A power oscillation suppression system and method based on inertia link

Abstract

The present application provides a power oscillation suppression system and method based on an inertia link, which includes a power calculation module for calculating reactive power and active power based on the collected grid-connected voltage and grid-connected current; a reactive-voltage loop for calculating the reactive-voltage loop output electromotive force based on the reactive power and the reactive power loop control equation after adding the rated voltage; an active-frequency loop for calculating a first difference between the active power and the active power setting value, multiplying the first difference by an adjustment coefficient to obtain a second power adjustment coefficient, calculating a second phase correction value based on the second power adjustment coefficient, and calculating the active-frequency loop output phase based on the first phase correction value and the second phase correction value; a pulse width PWM modulation module for controlling the start and stop of the virtual synchronous generator based on a three-phase modulation wave signal to solve the problem that the control of the VSG is difficult to take into account both transient and steady-state properties at the same time, and the optimization effect of dynamic stability is not obvious.

Description

Technical Field

[0001] The present invention relates to the field of novel electric power technology, and in particular to a power oscillation suppression system and method based on an inertia link. Background Art

[0002] VSG (Virtual Synchronous Generator) systems have become one of the main development trends in the power industry. Renewable energy generation, represented by photovoltaic and wind power, is a key focus of VSG system development. However, VSG systems use power electronics as grid-connected interfaces, failing to provide inertia and damping support for the system. This results in low inertia and weak damping characteristics for the power system as a whole, significantly impacting the stability of power grids with high renewable energy penetration. As a technology that can effectively simulate the inertia and damping characteristics of synchronous generators, VSG research is particularly important for the stability of renewable energy grid integration.

[0003] While VSGs improve the system's transient response characteristics by constructing rotor motion equations to obtain virtual inertia and damping, they also introduce the synchronous machine's rotor oscillation characteristics, which can lead to power oscillations in the system. Currently, methods for suppressing transient power and frequency oscillations caused by VSG disturbances typically employ methods such as increasing the fixed damping coefficient or employing parameter adaptation and transient damping. However, while increasing the fixed damping coefficient suppresses transient oscillations, it also increases the system's steady-state error. Parameter adaptation is a nonlinear control method, requiring complex parameter design. While transient damping does not increase the system's steady-state error and generally requires simple parameter design, its control process can result in significant active power overshoot, particularly significant frequency overshoot. Existing VSG control methods struggle to balance both transient and steady-state performance, and their effectiveness in optimizing the VSG's dynamic stability is limited.

[0004] Therefore, it is urgent to propose a power oscillation suppression system and method based on the inertia link to solve the technical problems that it is difficult to simultaneously take into account the transient and steady-state properties of VSG control, and the optimization effect of VSG dynamic stability is not obvious. Summary of the Invention

[0005] In order to overcome the problems existing in the related art, the present disclosure provides a power oscillation suppression system and method based on the inertia link to solve the technical problems in the related art that the control of VSG is difficult to take into account both transient and steady-state properties at the same time, and the optimization effect of VSG dynamic stability is not obvious.

[0006] One or more embodiments of this specification provide a power oscillation suppression system based on an inertia link. The system includes a power calculation module, a reactive-voltage loop module, an active-frequency loop module, a virtual impedance control loop module, a voltage-current dual closed-loop module, and a pulse width PWM modulation module. The system is characterized by:

[0007] The power calculation module is used to calculate reactive power and active power based on the collected grid voltage and grid current, and feed back the reactive power to the reactive-voltage loop and the active power to the active-frequency loop;

[0008] The reactive power-voltage loop is used to calculate the output electromotive force of the reactive power-voltage loop based on the reactive power and the reactive power loop control equation after adding the rated voltage;

[0009] The active power-frequency loop is configured to calculate a first difference between the active power and the active power set value, multiply the first difference by an adjustment coefficient and perform a differential calculation to obtain a second difference, sum the first difference and the second difference to calculate a first phase correction value, multiply the first difference by the adjustment coefficient to obtain a second power adjustment coefficient, calculate a second phase correction value based on the second power adjustment coefficient, and calculate the output phase of the active power-frequency loop based on the first phase correction value and the second phase correction value;

[0010] The virtual impedance control loop is used to obtain dq-axis control voltage components by Park transformation based on the grid-connected current and the electromotive force output by the reactive-voltage loop;

[0011] The voltage-current dual closed-loop module is used to control the grid-connected current and grid-connected voltage according to the obtained active-frequency loop output phase and the dq-axis control voltage component output by the virtual impedance control loop to obtain a three-phase modulated wave signal, drive the inverter to operate, and realize the virtual synchronous generator VSG grid-connected control and active oscillation suppression;

[0012] The pulse width PWM modulation module is used to start and stop the virtual synchronous generator according to the three-phase modulation wave signal.

[0013] Preferably, the reactive-voltage loop includes a first calculation unit and an electromotive force output unit;

[0014] The first calculation unit is used to calculate a third difference between the reactive power and the reactive setting value;

[0015] The electromotive force output unit is used to divide the third difference by the reactive droop coefficient and then perform an integral calculation, add the integral calculation result to the rated voltage, and then subtract the output voltage to obtain the output electromotive force.

[0016] Preferably, the active power-frequency loop includes a second calculation unit, a coefficient adjustment unit, a power difference calculation unit, a first phase calculation unit, a second phase calculation unit and a phase output unit;

[0017] The second calculation unit is used to calculate a first difference between the active power and the active power setting value;

[0018] The coefficient adjustment unit is configured to multiply the first difference by an adjustment coefficient;

[0019] The power difference calculation unit is configured to perform a differential operation on a result of the coefficient adjustment to obtain a second difference, and to sum the first difference and the second difference to obtain a power difference;

[0020] The first phase calculation unit is configured to divide the power difference by the rated angular frequency and then multiply the result by a first-order lag link to obtain a first power adjustment coefficient, multiply the first power adjustment coefficient by the power control coefficient to obtain an angular frequency difference, add the angular frequency difference to the rated angular frequency to obtain an output angular frequency, and then integrate the output angular frequency to obtain a first phase correction value;

[0021] The second phase calculation unit is configured to multiply the first difference after coefficient adjustment by the adjustment coefficient to obtain a power adjustment coefficient, and multiply the power adjustment coefficient by the power difference feedforward coefficient to obtain a second phase correction value;

[0022] The phase output unit is used to calculate and obtain the active power-frequency loop output phase according to the first phase correction value and the second phase correction value.

[0023] Preferably, the virtual impedance control loop includes a Park transformation unit, a d-axis control voltage component calculation unit and a q-axis control voltage component calculation unit;

[0024] The Parker transformation unit is used to perform Parker transformation on the collected grid-connected current and the obtained active power-frequency loop output phase to obtain a d-axis current component and a q-axis current component;

[0025] The d-axis control voltage component calculation unit is used to multiply the d-axis current component by a coupling term, add the result to the output electromotive force, and then subtract the product of the d-axis current component and the virtual resistance to obtain the d-axis control voltage component;

[0026] The q-axis control voltage component calculation unit is used to obtain the q-axis control voltage component by adding the product of the q-axis current component and the virtual resistance and the product of the q-axis current component and the coupling term and then negating the sum.

[0027] Preferably, the adjustment coefficient has a value range of 0.01 to 0.12, and the lag time constant in the first-order lag link has a value range of 0 to 0.02.

[0028] One or more embodiments of this specification provide a method for suppressing power oscillations based on an inertia link, comprising the following steps:

[0029] Calculating reactive power and active power based on the collected grid voltage and grid current, and feeding back the reactive power to the reactive-voltage loop and the active power to the active-frequency loop;

[0030] Calculating the reactive-voltage loop output electromotive force based on the reactive power and the reactive power loop control equation after adding the rated voltage;

[0031] Calculating a first difference between the active power and the active power set value, multiplying the first difference by an adjustment coefficient and performing a differential calculation to obtain a second difference, summing the first difference and the second difference to calculate a first phase correction value, multiplying the first difference by the adjustment coefficient to obtain a second power adjustment coefficient, calculating a second phase correction value based on the second power adjustment coefficient, and calculating an active-frequency loop output phase based on the first phase correction value and the second phase correction value;

[0032] Obtaining dq-axis control voltage components through Park transformation based on the grid-connected current and the electromotive force output by the reactive-voltage loop;

[0033] According to the obtained active-frequency loop output phase and the dq-axis control voltage component output by the virtual impedance control loop, the grid-connected current and grid-connected voltage are controlled to obtain a three-phase modulated wave signal, and the inverter is driven to operate, so as to realize the virtual synchronous generator (VSG) grid-connected control and active oscillation suppression;

[0034] The virtual synchronous generator is started and stopped according to the three-phase modulation wave signal.

[0035] Preferably, the reactive power-voltage loop output electromotive force is calculated based on the reactive power and the reactive power loop control equation after adding the rated voltage, comprising the following steps:

[0036] Calculating a third difference between the reactive power and the reactive setting value;

[0037] The third difference is divided by the reactive droop coefficient and then integrated. The integrated calculation result is added to the rated voltage, and then the output voltage is subtracted to obtain the output electromotive force.

[0038] Preferably, the calculating of a first difference between the active power and the active power setting value, multiplying the first difference by an adjustment coefficient and performing a differential calculation to obtain a second difference, summing the first difference and the second difference to calculate a first phase correction value, multiplying the first difference by an adjustment coefficient to obtain a second power adjustment coefficient, calculating a second phase correction value based on the second power adjustment coefficient, and obtaining the active-frequency loop output phase by calculating according to the first phase correction value and the second phase correction value comprises the following steps:

[0039] Calculating a first difference between the active power and an active power setting value;

[0040] multiplying the first difference by an adjustment coefficient;

[0041] Performing a differential operation on the result of the coefficient adjustment to obtain a second difference, and summing the first difference and the second difference to obtain a power difference;

[0042] The power difference is divided by the rated angular frequency and then multiplied by a first-order lag link to obtain a first power adjustment coefficient. The first power adjustment coefficient is multiplied by a power control coefficient to obtain an angular frequency difference. The angular frequency difference is added to the rated angular frequency to obtain an output angular frequency. The output angular frequency is then integrated to obtain a first phase correction value.

[0043] The power adjustment coefficient is obtained by multiplying the first difference value after coefficient adjustment by the adjustment coefficient, and the power adjustment coefficient is multiplied by the power difference feedforward coefficient to obtain a second phase correction value;

[0044] The active power-frequency loop output phase is calculated based on the first phase correction value and the second phase correction value.

[0045] Preferably, the electromotive force based on the grid-connected current and the reactive-voltage loop output is transformed into a dq-axis control voltage component by Park transformation, comprising the following steps:

[0046] The collected grid-connected current and the obtained active power-frequency loop output phase are subjected to Park transformation to obtain the d-axis current component and the q-axis current component;

[0047] Multiplying the d-axis current component by the coupling term, adding the result to the output electromotive force, and then subtracting the product of the d-axis current component and the virtual resistance to obtain the d-axis control voltage component;

[0048] The q-axis control voltage component is obtained by adding the product of the q-axis current component and the virtual resistance and the product of the q-axis current component and the coupling term and then negating the sum.

[0049] Preferably, the adjustment coefficient has a value range of 0.01 to 0.12, and the lag time constant in the first-order lag link has a value range of 0 to 0.02.

[0050] One or more embodiments of this specification provide a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, a power oscillation suppression system based on an inertia link as described above is implemented.

[0051] One or more embodiments of this specification provide a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, the steps of the above-mentioned power oscillation suppression system based on an inertia link are implemented.

[0052] The present disclosure provides a power oscillation suppression system and method based on an inertia link, which has the advantages that the power calculation module is used to calculate reactive power and active power based on the collected grid-connected voltage and grid-connected current, and feed back the reactive power to the reactive-voltage loop and the active power to the active-frequency loop, thereby constructing a reactive-voltage loop, an active-frequency loop optimized based on the inertia link, a virtual impedance control loop, and a voltage-current dual closed-loop system; the reactive-voltage loop is used to calculate the reactive-frequency loop based on the reactive power and the reactive power loop control equation after adding the rated voltage. The voltage loop outputs electromotive force to realize the output voltage and reactive power control of the VSG system; the active-frequency loop is used to calculate the first difference between the active power and the active power setting value, multiply the first difference by the adjustment coefficient and perform differential calculation to obtain the second difference, sum the first difference and the second difference to calculate the first phase correction value, multiply the first difference by the adjustment coefficient to obtain the second power adjustment coefficient, calculate the second phase correction value based on the second power adjustment coefficient, and calculate the active-frequency loop output phase according to the first phase correction value and the second phase correction value. , provides the VSG with virtual inertia and virtual damping that simulate the synchronous generator rotor motion equation, while enhancing the dynamic stability of the VSG and solving the active oscillation problem of the VSG under active power instructions and grid frequency disturbances; the virtual impedance control loop is used to obtain the dq axis control voltage component based on the grid-connected current and the electromotive force output by the reactive-voltage loop through Park transformation, and converts the variables in the three-phase AC system from the static three-phase coordinate system to the rotating dq coordinate system, which can more conveniently analyze and control the operation of power equipment such as synchronous motors; the voltage and current double closed The loop module is used to control the grid-connected current and grid-connected voltage according to the obtained active-frequency loop output phase and the dq-axis control voltage component output by the virtual impedance control loop to obtain a three-phase modulated wave signal, drive the inverter to operate, and realize the virtual synchronous generator VSG grid-connected control and active oscillation suppression; the pulse width PWM modulation module is used to start and stop the virtual synchronous generator according to the three-phase modulated wave signal, realize VSG grid-connected control and active oscillation suppression, and supply power to the load, effectively realizing the decoupling of VSG active power and reactive power, and improving the reliability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In order to more clearly illustrate one or more embodiments of this specification or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in this specification. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0054] Figure 1A structural diagram of a power oscillation suppression system based on an inertia link provided in one or more embodiments of this specification;

[0055] Figure 2 A control block diagram of a power oscillation suppression system based on an inertia link according to one or more embodiments of this specification;

[0056] Figure 3 A schematic diagram comparing the active power of a virtual synchronous generator (VSG) before and after optimization of the inertia link provided in one or more embodiments of this specification;

[0057] Figure 4 A schematic diagram comparing the frequency responses of a virtual synchronous generator (VSG) before and after the inertia link is optimized according to one or more embodiments of this specification;

[0058] Figure 5 A schematic diagram comparing the active power of a virtual synchronous generator (VSG) using the method provided in one or more embodiments of this specification and similar methods;

[0059] Figure 6 A schematic diagram comparing the frequency responses of a virtual synchronous generator (VSG) using the method provided in one or more embodiments of this specification and similar methods;

[0060] Figure 7 A schematic flow chart of a power oscillation suppression system based on an inertia link according to one or more embodiments of this specification;

[0061] Figure 8 A schematic diagram of the structure of a computer device provided in one or more embodiments of this specification. DETAILED DESCRIPTION

[0062] In order to help those skilled in the art better understand the technical solutions in one or more embodiments of this specification, the technical solutions in one or more embodiments of this specification will be clearly and completely described below in conjunction with the drawings in one or more embodiments of this specification. Obviously, the described embodiments are only part of the embodiments of this specification, not all of the embodiments. Based on one or more embodiments of this specification, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of this invention.

[0063] The present invention will be described in detail below with reference to specific implementation methods and the accompanying drawings.

[0064] System Example

[0065] According to an embodiment of the present invention, a power oscillation suppression system based on an inertia link is provided, such as Figure 1As shown in the figure, it is a structural diagram of the power oscillation suppression system based on the inertia link provided in this embodiment. According to the power oscillation suppression system based on the inertia link according to the embodiment of the present invention, the system includes a power calculation module, a reactive-voltage loop module, an active-frequency loop module, a virtual impedance control loop module, a voltage-current dual closed-loop module and a pulse width PWM modulation module.

[0066] In the VSG system, the DC power supply U dc As the energy source of the VSG main circuit, through the main circuit inverter, filter inductor L f and filter capacitor C f The three-phase AC current then passes through the line impedance L g The power calculation module 11 is used to calculate the grid voltage u based on the collected grid voltage u abc and grid-connected current i abc , calculate the reactive power Q e and active power P e .

[0067] The reactive power-voltage loop 12 is used to generate a voltage according to the reactive power Q e And the reactive power loop control equation after adding the rated voltage u0, the reactive-voltage loop output electromotive force E is calculated.

[0068] The active power-frequency loop 13 is used to calculate the active power P e and active power setting value P ref The first difference ΔP1 is multiplied by the adjustment coefficient k p The first phase correction value θ1 is calculated by summing the first difference ΔP1 and the second difference ΔP2, and multiplying the first difference ΔP1 by the adjustment coefficient k. p A second power adjustment coefficient ΔH2 is obtained, a second phase correction value θ2 is calculated based on the second power adjustment coefficient ΔH2, and an active-frequency loop output phase θ is obtained by calculation according to the first phase correction value θ1 and the second phase correction value θ2.

[0069] The virtual impedance control loop 14 is used to control the grid current i abc , and the output electromotive force E of the reactive-voltage loop are transformed by Park to obtain the dq axis control voltage component u dref ,u qref .

[0070] The voltage-current dual closed loop module 15 is used to obtain the active-frequency loop output phase θ and the dq axis control voltage component output by the virtual impedance control loop, u dref ,u qref The grid-connected current i abc, grid-connected voltage u abc Control is performed to obtain a three-phase modulated wave signal.

[0071] The pulse width PWM modulation module 16 is used to start and stop the virtual synchronous generator according to the three-phase modulation wave signal.

[0072] In the system provided by this embodiment, the power calculation module is used to calculate reactive power and active power based on the collected grid-connected voltage and grid-connected current, and feed back the reactive power to the reactive-voltage loop and the active power to the active-frequency loop, thereby constructing a reactive-voltage loop, an active-frequency loop based on inertia link optimization, a virtual impedance control loop, and a voltage-current dual closed-loop system; the reactive-voltage loop is used to calculate the reactive-voltage loop output electromotive force based on the reactive power and the reactive power loop control equation after adding the rated voltage, thereby realizing the output voltage and reactive power control of the VSG system; the active-frequency loop is used to calculate a first difference between the active power and the active power set value, multiply the first difference by the adjustment coefficient and perform differential calculation to obtain a second difference, sum the first difference and the second difference to calculate a first phase correction value, multiply the first difference by the adjustment coefficient to obtain a second power adjustment coefficient, calculate a second phase correction value based on the second power adjustment coefficient, and calculate the active-frequency loop output phase based on the first phase correction value and the second phase correction value, thereby providing a simulated synchronous control system for the VSG. The virtual inertia and virtual damping of the step-by-step generator rotor motion equation are combined to enhance the dynamic stability of the VSG and solve the active oscillation problem of the VSG under active power instructions and grid frequency disturbances; the virtual impedance control loop is used to obtain the dq axis control voltage component based on the grid-connected current and the electromotive force output by the reactive-voltage loop through Park transformation, and convert the variables in the three-phase AC power system from the static three-phase coordinate system to the rotating dq coordinate system, which can more conveniently analyze and control the operation of power equipment such as synchronous motors; the voltage and current dual closed-loop module is used According to the obtained active-frequency loop output phase and the dq-axis control voltage component output by the virtual impedance control loop, the grid-connected current and grid-connected voltage are controlled to obtain a three-phase modulated wave signal, and the inverter is driven to operate to achieve virtual synchronous generator VSG grid-connected control and active oscillation suppression; the pulse width PWM modulation module is used to start and stop the virtual synchronous generator according to the three-phase modulated wave signal, achieve VSG grid-connected control and active oscillation suppression, and supply power to the load, effectively achieving the decoupling of VSG active power and reactive power, and improving the reliability of the system.

[0073] In one embodiment, the reactive-voltage loop 12 includes a first calculation unit 121 and an electromotive force output unit 122 .

[0074] The first calculation unit 121 is used to calculate the reactive power Qe and reactive power setting value Q ref The third difference.

[0075] The electromotive force output unit 122 is used to divide the third difference by the reactive droop coefficient J q Then perform the integral calculation 1 / s, add the integral calculation result to the rated voltage u0, and then subtract the output voltage u t The output electromotive force E is obtained. The calculation formula of the output electromotive force E is:

[0076]

[0077] The system provided in this embodiment realizes the output voltage and reactive power control of the virtual synchronous generator (VSG) system through the reactive-voltage loop module.

[0078] In one embodiment, the active power-frequency loop 13 includes a second calculation unit 131 , a coefficient adjustment unit 132 , a power difference calculation unit 133 , a first phase calculation unit 134 , a second phase calculation unit 135 and a phase output unit 136 .

[0079] The second calculation unit 131 is used to calculate the active power P e and active power setting value P ref The first difference ΔP1.

[0080] The coefficient adjustment unit 132 is used to multiply the first difference ΔP1 by the adjustment coefficient k p .

[0081] The power difference calculation unit 133 is configured to perform a differential operation on the result of the coefficient adjustment to obtain a second difference ΔP2. The first difference ΔP1 and the second difference ΔP2 are summed to obtain a power difference ΔP. The power difference ΔP is expressed as follows:

[0082] ΔP=(1+k p s)(P ref -P e );

[0083] Among them, k p represents the adjustment coefficient, s represents the differential link, P ref Represents the active power setting value, P e Represents the output active power.

[0084] The first phase calculation unit 134 is configured to divide the power difference ΔP by the rated angular frequency ω0 and then multiply the result by a first-order lag 1 / τs+1 with a lag time constant τ to obtain a first power adjustment coefficient ΔH1. The first power adjustment coefficient ΔH1 is multiplied by the power control coefficient to obtain an angular frequency difference Δω. The angular frequency difference Δω is added to the rated angular frequency ω0 to obtain an output angular frequency ω. The output angular frequency ω is then integrated to obtain a first phase correction value θ1. The expression of the power control coefficient is:

[0085]

[0086] Among them, J p is the inertia time constant, D p is the damping coefficient, k f is the primary frequency modulation coefficient.

[0087] The second phase calculation unit 135 is configured to multiply the first difference ΔP1 after coefficient adjustment by the adjustment coefficient k p Then the power adjustment coefficient ΔH2 is obtained, and the power adjustment coefficient ΔH2 is multiplied by the power difference feedforward coefficient to obtain the second phase correction value θ2. The expression of the power difference feedforward coefficient is:

[0088]

[0089] The phase output unit 136 is configured to calculate the active power-frequency loop output phase θ according to the first phase correction value θ1 and the second phase correction value θ2. The expression for obtaining the active power-frequency loop output phase θ is:

[0090]

[0091] Among them, the adjustment coefficient k p The value range of is 0.01 to 0.12, and the value range of the lag time constant τ in the first-order lag link is 0 to 0.02.

[0092] The system provided in this embodiment solves the active power oscillation problem under grid frequency disturbance through the active power-power loop, thereby enhancing the dynamic stability of the virtual synchronous generator (VSG).

[0093] In one embodiment, the virtual impedance control loop 14 includes a Park transformation unit 141 , a d-axis control voltage component calculation unit 142 , and a q-axis control voltage component calculation unit 143 .

[0094] The Parker conversion unit 141 is used to convert the collected grid-connected current i abc Perform Park transformation on the active-frequency loop output phase θ to obtain the d-axis current component i d and the q-axis current component iq .

[0095] The d-axis control voltage component calculation unit 142 is used to convert the d-axis current component i d Multiply by the coupling term ωL v , then add it to the output electromotive force E, and then subtract the d-axis current component i d With the virtual resistor R v The product of the d-axis control voltage component u is obtained dref , L v is the virtual inductor.

[0096] The q-axis control voltage component calculation unit 143 is used to convert the q-axis current component i q With the virtual resistor R v The product of the q-axis current component i q and the coupling term ωL v The q-axis control voltage component u is obtained by adding the product and taking the negative. qref , the expressions of the dq axis control voltage components are:

[0097]

[0098] Where ω represents the output angular frequency, L v represents virtual inductance, i d represents the d-axis current component, i q Represents the q-axis current component.

[0099] The system provided in this embodiment effectively achieves the decoupling of active power and reactive power of the virtual synchronous generator VSG by introducing a virtual impedance control loop in the improved virtual synchronous generator VSG control, further reduces active oscillation, and improves system reliability.

[0100] The following is a further explanation of this solution through a specific case:

[0101] Case 1:

[0102] like Figure 3 As shown, it is a schematic diagram comparing the active power of the virtual synchronous generator VSG before and after the optimization of the inertia link is introduced in this embodiment. The operating condition of the virtual synchronous generator VSG is set as the active power instruction changes from 50kW to 100kW in a step manner at 3s, and the grid frequency drops from 50Hz to 49.95Hz in 6s.

[0103] When the active power instruction or grid frequency disturbance occurs, the active closed-loop small signal model of this embodiment is:

[0104]

[0105] Where K = 3Ug E / X is the voltage regulation coefficient of the virtual synchronous generator VSG, X is the grid impedance of the virtual synchronous generator VSG, ω g is the grid angular frequency, U g is the grid voltage.

[0106] When the grid frequency is inconsistent with the system frequency, the system steady-state error is:

[0107] ΔP e0 =(P e -P ref )| s→0 =(D p ω0+k f )(ω0-ω g );

[0108] This is consistent with the steady-state error of the model when this method is not added, which means that the introduction of the method of this embodiment will not increase the steady-state error. Figure 3 It can be seen that before the introduction of inertia link optimization, the output active power of the virtual synchronous generator VSG has a large overshoot and a long adjustment time. After the introduction of inertia link optimization, the output active power of the virtual synchronous generator VSG has basically no overshoot, the adjustment time is greatly shortened, and the steady-state error is not increased.

[0109] Case 2:

[0110] like Figure 4 The figure shows a comparison diagram of the frequency response of the virtual synchronous generator VSG before and after the optimization of the inertia link provided in this embodiment. The working condition of the virtual synchronous generator VSG is set to the active power command step change from 50kW to 100kW at 3s, and the grid frequency drops from 50Hz to 49.95Hz at 6s. Figure 3 It can be seen that before the introduction of inertia link optimization, the output frequency of the virtual synchronous generator VSG had obvious oscillation at 3s, large overshoot, and long adjustment time. After the introduction of inertia link optimization, the output frequency of the virtual synchronous generator VSG had no oscillation, the overshoot and adjustment time were greatly reduced, and the frequency response at 6s was also significantly optimized.

[0111] Case 3:

[0112] like Figure 5 As shown in FIG, it is a schematic diagram comparing the active power of the virtual synchronous generator VSG provided by the method of this embodiment and similar methods. The working condition of the virtual synchronous generator VSG is set as the active power instruction changes from 50kW to 100kW in 3s, and the grid frequency drops from 50Hz to 49.95Hz in 6s. Figure 5It can be seen that for active power command steps, when each method is adjusted to the optimal value, there is basically no active power overshoot, but the adjustment time of the method provided by this embodiment is significantly faster than that of other methods. For grid frequency drops, the method provided by this embodiment has no overshoot and a fast adjustment time, while the transient damping method and the adaptive method both have small overshoot, and the fixed damping method will produce a large steady-state error.

[0113] Case 4:

[0114] like Figure 6 The figure shows a comparison diagram of the frequency response of the virtual synchronous generator VSG between the method provided in this embodiment and similar methods. The working condition of the virtual synchronous generator VSG is set to the active power instruction step change from 50kW to 100kW at 3s, and the grid frequency drops from 50Hz to 49.95Hz at 6s. Figure 6 It can be seen that for active power command steps, the frequency response of the method of this embodiment has no oscillation, and the overshoot and adjustment time are significantly smaller than those of other methods; for grid frequency drops, the lowest frequency point of the method of this embodiment is significantly higher than that of other methods, and the adjustment time is fast.

[0115] Method Example

[0116] According to an embodiment of the present invention, a method for suppressing power oscillation based on an inertia link is provided, such as Figure 7 FIG. 1 is a flow chart of a method for suppressing power oscillations based on an inertia link according to an embodiment of the present invention. The method for suppressing power oscillations based on an inertia link according to an embodiment of the present invention includes the following steps:

[0117] S710 . Calculate reactive power and active power based on the collected grid-connected voltage and grid-connected current, and feed the reactive power back to the reactive-voltage loop, and feed the active power back to the active-frequency loop.

[0118] S720: Calculate the reactive-voltage loop output electromotive force E according to the reactive power and the reactive power loop control equation after adding the rated voltage.

[0119] S730. Calculate a first difference between the active power and the active power setting value, multiply the first difference by an adjustment coefficient and perform differential calculation to obtain a second difference, sum the first difference and the second difference to calculate a first phase correction value, multiply the first difference by an adjustment coefficient to obtain a second power adjustment coefficient, calculate a second phase correction value based on the second power adjustment coefficient, and obtain the active-frequency loop output phase according to the first phase correction value and the second phase correction value.

[0120] S740. Obtain dq-axis control voltage components based on the grid-connected current and the electromotive force output by the reactive-voltage loop through Park transformation.

[0121] S750. Based on the obtained active-frequency loop output phase and the dq-axis control voltage component output by the virtual impedance control loop, the grid-connected current and grid-connected voltage are controlled to obtain a three-phase modulated wave signal, and the inverter is driven to operate to achieve virtual synchronous generator VSG grid-connected control and active oscillation suppression.

[0122] S760: Start and stop the virtual synchronous generator according to the three-phase modulation wave signal.

[0123] The method provided in this embodiment calculates reactive power and active power based on the collected grid-connected voltage and grid-connected current, and feeds back the reactive power to the reactive-voltage loop and the active power to the active-frequency loop, thereby constructing a reactive-voltage loop, an active-frequency loop based on inertia link optimization, a virtual impedance control loop, and a voltage-current dual closed-loop system; according to the reactive power and the reactive power loop control equation after adding the rated voltage, the reactive-voltage loop output electromotive force E is calculated to realize the output voltage and reactive power control of the VSG system; a first difference between the active power and the active power set value is calculated, and a second difference is obtained by multiplying the first difference by an adjustment coefficient and performing a differential calculation, a first phase correction value is calculated by summing the first difference and the second difference, a second power adjustment coefficient is obtained by multiplying the first difference by an adjustment coefficient, a second phase correction value is calculated based on the second power adjustment coefficient, and an active-frequency loop output phase is calculated based on the first phase correction value and the second phase correction value to provide a phase correction value for the VSG. The invention simulates the virtual inertia and virtual damping of the synchronous generator rotor motion equation, enhances the dynamic stability of the VSG, and solves the active oscillation problem of the VSG under active power instructions and grid frequency disturbances; based on the grid-connected current and the electromotive force output by the reactive-voltage loop, the dq-axis control voltage component is obtained through Park transformation, and the variables in the three-phase AC power system are converted from the static three-phase coordinate system to the rotating dq coordinate system, which can more conveniently analyze and control the operation of power equipment such as synchronous motors; according to the obtained active-frequency loop output phase and the dq-axis control voltage component output by the virtual impedance control loop, the grid-connected current and grid-connected voltage are controlled to obtain a three-phase modulation wave signal, which drives the inverter to operate, so as to realize the grid-connected control and active oscillation suppression of the virtual synchronous generator VSG; according to the three-phase modulation wave signal, the virtual synchronous generator is started and stopped to realize the grid-connected control and active oscillation suppression of the VSG, and power is supplied to the load, effectively realizing the decoupling of the active power and reactive power of the VSG, and improving the reliability of the system.

[0124] In one embodiment, the reactive power-voltage loop output electromotive force E is calculated based on the reactive power and the reactive power loop control equation after adding the rated voltage, comprising the following steps:

[0125] S721. Calculate a third difference between the reactive power and the reactive setting value.

[0126] S722: Divide the third difference by the reactive droop coefficient and perform integration calculation, add the integration calculation result to the rated voltage, and then subtract the output voltage to obtain the output electromotive force.

[0127] The method provided in this embodiment realizes the output voltage and reactive power control of the virtual synchronous generator (VSG) system through the reactive-voltage loop module.

[0128] In one embodiment, the calculating of a first difference between the active power and the active power setting value, multiplying the first difference by an adjustment coefficient and performing a differential calculation to obtain a second difference, summing the first difference and the second difference to calculate a first phase correction value, multiplying the first difference by an adjustment coefficient to obtain a second power adjustment coefficient, calculating a second phase correction value based on the second power adjustment coefficient, and calculating an active-frequency loop output phase according to the first phase correction value and the second phase correction value comprises the following steps:

[0129] S731. Calculate a first difference between the active power and the active power setting value.

[0130] S732: Multiply the first difference by an adjustment coefficient.

[0131] S733: Perform a differential operation on the result of the coefficient adjustment to obtain a second difference, and sum the first difference and the second difference to obtain a power difference.

[0132] S734. Divide the power difference by the rated angular frequency and multiply it by a first-order lag with a lag time constant of τ to obtain a first power adjustment coefficient. Multiply the first power adjustment coefficient by the power control coefficient to obtain an angular frequency difference. Add the angular frequency difference to the rated angular frequency to obtain the output angular frequency. The output angular frequency is then integrated to obtain a first phase correction value. The adjustment coefficient has a value range of 0.01 to 0.12, and the lag time constant in the first-order lag link has a value range of 0 to 0.02.

[0133] S735: Multiply the first difference after coefficient adjustment by the adjustment coefficient to obtain a power adjustment coefficient, and multiply the power adjustment coefficient by the power difference feedforward coefficient to obtain a second phase correction value.

[0134] S736. Calculate and obtain the active-frequency loop output phase according to the first phase correction value and the second phase correction value.

[0135] The method provided in this embodiment solves the active power oscillation problem under grid frequency disturbance through the active power-power loop, thereby enhancing the dynamic stability of the virtual synchronous generator (VSG).

[0136] In one embodiment, the electromotive force based on the grid-connected current and the reactive-voltage loop output is subjected to Park transformation to obtain the dq-axis control voltage component, comprising the following steps:

[0137] The collected grid-connected current and the obtained active power-frequency loop output phase are subjected to Park transformation to obtain the d-axis current component and the q-axis current component.

[0138] The d-axis current component is multiplied by the coupling term, and then added to the output electromotive force, and then the product of the d-axis current component and the virtual resistance is subtracted to obtain the d-axis control voltage component.

[0139] The q-axis control voltage component is obtained by adding the product of the q-axis current component and the virtual resistance and the product of the q-axis current component and the coupling term and then negating the sum.

[0140] The method provided in this embodiment effectively achieves the decoupling of active power and reactive power of the virtual synchronous generator VSG by introducing a virtual impedance control loop in the improved virtual synchronous generator VSG control, further reduces active oscillation, and improves system reliability.

[0141] The embodiment of the present invention is a method embodiment corresponding to the above-mentioned system embodiment. The specific operations of the processing steps of each module can be understood by referring to the description of the system embodiment, and will not be repeated here.

[0142] like Figure 8 As shown, the present invention also provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the power oscillation suppression system based on the inertia link described in the above embodiment is implemented, or when the computer program is executed by a processor, the power oscillation suppression system based on the inertia link described in the above embodiment is implemented. When the computer program is executed by the processor, the above method steps are implemented.

[0143] Those skilled in the art will appreciate that all or part of the processes in the above-mentioned embodiments can be implemented by instructing the relevant hardware through a computer program. The computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, storage, database or other media used in the embodiments provided in this application can include non-volatile and / or volatile memory. Non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM) or flash memory. Volatile memory can include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in various forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link (Synchlink) DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM).

[0144] Each embodiment in this specification is described in a progressive manner. The same or similar parts between the embodiments can be referred to each other. Each embodiment focuses on the differences from other embodiments. In particular, for the device or system embodiments, since they are basically similar to the method embodiments, the description is relatively simple. For the relevant parts, refer to the partial description of the method embodiments. The device and system embodiments described above are merely schematic, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the scheme of this embodiment. A person of ordinary skill in the art can understand and implement it without making any creative efforts.

[0145] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention, and the contents not described in detail in the specification of the present invention are common knowledge to those skilled in the art.

Claims

1. A power oscillation suppression system based on inertia link, characterized in that include: Power calculation module, reactive-voltage loop, active-frequency loop, virtual impedance control loop, voltage and current double closed loop module and pulse width PWM Modulation module; The power calculation module is used to calculate reactive power and active power based on the collected grid voltage and grid current, and feed back the reactive power to the reactive-voltage loop and the active power to the active-frequency loop; The reactive power-voltage loop is used to calculate the output electromotive force of the reactive power-voltage loop based on the reactive power and the reactive power loop control equation after adding the rated voltage; The active power-frequency loop is configured to calculate a first difference between the active power and the active power set value, multiply the first difference by an adjustment coefficient and perform a differential calculation to obtain a second difference, sum the first difference and the second difference to calculate a first phase correction value, multiply the first difference by the adjustment coefficient to obtain a second power adjustment coefficient, calculate a second phase correction value based on the second power adjustment coefficient, and calculate the output phase of the active power-frequency loop based on the first phase correction value and the second phase correction value; The virtual impedance control loop is used to obtain the output of the virtual impedance control loop through Park transformation based on the grid-connected current and the electromotive force output by the reactive-voltage loop. dq Axis control voltage component; The voltage and current double closed loop module is used to output the phase of the active power-frequency loop and the output of the virtual impedance control loop. dq The axis controls the voltage component, controls the grid-connected current and grid-connected voltage to obtain a three-phase modulation wave signal, drives the inverter to operate, and realizes a virtual synchronous generator. VSG Grid connection control and active power oscillation suppression; The pulse width PWM The modulation module is used to control the start and stop of the virtual synchronous generator according to the three-phase modulation wave signal.

2. The power oscillation suppression system based on an inertia link according to claim 1, characterized in that: The reactive-voltage loop includes a first calculation unit and an electromotive force output unit; The first calculation unit is used to calculate a third difference between the reactive power and the reactive setting value; The electromotive force output unit is used to divide the third difference by the reactive droop coefficient and then perform an integral calculation, add the integral calculation result to the rated voltage, and then subtract the output voltage to obtain the output electromotive force.

3. The power oscillation suppression system based on an inertia link according to claim 1, characterized in that: The active power-frequency loop includes a second calculation unit, a coefficient adjustment unit, a power difference calculation unit, a first phase calculation unit, a second phase calculation unit and a phase output unit; The second calculation unit is used to calculate a first difference between the active power and the active power setting value; The coefficient adjustment unit is configured to multiply the first difference by an adjustment coefficient; The power difference calculation unit is configured to perform a differential operation on a result of the coefficient adjustment to obtain a second difference, and to sum the first difference and the second difference to obtain a power difference; The first phase calculation unit is configured to divide the power difference by the rated angular frequency and then multiply the result by a first-order lag link to obtain a first power adjustment coefficient, multiply the first power adjustment coefficient by the power control coefficient to obtain an angular frequency difference, add the angular frequency difference to the rated angular frequency to obtain an output angular frequency, and then integrate the output angular frequency to obtain a first phase correction value; The second phase calculation unit is configured to multiply the first difference by an adjustment coefficient to obtain a power adjustment coefficient, and multiply the power adjustment coefficient by a power difference feedforward coefficient to obtain a second phase correction value; The phase output unit is used to calculate and obtain the active power-frequency loop output phase according to the first phase correction value and the second phase correction value.

4. The power oscillation suppression system based on an inertia link according to claim 1, characterized in that: The virtual impedance control loop includes a Parker transformation unit, d Axis control voltage component calculation unit and q Axis control voltage component calculation unit; The Parker transformation unit is used to perform Parker transformation on the collected grid-connected current and the active-frequency loop output phase to obtain d The shaft current components and q Shaft current component; described d Axis control voltage component calculation unit, used to convert the d The shaft current component is multiplied by the coupling term, added to the output electromotive force, and then subtracted from the d The product of the shaft current component and the virtual resistance is d Axis control voltage component; described q Axis control voltage component calculation unit, used to convert the q The product of the shaft current component and the virtual resistance q The product of the shaft current component and the coupling term is added and then negative to obtain q Axis control voltage component.

5. The power oscillation suppression system based on an inertia link according to claim 3, characterized in that: The adjustment coefficient has a value range of 0.01 to 0.12, and the lag time constant in the first-order lag link has a value range of 0 to 0.

02.

6. A power oscillation suppression method based on an inertia link, characterized in that: The following steps are involved: Based on the collected grid voltage and grid current, reactive power and active power are calculated, and reactive power is fed back to the reactive-voltage loop, and active power is fed back to the active-frequency loop; Calculating the reactive-voltage loop output electromotive force based on the reactive power and the reactive power loop control equation after adding the rated voltage; Calculating a first difference between the active power and the active power set value, multiplying the first difference by an adjustment coefficient and performing a differential calculation to obtain a second difference, summing the first difference and the second difference to calculate a first phase correction value, multiplying the first difference by the adjustment coefficient to obtain a second power adjustment coefficient, calculating a second phase correction value based on the second power adjustment coefficient, and calculating an active-frequency loop output phase based on the first phase correction value and the second phase correction value; The virtual impedance control loop output is obtained by Park transformation based on the grid-connected current and the electromotive force output by the reactive-voltage loop. dq Axis control voltage component; According to the active-frequency loop output phase and the virtual impedance control loop output dq The axis controls the voltage component, controls the grid-connected current and grid-connected voltage to obtain a three-phase modulation wave signal, drives the inverter to operate, and realizes a virtual synchronous generator. VSG Grid connection control and active power oscillation suppression; The start and stop of the virtual synchronous generator are controlled according to the three-phase modulated wave signal.

7. A method for suppressing power oscillation based on an inertia link according to claim 6, characterized in that: The reactive power-voltage loop output electromotive force is calculated based on the reactive power and the reactive power loop control equation after adding the rated voltage, comprising the following steps: Calculating a third difference between the reactive power and the reactive setting value; The third difference is divided by the reactive droop coefficient and then integrated. The integrated calculation result is added to the rated voltage, and then the output voltage is subtracted to obtain the output electromotive force.

8. The method for suppressing power oscillation based on an inertia link according to claim 6, characterized in that: The method comprises the following steps: calculating a first difference between the active power and the active power setting value, multiplying the first difference by an adjustment coefficient and performing a differential calculation to obtain a second difference, summing the first difference and the second difference to calculate a first phase correction value, multiplying the first difference by an adjustment coefficient to obtain a second power adjustment coefficient, calculating a second phase correction value based on the second power adjustment coefficient, and obtaining an active-frequency loop output phase by calculating the first phase correction value and the second phase correction value. Calculating a first difference between the active power and an active power setting value; multiplying the first difference by an adjustment coefficient; Performing a differential operation on the result of the coefficient adjustment to obtain a second difference, and summing the first difference and the second difference to obtain a power difference; The power difference is divided by the rated angular frequency and then multiplied by a first-order lag link to obtain a first power adjustment coefficient. The first power adjustment coefficient is multiplied by a power control coefficient to obtain an angular frequency difference. The angular frequency difference is added to the rated angular frequency to obtain an output angular frequency. The output angular frequency is then integrated to obtain a first phase correction value. Multiplying the first difference by an adjustment coefficient to obtain a power adjustment coefficient, and multiplying the power adjustment coefficient by a power difference feedforward coefficient to obtain a second phase correction value; The active power-frequency loop output phase is calculated based on the first phase correction value and the second phase correction value.

9. The method for suppressing power oscillation based on an inertia link according to claim 6, characterized in that: The electromotive force based on the grid-connected current and the reactive-voltage loop output is obtained by Park transformation dq The axis control voltage component includes the following steps: Perform Park transformation on the collected grid-connected current and the active-frequency loop output phase to obtain d The shaft current components and q Shaft current component; The d The shaft current component is multiplied by the coupling term, added to the output electromotive force, and then subtracted from the d The product of the shaft current component and the virtual resistance is d Axis control voltage component; The q The product of the shaft current component and the virtual resistance q The product of the shaft current component and the coupling term is added and then negative to obtain q Axis control voltage component.

10. The method for suppressing power oscillation based on an inertia link according to claim 8, characterized in that: The adjustment coefficient has a value range of 0.01 to 0.12, and the lag time constant in the first-order lag link has a value range of 0 to 0.02.

Images