Optimization control method for improving power tracking precision of hybrid synchronous converter

Abstract

The invention discloses an optimal control method for improving the power tracking precision of a hybrid synchronous converter, and belongs to the field of power electronic technology and power system control. The invention provides an improved control strategy based on a series high-pass filter in order to solve the problem of low active power tracking precision caused by steady-state coupling of a voltage synchronization loop in existing hybrid synchronization control. According to the invention, the high-pass filter is connected in series in the voltage synchronization loop, continuous interference of a steady-state power angle to the frequency is blocked by utilizing the direct current blocking and alternating current alternating current characteristics of the high-pass filter, and the power synchronization loop independently dominates the steady-state frequency, so that the steady-state power error is thoroughly eliminated, and zero-static-error tracking is realized. And meanwhile, the response capability of the voltage synchronization loop to transient high-frequency disturbance is reserved, so that the excellent transient damping characteristic of the hybrid synchronization control strategy still exists. In addition, the method is simple in structure, does not need to depend on complex system parameter identification, and has high robustness and engineering adaptability.

Description

An optimized control method to improve the power point tracking accuracy of hybrid synchronous converters Technical Field

[0001] This invention relates to the fields of power electronics technology and power system control, and in particular to an optimized control method for improving the power tracking accuracy of hybrid synchronous converters, so as to improve the power tracking accuracy of hybrid control converters. Background Technology

[0002] In power grids with high penetration of new energy sources, hybrid synchronous control significantly improves the transient stability of grid-type converters under weak power grids and large disturbances by integrating a power synchronization loop that simulates the inertia of a synchronous machine and a voltage synchronization loop that provides electrical damping.

[0003] However, existing hybrid synchronous control architectures have an inherent drawback in practical applications: low steady-state power tracking accuracy. Traditional hybrid synchronous control voltage synchronization loops typically employ proportional feedback based on the voltage phase at the point of common coupling. According to the principle of synchronous transmission, when the converter outputs active power, there must be a non-zero steady-state power angle between its internal potential phase and the grid voltage phase. After passing through the proportional element of the voltage synchronization loop, this steady-state power angle continuously outputs a constant frequency bias signal. To maintain system frequency stability, the power synchronization loop is forced to generate a reverse power deviation to offset this frequency bias, resulting in the actual output active power failing to accurately track the reference value, thus producing an inherent steady-state error.

[0004] Currently, to address the issue of poor power tracking accuracy in hybrid synchronous control, existing technologies mainly focus on the following types of solutions: 1. The literature "Modified Hybrid Synchronization Control for GFM Inverters in Output Power Tracking, Oscillation Suppression, and Transient SynchronizationStability Improvement," W. Diao, in IEEE Access, vol. 13, pp. 144385-144396, 2025. This paper proposes an improved hybrid synchronous control scheme that includes power feedforward control. This method calculates the power angle deviation required for steady-state power command and injects it as feedforward, forcing the system to lock to the reference power balance point in steady state. Although this open-loop compensation can effectively reduce the steady-state error introduced by voltage synchronization, its accuracy is highly dependent on the real-time identification of grid impedance. If the identification is flawed, the feedforward logic will generate incorrect phase guidance, leading to an increase in tracking error. Meanwhile, while the low-pass filter modification of the voltage synchronization loop suppressed noise, it also sacrificed the dynamic response speed of the system under large disturbances.

[0005] 2. The paper "Physical Insight Into Hybrid-Synchronization-Controlled Grid-Forming Inverters Under Large Disturbances," T. Liu and X. Wang, in IEEE Transactions on Power Electronics, vol. 37, no. 10, pp. 11475-11480, Oct. 2022, reveals the physical nature of power deviation in hybrid synchronous control through a large-signal model and proposes to use a proportional-integral controller (PIC) in the power synchronization loop to replace the traditional droop control. This method utilizes the zero steady-state error characteristic of the integral element to eliminate the active power steady-state residual introduced by voltage synchronization from the control logic perspective. However, the introduction of the integral element results in a short critical fault clearing time for the inverter during grid faults, making it prone to loss of synchronization and significantly weakening the system's transient damping capability.

[0006] 3. The paper "Adaptive Grid-Synchronization Based Grid-Forming Control for Voltage Source Converters," H. Xiao, H. He, L. Zhang and T. Liu, in IEEE Transactions on Power Systems, vol. 39, no. 2, pp. 4763-4766, March 2024, proposes introducing an adaptive weighting coefficient to dynamically allocate power synchronization and voltage synchronization. When the coefficient favors power synchronization, power tracking accuracy improves; when the coefficient favors voltage synchronization, damping is enhanced. However, this method lacks a closed-loop elimination mechanism for steady-state power deviation. As long as the voltage synchronization loop has a gain coefficient, its effect will still lead to a static residual that cannot be eliminated between the output power and the reference value. In addition, the adaptive weighting coefficient is highly sensitive to system parameters and is prone to oscillations under complex operating conditions.

[0007] In summary, existing technologies have the following technical shortcomings in solving the power point tracking accuracy problem of hybrid synchronous control converters: 1. Reliance on complex parameters and models, resulting in poor robustness. Existing power feedforward compensation-based technical solutions heavily depend on the accurate acquisition of system parameters such as grid impedance. However, actual grid parameters are time-varying and uncertain; deviations in these parameters will directly lead to compensation failure, not only failing to eliminate steady-state errors but also potentially causing system oscillations due to improper compensation.

[0008] 2. Sacrificing transient stability for steady-state accuracy. While PI control in the power synchronization stage can eliminate steady-state errors, the phase lag introduced by the integral significantly weakens the system's transient damping capability. This leads to a shortened critical fault clearing time for the converter when facing grid faults, making it highly susceptible to out-of-synchronization oscillations, thus defeating the original intention of using hybrid synchronization control to enhance system stability.

[0009] 3. The control strategy is complex, making it difficult to balance accuracy and dynamic performance. Existing schemes using adaptive weight adjustment attempt to achieve a dynamic balance between power synchronization and voltage synchronization. However, this method lacks a fundamental closed-loop elimination mechanism for steady-state power deviation. As long as there is gain in the voltage synchronization loop, its output frequency correction signal will cause a static residual that cannot be eliminated by itself between the output power and the reference value. In addition, the adaptive weight coefficient is highly sensitive to system parameters, and improper adjustment under complex operating conditions can easily lead to system oscillations. Summary of the Invention

[0010] The technical problem this invention aims to solve is overcoming the limitations of existing hybrid synchronous control technologies in balancing power point tracking accuracy and transient damping. Specifically, this invention provides an optimized control method to improve the power point tracking accuracy of hybrid synchronous converters. This method eliminates the interference of the voltage synchronization loop on the steady-state power operating point by connecting a high-pass filter in series in the voltage synchronization loop, utilizing its DC blocking and AC passing characteristics. This achieves zero steady-state error tracking of active power while retaining the damping effect of the voltage synchronization loop during transient processes.

[0011] The technical solution of the present invention is as follows.

[0012] An optimized control method for improving the power point tracking accuracy of a hybrid synchronous converter, wherein the hybrid synchronous converter includes a DC-side voltage source, a three-phase full-bridge inverter, a three-phase LCL filter, a three-phase line equivalent inductance, and a three-phase power grid connected in series in sequence; the optimized control method includes the following steps: Step 1, acquiring the point of common coupling voltage v of the hybrid synchronous converter. PCCa ,v PCCb ,v PCCc and three-phase grid current i ga i gb i gc Step 1: Based on instantaneous power theory, the actual output active power P and reactive power Q of the converter are calculated; Step 2: Based on power synchronization control, according to the active power reference value P... ref The deviation from the actual output active power P is used to calculate the power synchronization angular frequency compensation amount Δω. PSC Step 3: Based on voltage synchronization control, a high-pass filter with a preset cutoff frequency is connected in series in the voltage synchronization loop, and the voltage synchronization angular frequency compensation amount Δω is generated through the voltage synchronization loop after connecting the high-pass filter in series. VBS Step 4, adjust the power synchronization angular frequency compensation amount Δω PSC The voltage synchronization angular frequency compensation amount Δω VBS The total angular frequency ω is obtained by superimposing the rated angular frequency ω0 of the power grid. HSC For the total angular frequency ω HSC By performing integration, the hybrid output phase θ of the converter is obtained. HSC Step 5, by mixing the output phase θ HSC For the common point of connection voltage v of the hybrid synchronous converter PCCa ,v PCCb ,v PCCc and three-phase grid current i ga i gb i gc Perform a dq coordinate transformation to obtain the dq component v of the voltage at the point of common coupling. PCCd ,v PCCqand the three-phase grid-connected current dq component i gd i gq Step 6, based on the reactive power reference value Q ref Reactive power Q and rated voltage reference value V ref Generate an internal potential amplitude command E; then use the internal potential amplitude command E and the common coupling point voltage dq component v PCCd ,v PCCq The dq axis current reference command i is calculated. d,ref i q,ref Step 7, set the dq axis current reference command i d,ref i q,ref Three-phase grid-connected current dq component i gd i gq and the voltage dq component at the point of common coupling v PCCd ,v PCCq After being controlled by the inner current loop, the modulated wave dq component v is obtained. md ,v mq Then, using the mixed output phase θ HSC Inverse transformation yields the three-phase modulated wave v ma ,v mb ,v mc And by using pulse width modulation, a corresponding switching signal is generated to drive the operation of the hybrid synchronous converter.

[0013] Preferably, the expressions for the actual output active power P and reactive power Q in step 1 are: .

[0014] Preferably, the power synchronization control in step 2 adopts a second-order virtual synchronous machine model, and the expression of its rotor motion equation is as follows:

[0015] In the formula, J is the virtual moment of inertia, and D... p P is the virtual damping coefficient. ref Here, s is the active power reference value, and s is the Laplace operator; the power synchronization angular frequency compensation Δω is obtained through this rotor motion equation. PSC .

[0016] Preferably, the implementation process of step 3 is as follows: Step 3.1, the voltage synchronization loop is set to proportional control only, and the proportional coefficient is K. p,PLL Step 3.2: Connect a high-pass filter in series in the voltage synchronization loop that only uses proportional control. HPF (s) is the transfer function of the high-pass filter, and its expression is:

[0017] In the formula, s is the Laplace operator, ωc The cutoff angular frequency of the high-pass filter; Step 3.3, obtain the voltage synchronization angular frequency compensation amount Δω generated by the voltage synchronization loop after the series high-pass filter. VBS Its expression is:

[0018] In the formula, v PCCq’ This is the q-axis component of the common connection point voltage from the previous control cycle.

[0019] Preferably, the total angular frequency ω in step 4 HSC The mixed output phase θ of the converter HSC The calculation formulas are as follows:

[0020] Where s is the Laplace operator.

[0021] Preferably, the implementation process of step 6 is as follows: Step 6.1, the reactive power reference value Q is... ref The result of subtracting the reactive power Q is multiplied by the reactive power droop factor n, and then fed forward with a rated voltage reference amplitude V. ref The internal potential amplitude command E is generated, and its expression is:

[0022] Step 6.2, using a virtual resistor R v With virtual inductance L v The virtual admittance control loop generates the inner loop current reference command for the dq-axis current. d,ref i q,ref The control law of the virtual admittance control loop is:

[0023] Where s is the Laplace operator.

[0024] Preferably, the modulation wave dq component v in step 7 md ,v mq The formula for calculation is:

[0025] Where s is the Laplace operator, K pc K is the proportional coefficient of the inner current loop in PI control. ic L1 is the integral coefficient of the inner current loop using PI control, and L1 is the inductance value of the inverter-side inductor in the three-phase LCL filter; the three-phase modulation wave v ma ,v mb ,v mc The transformation formula is: .

[0026] Compared with existing technologies, this invention has the following advantages: 1. It completely eliminates the steady-state error of power point tracking, achieving high-precision control. This invention uses a high-pass filter connected in series in the voltage synchronization loop, utilizing the high-pass filter's blocking characteristic for DC components to ensure that the output of the voltage synchronization loop is zero during steady-state operation. This allows the power synchronization loop to independently dominate the steady-state frequency, thereby ensuring that the actual output power is strictly equal to the reference value, fundamentally solving the power deviation problem caused by loop coupling in traditional hybrid synchronization control.

[0027] 2. It maintains excellent transient damping characteristics. When transient disturbances such as frequency changes or phase jumps occur in the power grid, the phase difference exhibits high-frequency variation characteristics. The high-pass filter allows this high-frequency component to pass through, and the voltage synchronization loop can still quickly output a frequency compensation signal, playing a role similar to the damping winding of a synchronous generator, effectively suppressing power oscillations and maintaining the stability advantage of hybrid synchronous control under weak power grid conditions.

[0028] 3. The method is simple and reliable, and does not depend on system parameters. This invention only requires adding a simple filter to the control loop, without the need for complex grid impedance identification or adaptive parameter adjustment algorithms. It is simple to implement in engineering and has strong robustness. Attached Figure Description

[0029] Figure 1 is a topology diagram of the hybrid synchronous converter in this invention.

[0030] Figure 2 is a block diagram of the optimized hybrid synchronization loop control of the voltage synchronization loop series high-pass filter described in this invention.

[0031] Figure 3 is a block diagram of the virtual admittance control loop described in this invention.

[0032] Figure 4 shows a power comparison waveform between the control method of the present invention and the conventional hybrid synchronous control during a power command step in the simulation.

[0033] Figure 5 shows the waveforms of the three-phase voltage and three-phase grid-connected current at the common connection point of the optimized hybrid synchronous control converter system described in this invention during simulation.

[0034] Figure 6 shows the local magnified waveforms of the three-phase voltage and three-phase grid-connected current at the common connection point of the optimized hybrid synchronous control converter system described in this invention during simulation.

[0035] Figure 7 shows the power response waveforms of the optimized hybrid synchronization control and the conventional grid-type control when a phase jump occurs in the power grid during the simulation.

[0036] Figure 8 is a schematic diagram of the overall flow of the control method of the present invention. Detailed Implementation

[0037] The technical solution of the present invention will now be clearly and completely described in conjunction with the accompanying drawings.

[0038] Figure 1 is a topology diagram of the hybrid synchronous converter in this invention. As can be seen from Figure 1, the hybrid synchronous converter of this invention includes a DC-side voltage source, a three-phase full-bridge inverter, a three-phase LCL filter, a three-phase line equivalent inductance, and a three-phase power grid connected in series in sequence.

[0039] As shown in Figure 1, the three-phase LCL filter is an LCL filter with passive damping resistor, including bridge arm-side inductor L1, filter capacitor, and capacitor-side series damping resistor R. d And the grid-side inductor L2. Where L1 is the inductance of the bridge arm-side inductor, C is the capacitance of the filter capacitor, and R... d L1 is the resistance value of the series damping resistor on the capacitor side, and L2 is the inductance value of the grid-side inductor.

[0040] Additionally, in Figure 1, v dc L is the output voltage of the DC-side voltage source. g The inductance value is the equivalent inductance of the three-phase line, and the three-phase output voltage of the inverter is v. inv,abc The three-phase grid-connected current is i g,abc v PCC,abc The three-phase voltage at the point of common coupling, v g,abc This is the voltage of the three-phase power grid.

[0041] In this embodiment, v is taken as dc =800V, L1=0.9mH, C=11.6μF, R d =2Ω, L2=0.2mH, L g =11.5mH, v g,abc =380V. In addition, the rated output line voltage of the converter is 380V / 50Hz, and the rated power is 20kW.

[0042] Figure 8 is a schematic diagram of the overall flow of the control method of the present invention. As shown in the figure, it is first necessary to synchronously acquire the common coupling point voltage and output current signals required for the control of the hybrid synchronous converter, and calculate the active power P and reactive power Q. Subsequently, the power synchronization angular frequency compensation Δω is generated using a power synchronization loop based on a virtual synchronous machine strategy. PSC In the voltage synchronization loop with a series high-pass filter, a voltage synchronization angular frequency compensation amount Δω is generated. VBS The internal potential amplitude command E is generated through the reactive power control loop. The obtained Δω... PSC With Δω VBS The mixed phase angle θ is obtained after synthesis and processing. HSC The sampled quantity is then transformed into dq coordinates and then sequentially passed through virtual admittance control and current loop control to finally generate modulation voltage and switching signals, thus completing the closed loop of the entire control system.

[0043] Specifically, the optimized control method includes the following steps: Step 1, acquiring the common coupling point voltage v of the hybrid synchronous converter. PCCa ,v PCCb ,v PCCc and three-phase grid current i ga i gb i gc The actual output active power P and reactive power Q of the converter are calculated based on instantaneous power theory.

[0044] In this embodiment, the expressions for the actual output active power P and reactive power Q in step 1 are: .

[0045] Step 2, based on power synchronization control, according to the active power reference value P ref The deviation from the actual output active power P is used to calculate the power synchronization angular frequency compensation amount Δω. PSC .

[0046] In this embodiment, the power synchronization control adopts a second-order virtual synchronous machine model, and the expression of its rotor motion equation is as follows:

[0047] In the formula, J is the virtual moment of inertia, and D... p P is the virtual damping coefficient. ref Here, s is the active power reference value, and s is the Laplace operator; the power synchronization angular frequency compensation Δω is obtained through this rotor motion equation. PSC .

[0048] In this embodiment, J=0.8106, D p =6366.2, P ref =20000.

[0049] Step 3: Based on voltage synchronization control, a high-pass filter with a preset cutoff frequency is connected in series in the voltage synchronization loop, and the voltage synchronization angular frequency compensation amount Δω is generated through the voltage synchronization loop after connecting the high-pass filter in series. VBS .

[0050] In this embodiment, the implementation process of step 3 is as follows: Step 3.1, the voltage synchronization loop is set to proportional control only, and the proportional coefficient is K. p,PLL Step 3.2: Connect a high-pass filter in series in the voltage synchronization loop that only uses proportional control. HPF (s) is the transfer function of the high-pass filter, and its expression is:

[0051] In the formula, s is the Laplace operator, ω c The cutoff angular frequency of the high-pass filter; Step 3.3, obtain the voltage synchronization angular frequency compensation amount Δω generated by the voltage synchronization loop after the series high-pass filter. VBS Its expression is:

[0052] In the formula, v PCCq’ This is the q-axis component of the common connection point voltage from the previous control cycle.

[0053] In this embodiment, K is taken as... p,PLL =0.1391, ω c =6.28 radians / second.

[0054] Figure 2 is the control chart for step 3.

[0055] Step 4, adjust the power synchronization angular frequency compensation amount Δω PSC The voltage synchronization angular frequency compensation amount Δω VBS The total angular frequency ω is obtained by superimposing the rated angular frequency ω0 of the power grid. HSC For the total angular frequency ω HSC By performing integration, the hybrid output phase θ of the converter is obtained. HSC .

[0056] In this embodiment, the total angular frequency ω HSC The mixed output phase θ of the converter HSC The calculation formulas are as follows:

[0057] Where s is the Laplace operator.

[0058] In this embodiment, ω0 = 314 radians / second.

[0059] Step 5, by mixing the output phase θ HSC For the common point of connection voltage v of the hybrid synchronous converter PCCa ,v PCCb ,v PCCc and three-phase grid current i ga i gb i gc Perform a dq coordinate transformation to obtain the dq component v of the voltage at the point of common coupling. PCCd ,v PCCq and the three-phase grid-connected current dq component i gd i gq .

[0060] Step 6, based on the reactive power reference value Q refReactive power Q and rated voltage reference value V ref Generate an internal potential amplitude command E; then use the internal potential amplitude command E and the common coupling point voltage dq component v PCCd ,v PCCq The dq axis current reference command i is calculated. d,ref i q,ref .

[0061] In this embodiment, the implementation process of step 6 is as follows: Step 6.1, set the reactive power reference value Q... ref The result of subtracting the reactive power Q is multiplied by the reactive power droop factor n, and then fed forward with a rated voltage reference amplitude V. ref The internal potential amplitude command E is generated, and its expression is:

[0062] Step 6.2, using a virtual resistor R v With virtual inductance L v The virtual admittance control loop generates the inner loop current reference command for the dq-axis current. d,ref i q,ref The control law of the virtual admittance control loop is:

[0063] Where s is the Laplace operator.

[0064] In this embodiment, R v =0.1pu, L v =0.2pu, where pu is a per-unit unit, and n=0.00077567.

[0065] Figure 3 is a block diagram of the virtual admittance control loop described in this invention.

[0066] Step 7, set the dq axis current reference command i d,ref i q,ref Three-phase grid-connected current dq component i gd i gq and the voltage dq component at the point of common coupling v PCCd ,v PCCq After being controlled by the inner current loop, the modulated wave dq component v is obtained. md ,v mq Then, using the mixed output phase θ HSC Inverse transformation yields the three-phase modulated wave v ma ,v mb ,v mc And by using pulse width modulation, a corresponding switching signal is generated to drive the operation of the hybrid synchronous converter.

[0067] In this embodiment, the modulated wave dq component v md ,v mq The formula for calculation is:

[0068] Where s is the Laplace operator, K pc K is the proportional coefficient of the inner current loop in PI control. ic L1 is the integral coefficient of the inner current loop using PI control, and L1 is the inductance value of the inverter-side inductor in the three-phase LCL filter; the three-phase modulation wave v ma ,v mb ,v mc The transformation formula is: .

[0069] In this embodiment, K is taken as... pc =4,K ic =10, L1=0.9mH.

[0070] To demonstrate the beneficial effects of the present invention, simulations were performed.

[0071] Figure 4 is a power comparison waveform diagram of the control method of this invention and conventional hybrid synchronous control at the power command step in the simulation of this invention, where P ref The power command is given by stepping 0.2 pu at 20 seconds, 30 seconds, 40 seconds, and 50 seconds respectively. P1 is the output power waveform of the optimized hybrid synchronous converter with the voltage synchronization loop series high-pass filter, and P2 is the output power waveform of the conventional hybrid synchronous converter. As can be seen from the figure, the optimized hybrid synchronization strategy proposed in this invention can enable the converter's output power to accurately follow the power command value.

[0072] Figures 5 and 6 show the three-phase voltage and three-phase grid-connected current waveforms and the local magnified waveforms at the common connection point of the optimized hybrid synchronous control converter system described in this invention. The voltage and current waveforms remain stable before and after the power step, without any instability. Furthermore, the output current waveform of the converter is well-formed and maintains a good sine wave shape, as can be seen in the magnified regional diagram.

[0073] Figure 7 shows the power response waveforms of the optimized hybrid synchronous control and the conventional grid-type control when the power grid experiences a phase jump in the simulation of this invention. The simulation sets the three-phase power grid to experience a 10-degree phase jump at 10 seconds and return to normal at 13 seconds. P3 is the output power waveform of the optimized hybrid synchronous converter with a series high-pass filter in the voltage synchronization loop, and P4 is the output power waveform of the conventional grid-type control converter. As can be seen from the figure, the optimized hybrid synchronous strategy proposed in this invention can achieve a faster power convergence speed than the conventional grid-type control under large disturbances such as phase jumps in the power grid. This indicates that the proposed optimized hybrid synchronous control still retains a certain damping capability of hybrid synchronous control, which is beneficial to the transient stability of the system.

Claims

1. An optimized control method for improving the power point tracking accuracy of a hybrid synchronous converter, wherein the hybrid synchronous converter comprises, in sequence, a DC-side voltage source, a three-phase full-bridge inverter, a three-phase LCL filter, a three-phase line equivalent inductance, and a three-phase power grid; characterized in that, The optimized control method includes the following steps: Step 1, acquiring the common coupling point voltage v of the hybrid synchronous converter. PCCa ,v PCCb ,v PCCc and three-phase grid current i ga i gb i gc Step 1: Based on instantaneous power theory, the actual output active power P and reactive power Q of the converter are calculated; Step 2: Based on power synchronization control, according to the active power reference value P... ref The deviation from the actual output active power P is used to calculate the power synchronization angular frequency compensation amount Δω. PSC Step 3: Based on voltage synchronization control, a high-pass filter with a preset cutoff frequency is connected in series in the voltage synchronization loop, and the voltage synchronization angular frequency compensation amount Δω is generated through the voltage synchronization loop after connecting the high-pass filter in series. VBS Step 4, adjust the power synchronization angular frequency compensation amount Δω PSC The voltage synchronization angular frequency compensation amount Δω VBS The total angular frequency ω is obtained by superimposing the rated angular frequency ω0 of the power grid. HSC For the total angular frequency ω HSC By performing integration, the hybrid output phase θ of the converter is obtained. HSC Step 5, by mixing the output phase θ HSC For the common point of connection voltage v of the hybrid synchronous converter PCCa ,v PCCb ,v PCCc and three-phase grid current i ga i gb i gc Perform a dq coordinate transformation to obtain the dq component v of the voltage at the point of common coupling. PCCd ,v PCCq and the three-phase grid-connected current dq component i gd i gq Step 6, based on the reactive power reference value Q ref Reactive power Q and rated voltage reference value V ref Generate an internal potential amplitude command E; then use the internal potential amplitude command E and the common coupling point voltage dq component v PCCd ,v PCCq The dq axis current reference command i is calculated. d,ref i q,ref Step 7, set the dq axis current reference command i d,ref i q,ref Three-phase grid-connected current dq component i gd i gq and the voltage dq component at the point of common coupling v PCCd ,v PCCq After being controlled by the inner current loop, the modulated wave dq component v is obtained. md ,v mq Then, using the mixed output phase θ HSC Inverse transformation yields the three-phase modulated wave v ma ,v mb ,v mc And by using pulse width modulation, a corresponding switching signal is generated to drive the operation of the hybrid synchronous converter.

2. The optimized control method for improving the power point tracking accuracy of a hybrid synchronous converter according to claim 1, characterized in that, The expressions for the actual output active power P and reactive power Q mentioned in step 1 are: 。 3. The optimized control method for improving the power point tracking accuracy of a hybrid synchronous converter according to claim 1, characterized in that, The power synchronization control described in step 2 adopts a second-order virtual synchronous machine model, and the expression of its rotor motion equation is as follows: In the formula, J is the virtual moment of inertia, and D... p P is the virtual damping coefficient. ref Here, s is the active power reference value, and s is the Laplace operator; the power synchronization angular frequency compensation Δω is obtained through this rotor motion equation. PSC .

4. The optimized control method for improving the power point tracking accuracy of a hybrid synchronous converter according to claim 1, characterized in that, The implementation process of step 3 is as follows: Step 3.1, the voltage synchronization loop is set to proportional control only, and the proportional coefficient is K. p,PLL Step 3.2: Connect a high-pass filter in series in the voltage synchronization loop that only uses proportional control. HPF (s) is the transfer function of the high-pass filter, and its expression is: In the formula, s is the Laplace operator, ω c The cutoff angular frequency of the high-pass filter; Step 3.3, obtain the voltage synchronization angular frequency compensation amount Δω generated by the voltage synchronization loop after the series high-pass filter. VBS Its expression is: In the formula, v PCCq’ This is the q-axis component of the common connection point voltage from the previous control cycle.

5. The optimized control method for improving the power point tracking accuracy of a hybrid synchronous converter according to claim 1, characterized in that, The total angular frequency ω mentioned in step 4 HSC The mixed output phase θ of the converter HSC The calculation formulas are as follows: Where s is the Laplace operator.

6. The optimized control method for improving the power point tracking accuracy of a hybrid synchronous converter according to claim 1, characterized in that, The implementation process of step 6 is as follows: Step 6.1, set the reactive power reference value Q... ref The result of subtracting the reactive power Q is multiplied by the reactive power droop factor n, and then fed forward with a rated voltage reference amplitude V. ref The internal potential amplitude command E is generated, and its expression is: Step 6.2, using a virtual resistor R v With virtual inductance L v The virtual admittance control loop generates the inner loop current reference command for the dq-axis current. d,ref i q,ref The control law of the virtual admittance control loop is: Where s is the Laplace operator.

7. The optimized control method for improving the power point tracking accuracy of a hybrid synchronous converter according to claim 1, characterized in that, Step 7 describes the modulation wave dq component v md ,v mq The formula for calculation is: Where s is the Laplace operator, K pc K is the proportional coefficient of the inner current loop in PI control. ic L1 is the integral coefficient of the inner current loop using PI control, and L1 is the inductance value of the inverter-side inductor in the three-phase LCL filter; the three-phase modulation wave v ma ,v mb ,v mc The transformation formula is: 。

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