Method and system for discriminating tripping of excitation circuit breaker of variable-speed pumped storage unit

Abstract

The invention discloses a method and a system for judging the tripping of an excitation circuit breaker of a variable-speed pumped storage unit, and the method comprises the steps: collecting the three-phase voltage of the high-voltage side of an excitation transformer, the three-phase voltage of the low-voltage side of a main transformer, and the three-phase current of the high-voltage side of the excitation transformer of the variable-speed pumped storage unit; compensating the three-phase voltage of the high-voltage side based on the three-phase current, and respectively calculating the three-phase line voltage of the high-voltage side of the exciting transformer and the three-phase line voltage of the low-voltage side of the main transformer according to the compensated three-phase voltage of the high-voltage side and the three-phase voltage of the low-voltage side; calculating a line voltage effective value average difference value and a line voltage phase average difference value in combination with a power frequency period; and determining the current running state of the variable-speed pumped storage unit, and judging whether the excitation circuit breaker has a trip fault or not. Based on the voltage and current of the high-voltage side of the excitation transformer and the voltage of the low-voltage side of the main transformer, ECB trip judgment and fault protection are achieved, and the accuracy, convenience and reliability of ECB trip judgment are improved.

Description

Technical Field

[0001] This invention belongs to the field of power equipment relay protection technology, and specifically relates to a method and system for detecting unauthorized tripping of excitation circuit breakers in variable speed pumped storage units. Background Technology

[0002] As power systems increasingly exhibit "dual high" characteristics—a high proportion of renewable energy integration and highly volatile load demand—the demand for fast-response, large-capacity peak-shaving and frequency-regulating equipment is growing. Traditional constant-speed pumped-storage units, due to their narrow regulation range and poor regulation flexibility, can no longer fully meet the flexibility and stability requirements of modern power grids. In contrast, such as... Figure 1 The doubly-fed variable-speed pumped storage unit shown can adapt to different head and power conditions by adjusting its speed, maintaining high operating efficiency under a wider range of conditions, especially demonstrating excellent independent control capabilities for active and reactive power. Furthermore, the variable-speed pumped storage unit has a fast control speed, capable of responding to grid frequency fluctuations and load changes within milliseconds, thus showing promising application prospects in new power systems.

[0003] However, in practical applications, due to the complex structure of variable-speed pumped-storage units, they are prone to various types of faults. While they have corresponding protection mechanisms for common faults such as grid-side short circuits and DC bus short circuits, when the excitation circuit breaker (ECB) of a variable-speed pumped-storage unit trips unexpectedly (i.e., the circuit breaker trips without cause), the relevant technologies cannot identify this type of fault, thus lacking a direct corresponding protection mechanism.

[0004] Therefore, how to accurately and efficiently identify the unauthorized tripping fault of the excitation circuit breaker in a variable-speed pumped-storage unit has become an urgent problem to be solved. Summary of the Invention

[0005] The purpose of this invention is to provide a method and system for detecting unauthorized tripping of the excitation circuit breaker (ECB) in a variable-speed pumped-storage unit. Based on the voltage and current on the high-voltage side of the excitation transformer and the low-voltage side voltage of the main transformer, the method enables the detection and fault protection of ECB unauthorized tripping, thereby improving the accuracy, convenience, and reliability of ECB unauthorized tripping detection.

[0006] To achieve the above objectives, the solution of the present invention is:

[0007] A method for detecting unauthorized tripping of excitation circuit breakers in variable-speed pumped-storage units includes,

[0008] Collect the three-phase voltage on the high-voltage side of the excitation transformer, the three-phase voltage on the low-voltage side of the main transformer, and the three-phase current on the high-voltage side of the excitation transformer of the variable-speed pumped-storage unit;

[0009] Based on the high-voltage side three-phase current, the high-voltage side three-phase voltage is compensated, and based on the compensated high-voltage side three-phase voltage and the low-voltage side three-phase voltage, the high-voltage side three-phase line voltage of the excitation transformer and the low-voltage side three-phase line voltage of the main transformer are calculated respectively.

[0010] Based on the three-phase line voltage on the high-voltage side, the three-phase line voltage on the low-voltage side, and the power frequency cycle, calculate the average difference of the effective value of the line voltage and the average difference of the line voltage phase of the variable speed pumped storage unit.

[0011] The current operating state of the variable-speed pumped-storage unit is determined. If the current operating state is any of the multiple target states, the excitation circuit breaker is determined to have experienced a tripping fault based on the average difference of the effective value of the line voltage and the average difference of the phase of the line voltage.

[0012] This includes collecting the three-phase voltage on the high-voltage side of the excitation transformer, the three-phase voltage on the low-voltage side of the main transformer, and the three-phase current on the high-voltage side of the excitation transformer of the variable-speed pumped-storage unit.

[0013] The three-phase voltage on the high-voltage side of the excitation transformer is collected through the voltage transformer on the high-voltage side of the excitation transformer.

[0014] The three-phase voltage on the low-voltage side of the main transformer is collected through the voltage transformer on the low-voltage side of the main transformer.

[0015] The three-phase current on the high-voltage side of the excitation transformer is collected through the current transformer between the high-voltage side of the excitation transformer and the excitation circuit breaker.

[0016] The compensation of the three-phase voltage on the high-voltage side based on the three-phase current on the high-voltage side includes,

[0017] A current-limiting reactor is installed between the low-voltage side of the main transformer and the excitation circuit breaker, and the inductance of the current-limiting reactor is obtained.

[0018] Based on the inductance and the three-phase current, the compensated high-voltage side three-phase voltage is calculated using the following formula.

[0019] ,

[0020] Where L is the inductance of the current-limiting reactor. It is the three-phase current on the high-voltage side of the excitation transformer. It is the three-phase voltage on the high-voltage side of the excitation transformer.

[0021] The calculation of the average difference in the effective value of the line voltage and the average difference in the phase of the line voltage for the variable-speed pumped-storage unit includes,

[0022] Calculate the average effective value of the three-phase line voltage on the high-voltage side of the excitation transformer based on the three-phase line voltage on the high-voltage side and the power frequency period; calculate the average effective value of the three-phase line voltage on the low-voltage side of the main transformer based on the three-phase line voltage on the low-voltage side and the power frequency period.

[0023] The first phase of the AB phase line voltage on the high-voltage side of the excitation transformer and the second phase of the AB phase line voltage on the low-voltage side of the main transformer are calculated using a PLL phase-locked loop.

[0024] The effective value difference of the line voltage is calculated based on the average effective value of the three-phase line voltage on the high-voltage side and the average effective value of the three-phase line voltage on the low-voltage side, and the phase difference of the line voltage is calculated based on the first phase and the second phase.

[0025] The window length of the moving average algorithm is set using the power frequency period. The moving average algorithm is then used to process the effective value difference of the line voltage and the phase difference of the line voltage to obtain the average difference of the effective value of the line voltage and the average difference of the phase difference of the line voltage.

[0026] This includes determining whether the excitation circuit breaker has experienced a sudden tripping fault, including...

[0027] If the average difference of the effective value of the line voltage and the average difference of the phase of the line voltage are both greater than the corresponding difference threshold, the abnormal duration exceeding the difference threshold is recorded.

[0028] If the duration of the abnormality exceeds a time threshold, it is determined that the excitation circuit breaker has experienced a sudden tripping fault.

[0029] After determining that the excitation circuit breaker has experienced a sudden tripping fault, it also includes,

[0030] Control the variable-speed pumped storage unit to perform the trip protection action.

[0031] The multiple target states include no-load, power generation, power generation phase adjustment, pumping, pumping phase adjustment, pumping self-start, and regenerative braking.

[0032] A detection system for unauthorized tripping of excitation circuit breakers in variable-speed pumped-storage units includes,

[0033] The data acquisition module is configured to acquire the three-phase voltage on the high-voltage side of the excitation transformer, the three-phase voltage on the low-voltage side of the main transformer, and the three-phase current on the high-voltage side of the excitation transformer of the variable-speed pumped-storage unit.

[0034] The first calculation module is configured to compensate the three-phase voltage on the high-voltage side based on the three-phase current on the high-voltage side, and calculate the three-phase line voltage on the high-voltage side of the excitation transformer and the three-phase line voltage on the low-voltage side of the main transformer based on the compensated three-phase voltage on the high-voltage side and the three-phase voltage on the low-voltage side, respectively.

[0035] The second calculation module is configured to calculate, based on the high-voltage side three-phase line voltage, the low-voltage side three-phase line voltage, and the power frequency cycle, the average difference in the effective value of the line voltage and the average difference in the line voltage phase of the variable-speed pumped-storage unit; and...

[0036] The discrimination module is configured to determine the current operating state of the variable speed pumped storage unit, and if the current operating state is any of a plurality of target states, to determine whether the excitation circuit breaker has experienced a tripping fault based on the average difference of the effective value of the line voltage and the average difference of the phase of the line voltage.

[0037] The system also includes,

[0038] The protection module is configured to control the variable-speed pumped-storage unit to perform a trip protection action after determining that the excitation circuit breaker has tripped unexpectedly.

[0039] An electronic device, comprising,

[0040] processor;

[0041] Memory used to store the processor's executable instructions;

[0042] The processor is configured to execute the instructions to implement the aforementioned method for detecting unauthorized tripping of the excitation circuit breaker in a variable-speed pumped-storage unit.

[0043] A computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the aforementioned method for detecting unauthorized tripping of the excitation circuit breaker in a variable-speed pumped-storage unit.

[0044] By adopting the above solution, the present invention has at least the following beneficial effects:

[0045] (1) This invention analyzes the different fault characteristics exhibited by the unit under different operating conditions after the excitation circuit breaker trips unexpectedly. It selects the voltage and current on the high-voltage side of the excitation transformer and the low-voltage side voltage of the main transformer to determine the ECB tripping unexpectedly. The existing voltage and current transformers in the excitation system of the variable speed pumped storage unit are used to measure the corresponding judgment data, so that the original voltage and current measurement points of the unit can be used without adding new measurement points, thus saving the cost required for tripping detection.

[0046] (2) In the operating conditions that require the excitation system to work, such as no-load, power generation, power generation phase adjustment, pumping, pumping phase adjustment, pumping self-start, and regenerative braking, the present invention adds the criteria for the fault tripping, avoiding fault identification in irrelevant operating conditions, which saves computing resources and avoids the probability of misjudgment.

[0047] (3) The present invention uses the effective value of line voltage and the average difference of phase as the criterion. Since the difference is used as the criterion, it will not cause the protection to malfunction when there is a single branch fault in the excitation system. The accuracy and reliability of the judgment result are high.

[0048] (4) The discrimination algorithm of the present invention is relatively simple, the calculation speed is fast, the fault judgment logic is simplified, the efficiency of the fault judgment is improved, and the protection scheme is easy to implement.

[0049] This improves the accuracy, convenience, and reliability of ECB (Electronic Control Board) trip detection, which is conducive to ensuring the safe and stable operation of variable speed pumped storage units. Attached Figure Description

[0050] Figure 1 This is a schematic diagram of the structure of a doubly-fed variable-speed pumped storage unit used in this invention;

[0051] Figure 2 This is a schematic diagram of the excitation system of a doubly-fed variable-speed pumped storage unit.

[0052] Figure 3 This is a flowchart of a method for detecting unauthorized tripping of the excitation circuit breaker in a variable-speed pumped-storage unit, as proposed in an embodiment of the present invention.

[0053] Figure 4 This is a flowchart of a difference calculation method proposed in an embodiment of the present invention;

[0054] Figure 5 This is a schematic diagram illustrating the change of voltage difference over time according to an embodiment of the present invention;

[0055] Figure 6 This is a schematic diagram illustrating the change of phase difference over time according to an embodiment of the present invention;

[0056] Figure 7 This is a schematic diagram of a system for detecting unauthorized tripping of the excitation circuit breaker in a variable-speed pumped-storage unit, as proposed in an embodiment of the present invention. Detailed Implementation

[0057] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0058] It should be noted that, as Figure 2As shown, the excitation system of existing doubly-fed variable-speed pumped-storage units typically includes multiple power branches, each of which includes an excitation transformer (which can be simply referred to as the excitation transformer in this invention) and a frequency converter. In related embodiments, corresponding protection actions are provided for common faults such as grid-side short circuits and DC bus short circuits. However, when the excitation circuit breaker trips unexpectedly (i.e., the circuit breaker trips without cause), there is no direct corresponding protection mechanism in the related embodiments. Although the protection device in the related embodiments can use the "ECB switch position contact" and "current unit operating condition" to identify ECB tripping faults, the position contact has the problem of unreliability and does not meet the requirements of relay protection in practical applications.

[0059] Therefore, this invention proposes a method for detecting unauthorized tripping of excitation circuit breakers in variable-speed pumped-storage units, which can accurately and reliably detect and protect against unauthorized tripping of excitation circuit breakers.

[0060] The following describes in detail, with reference to the accompanying drawings, a method and system for detecting unauthorized tripping of the excitation circuit breaker in a variable-speed pumped-storage unit, as proposed in an embodiment of the present invention.

[0061] Figure 3 This is a flowchart of a method for detecting unauthorized tripping of the excitation circuit breaker in a variable-speed pumped-storage unit, as proposed in an embodiment of the present invention. The method includes the following steps:

[0062] Step S101: Collect the three-phase voltage on the high-voltage side of the excitation transformer, the three-phase voltage on the low-voltage side of the main transformer, and the three-phase current on the high-voltage side of the excitation transformer of the variable-speed pumped-storage unit.

[0063] It should be noted that, in order to design a more accurate ECB (Excitation Circuit Breaker) tripping fault detection scheme, this invention pre-analyzed the characteristics of ECB tripping based on actual conditions, determining the different fault characteristics exhibited by the unit under different operating states after the excitation circuit breaker trips unexpectedly. Specifically, as follows:

[0064] In the first scenario, when the unit is operating under conditions where the active power flow of the excitation system is from the grid to the rotor side, such as subsynchronous power generation, supersynchronous pumping, and self-starting, and the power flow on the rotor side is from the grid to the rotor, after the ECB tripping fault occurs, the DC capacitor voltage drops rapidly to 0 due to the loss of power to the rotor, and the voltages on the high-voltage and low-voltage sides of the excitation transformer also drop rapidly to 0.

[0065] In the second scenario, when the unit is operating under conditions where the active power flow of the excitation system, such as supersynchronous generation, subsynchronous pumping, and regenerative braking, is from the rotor side to the grid side, the DC capacitor voltage rises after the ECB trips. Under normal grid-side control, the DC voltage rises rapidly and continues to deviate from the voltage reference value, causing the current reference value to rise rapidly as well. The grid-side PWM turn-on time is significantly extended, resulting in a significant rise in the grid-side voltage. In other words, after the ECB trips, the voltages on both the low-voltage and high-voltage sides of the excitation transformer also rise rapidly.

[0066] In the third scenario, when the unit is operating under phase-shifting conditions, where the exchange of active power between the grid excitation system and the grid is almost zero, ECB (Excitation Circuit Breaker) tripping faults are difficult to detect. However, in this case, ECB tripping has virtually no impact on unit operation because before the fault, there is no exchange of active and reactive power between the excitation system and the grid, and the current on the ECB is essentially zero. When the unit's condition changes, causing a change in DC voltage, the voltages on the high-voltage and low-voltage sides of the excitation transformer also change accordingly.

[0067] Based on the above analysis, it is clear that ECB (Electronic Circuit Breaker) tripping faults have the most direct impact on the excitation transformer and grid-side inverters. DC voltage and the low-voltage and high-voltage sides of the excitation transformer are suitable criteria for judgment. However, using DC voltage as the criterion requires setting up protection measurement points on multiple inverter DC buses and sending the measurement signals to the protection device, which is difficult and costly. Furthermore, when the grid-side inverter experiences partial DC short circuits or partial grid-side pulse loss, the four DC voltages will exhibit different states, which is detrimental to protection criterion design. Therefore, this invention uses the voltage and current on the high-voltage side of the excitation transformer and the low-voltage side voltage of the main transformer for discrimination calculations, enabling simple and efficient ECB tripping fault detection.

[0068] Specifically, first collect the current three-phase voltage on the high-voltage side of the excitation transformer, the three-phase voltage on the low-voltage side of the main transformer, and the three-phase current on the high-voltage side of the excitation transformer in the excitation system of the variable-speed pumped-storage unit.

[0069] In one embodiment of the present invention, the acquisition of the three-phase voltage on the high-voltage side of the excitation transformer, the three-phase voltage on the low-voltage side of the main transformer, and the three-phase current on the high-voltage side of the excitation transformer of the variable-speed pumped-storage unit includes: acquiring the three-phase voltage on the high-voltage side of the excitation transformer through a voltage transformer on the high-voltage side of the excitation transformer; acquiring the three-phase voltage on the low-voltage side of the main transformer through a voltage transformer on the low-voltage side of the main transformer; and acquiring the three-phase current on the high-voltage side of the excitation transformer through a current transformer between the high-voltage side of the excitation transformer and the excitation circuit breaker.

[0070] Specifically, such as Figure 2As shown, in existing doubly-fed variable-speed pumped-storage unit excitation systems, the high-voltage sides of the excitation transformers of each power branch are connected to the same busbar and then connected to the low-voltage side of the main transformer via an excitation circuit breaker. A voltage transformer (PT) is typically installed at this location for measurement; a PT is also installed on the low-voltage side of the main transformer for measurement; and a current transformer (CT) is used for measurement between the high-voltage side of the excitation transformer and the excitation circuit breaker. Therefore, this invention proposes a design for detecting and protecting against ECB (Extended Circuit Breaker) tripping faults using the existing voltage signals from the high-voltage side of the excitation transformer and the low-voltage side of the main transformer, along with the current from the high-voltage side of the excitation transformer, without requiring additional measurement points.

[0071] Therefore, in this embodiment of the invention, the three-phase voltage on the high-voltage side of the excitation transformer can be directly sampled from the high-voltage side PT of the excitation transformer and the low-voltage side PT of the main transformer, respectively. , , and the low-voltage side voltage of the main transformer , , The three-phase current on the high-voltage side of the excitation transformer is obtained by sampling from the current transformer (CT) between the high-voltage side of the excitation transformer and the excitation circuit breaker. , , .

[0072] Step S102: Based on the parameters of the current-limiting reactor and the three-phase current, the three-phase voltage on the high-voltage side is compensated, and the three-phase line voltage on the high-voltage side of the excitation transformer and the three-phase line voltage on the low-voltage side of the main transformer are calculated according to the compensated three-phase voltage on the high-voltage side and the three-phase voltage on the low-voltage side of the main transformer.

[0073] Specifically, such as Figure 2 As shown, since there is a current-limiting reactor between the low-voltage side of the main transformer and the excitation circuit breaker in the doubly-fed variable-speed pumped-storage unit, it is necessary to compensate the collected voltage to improve the accuracy of the judgment results.

[0074] In one embodiment of the present invention, the high-voltage side three-phase voltage is compensated based on the parameters of the current-limiting reactor and the three-phase current, including: first obtaining the inductance L of the current-limiting reactor; then calculating the compensated high-voltage side three-phase voltage based on the inductance and the three-phase current using the following formula:

[0075]

[0076] Where L is the inductance of the current-limiting reactor. It is the three-phase current on the high-voltage side of the excitation transformer. It is the three-phase voltage on the high-voltage side of the excitation transformer.

[0077] Furthermore, to avoid the impact of stator and rotor grounding faults and reduce misjudgments of tripping faults, this invention uses line voltage to identify tripping faults. Therefore, based on the compensated high-voltage side three-phase voltage and low-voltage side three-phase voltage, the high-voltage side three-phase line voltage of the excitation transformer and the low-voltage side three-phase line voltage of the main transformer are calculated respectively.

[0078] As one possible implementation, the three-phase line voltages can be calculated using the following formula:

[0079]

[0080] in, It is the three-phase line voltage on the low-voltage side of the main transformer. It is the three-phase line voltage on the high-voltage side of the excitation transformer.

[0081] Step S103: Based on the three-phase line voltage on the high-voltage side, the three-phase line voltage on the low-voltage side, and the power frequency cycle, calculate the average difference of the effective value of the line voltage and the average difference of the line voltage phase of the variable speed pumped storage unit.

[0082] Specifically, this invention uses the difference in line voltage as a criterion. Based on the three-phase line voltage on the high-voltage side and the three-phase line voltage on the low-voltage side calculated in the previous step, and the determined power frequency cycle of the unit, the average difference of the effective value of the line voltage of the computer group is calculated. Average phase difference between line voltage and line voltage The power frequency period is the period of the power grid frequency used by the current variable-speed pumped-storage unit, which can be determined in advance based on the power grid frequency under normal conditions.

[0083] To more clearly illustrate the specific implementation process of the line voltage difference calculation of the present invention, the following is an exemplary description of a calculation method proposed in one embodiment of the present invention. Figure 4 This is a flowchart of a difference calculation method proposed in an embodiment of the present invention. The method includes the following steps:

[0084] Step S401: Calculate the average effective value of the three-phase line voltage on the high-voltage side of the excitation transformer based on the three-phase line voltage on the high-voltage side and the power frequency period, and calculate the average effective value of the three-phase line voltage on the low-voltage side of the main transformer based on the three-phase line voltage on the low-voltage side and the power frequency period.

[0085] Specifically, the average effective value of the three-phase line voltage on the high-voltage side of the excitation transformer can be calculated using the effective value formula shown below. Average effective value of three-phase line voltage on the low-voltage side of the main transformer :

[0086]

[0087]

[0088] Where T is the period corresponding to the power frequency.

[0089] Step S402: Calculate the first phase of the AB phase line voltage on the high-voltage side of the excitation transformer and the second phase of the AB phase line voltage on the low-voltage side of the main transformer using a PLL phase-locked loop.

[0090] Specifically, using a PLL (Phase-Locked Loop), calculations are performed respectively. phase (i.e., the first phase) and phase (i.e., the second phase).

[0091] Step S403: Calculate the difference in effective line voltage values ​​based on the average effective values ​​of the three-phase line voltages on the high-voltage side and the average effective values ​​of the three-phase line voltages on the low-voltage side, and calculate the phase difference in line voltage values ​​based on the first phase and the second phase.

[0092] Specifically, the effective value of the line voltage and the difference between its phase are calculated using the following formula:

[0093]

[0094]

[0095] in, This is the difference between the effective values ​​of the line voltages. This represents the phase difference of the line voltage.

[0096] Step S404: Set the window length of the moving average algorithm using the power frequency period, and process the effective value difference of line voltage and the phase difference of line voltage using the set moving average algorithm to obtain the average difference of effective value of line voltage and the average difference of phase of line voltage.

[0097] Specifically, since the phase fluctuates significantly after the excitation circuit breaker ECB trips unexpectedly, in order to further improve the accuracy of the judgment, this invention uses a moving average algorithm to smooth the difference calculated in step S403 to reduce noise.

[0098] In this embodiment, the sliding window length of the moving average algorithm is set to a single power frequency cycle. During processing, as newly calculated difference data is continuously updated, the sliding window moves forward, discarding the oldest data point and adding the latest data point, and then the average is recalculated.

[0099] Therefore, this embodiment processes the above-mentioned line voltage effective value difference and line voltage phase difference using a moving average algorithm with predefined parameters. Using a moving average algorithm with a length of one power frequency cycle, the average value of the above-mentioned difference signals can be effectively calculated, thus obtaining the average difference of the line voltage effective values. Average phase difference between line voltage and line voltage .

[0100] Step S104: Determine the current operating status of the variable speed pumped storage unit. If the current operating status is any of the multiple target states, determine whether the excitation circuit breaker has experienced a tripping fault based on the average difference of the effective value of the line voltage, the average difference of the phase of the line voltage, and the duration of the abnormality.

[0101] Specifically, the current operating status of the variable-speed pumped storage unit is first determined in order to determine whether to activate the fault detection criteria for sudden tripping.

[0102] Variable-speed pumped-storage units typically include 10 operating states: stationary, start-up, no-load, power generation, power generation phase adjustment, pumping, pumping phase adjustment, pumping self-start, regenerative braking, and shutdown. Since the excitation circuit breaker can only trip unexpectedly when the unit is in an operating state that requires the excitation system to operate (i.e., the target state), this invention first determines whether the unit is currently in any of the multiple possible target states through various methods.

[0103] In one embodiment of the present invention, the operating status of the unit can be determined by reading information from the monitoring system of the variable speed pumped storage unit. Multiple preset target states include: no load, power generation, power generation phase adjustment, pumping, pumping phase adjustment, pumping self-start and regenerative braking. Subsequent fault identification is performed only when the unit is currently operating in any of the above multiple target states.

[0104] Furthermore, when it is determined that the unit is currently in any operating state that requires the excitation system to work, the fault detection criteria for sudden tripping are applied. Based on the average difference of the effective value of the line voltage, the average difference of the line voltage phase, and the duration of the abnormality, it is determined whether the excitation circuit breaker has experienced a sudden tripping fault.

[0105] In one embodiment of the present invention, determining whether the excitation circuit breaker has experienced a sudden tripping fault includes: if the average difference of the effective value of the line voltage and the average difference of the phase of the line voltage are respectively greater than the corresponding difference threshold, recording the abnormal duration of the difference threshold; if the abnormal duration is greater than the time threshold, determining that the excitation circuit breaker has experienced a sudden tripping fault.

[0106] Specifically, the fault detection criterion for the unauthorized jump in this embodiment is shown in the following formula:

[0107]

[0108] in, It is the voltage difference threshold. It is the phase difference threshold. It is a time threshold.

[0109] Among them, Greater than and Furthermore, the duration for which the above two differences exceed the corresponding difference thresholds (i.e., the abnormal duration) exceeds [a certain value]. Subsequently, it was determined that an ECB jump had occurred. This invention, by adding criteria such as abnormal duration, can avoid misjudgments caused by unexpected factors.

[0110] Furthermore, after determining that the excitation circuit breaker has tripped unexpectedly, this embodiment also includes controlling the variable-speed pumped-storage unit to perform the trip protection action. Specifically, if it is determined that the ECB has tripped unexpectedly, then a protection action is performed, such as triggering an emergency shutdown operation.

[0111] It is understandable that, since this invention uses the difference in line voltage as the criterion, the trip protection will not malfunction when a short circuit or other type of fault occurs in the unit's excitation system.

[0112] To more fully illustrate the effectiveness of the discrimination method of the present invention in practical applications, a specific embodiment is described below. This embodiment involves performing ECB (Electronic Control Board) trip detection on a doubly-fed variable-speed pumped storage unit. The parameters of this unit are shown in Table 1 below:

[0113] Table 1 Parameter Table of Doubly Fed Variable Speed ​​Pumped Storage Unit

[0114] project parameter project parameter Rated capacity 336MVA Synchronous speed 428.6 rpm Stator rated voltage of generator motor 15.75kV Inverter capacity 42MVA The rated voltage of the low-voltage side of the excitation transformer 4.5kV Excitation transformer short-circuit voltage percentage 18% Grid-side switching frequency 1000Hz DC bus voltage 7.5kV

[0115] In this embodiment, the stator rated line voltage is set. , Desirable Take here , The protection criterion is delayed for .

[0116] Then, an ECB trip fault was set up under generator operation. Before the fault, the active power command was 0.4 pu, the reactive power command was 0 p.u., the grid-side inverter adopted DC voltage and current dual closed-loop control based on d-axis grid voltage orientation, the DC voltage command was 7.5 kV, and the grid-side reactive power command was 0. At the time of the fault... .

[0117] Under the above conditions, the method for detecting unauthorized tripping of the excitation circuit breaker in a variable-speed pumped-storage unit, as described in this invention, performs relevant data calculations and fault identification. The specific implementation process can be referred to the relevant descriptions in the above embodiments, and will not be repeated here. Through calculation, the changing relationships of the voltage difference and phase difference can be calculated as follows: Figure 5 and Figure 6 As shown.

[0118] Depend on Figure 5 and Figure 6 It can be seen that under the subsynchronous power generation condition, the calculated effective value of the voltage on the high-voltage side of the excitation transformer has a brief spike at the moment of ECB tripping, exceeding the threshold value; subsequently, due to the rapid drop in DC voltage, the voltage on the high-voltage side of the excitation transformer also drops rapidly, and the voltage difference widens rapidly, exceeding the threshold value again. Because the grid-side frequency converter loses its orientation and experiences large phase fluctuations, the averaged value exceeds the threshold value. The tripping protection operates at 5.24 seconds.

[0119] Therefore, the present invention can quickly and accurately identify the tripping fault of the excitation circuit breaker and can quickly provide protection against the tripping fault.

[0120] To achieve the above embodiments, the present invention also proposes a detection system for the unauthorized tripping of the excitation circuit breaker in a variable-speed pumped-storage unit. Figure 7 This is a schematic diagram of a system for detecting the unauthorized tripping of the excitation circuit breaker in a variable-speed pumped-storage unit, as proposed in an embodiment of the present invention. The system includes: a data acquisition module 100, a first calculation module 200, a second calculation module 300, and a detection module 400.

[0121] Among them, the acquisition module 100 is used to acquire the three-phase voltage on the high-voltage side of the excitation transformer, the three-phase voltage on the low-voltage side of the main transformer, and the three-phase current on the high-voltage side of the excitation transformer of the variable speed pumped storage unit.

[0122] The first calculation module 200 is used to compensate the three-phase voltage on the high-voltage side based on the parameters of the current-limiting reactor and the three-phase current, and to calculate the three-phase line voltage on the high-voltage side of the excitation transformer and the three-phase line voltage on the low-voltage side of the main transformer based on the compensated three-phase voltage on the high-voltage side and the three-phase voltage on the low-voltage side.

[0123] The second calculation module 300 is used to calculate the average difference of the effective value of the line voltage and the average difference of the line voltage phase of the variable speed pumped storage unit based on the three-phase line voltage on the high-voltage side, the three-phase line voltage on the low-voltage side, and the power frequency cycle.

[0124] The discrimination module 400 is used to determine the current operating status of the variable speed pumped storage unit. When the current operating status is any of the multiple target states, it determines whether the excitation circuit breaker has experienced a tripping fault based on the average difference of the effective value of the line voltage, the average difference of the phase of the line voltage, and the duration of the abnormality.

[0125] In one embodiment of the present invention, the system further includes a protection module, which controls the variable speed pumped storage unit to perform a trip protection action after determining that the excitation circuit breaker has tripped unexpectedly.

[0126] It should be noted that the explanation of the aforementioned embodiment of the method for detecting the unauthorized tripping of the excitation circuit breaker in a variable-speed pumped-storage unit also applies to the system of this embodiment, and will not be repeated here.

[0127] In summary, the detection system for unauthorized tripping of the excitation circuit breaker (ECB) in variable-speed pumped-storage units according to the embodiments of the present invention improves the accuracy, convenience, and reliability of ECB unauthorized tripping detection, which is conducive to ensuring the safe and stable operation of variable-speed pumped-storage units.

[0128] To implement the above embodiments, the present invention also proposes an electronic device, which includes: a processor; a memory for storing processor-executable instructions; wherein the processor is configured to execute instructions to implement the method for detecting unauthorized tripping of the excitation circuit breaker of a variable-speed pumped-storage unit as described in any of the first aspect embodiments above.

[0129] To implement the above embodiments, the present invention also proposes a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the method for detecting unauthorized tripping of the excitation circuit breaker of a variable-speed pumped-storage unit as described in any of the first aspect embodiments above.

[0130] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0131] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0132] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing custom logic functions or processes, and the scope of preferred embodiments of the invention includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as should be understood by those skilled in the art to which embodiments of the invention pertain.

[0133] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Alternatively, the computer-readable medium may be paper or other suitable media on which the program can be printed, since the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in a computer memory.

[0134] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware as in another embodiment, it can be implemented using any of the following techniques known in the art, or a combination thereof: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0135] Those skilled in the art will understand that all or part of the steps of the methods described in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, it includes one or a combination of the steps of the method embodiments.

[0136] Furthermore, the functional units in the various embodiments of the present invention can be integrated into a processing module, or each unit can exist physically separately, or two or more units can be integrated into a module. The integrated module can be implemented in hardware or as a software functional module. If the integrated module is implemented as a software functional module and sold or used as an independent product, it can also be stored in a computer-readable storage medium.

[0137] The storage medium mentioned above can be a read-only memory, a disk, or an optical disk, etc. Although embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for detecting unauthorized tripping of excitation circuit breakers in variable-speed pumped-storage units, characterized in that: include, Collect the three-phase voltage on the high-voltage side of the excitation transformer, the three-phase voltage on the low-voltage side of the main transformer, and the three-phase current on the high-voltage side of the excitation transformer of the variable-speed pumped-storage unit; Based on the high-voltage side three-phase current, the high-voltage side three-phase voltage is compensated, and based on the compensated high-voltage side three-phase voltage and the low-voltage side three-phase voltage, the high-voltage side three-phase line voltage of the excitation transformer and the low-voltage side three-phase line voltage of the main transformer are calculated respectively. Based on the three-phase line voltage on the high-voltage side, the three-phase line voltage on the low-voltage side, and the power frequency cycle, calculate the average difference of the effective value of the line voltage and the average difference of the line voltage phase of the variable speed pumped storage unit. The current operating state of the variable-speed pumped-storage unit is determined. If the current operating state is any of the multiple target states, the excitation circuit breaker is determined to have experienced a tripping fault based on the average difference of the effective value of the line voltage and the average difference of the phase of the line voltage.

2. The method as described in claim 1, characterized in that: The system collects the three-phase voltage on the high-voltage side of the excitation transformer, the three-phase voltage on the low-voltage side of the main transformer, and the three-phase current on the high-voltage side of the excitation transformer of the variable-speed pumped-storage unit, including... The three-phase voltage on the high-voltage side of the excitation transformer is collected through the voltage transformer on the high-voltage side of the excitation transformer. The three-phase voltage on the low-voltage side of the main transformer is collected through the voltage transformer on the low-voltage side of the main transformer. The three-phase current on the high-voltage side of the excitation transformer is collected through the current transformer between the high-voltage side of the excitation transformer and the excitation circuit breaker.

3. The method as described in claim 1, characterized in that: Based on the three-phase current on the high-voltage side, compensation is performed on the three-phase voltage on the high-voltage side, including: A current-limiting reactor is installed between the low-voltage side of the main transformer and the excitation circuit breaker, and the inductance of the current-limiting reactor is obtained. Based on the inductance and the three-phase current, the compensated high-voltage side three-phase voltage is calculated using the following formula. ， Where L is the inductance of the current-limiting reactor. It is the three-phase current on the high-voltage side of the excitation transformer. It is the three-phase voltage on the high-voltage side of the excitation transformer.

4. The method as described in claim 1, characterized in that: Calculate the average difference of the effective value of the line voltage and the average difference of the line voltage phase of the variable-speed pumped-storage unit, including: Calculate the average effective value of the three-phase line voltage on the high-voltage side of the excitation transformer based on the three-phase line voltage on the high-voltage side and the power frequency period; Calculate the average effective value of the three-phase line voltage on the low-voltage side of the main transformer based on the three-phase line voltage on the low-voltage side and the power frequency period; The first phase of the AB phase line voltage on the high-voltage side of the excitation transformer and the second phase of the AB phase line voltage on the low-voltage side of the main transformer are calculated using a PLL phase-locked loop. The effective value difference of the line voltage is calculated based on the average effective value of the three-phase line voltage on the high-voltage side and the average effective value of the three-phase line voltage on the low-voltage side, and the phase difference of the line voltage is calculated based on the first phase and the second phase. The window length of the moving average algorithm is set using the power frequency period. The moving average algorithm is then used to process the effective value difference of the line voltage and the phase difference of the line voltage to obtain the average difference of the effective value of the line voltage and the average difference of the phase difference of the line voltage.

5. The method as described in claim 1, characterized in that: Determining whether the excitation circuit breaker has experienced a sudden tripping fault includes: If the average difference of the effective value of the line voltage and the average difference of the phase of the line voltage are both greater than the corresponding difference threshold, the abnormal duration exceeding the difference threshold is recorded. If the duration of the abnormality exceeds a time threshold, it is determined that the excitation circuit breaker has experienced a sudden tripping fault. After determining that the excitation circuit breaker has experienced a sudden tripping fault, it also includes, Control the variable-speed pumped storage unit to perform the trip protection action.

6. The method as described in claim 5, characterized in that: The multiple target states include no-load, power generation, power generation phase adjustment, pumping, pumping phase adjustment, pumping self-start, and regenerative braking.

7. A detection system for unauthorized tripping of excitation circuit breakers in variable-speed pumped-storage units, characterized in that: include, The data acquisition module is configured to acquire the three-phase voltage on the high-voltage side of the excitation transformer, the three-phase voltage on the low-voltage side of the main transformer, and the three-phase current on the high-voltage side of the excitation transformer of the variable-speed pumped-storage unit. The first calculation module is configured to compensate the three-phase voltage on the high-voltage side based on the three-phase current on the high-voltage side, and calculate the three-phase line voltage on the high-voltage side of the excitation transformer and the three-phase line voltage on the low-voltage side of the main transformer based on the compensated three-phase voltage on the high-voltage side and the three-phase voltage on the low-voltage side, respectively. The second calculation module is configured to calculate the average difference of the effective value of the line voltage and the average difference of the line voltage phase of the variable speed pumped storage unit based on the three-phase line voltage on the high-voltage side, the three-phase line voltage on the low-voltage side, and the power frequency cycle. as well as, The discrimination module is configured to determine the current operating state of the variable speed pumped storage unit, and if the current operating state is any of a plurality of target states, to determine whether the excitation circuit breaker has experienced a tripping fault based on the average difference of the effective value of the line voltage and the average difference of the phase of the line voltage.

8. The system as described in claim 7, characterized in that: It also includes, The protection module is configured to control the variable-speed pumped-storage unit to perform a trip protection action after determining that the excitation circuit breaker has tripped unexpectedly.

9. An electronic device, characterized in that: include, processor; Memory used to store the processor's executable instructions; The processor is configured to execute the instructions to implement the method for detecting unauthorized tripping of the excitation circuit breaker in a variable-speed pumped-storage unit as described in any one of claims 1 to 6.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by the processor, it implements a method for detecting the unauthorized tripping of the excitation circuit breaker in a variable-speed pumped-storage unit as described in any one of claims 1 to 6.

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