An inverter insulation impedance testing device and method

Abstract

The application discloses an inverter insulation impedance testing device and method, and belongs to the field of power electronic testing. A multi-stage adjustable resistance network composed of multiple high-precision fixed resistors is adopted, and resistance combination is switched quickly and accurately through hand-operated switch or controllable electronic switch matrix to simulate different insulation impedance values. The device integrates digital display instrument for real-time monitoring, contains secondary safety protection system and intelligent calibration module, and can automatically compensate contact resistance. The application improves the adjustment accuracy to ±0.1%, shortens the switching time to within 50ms, and prolongs the service life to more than 10 6 times, significantly improves the testing accuracy, efficiency, reliability and safety, and is particularly suitable for insulation performance detection of inverters with different power levels.

Description

Technical Field

[0001] This invention relates to power electronics testing, and more particularly to an inverter insulation resistance testing device and method. Background Technology

[0002] As the core equipment of a photovoltaic power generation system, the insulation performance of the inverter directly affects the safety and reliability of the entire system. Therefore, accurate testing of its insulation impedance is essential during the production, quality inspection, and maintenance of inverters. Currently, the industry commonly uses a testing scheme based on sliding rheostats to simulate different insulation impedance values ​​to verify the accuracy of the inverter's insulation monitoring function.

[0003] However, this traditional sliding rheostat solution has many inherent drawbacks:

[0004] Low accuracy and poor stability: The contact impedance of the sliding rheostat is unstable, and its accuracy is usually only ±5%. In addition, human error is easily introduced during the adjustment process, resulting in poor repeatability and low reliability of test results.

[0005] Short lifespan and insufficient reliability: Under high current testing conditions, the metal contacts of the sliding rheostat are prone to oxidation and wear, and its mechanical life is usually less than 5,000 cycles, which cannot meet the requirements of high frequency and long-term stable testing.

[0006] Low adjustment efficiency: It relies on manual adjustment, and each resistance adjustment takes a long time (usually more than 30 seconds), resulting in low testing efficiency and an inability to meet the fast-paced requirements of modern production lines.

[0007] Lack of dynamic response capability: The sliding rheostat has low adjustment resolution (the minimum step value is usually greater than 100Ω) and slow response speed, and cannot achieve fast and accurate resistance value steps, thus lacking dynamic response testing capability.

[0008] Limited functionality: This solution only supports static measurement, has a low sampling rate (<10Hz), and cannot memorize or automatically read back the test resistance value, resulting in low intelligence. Summary of the Invention

[0009] Purpose of the invention: The purpose of this invention is to provide a novel inverter insulation impedance testing device and method with high precision, high reliability, high efficiency and intelligent features.

[0010] Technical solution: An inverter insulation resistance testing device, comprising:

[0011] A multi-stage adjustable resistor network is composed of multiple fixed resistors (R0~Rn) with an accuracy better than ±1% connected in parallel or series, used to simulate different insulation resistance values;

[0012] A switching unit is connected to the multi-stage output resistor network. The switching unit includes multiple controllable switches (S0~S10). By controlling the closing and opening of the controllable switches, the fixed resistor can be selectively connected or bypassed to combine and output the target resistance value.

[0013] A measurement and display unit, connected to the multi-stage adjustable resistor network, is used to measure and display the resistance value output by the device in real time.

[0014] A safety protection unit is connected in series in the input circuit of the device to provide protection in case of abnormal current.

[0015] Furthermore, the fixed resistors in the multi-level adjustable resistor network are gold-plated aluminum-cased resistors, and their resistance values ​​are configured according to preset power levels. These power levels include at least 6kW, 12kW, 30kW, 50kW, 120kW, 250kW, and 320kW, with corresponding standard resistance values ​​of 15kΩ, 20kΩ, 25kΩ, 30kΩ, 50kΩ, 80kΩ, and 100kΩ, respectively. The specific power level-resistance value correspondence table is as follows:

[0016]

[0017] Furthermore, the switching unit is a manual switch array or an electronic contact matrix. By operating the switching unit, the resistance value can be adjusted in steps with an accuracy of 0.5%, and the resistance value switching time is less than or equal to 50 milliseconds.

[0018] Furthermore, the security protection unit includes dual redundant disconnect switches and self-resetting electronic fuses (FU0), forming a two-level security protection system.

[0019] Furthermore, the device also includes an intelligent calibration module for compensating the contact resistance of the device to make the contact resistance R ≤ 0.1mΩ, and supports zero calibration function.

[0020] Furthermore, the device also includes a preset scheme interface for receiving external commands and calling preset resistance combination test schemes.

[0021] Furthermore, the device also includes multiple plug-in terminals (a~k) for fixedly connecting input and output cables, and the resistance array can be varied by shorting different plug-in terminals using plug-in cables.

[0022] A method for testing the insulation resistance of an inverter includes the following steps:

[0023] S1. Based on the power level of the inverter under test, select the corresponding standard resistance value initial state through the switching unit;

[0024] S2. Connect the test device to the inverter under test via plug-in terminals;

[0025] S3. Start the test; the measurement and display unit displays the test parameters in real time.

[0026] S4. By operating the switching unit, the resistance value output by the multi-stage adjustable resistor network is dynamically adjusted to simulate the change in insulation impedance;

[0027] S5. Record the response data of the inverter under test under different insulation impedance values ​​to complete the test.

[0028] Furthermore, prior to step S1, a calibration step is included: performing contact resistance compensation and zeroing calibration operations through the intelligent calibration module.

[0029] Furthermore, in step S4, the preset test sequence is called through the preset scheme interface to realize automatic switching and testing of resistance values.

[0030] Beneficial effects:

[0031] (1) This invention abandons the traditional sliding rheostat and adopts a multi-stage adjustable resistor network composed of high-precision fixed resistors (such as gold-plated aluminum-cased resistors), which is combined with a manual switch or electronic contact matrix for switching. This design fundamentally eliminates contact impedance instability and human operation error, and improves the adjustment accuracy from ±5% of the traditional solution to a maximum of ±0.1%, an improvement of 50 times, ensuring extremely high repeatability and reliability of test results.

[0032] (2) Due to the use of a combination of solid-state switch and fixed resistor without mechanical sliding, the problems of contact oxidation and wear are avoided, which increases the continuous working life of the device from 5,000 times in the traditional scheme to 10^6 times, an increase of 200 times, which greatly reduces the equipment maintenance cost and failure rate.

[0033] (3) The resistance value is switched by a switch matrix, which is simple and quick to operate. The resistance value switching time can be shortened from the traditional 2 seconds to less than 20 milliseconds, which is 100 times faster. At the same time, it supports the interface of preset test schemes, which can realize the automation of the test process and greatly improve production efficiency, especially suitable for rapid inspection on the production line.

[0034] (4) A two-level safety protection system was introduced, including dual redundant disconnect switches and self-resetting electronic fuses, which provide multiple protections such as overcurrent and overvoltage for the device and the equipment under test, ensuring operational safety under high-voltage testing environment.

[0035] (5) The device integrates intelligent calibration technology (such as contact resistance compensation and zero calibration), which effectively eliminates system errors. In addition, it has digital display and preset scheme functions, which not only makes the testing process intuitive and transparent, but also realizes the standardization and intelligence of the testing process, meeting the testing needs under complex working conditions.

[0036] (6) The resistor network supports flexible plug-in combinations and can realize the multiplier array variation starting from 5kΩ. The test voltage can support up to 1500VDC (up from the traditional 2kV to 3kV), which can cover the test requirements of inverters with different power levels from 6kW to 320kW and above, and has a wide range of applications. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the device's circuit structure;

[0038] Figure 2 This is a connection diagram for plug-in terminals. Detailed Implementation

[0039] To make the technical solution of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0040] Example 1

[0041] like Figure 1 As shown, this embodiment provides a basic inverter insulation resistance testing device, the core of which is as follows:

[0042] Multi-stage adjustable resistor network: This network consists of multiple high-precision fixed resistors (R0, R1, R2, ... Rn). These resistors are preferably high-precision, low-temperature-coefficient gold-plated aluminum resistors. The resistance values ​​of each resistor are precisely calculated and configured, for example, R0 = 5kΩ, R1 = 10kΩ, R2 = 20kΩ, etc., arranged in a binary or decimal weighted manner to cover the required resistance range (e.g., 5kΩ to 100kΩ or wider) through combination.

[0043] Switching Unit: In this embodiment, the switching unit employs a set of manual switches (S0, S1, S2, ... S10). Each manual switch (S0~S10) is connected in series with one or more of the aforementioned fixed resistors (R0~Rn), and then connected in parallel between the input terminal (a) and the output terminal (k). By toggling different switch combinations, the corresponding resistors can be easily connected to or removed from the circuit, thereby quickly and accurately determining the target resistance value. For example, when a 15kΩ resistance value is required, the switches controlling R0 (5kΩ) and R1 (10kΩ) can be closed simultaneously.

[0044] Measurement and display unit: A digital ohmmeter (Ω) is connected in parallel across the resistor network to display the total resistance value of the current device output accurately in real time. This digital ohmmeter can be equipped with an external power supply interface to ensure stable display.

[0045] Safety protection unit: A fuse (FU0) is connected in series in the input circuit as primary overcurrent protection. In addition, the device can be equipped with a main disconnect switch (not fully shown in the figure, but the manual mentions "dual redundant disconnect switch") to form basic safety protection.

[0046] Connection terminals: The device is equipped with multiple plug-in terminals (a, b, c, ... k) for securing test cables. Different terminals can be connected using external shorting cables (e.g., shorting b and c). Figure 2 As shown, b and c~j are shorted using plug-in cables, allowing for resistor array variations of 5kΩ, 10kΩ, 15kΩ, 20kΩ, 25kΩ, 30kΩ... multiples. Selecting different resistors R0~Rn enables more diverse and high-precision combinations. The internal connection method of the resistor network can be changed (e.g., parallel / series connection), further expanding the adjustable range of the resistors.

[0047] The testing process is as follows:

[0048] First, the operator presets an initial resistance value (e.g., 25kΩ for a 30kW inverter) by toggling a manual switch, based on the inverter's power rating. Then, using a test cable, the device's input terminal (a) is connected to the inverter's DC positive terminal, and the output terminal (k) is connected to the DC negative terminal (or the casing ground). After connection, the device is powered on, and the digital ohmmeter displays the current resistance value. The operator can dynamically toggle the switch to change the resistance value and observe the inverter's insulation monitoring module's alarm threshold and response, thus completing the test.

[0049] Example 2

[0050] This embodiment is a further optimization and upgrade of Embodiment 1, focusing on automation and intelligence.

[0051] Upgrade of the switching unit: Replace the manual toggle switches (S0~S10) with electronic contact matrices, such as relays or solid-state switches. These switches are controlled by a single microcontroller (MCU).

[0052] Intelligent control core: A microcontroller (MCU) is added as the control core. The MCU is connected to the communication interface of the above-mentioned electronic switch control terminal, the measurement display unit (digital ohmmeter), and a preset interface (such as USB, RS485 or Ethernet port).

[0053] Advanced feature implementation:

[0054] Automatic testing: Users can select preset test schemes (such as "25kΩ→50kΩ→15kΩ step test") via the host computer software or the device's built-in keypad. After receiving the command, the MCU automatically drives the corresponding electronic switches in sequence to achieve rapid and automatic switching of resistance values.

[0055] Intelligent Calibration: The MCU has a built-in intelligent calibration algorithm. A self-calibration program can be initiated before each test or periodically. For example, "zero calibration" involves the MCU reading the base value of the digital display and storing it as an offset when the input is short-circuited, which is automatically subtracted in subsequent measurements; "contact resistance compensation" involves calculating and compensating for the switch contact resistance by measuring the voltage drop under low current, reducing the influence of system contact resistance to below 0.1mΩ.

[0056] Secondary safety protection: The safety protection system is more comprehensive. In addition to the basic fuse (FU0), an electronic switch controlled by an MCU is added as a front-end isolation, and voltage / current sensors may be integrated. The MCU monitors the circuit parameters in real time, and once an overcurrent or overvoltage abnormality is detected, it can cut off the main circuit within milliseconds, achieving dual redundancy active safety protection.

[0057] The measured data of this invention and the traditional sliding rheostat solution are compared as follows:

[0058]

[0059] This invention, through the innovative combination of a multi-level adjustable resistor network and an intelligent switching / control unit, successfully solves many bottlenecks in the accuracy, efficiency, lifespan, and safety of traditional testing methods, and provides a high-performance, high-reliability inverter insulation impedance testing solution.

[0060] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. An inverter insulation resistance testing device, characterized in that, include: A multi-stage adjustable resistor network is composed of multiple fixed resistors (R0~Rn) with an accuracy better than ±1% connected in parallel or series, used to simulate different insulation resistance values; A switching unit is connected to the multi-stage output resistor network. The switching unit includes multiple controllable switches (S0~S10). By controlling the closing and opening of the controllable switches, the fixed resistor can be selectively connected or bypassed to combine and output the target resistance value. A measurement and display unit, connected to the multi-stage adjustable resistor network, is used to measure and display the resistance value output by the device in real time. A safety protection unit is connected in series in the input circuit of the device to provide protection in case of abnormal current.

2. The inverter insulation resistance testing device according to claim 1, characterized in that, The fixed resistors in the multi-level adjustable resistor network are gold-plated aluminum-cased resistors, and their resistance values ​​are configured according to preset power levels. The power levels include at least 6kW, 12kW, 30kW, 50kW, 120kW, 250kW, and 320kW, with corresponding standard resistance values ​​of 15kΩ, 20kΩ, 25kΩ, 30kΩ, 50kΩ, 80kΩ, and 100kΩ, respectively.

3. The inverter insulation resistance testing device according to claim 1, characterized in that, The switching unit is a manual switch array or an electronic contact matrix. By operating the switching unit, the resistance value can be adjusted in steps of 0.5%, and the resistance value switching time is less than or equal to 50 milliseconds.

4. The inverter insulation resistance testing device according to claim 1, characterized in that, The security protection unit includes dual redundant disconnect switches and self-resetting electronic fuses (FU0), forming a two-level security protection system.

5. The inverter insulation resistance testing device according to claim 1, characterized in that, The device also includes an intelligent calibration module for compensating the contact resistance of the device to ensure that the contact resistance R ≤ 0.1mΩ, and supports zero-calibration function.

6. The inverter insulation impedance testing device according to claim 1, characterized in that, The device also includes a preset scheme interface for receiving external commands and calling preset resistance combination test schemes.

7. The inverter insulation impedance testing device according to claim 1, characterized in that, The device also includes multiple plug-in terminals (a~k) for fixedly connecting input and output cables. By shorting different plug-in terminals with plug-in cables, the multiplier of the resistor array can be changed.

8. A test method based on the inverter insulation resistance test device according to any one of claims 1 to 7, characterized in that, Includes the following steps: S1. Based on the power level of the inverter under test, select the corresponding standard resistance value initial state through the switching unit; S2. Connect the test device to the inverter under test via plug-in terminals; S3. Start the test; the measurement and display unit displays the test parameters in real time. S4. By operating the switching unit, the resistance value output by the multi-stage adjustable resistor network is dynamically adjusted to simulate the change in insulation impedance; S5. Record the response data of the inverter under test under different insulation impedance values ​​to complete the test.

9. The test method according to claim 8, characterized in that, Before step S1, a calibration step is also included: performing contact resistance compensation and zero calibration operations through the intelligent calibration module.

10. The test method according to claim 8, characterized in that, In step S4, the preset test sequence is called through the preset scheme interface to realize automatic switching and testing of resistance value.

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