A voltage continuous crossing test device based on two high crossing and two low crossing

Abstract

The application relates to the field of power electronics, in particular to a voltage continuous crossing test device based on two high crossings and two low crossings. The technical scheme is as follows: a voltage continuous crossing test device based on two high crossings and two low crossings comprises a main circuit which comprises, in sequence from an input end to an output end, a platform input circuit breaker CB1, a series reactor bypass circuit breaker CB2, a series reactor Xs and a platform output circuit breaker CB3, and the output end is used for connecting a grid-connected device to be tested; a low voltage crossing unit comprises two independent low crossing branches, the two low crossing branches are connected in parallel, one end of the two low crossing branches is commonly connected to a circuit node between the CB2 and the series reactor Xs, and the other end is grounded. The application realizes various complex test conditions, significantly reduces a plurality of sets of independent voltage generation units required by a traditional scheme, and thus reduces the overall complexity, volume and manufacturing cost of the device.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, and in particular to a voltage continuous ride-through test device based on two high-through and two low-through paths. Background Technology

[0002] Grid guidelines require that grid-connected power generation equipment maintain uninterrupted grid connection and provide grid support for a specified period when grid voltage drops (low voltage) or rises (high voltage) faults occur. This capability is known as voltage ride-through. To verify whether the equipment meets the standards, it must be tested in a laboratory using voltage drop / rise test fixtures.

[0003] Traditional voltage sag / rise simulators typically employ multiple independent sag units connected in complex series and parallel configurations to simulate varying voltage sag depths. However, this structure has limitations when simulating complex continuous ride-through conditions. For example, simulating "continuous low-voltage ride-through" (where a secondary sag occurs without voltage recovery) or "continuous low-high-voltage ride-through" (seamless transition from a low-voltage to a high-voltage state) requires at least three or more completely independent voltage generation units, with complex switching via high-speed switches. This results in a complex device structure, high cost, difficult control timing, and consequently reduced reliability.

[0004] Therefore, there is an urgent need in this field for a solution that is simple in structure, low in cost, and can flexibly and accurately simulate complex continuous voltage ride-through conditions. Summary of the Invention

[0005] This invention proposes a voltage continuous ride-through test device based on two high-pass and two low-pass voltages, which solves the problems of complex device structure, high cost, difficult control timing, and reduced reliability caused by traditional solutions in the prior art.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A voltage continuous ride-through test device based on two-channel high-throughput and two-channel low-throughput, comprising: The main circuit, from the input end to the output end, includes: platform input circuit breaker CB1, series reactor bypass circuit breaker CB2, series reactor Xs, and platform output circuit breaker CB3. The output end is used to connect the grid-connected equipment under test. The low voltage ride-through unit includes two independent low voltage ride-through branches. After the two low voltage ride-through branches are connected in parallel, one end is connected to the circuit node between CB2 and the series reactor Xs, and the other end is grounded. The high voltage ride-through unit includes two independent high voltage ride-through branches, which are connected in parallel on the line between the series reactor Xs and the platform output circuit breaker CB3. The control unit is electrically connected to all switching devices in the main circuit, low-voltage ride-through unit, and high-voltage ride-through unit, and is used to control their switching according to a preset timing sequence to achieve tests including continuous multi-stage low-voltage ride-through and low-high voltage continuous ride-through.

[0007] Furthermore, the first low-voltage ride-through branch in the low-voltage ride-through unit is composed of circuit breaker CB4, circuit breaker CB5 and shunt reactor Xp-1 connected in series; the second low-voltage ride-through branch is composed of circuit breaker CB6, circuit breaker CB7 and shunt reactor Xp-2 connected in series.

[0008] Furthermore, the first high-voltage crossing branch in the high-voltage crossing unit is composed of circuit breaker CB8, circuit breaker CB9, current-limiting resistor R3, and capacitor C1 connected in series; the second high-voltage crossing branch is composed of circuit breaker CB10, current-limiting resistor R4, and capacitor C2 connected in series.

[0009] Furthermore, it also includes a discharge circuit, which includes a discharge branch connected in parallel with capacitors C1 and C2 respectively. The discharge branch connected in parallel with capacitor C1 is composed of contactor KM1 and discharge resistor R1 connected in series, and the discharge branch connected in parallel with capacitor C2 is composed of contactor KM2 and discharge resistor R2 connected in series.

[0010] Furthermore, it also includes a current detection unit, which includes a current Hall sensor CT1 disposed at the common ground terminal of the low voltage ride-through unit, and the current Hall sensor CT1 is electrically connected to the control unit.

[0011] Furthermore, the inductive reactance value of the series reactor Xs is selected based on the system short-circuit ratio parameter, and the inductive reactance values ​​of the parallel reactors Xp-1 and Xp-2 are selected based on the voltage drop ratio required for the low voltage ride-through test.

[0012] Furthermore, the capacitive reactance values ​​of capacitors C1 and C2 and the resistance values ​​of current-limiting resistors R3 and R4 are selected according to the voltage boost ratio parameters required for the high-voltage ride-through test.

[0013] Furthermore, by controlling the alternating switching of circuit breakers CB4, CB5, CB6, and CB7 in the first and second low-voltage ride-through branches through the control unit, two continuous low-voltage ride-through test waveforms can be generated at the grid-connected equipment under test.

[0014] Furthermore, by controlling the disconnection of the low-voltage ride-through branch and the connection of capacitor C1 or C2 in the high-voltage ride-through branch during or after the low-voltage ride-through test, the voltage at the end of the grid-connected equipment under test can be changed from a drop state to a rise state, thereby realizing continuous testing from low-voltage ride-through to high-voltage ride-through.

[0015] Furthermore, after completing a high-voltage ride-through test, the control unit controls the closing of the corresponding contactor KM1 or KM2, and rapidly discharges the corresponding capacitor C1 or C2 through the discharge resistor R1 or R2 to eliminate the influence of residual voltage on subsequent tests.

[0016] The positive effects of this invention are: Highly integrated topology significantly reduces cost and size: Two low-throughput and two high-throughput functions are integrated into a unified test platform. Through a series reactor Xs and clever branch configuration, multiple test functions are realized, avoiding the problem of needing multiple independent voltage generation units in traditional solutions, simplifying the structure and reducing costs.

[0017] Rapid switching and continuous, high-quality output voltage waveform: The switching between low-voltage and high-voltage modes is completed by quickly opening and closing the corresponding branch circuit breakers. The action speed is fast, the voltage transition process is smooth, and it can simulate the actual dynamic changes of power grid faults with high fidelity.

[0018] The test is highly flexible: by utilizing two independent low-pass branches, it can flexibly simulate single drops, two-stage continuous drops, or graded recovery. By combining the timing with two high-pass branches, it can perform complex test conditions that meet national standards, such as direct lifting after a drop and multiple consecutive drops and lifts.

[0019] High safety and reliability: The system is designed with a series reactor bypass circuit breaker CB2 to ensure normal system operation when not under testing. Each low-voltage branch adopts a double circuit breaker design, improving current carrying and breaking reliability. The high-voltage branch is specially designed with a discharge circuit consisting of a discharge contactor and a discharge resistor to ensure that the capacitor energy can be quickly released after testing, protecting the safety of personnel and equipment. Current-limiting resistors R3 and R4 effectively suppress the inrush current and high-frequency oscillation when the capacitor is switched on. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the circuit structure of the voltage continuous ride-through test device based on two high-pass and two low-pass circuits of the present invention. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0022] Example Combination Figure 1As shown, this embodiment details the working principle of a voltage continuous ride-through test device based on two high-through and two low-through paths. This device is connected in series between a grid simulator and grid-connected equipment such as the photovoltaic inverter, wind power converter, or electrochemical energy storage system under test. It is used in a laboratory environment to simulate complex fault conditions involving voltage dips, rises, and continuous changes in grid voltage to verify whether the grid-connected equipment meets the voltage ride-through capability requirements specified in standards such as NB / T 31051 and GB / T 34133-2023.

[0023] Overall structure and connection of the device The testing device is an integrated topology, and its main components and connections are as follows: Main circuit: Serving as the main power flow channel. Starting from the grid simulator side, the following circuits are connected in series: platform input circuit breaker CB1, current-limiting reactor bypass circuit breaker CB2, series reactor Xs, and platform output circuit breaker CB3. The output is ultimately connected to the grid-connected device under test. The bypass circuit breaker CB2 is connected in parallel across the series reactor Xs to bypass Xs when the device is not being tested, minimizing the main circuit impedance.

[0024] Low Voltage Ride-Through (LVRH) Unit: Used to simulate grid voltage dip faults. This unit consists of two completely independent LVRH branches with different parameters, connected in parallel. One end of the parallel branch is connected to the circuit node between CB2 and the series reactor Xs, and the other end is grounded. Each LVRH branch employs a double circuit breaker design (e.g., CB4 and CB5 in LVRH branch 1, CB6 and CB7 in LVRH branch 2) connected in series with a parallel reactor (Xp-1 and Xp-2, respectively). This design improves the current-carrying capacity and operational safety of the branches. The two branches allow the device to simulate two different depths of voltage dips or continuous dips.

[0025] High Voltage Ride-Through Unit: Used to simulate grid voltage rise faults. This unit contains two independent high-voltage ride-through branches connected in parallel between the series reactor Xs and the platform output circuit breaker CB3. Each high-voltage ride-through branch includes a circuit breaker (e.g., CB8 and CB9 in high-voltage ride-through branch 1, and CB10 in branch 2), current-limiting resistors (R3 and R4), and energy storage capacitors (C1 and C2). In addition, each branch has a dedicated discharge circuit, which consists of a discharge contactor (KM1 and KM2) connected in series and a discharge resistor (R1 and R2) connected in parallel across the corresponding capacitor. The current-limiting resistor is used to suppress the inrush current when the capacitor is switched on and to eliminate high-frequency resonance, while the discharge resistor is used to quickly discharge residual charge from the capacitor after testing, ensuring operational safety.

[0026] The detection and control unit includes a current Hall sensor CT1 located at the common ground terminal of the low voltage ride-through unit, and a core control unit (e.g., a programmable logic controller, PLC). The control unit is electrically connected to all circuit breakers (CB1 to CB10), contactors (KM1, KM2), and sensor CT1. It receives test commands from the host computer and drives the opening and closing operations of all switching devices according to preset, precise timing logic.

[0027] Device working process and principle 1. Normal operating mode Before any testing, the device is in a transparent transmission state. The control unit closes the incoming circuit breaker CB1, the bypass circuit breaker CB2, and the outgoing circuit breaker CB3. At this time, the series reactor Xs is short-circuited by CB2, and all branches of the low-impedance and high-impedance units are in an open state. The electrical energy output from the power grid simulator is directly transmitted to the device under test through the low-impedance path formed by CB1, CB2, and CB3, without having a substantial impact on the system.

[0028] 2. Low Voltage Ride-Through Test Procedure When a low-voltage ride-through test is required, the device operates according to the following steps: First, the control unit disconnects the bypass circuit breaker CB2 of the series reactor, thereby connecting the series reactor Xs in series with the main circuit. At this point, a defined inductive impedance is introduced into the main circuit.

[0029] Next, according to the voltage drop depth simulated in the test procedure, the control unit closes the corresponding low-voltage branch circuit breaker. For example, to simulate 20% residual voltage, circuit breakers CB4 and CB5 can be closed, and shunt reactor Xp-1 can be connected. At this time, the series reactor Xs and the connected shunt reactor (such as Xp-1) form an impedance voltage divider network. The connection of the shunt reactor creates a shunt path to ground at the main circuit node (between CB2 and Xs). According to the voltage divider principle, the voltage at the device under test (i.e., the output voltage) will drop according to the impedance ratio of Xs and Xp-1. The drop depth can be precisely set by selecting Xp-1 and Xp-2 with different inductive reactance values, thereby realizing two different fixed drop depth tests.

[0030] To simulate continuous low-voltage ride-through (e.g., a secondary drop before voltage recovery), two independent low-voltage ride-through branches can be used. The control unit can first activate the first low-voltage ride-through branch (e.g., Xp-1) to generate the first stage of drop. After a specified duration, this branch is disconnected, and the second low-voltage ride-through branch (Xp-2) is activated almost simultaneously. Because Xp-1 and Xp-2 have different impedance values, the voltage at the device under test will change from one drop depth to another, thus accurately simulating the continuous drop or graded recovery test sequence required by the standard.

[0031] 3. High Voltage Ride-Through Test Procedure Before conducting the high voltage ride-through test, ensure that all low voltage branch circuit breakers are disconnected and that the series reactor Xs is connected to the main circuit by disconnecting CB2.

[0032] Subsequently, the control unit closes the circuit breaker of the selected high-voltage ride-through branch. For example, closing CB8 and CB9 connects the current-limiting resistor R3 and capacitor C1 into the circuit. At this time, the series reactor Xs and the parallel capacitor C1 work together. The addition of the capacitor changes the equivalent impedance characteristics of the line, causing the voltage at the device under test to rise. The magnitude of the voltage rise is determined by the inductive reactance of Xs, the capacitive reactance of C1, and the system frequency. Through parameter design, high-voltage ride-through test points meeting different standard requirements can be achieved. The current-limiting resistor R3 serves to suppress inrush current from the capacitor and protect the device.

[0033] 4. Low-to-high voltage continuous ride-through test process This test condition is used to verify the equipment's ability to operate continuously when it immediately faces a voltage rise fault after a voltage drop fault, and it is the key to the device of this invention in simulating complex operating conditions.

[0034] The operating process is as follows: The control unit first puts the device into a low-voltage ride-through test state (for example, CB2 has been disconnected and Xp-1 of low-voltage ride-through branch 1 has been connected). After the low-voltage ride-through test has lasted for a predetermined period of time, in order to simulate the continuous change of voltage from drop to rise, the control unit performs a high-speed switching operation: quickly disconnecting all low-voltage ride-through branch circuit breakers (such as CB4 and CB5), and almost simultaneously connecting the circuit breakers and capacitors of high-voltage ride-through branches (such as CB8 and CB9, and connecting C1).

[0035] Since the low-voltage crossing branch (parallel inductive load) and the high-voltage crossing branch (parallel capacitive load) are connected in different positions in the circuit topology and do not conflict with each other, this switching is only a matter of switching the branch switch, without the need for complex topology reconfiguration. Therefore, the voltage can quickly and smoothly transition from the drop state determined by the "Xs and Xp voltage divider" to the rise state determined by the "Xs and C series resonance / capacitive rise". This method can realistically simulate the dynamics of the power grid and achieve "continuous low-voltage ride-through".

[0036] The control unit can cyclically control different combinations of low-voltage and high-voltage ride-through branches according to a set timing sequence (e.g., 200ms for closing, 100ms for opening) to complete multiple consecutive low-to-high voltage ride-through test cycles. For example, the first cycle uses low-voltage and high-voltage ride-through branches 1, and the second cycle switches to low-voltage and high-voltage ride-through branches 2. During the process, the discharge contactor KM1 is controlled to discharge the high-voltage ride-through capacitor C1 to eliminate the influence of residual voltage on subsequent tests, thereby realizing a flexible and complex continuous test sequence.

[0037] The above-described embodiments are detailed and specific, illustrating preferred embodiments of the present invention. They are only used to illustrate the technical ideas and features of the present invention, with the aim of enabling those skilled in the art to understand the content of the present invention and implement it accordingly. However, they are not limited to the present invention, and the patent scope of the present invention cannot be limited by this embodiment alone. That is, any equivalent changes or modifications made to the spirit disclosed in the present invention, without departing from the structure of the present invention, such as local improvements within the system and modifications or transformations between subsystems, are still within the patent scope of the present invention.

Claims

1. A voltage continuous ride-through test device based on two-path high-through and two-path low-through, characterized in that, include: The main circuit, from the input end to the output end, includes: platform input circuit breaker CB1, series reactor bypass circuit breaker CB2, series reactor Xs, and platform output circuit breaker CB3. The output end is used to connect the grid-connected equipment under test. The low voltage ride-through unit includes two independent low voltage ride-through branches. After the two low voltage ride-through branches are connected in parallel, one end is connected to the circuit node between CB2 and the series reactor Xs, and the other end is grounded. The high voltage ride-through unit includes two independent high voltage ride-through branches, which are connected in parallel on the line between the series reactor Xs and the platform output circuit breaker CB3. The control unit is electrically connected to all switching devices in the main circuit, low-voltage ride-through unit, and high-voltage ride-through unit, and is used to control their switching according to a preset timing sequence to achieve tests including continuous multi-stage low-voltage ride-through and low-high voltage continuous ride-through.

2. The voltage continuous ride-through test device based on two-path high-pass and two-path low-pass as described in claim 1, characterized in that, The first low-voltage ride-through branch in the low-voltage ride-through unit is composed of circuit breaker CB4, circuit breaker CB5 and parallel reactor Xp-1 connected in series; the second low-voltage ride-through branch is composed of circuit breaker CB6, circuit breaker CB7 and parallel reactor Xp-2 connected in series.

3. The voltage continuous ride-through test device based on two-path high-pass and two-path low-pass as described in claim 1, characterized in that, The first high-voltage crossing branch in the high-voltage crossing unit consists of circuit breaker CB8, circuit breaker CB9, current-limiting resistor R3, and capacitor C1 connected in series; the second high-voltage crossing branch consists of circuit breaker CB10, current-limiting resistor R4, and capacitor C2 connected in series.

4. The voltage continuous ride-through test device based on two-path high-pass and two-path low-pass as described in claim 3, characterized in that, It also includes a discharge circuit, which includes a discharge branch connected in parallel with capacitors C1 and C2 respectively. The discharge branch connected in parallel with capacitor C1 is composed of contactor KM1 and discharge resistor R1 connected in series, and the discharge branch connected in parallel with capacitor C2 is composed of contactor KM2 and discharge resistor R2 connected in series.

5. The voltage continuous ride-through test device based on two-path high-pass and two-path low-pass as described in claim 1, characterized in that, It also includes a current detection unit, which includes a current Hall sensor CT1 disposed at the common ground terminal of the low voltage ride-through unit, and the current Hall sensor CT1 is electrically connected to the control unit.

6. The voltage continuous ride-through test device based on two-path high-through and two-path low-through according to claim 2, characterized in that, The inductive reactance value of the series reactor Xs is selected based on the system short-circuit ratio parameter, and the inductive reactance values ​​of the parallel reactors Xp-1 and Xp-2 are selected based on the voltage drop ratio required for the low voltage ride-through test.

7. The voltage continuous ride-through test device based on two-path high-pass and two-path low-pass as described in claim 3, characterized in that, The capacitive reactance values ​​of capacitors C1 and C2 and the resistance values ​​of current-limiting resistors R3 and R4 are selected based on the voltage boost ratio parameters required for the high-voltage ride-through test.

8. The voltage continuous ride-through test device based on two-path high-through and two-path low-through according to claim 2, characterized in that, By controlling the alternating switching of circuit breakers CB4, CB5, CB6, and CB7 in the first and second low-voltage ride-through branches by the control unit, two continuous low-voltage ride-through test waveforms can be generated at the grid-connected equipment under test.

9. A voltage continuous ride-through test device based on two-path high-pass and two-path low-pass as described in claim 3 or 8, characterized in that, By controlling the disconnection of the low-voltage ride-through branch and the connection of capacitor C1 or C2 in the high-voltage ride-through branch during or after the low-voltage ride-through test, the voltage at the terminal of the grid-connected equipment under test can be changed from a drop state to a rise state, thus realizing continuous testing from low-voltage ride-through to high-voltage ride-through.

10. A voltage continuous ride-through test device based on two-path high-through and two-path low-through according to claim 4, characterized in that, After completing a high-voltage ride-through test, the control unit closes the corresponding contactor KM1 or KM2 to quickly discharge the corresponding capacitor C1 or C2 through the discharge resistor R1 or R2, so as to eliminate the influence of residual voltage on subsequent tests.

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