Rectification side transient overvoltage quantitative calculation method for alternating current fault

Abstract

The invention belongs to the technical field of transient overvoltage suppression, and particularly discloses a rectification side transient overvoltage quantitative calculation method for an AC fault, and the method comprises the following steps: carrying out the steady-state analysis of a new energy access system, and obtaining a factor which affects the transient overvoltage when the AC fault occurs; analyzing the dynamic response process of the receiving end system and the sending end system containing the new energy access system when the AC fault occurs, and obtaining the generation reason of the transient overvoltage; according to the factors influencing the transient overvoltage and the generation reason of the transient overvoltage, analyzing to obtain a response relationship among the factors influencing the transient overvoltage; and establishing a transient overvoltage quantitative model according to the response relationship among the factors influencing the transient overvoltage, and completing the quantitative calculation of the transient overvoltage at the rectification side. According to the method, the problems of calculation deviation caused by simplified hypothesis and system dynamic characteristic change caused by new energy access in the prior art are solved.

Description

Technical Field

[0001] This invention belongs to the field of transient overvoltage suppression technology, specifically relating to a quantitative calculation method for transient overvoltage on the rectifier side during AC faults. Background Technology

[0002] With the rapid development of renewable energy, grid connection of new energy sources such as wind and solar power has become an important trend in the modernization of power systems. Direct current transmission (HVDC), as an efficient and reliable power transmission method, is particularly suitable for long-distance, large-capacity power transmission. To better accommodate large-scale renewable energy, the application of HVDC systems is gradually expanding towards new energy integration.

[0003] However, in DC transmission systems, severe transient overvoltages can occur on the rectifier side during AC faults, especially short-circuit faults. This can damage power equipment and affect system stability and reliability. Due to the complexity and dynamic characteristics of renewable energy grid-connected systems, traditional overvoltage suppression methods are no longer sufficient to meet the requirements for rapid response and precise control during AC faults.

[0004] Currently, the quantitative calculation of transient overvoltages on the rectifier side during AC faults remains one of the challenges in power system research, especially in DC transmission systems with renewable energy integration. Therefore, developing an effective overvoltage quantification method capable of real-time and accurate assessment of the magnitude, duration, and impact on system safety of transient overvoltages on the rectifier side is of significant theoretical and practical value for ensuring the stable operation of power systems and improving the reliability of renewable energy grid connection.

[0005] The existing technology mainly has the following problems: 1. Lack of sufficient consideration of the dynamic response of the receiving and sending systems. Traditional transient overvoltage calculation methods are mostly based on simplifying assumptions, neglecting the specific dynamic responses of the receiving and sending power systems. In real-world applications, overvoltages in DC transmission systems are not determined by a single factor, but are influenced by multiple system components and their interactions. However, existing methods often simplify these factors, resulting in calculation results that do not fully reflect the complexity and actual dynamic behavior of the system, thus affecting the accuracy and reliability of overvoltage predictions.

[0006] 2. The impact of renewable energy integration on overvoltage characteristics is not considered. With the large-scale integration of renewable energy sources, especially intermittent energy sources such as wind and solar power, the operating characteristics and overvoltage behavior of DC transmission systems have changed significantly. The dynamic response and volatility of renewable energy sources, especially during grid faults, directly affect the transient overvoltage level on the rectifier side. For example, wind and solar power plants may experience sharp power fluctuations or even disconnection from the grid during AC faults, which can significantly impact voltage fluctuations on the rectifier side. Existing calculation methods often neglect the quantification of these complex factors and cannot accurately reflect the voltage response behavior of renewable energy systems under fault conditions, leading to significant deviations in calculation results after renewable energy integration. Summary of the Invention

[0007] The purpose of this invention is to solve the problems of calculation deviation caused by simplification assumptions in the prior art and the changes in system dynamic characteristics caused by the access of new energy sources. It proposes a quantitative calculation method for transient overvoltage on the rectifier side during AC faults.

[0008] The technical solution of this invention is: a method for quantifying and calculating transient overvoltage on the rectifier side during AC faults, comprising the following steps: S1. Perform steady-state analysis on the system with new energy access to obtain the factors that affect transient overvoltage when AC faults occur; S2. Analyze the dynamic response process of the receiving-end system and sending-end system containing the new energy access system during AC faults to obtain the cause of transient overvoltage; S3. Based on the factors that affect transient overvoltage and the causes of transient overvoltage, analyze the response relationships between the factors that affect transient overvoltage; S4. Based on the response relationship between the various factors that affect transient overvoltage, establish a transient overvoltage quantification model and complete the quantification calculation of transient overvoltage on the rectifier side.

[0009] Preferably, in step S1, the formula for calculating the transient voltage change of the rectifier-side converter station bus when an AC fault occurs is:

[0010] in, This represents the instantaneous change in the voltage at the sending end bus, that is, the instantaneous change in the voltage at the converter station bus on the rectifier side. This represents the sum of reactive power changes during a fault. Indicates the short-circuit capacity of the sending-end system. This represents the reactive power of the synchronous generator branch flowing into the AC bus of the converter station. This indicates the reactive power of the branch line from the new energy station merging into the AC bus of the converter station. This indicates the reactive power output of the reactive power compensation equipment in the rectifier-side converter station. This represents the reactive power absorbed by the rectifiers in the converter station on the rectifier side; the instantaneous change in the voltage of the sending-end bus. The sum of reactive power changes during a fault It is positively correlated with the short-circuit capacity of the sending-end system. It is negatively correlated, that is , , , and All of these will affect transient overvoltage.

[0011] Preferably, the reactive power output of the reactive power compensation equipment in the rectifier-side converter station is [specified]. The formula for expressing this is:

[0012] in, This represents the effective value of the phase voltage of the AC bus in the converter station. This indicates reactive power compensation reactance.

[0013] Preferably, the rectifier absorbs reactive power. The formula for expressing this is:

[0014] in, This represents the DC current on the rectifier side. This represents the ideal no-load DC voltage. This indicates the active power output of the rectifier.

[0015] Preferably, in step S2, the dynamic response process of the receiving-end system and the sending-end system containing the new energy access system when an AC fault occurs is divided into three stages: stage 1, stage 2, and stage 3. Stage 1 is the fault occurrence stage; stage 2 is the inverter-side commutation failure and recovery stage; and stage 3 is the commutation failure disappearance and DC current recovery stage.

[0016] Preferably, in step S2, when an AC fault occurs, the change in reactive power exchanged by the new energy station when the system fault occurs leads to transient overvoltage.

[0017] Preferably, the change in reactive power exchanged by the new energy station when a system fault occurs includes the change in reactive power output by the reactive power compensation equipment of the rectifier-side converter station and the change in reactive power absorbed by the rectifier of the rectifier-side converter station.

[0018] Preferably, in the event of a fault, the change in reactive power output by the reactive power compensation equipment of the rectifier-side converter station is as follows:

[0019] in, This represents the change in reactive power output from the reactive power compensation equipment in the rectifier-side converter station. This indicates the transient overvoltage value of the rectifier-side AC bus after an AC fault occurs. This represents the effective value of the phase voltage of the AC bus on the rectifier side. This represents the reactive power compensation reactance. The larger the reactive power compensation reactance, the more sensitive the rectifier side is to changes in the reactive power output of the reactive power compensation equipment in the rectifier-side converter station, and the more severe the transient overvoltage becomes.

[0020] Preferably, the change in reactive power absorbed by the rectifier is obtained by differentiating and analyzing the rectifier firing angle, as shown in the following formula:

[0021] in, This represents the change in reactive power absorbed by the rectifier. Indicates the rectifier reactance. This represents the DC current of the rectifier. This represents the ideal no-load DC voltage. This indicates the rectifier's output active power. Represents pi (π). Indicates the rectifier firing angle. Represents the sine function. Represent the cosine function; it has a derivative. Greater than 0, when At that time, the reactive power absorbed by the rectifier is related to the rectifier firing angle. There is a positive correlation, meaning the reactive power absorbed by the rectifier is related to the rectifier firing angle. The relationship between them is monotonically increasing.

[0022] Preferably, the formula for the quantization model is:

[0023] in, Indicates transient overvoltage. This indicates the change in reactive power exchanged by the renewable energy station when a system failure occurs. , Indicates the rectifier firing angle. Indicates reactive power compensation reactance. Indicates transient overvoltage and , and The functional relationship between them.

[0024] The beneficial effects of this invention are: 1. Improved prediction accuracy: By comprehensively considering factors such as reactive power changes, firing angle, and reactance, the model established in this invention significantly improves the accuracy of transient overvoltage prediction and can more accurately reflect voltage fluctuations during AC faults.

[0025] 2. Optimized voltage control strategy: This invention provides a quantitative analysis based on reactive power and firing angle changes, offering a more accurate voltage control strategy for power systems and effectively reducing the impact of transient overvoltages on the system.

[0026] 3. Enhanced system stability: By adjusting the reactive power compensation equipment and rectifier firing angle in real time, this invention enhances the system's stability during faults, enabling rapid restoration of normal system operation and avoiding equipment damage caused by overvoltage. Attached Figure Description

[0027] Figure 1 The diagram shown is a flowchart of a method for quantifying and calculating transient overvoltage on the rectifier side during AC faults, provided in an embodiment of the present invention.

[0028] Figure 2 The diagram shown is an equivalent circuit diagram of the DC transmission system's sending-end system provided in an embodiment of the present invention.

[0029] Figure 3 The diagram shown is a phased schematic diagram of an AC fault occurring on the rectifier side, provided in an embodiment of the present invention. Detailed Implementation

[0030] Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be understood that the embodiments shown and described in the drawings are merely exemplary and are intended to illustrate the principles and spirit of the invention, and are not intended to limit the scope of the invention.

[0031] Example: like Figure 1 As shown, a method for quantifying and calculating transient overvoltages on the rectifier side during AC faults includes the following steps: S1. Perform steady-state analysis on the system with new energy access to obtain the factors that affect transient overvoltage when AC faults occur; S2. Analyze the dynamic response process of the receiving-end system and sending-end system containing the new energy access system during AC faults to obtain the cause of transient overvoltage; S3. Based on the factors that affect transient overvoltage and the causes of transient overvoltage, analyze the response relationships between the factors that affect transient overvoltage; S4. Based on the response relationship between the various factors that affect transient overvoltage, establish a transient overvoltage quantification model and complete the quantification calculation of transient overvoltage on the rectifier side.

[0032] In this embodiment, the equivalent circuit of the sending-end system of the high-voltage direct current transmission system is as follows: Figure 2 As shown, where, This represents the effective value of the phase voltage of the new energy station. This indicates the reactance of the high-voltage AC tie line between the new energy station and the converter station bus. This represents the effective value of the phase voltage of the AC bus in the converter station. This represents the effective value of the phase voltage of the equivalent synchronous generator. This represents the AC interconnection reactance between the equivalent synchronous generator and the converter station bus. The equivalent susceptance of the reactive power compensation device is represented by: Under the steady-state operating conditions of a high-voltage direct current transmission system, the balance between active and reactive power is expressed as:

[0033]

[0034] in, and These represent the active power of the synchronous generator branch and the new energy station branch that converge into the AC bus of the converter station, respectively. This represents the active power transmitted by the converter station. and These represent the reactive power of the synchronous generator branch and the new energy station branch flowing into the AC bus of the converter station, respectively. This indicates the compensation capacity of the reactive power compensation device. This indicates the reactive power consumed by the converter station.

[0035] By analyzing the voltage characteristics of the AC bus and combining the basic equations of power balance and voltage balance:

[0036]

[0037] in, This represents the active power output of new energy sources. The reactive power output of the new energy source can be represented by the following formula:

[0038] Therefore, the expression for the extreme voltage of the new energy station can be derived as follows:

[0039] Analyzing the side-mounted AC system, based on the AC bus voltage, using the voltage transfer equation:

[0040]

[0041] in, This represents the change in the effective value of the longitudinal component of the phase voltage at the AC bus of the converter station. This represents the transverse component of the phase voltage at the AC bus of the converter station. Indicates line impedance; Solve for the effective value of the phase voltage of the equivalent synchronous generator:

[0042] When an AC fault occurs, the formula for calculating the transient voltage change of the rectifier-side converter station bus is:

[0043] in, This represents the instantaneous change in the voltage at the sending end bus, that is, the instantaneous change in the voltage at the converter station bus on the rectifier side. This represents the sum of reactive power changes during a fault. Indicates the short-circuit capacity of the sending-end system. This represents the reactive power of the synchronous generator branch flowing into the AC bus of the converter station. This indicates the reactive power of the branch line from the new energy station merging into the AC bus of the converter station. This indicates the reactive power output of the reactive power compensation equipment in the rectifier-side converter station. This represents the reactive power absorbed by the rectifiers in the converter station on the rectifier side; the instantaneous change in the voltage of the sending-end bus. The sum of reactive power changes during a fault It is positively correlated with the short-circuit capacity of the sending-end system. It is negatively correlated, that is , , , and All of these will affect transient overvoltage.

[0044] When an AC fault occurs, the dynamic responses of the receiving and sending systems are intertwined, and their impact on transient overvoltages is quite complex. The receiving system is typically affected by voltage fluctuations caused by the fault, leading to sharp changes in current and voltage. Simultaneously, the sending system also experiences voltage fluctuations due to the fault, thus affecting the power transmitted to the DC side through the converter station.

[0045] In this embodiment, based on the inverter control state, the entire overvoltage process is divided into stage 0, stage 1, stage 2, and stage 3, as follows: Figure 3 As shown.

[0046] Phase 0: Pre-fault steady state. During normal operation, the rectifier side uses constant current control (CC), while the inverter side adjusts the firing angle through constant turn-off angle control (CEA). At this time, the command value βcea of ​​CEA is greater than the command value βcc of CC.

[0047] Phase 1: Fault Occurrence Phase When a severe fault occurs on the rectifier side, the AC bus voltage Uac1 drops rapidly, and the DC current Idi decreases. To maintain the DC current, the firing angle on the rectifier side decreases to its minimum value. The system enters minimum firing angle control mode. Due to the severity of the fault, the DC current continues to decrease, leading to commutation failure. The inverter-side turn-off angle control fails, and the system switches to constant current control (CC). At this time, the inverter-side... Decrease The current increases, but the system remains in CC control mode. Because both sides are under constant current control, the turn-off angle decreases uncontrollably, leading to commutation failure.

[0048] Phase 2: Inverter-side commutation failure and recovery phase Due to a fault, the inverter-side firing angle was significantly lower than normal operating conditions, resulting in a large turn-off angle during recovery from commutation failure. The CEA controller quickly adjusted the firing angle to restore it to its rated value. The presence of the CF (Cyclic Crosstalk) caused a bypass pair to form in the inverter during commutation, leading to a rapid increase in DC current. At this point, the inverter switched back to CEA control, but the lack of effective current control caused the DC current to rise further, resulting in a sharp increase in the rectifier firing angle.

[0049] Phase 3: Commutation failure disappears, DC current recovers. After the CF (Cyclic Flow Control) is cleared, the firing angle on the rectifier side gradually decreases, the DC current recovers to the pre-fault level, and the reactive power of the rectifier also gradually recovers to the pre-fault level. As the reactive power of the system gradually balances, the converter bus voltage recovers to its rated value. After the fault is cleared, the AC bus voltage Uac1 recovers, the DC current Idi increases, and the rectifier side returns to constant current control (CC). In the later stage of fault recovery, the inverter side switches to trigger current deviation control (CEC), at which point the current fluctuates between the commanded value and the actual value, gradually rising to a stable state.

[0050] During the fault duration (Phase 1), the rectifier enters the minimum firing angle control mode. The fault causes a rapid drop in the AC bus voltage at the DC sending end, resulting in a rapid decrease in DC power and current. As the fault is cleared, the DC current recovers, the rectifier firing angle increases, and reactive power increases. During the recovery process, the DC current gradually stabilizes, and the firing angle and reactive power gradually return to normal.

[0051] Due to inverter commutation failure (stage 2), a short circuit on the DC side triggers an inrush current, causing a sharp increase in DC current and consequently a sharp increase in the rectifier firing angle. Since the rectifier's reactive power is positively correlated with the firing angle, the increase in both current and firing angle leads to a rapid increase in the rectifier's reactive power, resulting in a drop in bus voltage.

[0052] After the commutation failure disappears, the DC current decreases rapidly under the control of the rectifier and inverter, and the rectifier firing angle decreases (stages 2 and 3). At this time, the reactive power of the rectifier decreases, and due to the excessive reactive power output by the reactive power compensation device, reactive power redundancy occurs on the rectifier AC bus. As a result, the reduced reactive power consumed by the rectifier leads to the converter station outputting reactive power to the sending-end AC system, causing the sending-end AC bus voltage to rise and resulting in overvoltage. That is, when an AC fault occurs, the change in reactive power exchanged by the new energy station during a system fault can lead to transient overvoltage.

[0053] In this embodiment, the change in reactive power exchanged by the renewable energy station when a system fault occurs directly affects the amplitude of voltage fluctuations. Especially during AC faults, the drastic change in reactive power exchanged by the renewable energy station can lead to significant voltage fluctuations. At this time, the voltage change mainly depends on two factors: first, the reactive power output by the reactive power compensation equipment of the rectifier-side converter station; and second, the reactive power absorbed by the rectifier.

[0054] The reactive power output of the rectifier station's reactive power compensation equipment can be expressed as:

[0055] in, This represents the effective value of the phase voltage of the AC bus in the converter station. This indicates reactive power compensation reactance.

[0056] When a fault occurs, the change in reactive power output of the reactive power compensation equipment in the rectifier-side converter station is as follows:

[0057] in, This represents the change in reactive power output from the reactive power compensation equipment in the rectifier-side converter station. This indicates the transient overvoltage value of the rectifier-side AC bus after an AC fault occurs.

[0058] The reactance of a reactive power compensation device has a significant impact on transient voltage fluctuations. Reactive power compensation reactance. The larger the reactance, the more sensitive the rectifier side is to changes in the reactive power output of the reactive power compensation equipment in the rectifier-side converter station, and the more severe the voltage fluctuations will be. Due to the interaction between reactance and voltage changes, when the voltage rises, the demand for reactive power compensation will increase, leading to a further increase in reactive power and thus exacerbating transient overvoltages.

[0059] When an AC fault occurs, the change in reactive power exchanged by the renewable energy station during the system fault. This can cause transient voltage fluctuations; therefore, changes in reactive power directly affect instantaneous voltage changes. Furthermore, changes in reactive power are closely related to the operation and control methods of the rectifier.

[0060] For a 12-pulse rectifier, the quasi-steady-state equation for the DC-side voltage is expressed as:

[0061] in, Indicates the DC voltage on the rectifier side. Indicates the rectifier reactance. This represents the DC current of the rectifier. This represents the ideal no-load DC voltage. Represents pi (π). Indicates the rectifier firing angle. This represents the cosine function.

[0062] Rectifier output active power for:

[0063] Reactive power absorbed by the rectifier for:

[0064] Therefore, the rectifier output active power is derived as follows:

[0065] Then, the DC current of the rectifier for:

[0066] Based on the expression for the reactive power absorbed by the rectifier, and Taking the derivative, we get:

[0067] Based on the DC current of the rectifier and to and The derivative obtained, representing the change in reactive power absorbed by the rectifier, is derived by differentiating and analyzing the rectifier firing angle. The specific formula is as follows:

[0068] in, This represents the change in reactive power absorbed by the rectifier. Indicates the rectifier reactance. This represents the DC current of the rectifier. This represents the ideal no-load DC voltage. This indicates the rectifier's output active power. Represents pi (π). Indicates the rectifier firing angle. Represents the sine function. Represent the cosine function; it has a derivative. Greater than 0, when At that time, the reactive power consumed by the rectifier is related to the rectifier firing angle. There is a positive correlation, that is, reactive power and rectifier firing angle. The relationship between them is monotonically increasing. The change in reactive power absorbed by the rectifier is illustrated using a typical system and control parameters. P dr =8000MW, U dR0 =810kV, I dR =10kA, X R =0.1, α R =4°, the change in reactive power absorbed by a rectifier in a real DC line is calculated as follows: ∆Q =3582 MVar In practical applications, calculations should be performed based on the specific DC transmission parameters.

[0069] Based on the relationship between voltage fluctuations and reactive power changes, a quantitative model is established to represent reactive power changes (specifically referring to the reactive power exchanged by renewable energy stations when system faults occur) and rectifier firing angles. and reactive power compensation reactance Transient overvoltage The comprehensive impact; the formula for the quantification model is:

[0070] in, Indicates transient overvoltage. This indicates the change in reactive power exchanged by the renewable energy station when a system failure occurs. , Indicates the rectifier firing angle. Indicates reactive power compensation reactance. Indicates transient overvoltage and , and The functional relationship between them.

[0071] In the transient overvoltage analysis of renewable energy grid-connected DC transmission systems, the change in reactive power exchanged by renewable energy stations when a system fault occurs is considered. rectifier firing angle and reactive power compensation reactance These parameters constitute the core parameters of the system's dynamic response. Reactive power variation reflects the dynamic energy exchange characteristics of the renewable energy station during system faults, directly determining the system's transient energy balance and voltage fluctuation amplitude. The rectifier firing angle, as a key parameter for system control, significantly affects the system's transient response process by adjusting the energy conversion channel and reactive power consumption rate. Meanwhile, the compensation reactance plays a crucial role in suppressing and mitigating transient overvoltages by adjusting the system's equivalent impedance and reactive power exchange capacity. These three parameters, through a complex nonlinear coupling mechanism, jointly determine the system's voltage dynamic characteristics and stability under fault conditions.

[0072] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in this invention without departing from the spirit of the invention, and these modifications and combinations are still within the scope of protection of this invention.

Claims

1. A method for quantifying and calculating transient overvoltages on the rectifier side during AC faults, characterized in that, Includes the following steps: S1. Perform steady-state analysis on the system with new energy access to obtain the factors that affect transient overvoltage when AC faults occur; S2. Analyze the dynamic response process of the receiving-end system and sending-end system containing the new energy access system during AC faults to obtain the cause of transient overvoltage; S3. Based on the factors that affect transient overvoltage and the causes of transient overvoltage, analyze the response relationships between the factors that affect transient overvoltage; S4. Based on the response relationship between the various factors affecting transient overvoltage, establish a transient overvoltage quantification model and complete the quantification calculation of transient overvoltage on the rectifier side.

2. The method for quantifying and calculating transient overvoltage on the rectifier side during AC faults according to claim 1, characterized in that, In step S1, the formula for calculating the transient voltage change of the rectifier-side converter station bus when an AC fault occurs is as follows: in, This represents the instantaneous change in the voltage at the sending end bus, that is, the instantaneous change in the voltage at the converter station bus on the rectifier side. This represents the sum of reactive power changes during a fault. Indicates the short-circuit capacity of the sending-end system. This represents the reactive power of the synchronous generator branch flowing into the AC bus of the converter station. This indicates the reactive power of the branch line from the new energy station merging into the AC bus of the converter station. This indicates the reactive power output of the reactive power compensation equipment in the rectifier-side converter station. This represents the reactive power absorbed by the rectifiers in the converter station on the rectifier side; the instantaneous change in the voltage of the sending-end bus. The sum of reactive power changes during a fault It is positively correlated with the short-circuit capacity of the sending-end system. It is negatively correlated, that is , , , and All of these will affect transient overvoltage.

3. The method for quantifying and calculating transient overvoltage on the rectifier side during AC faults according to claim 2, characterized in that, The reactive power output of the reactive power compensation equipment in the rectifier-side converter station The formula for expressing this is: in, This represents the effective value of the phase voltage of the AC bus in the converter station. This indicates reactive power compensation reactance.

4. The method for quantifying and calculating transient overvoltage on the rectifier side during AC faults according to claim 2, characterized in that, The reactive power absorbed by the rectifier The formula for expressing this is: in, This represents the DC current of the rectifier-side converter station. This represents the ideal no-load DC voltage. This indicates the active power output of the rectifier.

5. The method for quantifying and calculating transient overvoltage on the rectifier side during AC faults according to claim 1, characterized in that, In step S2, when an AC fault occurs, the dynamic response process of the receiving-end system and the sending-end system containing the new energy access system is divided into three stages: stage 1, stage 2, and stage 3. Stage 1 is the fault occurrence stage; stage 2 is the inverter-side commutation failure and recovery stage; and stage 3 is the commutation failure disappearance and DC current recovery stage.

6. The method for quantifying and calculating transient overvoltage on the rectifier side during AC faults according to claim 1, characterized in that, In step S2, when an AC fault occurs, the change in reactive power exchanged by the new energy station when the system fault occurs leads to transient overvoltage.

7. The method for quantifying and calculating transient overvoltage on the rectifier side during AC faults according to claim 6, characterized in that, The change in reactive power exchanged by the new energy station when a system fault occurs includes the change in reactive power output by the reactive power compensation equipment of the rectifier-side converter station and the change in reactive power absorbed by the rectifier of the rectifier-side converter station.

8. The method for quantifying and calculating transient overvoltage on the rectifier side during AC faults according to claim 7, characterized in that, When a fault occurs, the change in reactive power output of the reactive power compensation equipment in the rectifier-side converter station is as follows: in, This represents the change in reactive power output from the reactive power compensation equipment in the rectifier-side converter station. This indicates the transient overvoltage value of the rectifier-side AC bus after an AC fault occurs. This represents the effective value of the phase voltage of the AC bus on the rectifier side. This represents the reactive power compensation reactance. The larger the reactive power compensation reactance, the more sensitive the rectifier side is to changes in the reactive power output of the reactive power compensation equipment in the rectifier-side converter station, and the more severe the transient overvoltage becomes.

9. The method for quantifying and calculating transient overvoltage on the rectifier side during AC faults according to claim 8, characterized in that, The change in reactive power absorbed by the rectifier is obtained by differentiating and analyzing the rectifier firing angle, and the specific formula is as follows: in, This represents the change in reactive power absorbed by the rectifier. Indicates the rectifier reactance. This represents the DC current of the rectifier. This represents the ideal no-load DC voltage. This indicates the rectifier's output active power. Represents pi (π). Indicates the rectifier firing angle. Represents the sine function. Represents the cosine function; it has a derivative. Greater than 0, when At that time, the reactive power absorbed by the rectifier is related to the rectifier firing angle. There is a positive correlation, meaning the reactive power absorbed by the rectifier is related to the rectifier firing angle. The relationship between them is monotonically increasing.

10. The method for quantifying and calculating transient overvoltage on the rectifier side during AC faults according to claim 9, characterized in that, The formula for the quantization model is as follows: in, Indicates transient overvoltage. This indicates the change in reactive power exchanged by the renewable energy station when a system failure occurs. , Indicates the rectifier firing angle. Indicates reactive power compensation reactance. Indicates transient overvoltage and , and The functional relationship between them.

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