Transient overvoltage suppression method, system and device based on low residual voltage arrester

Abstract

The application provides a low-residual-voltage arrester-based transient overvoltage suppression method, system and device, and relates to the field of transient overvoltage suppression. The method comprises the following steps: calculating the DC power in the steady state; when commutation failure occurs on the inverter side, the DC sending end AC bus generates a transient overvoltage phenomenon, the requirement for suppressing the overvoltage of the sending end is determined according to the DC power in the steady state, and the related parameters of the low-residual-voltage arrester are calculated; the low-residual-voltage arrester is configured, and the configured low-residual-voltage arrester is arranged at the DC sending end AC bus position in the new energy sending grid topology diagram which lacks conventional power support, the transient overvoltage peak value of the sending end AC bus is determined; it is judged whether the transient overvoltage peak value of the sending end AC bus meets the requirement of the grid on the transient overvoltage of the sending end AC bus; if yes, the related parameters are output, and if no, the related parameters are reset. The application can suppress the transient overvoltage of the sending end system which lacks conventional power support.

Description

Technical Field

[0001] This invention relates to the field of transient overvoltage suppression, and in particular to a transient overvoltage suppression method, system and device based on a low residual voltage surge arrester. Background Technology

[0002] In recent years, several transient overvoltages at the sending end of high-voltage direct current (HVDC) transmission lines caused by commutation failures have occurred, leading to continuous grid disconnections of large-scale wind turbines and posing a serious threat to the safe and stable operation of the power system. Therefore, methods for suppressing transient overvoltages in sending-end systems without conventional power supply support are particularly important.

[0003] To suppress transient overvoltages at the DC sending end, there are currently two main approaches: first, suppressing overvoltages through parameter optimization of the control system; and second, suppressing overvoltages through external auxiliary equipment. Regarding DC control parameter optimization, existing research has proposed optimizing the parameters of the constant current control loop based on the magnitude of the transient overvoltage to further suppress it. However, this control strategy is relatively complex, requiring extensive data communication, which is not conducive to transient control. External auxiliary equipment currently mainly focuses on reactive power compensation devices to dissipate redundant reactive power. Researchers have investigated the potential for STATCOM to contribute to transient overvoltage suppression, studying its response hysteresis characteristics and proposing an optimization strategy based on damping switching. However, this method has only been validated under the CIGRE-HVDC standard model, and its applicability remains unknown. Although reactive power compensation devices can provide flexible negative compensation for redundant reactive power, some reactive power compensation devices exhibit a "reverse adjustment" problem with voltage, which can further worsen the overvoltage.

[0004] Surge arresters, as energy dissipation devices, have promising application prospects due to their advantages of rapid response and "zero" control requirements. However, for scenarios with large-capacity, high-proportion centralized access to new energy sources and a lack of conventional power supply support, there is currently a lack of analysis on the energy consumption requirements of transient overvoltages in such scenarios. Furthermore, the existing surge arrester parameters and configurations cannot meet the energy consumption demands, thus failing to suppress transient overvoltages in systems lacking conventional power supply support. Summary of the Invention

[0005] The purpose of this invention is to provide a transient overvoltage suppression method, system, and device based on a low residual voltage surge arrester, in order to solve the problem of being unable to suppress transient overvoltages in a power supply system lacking conventional power support.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] A transient overvoltage suppression method based on a low residual voltage surge arrester includes:

[0008] Based on the topology of the renewable energy transmission grid lacking conventional power support, calculate the steady-state DC power.

[0009] When a commutation failure occurs on the inverter side, a transient overvoltage occurs on the DC sending-end AC bus. The overvoltage suppression requirement is determined based on the steady-state DC power. The overvoltage suppression requirement includes energy dissipation requirements and voltage amplitude suppression requirements.

[0010] Based on the requirement to suppress overvoltage at the sending end, the relevant parameters of the low residual voltage surge arrester are calculated; the relevant parameters include rated voltage, trigger voltage, rated current, maximum absorbed energy, and number of configuration groups;

[0011] Configure the low residual voltage surge arrester according to the rated voltage, the trigger voltage, the rated current and the maximum absorbed energy, and set the configured low residual voltage surge arrester at the position of the DC sending end AC bus in the topology diagram of the new energy power grid that lacks conventional power support, according to the configured group number, and determine the peak value of transient overvoltage of the sending end AC bus.

[0012] Determine whether the peak value of the transient overvoltage of the sending-end AC bus meets the grid's requirements for transient overvoltage of the sending-end AC bus; if yes, output the relevant parameters; if no, readjust the relevant parameters.

[0013] Optionally, the steady-state DC power P dr For: P dr =P L +P LPV -P S Among them, P L The active power of the wind turbine cluster bus; P LPV The active power of the photovoltaic unit's busbar; P S This refers to the active power flowing into the AC power grid.

[0014] Optionally, the energy dissipation requirement W need for: Among them, P need For those with power dissipation requirements; t str The time it takes for the surge arrester to begin dissipating energy; t end This refers to the time it takes for the surge arrester to finish dissipating energy.

[0015] Optionally, use the formula Calculate the rated current P of the low residual voltage surge arrester; where U is the rated voltage and Z is the impedance modulus of the surge arrester. This is the power factor angle of the surge arrester.

[0016] Optionally, use the formula Calculate the rated current of the low residual voltage surge arrester; where P arrThe active power consumed by the surge arrester impedance; U” acr This is the voltage to ground of the surge arrester impedance; This is the power factor angle of the surge arrester.

[0017] Optionally, use the formula Calculate the maximum absorbed energy E max Among them, P arr (t) represents the active power dissipated by the surge arrester, t str t is the time it takes for the surge arrester to begin absorbing energy. end U is the time it takes for the surge arrester to finish dissipating energy. N This is the rated voltage of the surge arrester.

[0018] Optionally, use the formula Calculate the number of configuration groups, n.

[0019] A transient overvoltage suppression system based on a low residual voltage surge arrester includes:

[0020] The DC power calculation module is used to calculate the steady-state DC power based on the topology of a new energy power grid that lacks conventional power support.

[0021] The overvoltage suppression requirement determination module is used to determine the overvoltage suppression requirement based on the steady-state DC power when a commutation failure occurs on the inverter side and a transient overvoltage occurs on the DC sending-end AC bus. The overvoltage suppression requirement includes energy dissipation requirements and voltage amplitude suppression requirements.

[0022] The relevant parameter calculation module is used to calculate the relevant parameters of the low residual voltage surge arrester based on the requirement to suppress overvoltage at the sending end; the relevant parameters include rated voltage, trigger voltage, rated current, maximum absorbed energy, and number of configuration groups;

[0023] The peak value determination module for transient overvoltage of AC bus at the sending end is used to configure the low residual voltage surge arrester according to the rated voltage, the trigger voltage, the rated current and the maximum absorbed energy, and to set the configured low residual voltage surge arrester at the position of the DC sending end AC bus in the topology diagram of the new energy power grid that lacks conventional power support according to the configuration group number, so as to determine the peak value of transient overvoltage of AC bus at the sending end.

[0024] The relevant parameter setting module is used to determine whether the peak value of the transient overvoltage of the sending-end AC bus meets the grid's requirements for transient overvoltage of the sending-end AC bus; if yes, the relevant parameters are output; if no, the relevant parameters are readjusted.

[0025] An electronic device includes a memory and a processor, the memory storing a computer program, and the processor running the computer program to cause the electronic device to perform the above-described transient overvoltage suppression method based on a low residual voltage surge arrester.

[0026] A computer-readable storage medium storing a computer program that, when executed by a processor, implements the above-described transient overvoltage suppression method based on a low residual voltage surge arrester.

[0027] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects: Based on the topology of a new energy power grid lacking conventional power support, the requirement to suppress overvoltage at the sending end after commutation failure is determined according to the DC power in steady state, thereby designing relevant parameters for a low residual voltage surge arrester. The low residual voltage surge arrester configured according to the relevant parameters is installed at the position of the DC sending end AC bus in the new energy power grid topology lacking conventional power support, and the peak value of transient overvoltage at the sending end AC bus is determined so that the peak value of transient overvoltage at the sending end AC bus meets the grid's requirements for transient overvoltage at the sending end AC bus, thereby effectively suppressing transient overvoltage in the sending end system lacking conventional power support. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 The flowchart of the transient overvoltage suppression method based on low residual voltage surge arrester provided by the present invention is shown below;

[0030] Figure 2 A topology diagram of a power grid for transmitting new energy sources that lack conventional power support.

[0031] Figure 3 A design flowchart for the relevant parameters of a low residual voltage surge arrester based on suppression requirements;

[0032] Figure 4 This is a schematic diagram of the installation position of the surge arrester provided by the present invention.

[0033] Figure 5 A graph showing the overvoltage suppression of a low residual voltage surge arrester under minor fault conditions;

[0034] Figure 6 A graph showing the overvoltage suppression of a low residual voltage surge arrester under severe fault conditions;

[0035] Figure 7This is a system operating condition diagram under two commutation failure faults; among them, Figure 7 (a) in the figure is the AC voltage curve at the sending end; Figure 7 (b) in the figure is the reactive power consumption curve of the rectifier; Figure 7 (c) in the figure is the DC current curve of the rectifier side; Figure 7 (d) in the figure is the reactive power compensation curve within the station; Figure 7 (e) in the figure is the curve of the firing angle change on the rectifier side; Figure 7 (f) in the figure is a DC voltage variation curve. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] The purpose of this invention is to provide a transient overvoltage suppression method, system, and device based on a low residual voltage surge arrester, which can suppress transient overvoltages in a power supply system lacking conventional power support.

[0038] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0039] Analysis of the mechanism by which inverter-side commutation failure leads to overvoltage at the sending end:

[0040] Without considering the impact of the reactive power compensation device of the wind farm on the system, the transient voltage change rate of the converter station bus on the rectifier side can be expressed as:

[0041]

[0042] In the formula: ΔU is the transient voltage change rate of the converter bus; Q ch Q is the reactive power difference between the AC system and the converter station. ch >0 indicates that the AC system outputs reactive power to the converter station, Q ch <0 indicates that the converter station outputs reactive power to the AC system; S ac S is the short-circuit capacity of the converter bus. ac =S t +S w +S c S t For the short-circuit capacity of traditional thermal power units, S w S represents the short-circuit capacity of the wind farm. c This is the short-circuit capacity of the synchronous adjustment camera.

[0043] The reactive power difference between the AC system and the converter station is:

[0044] Q ch =Q f -Q dr .

[0045] In the formula: Q f The reactive power provided to the AC filters and capacitor compensators of the rectifier station. B c U is the equivalent susceptance of the AC filter and compensator. 1r Q is the AC bus voltage on the rectifier side. dr The reactive power consumed by the rectifier-side converter station.

[0046] Taking the CIGRE standard model as an example, during normal operation, the inverter station uses constant γ angle control, and the rectifier station uses constant current control. In steady state, we have:

[0047] U dr =U dor cosα-R cr I d .

[0048]

[0049] In the formula: U dor U represents the no-load DC voltage value of the rectifier station. doi U represents the no-load DC voltage value of the inverter station; dr Represents the DC voltage on the rectifier side; I d Represents direct current; R cr R ci The equivalent resistances R of the commutator on the rectifier side and inverter side are respectively. cr =3 / πX cr R ci =3 / πX ci X cr X ci These are the leakage reactance values ​​of the commutator transformer on the rectifier side and the commutator transformer on the inverter side, respectively; R d R is the resistance of the DC line; α is the firing angle on the rectifier side; β is the inverter angle on the inverter side; cr R ci These are the equivalent resistances of the rectifier and inverter side commutators, respectively.

[0050] When the harmonic components on both the AC and DC sides are ignored, we have:

[0051]

[0052] In the formula: ω is the power factor angle on the rectifier side; μ is the commutation angle on the rectifier side.

[0053] The reactive power consumed by the rectifier-side converter station

[0054]

[0055] Combining the above equations, we can see that

[0056] In the formula: P d ΔU represents the output power of the rectifier station, and ΔU represents the change in AC bus voltage at the sending end after a fault occurs.

[0057] After a commutation failure, the DC current initially increases, then rapidly decreases to the minimum value of 0.55 pu at the low-voltage current limiting stage. During the recovery process after the fault is cleared, the DC current initially decreases to 0, then gradually returns to the system's rated value. Since the commutation overlap angle has little impact on the reactive power consumed by the converter station, and the firing angle and DC current have the same influence on the reactive power consumed by the converter station, and the transient voltage change rate is approximately inversely proportional to the DC current, two significant peaks will appear in the transient voltage change rate during the rapid decrease of the two currents mentioned above. The causes of these two voltage peaks will be analyzed in detail below.

[0058] The first voltage peak occurs when the inverter-side converter valve fails to commutate continuously, the low-voltage current limiting circuit is activated, the constant current control on the rectifier side begins to respond, the firing angle on the rectifier side increases rapidly, the DC current decreases rapidly, the reactive power consumption of the converter decreases rapidly, while the AC filter in the rectifier-side converter station is still running, the converter station has a large surplus of reactive power, the converter station injects a large amount of reactive power into the AC system, and the AC bus voltage on the rectifier side will experience a sudden increase.

[0059] The second voltage peak: During the recovery process after fault clearance, the inverter-side AC bus voltage rises rapidly. Due to the lag in firing angle control, U... doi The rapid increase in voltage will cause the inverter-side DC current to decrease rapidly from the minimum value of the low-voltage current limiting link, or even decrease to 0. At this time, the rectifier-side current will also decrease rapidly, and the reactive power consumed by the rectifier-side converter station will further decrease. The rectifier-side AC bus voltage will then experience a process of rising again.

[0060] Due to these two voltage peaks, transient overvoltage will occur on the sending-end AC bus.

[0061] like Figure 1 As shown, the present invention provides a transient overvoltage suppression method based on a low residual voltage surge arrester, comprising:

[0062] Step 101: Calculate the steady-state DC power based on the topology of the renewable energy power grid that lacks conventional power supply support.

[0063] Step 102: When a commutation failure occurs on the inverter side, a transient overvoltage phenomenon occurs on the DC sending end AC bus. The overvoltage suppression requirement is determined based on the steady-state DC power. The overvoltage suppression requirement includes energy dissipation requirements and voltage amplitude suppression requirements.

[0064] In practical applications, the requirements for suppressing transient overvoltage at the sending end are analyzed:

[0065] Figure 2 For the power grid topology of new energy transmission lines lacking conventional power support, such as... Figure 2 As shown, the main AC grid at the sending end is far from the new energy base, and the new energy base lacks conventional power support, resulting in an extremely low short-circuit ratio at the new energy base, generally around 1.3. Figure 2 In the diagram, W represents the wind turbine generator; UG represents the voltage of the AC system bus; j represents the imaginary number sign; Q cL Reactive power compensation capacity of wind power collection busbar; Q c1 Q c2 Q represents the reactive power compensation capacity of wind farms 1 and 2, respectively; X1 Q X2 Q xl Q xs This represents the reactive power loss on each line; P is the active power, Q is the reactive power, and P+jQ is the phasor representation of the power.

[0066] Since active power transmission losses are relatively small on the line, taking the converter bus as an example, we derive the active power dissipation requirements for suppressing overvoltage at the sending end. In steady state, since the injected power at the node equals the outflow power, the following equation constraint is satisfied on the converter bus:

[0067] P dr =P L +P LPV -P S

[0068] Q dr =Q L +Q LPV +Q cr -Q S .

[0069] Among them, P dr For DC power, P L The active power of the wind turbine cluster bus; P LPV The active power of the photovoltaic unit's busbar; P S Q represents the active power flowing into the AC power grid. drQ represents the reactive power flowing into the rectifier station. L Q LPV Q S Q represents the reactive power on each line. cr This is for reactive power compensation at the converter bus.

[0070] When a commutation failure occurs on the inverter side, due to the adjustment of the constant current control on the rectifier side, the firing angle α on the rectifier side increases to over 90°. At this time, the DC current increases, and the DC voltage on the rectifier side drops sharply, resulting in a sharp decrease in the DC system's power transmission. At this point, P... dr ≈0. From the perspective of the sending-end AC system, a commutation failure in the DC system is equivalent to a loss of DC rated power P in the AC system. d The "large load" will drastically affect the power flow distribution of the sending-end AC system. To minimize the impact of this "large load" loss on the AC system, it is desirable that the power flowing into the converter bus after the fault equals the DC power at the previous steady state. Therefore, suppressing the power dissipation requirement P for sending-end overvoltage is crucial. need As shown below:

[0071] P need ≥P dr .

[0072] The energy dissipation requirement W for suppressing overvoltage at the sending end can be calculated by combining the overvoltage duration. need :

[0073]

[0074] In the formula, P need For those with power dissipation requirements; t str The time it takes for the surge arrester to begin dissipating energy; t end This refers to the time it takes for the surge arrester to finish dissipating energy.

[0075] According to the requirements of the power grid for transient overvoltage at the DC sending end, the transient overvoltage at the DC sending end shall not exceed 1.3 pu, and the requirement for suppressing the amplitude of transient overvoltage is less than 1.3 pu.

[0076] The combined requirements for suppressing transient overvoltages include energy requirements and voltage amplitude suppression requirements.

[0077] Step 103: Based on the requirement to suppress overvoltage at the sending end, calculate the relevant parameters of the low residual voltage surge arrester; the relevant parameters include rated voltage, trigger voltage, rated current, maximum absorbed energy, and number of configuration groups.

[0078] Parameters for low residual voltage surge arresters designed based on suppression requirements:

[0079] The first step is to calculate the rated voltage of the surge arrester. Based on the rated voltage of the AC bus at the sending end, the continuous operating voltage of the surge arrester is set. The continuous operating voltage of the surge arrester is a commonly used parameter, referring to the effective value of the power frequency voltage that can be continuously applied across the arrester for a long period of time. It is basically equivalent to the maximum phase voltage of the system (the maximum operating line voltage of the system divided by...). ).

[0080] The second step is to calculate the arrester's trigger voltage (residual voltage). Based on reference grid standards, the transient overvoltage should not exceed 1.3 pu, and the arrester's trigger voltage (residual voltage) is set accordingly. The trigger voltage is the voltage threshold at which the arrester begins to conduct. A lower trigger voltage can activate the arrester earlier, providing better protection, but may increase the risk of false triggering. A higher trigger voltage may cause overvoltage to ride through the arrester, affecting protection performance. The appropriate trigger voltage depends on the required overvoltage protection level U of the system. N .

[0081] Based on voltage suppression requirements, in order to suppress overvoltage below 1.3 pu, the trigger voltage should not exceed 1.3 pu. Therefore, low residual voltage surge arresters with a trigger voltage of 1.3 pu are more advantageous.

[0082] The third step is to calculate the rated current (charge rate) of the surge arrester based on the "active power dissipation requirement" and set the rated current (charge rate) of the surge arrester. The rated current is the maximum current that the surge arrester can safely withstand. Selecting an appropriate rated current ensures that the surge arrester will not be damaged or fail during overvoltage events, and the magnitude of the current is related to the impedance of the surge arrester under operating conditions. Active power and impedance satisfy the following relationship:

[0083]

[0084] Where P is the rated current, U is the rated voltage, and Z is the impedance modulus of the surge arrester. The power factor angle of the surge arrester

[0085] Assume the AC bus voltage at the sending end is given by U L Increase to U' L As can be seen from the formula, in order to meet the "power dissipation requirement", the surge arrester must consume at least P active power. d And the overvoltage level of the AC system at the sending end is U” acr At this time, the overvoltage typically reaches approximately 1.4 to 1.5 pu in its most severe condition; therefore, the expression for the rated current is:

[0086]

[0087] In the formula: I N Rated current; P arrThe active power consumed by the surge arrester impedance; U” acr This is the voltage to ground of the surge arrester impedance; The surge arrester power factor angle is given by the angle. r is the arrester resistance; x is the arrester reactance.

[0088] The fourth step is to calculate the maximum energy absorbed by the surge arrester. Based on the severity of the system fault, the maximum energy that needs to be absorbed is calculated. After reducing the arrester's trigger voltage, the energy absorbed by the arrester during overvoltage suppression will increase accordingly, requiring the arrester to have sufficient energy absorption capacity. However, the energy that the arrester needs to absorb varies depending on the system fault conditions. This invention considers different fault conditions in DC engineering and calculates the maximum energy that needs to be absorbed based on power dissipation requirements. Generally, the duration of overvoltage at the sending end is about 30ms. During this period, the DC system can hardly transmit DC power; therefore, the surge arrester needs to consume at least P... d The active power. The energy E required to suppress overvoltage. max (kJ / kV) can be expressed as:

[0089]

[0090] In the formula, E max To maximize energy absorption, P arr The active power dissipated by the surge arrester, t str t is the time it takes for the surge arrester to begin absorbing energy. end U is the time it takes for the surge arrester to finish dissipating energy. N This is the rated voltage of the surge arrester.

[0091] The fifth step is to determine the required number of surge arrester groups based on their energy absorption capacity. Currently, the maximum energy absorbed by a single surge arrester is 54.75 kV / kV. The maximum energy E required to suppress transient overvoltages is calculated in step four. max The number of surge arrester groups, n, can be calculated using the following formula:

[0092]

[0093] Step 6: Based on the relevant parameters of the low residual voltage surge arrester calculated in steps 1 to 5, establish the following in PSCAD: Figure 2The simulation model shown is the same as the low residual voltage surge arrester simulation model. The low residual voltage surge arresters are installed at the DC sending-end AC bus according to the configured number of groups. The peak value of the transient overvoltage of the sending-end AC bus is obtained, and the relevant parameters of the surge arrester are determined based on the simulation results. If the simulation result shows that the peak value of the transient overvoltage of the sending-end converter bus does not exceed 1.3 pu, the setting results of the relevant parameters of the surge arrester are output. If the simulation result shows that the peak value of the transient overvoltage of the sending-end converter bus exceeds 1.3 pu, the reasons why the overvoltage cannot be suppressed below 1.3 pu need to be analyzed, and the relevant parameters need to be set again until the setting results of the relevant parameters of the surge arrester can be output.

[0094] The design process for relevant parameters of low residual voltage surge arresters based on suppression requirements is as follows: Figure 3 As shown.

[0095] Step 104: Configure the low residual voltage surge arrester according to the rated voltage, the trigger voltage, the rated current and the maximum absorbed energy, and set the configured low residual voltage surge arrester at the position of the DC sending end AC bus in the topology diagram of the new energy power grid that lacks conventional power support, according to the configured group number, and determine the peak value of the transient overvoltage of the sending end AC bus.

[0096] Step 105: Determine whether the peak value of the transient overvoltage of the sending-end AC bus meets the grid's requirements for transient overvoltage of the sending-end AC bus; if yes, proceed to step 106; if no, proceed to step 107.

[0097] Step 106: Output the relevant parameters.

[0098] Step 107: Re-tune the relevant parameters.

[0099] Example 2

[0100] Figure 4 This is a schematic diagram of the installation location of the surge arrester provided by the present invention. In order to limit the transient overvoltage problem at the sending end caused by commutation failure, the surge arrester is connected in parallel at the AC bus of the rectifier side of the high voltage DC transmission system.

[0101] Using Thevenin's equivalent method, the equivalent impedance of the AC surge arrester connected to the downstream AC system is as follows:

[0102]

[0103] Among them, Z l For the impedance of the AC system, is the impedance of the AC surge arrester; / / represents two impedances connected in parallel.

[0104] When the system is operating normally, the surge arrester impedance is at a high value (open circuit state), and the resistance tends to infinity. The equivalent impedance Z of the sending-end AC system approaches 0. acr It remains almost unchanged, so it will not have any impact on the system.

[0105] When a commutation failure occurs in a DC system and an overvoltage is generated at the sending end, the surge arrester's impedance senses the voltage rise, its resistance decreases rapidly, and the surge arrester branch conducts. At this time, The equivalent impedance Z of the sending-end AC system gradually increases. acr This will decrease, which is equivalent to reducing the electrical distance between the sending-end AC system and the DC system. The short-circuit capacity S of the sending-end AC system. ac , can be represented as:

[0106]

[0107] In the formula, S ac Z is the short-circuit capacity of the sending-end AC system. acr The equivalent impedance of the sending-end AC system during DC steady-state operation; U s This represents the system's equivalent potential during steady-state DC operation.

[0108] The above analysis shows that after a commutation failure, a large amount of reactive power surges into the sending-end AC system. The surge arrester experiences overvoltage, its impedance decreases, and it can temporarily increase the system's short-circuit capacity. The transient overvoltage ΔU” on the sending-end AC bus after the fault… acr The following formula can be used to calculate:

[0109]

[0110] In the formula, ΔQ” acr S represents the reactive power redundancy at the sending end during the voltage boosting stage. ac This refers to the short-circuit capacity of the AC system.

[0111] As can be seen from the above equation, an increase in the short-circuit capacity Sac leads to an increase in the transient overvoltage ΔU” on the sending-end AC bus. acr The voltage will decrease, thus suppressing the overvoltage at the sending end. Simultaneously, during a fault, the surge arrester provides a short-term channel for active power that cannot be delivered to the DC system. By dissipating a large amount of active power, it buys time for the DC system controller to react, which is beneficial for the recovery of the DC system. This increases the reactive power consumed by the rectifier, reduces the reactive power surplus of the converter station, and further suppresses the overvoltage at the sending end.

[0112] Example 3

[0113] Taking a ±800kV UHVDC demonstration project as an example, a simulation model was established. Through simulation experiments, the effectiveness of the low residual voltage surge arrester designed in this paper in suppressing overvoltage at the sending end was compared and analyzed with that of existing ordinary surge arresters and high charge rate surge arresters.

[0114] Through repeated iterative calculations and extensive simulations using the low residual voltage surge arrester design method provided by this invention, taking a 750kV voltage level surge arrester as an example, the technical parameters of the low residual voltage surge arrester were finally determined, as shown in Table 1.

[0115] Table 1 Technical parameters of 750kV low residual voltage surge arresters

[0116]

[0117] First, the system operating characteristics after the low residual voltage surge arrester is put into operation are compared and analyzed under the following three working conditions.

[0118] Operating Condition 1: Minor Fault (Single-phase inductive grounding fault occurs at the receiving end, grounding inductance L) f =0.7H, fault duration is 0.02s).

[0119] Operating Condition 2: Severe Fault (Single-phase inductive grounding fault occurs at the receiving end, grounding inductance L) f =0.3H, fault duration is 0.05s).

[0120] Condition 3: Two-phase commutation failure fault (a three-phase ground fault occurs at the receiving end, the fault duration is 0.06s, causing two-phase commutation failures in the DC system).

[0121] Figure 5 The graph shows the overvoltage suppression curve of a low residual voltage surge arrester under minor fault conditions. Figure 6 The curves showing the overvoltage suppression of low residual voltage surge arresters under severe fault conditions are shown below. Figures 5-6 As shown, with one low residual voltage surge arrester, under a minor system fault, the overvoltage level at the sending end reaches 1.279 pu. Installing one set of low residual voltage surge arresters within the station can limit the overvoltage level within the converter station to approximately 1.113 pu. Under a severe system fault, the overvoltage level at the sending end reaches 1.381 pu. Installing one set of low residual voltage surge arresters within the station can limit the overvoltage level at the sending end to approximately 1.173 pu.

[0122] Figure 7 The diagram shows the system operating conditions under a two-commutation-failure fault. The DC system experienced two commutation failures. During the first failure, the overvoltage level of the sending-end AC system reached nearly 1.5 pu. After activating a low-residual-voltage surge arrester, during the commutation failure period, the arrester sensed the increased voltage and immediately switched from a high-resistance state to a low-resistance state to discharge current, thereby limiting the overvoltage amplitude. This directly reduced the reactive power compensation within the station. Figure 7 As shown in (d) in the figure; at the same time, it causes the DC voltage on the rectifier side to decrease during the transient overvoltage period, as shown in the figure. Figure 7As shown in (f); under the control of the DC control system, the DC current is further increased, as shown in... Figure 7 As shown in (c) above. Due to the increase in DC current and the decrease in DC voltage, the reactive power consumed by the rectifier will increase, as shown in (c). Figure 7 As shown in (b), at this time, the reactive power surplus on the rectifier side decreases, so the instantaneous overvoltage at the sending end is suppressed to 1.234 pu. Because the low residual voltage surge arrester dissipates redundant active power that cannot flow into the DC system, the DC current increases, the DC voltage decreases, and consequently, the rectifier firing angle increases, as shown in (b). Figure 7 As shown in (e) in the diagram; the reactive power absorbed by the rectifier increases accordingly, thereby suppressing the transient overvoltage at the sending end, as shown in the diagram. Figure 7 As shown in (a) in the figure.

[0123] Secondly, in order to further verify the effect of the proposed low residual voltage surge arrester on the transient overvoltage suppression of the weak sending-end AC power grid, this invention compares the effective values ​​of the sending-end overvoltage under different sending-end power grid strengths based on operating condition 3, and compares and analyzes the ordinary surge arrester (OA), high charge rate surge arrester (HRA) and the low residual voltage surge arrester (LRA) designed in this paper. The comparison results are shown in Table 2.

[0124] Table 2 Overvoltage suppression effect of different surge arresters

[0125]

[0126]

[0127] Based on simulations and considering all factors, the suppression effects of various schemes can be summarized as follows:

[0128] (1) Ordinary surge arrester (OA): For operating condition 3 (two commutation failures), under different short-circuit ratios, ordinary surge arresters cannot suppress the overvoltage to below 1.3pu.

[0129] (2) High charge rate surge arrester (HRA): When the short circuit ratio is below 1.9, the high charge rate surge arrester cannot suppress the overvoltage to below 1.3pu; but when the short circuit ratio is above 1.9, the overvoltage can be suppressed to 1.273pu~1.298pu.

[0130] (3) Low residual voltage surge arrester (LRA): When the short-circuit ratio is extremely low, the overvoltage can be suppressed to 1.203pu~1.234pu; when the short-circuit ratio is higher than 2, the overvoltage level can be limited to below 1.2pu.

[0131] As shown in Table 2, as the grid strength decreases, the overvoltage amplitude increment gradually increases. However, the low residual voltage surge arrester can effectively suppress transient overvoltages below 1.3 pu, and can effectively protect the sending-end grid from the harm of high voltage.

[0132] Example 4

[0133] In order to implement the method corresponding to Embodiment 1 above and achieve the corresponding functions and technical effects, a transient overvoltage suppression system based on a low residual voltage surge arrester is provided below.

[0134] A transient overvoltage suppression system based on a low residual voltage surge arrester includes:

[0135] The DC power calculation module is used to calculate the steady-state DC power based on the topology of a new energy power grid that lacks conventional power supply support.

[0136] The overvoltage suppression requirement determination module is used to determine the overvoltage suppression requirement based on the steady-state DC power when a commutation failure occurs on the inverter side and a transient overvoltage occurs on the DC sending-end AC bus. The overvoltage suppression requirement includes energy dissipation requirement and voltage amplitude suppression requirement.

[0137] The relevant parameter calculation module is used to calculate the relevant parameters of the low residual voltage surge arrester based on the requirement to suppress overvoltage at the sending end; the relevant parameters include rated voltage, trigger voltage, rated current, maximum absorbed energy, and number of configuration groups.

[0138] The peak value determination module for transient overvoltage of AC bus at the sending end is used to configure the low residual voltage surge arrester according to the rated voltage, the trigger voltage, the rated current and the maximum absorbed energy, and to set the configured low residual voltage surge arrester at the position of the DC sending end AC bus in the topology diagram of the new energy power grid that lacks conventional power support according to the number of configuration groups, so as to determine the peak value of transient overvoltage of AC bus at the sending end.

[0139] The relevant parameter setting module is used to determine whether the peak value of the transient overvoltage of the sending-end AC bus meets the grid's requirements for transient overvoltage of the sending-end AC bus; if yes, the relevant parameters are output; if no, the relevant parameters are readjusted.

[0140] Example 5

[0141] This invention provides an electronic device including a memory and a processor. The memory stores a computer program, and the processor runs the computer program to enable the electronic device to perform the transient overvoltage suppression method based on a low residual voltage surge arrester provided in Embodiment 1.

[0142] In practical applications, the aforementioned electronic devices can be servers.

[0143] In practical applications, electronic devices include: at least one processor, memory, bus, and communication interface.

[0144] The processor, communication interface, and memory communicate with each other via a communication bus.

[0145] A communication interface is used to communicate with other devices.

[0146] The processor is used to execute programs, specifically the methods described in the above embodiments.

[0147] Specifically, the program may include program code, which includes computer operation instructions.

[0148] The processor may be a central processing unit (CPU), an application-specific integrated circuit (ASIC), or one or more integrated circuits configured to implement embodiments of the present invention. The electronic device may include one or more processors of the same type, such as one or more CPUs; or it may include processors of different types, such as one or more CPUs and one or more ASICs.

[0149] Memory is used to store programs. Memory may include high-speed RAM, and may also include non-volatile memory, such as at least one disk storage device.

[0150] Based on the description of the above embodiments, this application provides a storage medium storing computer program instructions thereon, which can be executed by a processor to implement the methods described in any embodiment.

[0151] The transient overvoltage suppression system based on a low residual voltage surge arrester provided in this application exists in various forms, including but not limited to:

[0152] (1) Mobile communication devices: These devices are characterized by their mobile communication capabilities and primarily aim to provide voice and data communication. These terminals include: smartphones (e.g., iPhones), multimedia phones, feature phones, and low-end phones, etc.

[0153] (2) Ultra-mobile personal computer devices: These devices fall under the category of personal computers, possessing computing and processing capabilities, and generally also have mobile internet access capabilities. These terminals include PDAs, MIDs, and UMPCs, such as the iPad.

[0154] (3) Portable entertainment devices: These devices can display and play multimedia content. This category includes: audio and video players (such as iPods), handheld game consoles, e-books, as well as smart toys and portable car navigation devices.

[0155] (4) Other electronic devices with data interaction functions.

[0156] Specific embodiments of the subject matter have now been described. Other embodiments are within the scope of the appended claims. In some cases, the actions described in the claims can be performed in a different order and still achieve the desired result. Furthermore, the processes depicted in the drawings do not necessarily require a specific or sequential order to achieve the desired result. In some embodiments, multitasking and parallel processing can be advantageous.

[0157] The systems, devices, modules, or units described in the above embodiments can be implemented by computer chips or entities, or by products with certain functions. A typical implementation device is a computer. Specifically, a computer can be, for example, a personal computer, laptop computer, cellular phone, camera phone, smartphone, personal digital assistant, media player, navigation device, email device, game console, tablet computer, wearable device, or any combination of these devices.

[0158] For ease of description, the above apparatus is described by dividing it into various functional units. Of course, in implementing this application, the functions of each unit can be implemented in one or more software and / or hardware components. Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0159] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create a machine for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0160] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0161] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0162] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0163] Memory may include non-persistent storage in computer-readable media, such as random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM. Memory is an example of computer-readable media.

[0164] Computer-readable media, including both permanent and non-permanent, removable and non-removable media, can store information using any method or technology. Information can be computer-readable instructions, data structures, program modules, or other data. Examples of computer storage media include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, and CD-ROM.

[0165] Digital multifunction optical disc (DVD) or other optical storage, magnetic cassette tape, magnetic tape, disk storage or other magnetic storage devices

[0166] Or any other non-transmission medium that can be used to store information that can be accessed by a computing device. As defined herein, computer-readable media does not include transient media, such as modulated data signals and carrier waves.

[0167] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0168] This application can be described in the general context of computer-executable instructions that are executed by a computer, such as program modules. Generally, program modules include routines, programs, objects, components, data structures, etc., that perform specific transactions or implement specific abstract data types. This application can also be practiced in distributed computing environments where transactions are performed by remote processing devices connected via a communication network. In distributed computing environments, program modules can reside in local and remote computer storage media, including storage devices.

[0169] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple; relevant parts can be referred to the method section.

[0170] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A transient overvoltage suppression method based on a low residual voltage surge arrester, characterized in that, include: Based on the topology of the renewable energy transmission grid lacking conventional power support, calculate the steady-state DC power. When a commutation failure occurs on the inverter side, a transient overvoltage occurs on the DC sending-end AC bus. The overvoltage suppression requirement is determined based on the steady-state DC power. The overvoltage suppression requirement includes energy dissipation requirements and voltage amplitude suppression requirements. Based on the requirement to suppress overvoltage at the sending end, the relevant parameters of the low residual voltage surge arrester are calculated; the relevant parameters include rated voltage, trigger voltage, rated current, maximum absorbed energy, and number of configuration groups; Configure the low residual voltage surge arrester according to the rated voltage, the trigger voltage, the rated current and the maximum absorbed energy, and set the configured low residual voltage surge arrester at the position of the DC sending end AC bus in the topology diagram of the new energy power grid that lacks conventional power support, according to the configured group number, and determine the peak value of transient overvoltage of the sending end AC bus. Determine whether the peak value of the transient overvoltage of the sending-end AC bus meets the grid's requirements for transient overvoltage of the sending-end AC bus; if yes, output the relevant parameters; if no, readjust the relevant parameters.

2. The transient overvoltage suppression method based on a low residual voltage surge arrester according to claim 1, characterized in that, The steady-state DC power P dr For: P dr =P L +P LPV -P S ; Among them, P L P represents the active power of the wind turbine cluster's busbar. LPV The active power of the photovoltaic unit's busbar; P S This refers to the active power flowing into the AC power grid.

3. The transient overvoltage suppression method based on a low residual voltage surge arrester according to claim 1, characterized in that, The energy dissipation requirement W need for: Among them, P need For those with power dissipation requirements; t str The time it takes for the surge arrester to begin dissipating energy; t end This refers to the time it takes for the surge arrester to finish dissipating energy.

4. The transient overvoltage suppression method based on a low residual voltage surge arrester according to claim 1, characterized in that, Using formula Calculate the rated current P of the low residual voltage surge arrester; where U is the rated voltage and Z is the impedance modulus of the surge arrester. This is the power factor angle of the surge arrester.

5. The transient overvoltage suppression method based on a low residual voltage surge arrester according to claim 1, characterized in that, Using formula Calculate the rated current I of the low residual voltage surge arrester. N ; Among them, P arr The active power consumed by the surge arrester impedance; U' a ' cr This is the voltage to ground of the surge arrester impedance; This is the power factor angle of the surge arrester.

6. The transient overvoltage suppression method based on a low residual voltage surge arrester according to claim 1, characterized in that, Using formula Calculate the maximum absorbed energy E max ; Among them, P arr (t) represents the active power dissipated by the surge arrester, t str t is the time it takes for the surge arrester to begin absorbing energy. end U is the time it takes for the surge arrester to finish dissipating energy. N This is the rated voltage of the surge arrester.

7. The transient overvoltage suppression method based on a low residual voltage surge arrester according to claim 6, characterized in that, Using formula Calculate the number of configuration groups, n.

8. A transient overvoltage suppression system based on a low residual voltage surge arrester, characterized in that, include: The DC power calculation module is used to calculate the steady-state DC power based on the topology of a new energy power grid that lacks conventional power support. The overvoltage suppression requirement determination module is used to determine the overvoltage suppression requirement based on the steady-state DC power when a commutation failure occurs on the inverter side and a transient overvoltage occurs on the DC sending-end AC bus. The overvoltage suppression requirement includes energy dissipation requirements and voltage amplitude suppression requirements. The relevant parameter calculation module is used to calculate the relevant parameters of the low residual voltage surge arrester based on the requirement to suppress overvoltage at the sending end; the relevant parameters include rated voltage, trigger voltage, rated current, maximum absorbed energy, and number of configuration groups; The peak value determination module for transient overvoltage of AC bus at the sending end is used to configure the low residual voltage surge arrester according to the rated voltage, the trigger voltage, the rated current and the maximum absorbed energy, and to set the configured low residual voltage surge arrester at the position of the DC sending end AC bus in the topology diagram of the new energy power grid that lacks conventional power support according to the configuration group number, so as to determine the peak value of transient overvoltage of AC bus at the sending end. The relevant parameter setting module is used to determine whether the peak value of the transient overvoltage of the sending-end AC bus meets the grid's requirements for transient overvoltage of the sending-end AC bus; if yes, the relevant parameters are output; if no, the relevant parameters are readjusted.

9. An electronic device, characterized in that, The device includes a memory and a processor, the memory being used to store a computer program, and the processor running the computer program to cause the electronic device to perform the transient overvoltage suppression method based on a low residual voltage surge arrester as described in any one of claims 1-7.

10. A computer-readable storage medium, characterized in that, It stores a computer program that, when executed by a processor, implements the transient overvoltage suppression method based on a low residual voltage surge arrester as described in any one of claims 1-7.

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