the power control performance, improving the system's dynamic response speed and stability, ensuring that the inverter output voltage always remains within the target range, and thus enhancing the power supply quality and reliability.

[0133] Specifically, the grid parameter monitoring unit realizes precise monitoring of the grid operation state by collecting key electrical parameters of the grid (such as voltage, current, frequency, and power) in real time. This unit consists of a sensing module, a signal processing module, and a data communication module. The sensing module uses voltage transformers and current transformers to sample the grid signal. The signal processing module extracts the effective value and harmonic components of the parameters through digital filtering and fast Fourier transform (FFT) technology. The data communication module uploads the processed parameters to the control system or cloud platform. The monitoring unit has high-frequency sampling ability and anomaly detection function, can quickly respond to fault states such as grid frequency deviation, voltage sag, or harmonic over-standard, and trigger corresponding protection mechanisms. At the same time, this unit supports multi-point distributed monitoring and realizes efficient data interaction with other devices through wireless communication or bus protocol, and is widely used in smart grid, distributed generation, and microgrid operation scenarios.

[0134] Example 3:

[0135] This embodiment provides a terminal device, which includes a processor and a memory. The memory is used to store a computer program, and the computer program includes program instructions. The processor is used to execute the program instructions stored in the computer storage medium. The processor may be a Central Processing Unit (CPU), or may also be other general-purpose processors, Digital Signal Processors (DSPs), Application Specific Integrated Circuits (ASICs), Field-Programmable Gate Arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, and is suitable for implementing one or more instructions. Specifically, it is suitable for loading and executing one or more instructions to implement the corresponding method flow or corresponding function. The processor described in the embodiments of the present invention can be used for the operation of a method for decoupling the output power of a grid-forming VSG based on voltage signal composite feedforward, including the following steps:

[0136] S1: Obtain grid parameters, system static parameters, and line impedance information, build a grid-forming VSG control grid-connection model, identify the line impedance from the VSG terminal bus to the grid-connection point bus through a state observer, construct a power relationship matrix, and calculate the steady-state operating point;

[0137] S2: Based on the line impedance parameters estimated in step S1, considering the actual offset coefficient, calculate the virtual negative resistance and inductance, and generate the first virtual voltage drop feedforward signal to adjust the VSG power synchronization link, thereby compensating for the influence of the line impedance on the power output;

[0138] S3: Collect the fluctuations in the amplitude and phase angle of the electromotive force after the first voltage feedforward. This feedforward signal provides a basis for the secondary feedforward compensation. Calculate the secondary feedforward value based on the system static operating point, and further adjust the voltage response to provide a stable voltage reference for the subsequent decoupling of current and voltage;

[0139] S4: The voltage signal after composite feedforward is used as a reference to participate in the decoupling of the filter inductor current and capacitor voltage. The decoupled voltage signal is used for SVPWM modulation to accurately control the operation of the inverter, and finally achieve stable power output and grid voltage.

[0140] Embodiment 4:

[0141] This embodiment provides a storage medium, specifically a computer-readable storage medium (Memory). The computer-readable storage medium is a memory device in a terminal device and is used to store programs and data. It can be understood that the computer-readable storage medium here can include both the built-in storage medium in the terminal device and, of course, the extended storage medium supported by the terminal device. The computer-readable storage medium provides a storage space, and this storage space stores the operating system of the terminal. Moreover, in this storage space, one or more instructions suitable for being loaded and executed by a processor are also stored. These instructions can be one or more computer programs (including program codes). It should be noted that the computer-readable storage medium here can be a high-speed RAM memory or a non-volatile memory, such as at least one disk memory.

[0142] One or more instructions stored in the computer-readable storage medium can be loaded and executed by a processor to implement the corresponding steps of the method for decoupling the output power of a grid-forming VSG based on voltage signal composite feedforward in the above embodiment; one or more instructions in the computer-readable storage medium are loaded and executed by the processor to perform the following steps:

[0143] S1: Obtain grid parameters, system static parameters, and line impedance information, build a grid-forming VSG control grid-connection model, identify the line impedance from the VSG terminal bus to the grid-connection point bus through a state observer, construct a power relationship matrix, and calculate the steady-state operating point;

[0144] S2: Based on the line impedance parameters estimated in step S1, considering the actual offset coefficient, calculate the virtual negative resistance and inductance, and generate the first virtual voltage drop feedforward signal to adjust the VSG power synchronization link, thereby compensating for the influence of the line impedance on the power output;

[0145] S3: Collect the fluctuations in the electromotive force amplitude and phase angle after the first voltage feedforward. This feedforward signal provides a basis for the secondary feedforward compensation. Calculate the secondary feedforward value based on the system static operating point, and further adjust the voltage response to provide a stable voltage reference for the subsequent decoupling of current and voltage;

[0146] S4: The voltage signal after composite feedforward is used as a reference to participate in the decoupling of the filter inductor current and capacitor voltage. The decoupled voltage signal is used for SVPWM modulation to precisely control the operation of the inverter, and finally achieve stable power output and grid voltage.

[0147] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a system, or a computer program product. Therefore, the present invention can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk memory, CD-ROM, optical memory, etc.) that contain computer-usable program code.

[0148] The present invention is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to embodiments of the present invention. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of flows and / or blocks in the flowcharts and / or block diagrams, can be realized by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing devices generate means for realizing the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0149] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory generate a manufactured article including instruction means that realize the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0150] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process, so that the instructions executed on the computer or other programmable device provide steps for realizing the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0151] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited to the above embodiments. Within the knowledge scope of those of ordinary skill in the art, various changes can be made without departing from the gist of the present invention.

[0152] Many other changes and modifications can be made without departing from the concept and scope of the present invention. It should be understood that the present invention is not limited to the specific embodiments, and the scope of the present invention is defined by the appended claims.

Claims

1. A decoupling method for the output power of a grid-forming VSG based on voltage signal composite feedforward, characterized in that, The method includes: S1: Obtain grid parameters, system static parameters, and line impedance information, build a grid-forming VSG control grid-connection model, identify the line impedance from the VSG terminal bus to the grid-connection point bus through a state observer, construct a power relationship matrix, and calculate the steady-state operating point; S2: Based on the line impedance parameters estimated in step S1, considering the actual offset coefficient, calculate the virtual negative resistance and inductance, and generate the first virtual voltage drop feedforward signal to adjust the VSG power synchronization link, thereby compensating for the influence of line impedance on power output; S3: Collect the fluctuations in the electromotive force amplitude and phase angle after the first voltage feedforward. This feedforward signal provides a basis for the secondary feedforward compensation. Calculate the secondary feedforward value based on the system static operating point, further adjust the voltage response, and provide a stable voltage reference for the subsequent decoupling of current and voltage; S4: Use the voltage signal after composite feedforward as a reference to participate in the decoupling of the filter inductor current and capacitor voltage. The decoupled voltage signal is used for SVPWM modulation to precisely control the operation of the inverter, and finally achieve stable power output and grid voltage.

2. The decoupling method for the output power of the grid-forming VSG based on voltage signal composite feedforward according to claim 1, wherein, The step S1 includes: The grid-forming converter grid-connection system consists of a bridge-type voltage source inverter composed of 4 IGBTs with anti-parallel freewheeling diodes, an LC filter, and a line impedance; the power synchronization part of the grid-forming converter is composed of VSG control. The active loop has damping D and inertia J, simulating the mechanical motion equation of a synchronous generator, enabling the system to have frequency support capabilities. The reactive loop retains the droop characteristic; its specific expression is: Among them, P m and P e represent the mechanical power and electromagnetic power of the system respectively, ω and ω n represent the angular frequency of the system and the rated angular frequency respectively; J and D represent the virtual moment of inertia and the system damping coefficient of the synchronous generator simulated in the VSG strategy; δ represents the phase of the generated excitation electromotive force, which is called the power angle; By default, the transmission lines are purely inductive, and the impedance angle between the lines can be considered 90°. To accurately describe the output power characteristics of the grid-forming converter in medium- and low-voltage lines, considering the coexistence of line resistance and reactance, the machine terminal potential E of the grid-forming VSG control converter is a controllable quantity, the grid voltage U and the line transmission current I are given quantities, and the corresponding information can be obtained by the sampling measurement module in the simulation platform. In practice, the terminal voltage amplitude and phase angle can be sampled by the synchronous vector measurement device at the bus. The phase angle difference between the machine terminal voltage E and the grid voltage U is regarded as the power angle δ. Construct the grid-forming output power mathematical model, and its specific expression is: wherein, P and Q respectively represent the active power and reactive power output by the network-forming converter; E and U respectively represent the inverter terminal voltage and the grid connection point voltage; φ represents the line impedance angle; X eq , R eq respectively represent the equivalent inductance and equivalent resistance of the line; The power monitoring module is responsible for real-time measurement of the active power and reactive power output of the energy storage system, referring to a calculation program or device capable of performing power calculations. By monitoring the power flow at the grid-connection point, this module helps the system understand the current power exchange situation, thereby precisely adjusting the output of active and reactive power to ensure the stable operation of the system and coordination with the grid; The static operating point of the network-forming converter can well reflect the rated operating state of the system. The static operating voltage Es represents the amplitude of the electromotive force at the busbar of the network-forming converter, δs represents the phase angle of the electromotive force at the busbar of the network-forming converter, Ps represents the active power value output by the network-forming converter during steady-state operation, and Qs represents the reactive power value output by the network-forming converter during steady-state operation. The above values are all constant values and can be obtained through sampling by measuring equipment. The voltage vector and current vector s are collected by the synchronous vector measurement device at the busbars on the network-forming converter side and the grid connection point side. The sampling frequency needs to meet the Nyquist sampling theorem to ensure signal integrity. A robust state observer is designed to estimate the current and voltage states of the line online. The state estimation process is specifically expressed as: wherein, is the observation state, i.e., the output state, y is the input state provided by the state observer, and L is the observer gain matrix, which is designed by the optimal control theory; Using the output of the state observer and combining with the recursive least squares method, estimate the resistance R of the line line and reactance X line , and the specific expression is as follows: θ = [R, X] T θ k+1 = θ k + L k (y k - φ k T θ k ) where, L k is the gain matrix; y k is the actual sampled data, φ k is the regressor, and θ k is the parameter to be estimated; According to the real-time measurement data, the observer parameter L is dynamically adjusted to improve the system robustness and accuracy; the accuracy of the result is affected by the measuring device, and the final result is fed back online to the power grid control system, R line and X line Updated in real time; The output power relationship matrix of the network-forming VSG-controlled converter will be used for subsequent program calculations, and the specific expression is: The output power depends on the P-f and Q-U characteristics. In the relationship matrix, As the uncoupled quantity of the output power, it is characterized as the direct power representation under the independent control part; It is the coupled quantity of the output power, that is, the output power to be decoupled. In order to meet the independent control of active power and reactive power, the coupled quantity should be weakened from two aspects They are, in sequence, the impedance angle caused by the line impedance and the amplitude and phase angle fluctuations of the generated voltage signal on the grid-forming converter side.

3. A decoupling method for the output power of a grid-forming VSG based on voltage signal composite feedforward according to claim 1, characterized in that, The step S2 includes: The impedance between lines estimated based on step S1 is directly used for the calculation of the virtual negative resistance value Rv and the virtual inductance value Lv. Considering the impedance offset phenomenon, if the equivalent value after the system accesses the virtual resistance Rv is less than zero, it may cause system instability. In addition, due to the existence of parasitic resistance in the actual line, the transmission line will not present pure inductance. In engineering, the impedance-inductance ratio A transmission line with an impedance-inductance ratio less than 0.12 can be regarded as an inductive line; using the setting method of the virtual negative resistance Rv, the value of the virtual negative resistance should avoid this situation, that is, the virtual negative resistance value Rv should be less than the sum of the actual output resistance and the line resistance. The method should be applicable to general detection equipment and general measurement accuracy, and the maximum offset in the actual environment does not exceed 10%. The specific expression of the virtual negative resistance Rv setting method is: The busbar voltage vector E on the network-forming converter side and the line current vector I collected in step S1 are transformed from the time domain to the two-phase rotating coordinate through the Park transformation; the virtual voltage drop generated by the virtual impedance is calculated with the set virtual impedance value. The specific expression of the virtual voltage drop is: Among them, E d* and E q* are the d-axis and q-axis voltage reference values after passing through the virtual impedance link respectively; E d and E q are the d-axis and q-axis reference values of the virtual electromotive force respectively, and I d and I q are the d-axis and q-axis inductor currents respectively; The voltage signal after the first feeding of the virtual voltage drop is then transformed back to the three-phase coordinate system through the inverse Park transformation. A virtual negative resistance is introduced to eliminate the resistance component in the output impedance of the inverter sending end and the line impedance, and the virtual inductor is used to further increase the equivalent impedance angle of the system, so as to decouple the transmission power caused by the impedance angle.

4. A decoupling method for the output power of a grid-forming VSG based on voltage signal composite feedforward according to claim 1, characterized in that, The step S3 includes: The three-phase voltage signal E obtained by the transformation in step S2 is controllable and measurable. According to the system static operating point calculated in step S1, the static operating voltage amplitude Es and phase angle δs at the busbar of the network-forming converter, as well as the active power Ps and reactive power Qs output during steady-state operation, are determined. Assume that the reactive power command is constant and the active power has a step change at a certain moment. Then the active power control will increase the phase angle to track the active power command. Since the reactive power command does not change, the reactive power control passively reduces the voltage amplitude through feedback. This feedback is limited by the bandwidth of the power loop, resulting in system delay in response and thus reactive power fluctuations. Similarly, assume that the active power command remains unchanged and the reactive power has a step change. The reactive power loop will increase the voltage amplitude to track the reactive power command, and then the active power loop will reduce the phase angle through the feedback mechanism to maintain the stability of the active power. s Then it is proposed that introducing a power angle feedforward term in the active power control loop and an amplitude feedforward term in the reactive power control loop can cancel the inherent power coupling relationship. The purpose of this minimization is to ensure that the active power is mainly affected by the phase difference and the reactive power is mainly affected by the voltage amplitude, enhancing the P-f and Q-U characteristics of the VSG system. The decoupling control specific expression is: Among them, Δδ and ΔE are the fluctuations of the electromotive force phase angle and amplitude on the network-forming converter side respectively; When the voltage phase angle is difficult to measure, the compensation amounts of the voltage amplitude and phase angle compensation are also equivalently characterized by the line impedance. The specific expression is: The variations of voltage amplitude ΔE and power angle Δδ in feedforward compensation are system measurement values, that is, the differentials of the voltage signal amplitude and phase angle. In actual measurement, it is difficult to capture the phase angle variation. Considering the inherent integral relationship between phase and frequency, the phase difference detection can also be transformed into frequency detection, and the generated phase feedforward can also be transformed into frequency feedforward, which is equivalent to directly introducing the frequency quantity on the VSG side to compare with the grid frequency. The feedforward quantity ΔE f and Δδ f are calculated based on the system state and external disturbances in the current sampling period and are only valid in the current current control period. Therefore, there is a time delay effect in data compensation in practical applications. An integral link is added in the continuous system to ensure that the feedforward value is continuously valid throughout the control process. The calculated voltage amplitude feedforward value ΔE f and power angle feedforward Δδ f are compensated to E if and δ if . The obtained secondary compensation values E sf and δ sf . The specific expression of the compensated voltage signal is as follows: Feedforward control can quickly compensate when the power or voltage changes, reducing the system response delay. This fast response characteristic is particularly important when the load fluctuates or the photovoltaic output is unstable, which helps to improve the dynamic performance of the system.

5. A decoupling method for the output power of a grid-forming VSG based on voltage signal composite feedforward according to claim 1, characterized in that The step S4 includes: The voltage signal after composite feedforward is used as a reference value, which first participates in the decoupling control of the filter inductor current. Through the decoupling equation, the reference voltage E sfdq is converted into the target inductor current I Ldq . During this process, the coupling term of the filter inductor is dynamically compensated to eliminate the cross influence between the d-axis and q-axis currents, ensuring that the inductor current is consistent with the voltage reference value and improving the system control accuracy and dynamic performance; Next, the decoupled inductor current signal is used for the decoupling control of the filter capacitor voltage, and the final target output voltage V is calculated through dynamic compensation. odq This decoupling process effectively reduces the voltage fluctuations caused by the non-linear dynamic characteristics of the capacitor, ensuring the stability and fast response ability of the output voltage. Subsequently, the decoupled target voltage signal V odq is converted into a three-phase instantaneous reference voltage V oabc , and is input into the space vector pulse width modulation algorithm, which generates three-phase PWM control signals S a , S b and S c . SVPWM optimizes the switching sequence to make the output voltage waveform close to a sine wave, while reducing the harmonic distortion rate, ensuring high-precision regulation of the inverter output voltage in terms of amplitude, frequency, and phase; To ensure the safety and stability of the system, the circuit dynamically compares the output voltage and current signals sampled in real time with the reference signal to form a closed-loop feedback regulation mechanism. At the same time, the system is equipped with a protection module that can automatically adjust or cut off the PWM signal when detecting abnormal states such as overvoltage, overcurrent, or short circuit, to prevent damage to power devices and ensure the stable operation of the system. Through the above steps, the decoupling control of the composite feedforward and the filter inductance and capacitance, combined with SVPWM modulation, finally realizes the efficient, stable, and safe control of the inverter operating state.

6. A decoupling system for the output power of a grid-forming VSG based on voltage signal composite feedforward, characterized in that, The system is used to execute the method described in any one of claims 1-5. The system includes: a grid parameter detection unit, a line impedance observer, a voltage signal secondary feedforward loop, a virtual impedance voltage drop feedforward loop, and a grid-forming VSG power control module; adopting a grid-forming VSG control architecture, the grid parameter detection unit real-time collects voltage, current, and frequency signals, and the line impedance observer online estimates the line parameters; the virtual impedance voltage drop feedforward loop simulates the line impedance characteristics for voltage drop compensation, and the voltage signal secondary feedforward loop further adjusts the influence of voltage changes on power; the grid-forming VSG power control module realizes the decoupling control of active and reactive power based on the P-f and Q-U droop characteristics, combined with virtual inertia and a double closed-loop structure, significantly improving the dynamic response ability and grid support performance of the inverter.

7. A decoupling system for the output power of a grid-forming VSG based on voltage signal composite feedforward according to claim 6, characterized in that The grid parameter detection unit collects key electrical parameters of the grid through voltage transformers and current transformers. The signal processing module extracts the effective value and harmonic information based on digital filtering and fast Fourier transform. The data communication module uploads the processing results to the control system or the cloud platform. This unit supports high-frequency sampling, abnormal state detection, and can achieve multi-point distributed monitoring through wireless or bus protocols, and is applicable to smart grid, distributed generation, and microgrid application scenarios. The line impedance observer constructs a line state space model based on the voltage and current signals collected in real time and combines with state estimation algorithms to achieve online high-precision estimation of the equivalent resistance and reactance. This observer has high robustness and fast response ability, can adapt to complex grid environments, and provides basic support for subsequent compensation control and system stability. The voltage signal secondary feedforward loop, on the basis of primary compensation, further collects and analyzes the changes in voltage amplitude and phase angle, provides more accurate dynamic compensation, weakens the power imbalance caused by external disturbances or load fluctuations by adjusting the system state in real time, improves the voltage control accuracy and the system dynamic response speed, ensures that the inverter output voltage is stable within the set range, and improves the power supply reliability and power regulation performance of the system. The virtual impedance voltage drop feedforward loop simulates the line impedance characteristics by introducing a virtual resistor and an inductor to achieve voltage drop compensation for the inverter output voltage. It actively calculates the voltage change caused by the line impedance and implements compensation, effectively improving the system equivalent impedance characteristics and power decoupling performance, suppressing the power coupling problem caused by line parameter fluctuations or load disturbances, thereby enhancing the system stability and power supply quality; The grid-forming VSG power control module achieves precise regulation of active and reactive power by simulating the rotor motion equation of a synchronous generator, thereby improving the system dynamic response performance and operation stability. The control strategy adopts a double closed-loop structure based on P-f and Q-U droop characteristics, achieving active power output control through frequency regulation and reactive power balance through voltage regulation; introducing a virtual inertia and virtual damping mechanism to endow the inverter with inertia support and voltage regulation capabilities.

8. A computer device, characterized in that, It includes a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the program, it implements a grid-forming VSG output power decoupling method according to any one of claims 1 to 5.

9. A computer-readable storage medium, characterized in that, A computer program is stored on the computer-readable storage medium. When the program is executed by the processor, it implements a grid-forming VSG output power decoupling method according to any one of claims 1 to 5.

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