Overvoltage suppression method and device

Abstract

The invention is suitable for the technical field of power grid control, and provides an overvoltage suppression method and device, and the method comprises the steps: obtaining a target overvoltage of a fault at an AC bus of a voltage source type converter; obtaining a reactive power reference signal based on the target overvoltage; and suppressing the target overvoltage based on the actual output reactive power and the reactive power reference signal of the voltage source type converter. According to the invention, the overvoltage of the hybrid power flow controller at the AC bus of the voltage source type converter can be effectively suppressed, the suppression effect at the initial stage of suppression is enhanced, and the suppression response speed is improved.

Description

Technical Field

[0001] The present application belongs to the field of power grid control technology, and in particular, to an overvoltage suppression method and device. Background Art

[0002] As the proportion of renewable energy in the power grid increases, it gradually replaces traditional thermal power generation. Its inherent uncertainty and volatility bring challenges to the dynamic control of power flow in the power grid. This characteristic makes the imbalance problem of power flow distribution in the power grid more serious, which is manifested in excessive power flow loads in some transmission channels and nodes, excessive voltage in local areas, and overload problems in N-1 (that is, the system can still operate normally after any component fails). These problems coexist in the power grid, with both bottleneck constraints of transmission sections and underutilization of line transmission capacity, which has a serious impact on the overall power supply capacity of the power grid and the safety and stability of the system.

[0003] In order to solve the above problems, hybrid power flow controller has become a hot topic in the research field. This device combines a large-capacity dual-core symmetrical phase shifting transformer (PST) and a small-capacity voltage source converter (VSC) to form a new type of hybrid power flow controller (HPFC). This controller can achieve accurate and rapid control of power flow by making large-scale flexible and continuous adjustments to the amplitude and phase of the line impedance. However, the overvoltage characteristics of this new type of equipment combined with traditional electromagnetic equipment and power electronic equipment are more complex. The secondary side of the excitation transformer is combined with a voltage source converter to improve the converter's ability to withstand overvoltage, but the voltage source converter belongs to power electronic equipment. The converter module has limited voltage resistance, and the amplitude and time of overvoltage stress are small. When overvoltage occurs, it is easy to be damaged and exit operation. Therefore, it is particularly important to suppress the transient overvoltage of the AC bus of the voltage source converter from the control level of the hybrid power flow controller.

[0004] During normal operation, if the power flow of the line changes, the dual-core symmetrical phase-shifting transformer is used to discretely adjust and track the system power flow, and combined with the voltage source converter to achieve continuous and precise regulation. Among them, the voltage source converter control link uses a proportional-integral (PI) controller to adjust to compensate for the error. However, the PI controller is a control mechanism based on error feedback to eliminate errors. When overvoltage occurs, the voltage source converter still uses PI to adjust it, which may cause certain hysteresis and large fluctuations. This may not meet the performance requirements in situations where fast response and effective suppression of overvoltage are required. Summary of the invention

[0005] The embodiments of the present application provide an overvoltage suppression method and device to achieve effective suppression of overvoltage at the AC bus of a voltage source converter by a hybrid power flow controller, enhance the suppression effect in the initial stage of suppression, and improve the suppression response speed.

[0006] This application is implemented through the following technical solutions:

[0007] In a first aspect, an embodiment of the present application provides an overvoltage suppression method, comprising:

[0008] Obtain the target overvoltage at the AC bus of the voltage source converter when a fault occurs.

[0009] Based on the target overvoltage, a reactive power reference signal is obtained.

[0010] Based on the actual output reactive power of the voltage source converter and a reactive power reference signal, the target overvoltage is suppressed.

[0011] In combination with the first aspect, in some possible implementations, suppressing a target overvoltage based on an actual output reactive power of a voltage source converter and a reactive power reference signal includes:

[0012] The difference between the actual output reactive power of the voltage source converter and the reactive power reference signal is calculated and recorded as the first difference.

[0013] Based on the first difference, a bandwidth of the hybrid power flow controller is adjusted.

[0014] Based on the bandwidth of the hybrid power flow controller, the bandwidth of the linear extended state observer is set to suppress the target overvoltage.

[0015] In combination with the first aspect, in some possible implementations, adjusting the bandwidth of the voltage source converter based on the first difference includes:

[0016] When the first difference is greater than the first set value, the bandwidth is increased by the adaptive linear active disturbance suppression control hybrid power flow controller.

[0017] When the first difference is less than the first set value, the bandwidth is reduced by the adaptive linear active disturbance suppression control hybrid power flow controller.

[0018] In combination with the first aspect, in some possible implementations, when the first difference is greater than a first set value, increasing the bandwidth by using an adaptive linear active disturbance suppression control hybrid power flow controller includes:

[0019] When the first difference is greater than the first set value, the bandwidth is increased by controlling the hybrid power flow controller through an adaptive linear active disturbance suppression method in combination with the first formula.

[0020] The first formula is:

[0021] ω + =ω c0 +k(ln10(Q V -Q ref )+Q set )

[0022] Among them, ω + represents the increased bandwidth, ω c0 represents the initial bandwidth, k represents the adaptive adjustment coefficient, (Q V -Q ref ) represents the first difference, Q set Indicates the first setting value.

[0023] In combination with the first aspect, in some possible implementations, when the first difference is less than a first set value, reducing the bandwidth by using an adaptive linear active disturbance suppression control hybrid power flow controller includes:

[0024] When the first difference is less than the first set value, the bandwidth is reduced by controlling the hybrid power flow controller through an adaptive linear active disturbance suppression method in combination with the second formula.

[0025] The second formula is:

[0026]

[0027] Among them, ω - represents the reduced bandwidth, ω c0 represents the initial bandwidth, k represents the adaptive adjustment coefficient, (Q V -Q ref ) represents the first difference, Q set Indicates the first setting value.

[0028] In combination with the first aspect, in some possible implementations, the bandwidth of the linear extended state observer is 2 to 10 times the bandwidth of the hybrid power flow controller.

[0029] In conjunction with the first aspect, in some possible implementations, obtaining a target overvoltage at an AC bus of a voltage source converter when a fault occurs includes:

[0030] Obtain the original overvoltage data of the fault at the AC bus of the voltage source converter.

[0031] Based on a preset effective overvoltage range, effective overvoltage is screened out from the original overvoltage data.

[0032] The effective overvoltage is limited to obtain the target overvoltage.

[0033] In combination with the first aspect, in some possible implementations, the preset effective overvoltage range is: 1 kV to 1.5 kV.

[0034] In combination with the first aspect, in some possible implementations, obtaining a reactive power reference signal based on a target overvoltage includes:

[0035] In combination with the third formula, based on the target overvoltage, a reactive power reference signal is obtained.

[0036] The third formula is:

[0037]

[0038] Among them, Q ref represents the reactive power reference signal, and v0 represents the per-unit value of the target overvoltage.

[0039] In a second aspect, an embodiment of the present application provides an overvoltage suppression device, comprising:

[0040] The data acquisition module is used to obtain the target overvoltage at the AC bus of the voltage source converter when a fault occurs.

[0041] The data calculation module is used to obtain a reactive power reference signal based on the target overvoltage.

[0042] The voltage suppression module is used to suppress the target overvoltage based on the actual output reactive power of the voltage source converter and the reactive power reference signal.

[0043] It can be understood that the beneficial effects of the second aspect mentioned above can be found in the relevant description of the first aspect mentioned above, and will not be repeated here.

[0044] Compared with the prior art, the embodiments of the present invention have the following beneficial effects:

[0045] The present application obtains a reactive power reference signal through target overvoltage calculation, and then can adaptively adjust the bandwidth of the hybrid power flow controller according to the actual output power and the reactive power reference signal, thereby achieving the goal of enhancing the suppression effect and improving the suppression response speed. Compared with the traditional method of using a PI controller for adjustment, it is faster while ensuring the suppression effect.

[0046] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0048] Figure 1 It is a flow chart of an overvoltage suppression method provided by an embodiment of the present application;

[0049] Figure 2 It is a structural block diagram of an overvoltage suppression strategy of a hybrid power flow controller combining reactive power adaptive regulation and adaptive linear active disturbance suppression control provided by an embodiment of the present application;

[0050] Figure 3 This is a topological diagram of a hybrid power flow controller provided in an embodiment of the present application;

[0051] Figure 4 This is a schematic diagram of a hybrid power flow controller regulating power flow provided in an embodiment of the present application;

[0052] Figure 5 It is a schematic diagram of the regulation effect of the traditional method provided in one embodiment of the present application and the method of the present application;

[0053] Figure 6 It is a schematic diagram comparing voltage changes between a conventional method provided in an embodiment of the present application and the method of the present application;

[0054] Figure 7 It is a schematic diagram comparing reactive power changes of a conventional method provided in an embodiment of the present application and the method of the present application;

[0055] Figure 8 It is a schematic diagram of the structure of an overvoltage suppression device provided in one embodiment of the present application. DETAILED DESCRIPTION

[0056] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present application. However, it should be clear to those skilled in the art that the present application may also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present application.

[0057] It should be understood that when used in the present specification and the appended claims, the term "comprising" indicates the presence of described features, wholes, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or combinations thereof.

[0058] It should also be understood that the term “and / or” used in the specification and appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0059] As used in the specification and appended claims of this application, the term "if" can be interpreted as "when" or "uponce" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrase "if it is determined" or "if [described condition or event] is detected" can be interpreted as meaning "uponce it is determined" or "in response to determining" or "uponce [described condition or event] is detected" or "in response to detecting [described condition or event]", depending on the context.

[0060] In addition, in the description of the present application specification and the appended claims, the terms "first", "second", "third", etc. are only used to distinguish the descriptions and cannot be understood as indicating or implying relative importance.

[0061] References to "one embodiment" or "some embodiments" etc. described in the specification of this application mean that one or more embodiments of the present application include specific features, structures or characteristics described in conjunction with the embodiment. Therefore, the statements "in one embodiment", "in some embodiments", "in some other embodiments", "in some other embodiments", etc. that appear in different places in this specification do not necessarily refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "including", "comprising", "having" and their variations all mean "including but not limited to", unless otherwise specifically emphasized in other ways.

[0062] The present application provides an overvoltage suppression method.

[0063] Figure 1 is a schematic diagram of the process of an overvoltage suppression method provided in an embodiment of the present application, referring to Figure 1 , the overvoltage suppression method is described in detail as follows:

[0064] Step 101, obtaining a target overvoltage at an AC bus of a voltage source converter due to a fault.

[0065] Exemplarily, step 101 may include:

[0066] Obtain the original overvoltage data of the fault at the AC bus of the voltage source converter.

[0067] Based on a preset effective overvoltage range, effective overvoltage is screened out from the original overvoltage data.

[0068] The effective overvoltage is limited to obtain the target overvoltage.

[0069] Exemplarily, the preset effective overvoltage range is: 1 kV to 1.5 kV.

[0070] Specifically, because different faults cause different overvoltage levels, the overvoltage caused by faults on the secondary side of the excitation transformer and the VSC AC bus is very serious. It cannot be effectively suppressed by controlling the VSC output alone, and it needs to cooperate with the insulation. In order to ensure the effectiveness of the control strategy, it is necessary to screen the effective overvoltage signal and perform a limiting link.

[0071] Step 102: obtaining a reactive power reference signal based on the target overvoltage.

[0072] Exemplarily, step 102 may include:

[0073] In combination with the third formula, based on the target overvoltage, a reactive power reference signal is obtained.

[0074] The third formula can be:

[0075]

[0076] Among them, Q ref represents the reactive power reference signal, and v0 represents the per-unit value of the target overvoltage.

[0077] Step 103: suppressing a target overvoltage based on the actual output reactive power of the voltage source converter and a reactive power reference signal.

[0078] Specifically, in addition to the influence caused by the fault location, the voltage level at the VSC AC bus also needs to consider the influence of the control strategy. The voltage at the VSC AC bus is affected by the VSC output reactive power. When overvoltage occurs, the corresponding VSC output reactive power changes. In order to achieve overvoltage suppression, the VSC output reactive power can be adaptively reversed to achieve the purpose of suppressing overvoltage. The corresponding relationship between output reactive power and suppressed overvoltage level can be obtained for different overvoltage level data. That is, the target overvoltage in the above different value ranges corresponds to the calculation of different reactive power reference signals.

[0079] Exemplarily, step 103 may include:

[0080] The difference between the actual output reactive power of the voltage source converter and the reactive power reference signal is calculated and recorded as the first difference.

[0081] Based on the first difference, a bandwidth of the hybrid power flow controller is adjusted.

[0082] Based on the bandwidth of the hybrid power flow controller, the bandwidth of the linear extended state observer is set to suppress the target overvoltage.

[0083] Exemplarily, adjusting the bandwidth of the voltage source converter based on the first difference may include:

[0084] When the first difference is greater than the first set value, the bandwidth is increased by the adaptive linear active disturbance suppression control hybrid power flow controller.

[0085] When the first difference is less than the first set value, the bandwidth is reduced by the adaptive linear active disturbance suppression control hybrid power flow controller.

[0086] Exemplarily, when the first difference is greater than the first set value, increasing the bandwidth by controlling the hybrid power flow controller through an adaptive linear active disturbance suppression method includes:

[0087] When the first difference is greater than the first set value, the bandwidth is increased by controlling the hybrid power flow controller through an adaptive linear active disturbance suppression method in combination with the first formula.

[0088] The first formula can be:

[0089] ω + =ω c0 +k(ln10(Q V -Q ref )+Q set )

[0090] Among them, ω + represents the increased bandwidth, ω c0 represents the initial bandwidth, k represents the adaptive adjustment coefficient, (Q V -Q ref ) represents the first difference, Q set Indicates the first setting value.

[0091] Exemplarily, when the first difference is less than the first set value, reducing the bandwidth by using an adaptive linear active disturbance suppression control hybrid power flow controller includes:

[0092] When the first difference is less than the first set value, the bandwidth is reduced by controlling the hybrid power flow controller through an adaptive linear active disturbance suppression method in combination with the second formula.

[0093] The second formula can be:

[0094]

[0095] Among them, ω - represents the reduced bandwidth, ω c0 represents the initial bandwidth, k represents the adaptive adjustment coefficient, (Q V -Q ref ) represents the first difference, Q set Indicates the first setting value.

[0096] Specifically, since the transient overvoltage caused by a fault is relatively complex, the use of PI regulation to control reactive power output is a control method based on error elimination, which has a certain lag effect. The effect of suppressing the initial stage of overvoltage and the system response speed cannot meet actual engineering needs.

[0097] At this time, according to the reactive power feedback value of VSC output, the adaptive linear active disturbance rejection control (A-LADRC) can be used to realize the adaptive adjustment of the bandwidth parameters of the hybrid power flow controller to suppress the VSC AC bus overvoltage. The adaptive linear active disturbance rejection control parameters are designed, and the hybrid power flow controller bandwidth parameter selection is designed based on the linear state error feedback (LSEF) control and linear extended state observer (LESO) characteristic equation pole configuration method.

[0098] 1) Linear state error feedback control

[0099] The linear state error feedback control loop can be expressed as:

[0100] u0=k p (R-z1)-k d z2

[0101]

[0102] Among them, u0 is the output control quantity of the linear state error feedback control loop; b0 is the gain coefficient; k p , k d is the gain coefficient of the hybrid power flow controller; z1, z2, z3 are the state variables of LESO respectively; R is the set system input value.

[0103] Consider that a second-order system can usually be expressed as:

[0104]

[0105] Among them, a1 and a0 are control parameters.

[0106] Referring to the pole placement method, let the bandwidth of the hybrid power flow controller be ω c , the closed-loop pole of the system is configured at -ω c Get:

[0107] s 2 +k d s+k p =(s+ωc ) 2

[0108] Correspondingly, we can get:

[0109]

[0110] The bandwidth of the hybrid power flow controller is closely related to the system response speed, but it is difficult to achieve fast and accurate system regulation by only given values, and there may be problems with the response speed being too fast or too slow.

[0111] In order to solve the above problems, this method adopts a method of adaptive adjustment of system bandwidth. By real-time acquisition of the difference between the reactive power output of the VSC and the reactive power reference signal, and comparing it with the first set value, the system bandwidth is changed to achieve accurate and rapid adjustment.

[0112] Considering that the overvoltage magnitude and the VSC output reactive power are within a certain range, k can be set to 5, Q set =4.

[0113] When the first difference is higher than the first set value, the bandwidth is increased to speed up the response; when the first difference is lower than the first set value, the bandwidth is reduced to avoid oscillation.

[0114] 2) Linear Extended State Observer

[0115] LESO can estimate the system state variables in real time based on the input and output information of the system, and has a good anti-disturbance effect on nonlinear systems. The linear extended state observer can be expressed as:

[0116]

[0117] Among them, z1, z2, z3 are state variables; β1, β2, β3 are gain parameters of the linear extended state observer; y is the output.

[0118] Considering the feasibility of applying A-LADRC in engineering and the difficulty of adjusting its control parameters, the pole setting method can be used. Setting the bandwidth parameter of the linear extended state observer to ω0, we can get:

[0119] s 3 +β1s 2 +β2s+β3=(s+ω0) 3

[0120] Correspondingly, we can get:

[0121]

[0122] By adjusting the bandwidth ω0 of the linear extended state observer and the bandwidth ω of the hybrid power flow controller cThe controller parameter design can be realized. Generally, the observer bandwidth ω0 is 4 to 10 times or 2 to 5 times of ω c Let ω c When ω0=500(pu) and ω0=3000(pu), the control effect is optimal.

[0123] Exemplarily, the bandwidth of the linear extended state observer is 2 to 10 times the bandwidth of the hybrid power flow controller.

[0124] The above-mentioned overvoltage suppression method obtains the reactive power reference signal through target overvoltage calculation, and then can adaptively adjust the bandwidth of the hybrid power flow controller according to the actual output power and the reactive power reference signal, so as to achieve the goal of enhancing the suppression effect and improving the suppression response speed. Compared with the traditional method of using PI controller for adjustment, it is faster while ensuring the suppression effect.

[0125] In order to facilitate the understanding of this scheme, Figure 2-7 This section introduces the overall logic and effects of this solution.

[0126] exist Figure 2 In the figure, E1 and E2 are the voltages at both ends of the power supply, Z1 and Z2 are the corresponding line impedances, and P L2 is the output power of the HPFC line, U S , U L Represents the voltage across the phase-shifting transformer PST, P L1 is the output power of the transmission line L1, U E2 is the output voltage of the secondary side of the excitation transformer, K E is the voltage ratio of the current gear of PST, z1, z2, z3 are state variables; β1, β2, β3 are the gain parameters of the linear extended state observer; y is the output; b0 is the gain coefficient, ω c is the bandwidth of the hybrid power flow controller; U2 is the compensation amount, ω0 is the bandwidth of the linear extended state observer, P ref is the reference power, u0 is the output control quantity of the linear state error feedback control loop; k p , k d is the gain coefficient of the hybrid power flow controller, U1 is the voltage adjustment value of VSC, U3 is the output voltage when VSC is working normally, and U T1 is the primary voltage of the excitation transformer, U qref is the given q-axis voltage component.

[0127] In this embodiment, the hybrid power flow controller (HPFC) includes two parts: a phase-shifting transformer (PST) and a VSC. During normal operation, the VSC compensates the voltage to the system to achieve coordination with the PST to control the system power flow. During overvoltage, the control link includes a linear extended state observer (LESO) and a linear state error feedback (LSEF) control to form an adaptive linear active disturbance rejection control (A-LADRC) control.

[0128] For the HPFC system, when a three-phase ground short circuit fault occurs on the primary side of the excitation transformer, the fault causes the voltage on the secondary side of the excitation transformer to drop to zero, and the current on the line connecting the VSC and the secondary side of the excitation transformer increases. At this time, the reactive power consumption of the VSC increases, and overvoltage occurs at the VSC AC bus.

[0129] To achieve overvoltage suppression, the VSC can be controlled to transmit reactive power in reverse to suppress it. The overvoltage signal at the VSC AC bus is used as input to obtain the corresponding reactive power reference signal Q. ref In order to ensure the effectiveness of the reactive power reference signal output by the VSC, it needs to be limited.

[0130]

[0131] Among them, Q ref Represents the reactive power reference signal, v0 represents the overvoltage size (in unit value).

[0132] When facing transient overvoltage problems caused by faults, if the control link adopts the traditional PI adjustment method, there will be a certain lag, and the initial stage of suppressing overvoltage and the system response speed often cannot meet the actual engineering needs. In order to solve this problem, the adaptive linear active disturbance rejection control (A-LADRC) technology can be used according to the reactive power feedback value output by the VSC. The linear state error feedback control and linear state expansion observer parameters in A-LADRC are designed through adaptive adjustment of the controller bandwidth parameters to effectively suppress the overvoltage phenomenon of the VSC AC bus.

[0133] Q ref As the setting input of the linear state error feedback control, referring to the pole placement method, the bandwidth of the hybrid power flow controller is ω c , the closed-loop pole of the system is configured at -ω c The relationship between the hybrid power flow controller bandwidth and the controller gain coefficient is as follows:

[0134]

[0135] It is difficult to adjust quickly and accurately by adjusting the given bandwidth alone. By collecting the difference between the actual value and the reference value of the VSC output reactive power in real time, and comparing it with the power setting value, the system bandwidth can be changed to achieve fast and accurate control. The set power value is defined as Q set .make:

[0136]

[0137] Where k is the adaptive adjustment coefficient; Q V Output reactive power for VSC; Q ref is the reactive power reference value; ω c0 is the initial bandwidth.

[0138] Considering that the overvoltage magnitude and the VSC output reactive power are within a certain range, k can be set to 5, Q set =4.

[0139] When the first difference is higher than the first set value, the bandwidth is increased to speed up the response; when the first difference is lower than the first set value, the bandwidth is reduced to avoid oscillation.

[0140] In order to improve the anti-disturbance effect of the system, the linear extended state observer collects the system input and output to estimate the system state variables in real time. The linear extended state observer can be expressed as:

[0141]

[0142] Among them, z1, z2, z3 are state variables; β1, β2, β3 are gain parameters of the linear extended state observer; y is the output.

[0143] Referring to the pole configuration method, the relationship between the observer gain parameter and the bandwidth parameter is as follows:

[0144]

[0145] By adjusting the linear state observer bandwidth ω0 and the hybrid power flow controller bandwidth ω c The system parameter design can be realized, and finally the overvoltage at the VSC AC bus can be suppressed quickly and effectively.

[0146] exist Figure 3The structure of the hybrid power flow controller is introduced in detail, combining PST and VSC to continuously and accurately control the power flow of the line. The PST uses a double-core symmetrical phase-shifting transformer, which consists of a series transformer (ST) and an excitation transformer (ET). The PST is connected in series to the transmission line, and by changing the voltage of the transmission line, the voltage at the L end of the transmission line is adjusted to achieve the purpose of regulating the power flow. Figure 3 The primary side of the ST is connected in series with the transmission line, and the secondary side is delta-connected; the primary and secondary sides of the ET are both star-connected.

[0147] The PST structure is as follows Figure 3 As shown. PST is connected in series in the transmission line, and the voltage at the L end of the transmission line is adjusted by changing the voltage of the transmission line in series, where K E Indicates ET ratio, K S Indicates the ST ratio.

[0148] Taking phase A as an example, the excitation transformer obtains voltage from the transmission line. The primary and secondary voltages of the excitation transformer are U E1A , U E2A , the voltage across PST is The phase difference between the two ends is e jδ The compensation voltage of the series transformer connected to the transmission line is U stA :

[0149] U stA =K S (U E2C -U E2B )

[0150] U E2A =K E U E1A

[0151] U SA -U LA =U stA

[0152]

[0153] By adjusting the ET tap, K E , thereby changing the secondary side voltage U E2A , then adjust ST ratio K S , which can change the voltage of the series-connected line, and thus change the line voltage and line flow.

[0154] On the secondary side of the excitation transformer, the VSC is connected in series and used in conjunction with a phase-shifting transformer. The output voltage of the VSC is adjustable according to the target power flow. E3A and ET secondary voltage U E2ACoaxial superposition further adjusts the voltage returned by ET to the line, thereby adjusting the phase difference and power flow at both ends of PST, and finely adjusting the system power flow.

[0155] Taking phase A as an example, when PST works independently, the phase difference between the two ends of the line is δ1, and the phase difference corresponding to the target power is δ2. At this time, by controlling the VSC output and U E2A The voltage U in phase E3A The line power flow can reach the target value by making the phase difference between the two ends of the line reach the target value δ2, as shown in the following example: Figure 4 shown.

[0156] like Figure 5 As shown, the overvoltage suppression strategy provided in this embodiment can quickly and effectively suppress overvoltage at the VSC AC bus.

[0157] in, Figure 5 Taking phase A as an example, the proposed control of VSC reactive power output to suppress overvoltage at the VSC AC bus is proven to be effective. The overvoltage suppression effect of HPFC combined with reactive power adaptive regulation and A-LADRC control is more obvious than that of traditional PI regulation, and the suppression speed is faster. Figure 6 Characterizing the change in voltage amplitude at the VSC AC bus, compared with traditional PI regulation, when the HPFC overvoltage suppression strategy combining reactive power adaptive regulation and A-LADRC control is adopted, the system response speed is faster, which can effectively solve the problem of hysteresis effect in traditional PI regulation, and the suppression effect is more obvious in the initial stage. Figure 7 Characterizing the change of VSC output reactive power, compared with traditional PI regulation, the method provided in this example, combining reactive power adaptive regulation and HPFC overvoltage suppression controlled by A-LADRC, can better regulate VSC reactive power, effectively reduce the difficulty of parameter design, shorten the system stabilization time, and have better suppression effect in the initial stage.

[0158] It should be understood that the size of the serial numbers of the steps in the above embodiments does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0159] Corresponding to the overvoltage suppression method described in the above embodiment, Figure 8 A structural block diagram of an overvoltage suppression device provided in an embodiment of the present application is shown. For ease of explanation, only the parts related to the embodiment of the present application are shown.

[0160] See also Figure 8 , the overvoltage suppression device in the embodiment of the present application may include:

[0161] The data acquisition module 201 is used to acquire a target overvoltage at the AC bus of the voltage source converter when a fault occurs.

[0162] The data calculation module 202 is used to obtain a reactive power reference signal based on the target overvoltage.

[0163] The voltage suppression module 203 is used to suppress the target overvoltage based on the actual output reactive power of the voltage source converter and the reactive power reference signal.

[0164] Exemplarily, the voltage suppression module 203 may be used to:

[0165] The difference between the actual output reactive power of the voltage source converter and the reactive power reference signal is calculated and recorded as the first difference.

[0166] Based on the first difference, a bandwidth of the hybrid power flow controller is adjusted.

[0167] Based on the bandwidth of the hybrid power flow controller, the bandwidth of the linear extended state observer is set to suppress the target overvoltage.

[0168] Exemplarily, the voltage suppression module 203 may also be used for:

[0169] When the first difference is greater than the first set value, the bandwidth is increased by the adaptive linear active disturbance suppression control hybrid power flow controller.

[0170] When the first difference is less than the first set value, the bandwidth is reduced by the adaptive linear active disturbance suppression control hybrid power flow controller.

[0171] Exemplarily, the voltage suppression module 203 may also be used for:

[0172] When the first difference is greater than the first set value, the bandwidth is increased by controlling the hybrid power flow controller through an adaptive linear active disturbance suppression method in combination with the first formula.

[0173] The first formula can be:

[0174] ω + =ω c0 +k(ln10(Q V -Q ref )+Q set )

[0175] Among them, ω + represents the increased bandwidth, ω c0 represents the initial bandwidth, k represents the adaptive adjustment coefficient, (Q V -Q ref ) represents the first difference, Q set Indicates the first setting value.

[0176] Exemplarily, the voltage suppression module 203 may also be used for:

[0177] When the first difference is less than the first set value, the bandwidth is reduced by controlling the hybrid power flow controller through an adaptive linear active disturbance suppression method in combination with the second formula.

[0178] The second formula can be:

[0179]

[0180] Among them, ω - represents the reduced bandwidth, ω c0 represents the initial bandwidth, k represents the adaptive adjustment coefficient, (Q V -Q ref ) represents the first difference, Q set Indicates the first setting value.

[0181] Exemplarily, the bandwidth of the linear extended state observer is 2 to 10 times the bandwidth of the hybrid power flow controller.

[0182] Exemplarily, the data acquisition module 201 may include:

[0183] Obtain the original overvoltage data of the fault at the AC bus of the voltage source converter.

[0184] Based on a preset effective overvoltage range, effective overvoltage is screened out from the original overvoltage data.

[0185] The effective overvoltage is limited to obtain the target overvoltage.

[0186] Exemplarily, the preset effective overvoltage range is: 1 kV to 1.5 kV.

[0187] Exemplarily, the data calculation module 202 may include:

[0188] In combination with the third formula, based on the target overvoltage, a reactive power reference signal is obtained.

[0189] The third formula can be:

[0190]

[0191] Among them, Q ref represents the reactive power reference signal, and v0 represents the per-unit value of the target overvoltage.

[0192] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0193] Those of ordinary skill in the art will appreciate that the templates, units, and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0194] If the module / unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present invention implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by the processor, the steps of the above-mentioned various overvoltage suppression method embodiments can be implemented. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium may include: any entity or device that can carry the computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory, random access memory, electrical carrier signal, telecommunication signal and software distribution medium.

[0195] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. An overvoltage suppression method, characterized in that: include: Obtaining a target overvoltage at the AC busbar of the voltage source converter when a fault occurs; Based on the target overvoltage, obtaining a reactive power reference signal; The target overvoltage is suppressed based on the actual output reactive power of the voltage source converter and a reactive power reference signal.

2. The overvoltage suppression method according to claim 1, characterized in that: The method of suppressing the target overvoltage based on the actual output reactive power of the voltage source converter and the reactive power reference signal comprises: Calculating the difference between the actual output reactive power of the voltage source converter and the reactive power reference signal, and recording it as a first difference; Based on the first difference, adjusting the bandwidth of the hybrid power flow controller; Based on the bandwidth of the hybrid power flow controller, the bandwidth of the linear extended state observer is set to suppress the target overvoltage.

3. The overvoltage suppression method according to claim 2, characterized in that: The adjusting the bandwidth of the voltage source converter based on the first difference includes: When the first difference is greater than a first set value, increasing the bandwidth of the hybrid power flow controller through adaptive linear active disturbance suppression control; When the first difference is less than the first set value, the hybrid power flow controller reduces the bandwidth through adaptive linear active disturbance suppression control.

4. The overvoltage suppression method according to claim 3, characterized in that: When the first difference is greater than a first set value, increasing the bandwidth of the hybrid power flow controller by adaptive linear active disturbance suppression control includes: When the first difference is greater than a first set value, the hybrid power flow controller is controlled to increase the bandwidth by adaptive linear active disturbance suppression in combination with the first formula; The first formula is: ω + =ω c0 +k(ln10(Q V -Q ref )+Q set ) Among them, ω + represents the increased bandwidth, ω c0 represents the initial bandwidth, k represents the adaptive adjustment coefficient, (Q V -Q ref ) represents the first difference, Q set Indicates the first set value.

5. The overvoltage suppression method according to claim 3, characterized in that: When the first difference is less than the first set value, reducing the bandwidth of the hybrid power flow controller by adaptive linear active disturbance suppression control includes: When the first difference is less than the first set value, combining the second formula, controlling the hybrid power flow controller to reduce the bandwidth through adaptive linear active disturbance suppression; The second formula is: Among them, ω- represents the reduced bandwidth, ω c0 represents the initial bandwidth, k represents the adaptive adjustment coefficient, (Q V -Q ref ) represents the first difference, Q set Indicates the first set value.

6. The overvoltage suppression method according to claim 2, characterized in that: The bandwidth of the linear extended state observer is 2 to 10 times the bandwidth of the hybrid power flow controller.

7. The overvoltage suppression method according to claim 1, characterized in that: The step of obtaining a target overvoltage at an AC busbar of a voltage source converter due to a fault comprises: Obtaining raw overvoltage data at the AC bus of the voltage source converter at fault; Based on a preset effective overvoltage range, screening out effective overvoltage from the original overvoltage data; The effective overvoltage is limited to obtain the target overvoltage.

8. The overvoltage suppression method according to claim 7, characterized in that: The preset effective overvoltage range is: 1 kV to 1.5 kV.

9. The overvoltage suppression method according to claim 1, characterized in that: The obtaining of a reactive power reference signal based on the target overvoltage comprises: In combination with the third formula, based on the target overvoltage, the reactive power reference signal is obtained; The third formula is: Among them, Q ref represents the reactive power reference signal, and v0 represents the per-unit value of the target overvoltage.

10. An overvoltage suppression device, characterized in that: include: A data acquisition module, used to acquire a target overvoltage at the AC busbar of a voltage source converter when a fault occurs; A data calculation module, used for obtaining a reactive power reference signal based on the target overvoltage; The voltage suppression module is used to suppress the target overvoltage based on the actual output reactive power of the voltage source converter and the reactive power reference signal.

Images