A 10kV-35kV high and low voltage crossing test device

Abstract

The utility model relates to a power test device field especially relates to a 10kV 35kV high low voltage crossing test device. Technical scheme is as follows: a 10kV 35kV high low voltage crossing test device, including main control circuit, transformer branch, low crossing branch 1, low crossing branch 2, high crossing branch and auxiliary circuit: wiring bushing XT1, circuit breaker CB1, current transformer CT1, voltage transformer PT1, disconnecting switch CB6, electric reactor Xs, disconnecting switch CB9, voltage transformer PT2, current transformer CT2, circuit breaker CB3, wiring bushing XT2 are connected in series in proper order, and circuit breaker CB2 is parallelly connected to the both ends of electric reactor Xs, transformer branch: disconnecting switch CB7 and three-phase step-up transformer T1, disconnecting switch CB8 are connected in series in proper order, and form first parallel branch, and disconnecting switch CB10 and single-phase step-down transformer T2, T3, T4 and disconnecting switch CB11 are connected in series in proper order, and form second parallel branch. Realized the high precision, full scene test of high low voltage crossing ability to new energy grid-connected equipment.

Description

Technical Field

[0001] This utility model relates to the field of power testing equipment, and in particular to a 10kV-35kV high and low voltage ride-through testing device. Background Technology

[0002] Due to various factors affecting the power grid, local short circuits or sudden voltage drops or rises caused by the start-up and shutdown of heavy loads can occur. The proportion of new energy sources such as wind and solar power is increasing, and their power generation is significantly affected by climate and weather, making it difficult to guarantee transient stability in power generation and consumption. We know that power systems require supply and demand to be consistent, with power consumption equal to power generation. Once this balance is disrupted, it can lead to power quality deterioration, causing frequency and voltage instability, or even power outages. To improve the operational safety of the power system and prevent the disconnection of large-scale new energy power plants during grid transient faults, thus avoiding major accidents such as large-scale power outages, inverters for photovoltaic and wind power plants must meet relevant national standards for high and low voltage ride-through before being allowed to be installed and connected to the grid. This utility model provides a 10kV / 35kV high and low voltage ride-through test device, offering an effective method for testing the high and low voltage ride-through capability of new energy power generation connected to the grid.

[0003] The electricity generated by large-scale photovoltaic power plants, large-scale wind turbines, or electrochemical energy storage systems must be transmitted through the national power grid to reach users. When a grid fault or disturbance causes a voltage rise, the ability of these systems to maintain continuous operation without disconnecting from the grid within a certain voltage rise range and time interval is called high-voltage ride-through capability. Conversely, when a grid fault or disturbance causes a voltage drop, the ability of these systems to maintain continuous operation without disconnecting from the grid within a certain voltage drop range and time interval is called low-voltage ride-through capability. To ensure reliable transmission of electricity generated by large-scale photovoltaic power plants, large-scale wind turbines, or electrochemical energy storage systems, it is necessary to develop a testing device that generates fault voltages that meet testing requirements at the grid connection test point—namely, a 10kV / 35kV high and low voltage ride-through test device. Utility Model Content

[0004] This invention proposes a 10kV-35kV high and low voltage ride-through test device, which solves the problem that the existing technology lacks an integrated test device that can be compatible with different voltage levels and accurately simulate grid voltage drop and rise faults, thus failing to meet the high and low voltage ride-through capability test requirements of new energy grid-connected equipment.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by this utility model is as follows:

[0006] A 10kV-35kV high and low voltage ride-through test device, comprising:

[0007] Main control circuit: Bushing XT1, circuit breaker CB1, current transformer CT1, voltage transformer PT1, disconnector CB6, reactor Xs, disconnector CB9, voltage transformer PT2, current transformer CT2, circuit breaker CB3, and bushing XT2 are connected in series in sequence, and circuit breaker CB2 is connected in parallel to both ends of reactor Xs.

[0008] Transformer branch: Disconnector CB7 is connected in series with three-phase step-up transformer T1 and disconnector CB8 to form the first parallel branch; disconnector CB10 is connected in series with single-phase step-down transformers T2, T3, T4 and disconnector CB11 to form the second parallel branch; the first parallel branch is connected in parallel across disconnector CB6, and the second parallel branch is connected in parallel across circuit breaker CB9;

[0009] Low-passage branch 1: Current transformer CT3-1, contactor CB4-1, contactor QL, adjustable reactor Xp1, and contactor QN1 are connected in series. Contactor QN1 is grounded. Current transformer CT3-1 is connected to the node between circuit breaker CB2 and disconnector CB9.

[0010] Low-passage branch 2: Current transformer CT3-2, contactor CB4-2 and fixed reactor Xp2 are connected in series. Current transformer CT3-2 is connected to the node between circuit breaker CB2 and disconnector CB9. Low-passage branch 2 is connected in parallel with low-passage branch 1.

[0011] High-pass branch: Current transformer CT4, contactor CB5, contactor QC, capacitor CL, resistor Rd, and contactor QN2 are connected in series. Contactor QN2 is grounded. Current transformer CT4 is connected to the node between circuit breaker CB2 and disconnector CB9. The high-pass branch is connected in parallel with low-pass branch 2.

[0012] Auxiliary circuit: The first end of contactor CB12 is connected to the node between disconnector CB6 and reactor Xs, and the second end of contactor CB12 is connected to the node between contactor CB4-1 and contactor QL; the first end of contactor CB13 is connected to the node between disconnector CB6 and reactor Xs, and the second end of contactor CB13 is connected to the node between contactor CB5 and contactor QC.

[0013] Furthermore, the reactor Xs is composed of five independent reactors Xs1 to Xs5 connected in series. Each of the five independent reactors Xs1 to Xs5 is connected in parallel with a single-phase contactor QS1 to QS5. The reactance values ​​of the five independent reactors Xs1 to Xs5 are designed in a ratio of 16:8:4:2:1.

[0014] Furthermore, the adjustable reactor Xp1 is composed of five independent reactors Xp11 to Xp15 connected in series. Each of the five independent reactors Xp11 to Xp15 is connected in parallel with contactors QP11 to QP15. The reactance values ​​of the five independent reactors Xp11 to Xp15 are designed in a ratio of 16:8:4:2:1.

[0015] Furthermore, each phase of capacitor CL consists of six independent capacitors C1 to C6 connected in parallel. Each capacitor is connected in series with a single-phase contactor to control its on / off state. The six unidirectional contactors are QC1 to QC6. The capacitance values ​​of the six capacitors C1 to C6 are designed in a ratio of 32:16:8:4:2:1.

[0016] Furthermore, contactor QL is composed of three independent single-phase contactors QL1 to QL3 connected in parallel, used to select the conduction phase sequence of the low-voltage branch 1; contactor QC is composed of three independent single-phase contactors QC1 to QC3 connected in parallel, used to select the conduction phase sequence of the high-voltage branch.

[0017] Furthermore, contactor QN1 is connected in series in the neutral circuit of the low-voltage branch 1, and contactor QN2 is connected in series in the neutral circuit of the high-voltage branch.

[0018] Furthermore, the three-phase step-up transformer T1 has a turns ratio of 10kV / 35kV, while the single-phase step-down transformers T2, T3, and T4 have an input voltage compatible with 35kV and an output voltage compatible with 10kV.

[0019] Furthermore, all contactors (QL1~QL3, QC1~QC3, QS1~QS5, QP11~QP15) are fast contactors with opening and closing times ≤20ms.

[0020] Furthermore, the impedance value of the fixed reactor Xp2 is set to 20% of the maximum impedance value of the reactor Xs.

[0021] Furthermore, the resistor Rd is an adjustable resistor, with each phase consisting of two independent resistors R1 to R2, and three resistance values ​​can be adjusted through a combination of contactors.

[0022] Furthermore, the continuous voltage ride-through function of the high and low voltage ride-through test device is achieved through multi-branch coordinated switching:

[0023] Continuous low voltage ride-through: After a voltage drop is generated by the current-limiting impedance Xs, low-voltage ride-through branch 1 and low-voltage ride-through branch 2, a voltage drop can be generated again by controlling the fast contactor.

[0024] Low-high continuous crossing: During the period when the low voltage state is maintained in the low crossing branch, the overvoltage state is generated by switching to the high crossing branch through a fast contactor;

[0025] The contactor's opening and closing action time is significantly shorter than the voltage state duration, ensuring no current interruption during state transition.

[0026] The positive effects of this invention are as follows: This high and low voltage ride-through test device, through a main control circuit and a multi-branch collaborative architecture, achieves high-precision, full-scenario testing of the high and low voltage ride-through capabilities of new energy grid-connected equipment. Its core value lies in:

[0027] With intelligent voltage level compatibility, it adopts a parallel transformer group structure (a combination of three-phase step-up transformers and single-phase step-down transformers). A single device can cover the testing needs of different voltage levels (such as 10kV / 35kV), completely solving the problem of needing to configure multiple devices due to voltage level differences in traditional solutions, greatly improving testing efficiency and reducing hardware costs.

[0028] The fault simulation features refined control based on a binary adjustable component design (multi-stage segmented combination of reactors and capacitors), coupled with a phase sequence selection contactor group, enabling the generation of arbitrary single-phase / multi-phase voltage dip or rise waveforms at test points. Its continuous impedance and capacitive reactance adjustment capabilities ensure that voltage fluctuations cover the entire spectrum of fault scenarios, from zero breakdown to deep voltage drop and overvoltage, accurately matching the stringent test curves required by national standards.

[0029] Dynamic response and continuous fault-crossing capability are achieved through a rapid-closing contactor group and a dual low-voltage bypass branch coordination mechanism, enabling millisecond-level fault waveform switching. The seamless relay between the low-voltage and high-voltage bypass branches can generate continuous low-to-high voltage transient waveforms, realistically simulating the transient disturbance process of the power grid and effectively verifying the uninterrupted operation capability of new energy equipment under complex faults.

[0030] To ensure safety and stability during testing, the reactive power compensation design of the auxiliary circuit (such as boost resistor-capacitor to support grid voltage and short-circuit impedance to suppress overshoot) combined with the graded protection of the current-limiting reactor maintains the stability of the main grid voltage while creating voltage faults at the test point, avoiding real grid fluctuations during the test process and ensuring that the test process is safe and controllable. Attached Figure Description

[0031] Figure 1 This is the overall electrical schematic diagram of this utility model;

[0032] Figure 2 This is a diagram of the reactor Xs (Xs1~Xs5) and the switch combination in this utility model;

[0033] Figure 3 This is a diagram showing the parallel reactor Xp1 (Xp11~Xp15) and the switch combination in this utility model;

[0034] Figure 4 This is a diagram of the parallel capacitors CL (C1~C6) and the switch combination method in this utility model;

[0035] Figure 5 The continuous low voltage ride-through waveform diagram satisfied by this utility model;

[0036] Figure 6 This utility model satisfies the continuous low-high voltage ride-through waveform diagram. Detailed Implementation

[0037] The technical solutions of this utility model will be clearly and completely described below with reference to the embodiments of this utility model. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this utility model.

[0038] A 10kV-35kV high and low voltage ride-through test device, comprising:

[0039] Main control circuit: Bushing XT1, circuit breaker CB1, current transformer CT1, voltage transformer PT1, disconnector CB6, reactor Xs, disconnector CB9, voltage transformer PT2, current transformer CT2, circuit breaker CB3, and bushing XT2 are connected in series in sequence, and circuit breaker CB2 is connected in parallel to both ends of reactor Xs.

[0040] Transformer branch: Disconnector CB7 is connected in series with three-phase step-up transformer T1 and disconnector CB8 to form the first parallel branch; disconnector CB10 is connected in series with single-phase step-down transformers T2, T3, T4 and disconnector CB11 to form the second parallel branch; the first parallel branch is connected in parallel across disconnector CB6, and the second parallel branch is connected in parallel across circuit breaker CB9;

[0041] Low-passage branch 1: Current transformer CT3-1, contactor CB4-1, contactor QL, adjustable reactor Xp1, and contactor QN1 are connected in series. Contactor QN1 is grounded. Current transformer CT3-1 is connected to the node between circuit breaker CB2 and disconnector CB9.

[0042] Low-passage branch 2: Current transformer CT3-2, contactor CB4-2 and fixed reactor Xp2 are connected in series. Current transformer CT3-2 is connected to the node between circuit breaker CB2 and disconnector CB9. Low-passage branch 2 is connected in parallel with low-passage branch 1.

[0043] High-pass branch: Current transformer CT4, contactor CB5, contactor QC, capacitor CL, resistor Rd, and contactor QN2 are connected in series. Contactor QN2 is grounded. Current transformer CT4 is connected to the node between circuit breaker CB2 and disconnector CB9. The high-pass branch is connected in parallel with low-pass branch 2.

[0044] Auxiliary circuit: The first end of contactor CB12 is connected to the node between disconnector CB6 and reactor Xs, and the second end of contactor CB12 is connected to the node between contactor CB4-1 and contactor QL; the first end of contactor CB13 is connected to the node between disconnector CB6 and reactor Xs, and the second end of contactor CB13 is connected to the node between contactor CB5 and contactor QC.

[0045] The schematic diagram of the 10kV-35kV high and low voltage ride-through test device is as follows: Figure 1 As shown; including the main control circuit, transformer branch, low-voltage branch 1, low-voltage branch 2, high-voltage branch, and auxiliary circuit.

[0046] The main control circuit includes bushing XT1, circuit breaker CB1, current transformer CT1, voltage transformer PT1, disconnector CB6, reactor Xs, circuit breaker CB2, disconnector CB9, current transformer CT2, voltage transformer PT2, circuit breaker CB3, bushing XT2, disconnector CB7, transformer T1, disconnector CB8, disconnector CB10, transformers T2, T3, T4, and disconnector CB11; low-voltage branch 1 includes current transformer CT3-1, contactor CB4-1, contactor QL, reactor Xp1, and contactor QN1; low-voltage branch 2 includes current transformer CT3-2, contactor CB4-2, and reactor Xp2; high-voltage branch includes current transformer CT4, contactor CB5, contactor QC, capacitor CL, resistor Rd, contactor QN2, contactor CB12, and contactor CB13.

[0047] The XT1 bushing is connected to the external power grid. Using a bushing can greatly reduce the space required for voltage insulation and reduce the size of the equipment. The CB1 circuit breaker is a three-phase circuit breaker used to control the connection and disconnection with the external power grid.

[0048] The current transformer CT1 is a high-precision current transformer connected in series in the main circuit; the voltage transformer PT1 is a high-precision voltage transformer connected in parallel in the main circuit; both provide current and voltage signals for the measurement and control circuits.

[0049] Circuit breaker CB2 is connected in parallel across reactor Xs; circuit breaker CB2 is a three-phase circuit breaker. Series reactor Xs is an adjustable reactor, such as... Figure 2As shown, each phase of reactor Xs consists of reactors Xs1 to Xs5. Each reactor Xs1 to Xs5 is connected in parallel with contactors QS1 to QS5. Contactors QS1 to QS5 are single-phase contactors that can remotely control the reactors to be put into or taken out of operation, forming different combinations. Theoretically, 32 impedance values ​​can be achieved.

[0050] Reactors Xs1 to Xs5 are designed with reactance values ​​of 16:8:4:2:1;

[0051] The current transformer CT2 is a high-precision current transformer connected in series in the main circuit; the voltage transformer PT2 is a high-precision voltage transformer connected in parallel in the main circuit; both provide current and voltage signals for the measurement and control circuits.

[0052] The XT2 bushing connects to the test point; the CB3 circuit breaker is a three-phase circuit breaker used for controlling the connection and disconnection of the test point.

[0053] Disconnector CB7, transformer T1, and disconnector CB8 are connected in series; transformer T1 is a three-phase step-up transformer with a turns ratio of 10 / 35.

[0054] The disconnecting switch CB10, transformers T2, T3, and T4, and disconnecting switch CB11 are connected in series. Transformers T2, T3, and T4 are single-phase step-down transformers. The use of three single-phase transformers solves the problem of electromagnetic imbalance during two-phase or single-phase testing. The use of the three-phase step-up transformer T1 and the three single-phase step-down transformers T2, T3, and T4 enables this invention to achieve 35kV and 10.5kV compatible testing of the tested object, thus broadening the application range of the device. The functions of the original 10kV and 35kV testing devices are combined into one testing device, greatly reducing the equipment size and cost.

[0055] Current transformers CT3-1 and CT3-2 are high-precision current transformers connected in series in the low-voltage branch; they provide current and voltage signals for the measurement and control circuits.

[0056] Contactor CB4-1 is a three-phase contactor used to control the connection or disconnection of low-voltage branch 1;

[0057] Reactor Xp1 is an adjustable reactor, such as... Figure 3As shown, each phase of the parallel reactor Xp1 consists of five reactors, Xp11 to Xp15. Each reactor Xp11 to Xp15 is connected in parallel with a corresponding contactor QP11 to QP15. Contactors QP11 to QP15 are single-phase contactors used to control the connection or disconnection of Xp11 to Xp15. The reactance values ​​of reactors Xp11 to Xp15 are designed according to 16:8:4:2:1. The reactors can be remotely controlled to be put into or taken out of operation, forming different combinations. Theoretically, 32 impedance values ​​can be achieved. Contactor CB4-2 is a three-phase contactor used to control the connection or disconnection of the low-voltage branch 2. Reactor Xp2 is a fixed reactor.

[0058] Reactor ratio: The reactance values ​​of Xp11 to Xp15 are designed according to 16:8:4:2:1, and the total reactance value is Xp=16k+8k+4k+2k+1k=31k (k is the proportional coefficient).

[0059] Function of parallel contactors: A single-phase contactor (QS11~QS15) is connected in parallel across the two ends of each reactor. When the contactor is closed, the corresponding reactor is short-circuited, and the reactance value is removed from the total reactance.

[0060] Binary encoding adjustment

[0061] Equivalent binary bits: The ratio 16:8:4:2:1 corresponds to binary bit weights (2 4 :2 3 :2 2 :2 1 :2 0 The 0 to 31k integer multiple adjustment is achieved by combining the on and off states of the contactor.

[0062] Adjustable step size: The minimum step size is 1k (Xp15), which can cover all integer reactance values; for example:

[0063] Requires 5k: Close QS11, QS12, QS13 (31k-16-8-4=3k, combination needs to be adjusted);

[0064] 10k is required: Close QS11, QS13, QS15 (31k-16-4-1=10k);

[0065] Non-integer adjustment: If more precise adjustment (e.g., 0.5k) is required, a smaller ratio reactor can be added (e.g., Xp16 = 0.5k), but the current ratio already covers 32 levels of integer adjustment.

[0066] The PLC controls the contactor to switch quickly, ensuring the required response speed and power factor.

[0067] By using a 16:8:4:2:1 proportional design and combining it with contactor binary control, 32 levels of fine reactance adjustment (step size 1k) are achieved, meeting the requirements of converter devices for harmonic suppression and dynamic response.

[0068] The adjustment of the reactance values ​​of reactors Xs1 to Xs5 is similar.

[0069] The contactor QL consists of three single-phase contactors, QL1 to QL3, used for phase sequence selection;

[0070] Contactor QN1 is a neutral line selection switch that controls the connection or disconnection of the grounding of the low-voltage branch 1.

[0071] By combining QL1 to QL3 and QN1, any single-phase, two-phase, and three-phase voltage drop / rise required by the test point can be achieved;

[0072] The series reactors (current-limiting reactors) Xs (Xs1~Xs5) and the switch combination form 32 impedance values, and the parallel reactors (short-circuit reactors) Xp1 (Xp11~Xp15) and the switch combination form 32 impedance values. Combined, they can form 32×32, a total of 1024 combinations. In this way, very precise voltage drop values ​​within the range of 0-90% can be generated for low voltage ride-through testing; the low-through branch 2, in conjunction with the series reactor, generates zero-through and 20% low-through.

[0073] The CT4 current transformer is a high-precision current transformer connected in series in the high-voltage branch; it provides current and voltage signals for the measurement and control circuits.

[0074] Contactor CB5 is a three-phase contactor used to control the connection or disconnection of high-voltage branches;

[0075] Capacitor CL is an adjustable capacitor, such as... Figure 4 As shown, each phase of capacitor CL consists of 6 capacitors, C1 to C6, and each capacitor C1 to C6 is controlled by a corresponding single-phase contactor. The capacitors C1 to C6 can be remotely controlled to be engaged or disengaged, forming different combinations, theoretically achieving 63 different capacitance values.

[0076] The capacitance values ​​of capacitors C1 to C6 are designed according to a ratio of 32:16:8:4:2:1;

[0077] Capacitor ratio: The capacitor values ​​of C1 to C6 are designed according to 32:16:8:4:2:1, and the total capacitance value is C_total=32k+16k+8k+4k+2k+1k=63k (k is the proportionality coefficient).

[0078] Parallel switch function: An electronic switch (such as a MOSFET or relay) is connected in parallel across each capacitor. When the switch is closed, the corresponding capacitor is short-circuited, and the capacitance value is removed from the total capacitance.

[0079] Binary encoding adjustment

[0080] Equivalent binary bits: The ratio 32:16:8:4:2:1 corresponds to binary bit weights (2 5 :2 4 :2 3 :2 2 :2 1 :2 0 The 0 to 63k integer multiple adjustment is achieved through the combination of on and off switches.

[0081] Adjustable step size: The minimum step size is 1k (C6), which can cover all integer capacitance values. For example:

[0082] 5k is required: Close C1, C2, C3, C4 (63k-32-16-8-4=3k, the combination needs to be adjusted).

[0083] 10k is needed: Close C1, C2, C4, C5 (63k-32-16-4-2=9k, the combination needs to be adjusted).

[0084] Non-integer adjustment: For finer adjustment (e.g., 0.5k), a smaller capacitor can be added (e.g., C7 = 0.5k), but the current ratio already covers 64 levels of integer adjustment.

[0085] The digitally adjustable capacitor circuit uses a DAC to control the switch for rapid switching, ensuring response speed and accuracy.

[0086] By employing a 32:16:8:4:2:1 proportional design and combining it with binary switch control, 64 levels of fine capacitor adjustment (1k step) are achieved to meet the precise capacitance value requirements of power systems or analog circuits.

[0087] The resistor Rd is an adjustable resistor. Each phase consists of two resistors, R1 and R2. R1 and R2 are controlled by corresponding contactors to form different combinations. Theoretically, three resistance values ​​can be achieved.

[0088] The contactor QC consists of three single-phase contactors, QC1 to QC3, used for phase sequence selection. They control the connection or disconnection of the capacitors and resistors in each of phases A, B, and C, respectively. They can control the connection of three-phase or two-phase resistors and capacitors to achieve the required voltage increase at the test point.

[0089] Contactor QN2 controls the connection or disconnection of the N-phase circuit of the high-voltage branch.

[0090] The current-limiting impedance Xs mentioned above has 32 combinations, the capacitor CL has 64 combinations, and the resistor Rd has 3 combinations. All three of L, C, and R are adjustable, and theoretically, a total of 6048 combinations (32×63×3) can be generated. As needed, different voltage values ​​can be generated at the test point to test the high voltage ride-through capability of the system under test.

[0091] like Figure 1 As shown, during low voltage ride-through, contactors CB12 and CB5 are open, contactor CB13 is closed, and boost resistors Rd and CL are connected to the grid. The boost resistors Rd and CL provide reactive power compensation to support the grid voltage.

[0092] When high voltage ride-through occurs, contactors CB4-1 and CB4-2 are disconnected, contactor CB12 is closed, and short-circuit impedance Xp1 is connected to the grid terminal. Reactive power compensation is provided by short-circuit impedance Xp1 to support the grid voltage.

[0093] 1. Low Voltage Ride

[0094] like Figure 1 As shown, when the external power grid is 35kV, set the current-limiting impedance Xs and short-circuit impedances Xp1 and Xp2 as needed, disconnect disconnect switches CB7, CB8, CB10, and CB11, close disconnect switches CB6 and CB9, and close circuit breakers CB3 and CB1. When the unit is in grid-connected operation, the low-voltage ride-through test can be performed according to the following steps:

[0095] a) Disconnect the bypass contactor CB2 and connect the current-limiting impedance Xs;

[0096] b) Disconnect contactors CB12 and CB5, close contactors QN2, QC and CB13, connect the boost resistor and capacitor Rd and CL to the grid terminal, close short-circuit contactors QN1, CL, CB4-1 and CB4-2, connect short-circuit impedances Xp1 and Xp2, and generate a voltage drop at the test point.

[0097] c) Disconnect short-circuit contactors CB4-1 and CB4-2 to disconnect short-circuit impedances Xp1 and Xp2; disconnect contactor CB13 to disconnect the reactive power compensation provided by boost resistor-capacitor Rd and CL.

[0098] d) Close the bypass contactor CB2, disconnect the current limiting impedance Xs, and the grid voltage returns to normal.

[0099] 2. High Voltage Ride

[0100] like Figure 1As shown, when the external power grid is 35kV, set the same current-limiting impedance Xs as the low-voltage ride-through test. Set the boost resistor and capacitor Rd and CL as needed. Disconnect disconnect switches CB7, CB8, CB10, and CB11, close disconnect switches CB6 and CB9, and close circuit breakers CB3 and CB1. When the unit is running in grid-connected mode, the high-voltage ride-through test can be performed according to the following steps:

[0101] a) Disconnect the bypass contactor CB2 and connect the current-limiting impedance Xs;

[0102] b) Disconnect contactors CB4-1, CB4-2, and CB13, close contactors QN1, CL, and CB12, connect short-circuit impedance Xp1 to the power grid, close short-circuit contactors QN2, QC, and CB5, and engage boost resistors Rd and CL to generate a voltage rise at the test point.

[0103] c) Disconnect short-circuit contactor CB5 to deactivate boost resistor-capacitor Rd and CL; disconnect contactor CB12 to deactivate reactive power compensation provided by short-circuit impedance Xp1.

[0104] d) Close the bypass contactor CB2, disconnect the current limiting impedance Xs, and the grid voltage returns to normal.

[0105] 3. Continuous crossing

[0106] The contactors of this utility model are all fast contactors with extremely short opening and closing times. The low-voltage pass-through branch 1 and the low-voltage pass-through branch 2 meet the requirements for continuous low-voltage pass-through. The low-voltage pass-through branch 1 or the low-voltage pass-through branch 2, in conjunction with the high-voltage pass-through branch, meets the requirements for low-to-high continuous voltage pass-through in the standard. Figure 5 The figure shown is a continuous low voltage ride-through waveform diagram that meets the requirements of this utility model; Figure 6 The figure shown is a waveform diagram of continuous low-high voltage ride-through that meets the requirements of this utility model.

[0107] The continuous voltage ride-through function of the high and low voltage ride-through test device is achieved through multi-branch coordinated switching:

[0108] Continuous low voltage ride-through: After a voltage drop is generated by the current-limiting impedance Xs, low-voltage ride-through branch 1 and low-voltage ride-through branch 2, a voltage drop can be generated again by controlling the fast contactor; and different levels of voltage drop can be generated.

[0109] Low-high continuous crossing: During the period when the low voltage state is maintained in the low crossing branch, the overvoltage state is generated by switching to the high crossing branch through a fast contactor;

[0110] The contactor's opening and closing action time is significantly shorter than the voltage state duration, ensuring no current interruption during state transition.

[0111] The contactors in this invention all adopt fast contactors with a switching time of ≤20ms, which lays the foundation for achieving millisecond-level voltage state switching. The coordinated operation of low-voltage ride-through branch 1 and low-voltage ride-through branch 2, combined with the adjustable characteristics of the series current-limiting reactor Xs, jointly realizes the continuous low-voltage ride-through test function required by the standard, capable of simulating multi-stage, continuous voltage drop scenarios that occur during power grid faults. Its core working principle is as follows:

[0112] (1) Base voltage sag setting and first-level sag generation:

[0113] First, according to the test requirements (e.g., simulating an initial drop to 80% of the rated voltage), the base impedance value is set by using a series current-limiting reactor Xs. The reactor Xs consists of five independent reactors Xs1 to Xs5 connected in series, with reactance values ​​designed in a ratio of 16:8:4:2:1 (binary weighting). Each reactor is connected in parallel with fast single-phase contactors QS1 to QS5.

[0114] By controlling the combination of QS1 to QS5, the equivalent impedance value of Xs can be finely adjusted (theoretically 32 combinations), thereby initially setting the base voltage level that the test point may reach without adding an additional low-voltage branch (usually higher than the target drop voltage).

[0115] Then, the low-voltage branch 1 is put into operation. The low-voltage branch 1 contains a parallel adjustable reactor Xp1. Xp1 is also composed of five independent reactors Xp11 to Xp15 connected in series, with the reactance values ​​designed in a ratio of 16:8:4:2:1. Each reactor is connected in parallel with fast contactors QP11 to QP15.

[0116] Based on the target first-level voltage drop depth (e.g., from rated voltage to 50%), precisely configure the equivalent impedance of Xp1 (theoretically 32 combinations). Connect Xp1 in parallel to the main circuit by closing contactor CB4-1, QL (phase sequence selection), and QN1 (grounding) (the connection point is the node between circuit breaker CB2 and disconnector CB9).

[0117] The core working principle is as follows: The parallel connection of Xp1 is equivalent to introducing a controllable parallel short-circuit impedance at the test point of the main circuit. According to the principle of voltage division by parallel impedance (or understood as introducing a controllable inductive current load at the test point, resulting in a voltage drop), the precisely configured impedance value of Xp1, together with the series current-limiting reactor Xs, precisely pulls the voltage at the test point down to the preset first-stage drop target value (e.g., 50% Un).

[0118] (2) Superposition of second-level voltage drops:

[0119] During the maintenance of the first voltage sag, the control system prepares to superimpose a second voltage sag based on test requirements (e.g., the need to further sag to 20% Un or 0% Un based on the first voltage sag).

[0120] At this point, the control system issues a command to quickly engage low-voltage branch 2. Low-voltage branch 2 contains a fixed reactor Xp2 (impedance set to 20% of the maximum impedance of Xs). By closing contactor CB4-2, Xp2 is connected in parallel to the main circuit (connected in parallel with low-voltage branch 1 at the same node).

[0121] The core working principle is as follows: By introducing an additional parallel short-circuit impedance Xp2, the equivalent parallel impedance at the test point is further reduced (or the equivalent inductive load current at the test point is increased). With the impedance of the series current-limiting reactor Xs remaining unchanged, the voltage at the test point will be further pulled down according to the voltage divider principle, achieving a second-stage voltage drop.

[0122] Combination accuracy: The combination of Xp1 (32 adjustable levels) in low-breakdown branch 1 and the fixed Xp2 in low-breakdown branch 2 can produce a wider variety of voltage drop depths. For example, if a deeper drop than Xp1 alone is required (such as near zero breakdown), Xp2 can be engaged; if fine adjustment of the drop depth within the adjustable range of Xp1 but not at the preset level is required, Xp2 can also be used for partial fine-tuning. Combined with the 32-level adjustment of the series current-limiting reactor Xs, theoretically, very fine voltage drop values ​​(up to 1024 combinations) can be achieved within the 0-90% range, covering the full spectrum from zero breakdown to deep voltage drop (mentioned in the original text on page 10 of the manual).

[0123] (3) Millisecond-level switching and waveform control:

[0124] The entire state switching process (connecting low-voltage branch 2) relies on a fast contactor (CB4-2, etc.). Its extremely short opening and closing time (≤20ms) ensures that:

[0125] Rapid state transition: The transition time from voltage drop at the first level to drop at the second level is extremely short, which can accurately simulate the continuous and rapid changes in voltage that may occur during power grid faults.

[0126] No current interruption: The contactor's operating time is much shorter than the voltage drop duration specified in the standard (usually hundreds of milliseconds), ensuring that the device under test will not malfunction and disconnect from the network due to a brief current interruption during the switching process.

[0127] During the switching process, the series current-limiting reactor Xs plays a crucial role in current limiting and overshoot suppression, limiting the inrush current that may be generated when the low-pass branch is connected, which helps to maintain the smoothness and stability of the voltage drop waveform.

[0128] Meanwhile, the auxiliary circuit (contactor CB13) closes during the low-voltage run-through process, connecting the boost resistor-capacitor Rd and CL to the grid terminal (rather than the test point terminal) to provide reactive power compensation, support the stability of the main grid voltage, and prevent excessive fluctuations in the real grid during the test process.

[0129] Ultimately, through precise timing control of the control system, parameters such as... can be generated at the test points. Figure 5 The waveform shown is a series of low voltage drops (e.g., from 100% -> 50% -> 20% -> recovery).

[0130] The continuous low-voltage ride-through (LVRT) function achieves precise first-stage voltage sag through a series current-limiting reactor Xs setting the base impedance, an adjustable shunt reactor Xp1 in LVRT branch 1 achieving precise first-stage voltage sag, and a fixed shunt reactor Xp2 in LVRT branch 2 rapidly engaging during the first-stage sag to achieve the second-stage voltage sag. A fast contactor ensures timely (millisecond-level) and seamless (no current interruption) state switching, Xs suppresses inrush current and stabilizes the waveform, and the auxiliary circuit (CB13 and boost resistor-capacitor) maintains grid stability. The binary proportional design and combined adjustment of Xp1 and Xs (32 levels each) provide the underlying technical support for achieving high-precision, multi-level voltage sag over a wide range (0-90%), meeting the needs of low-voltage ride-through testing in all scenarios.

[0131] Low-high continuous crossing: During the period when the low voltage state is maintained in the low-voltage branch (such as low-voltage branch 1 or 2), the high voltage state is switched to the high voltage state by means of a fast contactor (such as disconnecting the low voltage branch contactor CB4-1 / CB4-2 and simultaneously closing the high voltage branch contactor CB5, QC, etc.); the contactor opening and closing time is significantly less than the duration of the voltage state, ensuring that there is no current interruption during the state transition.

[0132] The continuous traversal function of this invention is achieved through a fast contactor collaborative control mechanism and a multi-branch dynamic switching architecture. Its core principle is as follows:

[0133] Basic performance of fast contactor group: It adopts magnetically held vacuum contactors to form fast action unit, and uses the synergistic effect of electromagnetic force and mechanical interlocking to achieve millisecond-level switching of circuit on and off states; the contactor drive coil is equipped with energy feedback circuit, which absorbs and suppresses arc generation through reverse electromotive force during opening and closing, ensuring electrical life and operation stability.

[0134] Continuous low voltage ride-through generation principle

[0135] First-stage voltage drop generation: By connecting the adjustable reactor group (Xp11-Xp15) of low-pass branch 1 with a preset impedance combination, an initial voltage trough is established at the test point;

[0136] Second-stage voltage drop superposition: While maintaining the first-stage voltage drop, the main grid voltage is stabilized through reactive power compensation of the auxiliary circuit (CB12), and the fixed reactor (Xp2) of the low-voltage branch 2 is put into operation to further reduce the voltage at the test point.

[0137] Waveform smoothing control: By adjusting the impedance of the current-limiting reactor (Xs) in stages, the interference of sudden current changes on the voltage waveform is suppressed.

[0138] Low-to-high continuous crossing conversion principle

[0139] Low-impedance stage maintenance: The low-impedance branch 1 / 2 forms a stable low-impedance path through the reactor network, clamping the test point voltage at the target low level;

[0140] Pre-charge transition: Before the end of the low-through state, a charge reserve is pre-established through the capacitor bank (CL) of the high-through branch;

[0141] Energy conversion switching: while disconnecting the low-voltage branch, the high-voltage branch contactor group is closed, and the energy stored in the capacitor is released in an orderly manner through the resistor network (Rd), so as to achieve a smooth rise in voltage state;

[0142] Dynamic stability guarantee mechanism

[0143] The auxiliary circuit (CB13) provides transient reactive power compensation and suppresses voltage overshoot during switching.

[0144] The current transformers (CT3-1 / CT4) monitor the changes in branch current in real time and adjust the input ratio of reactors / capacitors through closed-loop control.

[0145] The neutral circuit contactor (QN1 / QN2) ensures a stable potential reference under unbalanced operating conditions.

[0146] The extremely short opening and closing time of the fast contactor ensures seamless switching:

[0147] Time window matching: The opening and closing time of the fast contactor (usually <5ms) is much shorter than the voltage drop / rise duration specified in the standard (such as 150ms for a 10% Un undervoltage test). Multiple switching can be completed within the voltage fault phase, avoiding test failures caused by switching delays.

[0148] Dynamic response capability: For example, after the low-voltage branch 1 (such as the reactor bank) is deactivated, the fast contactor can switch to the low-voltage branch 2 (such as the capacitor bank) within 10ms, maintaining the voltage drop depth within ±2% error range, meeting the voltage accuracy requirements of the NB / T31051 standard.

[0149] Cooperative control of low-high continuous crossing

[0150] Seamless transition during fault phase: After the low voltage ride-through (e.g., 10%Un) ends, the fast contactor can disconnect the low-voltage ride-through branch and engage the high-voltage ride-through branch (e.g., 130%Un) within 5ms, ensuring that the voltage rises directly from the drop to the overvoltage state, simulating the transient overvoltage after the real power grid fault is cleared.

[0151] Avoid power interruption: Traditional contactors (opening time > 50ms) may cause voltage interruption, causing the tested equipment to disconnect from the grid; fast contactors shorten the interruption time to the millisecond level, allowing wind turbines or energy storage converters to remain connected to the grid, meeting the test requirements of three consecutive low-high ride-through tests for A1 / A2 class equipment.

[0152] Low test error and equipment risk

[0153] Reduce arcing and overshoot: Fast tripping suppresses arc reignition, avoids voltage overshoot (e.g., <5% per unit value), and prevents the tested equipment from malfunctioning due to overvoltage protection.

[0154] Improved testing efficiency: The entire process of low penetration → high penetration → recovery can be completed within one experimental cycle (e.g., 300ms), without the need for multiple start-ups and shutdowns of the equipment, improving efficiency by more than 3 times.

[0155] The fast contactor, through millisecond-level switching and high-precision control, keeps the dynamic error of voltage ride-through tests within ±2%, ensuring the accuracy and equipment safety of continuous low-to-high voltage ride-through tests.

[0156] 4. High and low voltage ride-through when the external power grid is 10kV

[0157] like Figure 1 As shown, when the external power grid is 10kV, set the current limiting impedance Xs, short-circuit impedance Xp1, and step-up resistor and capacitor Rd and CL as needed. Disconnect the disconnecting switches CB6 and CB10, close the disconnecting switches CB7, CB8, CB9, CB11, CB12, and CB13, and close the circuit breakers CB3 and CB1. When the unit is running in grid-connected mode, the test can be performed according to the steps shown in 1, 2, and 3, which will not be repeated here.

[0158] The quantities of current-limiting impedance Xs, short-circuit impedances Xp1 and Xp2, boost resistor-capacitor Rd, and CL mentioned above are just one example. They can also be other quantities, and designs formed by other quantities also fall within the scope of this utility model.

[0159] The above-described embodiments are detailed and specific, illustrating preferred embodiments of the present utility model. They are only used to illustrate the technical ideas and features of the present utility model, with the aim of enabling those skilled in the art to understand the content of the present utility model and implement it accordingly. However, they are not limited to the present utility model, and the patent scope of the present utility model cannot be limited by this embodiment alone. That is, any equivalent changes or modifications made to the spirit disclosed in the present utility model, without departing from the structure of the present utility model, such as local improvements within the system and modifications or transformations between subsystems, are still within the patent scope of the present utility model.

Claims

1. A 10kV-35kV high and low voltage ride-through test device, characterized in that, include: Main control circuit: Bushing XT1, circuit breaker CB1, current transformer CT1, voltage transformer PT1, disconnector CB6, reactor Xs, disconnector CB9, voltage transformer PT2, current transformer CT2, circuit breaker CB3, and bushing XT2 are connected in series in sequence, and circuit breaker CB2 is connected in parallel to both ends of reactor Xs. Transformer branch: Disconnector CB7 is connected in series with three-phase step-up transformer T1 and disconnector CB8 to form the first parallel branch; disconnector CB10 is connected in series with single-phase step-down transformers T2, T3, T4 and disconnector CB11 to form the second parallel branch; the first parallel branch is connected in parallel across disconnector CB6, and the second parallel branch is connected in parallel across circuit breaker CB9; Low-passage branch 1: Current transformer CT3-1, contactor CB4-1, contactor QL, adjustable reactor Xp1, and contactor QN1 are connected in series. Contactor QN1 is grounded. Current transformer CT3-1 is connected to the node between circuit breaker CB2 and disconnector CB9. Low-passage branch 2: Current transformer CT3-2, contactor CB4-2 and fixed reactor Xp2 are connected in series. Current transformer CT3-2 is connected to the node between circuit breaker CB2 and disconnector CB9. Low-passage branch 2 is connected in parallel with low-passage branch 1. High-pass branch: Current transformer CT4, contactor CB5, contactor QC, capacitor CL, resistor Rd, and contactor QN2 are connected in series. Contactor QN2 is grounded. Current transformer CT4 is connected to the node between circuit breaker CB2 and disconnector CB9. The high-pass branch is connected in parallel with low-pass branch 2. Auxiliary circuit: The first end of contactor CB12 is connected to the node between disconnector CB6 and reactor Xs, and the second end of contactor CB12 is connected to the node between contactor CB4-1 and contactor QL; the first end of contactor CB13 is connected to the node between disconnector CB6 and reactor Xs, and the second end of contactor CB13 is connected to the node between contactor CB5 and contactor QC.

2. The 10kV-35kV high and low voltage ride-through test device according to claim 1, characterized in that, The series reactor Xs consists of five independent reactors Xs1 to Xs5 connected in series. Each of the five independent reactors Xs1 to Xs5 has a single-phase contactor QS1 to QS5 connected in parallel across its two ends. The reactance values ​​of the five independent reactors Xs1 to Xs5 are designed in a ratio of 16:8:4:2:

1.

3. The 10kV-35kV high and low voltage ride-through test device according to claim 1, characterized in that, The parallel adjustable reactor Xp1 is composed of five independent reactors Xp11 to Xp15 connected in series. Contactors QP11 to QP15 are connected in parallel across the two ends of each of the five independent reactors Xp11 to Xp15. The reactance values ​​of the five independent reactors Xp11 to Xp15 are designed in a ratio of 16:8:4:2:

1.

4. The 10kV-35kV high and low voltage ride-through test device according to claim 1, characterized in that, Each phase of capacitor CL consists of six independent capacitors, C1 to C6, connected in parallel. Each capacitor is connected in series with a single-phase contactor to control its on / off state. The six single-phase contactors are QC1 to QC6. The capacitance values ​​of the six capacitors C1 to C6 are designed in a ratio of 32:16:8:4:2:

1.

5. The 10kV-35kV high and low voltage ride-through test device according to claim 1, characterized in that, Contactor QL consists of three independent single-phase contactors QL1 to QL3 connected in parallel, used to select the conduction phase sequence of the low-voltage branch 1; contactor QC consists of three independent single-phase contactors QC1 to QC3 connected in parallel, used to select the conduction phase sequence of the high-voltage branch.

6. The 10kV-35kV high and low voltage ride-through test device according to claim 1, characterized in that, Contactor QN1 is connected in series in the neutral circuit of the low-voltage branch 1, and contactor QN2 is connected in series in the neutral circuit of the high-voltage branch.

7. The 10kV-35kV high and low voltage ride-through test device according to claim 1, characterized in that, The three-phase step-up transformer T1 has a turns ratio of 10kV / 35kV. The single-phase step-down transformers T2, T3, and T4 have an input voltage compatible with 35kV and an output voltage compatible with 10kV.

8. A 10kV-35kV high and low voltage ride-through test device according to claim 1, characterized in that, All contactors QL1~QL3, QC1~QC3, QS1~QS5, and QP11~QP15 are fast contactors with a switching time of ≤20ms.

9. A 10kV-35kV high and low voltage ride-through test device according to claim 1, characterized in that, The impedance value of the fixed reactor Xp2 is set to 20% of the maximum impedance value of the reactor Xs.

10. The 10kV-35kV high and low voltage ride-through test device according to claim 1 or 8, characterized in that: The continuous voltage ride-through function of the high and low voltage ride-through test device is achieved through multi-branch coordinated switching: Continuous low voltage ride-through: After a voltage drop is generated by the current-limiting impedance Xs, low voltage ride-through branch 1 and low voltage ride-through branch 2, a voltage drop can be generated again by switching through a fast contactor. Low-high continuous crossing: During the period when the low voltage state is maintained in the low crossing branch, the overvoltage state is generated by switching to the high crossing branch through a fast contactor; The contactor's opening and closing action time is less than the duration of the voltage state, ensuring no current interruption during the state transition.

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