Photovoltaic all-in-one machine (box transformer substation) detection equipment

Abstract

The invention discloses photovoltaic all-in-one machine (box transformer) detection equipment, which comprises a power frequency power supply, a boosting transformer, a capacitor bank, high-voltage switch equipment, a load reactor and a system controller, the capacitor bank is connected through the contactor, and the system controller controls switching of the capacitor unit; during detection, safety preparation, line connection and power supply starting are carried out firstly, a system controller automatically adjusts a capacitor unit according to a preset method to enable the current of a transformer to be detected to reach a rated value, then parameters are continuously monitored and recorded, and safety processing and report generation are carried out after the test is finished. The equipment and the method are low in energy consumption, low in cost, high in detection efficiency and accurate in result, can effectively detect the variable performance of the photovoltaic all-in-one case, and have remarkable application value.

Description

Technical Field

[0001] This invention relates to the field of electrical equipment testing technology, and in particular to a testing device for photovoltaic integrated machines (box-type substations). Background Technology

[0002] Transformers are important electrical components of photovoltaic integrated machines (box-mounted substations). The direct load method is a commonly used transformer testing method, but it has significant drawbacks. This method requires the configuration of power supply and load equipment that matches the transformer capacity, resulting in huge energy consumption during the testing process. At the same time, the purchase and maintenance costs are high, which seriously restricts the testing efficiency and economy.

[0003] To overcome the aforementioned shortcomings, the series resonance method has emerged. Based on the LC resonance principle, it can generate a large current that meets the detection requirements with a relatively small power supply, significantly reducing energy consumption and equipment capacity requirements. However, current mainstream series resonance schemes generally rely on frequency converters to track the resonance point in real time, which keeps the overall system cost high. For small and medium capacity transformers widely used in scenarios such as energy storage stations, this type of scheme is not economical and cannot meet the cost control requirements in practical applications. Therefore, a better detection equipment solution is urgently needed. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned technical deficiencies and propose a photovoltaic integrated machine (substation) testing device to solve the problems mentioned in the background art.

[0005] To achieve the above technical objectives, the present invention provides a photovoltaic integrated machine (box-type transformer) testing device, comprising: a power frequency power supply (1), a step-up transformer (2), a capacitor bank (3), a high-voltage switchgear (4), a load reactor (5), and a system controller (6); the low-voltage side of the step-up transformer (2) is connected to the power frequency power supply (1); the capacitor bank (3) includes several capacitor units (31) and a contactor, the capacitor units (31) are connected to the power frequency power supply (1) and the low-voltage side of the step-up transformer (2) through the contactor, the input terminal of the high-voltage switchgear (4) is connected to the high-voltage side of the step-up transformer (2), and the output terminal is connected to the high-voltage side of the transformer under test (7), the load reactor (5) is connected to the low-voltage side of the transformer under test (7), the voltage value of the power frequency power supply (1) is greater than the voltage value of the low-voltage side of the transformer under test, and the system controller (6) is connected to the contactor and the power frequency power supply (1); the system controller (6) controls the capacitor units (31) to be engaged or disengaged through the contactor.

[0006] Furthermore, the system controller (6) controls the contactor to stepwise switch the capacitor unit (31) according to a preset switching capacity. The preset switching capacity of the system controller (6) is determined according to the following steps: A1. Calculate the total inductive reactance of the system, which is the sum of the inductive impedances of the step-up transformer, the transformer under test, and the load reactor; A2. Determine the target impedance and required capacitive reactance. Convert the rated current of the high-voltage side of the transformer under test to the low-voltage side of the step-up transformer. Calculate the target impedance using Ohm's law and combine it with the total system impedance to calculate the required capacitive reactance. A3. Determine the switching capacity, calculate the total capacitance value based on the required capacitive reactance, and then determine the required compensation capacity.

[0007] Furthermore, the system controller (6) includes: a measurement unit (61), a calculation control unit (62), and a switching execution unit (63). The measurement unit (61) is used to collect the real-time current value of the transformer under test (7). The calculation control unit (62) outputs a control signal to the switching execution unit (63) according to the operating characteristics of the transformer under test. The switching execution unit (63) controls the contactor to engage or disengage.

[0008] Furthermore, the workflow of the system controller (6) is as follows: S1. Before testing, input the rated current of the transformer under test into the calculation control unit (62). I_target ; S2. During testing, the measuring unit (61) detects the real-time current of the transformer under test. I_m ; S3. The calculation control unit (62) sends a control signal to the switching execution unit (63) to control its switching step size ( Step The capacitor is used to determine the time delay. I_m and I_target Relationship: if I_m < I_target This indicates insufficient current, requiring additional capacitors to reduce the total impedance; let the number of capacitor banks currently in operation be... N = N + Step / 2 ; if I_m > I_target This indicates that the current is too high, and the capacitor count needs to be reduced to increase the total impedance; let the current number of capacitor banks be... N = N - Step / 2 ; S4. Calculate the update step size of the control unit (62): Step = Step / 2 If the new Step < 1 If the loop ends, the loop ends; otherwise, a control signal is sent to the switching execution unit (63), and the process returns to step S3.

[0009] Furthermore, the cutting step size in step S1 ( Step ) is initialized to half the total number of capacitor units (31); the current number of capacitor units ( N Initialize to the stated cutting step size ( Step The value of ).

[0010] Furthermore, several capacitor units (31) in the capacitor bank (3) are arranged according to binary weights.

[0011] Furthermore, the inspection method for this equipment includes the following steps: B1. Disconnect all power sources, fully discharge the capacitor bank, step-up transformer, and the high and low voltage sides of the transformer under test, and connect grounding wires. Set up physical isolation barriers and warning signs. B2. Connect the high-voltage terminal of the transformer under test to the high-voltage output terminal of the step-up transformer via a high-voltage switchgear, and connect the low-voltage terminal to the fixed load reactor. Check that all grounding wires are securely connected. B3. Disconnect all branches of the capacitor bank, and then close the main circuit switch for the power frequency power supply; B4. The system controller (6) controls the capacitor unit (31) to be put into or removed so that the transformer under test reaches the rated current; B5. Begin timing the test, continuously monitor and record the voltage, current, and winding temperature parameters on the high-voltage side of the transformer under test until thermal stability is achieved; B6. Disconnect the power frequency power supply from the main circuit switch, manually confirm and fully discharge the capacitor bank, step-up transformer, and transformer under test; B7. Disconnect all test cables and export the data to generate a report.

[0012] Compared with the prior art, the beneficial effects of the present invention include: 1. This invention replaces the frequency converter with a power frequency power supply, saving high purchase and maintenance costs, reducing initial costs by 40%-60%, and operation and maintenance costs by only 1 / 3 of the frequency converter solution; combined with binary weighted capacitor banks and a binary switching strategy, it simplifies control design, and the components use standardized devices, resulting in low procurement and replacement costs; this design accurately solves the economic contradiction of small-capacity transformer testing in scenarios such as energy storage stations, promoting its widespread application.

[0013] 2. In the current regulation stage, the present invention collects real-time current through the measurement unit, calculates and controls the control unit to issue control signals according to the current situation, and the switching execution unit responds quickly, so that the current of the transformer under test can quickly reach the rated current, thereby improving the detection efficiency. In the test monitoring stage, the voltage, current, power factor and winding temperature of the high-voltage side of the transformer under test are continuously monitored and recorded until the thermal stability state is reached. This allows for comprehensive and accurate acquisition of transformer performance data, ensuring the accuracy of the test results and meeting the needs of practical applications. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of a photovoltaic integrated machine (substation) testing device provided by the present invention; Figure 2This is a schematic diagram of the system controller of a photovoltaic integrated machine (substation) testing equipment provided by the present invention. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0016] Example 1 Reference Figure 1 The present invention provides a photovoltaic integrated machine (box-type substation) testing device, including a power frequency power supply 1, a step-up transformer 2, a capacitor bank 3, a high-voltage switchgear 4, and a load reactor 5.

[0017] The low-voltage side of the step-up transformer 2 is connected to the power frequency power supply 1. The capacitor bank 3 includes several capacitor units 31 and contactors. Each capacitor unit 31 is connected to the power frequency power supply 1 and the low-voltage side of the step-up transformer 2 through an independent contactor. The capacitor unit 31 can be put into or taken out by controlling the contactor to engage or disengage. The incoming terminal of the high-voltage switchgear 4 is connected to the high-voltage side of the step-up transformer 2, and the outgoing terminal is connected to the high-voltage terminal of the transformer under test 7. The load reactor 5 is connected to the low-voltage terminal of the transformer under test 7 to simulate the actual load of the transformer under test. In addition, this testing equipment also includes a system controller 6, which is connected to the contactor of the capacitor bank 3 and the power frequency power supply 1 respectively, and is used to control the switching of the capacitor unit 31 and monitor the output parameters of the power frequency power supply.

[0018] In this embodiment, the system controller 6 uses a preset switching capacity method to control the contactor to step-switch the capacitor unit 31.

[0019] The calculation method for its preset switching capacity is as follows: A1. Calculate the total system impedance: Leakage reactance of step-up transformer ( X T_bosst Known parameters: Rated capacity of the step-up transformer S bosst Rated high voltage U H_bosst Rated low voltage U L_bosst Short-circuit impedance percentage U k_bosst %.

[0020] , The leakage inductance reactance of the transformer under test, and known parameters: the rated capacity of the transformer under test. S test Rated high voltageU H_test Short-circuit impedance percentage U k_test The leakage inductance on the high-voltage side is converted to the low-voltage side of the test system.

[0021] Calculate the leakage reactance on the high-voltage side of the transformer under test: , Converted to the low-voltage side of the step-up transformer: , K This refers to the turns ratio of a step-up transformer. The inductive reactance of the load reactor ( X reactor Known parameters: Rated voltage of the load reactor U reactor and rated capacity S reactor and reactance X R %.

[0022] , Converted to the low-voltage side of the system: , Total system inductive impedance:

[0023] A2. Determine the target impedance and required capacitive reactance, and input the rated current of the high-voltage side of the transformer under test ( I test_H ) converted to the low-voltage side of the step-up transformer ( I bosst_L The target impedance is calculated using Ohm's law, and the required capacitive reactance is obtained by combining the total inductive reactance of the system.

[0024] , Target impedance: , Test the power supply voltage; The resistance in this system is small and can be ignored in practical applications. Therefore, the required capacitive reactance value is:

[0025] A3. Determine the switching capacity, calculate the total capacitance value based on the required capacitive reactance, and then determine the required compensation capacity.

[0026] Calculate the required total capacitance: ， Calculate the required compensation capacitance: , The method for testing photovoltaic integrated transformer substations using the testing equipment described in this invention includes the following steps: B1. Safety Preparation Phase: Disconnect all power supplies and fully discharge the capacitor bank, step-up transformer, and the high and low voltage sides of the transformer under test for at least 5 minutes, and install grounding wires on each side. Set up physical barriers and warning signs around the testing area to prevent unauthorized personnel from entering.

[0027] B2. Line Connection Stage: Connect the high-voltage terminals of the transformer under test to the high-voltage output terminal of the step-up transformer via a high-voltage switchgear, and connect the low-voltage terminals to the fixed load reactor. Carefully check the tightness and insulation of all connections to ensure reliable grounding.

[0028] B3. Power Start-up Phase: First, disconnect the contactors of all branches of the capacitor bank to ensure that the capacitor bank is initially completely disconnected; then close the main circuit switch of the power frequency power supply to supply power to the system.

[0029] B4. Current regulation stage: The system controller 6 automatically controls the connection or disconnection of capacitor unit 31 according to the above workflow, and adjusts the total capacity of the capacitor bank to make the current of the transformer under test reach the rated current.

[0030] B5. Test Monitoring Phase: Once the transformer under test reaches its rated current, the test begins with timing. Parameters such as voltage, current, power factor, and winding temperature on the high-voltage side of the transformer under test are continuously monitored and recorded. The test duration is determined according to relevant standards, and continues until the transformer under test reaches a thermally stable state, typically defined as a winding temperature change rate not exceeding 1°C for one consecutive hour.

[0031] B6. Test Completion Stage: After the test is completed, first disconnect the power frequency power supply and the main circuit switch, then manually confirm and fully discharge the capacitor bank, step-up transformer, and transformer under test to ensure the safety of equipment and personnel.

[0032] B7. Final Stage: Disconnect all test connections, export the data recorded during the test, and generate a test report using the data analysis software built into the system controller. The report includes test parameters, curves, and pass / fail results.

[0033] Example 2 Based on Embodiment 1, the system controller 6 specifically includes a measurement unit 61, a calculation control unit 62, and a switching execution unit 63, wherein: The measuring unit 61 mainly consists of a current sensor and a signal processing circuit, and is used to acquire the real-time current value of the transformer under test. I_m ; The calculation and control unit 62 uses a microprocessor as its core and adopts a binary adjustment strategy. It can output control signals based on the operating characteristics of the transformer under test and the real-time current value collected by the measurement unit 61. The switching execution unit 63 is composed of a relay drive circuit, which receives the control signal output by the calculation control unit 62 and controls the engagement or release of the corresponding contactor to realize the switching of the capacitor unit 31.

[0034] The capacitor units 31 in the capacitor bank 3 are arranged according to binary weights. For example, if there are a total of 8 capacitor units, their capacity can be set in the ratio of 1:2:4:8:16:32:64:128.

[0035] The workflow of system controller 6 is as follows: S1. Before testing, input the rated current of the transformer under test into the calculation control unit 62 through the human-machine interface of the system controller 6. I_target At the same time, the throwing step length will be adjusted. Step The initial value is half the total number of capacitor units (31). For example, if there are a total of 8 capacitor units... Step The initial value is 4; the current number of capacitor banks is set. N Initialize to the cutting step size Step The value of, i.e. N=4 .

[0036] S2. During testing, the measuring unit 61 detects the real-time current value of the transformer under test through a current sensor. I_m And transmit it to the computing control unit 62.

[0037] S3. The calculation control unit 62 sends a control signal to the switching execution unit 63 to control it to engage the switching step size ( Step The capacitor is used, and a delay of 1-2 seconds is applied to ensure circuit stability before judging the real-time current. I_m With rated current I_target Relationship: if I_m < I_target, This indicates that the current is insufficient, and it is necessary to add capacitors to reduce the total impedance, thereby increasing the current; at this point, let the number of capacitor banks be... N = N + Step / 2 ; if I_m > I_target This indicates that the current is too high, and the capacitor count needs to be reduced to increase the total impedance, thereby reducing the current. At this point, let the number of capacitor banks currently in operation be... N = N - Step / 2 .

[0038] S4. Calculate and update the switching step size of control unit 62: Step = Step / 2 If the new Step < 1If the minimum adjustment accuracy has been reached, the loop ends; otherwise, a control signal is sent to the switching execution unit 63, and the process returns to step S3 to continue capacitor switching adjustment until the real-time current of the transformer under test reaches the rated current value.

[0039] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A photovoltaic integrated machine (substation) testing device, comprising: The system comprises a power frequency power supply (1), a step-up transformer (2), a capacitor bank (3), a high-voltage switchgear (4), a load reactor (5), and a system controller (6); characterized in that: The low-voltage side of the step-up transformer (2) is connected to the power frequency power supply (1); the capacitor bank (3) includes several capacitor units (31) and a contactor. The capacitor units (31) are connected to the power frequency power supply (1) and the low-voltage side of the step-up transformer (2) through the contactor. The input terminal of the high-voltage switchgear (4) is connected to the high-voltage side of the step-up transformer (2), and the output terminal is connected to the high-voltage terminal of the transformer under test (7). The load reactor (5) is connected to the low-voltage terminal of the transformer under test (7). The voltage value of the power frequency power supply (1) is greater than the voltage value of the low-voltage side of the transformer under test. The system controller (6) is connected to the contactor and the power frequency power supply (1). The system controller (6) controls the capacitor units (31) to be engaged or disengaged through the contactor.

2. The photovoltaic integrated machine (substation) testing equipment according to claim 1, characterized in that: The system controller (6) controls the contactor to stepwise switch the capacitor unit (31) according to the preset switching capacity. The preset switching capacity value of the system controller (6) is determined according to the following steps: A1. Calculate the total inductive reactance of the system, which is the sum of the inductive impedances of the step-up transformer, the transformer under test, and the load reactor; A2. Determine the target impedance and required capacitive reactance. Convert the rated current of the high-voltage side of the transformer under test to the low-voltage side of the step-up transformer. Calculate the target impedance using Ohm's law and combine it with the total system impedance to calculate the required capacitive reactance. A3. Determine the switching capacity, calculate the total capacitance value based on the required capacitive reactance, and then determine the required compensation capacity.

3. The photovoltaic integrated machine (substation) testing equipment according to claim 1, characterized in that: The system controller (6) includes a measurement unit (61), a calculation control unit (62), and a switching execution unit (63). The measurement unit (61) is used to collect the real-time current value of the transformer under test. The calculation control unit (62) outputs a control signal to the switching execution unit (63) according to the operating characteristics of the transformer under test. The switching execution unit (63) controls the contactor to engage or disengage.

4. The photovoltaic integrated machine (substation) testing equipment according to claim 3, characterized in that: The workflow of the system controller (6) is as follows: S1. Before testing, input the rated current of the transformer under test into the calculation control unit (62). I_target ; S2. During testing, the measuring unit (61) detects the real-time current of the transformer under test. I_m ; S3. The calculation control unit (62) sends a control signal to the switching execution unit (63) to control its switching step size ( Step The capacitor is used to determine the time delay. I_m and I_target Relationship: if I_m <I_target This indicates insufficient current, requiring additional capacitors to reduce the total impedance; let the number of capacitor banks currently in operation be... N = N + Step / 2 ; if I_m>I_target This indicates that the current is too high, and the capacitor count needs to be reduced to increase the total impedance; let the current number of capacitor banks be... N = N - Step / 2 ; S4. Calculate the update step size of the control unit (62): Step = Step / 2 If the new Step<1 If the loop ends, the loop ends; otherwise, a control signal is sent to the switching execution unit (63), and the process returns to step S3.

5. A photovoltaic integrated machine (substation) testing device according to claim 4, characterized in that... The cutting step size in step S1 ( Step ) is initialized to half the total number of capacitor units (31); the current number of capacitor units ( N Initialize to the stated cutting step size ( Step The value of ).

6. The photovoltaic integrated machine (substation) testing equipment according to claim 5, characterized in that... The capacitor bank (3) consists of several capacitor units (31) arranged according to binary weights.

7. A test method for a photovoltaic integrated machine (substation) testing device according to any one of claims 2-6, characterized in that: Includes the following steps: B1. Disconnect all power sources, fully discharge the capacitor bank, step-up transformer, and the high and low voltage sides of the transformer under test, and connect grounding wires. Set up physical isolation barriers and warning signs. B2. Connect the high-voltage terminal of the transformer under test to the high-voltage output terminal of the step-up transformer via a high-voltage switchgear, and connect the low-voltage terminal to the fixed load reactor. Check that all grounding wires are securely connected. B3. Disconnect all branches of the capacitor bank, and then close the main circuit switch for the power frequency power supply; B4. The system controller (6) controls the capacitor unit (31) to be engaged or disengaged, so that the transformer under test reaches the rated current; B5. Begin timing the test, continuously monitor and record the voltage, current, and winding temperature parameters on the high-voltage side of the transformer under test until thermal stability is achieved; B6. Disconnect the power frequency power supply from the main circuit switch, manually confirm and fully discharge the capacitor bank, step-up transformer, and transformer under test; B7. Disconnect all test cables and export the data to generate a report.

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