Transient support capability improvement strategy of VSG based on active deviation integral feedback

Abstract

The application provides a VSG transient support capability improvement strategy based on active deviation integral feedback, comprising: constructing an active control loop of a VSG based on active power deviation integral feedback; calculating an integral feedback compensation value based on power deviation control based on the active control loop of the VSG; and prolonging the limit fault removal time based on the integral feedback compensation value. The strategy can effectively inhibit the power angle change rate of the VSG during the fault process, prolong the limit fault removal time, and improve the transient power angle stability.

Description

Technical Field

[0001] This application relates to the field of intelligent control technology for distribution networks, and in particular to a strategy for enhancing the transient support capability of VSG based on active power deviation integral feedback. Background Technology

[0002] Currently, most grid-connected inverters for new energy adopt grid-following (GFL) control. However, in weak grid scenarios, GFL inverters are prone to voltage instability and phase synchronization loss, seriously threatening the synchronous stability of the system. To overcome the stability problem of GFLs in weak grids, researchers have proposed grid-forming (GFM) control strategies. Virtual synchronous generators (VSGs), as one of the core controls in grid-forming, possess the rotational inertia and damping characteristics of traditional synchronous generators (SGs), providing voltage and frequency support to the grid, and have become a key solution for distributed renewable energy grid connection. However, when voltage drops occur on the distribution network side, VSGs exhibit transient power angle instability problems similar to those of traditional synchronous generators, which can even lead to VSC disconnection in severe cases. To ensure reliable grid operation, VSGs must have fault ride-through capability during system operation, i.e., continuously providing voltage and frequency support to the distribution network during the fault duration phase. Therefore, in-depth research on optimized control strategies for the transient power angle stability of VSGs during distribution network voltage drops is of great significance.

[0003] Currently, most existing research on the transient power angle stability of VSG focuses on three aspects: adjusting parameters, virtual impedance, and switching control strategies. Existing technologies often improve transient power angle stability by adjusting the active power reference value. However, in the event of a severe voltage drop on the distribution network side, power angle instability may still occur. Summary of the Invention

[0004] This application provides a strategy for enhancing the transient support capability of VSG based on active power deviation integral feedback. To solve the above-mentioned technical problems, this application adopts the following technical method:

[0005] Firstly, this application provides a strategy for enhancing VSG transient support capabilities based on active power deviation integral feedback, including:

[0006] Construct a VSG active power control loop based on active power deviation integral feedback;

[0007] Based on the VSG active power control loop, calculate the integral feedback compensation value based on power deviation control;

[0008] Based on the integral feedback compensation value, the critical fault clearing time is extended.

[0009] Optionally, calculating the integral feedback compensation value based on power deviation control based on the VSG active power control loop includes:

[0010] Obtain the grid frequency reference value and the coefficients based on power deviation integral feedback compensation;

[0011] Based on the power grid frequency reference value and the coefficients for power deviation integral feedback compensation, calculate the integral feedback compensation value based on power deviation control.

[0012] Optionally, the integral feedback compensation value based on power deviation control is calculated based on the grid frequency reference value and the coefficients of the power deviation integral feedback compensation, using the following formula:

[0013] ;

[0014] In the formula, This is the integral feedback compensation value based on power deviation control. The coefficients are based on power deviation integral feedback compensation. For the Laplace operator, This is the reference value for the power grid frequency. This represents the actual value of the VSG virtual rotor angular velocity after power deviation integral feedback compensation. and These are the VSG's active power reference value and actual active power output value, respectively. This is a virtual moment of inertia; is the damping coefficient.

[0015] Optionally, extending the critical fault clearing time based on the integral feedback compensation value includes:

[0016] The virtual power angle is calculated based on the integral feedback compensation value;

[0017] Collect the inverter's output current and the grid connection point PCC voltage under transient conditions;

[0018] Calculate the voltage modulation signal of the VSG system based on the virtual power angle, the inverter output current and the grid connection point PCC voltage.

[0019] Based on the voltage modulation signal of the VSG system, the critical fault clearing time is extended.

[0020] Optionally, based on the virtual power angle, the inverter's output current, and the grid connection point PCC voltage, the voltage modulation signal of the VSG system is calculated, including:

[0021] Calculate the actual output value of the inverter's reactive power based on the inverter's output current;

[0022] Calculate the VSG voltage command value based on the actual reactive power output value of the inverter.

[0023] Based on the VSG voltage command value and virtual power angle, calculate the reference value of the three-phase instantaneous voltage output by the VSG;

[0024] The voltage modulation signal of the VSG system is calculated based on the three-phase instantaneous voltage reference value, the inverter output current and the grid connection point PCC voltage.

[0025] Optionally, the voltage modulation signal based on the VSG system extends the critical fault clearing time by including:

[0026] The voltage modulation signal of the VSG system is transformed to generate a PWM modulation wave;

[0027] By using PWM modulation waves to generate drive signals, the switching transistors are controlled to turn on and off, thus extending the time for clearing extreme faults.

[0028] In a second aspect, this application also provides a computer device, including a memory and a processor, wherein the memory stores a computer program, characterized in that the processor executes the computer program to implement the steps of the VSG transient support capability enhancement strategy based on active power deviation integral feedback as described in any one of the first aspects.

[0029] Thirdly, this application also provides a computer storage medium storing computer program code, characterized in that the computer program code, when executed by a processor, implements the VSG transient support capability enhancement strategy based on active power deviation integral feedback as described in any of the first aspects.

[0030] This application has the following beneficial effects:

[0031] The strategy proposed in this application can effectively suppress the rate of change of the power angle of the VSG during the fault process, prolong the ultimate fault clearing time, and improve the transient power angle stability. Attached Figure Description

[0032] Figure 1 A schematic diagram of the VSG system control loop provided in an embodiment of this application;

[0033] Figure 2 The output power angle curves of the VSG before and after considering damping are provided for embodiments of this application. Figure 2 (a) is the output power angle curve of the VSG without considering the damping coefficient; Figure 2 (b) is the output power angle curve of the VSG considering the damping coefficient;

[0034] Figure 3 The VSG output power angle curve provided in the embodiments of this application and curve, Figure 3 (a) Figure 3 (c) are the output power angle curves of VSG under different voltage drop conditions, where curves I, II and III are the output power angle curves of VSG under normal operating conditions (k=1), grid voltage drop to 0.7pu and 0.3pu respectively. Figure 3 (b) Figure 3 (d) shows the voltage drop conditions under curves II and III, respectively. Line graph;

[0035] Figure 4 VSG phase plane diagrams under different J and D conditions in transient situations provided in embodiments of this application. Figure 4 (a) is the VSG phase plane diagram with D=1500 and only J changing; Figure 4 (b) is the VSG phase plane diagram with J=94.2 and only D changing;

[0036] Figure 5 Waveform diagram of the entire process of conventional VSG fault ride-through provided in the embodiments of this application;

[0037] Figure 6 A flowchart illustrating the VSG transient support capability enhancement strategy based on active power deviation integral feedback provided in this application embodiment;

[0038] Figure 7 A schematic diagram of a VSG active power control loop based on active power deviation integral feedback provided in an embodiment of this application;

[0039] Figure 8 The power angle curve after incorporating power deviation integral compensation control is provided in the embodiments of this application;

[0040] Figure 9 The phase plane diagram of VSG when the fault duration is 1 second after being cleared when the strategy of this application is adopted, provided for the embodiments of this application;

[0041] Figure 10 A comparison of transient waveforms of different VSG control strategies when the grid voltage drops to 0.5 pu, as provided in the embodiments of this application. Figure 10 (a) is a transient process waveform diagram using the traditional VSG control strategy; Figure 10 (b) is a transient process waveform diagram under active power deviation integral control adopted in this application;

[0042] Figure 11 A comparison of transient waveforms of different VSG control strategies when the grid voltage drops to 0.3 pu, as provided in the embodiments of this application. Figure 11 (a) is a transient process waveform diagram using the traditional VSG control strategy; Figure 11 (b) is a transient process waveform diagram under active power deviation integral control;

[0043] Figure 12 Waveform diagrams comparing the VSG output power angle and various electrical quantities with the control strategy provided in this application, which employs flexible parameter adjustment for the VSG control provided in this application. Figure 12 (a) Waveforms of the output power angle and various electrical quantities of VSG control with flexible parameter adjustment; Figure 12 (b) is a waveform diagram of the output power angle and various electrical quantities under active power deviation integral control. Detailed Implementation

[0044] To facilitate understanding by those skilled in the art, the present application will be further described below in conjunction with embodiments and accompanying drawings. The content mentioned in the embodiments is not intended to limit the present application.

[0045] To facilitate understanding of the technical solution adopted in this application, a brief explanation of the basic principles and transient characteristic analysis of VSG referenced therein will be provided first:

[0046] VSG basic principle:

[0047] VSG system control loop such as Figure 1 As shown in the figure, VSC uses a constant DC-side voltage. It is connected to the power grid via an LC filter. and These are the inductance and capacitance of the filter, respectively; , and These are the inverter's output current, grid connection point (PCC) voltage, and grid-side voltage under steady-state conditions, respectively. Line reactance; PWM stands for pulse width modulation. S 1- S 6 is the switching transistor.

[0048] right Figure 1 Analysis reveals that the active-frequency and reactive-voltage control equations of the VSG system are given in equations (1) and (2), respectively:

[0049] (1)

[0050] (2)

[0051] In the formula: and These are the VSC's active power reference value and actual active power output value, respectively. and These are the actual and reference values ​​of the virtual rotor angular velocity of the VSG, respectively. and These are the reference value and the actual output value of the inverter's reactive power, respectively. This is the droop coefficient; This is a virtual moment of inertia; The damping coefficient; The phase difference between the grid connection point voltage and the grid voltage, i.e., the virtual power angle, will be referred to as the power angle in the following text; and These represent the VSG rated voltage amplitude and voltage command value, respectively, and the three-phase instantaneous voltage reference value output by the VSG. .

[0052] The VSG port voltage can be represented as a phasor. The grid-side voltage is .in, The power angle, or VSG output voltage, describes the phase lead of the VSG output voltage relative to the grid voltage. Under this condition, it represents the active power output by the VSC to the grid. and reactive power As shown in equations (3) and (4) respectively:

[0053] (3)

[0054] (4)

[0055] In the formula: and These are the VSG output voltage and the mains voltage, respectively. This refers to the line reactance.

[0056] Transient work angle characteristics.

[0057] Traditional equal-area methods can quantitatively analyze and determine transient stability by comparing the sizes of the acceleration and deceleration areas. However, they neglect the influence of the damping coefficient, leading to a conservative assessment of VSG transient stability. To improve the accuracy of VSG transient characteristic analysis, this paper will consider the damping in the system.

[0058] Under fault conditions, let the VSG equivalent active power reference value be... The active-frequency equation of the VSG can then be expressed as:

[0059] (5)

[0060] In the formula, and These are the mains voltage fault value and the VSC voltage fault value, respectively. This represents the active power output value under fault conditions.

[0061] Figure 2 (a) and Figure 2 (b) The output power angle curves of the VSG are shown with and without considering the damping coefficient, respectively. A comparison reveals that the equivalent active power reference value of the VSG... The damping coefficient is dynamically adjusted to reduce the acceleration area of ​​the VSG while increasing the deceleration area, thereby enhancing the transient stability of the VSG. Compared to the more conservative stability assessment without considering the damping coefficient, the transient characteristic analysis results of the VSG system considering the damping coefficient are more accurate.

[0062] According to equation (5), the power angle curves of the VSG under different fault depths can be obtained. Curves Figure 3 As shown. The degree of grid voltage drop can be expressed as follows. It indicates. Among them, This represents the voltage value after a power grid fault.

[0063] Figure 3 (a) and (c) are the output power angle curves of VSG under different voltage drop conditions, where curves I, II and III are the output power angle curves of VSG under normal operating conditions (k=1), grid voltage drop to 0.7pu and 0.3pu, respectively. Figure 3 (b) and (d) correspond to curves under voltage drop conditions II and III, respectively.

[0064] Figure 3 (a) and (b) represent the transiently stable cases of VSG. From Figure 3 (a) It can be seen that after the grid voltage drops, the VSG operating point abruptly changes from point A to point B and enters the acceleration region. As the fault continues, the active power output... Increase, Decrease until the condition is met. Then it enters the deceleration zone. Correspondingly Figure 3 (b) After the grid voltage drops due to a fault, the rate of change of the VSG power angle increases under the influence of the acceleration area, and then gradually decreases after entering the deceleration region.

[0065] Figure 3 (c) and (d) represent the transient instability cases of the VSG. (From...) Figure 3 (c) It can be seen that due to the deep fault drop, the VSG system is in an unstable state because the deceleration area is missing. Figure 3(d) shows that the rate of change of the VSG power angle is always positive, resulting in a continuous monotonically increasing VSG power angle. Therefore, for the transient stability of the VSG, it is necessary not only to have a deceleration area between the reference active power and the output active power curves, but also to ensure that this deceleration area is greater than or equal to the acceleration area.

[0066] After considering damping, the transient stability of the VSG should satisfy:

[0067] (6)

[0068] Based on the above analysis, in order to improve the transient stability of the VSG, it is possible to change the power angle curve of the VSG to reduce the acceleration area and increase the deceleration area.

[0069] Impact of key system parameters on the transient stability characteristics of VSG:

[0070] To comprehensively analyze different moments of inertia during power grid voltage faults and damping coefficient The impact on the transient stability performance of VSG, according to equation (5) regarding The second-order differential equation was used to plot the different voltage drops on the distribution network side. , The VSG phase plane diagram with the values ​​is as follows Figure 4 As shown in the figure The initial power angle of the VSG before the fault; This refers to the overshoot of the power angle; This represents the maximum difference in angular frequency.

[0071] from Figure 4 It can be seen that when a severe voltage drop fault occurs on the distribution network side, if Keep unchanged, increase Effectively reduces transient periods and This value further improves the transient stability performance of the VSG. If Keep unchanged, increase It can also significantly reduce and This is because a larger damping coefficient can accelerate the rate of kinetic energy consumption during VSG faults, thereby reducing the amplitude of power angle changes and suppressing power angle offset, thus improving transient process stability. As the above analysis shows, increasing both inertia and damping can effectively suppress severe voltage drops on the distribution network side. and This effectively improves the transient stability of the VSG. Therefore, by flexibly adjusting... and This can further improve the transient stability performance of VSG.

[0072] When voltage drops occur on the distribution network side, traditional VSGs are prone to transient instability and persistent oscillations after fault clearance, which can lead to system disconnection in severe cases. A typical traditional VSG fault ride-through waveform is shown below. Figure 5 As shown. Based on the above analysis of the transient characteristics of VSG under the condition of voltage drop on the distribution network side, the following conclusions can be drawn: (1) The transient power angle instability of VSG is related to the imbalance difference between the reference active power value and the output active power of VSG. By compensating for the imbalance difference of active power, the acceleration and deceleration area of ​​the system after the voltage drop on the distribution network side can be changed, thereby improving the transient power angle stability; (2) The moment of inertia J and damping coefficient D in the active loop of VSG will affect the power angle change rate and power angle overshoot of the VSG system. Therefore, by taking advantage of the flexible characteristics of VSG parameters, J and D can be flexibly adjusted to further improve the transient stability of VSG.

[0073] Based on the above analysis, in order to solve the problems raised in the background technology, such as Figure 6 As shown, this application proposes a strategy for enhancing the transient support capability of VSG based on active power deviation integral feedback, including:

[0074] Step S101: Construct a VSG active power control loop based on active power deviation integral feedback;

[0075] First, construct as Figure 7 The VSG active power control loop shown is based on active power deviation integral feedback, which adds an additional active power deviation integral control loop to the original VSG active power control loop. During a fault, the VSG active power reference value is... Compared with the actual output value of active power Integrate the deviation between the two values ​​and compare the integral value with the grid frequency reference value. Same as actual VSG output frequency value The deviations are added together to obtain the final composite value. As a compensation, the unbalanced frequency difference is fed back to the active power control loop, from which the improved VSG active power loop can be obtained as follows:

[0076] (7)

[0077] In the formula, This is the integral feedback compensation value based on power deviation control. The coefficients are based on power deviation integral feedback compensation. For the Laplace operator, This is the reference value for the power grid frequency. This represents the actual value of the VSG virtual rotor angular velocity after power deviation integral feedback compensation.

[0078] Step S102: Based on the VSG active power control loop, calculate the integral feedback compensation value based on power deviation control;

[0079] According to the above formula (7), after obtaining the grid frequency reference value and the coefficients based on power deviation integral feedback compensation, the integral feedback compensation value based on power deviation control can be calculated by substituting the grid frequency reference value and the coefficients based on power deviation integral feedback compensation into formula (7). .

[0080] Step S103: Based on the integral feedback compensation value, extend the limit fault clearing time.

[0081] In the calculation Then, the virtual work angle can be calculated. At this point, the output current of the inverter under steady-state conditions is collected. Voltage at grid connection point PCC Calculate the actual output value of the inverter's reactive power based on the inverter's output current; calculate the VSG voltage command value based on the actual output value of the inverter's reactive power.

[0082] Based on the VSG voltage command value and virtual power angle, calculate the three-phase instantaneous voltage reference value output by the VSG. ;

[0083] Based on the three-phase instantaneous voltage reference value, the inverter output current and the grid connection point PCC voltage, the voltage modulation signal of the VSG system is calculated, and then the voltage modulation signal is transformed to generate a PWM modulation wave.

[0084] The drive signal is generated by using PWM modulation to control the switching transistor ( S 1- S 6) Switch on / off to extend the time for clearing extreme faults.

[0085] It should be noted that the formula used to calculate the modulated signal in this step is a commonly used formula in this field, so it will not be listed and explained one by one here.

[0086] Simplifying formula (7) yields:

[0087] (8)

[0088] By performing a Laplace transform and polynomial long division on equation (8), we can obtain:

[0089] (9)

[0090] in: , .

[0091] The last term in equation (9) is the remainder term in the polynomial long division simplification process. This remainder term is the additional response introduced by the power deviation integral. To reveal the time-domain characteristics of this control structure, the remainder term is converted into a time-domain expression through the inverse Laplace transform, resulting in:

[0092] (10)

[0093] In equation (10), For the Laplace transform of the work angle, The unit step function indicates that the response takes effect from t=0.

[0094] As can be seen from the analysis of equation (10), the remainder can accumulate the deviation of the power angle change during the VSG fault, and the power angle can be compensated by feedback based on the accumulated deviation, so as to achieve the effect of power angle return during the fault.

[0095] Substituting equation (10) into the equation, we get:

[0096] (11)

[0097] Comparing equation (1) and equation (11), the equivalent moment of inertia after power deviation integral feedback compensation can be obtained. Equivalent damping coefficient and equivalent active power reference value as follows:

[0098] (12)

[0099] (13)

[0100] (14)

[0101] Analysis of equations (12), (13), and (14) shows that the power deviation integral feedback compensation control can effectively adjust the moment of inertia. and damping coefficient Simultaneously, based on the combined effect of power angle and dynamic residual term, the equivalent active power reference value is dynamically adjusted. This further compensates for the active power imbalance during the fault period.

[0102] The transient stability after incorporating the above-mentioned active power deviation integral compensation control is theoretically analyzed as follows:

[0103] like Figure 8As shown in the figure, curves I and II represent the output power angle curves under normal operating conditions and when the grid voltage drops significantly (k=0.3), respectively. When the voltage on the distribution network side drops, it can be analyzed from equation (11) that, due to the influence of power deviation integral feedback compensation control, the active power reference value can be adjusted equivalently. Moment of inertia and damping coefficient This changes the size of the VSG transient acceleration / deceleration area.

[0104] Figure 8 middle, , and These correspond to the fault time, fault clearance point, and maximum power angle operation point, respectively. and For the first and second part deceleration areas, and and The acceleration area is for the first and second parts.

[0105] from Figure 5 Analysis shows that when the grid voltage drops, the VSG operating point abruptly changes from point A to point B. As the fault continues to occur, the operating point will move along curve II. Under the influence of the dynamic characteristics of the residual term of the power deviation integral feedback control, the rate of increase of the VSG power angle gradually slows down. When the power angle reaches its maximum value, its rate of change changes from positive to negative, at which point the power angle value is... This corresponds to point C on the power angle curve. Subsequently, the VSG output power angle value will decrease. During fault clearing, the power angle value at this point is... At point D on the corresponding power angle curve, the VSG operating point jumps from point D to point E.

[0106] Further analysis of the transient process reveals that after adding power deviation integral feedback compensation control during the fault period, the active power command value of the VSG decreases, and the acceleration area is significantly reduced. As the power angle continues to increase, the power deviation integral feedback control causes the active power command value to continue to decrease, forming a power balance point with the VSG output power, and the VSG deceleration area... It continues to increase. Once the power angle reaches its maximum value, the active power command value... The combined effect of the power angle and other terms results in a backoff effect, which remains less than the VSG's output power during the fault. This backoff process significantly reduces the power angle value at the moment of fault clearing, thereby further expanding the VSG's deceleration area. This effectively improves the transient stability margin of the VSG and extends the fault clearance time.

[0107] Figure 9 The diagram shows the phase plane of the VSG when it is disconnected after 1 second of fault duration. The steady-state power angle of the VSG before the fault. The figure shows the VSG power angle during fault clearance. As can be seen from the figure, the traditional VSG completely destabilizes during the fault process; the power deviation integral feedback compensation control, which does not consider the residual term, also destabilizes during the transient process; while the power deviation integral feedback compensation control, which considers the residual term, can improve the transient power angle stability performance under fault conditions. This is because the rotational inertia is effectively increased during the fault period. and damping coefficient At the same time, the active power reference value is effectively reduced by combining the work angle and the remainder term. Furthermore, the acceleration and deceleration area of ​​the VSG system was adjusted, and the rate of change of the power angle during faults was suppressed, thereby improving the transient power angle stability. Ultimately, it can be seen that the remainder has a certain positive impact on the transient power angle stability of the VSG.

[0108] Analysis of the power angle curve and phase plane diagram of VSG under grid voltage dips shows that the power angle regulation control of VSG introduced in this application based on active power deviation integral feedback compensation in the active power loop can change the acceleration and deceleration area of ​​the system by equivalent dynamic adjustment of the reference active power value, increasing the damping coefficient and rotational inertia. This effectively suppresses the rate of change of power angle of VSG during faults, prolongs the fault limit clearing time, and enhances the transient stability performance of VSG under different voltage dip conditions.

[0109] In some embodiments, this application also provides a computer device including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps in the above-described method embodiments.

[0110] This application also provides a computer-readable storage medium for storing a computer program. This computer-readable storage medium can be applied to a computer device, and the computer program causes the computer device to execute the corresponding processes in the methods described above in the embodiments of this application; for brevity, further details are omitted here.

[0111] Simulation verification

[0112] To verify the practical effectiveness of the proposed control strategy and ensure the accuracy of the theoretical analysis, Matlab / Simulink was used to perform... Figure 1 A simulation model of a grid-connected inverter based on VSG control was constructed. The system and control parameters are detailed in Table 1. Initially, the grid-connected inverter is in a stable operating state. At time 1 second, a voltage dip fault occurs in the grid, lasting for 1 second. The following simulations compare the traditional VSG control and the VSG inverter with the proposed control strategy under two operating conditions: voltage dips to 0.5 pu and 0.3 pu.

[0113] ;

[0114] Figure 10 A comparison of transient waveforms for different VSG control strategies when the grid voltage drops to 0.5 pu. Figure 10 (a) is a waveform diagram under traditional VSG control. It can be seen from the figure that the traditional VSG experiences transient instability during the fault process. Figure 10 (b) shows the waveform of the VSG under power deviation integral feedback compensation control. It can be observed that the VSG using power deviation integral feedback compensation control can suppress the rate of change of the VSG's power angle during a fault by effectively dynamically adjusting the reference active power value, increasing the damping coefficient and moment of inertia, and changing the acceleration / deceleration area of ​​the VSG, thus effectively improving the transient stability of the VSG. Finally, simulation results show that the proposed power deviation integral feedback compensation control strategy can effectively improve transient power angle stability.

[0115] Figure 11 A comparison of transient waveforms for different VSG control strategies when the grid voltage drops to 0.3 pu. Figure 11 (a) is a waveform diagram under traditional VSG control. It can be seen from the figure that the traditional VSG experiences transient instability during the fault process. Figure 11 (b) shows the waveform of the VSG under power deviation integral feedback compensation control. It can be observed that the VSG using power deviation integral feedback compensation control can suppress the rate of change of the VSG's power angle during a fault by effectively dynamically adjusting the reference active power value, increasing the damping coefficient and moment of inertia, and changing the acceleration / deceleration area of ​​the VSG, thus effectively improving the transient stability of the VSG. Finally, simulation results show that the proposed power deviation integral feedback compensation control strategy can effectively improve transient power angle stability.

[0116] To further demonstrate the effectiveness of the proposed control strategy during fault conditions, a comparison is made between the existing flexible control strategy using rotational inertia and damping coefficient parameters and the VSG output power angle and various electrical quantities under power deviation integral feedback compensation control. Figure 12 As shown.

[0117] Figure 12 (a) By adopting a flexible control strategy based on rotational inertia and damping coefficient parameters, although it is possible to increase the fault limit clearing time while increasing the limit clearing angle and optimizing the transient stability performance of VSG, the fault limit clearing time is only increased to 0.22s. Figure 12 (b) is the active power deviation integral feedback control strategy proposed in this paper. This control strategy can effectively suppress the rate of change of power angle during the fault and extend the limit fault clearing time to 1s, which significantly improves the transient stability performance of VSG.

[0118] In summary, the strategy proposed in this application can effectively suppress the rate of change of the VSG power angle during the fault process, prolong the ultimate fault clearing time, and improve the transient power angle stability.

[0119] The above embodiments are preferred implementations of this application. In addition, this application can be implemented in other ways. Any obvious substitutions without departing from the concept of this technical solution are within the protection scope of this application.

[0120] To facilitate understanding by those skilled in the art of the improvements made by this application compared to the prior art, some of the accompanying drawings and descriptions have been simplified, and for clarity, some other elements have been omitted from this application. Those skilled in the art should realize that these omitted elements may also constitute the content of this application.

Claims

1. A strategy for enhancing the transient support capability of VSG based on active power deviation integral feedback, characterized in that, include: Construct a VSG active power control loop based on active power deviation integral feedback; Based on the VSG active power control loop, calculate the integral feedback compensation value based on power deviation control; Based on the integral feedback compensation value, the critical fault clearing time is extended; The calculation of the integral feedback compensation value based on power deviation control based on the VSG active power control loop includes: Obtain the grid frequency reference value and the coefficients based on power deviation integral feedback compensation; Based on the power grid frequency reference value and the coefficients of the power deviation integral feedback compensation, calculate the integral feedback compensation value based on power deviation control; The integral feedback compensation value based on power deviation control is calculated using the power grid frequency reference value and the coefficient based on power deviation integral feedback compensation. The calculation formula is as follows: ； In the formula, This is the integral feedback compensation value based on power deviation control. The coefficients are based on power deviation integral feedback compensation. For the Laplace operator, This is the reference value for the power grid frequency. This represents the actual value of the VSG virtual rotor angular velocity after power deviation integral feedback compensation. and These are the VSG's active power reference value and actual active power output value, respectively. This is a virtual moment of inertia; is the damping coefficient.

2. The strategy according to claim 1, characterized in that, The step of extending the critical fault clearing time based on the integral feedback compensation value includes: The virtual power angle is calculated based on the integral feedback compensation value; Collect the inverter's output current and the grid connection point PCC voltage under transient conditions; Calculate the voltage modulation signal of the VSG system based on the virtual power angle, the inverter output current and the grid connection point PCC voltage. Based on the voltage modulation signal of the VSG system, the critical fault clearing time is extended.

3. The strategy according to claim 2, characterized in that, Based on the virtual power angle, inverter output current, and grid connection point PCC voltage, the voltage modulation signal of the VSG system is calculated, including: Calculate the actual output value of the inverter's reactive power based on the inverter's output current; Calculate the VSG voltage command value based on the actual reactive power output value of the inverter. Based on the VSG voltage command value and virtual power angle, calculate the reference value of the three-phase instantaneous voltage output by the VSG; The voltage modulation signal of the VSG system is calculated based on the three-phase instantaneous voltage reference value, the inverter output current and the grid connection point PCC voltage.

4. The strategy according to claim 3, characterized in that, The voltage modulation signal based on the VSG system extends the critical fault clearing time, including: The voltage modulation signal of the VSG system is transformed to generate a PWM modulation wave; By using PWM modulation waves to generate drive signals, the switching transistors are controlled to turn on and off, thus extending the time for clearing extreme faults.

5. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the VSG transient support capability enhancement strategy based on active power deviation integral feedback as described in any one of claims 1 to 4.

6. A computer storage medium storing computer program code, characterized in that, When the computer program code is executed by the processor, it implements the VSG transient support capability enhancement strategy based on active power deviation integral feedback as described in any one of claims 1-4.

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