A network-configuration type inverter control method based on q-axis voltage error compensation

Abstract

The application discloses a network type inverter control method based on q-axis voltage error compensation, and the method comprises the following steps: inputting q-axis voltage deviation into a q-axis voltage outer loop PI controller to output an inner loop q-axis current reference value; inputting d-axis voltage deviation into a d-axis voltage outer loop PI controller to obtain a d-axis current reference instruction; acquiring a voltage error compensation coefficient of the q-axis voltage outer loop PI controller, calculating a compensation component according to the voltage error compensation coefficient and a q-axis voltage actual component, superimposing the compensation component into the d-axis current reference instruction in a negative feedback superposition mode to generate a corrected inner loop d-axis current reference value, and generating a pulse width modulation driving signal through inner loop current closed loop tracking; through the compensation mechanism of the control dimension, the application realizes the global stability of the system under strong and weak power grids without increasing the equivalent series impedance of the main circuit.

Description

Technical Field

[0001] This invention belongs to the field of grid-connected control technology, specifically relating to a grid-connected inverter control method based on q-axis voltage error compensation. Background Technology

[0002] Grid-type inverters simulate the operation mechanism of traditional synchronous generators and exhibit controlled voltage source characteristics. They can autonomously establish system voltage and frequency without relying on grid phase information, providing necessary inertia and damping support for weak grids.

[0003] Although grid-connected inverters exhibit excellent stability in weak grid environments, when connected to a strong grid with a high short-circuit ratio, significant voltage source electrical conflicts arise due to the low impedance voltage source characteristics of both. At this time, an amplitude or phase difference exists between the internal control potential and the external grid voltage, inducing interactive currents on the low line impedance. This causes coupling and instability in the inverter's internal power synchronization control loop and voltage regulation loop, typically manifesting as low-frequency continuous oscillations of active and reactive power.

[0004] In existing technologies, a control strategy that introduces virtual impedance is typically used to mitigate the instability problem under strong power grids. However, the short-circuit ratio of a real power system is dynamically changing. When the system operating conditions shift to weak power grids, the virtual impedance at the control level will superimpose with the physical grid impedance, further reducing the actual short-circuit ratio of the system, reducing the system's phase stability margin, and easily inducing high-frequency resonance or system disconnection from the grid. Therefore, traditional control methods struggle to ensure the global stability of the inverter under both strong and weak power grids. Summary of the Invention

[0005] This invention provides a grid-connected inverter control method based on q-axis voltage error compensation to solve the problems that existing grid-connected inverters are prone to low-frequency oscillations in strong grid scenarios due to voltage source characteristic conflicts, while traditional virtual impedance control in weak grid scenarios will worsen the equivalent grid impedance and reduce the system stability margin.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] The first aspect of this invention provides a grid-type inverter control method based on q-axis voltage error compensation, comprising:

[0008] The acquired three-phase AC voltage and three-phase AC current signals are converted into actual components of d-axis voltage, q-axis voltage, d-axis current, and q-axis current.

[0009] The deviation between the actual q-axis voltage component and the q-axis voltage reference value is input to the outer loop PI controller (full Chinese name: AC voltage proportional-integral controller) of the q-axis voltage, which outputs the inner loop q-axis current reference value.

[0010] The deviation between the actual d-axis voltage component and the d-axis voltage reference value is input to the outer loop PI controller of the d-axis voltage to obtain the d-axis current reference command; the voltage error compensation coefficient of the outer loop PI controller of the q-axis voltage is obtained, and the compensation component is calculated based on the voltage error compensation coefficient and the actual q-axis voltage component. The compensation component is fed into the d-axis current reference command in a negative feedback superposition manner to generate the corrected inner loop d-axis current reference value.

[0011] The deviations between the actual d-axis current component and the inner loop d-axis current reference value, and the deviations between the actual q-axis current component and the inner loop q-axis current reference value are input to the inner loop PI controller to obtain the basic components of the inverter modulation voltage under the dq axes. The actual d-axis current component and the actual q-axis current component are input to the cross-decoupling module to obtain the dq-axis cross-decoupling compensation term. The basic components of the inverter modulation voltage under the dq axes are superimposed with the dq-axis cross-decoupling compensation term to obtain the final modulation voltages of the d and q axes. The final modulation voltages of the d and q axes are converted into three-phase voltage reference values.

[0012] The three-phase voltage reference value is input to the pulse width modulation module to generate the power switching device drive signal, and the grid-type inverter main circuit is controlled to operate according to the power switching device drive signal.

[0013] Furthermore, the three-phase AC voltage signal and three-phase AC current signal are converted into actual components of d-axis voltage, q-axis voltage, d-axis current, and q-axis current, specifically including:

[0014] The actual active power P output by the inverter is calculated based on the collected three-phase AC voltage and three-phase AC current signals.

[0015] The active power deviation value is obtained by subtracting the actual active power P from the active power reference command; the active power deviation value is input into the virtual synchronous control calculation model, and the internal reference angular frequency of the inverter is generated by simulating the rotor inertia and damping characteristics of the synchronous generator; the internal virtual phase angle is generated by performing time integration on the internal reference angular frequency. ;

[0016] Using internal virtual phase angle Generate Parker coordinate transformation matrix to convert the three-phase AC voltage signal and the three-phase AC current signal into actual components of d-axis voltage, q-axis voltage, d-axis current, and q-axis current.

[0017] Furthermore, the voltage error compensation coefficient of the outer loop PI controller for the q-axis voltage is obtained, specifically including:

[0018] A small-signal disturbance is applied to the steady-state operating point of the grid-type inverter to establish a power incremental matrix equation;

[0019] Virtual Inertia Based on Grid-Type Inverter and damping coefficient Establish active power disturbance to internal virtual phase angle perturbation The transfer function matrix;

[0020] Based on the Jacobian coefficient matrix and transfer function matrix of the power incremental matrix equation, a real perturbation analytical mapping model from the physical coordinate system to the controller coordinate system is constructed.

[0021] The inverter admittance matrix is ​​derived from the real perturbation analytical mapping model. ;

[0022] Based on inverter admittance matrix The voltage error compensation coefficient is determined by the zero-point criterion of the determinant of the frequency domain loop impedance matrix; the voltage error compensation coefficient includes the proportional gain coefficient and integral gain coefficient of the q-axis voltage outer loop PI controller.

[0023] Furthermore, based on the voltage error compensation coefficient and the actual q-axis voltage component, the compensation component is calculated and then fed into the d-axis current reference command using a negative feedback superposition method to generate a corrected inner-loop d-axis current reference value. Specifically, this includes:

[0024] ;

[0025] in, This is the reference value for the inner loop d-axis current. This is a d-axis current reference command. The proportional gain coefficient of the outer loop PI controller for the q-axis voltage. Here, is the integral gain coefficient of the q-axis voltage outer-loop PI controller, and s is the Laplace operator. This represents the actual component of the q-axis voltage.

[0026] Furthermore, a small-signal perturbation is applied to the steady-state operating point of the grid-connected inverter to establish a power incremental matrix equation, specifically including:

[0027] ;

[0028] , ;

[0029] In the formula, For small-signal disturbances with active power, For reactive power small signal disturbance, This is the Jacobian coefficient matrix for voltage and power. Let d be the steady-state value of the grid voltage in the controller coordinate system. Let q be the steady-state value of the grid voltage in the controller coordinate system. This is the Jacobian coefficient matrix for current and power. Let d be the steady-state value of the grid current in the controller coordinate system. Let q be the steady-state value of the grid current in the controller coordinate system. and These represent the steady-state values ​​of the grid current along the d-axis and q-axis in the physical coordinate system, respectively. and These are the steady-state values ​​of the grid current along the d-axis and q-axis in the physical coordinate system, respectively.

[0030] Furthermore, virtual inertia based on grid-connected inverters and damping coefficient Establish active power disturbance to internal virtual phase angle perturbation The transfer function matrix; specifically including:

[0031] ;

[0032] ;

[0033] In the formula, For the transfer function matrix, The fundamental angular frequency of the power grid. For the Laplace operator; For small-signal disturbances with active power, This is a small-signal disturbance of reactive power.

[0034] Furthermore, based on the Jacobian coefficient matrix and transfer function matrix of the power incremental matrix equation, a real-disturbance analytical mapping model from the physical coordinate system to the controller coordinate system is constructed; specifically including:

[0035] Based on the derivation of the transfer function matrix, the equivalent voltage transfer matrix and equivalent current transfer matrix caused by the phase angle disturbance are obtained, and their expressions are as follows:

[0036] , ;

[0037] In the formula, and These represent the steady-state values ​​of the grid current along the d-axis and q-axis in the physical coordinate system, respectively. and These are the steady-state values ​​of the grid current along the d-axis and q-axis in the physical coordinate system, respectively. The transfer function matrix; This is the equivalent voltage transfer matrix. This is the equivalent current transfer matrix;

[0038] An auxiliary decoupling matrix is ​​constructed from the equivalent current transfer matrix and the Jacobian coefficient matrices of current and power, expressed as follows:

[0039] ;

[0040] In the formula, This is the Jacobian coefficient matrix for current and power. For auxiliary decoupling matrix;

[0041] Based on the auxiliary decoupling matrix, equivalent voltage transfer matrix, equivalent current transfer matrix, and Jacobian coefficient matrix, a real disturbance analytical mapping model from the physical coordinate system to the controller coordinate system is constructed, expressed by the following formula:

[0042] ;

[0043] ;

[0044] ;

[0045] ;

[0046] ;

[0047] ;

[0048] In the formula, This is the Jacobian coefficient matrix for voltage and power. This represents the small-signal disturbance vector of the grid voltage in the dq coordinate system inside the controller. This represents the small-signal disturbance vector of the grid current in the dq coordinate system inside the controller. Let be the small-signal disturbance vector of the grid current in the system's physical dq coordinate system. Let be the small-signal disturbance vector of the grid voltage in the system's physical dq coordinate system. This is the transfer matrix from the physical coordinate system voltage to the controller coordinate system voltage. This is the transfer matrix from current in the physical coordinate system to voltage in the controller coordinate system. This is the transfer matrix from voltage in the physical coordinate system to current in the controller coordinate system. This is the transfer matrix from the physical coordinate system current to the controller coordinate system current. It is an identity matrix.

[0049] Furthermore, the inverter admittance matrix is ​​derived from the real-disturbance analytical mapping model. Specifically, it includes:

[0050] The voltage outer loop regulation matrix is ​​constructed based on the proportional gain coefficient and integral gain coefficient of the q-axis voltage outer loop PI controller, expressed by the following formula:

[0051] ;

[0052] In the formula, The proportional gain coefficient of the outer loop PI controller for the q-axis voltage. Here, is the integral gain coefficient of the q-axis voltage outer-loop PI controller, and s is the Laplace operator. This is the voltage outer loop adjustment matrix;

[0053] Based on the real-disturbance analytical mapping model, combining the inner-loop PI controller matrix and the outer-loop voltage regulation matrix, and considering the equivalent gain matrix of space vector pulse width modulation, the inverter control closed-loop equation is established, expressed as follows:

[0054] ;

[0055] ;

[0056] ;

[0057] In the formula, The actual output PWM modulated voltage is subject to small signal disturbance. For voltage feedback synthesis matrix, For current feedback synthesis matrix, Let be the small-signal disturbance vector of the grid current in the system's physical dq coordinate system. This is the small-signal disturbance vector of the grid voltage in the system's physical dq coordinate system; This is the inverse coordinate transformation matrix from the controller coordinate system to the physical coordinate system. This is the equivalent gain matrix for space vector pulse width modulation. This is the cross-axis feedforward decoupling matrix for the filter inductor. For the inner loop PI controller matrix, This is the transfer matrix from the physical coordinate system voltage to the controller coordinate system voltage. This is the transfer matrix from current in the physical coordinate system to voltage in the controller coordinate system;

[0058] For the LC filter network of the inverter main circuit, establish the inverter-side inductor admittance matrix. and the parallel branch admittance matrix composed of filter capacitors and series damping resistors. ;

[0059] Based on inverter-side inductor admittance matrix and parallel branch admittance matrix Construct the physical Kirchhoff current equations for the inverter's main circuit, simultaneously solve the control closed-loop equations and the physical Kirchhoff current equations for the main circuit, and derive the inverter admittance matrix by eliminating internal disturbance variables. Formula: .

[0060] Furthermore, based on the inverter admittance matrix The voltage error compensation coefficient is determined by the zero-point criterion of the determinant of the frequency domain loop impedance matrix, specifically including:

[0061] Construct an external AC power grid in the dq rotating coordinate system, including the equivalent resistance of the lines. and equivalent inductance and the small-signal impedance matrix of the power grid for the fundamental frequency coupling term. ;

[0062] The small-signal impedance matrix of the power grid With inverter admittance matrix By combining the equations, we can construct the characteristic equation of the loop impedance matrix of the grid-connected loop, expressed as follows:

[0063] ;

[0064] In the formula, It is a matrix determinant function. It is the identity matrix;

[0065] Solve for the eigenvalues ​​and poles of the characteristic equation of the loop impedance matrix; iteratively adjust the proportional gain coefficient of the q-axis voltage error compensation. and integral gain coefficient The output voltage error compensation coefficient is calculated until the real parts of all characteristic root poles are less than the tolerance threshold.

[0066] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0067] This invention employs a control strategy based on q-axis voltage error compensation. By superimposing compensation signals in parallel within the control inner loop, it reshapes the equivalent admittance, avoiding the addition of extra equivalent series impedance in the main circuit. Therefore, this invention not only possesses strong oscillation suppression capabilities under strong grid conditions but also, under weak grid conditions, avoids exacerbating voltage dips or worsening the actual short-circuit ratio of the system, significantly improving the dynamic performance of grid-connected inverters in weak grid environments. Attached Figure Description

[0068] Figure 1 This is a structural diagram of the grid-connected system provided in Embodiment 1 of the present invention;

[0069] Figure 2 This is a structural diagram of the virtual synchronization control operation model provided in Embodiment 1 of the present invention;

[0070] Figure 3 This is a structural diagram of the dq / abc coordinate transformation module provided in Embodiment 1 of the present invention;

[0071] Figure 4 This is the characteristic root distribution diagram of a traditional grid system without additional virtual impedance under a strong power grid SCR=15.3;

[0072] Figure 5 This is a waveform diagram of the output active power of a traditional grid system without additional virtual impedance under a strong power grid SCR=15.3.

[0073] Figure 6 This is a waveform diagram of the reactive power output of a traditional grid system without additional virtual impedance under a strong power grid SCR=15.3.

[0074] Figure 7 This is the system eigenvalue distribution diagram of the present invention under a strong power grid SCR=15.3;

[0075] Figure 8 This is the system eigenvalue distribution diagram of the present invention under a weak power grid SCR=1.53;

[0076] Figure 9 This is a waveform diagram of the output active power of the present invention under both strong and weak power grids;

[0077] Figure 10 This is a waveform diagram of the reactive power output of the present invention under both strong and weak power grids;

[0078] Figure 11 This is a comparison of the output active power waveforms of two control systems under a strong power grid with SCR=15.3.

[0079] Figure 12 This is a comparison of the output reactive power waveforms of two control systems under a strong power grid with SCR=15.3.

[0080] Figure 13 This is a comparison of the output active power waveforms of two control systems under a weak power grid with an SCR of 1.53.

[0081] Figure 14 This is a comparison of the output reactive power waveforms of two control systems under a weak power grid with SCR=1.53. Detailed Implementation

[0082] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0083] This implementation provides a grid-type inverter control method based on q-axis voltage error compensation, including:

[0084] Figure 1 The diagram shows the complete structure of the main circuit and closed-loop control system of a grid-type inverter with LC filtering. The DC power supply provides input to the three-phase voltage-source inverter bridge, which converts the DC power into a high-frequency PWM AC voltage via a pulse-width modulation (PWM) module drive signal. A second-order LC low-pass filter, including a filter inductor, is configured on the inverter side. L f Filter capacitor With series damping resistor Its function is to filter out switching frequency ripple, suppress LC resonance spikes, and output high-quality power frequency AC voltage;

[0085] The filtered AC voltage is connected to the power grid at the point of common coupling (PCC), and the power grid is represented by an ideal AC voltage source superimposed with the equivalent grid impedance. Formal modeling; where, For the inverter to output grid-connected current to the grid, This is the voltage at point PCC.

[0086] To establish the power increment matrix equation by applying a small-signal perturbation at the steady-state operating point of the grid-connected inverter, the following steps are taken:

[0087] ;

[0088] , ;

[0089] In the formula, For small-signal disturbances with active power, For small-signal reactive power disturbances, This is the Jacobian coefficient matrix for voltage and power. Let d be the steady-state value of the grid voltage in the controller coordinate system. Let q be the steady-state value of the grid voltage in the controller coordinate system. This is the Jacobian coefficient matrix for current and power. Let d be the steady-state value of the grid current in the controller coordinate system. Let q be the steady-state value of the grid current in the controller coordinate system. and These represent the steady-state values ​​of the grid current along the d-axis and q-axis in the physical coordinate system, respectively. and These are the steady-state values ​​of the grid current along the d-axis and q-axis in the physical coordinate system, respectively.

[0090] Virtual Inertia Based on Grid-Type Inverter and damping coefficient Establish active power disturbance to internal virtual phase angle perturbation The transfer function matrix; specifically including:

[0091] ;

[0092] ;

[0093] In the formula, For the transfer function matrix, The fundamental angular frequency of the power grid. For the Laplace operator; For small-signal disturbances with active power, This is a small-signal disturbance of reactive power.

[0094] Based on the Jacobian coefficient matrix and transfer function matrix of the power increment matrix equation, a real perturbation analytical mapping model from the physical coordinate system to the controller coordinate system is constructed; specifically including:

[0095] Based on the derivation of the transfer function matrix, the equivalent voltage transfer matrix and equivalent current transfer matrix caused by the phase angle disturbance are obtained, and their expressions are as follows:

[0096] , ;

[0097] In the formula, and These represent the steady-state values ​​of the grid current along the d-axis and q-axis in the physical coordinate system, respectively. and These are the steady-state values ​​of the grid current along the d-axis and q-axis in the physical coordinate system, respectively. The transfer function matrix; This is the equivalent voltage transfer matrix. This is the equivalent current transfer matrix;

[0098] An auxiliary decoupling matrix is ​​constructed from the equivalent current transfer matrix and the Jacobian coefficient matrices of current and power, expressed as follows:

[0099] ;

[0100] In the formula, This is the Jacobian coefficient matrix for current and power. For auxiliary decoupling matrix;

[0101] Based on the auxiliary decoupling matrix, equivalent voltage transfer matrix, equivalent current transfer matrix, and Jacobian coefficient matrix, a real disturbance analytical mapping model from the physical coordinate system to the controller coordinate system is constructed, expressed by the following formula:

[0102] ;

[0103] ;

[0104] ;

[0105] ;

[0106] ;

[0107] ;

[0108] In the formula, This is the Jacobian coefficient matrix for voltage and power. This represents the small-signal disturbance vector of the grid voltage in the dq coordinate system inside the controller. This represents the small-signal disturbance vector of the grid current in the dq coordinate system inside the controller. Let be the small-signal disturbance vector of the grid current in the system's physical dq coordinate system. Let be the small-signal disturbance vector of the grid voltage in the system's physical dq coordinate system. This is the transfer matrix from the physical coordinate system voltage to the controller coordinate system voltage. This is the transfer matrix from current in the physical coordinate system to voltage in the controller coordinate system. This is the transfer matrix from voltage in the physical coordinate system to current in the controller coordinate system. This is the transfer matrix from the physical coordinate system current to the controller coordinate system current. It is an identity matrix.

[0109] The inverter admittance matrix is ​​derived from the real perturbation analytical mapping model. Specifically, it includes:

[0110] The voltage outer loop regulation matrix is ​​constructed based on the proportional gain coefficient and integral gain coefficient of the q-axis voltage outer loop PI controller, expressed by the following formula:

[0111] ;

[0112] In the formula, The proportional gain coefficient of the outer loop PI controller for the q-axis voltage. Here, is the integral gain coefficient of the q-axis voltage outer-loop PI controller, and s is the Laplace operator. This is the voltage outer loop adjustment matrix;

[0113] Based on the real-disturbance analytical mapping model, combining the inner-loop PI controller matrix and the outer-loop voltage regulation matrix, and considering the equivalent gain matrix of space vector pulse width modulation, the inverter control closed-loop equation is established, expressed as follows:

[0114] ;

[0115] ;

[0116] ;

[0117] In the formula, The actual output PWM modulated voltage is subject to small signal disturbance. For voltage feedback synthesis matrix, For current feedback synthesis matrix, Let be the small-signal disturbance vector of the grid current in the system's physical dq coordinate system. This is the small-signal disturbance vector of the grid voltage in the system's physical dq coordinate system; This is the inverse coordinate transformation matrix from the controller coordinate system to the physical coordinate system. This is the equivalent gain matrix for space vector pulse width modulation. This is the cross-axis feedforward decoupling matrix for the filter inductor. For the inner loop PI controller matrix, This is the transfer matrix from the physical coordinate system voltage to the controller coordinate system voltage. This is the transfer matrix from current in the physical coordinate system to voltage in the controller coordinate system;

[0118] For the LC filter network of the inverter main circuit, establish the inverter-side inductor admittance matrix. and the parallel branch admittance matrix composed of filter capacitors and series damping resistors. ;

[0119] Based on inverter-side inductor admittance matrix and parallel branch admittance matrix Construct the physical Kirchhoff current equations for the inverter's main circuit, simultaneously solve the control closed-loop equations and the physical Kirchhoff current equations for the main circuit, and derive the inverter admittance matrix by eliminating internal disturbance variables. Formula: .

[0120] Based on inverter admittance matrix The voltage error compensation coefficient is determined by the zero-point criterion of the determinant of the frequency domain loop impedance matrix, specifically including:

[0121] Construct an external AC power grid in the dq rotating coordinate system, including the equivalent resistance of the lines. and equivalent inductance and the small-signal impedance matrix of the power grid for the fundamental frequency coupling term. ;

[0122] The small-signal impedance matrix of the power grid With inverter admittance matrix By combining the equations, we can construct the characteristic equation of the loop impedance matrix of the grid-connected loop, expressed as follows:

[0123] ;

[0124] In the formula, It is a matrix determinant function. It is the identity matrix;

[0125] Solve for the eigenvalues ​​and poles of the characteristic equation of the loop impedance matrix; iteratively adjust the proportional gain coefficient of the q-axis voltage error compensation. and integral gain coefficient The output voltage error compensation coefficient is calculated until the real parts of all characteristic root poles are less than the tolerance threshold. The voltage error compensation coefficient includes the proportional gain coefficient and integral gain coefficient of the q-axis voltage outer loop PI controller.

[0126] like Figure 3 As shown, the three-phase AC voltage signal and the three-phase AC current signal are converted into the actual d-axis voltage component. q-axis voltage actual component d-axis current actual components and the actual component of the q-axis current Specifically, it includes:

[0127] The actual active power P output by the inverter is calculated based on the collected three-phase AC voltage and three-phase AC current signals.

[0128] like Figure 2 As shown, the active power deviation value is obtained by subtracting the actual active power P from the active power reference command; the active power deviation value is input into the virtual synchronous control calculation model, and the internal reference angular frequency of the inverter is generated by simulating the rotor inertia and damping characteristics of the synchronous generator; where 1 / w represents the conversion of power deviation into torque deviation, and 1 / s is the integral term. For virtual inertia, The damping coefficient is... This is the reference value for the rated angular velocity;

[0129] The internal virtual phase angle is generated by performing time integration on the internal reference angular frequency. ; Utilizing internal virtual phase angle Generate a Parker coordinate transformation matrix to convert the three-phase AC voltage and current signals into the actual d-axis voltage components. q-axis voltage actual component d-axis current actual components and the actual component of the q-axis current .

[0130] The deviation between the actual q-axis voltage component and the q-axis voltage reference value is input to the outer loop PI controller (full Chinese name: AC voltage proportional-integral controller) of the q-axis voltage, which outputs the inner loop q-axis current reference value.

[0131] The deviation between the actual d-axis voltage component and the d-axis voltage reference value is input to the outer loop PI controller of the d-axis voltage to obtain the d-axis current reference command; the voltage error compensation coefficient of the outer loop PI controller of the q-axis voltage is obtained, and the compensation component is calculated based on the voltage error compensation coefficient and the actual q-axis voltage component. The compensation component is then fed into the d-axis current reference command in a negative feedback superposition manner to generate the corrected inner loop d-axis current reference value, specifically including:

[0132] ;

[0133] in, This is the reference value for the inner loop d-axis current. This is a d-axis current reference command. The proportional gain coefficient of the outer loop PI controller for the q-axis voltage. Here, is the integral gain coefficient of the q-axis voltage outer-loop PI controller, and s is the Laplace operator. This represents the actual component of the q-axis voltage.

[0134] The deviations of the actual d-axis current component from the inner-loop d-axis current reference value, and the deviations of the actual q-axis current component from the inner-loop q-axis current reference value are input to the inner-loop PI controller to obtain the basic components of the inverter modulation voltage under the d and q axes. The actual d-axis current components and the actual q-axis current are input to the cross-decoupling module to obtain the d and q-axis cross-decoupling compensation term. The basic components of the inverter modulation voltage under the d and q axes are superimposed with the d and q-axis cross-decoupling compensation term to obtain the final modulation voltage of the d and q axes. The internal virtual phase angle is then used. Generate the Parker coordinate transformation matrix to convert the final modulation voltages on the d-axis and q-axis into three-phase voltage reference values;

[0135] The three-phase voltage reference value is input to the pulse width modulation module to generate the power switching device drive signal, and the grid-type inverter main circuit is controlled to operate according to the power switching device drive signal.

[0136] By introducing an integral gain coefficient into the q-axis voltage error compensation The integral term ensures that when the system experiences active power disturbances, primary frequency regulation, or large-scale grid intensity switching and enters a steady-state operation phase, the closed-loop system must satisfy... This eliminates the steady-state static error of reactive power and achieves physical decoupling between the active and reactive power output of the inverter in steady state.

[0137] The q-axis voltage error compensation signal in the control method is a parallel compensation mechanism. By superimposing the compensation signal in parallel in the inner control loop to reshape the closed-loop equivalent admittance of the inverter port input, no equivalent series virtual impedance parameter is added to the inverter main circuit control equation. This avoids the defect that the actual short-circuit ratio of the system will be further deteriorated due to the superposition of physical impedance and series virtual impedance in a weak grid environment. While ensuring the ability to suppress low-frequency oscillations in a strong grid, the maximum power transmission capacity and synchronization torque of the inverter under a weak grid are maintained.

[0138] To verify the effectiveness of the control method proposed in this invention, a grid-connected inverter system model was built in simulation software. The method of this invention was compared and verified with the traditional control method under different grid short-circuit ratio conditions. The main parameters of the grid-connected inverter system model are shown in Table 1.

[0139] Table 1. List of main parameters for grid-connected inverter system model;

[0140]

[0141] like Figures 4 to 6 As shown, after adopting the traditional grid-type control method without additional damping, the characteristic roots of the system loop impedance determinant show conjugate poles in the right half of the complex plane, indicating that the system has a low-frequency divergent oscillation mode. Combined with the time-domain waveform, it can be seen that under traditional control, after grid-connected startup, the system's output active and reactive power exhibit significant low-frequency oscillations that fail to converge.

[0142] like Figure 7 and Figure 8 As shown, after switching to the control method proposed in this invention, the unstable poles originally located in the right half-plane are effectively pulled to the stable region of the left half-plane, and all characteristic roots of the system exhibit stable modes.

[0143] When the power grid short-circuit ratio is selected as a strong power grid condition, the short-circuit ratio SCR = 15.3; when the power grid short-circuit ratio is selected as a weak power grid condition, the short-circuit ratio SCR = 1.53; if Figure 9 and Figure 10 The inverter's active and reactive power can quickly calm fluctuations and converge to steady-state command values, low-frequency oscillations are eliminated, and the reactive power error is zero in steady state.

[0144] like Figures 11 to 14As shown, the two control methods are the traditional virtual impedance control method and the control method proposed in this invention. Traditional virtual impedance control, by adding an additional impedance in series with the equivalent main circuit, further significantly reduces the already extremely low system short-circuit ratio. When the system operates under this condition or encounters power command changes, the system using virtual impedance control cannot maintain stability due to severely insufficient synchronization torque, resulting in significant oscillations and divergence in the power waveform. However, the method proposed in this invention, based on q-axis voltage error compensation, is a parallel feedforward mechanism at the control information level and does not increase the equivalent series impedance of the main circuit, thus not weakening the system synchronization torque under weak grid conditions. Under the same weak grid and command conditions, the system controlled by this invention not only did not become unstable but also smoothly tracked the reference command, maintaining a very high stability margin. This proves that the method of this invention effectively suppresses strong grid oscillations while overcoming the instability defects of the virtual impedance method under weak grid conditions, greatly improving the grid adaptability of grid-connected inverters.

[0145] The PI feedforward mechanism of this invention endows the system with adaptive damping adjustment characteristics over a wide frequency range: in the mid-to-high frequency range, the proportional term... Dominantly providing high-frequency positive virtual resistance damping similar to active admittance methods, it can rapidly dissipate resonant energy and effectively suppress high-frequency current and voltage oscillations caused by small line inductance under strong power grids; in the low-frequency range, the integral term... It dominates and provides extremely high low-frequency electrical stiffness. This wide-frequency-domain damping adaptive characteristic allows the system to break the deadlock of traditional fixed parameters that are difficult to balance.

[0146] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0147] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0148] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0149] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0150] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A grid-type inverter control method based on q-axis voltage error compensation, characterized in that, include: The acquired three-phase AC voltage and three-phase AC current signals are converted into actual components of d-axis voltage, q-axis voltage, d-axis current, and q-axis current. The deviation between the actual q-axis voltage component and the q-axis voltage reference value is input to the outer loop PI controller of the q-axis voltage to output the inner loop q-axis current reference value; The deviation between the actual d-axis voltage component and the d-axis voltage reference value is input to the outer loop PI controller of the d-axis voltage to obtain the d-axis current reference command; Obtain the voltage error compensation coefficient of the outer loop PI controller of the q-axis voltage, calculate the compensation component based on the voltage error compensation coefficient and the actual component of the q-axis voltage, and feed the compensation component into the d-axis current reference command in a negative feedback superposition manner to generate the corrected inner loop d-axis current reference value. The deviations between the actual d-axis current component and the inner loop d-axis current reference value, and the deviations between the actual q-axis current component and the inner loop q-axis current reference value are input to the inner loop PI controller to obtain the basic components of the inverter modulation voltage under the dq axes. The actual d-axis current component and the actual q-axis current component are input to the cross-decoupling module to obtain the dq-axis cross-decoupling compensation term. The basic components of the inverter modulation voltage under the dq axes are superimposed with the dq-axis cross-decoupling compensation term to obtain the final modulation voltages of the d and q axes. The final modulation voltages of the d and q axes are converted into three-phase voltage reference values. The three-phase voltage reference value is input to the pulse width modulation module to generate the power switching device drive signal, and the grid-type inverter main circuit is controlled to operate according to the power switching device drive signal.

2. The grid-connected inverter control method according to claim 1, characterized in that, The three-phase AC voltage signal and three-phase AC current signal are converted into actual components of d-axis voltage, q-axis voltage, d-axis current, and q-axis current, specifically including: The actual active power P output by the inverter is calculated based on the collected three-phase AC voltage and three-phase AC current signals. The active power deviation value is obtained by subtracting the actual active power P from the active power reference command; the active power deviation value is input into the virtual synchronous control calculation model, and the internal reference angular frequency of the inverter is generated by simulating the rotor inertia and damping characteristics of the synchronous generator; the internal virtual phase angle is generated by performing time integration on the internal reference angular frequency. ; Using internal virtual phase angle Generate Parker coordinate transformation matrix to convert the three-phase AC voltage signal and the three-phase AC current signal into actual components of d-axis voltage, q-axis voltage, d-axis current, and q-axis current.

3. The grid-connected inverter control method according to claim 1, characterized in that, Obtain the voltage error compensation coefficient of the outer loop PI controller for the q-axis voltage, specifically including: A small-signal disturbance is applied to the steady-state operating point of the grid-type inverter to establish a power incremental matrix equation; Virtual Inertia Based on Grid-Type Inverter and damping coefficient Establish active power disturbance to internal virtual phase angle perturbation The transfer function matrix; Based on the Jacobian coefficient matrix and transfer function matrix of the power incremental matrix equation, a real perturbation analytical mapping model from the physical coordinate system to the controller coordinate system is constructed. The inverter admittance matrix is ​​derived from the real perturbation analytical mapping model. ; Based on inverter admittance matrix The voltage error compensation coefficient is determined by the zero-point criterion of the determinant of the frequency domain loop impedance matrix; the voltage error compensation coefficient includes the proportional gain coefficient and integral gain coefficient of the q-axis voltage outer loop PI controller.

4. The grid-type inverter control method according to claim 3, characterized in that, The compensation component is calculated based on the voltage error compensation coefficient and the actual q-axis voltage component. This compensation component is then fed into the d-axis current reference command via negative feedback to generate a corrected inner-loop d-axis current reference value. Specifically, this includes: ； in, This is the reference value for the inner loop d-axis current. This is a d-axis current reference command. The proportional gain coefficient of the outer loop PI controller for the q-axis voltage. Here, is the integral gain coefficient of the q-axis voltage outer-loop PI controller, and s is the Laplace operator. This represents the actual component of the q-axis voltage.

5. The grid-connected inverter control method according to claim 3, characterized in that, To establish the power increment matrix equation by applying a small-signal perturbation at the steady-state operating point of the grid-connected inverter, the following steps are taken: ； ， ； In the formula, For small-signal disturbances with active power, For small-signal reactive power disturbances, This is the Jacobian coefficient matrix for voltage and power. Let d be the steady-state value of the grid voltage in the controller coordinate system. Let q be the steady-state value of the grid voltage in the controller coordinate system. This is the Jacobian coefficient matrix for current and power. Let d be the steady-state value of the grid current in the controller coordinate system. Let q be the steady-state value of the grid current in the controller coordinate system. and These represent the steady-state values ​​of the grid current along the d-axis and q-axis in the physical coordinate system, respectively. and These are the steady-state values ​​of the grid current along the d-axis and q-axis in the physical coordinate system, respectively.

6. The grid-connected inverter control method according to claim 5, characterized in that, Virtual Inertia Based on Grid-Type Inverter and damping coefficient Establish active power disturbance to internal virtual phase angle perturbation The transfer function matrix; specifically including: ； ； In the formula, For the transfer function matrix, The fundamental angular frequency of the power grid. For the Laplace operator; For small-signal disturbances with active power, This is a small-signal disturbance of reactive power.

7. The grid-connected inverter control method according to claim 6, characterized in that, Based on the Jacobian coefficient matrix and transfer function matrix of the power increment matrix equation, a real perturbation analytical mapping model from the physical coordinate system to the controller coordinate system is constructed; specifically including: Based on the derivation of the transfer function matrix, the equivalent voltage transfer matrix and equivalent current transfer matrix caused by the phase angle disturbance are obtained, and their expressions are as follows: ， ； In the formula, and These represent the steady-state values ​​of the grid current along the d-axis and q-axis in the physical coordinate system, respectively. and These are the steady-state values ​​of the grid current along the d-axis and q-axis in the physical coordinate system, respectively. The transfer function matrix; This is the equivalent voltage transfer matrix. This is the equivalent current transfer matrix; An auxiliary decoupling matrix is ​​constructed from the equivalent current transfer matrix and the Jacobian coefficient matrices of current and power, expressed as follows: ； In the formula, This is the Jacobian coefficient matrix for current and power. For auxiliary decoupling matrix; It is the identity matrix; Based on the auxiliary decoupling matrix, equivalent voltage transfer matrix, equivalent current transfer matrix, and Jacobian coefficient matrix, a real disturbance analytical mapping model from the physical coordinate system to the controller coordinate system is constructed, expressed by the following formula: ； ； ； ； ； ； In the formula, This is the Jacobian coefficient matrix for voltage and power. This represents the small-signal disturbance vector of the grid voltage in the dq coordinate system inside the controller. This represents the small-signal disturbance vector of the grid current in the dq coordinate system inside the controller. Let be the small-signal disturbance vector of the grid current in the system's physical dq coordinate system. Let be the small-signal disturbance vector of the grid voltage in the system's physical dq coordinate system. This is the transfer matrix from the physical coordinate system voltage to the controller coordinate system voltage. This is the transfer matrix from current in the physical coordinate system to voltage in the controller coordinate system. This is the transfer matrix from voltage in the physical coordinate system to current in the controller coordinate system. This is the transfer matrix from the physical coordinate system current to the controller coordinate system current.

8. The grid-connected inverter control method according to claim 7, characterized in that, The inverter admittance matrix is ​​derived from the real perturbation analytical mapping model. Specifically, it includes: The voltage outer loop regulation matrix is ​​constructed based on the proportional gain coefficient and integral gain coefficient of the q-axis voltage outer loop PI controller, expressed by the following formula: ； In the formula, The proportional gain coefficient of the outer loop PI controller for the q-axis voltage. Here, is the integral gain coefficient of the q-axis voltage outer-loop PI controller, and s is the Laplace operator. This is the voltage outer loop adjustment matrix; Based on the real-disturbance analytical mapping model, combining the inner-loop PI controller matrix and the outer-loop voltage regulation matrix, and considering the equivalent gain matrix of space vector pulse width modulation, the inverter control closed-loop equation is established, expressed as follows: ； ； ； In the formula, The actual output PWM modulated voltage is subject to small signal disturbance. For voltage feedback synthesis matrix, For current feedback synthesis matrix, Let be the small-signal disturbance vector of the grid current in the system's physical dq coordinate system. This is the small-signal disturbance vector of the grid voltage in the system's physical dq coordinate system; This is the inverse coordinate transformation matrix from the controller coordinate system to the physical coordinate system. This is the equivalent gain matrix for space vector pulse width modulation. This is the cross-axis feedforward decoupling matrix for the filter inductor. For the inner loop PI controller matrix, This is the transfer matrix from the physical coordinate system voltage to the controller coordinate system voltage. This is the transfer matrix from current in the physical coordinate system to voltage in the controller coordinate system; For the LC filter network of the inverter main circuit, establish the inverter-side inductor admittance matrix. and the parallel branch admittance matrix composed of filter capacitors and series damping resistors. ; Based on inverter-side inductor admittance matrix and parallel branch admittance matrix Construct the physical Kirchhoff current equations for the inverter's main circuit, simultaneously solve the control closed-loop equations and the physical Kirchhoff current equations for the main circuit, and derive the inverter admittance matrix by eliminating internal disturbance variables. Formula: .

9. The grid-connected inverter control method according to claim 3, characterized in that, Based on inverter admittance matrix The voltage error compensation coefficient is determined by the zero-point criterion of the determinant of the frequency domain loop impedance matrix, specifically including: Construct an external AC power grid in the dq rotating coordinate system, including the equivalent resistance of the lines. and equivalent inductance and the small-signal impedance matrix of the power grid for the fundamental frequency coupling term. ; The small-signal impedance matrix of the power grid With inverter admittance matrix By combining the equations, we can construct the characteristic equation of the loop impedance matrix of the grid-connected loop, expressed as follows: ； In the formula, It is a matrix determinant function. It is the identity matrix; Solve for the eigenvalues ​​and poles of the characteristic equation of the loop impedance matrix; iteratively adjust the proportional gain coefficient for q-axis voltage error compensation. and integral gain coefficient The output voltage error compensation coefficient is calculated until the real parts of all characteristic root poles are less than the tolerance threshold.

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