Virtual synchronous generator control method for improving power transmission capability

Abstract

The invention discloses a virtual synchronous generator control method for improving power transmission capability, which is characterized in that the traditional virtual synchronous generator control is composed of a power outer loop and an inner loop formed by voltage and current double closed loops. A reference voltage generated by a power outer loop subtracts a grid-connected point voltage and then is input into a current feed-forward compensation calculation module to generate a current feed-forward compensation value, the current feed-forward compensation value is superposed on a current given value output by a voltage controller, and the superposed value is used as a total current given value of a current controller. Compared with traditional virtual synchronous generator control, the method has the wide-range adaptive capacity of power grid impedance, and the limit power transmission capacity of active power of a grid-connected inverter can be remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of virtual synchronous generator control, and more particularly to a virtual synchronous generator control method for improving power transmission capability. Background Technology

[0002] As a high proportion of renewable energy is connected to the grid through power electronic converters, the equivalent rotating inertia and synchronous damping of the power system continue to decrease, resulting in a significant decline in system frequency stability and anti-interference capability.

[0003] Virtual synchronous generator technology simulates the rotor motion equations and voltage regulation characteristics of a synchronous generator through control algorithms, providing virtual inertia and damping support for the power grid. It has become an important means to improve the stability of new energy grid connection.

[0004] However, in actual power grids, grid impedance varies over a wide range due to differences in line length, network topology, and operating mode, which seriously affects the dynamic performance and stability of virtual synchronous generator control.

[0005] To enhance the robustness of the system to changes in grid impedance, existing technologies typically employ the method of introducing a virtual impedance. This method reshapes the system's output impedance characteristics by connecting a virtual impedance element in series in the control loop, thereby expanding the stable operating range.

[0006] However, this method has an inherent drawback: the introduced virtual impedance increases the equivalent output impedance of the control system in steady state. Based on the power transmission characteristics of the grid-connected inverter, its maximum transmitted active power (i.e., the active power limit P) max It is inversely proportional to the total impedance between the inverter output and the grid (including virtual impedance and actual grid impedance).

[0007] Therefore, while the introduction of virtual impedance improves impedance adaptability, it inevitably reduces the active power transmission limit of the system and limits the inverter's load-carrying capacity under heavy load or weak grid conditions.

[0008] Chinese patent CN121124532A discloses a converter grid control method with low-frequency impedance reshaping function. It improves the grid impedance adaptation range by designing virtual impedance, but inevitably reduces the active power transmission capacity.

[0009] Therefore, in order to solve the above-mentioned technical problems, it is an urgent technical problem for those skilled in the art to solve the problem of providing a method to effectively improve the adaptability of virtual synchronous generators to a wide range of grid impedances without sacrificing the active power transmission capacity of the system. Summary of the Invention

[0010] In view of this, the present invention provides a virtual synchronous generator control method to improve power transmission capability.

[0011] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0012] Virtual synchronous generator control methods to enhance power transmission capabilities include: the grid's rated angular frequency ω n Subtract the angular frequency ω output by the frequency-locked loop or active power loop, and multiply the difference by the active power droop coefficient k. p The given value P for primary frequency modulation is obtained. f ;

[0013] Collect the grid-connected three-phase voltage u at the grid connection point of the grid-connected inverter. pabc , grid-connected three-phase current i pabc and the three-phase current i output by the inverter Labc After dq transformation, the d-axis voltage u at the grid connection point is obtained. pd With q-axis voltage u pq d-axis current i at grid connection point pd With q-axis current i pq and the d-axis current i output by the inverter Ld With q-axis current i Lq ;

[0014] Calculate the active power P and reactive power Q output of the grid-connected inverter; active power setpoint P ref Add a frequency modulation setpoint P f Subtracting the active power P output by the grid-connected inverter yields the active power deviation. Active power deviation The reciprocal of the rated angular frequency Multiplying them together yields the virtual torque T. m ;

[0015] virtual torque T m Subtract the damping torque T D Then, multiply by the virtual inertia element Obtain angular frequency deviation Where J is the virtual inertia, s is the Laplace operator, and T is the damping torque. D Through angular frequency deviation The result is obtained by multiplying by the virtual damping coefficient D;

[0016] angular frequency deviation Plus the grid's rated angular frequency ω n Then, the angular frequency ω of the virtual synchronous generator is obtained; the phase angle θ of the virtual synchronous generator is obtained by integrating the angular frequency ω; the reactive power setpoint Q is then calculated. ref Subtracting the reactive power Q output by the grid-connected inverter yields the reactive power deviation. ; to reduce reactive power deviation Multiply by reactive power droop factor k q Receive voltage deviation ; to reduce voltage deviation Plus the rated voltage amplitude U at the grid connection point n The reference voltage amplitude E generated by the power outer loop is obtained; the reference voltage amplitude E generated by the power outer loop is combined with the phase angle θ of the virtual synchronous generator, and its d-axis expression E is obtained through coordinate transformation. d With q-axis expression E q ;

[0017] The d-axis reference voltage E generated by the power outer loop d With the d-axis voltage u at the grid connection point pd The difference is used to obtain the d-axis voltage deviation; the q-axis reference voltage E is generated by the power outer loop. q With the q-axis voltage u at the grid connection point pq The difference is calculated to obtain the q-axis voltage deviation. These d-axis and q-axis voltage deviations are then input into the voltage controller to generate the d-axis current reference value i. dref and q-axis current reference value i qref On the other hand, the input current feedforward compensation calculation module generates the d-axis current feedforward compensation value i. df With q-axis current feedforward compensation value i qf .

[0018] The current feedforward compensation calculation module adopts a dq-axis coupled virtual impedance dynamic implementation structure, which includes virtual resistance. Virtual inductance Inertial links and cross-coupling terms .in, The rated angular frequency; this module calculates the d-axis current feedforward compensation value i based on the d-axis and q-axis voltage deviations and the cross-coupling relationship between the d-axis and q-axis current feedforward compensation values. df With q-axis current feedforward compensation value i qf .

[0019] The current feedforward compensation values ​​for the d-axis and q-axis satisfy the following relationship:

[0020]

[0021] d-axis current reference value i dref With d-axis current feedforward compensation value i df The summation yields the total d-axis current setpoint i. dref_t d-axis current total setpoint i dref_t Subtract the inverter output d-axis current i Ld The resulting difference is processed by the current controller and outputs a d-axis modulation signal m. d ; q-axis current reference value iqref With q-axis current feedforward compensation value i qf The summation yields the total q-axis current setpoint i. qref_t q-axis current total setpoint i qref_t Subtract the inverter output q-axis current i Lq The difference obtained is processed by the current controller and output as a q-axis modulated signal m. q The inverter drive signal is obtained by pulse width modulation of the modulated signal.

[0022] Preferably, by introducing a current feedforward compensation calculation module, when the control system reaches steady state, the current feedforward compensation calculation module does not affect the steady-state gain from the power outer loop output reference voltage to the grid connection point voltage and the equivalent impedance of the grid connection point.

[0023] Preferably, in the voltage-current dual closed-loop system, the setpoint of the voltage controller does not introduce the grid connection point current multiplied by the virtual impedance Z. v (s) The compensation voltage generated; the d-axis current reference value i output by the voltage controller. dref and the current reference value i along the q-axis qref The following voltage difference input voltage controllers process the data to obtain the d-axis voltage reference value E. d With the d-axis voltage u at the grid connection point pd The difference, q-axis voltage reference value E q With the q-axis voltage u at the grid connection point pq The difference is expressed as follows:

[0024]

[0025] in, The transfer function of the voltage controller is the current reference value output by the voltage controller plus the current feedforward compensation value generated by the current feedforward compensation calculation module, which serves as the total reference value of the current controller.

[0026] Preferably, the current feedforward compensation calculation module is implemented using a dq-axis coupled virtual impedance dynamic structure:

[0027] Coupled virtual impedance includes virtual resistance Virtual inductance Inertial links and cross-coupling terms .in, This is the rated angular frequency. Based on the voltage deviations along the d-axis and q-axis, and considering the cross-coupling relationship between the d-axis and q-axis current feedforward compensation values, this module jointly calculates the d-axis current feedforward compensation value i. df With q-axis current feedforward compensation value i qf .

[0028] The current feedforward compensation values ​​for the d-axis and q-axis satisfy the following relationship:

[0029]

[0030] The current reference value output by the voltage controller, plus the current feedforward compensation value generated by the current feedforward compensation calculation module, is used as the total reference value of the current controller. Subtracting the inverter output current value and inputting the result back into the current controller yields the modulation voltage, whose expression is:

[0031]

[0032] in, Given the transfer function of the current controller, the expression for the grid connection point voltage at this time can be obtained as follows:

[0033]

[0034] Where H(s) is the gain from the power outer loop output reference voltage to the grid connection point voltage, Z o (s) represents the equivalent impedance between the grid connection point and the inverter;

[0035] At this point, the voltage gain H(s) and the equivalent impedance Z at the grid connection point are... o The expression for (s) is:

[0036]

[0037] Among them, E dq (s), i Ldq (s), i pdq (s) and u pdq (s) represent the d-axis and q-axis component expressions for the reference voltage generated by the power outer loop, the inverter output current, the grid connection point current, and the grid connection point voltage, respectively; K pwm L is the inverter's equivalent gain. f C f With R f These are the filter inductance, filter capacitor, and damping resistor of the filter, respectively. A virtual impedance is generated for the current feedforward compensation calculation module; whereby, , and These are the virtual resistance and virtual inductance in the virtual impedance, respectively;

[0038] Preferably, the steady-state gain of the control loop is: voltage steady-state gain: H(s=j0) = 1; inner loop output impedance Z o (s=j0) = 0; at this time, the expression for the active power output of the inverter is:

[0039]

[0040] U g L represents the amplitude of the grid voltage. g For the mains inductance, This represents the phase angle difference between the grid voltage and the reference voltage generated by the power outer loop; since the steady-state value of the equivalent impedance between the grid connection point and the inverter is 0, the denominator of the expression for the active power P output by the inverter only includes the grid impedance ω. n L g Unaffected by virtual impedance This significantly improves the transmission capacity of active power, thus mitigating the impact of [the pandemic / influence].

[0041] At this point, the inverter's active power output transmission limit P max for:

[0042]

[0043] A non-transitory computer-readable storage medium is provided for storing computer instructions, which, when executed by a processor, implement the virtual synchronous generator control method for improving power transmission capability as described above.

[0044] A computer device includes a memory and a processor, the processor and the memory communicating with each other, the memory storing program instructions executable by the processor, and the processor invoking the program instructions to execute the virtual synchronous generator control method for improving power transmission capability as described above.

[0045] An electronic device includes a processor, a memory, and a computer program; wherein the processor is connected to the memory, the computer program is stored in the memory, and when the electronic device is running, the processor executes the computer program stored in the memory to cause the electronic device to execute instructions to implement a virtual synchronous generator control method, such as improving power transmission capability.

[0046] The present invention achieves the following technical effects compared to the prior art:

[0047] This invention improves the grid impedance adaptation range by adding a current feedforward compensation calculation module, without reducing the inverter's active power output transmission limit P due to the introduction of the current feedforward compensation calculation module. max This improves the adaptability of the virtual synchronous generator to the power grid. Attached Figure Description

[0048] Figure 1 This is a block diagram of the overall control structure of the present invention;

[0049] Figure 2 This is a block diagram of the virtual synchronous generator power control of the present invention. Detailed Implementation

[0050] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0051] Example 1:

[0052] This invention discloses a virtual synchronous generator control method to improve power transmission capability, wherein, Figure 1 This is a block diagram of the overall control structure of the present invention. Figure 2 This is a block diagram of the virtual synchronous generator power control of the present invention.

[0053] The specific steps are as follows:

[0054] 1) Rated angular frequency ω of the power grid n Subtract the angular frequency ω output by the frequency-locked loop or active power loop, and multiply the difference by the active power droop coefficient k. p The given value P for primary frequency modulation is obtained. f ;

[0055] 2) Collect the grid-connected three-phase voltage u at the common connection point of the grid-connected inverter. pabc With three-phase current i pabc After dq transformation, its d-axis voltage u is obtained. pd q-axis voltage u pq d-axis current i pd q-axis current i pq ;

[0056] 3) Calculate the active power P and reactive power Q output by the grid-connected inverter;

[0057] 4) Active power setpoint P ref Add a frequency modulation setpoint P f Subtracting the active power P output by the grid-connected inverter yields the active power deviation. ;

[0058] 5) Active power deviation Reciprocal of the rated angular frequency Multiplying them together yields the virtual torque T. m ;

[0059] 6) The virtual torque T m Subtract the damping torque T D Then multiply by the virtual inertia element Obtain angular frequency deviation Where J is the virtual inertia, s is the Laplace operator, and T is the damping torque. D Through angular frequency deviation The result is obtained by multiplying by the virtual damping coefficient D;

[0060] 7) Adjust angular frequency deviation Plus the rated angular frequency ω n Then output the angular frequency ω;

[0061] 8) Reactive power setpoint Q ref Subtracting the reactive power Q output by the grid-connected inverter yields the reactive power deviation. ;

[0062] 9) Adjust reactive power deviation Multiply by reactive power droop factor k q Receive voltage deviation ;

[0063] 10) Voltage deviation Plus the rated voltage amplitude U at the grid connection point n The reference voltage amplitude E generated by the power outer loop is obtained;

[0064] 11) Combine the reference voltage E generated by the power outer loop with the phase angle θ of the virtual synchronous generator, and obtain its d-axis and q-axis expressions E through coordinate transformation. d With E q ;

[0065] 12) The d-axis reference voltage E generated by the power outer loop d Subtract the d-axis voltage u at the grid connection point pd The input voltage controller then obtains the d-axis current reference value i. dref The q-axis reference voltage E generated by the power outer loop q Subtract the q-axis voltage u at the grid connection point pq The input voltage controller then obtains the q-axis current reference value i. qref ;

[0066] 13) The d-axis reference voltage E generated by the power outer loop d With the d-axis voltage u at the grid connection point pd The difference is used to obtain the d-axis voltage deviation; the q-axis reference voltage E is generated by the power outer loop. q With the q-axis voltage u at the grid connection point pq The difference is calculated to obtain the q-axis voltage deviation. These d-axis and q-axis voltage deviations are then input into the voltage controller to generate the d-axis current reference value i. dref and q-axis current reference value i qref On the other hand, the input current feedforward compensation calculation module generates the d-axis current feedforward compensation value i. df With q-axis current feedforward compensation value i qf .

[0067] The current feedforward compensation calculation module adopts a dq-axis coupled virtual impedance dynamic implementation structure, which includes virtual resistance. Virtual inductance Inertial links and cross-coupling terms .in, This is the rated angular frequency. Based on the voltage deviations along the d-axis and q-axis, and considering the cross-coupling relationship between the d-axis and q-axis current feedforward compensation values, this module jointly calculates the d-axis current feedforward compensation value i. df With q-axis current feedforward compensation value i qf .

[0068] The current feedforward compensation values ​​for the d-axis and q-axis satisfy the following relationship:

[0069]

[0070] 14) d-axis current reference value i dref With d-axis current feedforward compensation value i df The summation yields the total d-axis current setpoint i. dref_t d-axis current total setpoint i dref_t Subtract the inverter output d-axis current i Ld The resulting difference is processed by the current controller and outputs a d-axis modulation signal m. d ; q-axis current reference value i qref With q-axis current feedforward compensation value i qf The summation yields the total q-axis current setpoint i. qref_t q-axis current total setpoint i qref_t Subtract the inverter output q-axis current i Lq The resulting difference is processed by the current controller and outputs a q-axis modulation signal m. q ;

[0071] 15) The inverter drive signal is obtained by pulse width modulation of the modulation signal.

[0072] While improving the inverter's adaptability to grid impedance through the current feedforward compensation calculation module, this method also further enhances the system's maximum active power transmission capability; the specific analysis steps for improving power transmission capability are as follows:

[0073] In traditional virtual synchronous generator control, the setpoint of the voltage controller in the voltage-current dual closed-loop system is the voltage reference value output from the power outer loop multiplied by the grid connection point current and the virtual impedance Z. v The difference in compensation voltage generated by (s);

[0074] Among them, Z v (s)=R v+jω n L v R v With L v These represent the virtual resistance and virtual inductance of the virtual impedance link, and the d-axis compensation voltage u. zvd The calculation method is as follows: virtual resistance R v With the d-axis current i at the grid connection point pd The product of, minus the virtual sense resistance ω n L v With the q-axis current i at the grid connection point pq The product of; q-axis compensation voltage u zvq The calculation formula is: Virtual resistance R v With the q-axis current i at the grid connection point pq The product of, plus virtual sensory resistance ω n L v With the d-axis current i at the grid connection point pd The product of.

[0075] At this time, the expression for the setpoint of the voltage controller is:

[0076]

[0077] The d-axis setpoint u of the voltage controller dref With the d-axis voltage u at the grid connection point pd After subtraction, the input voltage controller obtains the d-axis current reference value i. dref The q-axis setpoint u of the voltage controller qref With the q-axis voltage u at the grid connection point pq After subtraction, the input voltage controller obtains the q-axis current reference value i. qref The expressions for both are:

[0078]

[0079] Among them, G v (s) is the transfer function of the voltage controller. When the voltage controller is a proportional-integral controller, its transfer function is G. v (s)=k pv +k iv / s,k pv With k iv These are the proportional and integral coefficients of the voltage loop, respectively.

[0080] The sum of the obtained inner current loop reference value and the feedback value is used as the reference input of the current loop controller. After current loop control, the modulation voltage expression is obtained:

[0081]

[0082] Among them, G c(s) is the transfer function of the current controller, i Ld with i Lq Let G represent the d-axis and q-axis values ​​of the inverter output current. When a proportional-integral (PI) controller is used as the voltage controller, its transfer function is G. c (s)=k pc +k ic / s,k pc With k ic These are the proportional and integral coefficients of the current loop, respectively.

[0083] Based on the above control structure, the expression for the grid connection point voltage can be obtained as follows:

[0084]

[0085] Voltage gain H(s) and inner loop output impedance Z o The expression for (s) is:

[0086]

[0087] Among them, E dq (s), i Ldq (s), i pdq (s) and u pdq (s) represent the d-axis and q-axis component expressions for the reference voltage generated by the power outer loop, the inverter output current, the grid connection point current, and the grid connection point voltage, respectively; K pwm L is the inverter's equivalent gain. f C f With R f These are the filter inductor, filter capacitor, and damping resistor of the filter, respectively.

[0088] When the control system is stable, the controlled object is in DC component in synchronous coordinate system. At this time, the gain of the control loop on the DC component is: H(s=j0) = 1. That is, when the control system is stable, the virtual impedance Z added to improve the adaptability of the power grid impedance. v (s) will increase the equivalent impedance of the control loop. At this time, the expression for the active power output of the inverter is:

[0089]

[0090] Among them, U g L represents the amplitude of the grid voltage. g For the mains inductance, This is the phase angle difference between the grid voltage and the reference voltage generated by the power outer loop.

[0091] At this time, the inverter's active power output transmission limit P max for:

[0092]

[0093] From the transmission limit P max As can be seen from the expression, the increase in virtual impedance in the denominator reduces the inverter's active power output transmission limit P. max .

[0094] When using the control structure of this invention, the setpoint of the voltage controller in the voltage-current dual closed loop does not introduce the grid-connected point current multiplied by the virtual impedance Z. v (s) The compensation voltage generated; the d-axis current reference value i output by the voltage controller. dref and the current reference value i along the q-axis qref The following voltage difference input voltage controllers process the data to obtain the d-axis voltage reference value E. d With the d-axis voltage u at the grid connection point pd The difference, q-axis voltage reference value E q With the q-axis voltage u at the grid connection point pq The difference is expressed as follows:

[0095]

[0096] in, The transfer function of the voltage controller is defined as follows: the current reference value output by the voltage controller plus the current feedforward compensation value generated by the current feedforward compensation calculation module is used as the total reference value of the current controller. The calculation process of the feedforward compensation value generated by the current feedforward compensation calculation module is as follows: the d-axis reference voltage E generated by the power outer loop... d With the d-axis voltage u at the grid connection point pd The difference is used to obtain the d-axis voltage deviation; the q-axis reference voltage E is generated by the power outer loop. q With the q-axis voltage u at the grid connection point pq The difference is calculated to obtain the q-axis voltage deviation. These d-axis and q-axis voltage deviations are then input into the voltage controller to generate the d-axis current reference value i. dref and q-axis current reference value i qref On the other hand, the input current feedforward compensation calculation module generates the d-axis current feedforward compensation value i. df With q-axis current feedforward compensation value i qf .

[0097] The current feedforward compensation calculation module adopts a dq-axis coupled virtual impedance dynamic implementation structure, which includes virtual resistance. Virtual inductance Inertial links and cross-coupling terms .in, This is the rated angular frequency. Based on the voltage deviations between the d-axis and q-axis, and considering the cross-coupling relationship between the d-axis and q-axis feedforward currents, this module jointly calculates the d-axis current feedforward compensation value i. df With q-axis current feedforward compensation value i qf .

[0098] The d-axis and q-axis current feedforward compensation values ​​satisfy the following relationship:

[0099]

[0100] The current reference value output by the voltage controller, plus the current feedforward compensation value generated by the current feedforward compensation calculation module, is used as the total reference value of the current controller. Subtracting the inverter output current value and inputting the result back into the current controller yields the modulation voltage, whose expression is:

[0101]

[0102] The expression for the grid connection point voltage at this time can be obtained as follows:

[0103]

[0104] At this time, the voltage gain H(s) and the inner loop output impedance Z o The expression for (s) is:

[0105]

[0106] Among them, E dq (s), i Ldq (s), i pdq (s) and u pdq (s) represent the d-axis and q-axis component expressions for the reference voltage generated by the power outer loop, the inverter output current, the grid connection point current, and the grid connection point voltage, respectively; K pwm L is the inverter's equivalent gain. f C f With R f These are the filter inductor, filter capacitor, and damping resistor, respectively. A virtual impedance is generated for the current feedforward compensation calculation module; whereby, , and These are the virtual resistance and virtual inductance in the virtual impedance, respectively.

[0107] The steady-state gain of the control loop in this invention is: voltage steady-state gain: H(s=j0) = 1; equivalent impedance Z between the grid connection point and the inverter. o (s=j0) = 0. This means that the virtual impedance added to improve the adaptability of the grid impedance will not increase the equivalent impedance of the control loop.

[0108] At this point, the expression for the active power output by the inverter is:

[0109]

[0110] Since the steady-state value of the equivalent impedance between the grid connection point and the inverter is 0, the denominator of the expression for the active power P output by the inverter only includes the grid impedance ω. n L g Unaffected by virtual impedance This significantly improves the transmission capacity of active power, thus mitigating the impact of [the pandemic / influence].

[0111] At this time, the inverter's active power output transmission limit P max for:

[0112]

[0113] Since the added virtual impedance does not appear in the inverter's output power, this control structure, while improving the grid impedance adaptation range by adding virtual impedance, will not reduce the inverter's active power output transmission limit P due to the introduction of the current feedforward compensation calculation module. max This improves the adaptability of virtual synchronous generator control to the power grid.

[0114] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the technical scope of the present invention. Therefore, any minor modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A virtual synchronous generator control method for improving power transmission capability, characterized in that, include: Rated angular frequency ω of the power grid n Subtract the angular frequency ω output by the frequency-locked loop or active power loop, and multiply the difference by the active power droop coefficient k. p The given value P for primary frequency modulation is obtained. f ; Collect the grid-connected three-phase voltage u at the grid connection point of the grid-connected inverter. pabc , grid-connected three-phase current i pabc and the three-phase current i output by the inverter Labc After dq transformation, the d-axis voltage u at the grid connection point is obtained. pd With q-axis voltage u pq d-axis current i at grid connection point pd With q-axis current i pq and the d-axis current i output by the inverter Ld With q-axis current i Lq ; Calculate the active power P and reactive power Q output of the grid-connected inverter; active power setpoint P ref Add a frequency modulation setpoint P f Subtracting the active power P output by the grid-connected inverter yields the active power deviation. Active power deviation The reciprocal of the rated angular frequency Multiplying them together yields the virtual torque T. m ; virtual torque T m Subtract the damping torque T D Then, multiply by the virtual inertia element Obtain angular frequency deviation Where J is the virtual inertia, s is the Laplace operator, and T is the damping torque. D Through angular frequency deviation Multiply by the virtual damping coefficient D to obtain; angular frequency deviation Plus the rated angular frequency ω of the power grid n Then, the angular frequency ω of the virtual synchronous generator is obtained; the phase angle θ of the virtual synchronous generator is obtained by integrating the angular frequency ω; the reactive power setpoint Q is then calculated. ref Subtracting the reactive power Q output by the grid-connected inverter yields the reactive power deviation. ; to reduce reactive power deviation Multiply by reactive power droop factor k q Receive voltage deviation ; to reduce voltage deviation Plus the rated voltage amplitude U at the grid connection point n The reference voltage amplitude E generated by the power outer loop is obtained; the reference voltage amplitude E generated by the power outer loop is combined with the phase angle θ of the virtual synchronous generator, and its d-axis expression E is obtained through coordinate transformation. d With the q-axis expression E q The d-axis reference voltage E generated by the power outer loop d Subtract the d-axis voltage u at the grid connection point pd Subsequently, the input voltage controller obtains the d-axis current reference value i. dref The q-axis reference voltage E generated by the power outer loop q Subtract the q-axis voltage u at the grid connection point pq Then, the input voltage controller obtains the q-axis current reference value i. qref The d-axis reference voltage E generated by the power outer loop d With the d-axis voltage u at the grid connection point pd The difference is used to obtain the d-axis voltage deviation; the q-axis reference voltage E is generated by the power outer loop. q With the q-axis voltage u at the grid connection point pq The difference is calculated to obtain the q-axis voltage deviation; the above d-axis and q-axis voltage deviations are then used to generate the d-axis and q-axis current feedforward compensation values ​​i by the input current feedforward compensation module. df with i qf ; The current feedforward compensation calculation module adopts a dq-axis coupled virtual impedance dynamic implementation structure, which includes virtual resistance. Virtual inductance Inertial links and cross-coupling terms ;in, The rated angular frequency; this module calculates the d-axis current feedforward compensation value i based on the d-axis and q-axis voltage deviations and the cross-coupling relationship between the d-axis and q-axis current feedforward compensation values. df With q-axis current feedforward compensation value i qf ; The current feedforward compensation values ​​for the d-axis and q-axis satisfy the following relationship:

2. d-axis current reference value i dref With d-axis current feedforward compensation value i df The summation yields the total d-axis current setpoint i. dref_t d-axis current total setpoint i dref_t Subtract the inverter output d-axis current i Ld The resulting difference is processed by the current controller and outputs a d-axis modulation signal m. d ; q-axis current reference value i qref With q-axis current feedforward compensation value i qf The summation yields the total q-axis current setpoint i. qref_t q-axis current total setpoint i qref_t Subtract the inverter output q-axis current i Lq The difference obtained is processed by the current controller and output as a q-axis modulated signal m. q The inverter drive signal is obtained by pulse width modulation of the modulated signal.

3. The virtual synchronous generator control method for improving power transmission capability according to claim 1, characterized in that, By introducing a current feedforward compensation calculation module, when the control system reaches steady state, the current feedforward compensation calculation module does not affect the steady-state gain from the power outer loop output reference voltage to the grid connection point voltage and the equivalent impedance between the inverter and the grid.

4. The virtual synchronous generator control method for improving power transmission capability according to claim 2, characterized in that, In a voltage-current dual closed-loop circuit, the voltage controller's setpoint does not introduce the grid connection point current multiplied by the virtual impedance Z. v (s) The compensation voltage generated; the d-axis current reference value i output by the voltage controller. dref and the current reference value i along the q-axis qref The following voltage difference input voltage controllers process the data to obtain the d-axis voltage reference value E. d With the d-axis voltage u at the grid connection point pd The difference, q-axis voltage reference value E q With the q-axis voltage u at the grid connection point pq The difference is expressed as follows:

5. Among them, The transfer function of the voltage controller is the current reference value output by the voltage controller plus the current feedforward compensation value generated by the current feedforward compensation calculation module, which serves as the total reference value of the current controller.

6. The virtual synchronous generator control method for improving power transmission capability according to claim 3, characterized in that, The current feedforward compensation calculation module is implemented using a dynamic structure of dq-axis coupled virtual impedance: the coupled virtual impedance includes a virtual resistance. Virtual inductance Inertial links and cross-coupling terms ;in, The rated angular frequency; this module calculates i based on the voltage deviations of the d-axis and q-axis, combined with the cross-coupling relationship between the current feedforward compensation values ​​of the d-axis and q-axis. df with i qf ; The current feedforward compensation values ​​for the d-axis and q-axis satisfy the following relationship:

7. The current reference value output by the voltage controller, plus the current feedforward compensation value generated by the current feedforward compensation calculation module, is used as the total reference value of the current controller. Subtracting the inverter output current value and inputting the result back into the current controller yields the modulation voltage, expressed as:

8. Among them, Given the transfer function of the current controller, the expression for the grid connection point voltage at this time can be obtained as follows:

9. Where H(s) is the gain from the power outer loop output reference voltage to the grid connection point voltage, and Z... o (s) represents the equivalent impedance between the grid connection point and the inverter; At this time, the voltage gain H(s) and the inner loop output impedance Z o The expression for (s) is: in, E dq (s), i Ldq (s), i pdq (s) and u pdq (s) represent the d-axis and q-axis component expressions for the reference voltage generated by the power outer loop, the inverter output current, the grid connection point current, and the grid connection point voltage, respectively; K pwm L is the inverter's equivalent gain. f C f With R f These are the filter inductance, filter capacitor, and damping resistor of the filter, respectively. A virtual impedance is generated for the current feedforward compensation calculation module; whereby, , and These are the virtual resistance and virtual inductance in the virtual impedance, respectively.

10. The generator control method for improving grid impedance adaptability and power transmission capability according to claim 1, characterized in that, The steady-state gain of the control loop is: voltage steady-state gain: H(s=j0) = 1; equivalent impedance Z between the grid connection point and the inverter. o (s=j0) = 0; at this time, the expression for the active power output of the inverter is:

11. Among them, U g L represents the amplitude of the grid voltage. g For the mains inductance, This represents the phase angle difference between the grid voltage and the reference voltage generated by the power outer loop; since the steady-state value of the equivalent impedance between the grid connection point and the inverter is 0, the denominator of the expression for the active power P output by the inverter only includes the grid impedance ω. n L g Unaffected by virtual impedance This significantly improves the transmission capacity of active power, thus mitigating the impact of [the pandemic / influence]. At this time, the inverter's active power output transmission limit power P max for: 。 12. A non-transitory computer-readable storage medium, characterized in that, The non-transitory computer-readable storage medium is used to store computer instructions, which, when executed by a processor, implement the virtual synchronous generator control method for improving power transmission capability as described in any one of claims 1-5.

13. A computer device, characterized in that, The system includes a memory and a processor, which communicate with each other. The memory stores program instructions that can be executed by the processor, and the processor calls the program instructions to execute the virtual synchronous generator control method for improving power transmission capability as described in any one of claims 1-5.

14. An electronic device, characterized in that, include: The device includes a processor, a memory, and a computer program; wherein the processor is connected to the memory, the computer program is stored in the memory, and when the electronic device is running, the processor executes the computer program stored in the memory to cause the electronic device to execute instructions for implementing the virtual synchronous generator control method for improving power transmission capability as described in any one of claims 1-5.

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