Solid state transformer function test system and method based on small power energy feeding opposite towing method

Abstract

The application discloses a solid-state transformer function test system and method based on a small-power energy feedback opposite-pulling method, belongs to the technical field of solid-state transformer testing, and comprises: a power grid working condition simulation module, which is used for simulating a power grid working condition according to actual function test requirements and outputting a power grid simulation signal; a solid-state transformer to be tested, which executes regulation and control in response to the power grid simulation signal and outputs a signal after regulation and control, and an output port of the solid-state transformer to be tested is electrically connected with an input port of the power grid working condition simulation module to form an energy feedback opposite-pulling loop with energy closed loop; and a function test module, which is used for collecting electrical parameters at the output port of the power grid working condition simulation module, the output port of the solid-state transformer to be tested and the input port of the solid-state transformer to be tested, and testing the function of the solid-state transformer to be tested according to the electrical parameters. The technical problem that the prior art is difficult to realize the accurate test of the electrical performance of the solid-state transformer under the premise of controlling the test cost and reducing energy consumption is solved.

Description

Technical Field

[0001] This invention relates to the field of solid-state transformer testing technology, specifically to a solid-state transformer functional testing system and method based on the low-power energy feed-to-drive method. Background Technology

[0002] Solid-state transformers, as a core technology of next-generation flexible power electronics, can accurately adapt to the development trend of power grid digitalization and power electronics, and are a core supporting equipment for building new power systems. However, the current solid-state transformer testing system is still imperfect. Solid-state transformers are mostly presented in a modular, fully packaged form on the user side. Their testing can be divided into multiple levels such as equipment, control and protection, and components. However, it is difficult for users to disassemble internal components for individual testing. Whole-machine testing has become the key to ensuring its application reliability. Solid-state transformer whole-machine testing can be further divided into multiple dimensions such as electrical performance, reliability, electromagnetic compatibility, protection function, and environmental adaptability. Among them, the electrical performance dimension focuses on the power conversion and transmission capabilities of the equipment, covering efficiency testing, power output accuracy testing, voltage regulation range testing, and current stability testing. It is the basic dimension for evaluating whether the core functions of the equipment meet the standards. At present, the existing testing capabilities of conventional distribution transformers can support the verification of most reliability dimensions of solid-state transformers, and the testing of electromagnetic compatibility and environmental adaptability can reuse existing equipment. However, there is still a significant gap in the electrical performance dimension. Compared to conventional transformers, solid-state transformers offer additional functions such as power quality optimization, multi-port output with different voltage characteristics and levels, voltage and frequency support, and power factor regulation. However, their grid configuration support, power regulation, and power quality optimization functions require a simulated power grid operating environment for comprehensive verification, which current testing conditions cannot meet. To address this testing capability gap, the main technical solution currently is the full-power power grid simulation method. This method relies on a high-precision power grid simulator to reproduce the voltage levels, frequency characteristics, harmonic content, and fault transient processes of a real power grid, constructing a full-condition testing environment highly consistent with actual applications. However, the full-power solution suffers from high costs and high energy consumption, hindering large-scale application. Therefore, achieving accurate testing of the electrical performance of solid-state transformers while controlling testing costs and reducing energy consumption remains a technical challenge that current technologies struggle to address. Summary of the Invention

[0003] To address the technical challenge of achieving accurate testing of the electrical performance of solid-state transformers while controlling testing costs and reducing energy consumption using existing technologies, this invention provides a functional testing system and method for solid-state transformers based on a low-power energy feed-to-drive method. By constructing an energy-closed-loop energy feed-to-drive circuit, it achieves energy recycling to reduce energy consumption and testing costs. A power grid simulation module outputs simulated power grid signals that meet the actual functional testing requirements, and the functional testing module performs comparison and verification based on multi-port electrical parameters. Through power grid simulation, closed-loop energy feed design, and multi-parameter linkage comparison, this invention solves the technical problem of achieving accurate testing of the electrical performance of solid-state transformers while controlling testing costs and reducing energy consumption using existing technologies.

[0004] To address the aforementioned technical problems, this invention provides a functional testing system for solid-state transformers based on the low-power energy feed-to-drive method, comprising: The power grid operating condition simulation module has its output port electrically connected to the input port of the solid-state transformer under test. It is used to simulate power grid operating conditions according to actual functional test requirements and output power grid simulation signals. The solid-state transformer under test (SST) responds to the grid simulation signal to perform regulation and outputs the regulated signal. The output port of the SST is electrically connected to the input port of the grid operating condition simulation module to form an energy feedback loop with closed energy loop. The functional test module is electrically connected to the output port of the power grid operating condition simulation module, the output port of the solid-state transformer under test, and the input port of the solid-state transformer under test, respectively. It is used to collect the first electrical parameter at the output port of the power grid operating condition simulation module, the second electrical parameter at the output port of the solid-state transformer under test, and the third electrical parameter at the input port of the solid-state transformer under test, and to test the function of the solid-state transformer under test based on the first electrical parameter, the second electrical parameter, and the third electrical parameter.

[0005] Preferably, the power grid operating condition simulation module integrates a low-voltage AC port, a low-voltage DC port, and a medium-voltage AC port; The low-voltage AC port is used to receive low-voltage AC power output from the power supply module that is electrically connected to the low-voltage AC port, and convert the low-voltage AC power into low-voltage DC power. The low-voltage DC port is used to receive low-voltage DC power and the closed-loop feedback power of the energy feed-to-drive circuit, and to convert the low-voltage DC power into medium-voltage AC power. The medium-voltage AC port is used to simulate the grid operating conditions based on medium-voltage AC power and according to the actual functional test requirements, combined with closed-loop feedback power, and output grid simulation signals. Specifically, the output port of the power grid operating condition simulation module is a medium-voltage AC port, and the input port of the power grid operating condition simulation module is a low-voltage DC port.

[0006] In this scheme, by constructing an energy closed-loop energy feed-to-drive circuit, internal energy recycling can be achieved, effectively reducing test energy consumption and equipment costs. However, the closed-loop feedback power will have a reverse effect on the power grid operating condition simulation stage, which can easily cause simulation waveform deviation and operating condition distortion. To address this, this invention introduces a coupling correction of the closed-loop feedback power during the power grid operating condition simulation process. While retaining the advantages of energy recycling and energy saving, it also suppresses the interference of feedback power on the accuracy of operating condition simulation, thereby improving the accuracy of solid-state transformer electrical performance testing.

[0007] Preferably, the step of using medium-voltage AC as the simulation basis, and according to actual functional test requirements, combining closed-loop feedback power to simulate grid operating conditions, and outputting a grid simulation signal includes: Pre-set the corresponding theoretical power grid operating parameters according to the actual functional test requirements; Based on theoretical power grid operating parameters and closed-loop feedback power, the waveform of medium-voltage AC is reconstructed to generate simulated operating waveform, and the initial power grid simulation signal is obtained based on the simulated operating waveform. The deviation between the actual power grid operating parameters and the theoretical power grid operating parameters of the initial power grid simulation signal is obtained. Based on the deviation, the initial power grid simulation signal is corrected and the power grid simulation signal is obtained and output. The actual functional test requirements include at least the power quality optimization function test, the multi-port output function test, the voltage and frequency support function test, and the power factor regulation function test.

[0008] This scheme employs a combination of theoretical grid operating parameters and closed-loop feedback power for waveform reconstruction, which suppresses power back-current disturbances caused by the energy closed loop at the source, alleviating the technical contradiction between operating condition simulation accuracy and energy recycling. Based on this, the deviation is obtained by comparing the actual operating parameters of the initial grid simulation signal with the theoretical target parameters. Closed-loop correction of the signal based on this deviation further eliminates residual deviations caused by non-ideal factors such as line losses and device nonlinearity, ensuring that the final output grid simulation signal highly matches the target simulated operating condition. This approach achieves low-cost, low-energy-consumption testing while significantly improving the accuracy and reliability of grid operating condition simulation, enabling precise verification of the electrical performance of solid-state transformers.

[0009] Preferably, the waveform reconstruction of medium-voltage AC power based on theoretical grid operating parameters and closed-loop feedback power includes: The impact of closed-loop feedback power on theoretical grid operating parameters is obtained based on the module's electrical characteristic parameters. The theoretical grid operating parameters are then corrected based on the impact. Finally, the waveform of medium-voltage AC power is reconstructed based on the corrected theoretical grid operating parameters.

[0010] Preferably, the step of testing the function of the solid-state transformer under test based on the first electrical parameter, the second electrical parameter, and the third electrical parameter includes: According to the actual functional test requirements, the second electrical parameter is compared with the first electrical parameter. If the comparison is successful, the function of the solid-state transformer under test is verified by combining the first electrical parameter and the third electrical parameter according to the actual functional test requirements. Otherwise, it indicates that the power grid simulation signal is distorted and an error is reported.

[0011] Preferably, the step of comparing the second electrical parameter with the first electrical parameter according to actual functional test requirements includes: The target comparison parameters are determined according to the actual functional test requirements. The parameter difference between the target comparison parameter in the second electrical parameter and the target comparison parameter in the first electrical parameter is obtained. If the parameter difference is less than the preset difference, the comparison is successful; otherwise, the comparison fails.

[0012] Preferably, the verification of the function of the solid-state transformer under test based on actual functional test requirements, combined with the first and third electrical parameters, includes: Based on the actual functional test requirements, the corresponding functional test indicators are determined. The parameter data corresponding to the functional test indicators are extracted from the first electrical parameter and the third electrical parameter. The actual test values ​​corresponding to the functional test indicators are obtained based on the parameter data. If the actual test values ​​all meet the preset functional qualification standards, the functional test is judged to be qualified; otherwise, it is judged to be unqualified.

[0013] Preferably, the functional test module is also communicatively connected to the energy compensation module for issuing energy compensation commands. The energy compensation module is electrically connected to the power grid operating condition simulation module for outputting compensation energy to compensate the power grid operating condition simulation module according to the energy compensation commands.

[0014] Preferably, the power grid operating condition simulation module also integrates a control and protection submodule for monitoring and regulating the operating status of the low-voltage AC port, the low-voltage DC port, and the medium-voltage AC port.

[0015] By adopting the above technical solution, the present invention has the following advantages: By constructing an energy-closed-loop energy feed-to-drive circuit, electrical energy recycling is achieved to reduce energy consumption and testing costs. The power grid operating condition simulation module outputs simulated power grid signals that meet the actual functional testing requirements, and the functional testing module verifies the results based on multi-port electrical parameters. Through power grid operating condition simulation, closed-loop energy feed design, and multi-parameter linkage comparison, the technical problem of accurately testing the electrical performance of solid-state transformers while controlling testing costs and reducing energy consumption, as demonstrated by existing technologies, is solved. Waveform reconstruction is achieved by combining theoretical grid operating parameters with closed-loop feedback power, suppressing power back-current disturbances caused by the energy closed loop at the source and alleviating the technical contradiction between operating condition simulation accuracy and energy recycling. Based on this, the deviation is obtained by comparing the actual operating parameters of the initial grid simulation signal with the theoretical target parameters. Closed-loop correction of the signal based on this deviation further eliminates residual deviations caused by non-ideal factors such as line losses and device nonlinearity, ensuring that the final output grid simulation signal highly matches the target simulated operating condition. This approach significantly improves the accuracy and reliability of grid operating condition simulation while achieving low-cost, low-energy-consumption testing, enabling precise verification of the electrical performance of solid-state transformers.

[0016] This invention also provides a functional testing method for solid-state transformers based on the low-power energy feed-to-drive method, applicable to the aforementioned functional testing system for solid-state transformers based on the low-power energy feed-to-drive method, comprising: Simulates power grid operating conditions based on actual functional test requirements and outputs power grid simulation signals; It performs regulation in response to the grid analog signal and outputs the regulated signal; The first electrical parameter at the output port of the power grid operating condition simulation module, the second electrical parameter at the output port of the solid-state transformer under test, and the third electrical parameter at the input port of the solid-state transformer under test are collected, and the function of the solid-state transformer under test is tested based on the first electrical parameter, the second electrical parameter, and the third electrical parameter.

[0017] By adopting the above technical solution, the present invention has the following advantages: By constructing an energy-closed-loop energy feed-to-drive circuit, electrical energy recycling is achieved to reduce energy consumption and testing costs. A grid operating condition simulation module outputs grid simulation signals that meet the actual functional testing requirements, and the functional testing module verifies the results based on multi-port electrical parameters. Through grid operating condition simulation, closed-loop energy feed design, and multi-parameter linkage comparison, the technical problem of accurately testing the electrical performance of solid-state transformers while controlling testing costs and reducing energy consumption, as in existing technologies, is solved. Attached Figure Description

[0018] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings. The drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings.

[0019] Figure 1 This is a schematic diagram of the solid-state transformer functional test system based on the low-power energy feed-to-drive method of the present invention; Figure 2This is a flowchart illustrating the functional testing method for solid-state transformers based on the low-power energy feed-to-drive method of the present invention. Detailed Implementation

[0020] 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 only one preferred embodiment of this invention and are only used to explain this invention. They do not limit the scope of protection of this invention. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0021] Before discussing the exemplary embodiments in more detail, it should be mentioned that some exemplary embodiments are described as processes or methods depicted as flowcharts. Although the flowcharts describe the operations (or steps) as sequential processes, many of the operations (or steps) can be performed in parallel, concurrently, or simultaneously. Furthermore, the order of the operations can be rearranged. The process can be terminated when its operation is completed, but it may also have additional steps not included in the figures; the process may correspond to a method, function, procedure, subroutine, subroutine, etc.

[0022] Example 1: As Figure 1 As shown, the functional test system for a solid-state transformer based on the low-power energy feed-to-drive method includes: The power grid operating condition simulation module has its output port electrically connected to the input port of the solid-state transformer under test. It is used to simulate power grid operating conditions according to actual functional test requirements and output power grid simulation signals.

[0023] As an optional embodiment, the power grid operating condition simulation module integrates a low-voltage AC port, a low-voltage DC port, and a medium-voltage AC port; The low-voltage AC port is used to receive low-voltage AC power output from the power supply module that is electrically connected to the low-voltage AC port, and convert the low-voltage AC power into low-voltage DC power. The low-voltage DC port is used to receive low-voltage DC power and the closed-loop feedback power of the energy feed-to-drive circuit, and to convert the low-voltage DC power into medium-voltage AC power. The medium-voltage AC port is used to simulate the grid operating conditions based on medium-voltage AC power and according to the actual functional test requirements, combined with closed-loop feedback power, and output grid simulation signals. Specifically, the output port of the power grid operating condition simulation module is a medium-voltage AC port, and the input port of the power grid operating condition simulation module is a low-voltage DC port.

[0024] As an optional embodiment, the power grid operating condition simulation module also integrates a control and protection submodule for monitoring and regulating the operating status of the low-voltage AC port, the low-voltage DC port, and the medium-voltage AC port.

[0025] The power supply module is specifically an AC 380V distribution cabinet, and the medium-voltage AC port is specifically a programmable AC power supply. The power grid condition simulation module adopts a third-generation wide-bandgap semiconductor silicon carbide (SiC-MOSFET) multi-level modular cascade design with a rated capacity of 2.5MVA. The medium-voltage AC side has a power grid simulation capability of 8.5kV~11kV, the low-voltage AC side can achieve 380VAC±10% voltage regulation (rated power 400KVA), and the DC side voltage regulation range is 200Vdc~2500Vdc, adapting to a 40-60Hz operating frequency. It can accurately simulate typical operating conditions such as power grid voltage sags, harmonic injection, and frequency deviations, and also has an energy feedback function to simulate various load characteristics. It can be understood that flexible power transmission between the low-voltage AC port, low-voltage DC port, and medium-voltage AC port is achieved through a three-stage conversion stage, including an AC / DC conversion stage, a DC / DC conversion stage, and a DC / AC conversion stage. The AC / DC conversion stage consists of three parallel cascaded H-bridge rectifier sub-units, each containing multiple series-connected H-bridge rectifier modules. The power input of the medium-voltage AC port (MVAC) of the power grid simulation module is connected to the AC input of the AC / DC conversion stage, and the AC output of the low-voltage AC port (LVAC) of the power grid simulation module is also connected to the corresponding input of the AC / DC conversion stage. The AC / DC conversion stage uses pulse-width modulation rectification technology to convert the AC input into a stable DC bus voltage, while simultaneously achieving input power factor correction. The DC outputs of each sub-unit are connected in series to form a high-voltage DC bus, providing DC support for the subsequent DC / DC conversion stage. The three sub-units of the DC / DC conversion stage correspond one-to-one with those of the AC / DC conversion stage. Each sub-unit contains an isolated bidirectional DC / DC converter module (using a full-bridge phase-shifted resonant topology), with a built-in high-frequency transformer for electrical isolation and voltage level conversion. The DC input of the DC / DC converter stage is connected to the high-voltage DC bus of the AC / DC converter stage, and the DC output is connected in parallel to form a low-voltage DC bus, which is then connected to the power input of the low-voltage DC port (LVDC) of the power grid simulation module, realizing bidirectional power transfer between high-voltage DC and low-voltage DC. The DC / AC converter stage consists of an H-bridge inverter module and an LC filter circuit. Its DC input is connected to the low-voltage DC bus, and its AC output, after filtering, is connected to the AC input of the low-voltage AC port (LVAC) of the power grid simulation module. The DC / AC converter stage uses PWM inverter technology to convert the low-voltage DC bus voltage into low-distortion sinusoidal low-voltage AC power (such as AC 380V), providing power to low-voltage AC loads or input interfaces.The low-voltage AC port (LVAC) of the power grid operating condition simulation module receives low-voltage AC power from the AC 380V distribution cabinet. After rectification by the AC / DC conversion stage, it is input to the power input of the low-voltage DC port (LVDC) of the power grid operating condition simulation module. The low-voltage DC power is boosted to medium-voltage DC power by the DC / DC conversion stage, and then inverted to medium-voltage AC power by the AC / DC conversion stage. This topology supports bidirectional power flow.

[0026] The control and protection submodule is integrated within the power grid operating condition simulation module and also possesses the following core functions: Status monitoring: Real-time acquisition of key operating parameters such as voltage, current, temperature, and switch status of the three-stage converter stage, achieving full-link status visualization; Closed-loop control: Dynamically adjusting the PWM drive signal based on a closed-loop control algorithm to maintain DC bus voltage stability and ensure that the output power quality meets standards; Fault protection: Possessing fault detection and rapid response capabilities for overvoltage, overcurrent, overtemperature, and short circuits, it can actively shut down faulty modules or switch redundant paths to ensure continuous and stable testing. In this embodiment, the power grid operating condition simulation module adopts a modular cascaded design, which can flexibly expand power capacity and voltage levels; a high-frequency transformer replaces the traditional power frequency transformer, significantly reducing the size and weight of the equipment and increasing power density; the multi-port flexible interconnection feature adapts to various testing scenarios, and combined with the closed-loop control and fault-tolerant mechanism of the control and protection submodule, further enhances the reliability and applicability of the power grid operating condition simulation module.

[0027] In some embodiments, the step of using medium-voltage AC as the simulation basis, and according to actual functional test requirements, combining closed-loop feedback power to simulate grid operating conditions, and outputting a grid simulation signal includes: Pre-set the corresponding theoretical power grid operating parameters according to the actual functional test requirements; Based on theoretical power grid operating parameters and closed-loop feedback power, the waveform of medium-voltage AC is reconstructed to generate simulated operating waveform, and the initial power grid simulation signal is obtained based on the simulated operating waveform. The deviation between the actual power grid operating parameters and the theoretical power grid operating parameters of the initial power grid simulation signal is obtained. Based on the deviation, the initial power grid simulation signal is corrected and the power grid simulation signal is obtained and output. The actual functional test requirements include at least the power quality optimization function test, the multi-port output function test, the voltage and frequency support function test, and the power factor regulation function test.

[0028] Understandably, the power grid operating parameters include at least voltage, frequency, harmonics, and phase. Taking the power quality optimization function test as an example, the 3rd, 5th, 7th, and 11th harmonic components are superimposed on the power grid voltage, with the voltage content of each harmonic being 5%, 4%, 3%, and 2%, respectively, and the total harmonic distortion rate of the voltage not less than 8%, to verify the filtering and mitigation effect of the solid-state transformer under test on harmonics. The three-phase voltage amplitude deviation is set to 8%, and the phase angle deviation is set to 6° to simulate an unbalanced power grid condition, and to assess the compensation and balancing capability of the solid-state transformer under test for three-phase imbalance. The voltage fluctuation amplitude is set to ±5% of the rated voltage, and the fluctuation frequency is set to 10Hz to simulate a voltage fluctuation condition, and to verify the effect of the solid-state transformer under test on the smoothing and stabilization control of voltage fluctuations. Through the above-mentioned preset theoretical power grid operating parameters, the power quality optimization performance of the solid-state transformer under test in terms of harmonic mitigation, three-phase imbalance regulation, and voltage stability can be comprehensively measured. Understandably, the multi-port output function test specifically refers to verifying whether the solid-state transformer can simultaneously output stable voltage and power that meet rated specifications at multiple ports, with each port operating independently and without interference, thus verifying whether its multi-port collaborative power supply, load-carrying capacity, and output power quality meet design requirements. The voltage and frequency support function test specifically refers to verifying whether the solid-state transformer can respond quickly to unstable conditions such as voltage drops / rises or frequency deviations in the power grid, providing voltage and frequency support to the grid by adjusting its own output voltage and power, helping the grid voltage and frequency quickly recover to the rated range, thus verifying its voltage and frequency stabilization capabilities and grid connection support performance under grid disturbances. The power factor regulation function test specifically refers to setting inductive or capacitive reactive power deviations in a simulated power grid, causing the power factor to deviate from the rated value, and testing whether the solid-state transformer can compensate for reactive power in the grid by dynamically adjusting reactive power output, correcting the power factor to a set target value (e.g., above 0.95), thus verifying its reactive power regulation capability, power factor control accuracy, and optimization effect on grid losses.

[0029] If the theoretical power grid operating parameters corresponding to the actual functional test requirements are voltage amplitude, frequency, harmonic components, three-phase imbalance, and power factor, then the deviation between the actual power grid operating parameters and the theoretical power grid operating parameters of the initial power grid simulation signal is obtained. Based on the deviation, the initial power grid simulation signal is corrected and the power grid simulation signal is obtained and output. This includes: extracting the actual voltage amplitude, actual frequency, actual harmonic components, actual three-phase imbalance, and actual power factor respectively; comparing the actual voltage amplitude, actual frequency, actual harmonic components, actual three-phase imbalance, and actual power factor with the corresponding parameters in the theoretical power grid operating parameters, and calculating the amplitude deviation, frequency deviation, harmonic deviation, three-phase imbalance deviation, and power factor deviation; constructing a closed-loop correction command based on each deviation, and performing feedforward compensation on the initial power grid simulation signal. Closed-loop regulation: When the actual voltage amplitude is higher than the theoretical voltage amplitude, the amplitude of the initial grid simulation signal is reduced proportionally to the deviation; when the actual voltage amplitude is lower than the theoretical voltage amplitude, the amplitude of the initial grid simulation signal is increased proportionally to the deviation; when the actual frequency deviates from the theoretical frequency, frequency correction is achieved by adjusting the period of the initial grid simulation signal; for harmonic deviation and three-phase imbalance deviation, corresponding compensation harmonic components and negative-sequence and zero-sequence compensation components are injected to suppress harmonic distortion and asymmetric deviation; for power factor deviation, the reactive power component adjustment combined with closed-loop feedback power is used to correct the active and reactive power ratio of the initial grid simulation signal, so that the actual power factor approaches the theoretical set value; after multiple iterative corrections, the deviation between the actual grid operating parameters and the theoretical grid operating parameters is less than a preset threshold, and finally a stable and accurate grid simulation signal is output. In this embodiment, the closed-loop process of preset theoretical parameters, waveform reconstruction, deviation correction and iterative calibration can effectively reduce the deviation between the initial power grid simulation signal and the theoretical operating condition parameters, ensuring that the simulated power grid operating conditions conform to the actual power grid operating characteristics, providing an accurate test environment for various functional tests, and ensuring the authenticity and reliability of the test results.

[0030] Specifically, the waveform reconstruction of medium-voltage AC power based on theoretical grid operating parameters and closed-loop feedback power includes: The impact of closed-loop feedback power on theoretical grid operating parameters is obtained based on the module's electrical characteristic parameters. The theoretical grid operating parameters are then corrected based on the impact. Finally, the waveform of medium-voltage AC power is reconstructed based on the corrected theoretical grid operating parameters.

[0031] In this embodiment, the module electrical characteristic parameters specifically refer to the output impedance characteristics of the medium-voltage AC port, the parameters of the internal LC filter network, and the dynamic response characteristics (switching frequency, bandwidth, dead-zone effect) of the SiC / IGBT inverter in the power grid operating condition simulation module. In this embodiment, taking the theoretical power grid operating condition parameters as voltage and frequency as examples, the influence of voltage is... , Indicates closed-loop feedback power. This indicates the output impedance of the medium-voltage AC port in the power grid operating condition simulation module. This represents the theoretical voltage amplitude. Understandably, the output impedance directly determines the magnitude of the voltage impact; the higher the output impedance, the greater the voltage impact for the same closed-loop feedback power, meaning the theoretical voltage amplitude is significantly affected. Frequency influence. , This indicates the dead zone of the SiC / IGBT inverter. The value of C represents the inductance of the LC filter network, and the value of C represents the capacitance of the LC filter network. This indicates the control bandwidth of the SiC / IGBT inverter. This indicates the switching frequency of the SiC / IGBT inverter. Indicates the theoretical frequency. This represents the frequency correction factor, with a value ranging from 0.01 to 0.05, and is calibrated by the switching characteristics of the SiC / IGBT inverter.

[0032] In this embodiment, waveform reconstruction is performed using theoretical grid operating parameters and closed-loop feedback power to suppress power reverse disturbances caused by the energy closed loop at the source, thus alleviating the technical contradiction between operating condition simulation accuracy and energy recycling. Based on this, the deviation is obtained by comparing the actual operating parameters of the initial grid simulation signal with the theoretical target parameters. Closed-loop correction of the signal based on this deviation further eliminates residual deviations caused by non-ideal factors such as line losses and device nonlinearity, ensuring that the final output grid simulation signal highly matches the target simulated operating condition. This achieves low-cost, low-energy-consumption testing while significantly improving the accuracy and reliability of grid operating condition simulation, enabling precise verification of the electrical performance of solid-state transformers.

[0033] The solid-state transformer under test (SSD) responds to the grid simulation signal to perform regulation and outputs the regulated signal. The output port of the SSD is electrically connected to the input port of the grid operating condition simulation module to form an energy feedback loop with a closed energy loop.

[0034] In this embodiment, the solid-state transformer under test (SSD) integrates a low-voltage DC port (LVDC), a medium-voltage AC port (MVAC), other ports, and a control and protection submodule. The MVAC port in the SSD receives medium-voltage AC power from the power grid simulation module. After internal conversion, low-voltage DC power is output from the LVDC port in the SSD. This low-voltage DC power is fed back to the LVDC port in the power grid simulation module, forming a bidirectional power cycle integrated source-load architecture. The control and protection submodule in the SSD monitors the operating parameters of the SSD and coordinates with the test process to achieve state regulation. In this embodiment, the electrical energy output from the load side (such as the solid-state transformer) during the test is fed back to the power grid simulation module through an energy feed-to-drive loop, realizing energy recovery and reuse, and reducing test energy consumption.

[0035] The functional test module is electrically connected to the output port of the power grid operating condition simulation module, the output port of the solid-state transformer under test, and the input port of the solid-state transformer under test, respectively. It is used to collect the first electrical parameter at the output port of the power grid operating condition simulation module, the second electrical parameter at the output port of the solid-state transformer under test, and the third electrical parameter at the input port of the solid-state transformer under test, and to test the function of the solid-state transformer under test based on the first electrical parameter, the second electrical parameter, and the third electrical parameter.

[0036] The functional testing module includes a data acquisition module and a control module. The data acquisition module adopts the NIPXIe system and is equipped with a voltage / current / power acquisition card (sampling frequency of 100kHz), a high-frequency power analyzer (measurement accuracy of 0.05%, bandwidth of DC~5MHz), an oscilloscope, and high-precision sensors for acquiring electrical parameters. The control module is based on a PLC (typically Siemens S7-1500) or an industrial computer, communicates with other units via Ethernet, and has built-in operating condition control algorithms and performance evaluation models. It can realize 100-step operating condition programming control, complete the adjustment of operating condition parameters, and can also test the function of the solid-state transformer under test based on the first, second, and third electrical parameters.

[0037] In some embodiments, the test of the function of the solid-state transformer under test based on the first electrical parameter, the second electrical parameter, and the third electrical parameter includes: According to the actual functional test requirements, the second electrical parameter is compared with the first electrical parameter. If the comparison is successful, the function of the solid-state transformer under test is verified by combining the first electrical parameter and the third electrical parameter according to the actual functional test requirements. Otherwise, it indicates that the power grid simulation signal is distorted and an error is reported.

[0038] Given the diverse functionalities of the solid-state transformers under test (SSTs) and the significant differences in verification logic for different functional tests, using a uniform and fixed comparison and verification standard would be insufficient to accurately reflect the true performance of the SSTs. Therefore, based on actual functional testing requirements, corresponding comparison and verification standards are dynamically matched to ensure that each type of functional test accurately reflects the true performance of the SST, avoiding verification distortion caused by standardized criteria.

[0039] Specifically, the comparison of the second electrical parameter with the first electrical parameter according to actual functional test requirements includes: The target comparison parameters are determined according to the actual functional test requirements. The parameter difference between the target comparison parameter in the second electrical parameter and the target comparison parameter in the first electrical parameter is obtained. If the parameter difference is less than the preset difference, the comparison is successful; otherwise, the comparison fails.

[0040] Specifically, the verification of the function of the solid-state transformer under test, based on actual functional test requirements and in conjunction with the first and third electrical parameters, includes: Based on the actual functional test requirements, the corresponding functional test indicators are determined. The parameter data corresponding to the functional test indicators are extracted from the first electrical parameter and the third electrical parameter. The actual test values ​​corresponding to the functional test indicators are obtained based on the parameter data. If the actual test values ​​all meet the preset functional qualification standards, the functional test is judged to be qualified; otherwise, it is judged to be unqualified.

[0041] Understandably, both the preset difference and the preset functional qualification standard can be flexibly adjusted according to actual needs.

[0042] In some embodiments, the functional test module is also communicatively connected to the energy compensation module for issuing energy compensation commands. The energy compensation module is electrically connected to the power grid operating condition simulation module for outputting compensation energy to perform energy compensation on the power grid operating condition simulation module according to the energy compensation commands.

[0043] In this embodiment, the energy compensation module uses a Keysight N6705B programmable DC power supply with an output power range of 0-20kVA, supplementing 10% of the rated power loss. In some embodiments, the energy compensation module is integrated into the power grid operating condition simulation module.

[0044] The testing procedure for this system can be as follows: Test Preparation: Connect the solid-state transformer under test (SST), and preset the grid voltage (10kV rated voltage, 8.5kV low voltage ride-through voltage), frequency (50Hz), load power (rated / 120% overload), fault type, and programming parameters (voltage rise time 500μs, hold time 1s, etc.); System Startup: The grid operating condition simulation module outputs simulated grid operating conditions and inputs the grid simulation signal to the SST. The energy compensation module starts and outputs an initial compensation of 10% of the rated power; Energy Cycle and Operating Condition Adjustment: The electrical energy output by the SST, i.e., the closed-loop feedback power, is rectified and inverted by the energy feeder circuit and fed back to the grid operating condition simulation module to form a closed-loop cycle. The functional test module collects electrical parameters in real time, adjusts the operating status of the SST and the output parameters of the grid operating condition simulation module, switches between rated load, overload, voltage sag, three-phase imbalance, and other operating conditions, and performs functional tests based on the collected electrical parameters to generate a test report.

[0045] Example 2: Figure 2 As shown, this embodiment also provides a functional test method for solid-state transformers based on the low-power energy feed-to-drive method, applicable to the aforementioned functional test system for solid-state transformers based on the low-power energy feed-to-drive method, including: Simulates power grid operating conditions based on actual functional test requirements and outputs power grid simulation signals; It performs regulation in response to the grid analog signal and outputs the regulated signal; The first electrical parameter at the output port of the power grid operating condition simulation module, the second electrical parameter at the output port of the solid-state transformer under test, and the third electrical parameter at the input port of the solid-state transformer under test are collected, and the function of the solid-state transformer under test is tested based on the first electrical parameter, the second electrical parameter, and the third electrical parameter.

[0046] The specific embodiments described above are preferred embodiments of the solid-state transformer functional test system and method based on the low-power energy feed-to-drive method of the present invention, and are not intended to limit the specific scope of the present invention. The scope of the present invention includes but is not limited to the specific embodiments described above. All equivalent changes made in accordance with the shape and structure of the present invention are within the protection scope of the present invention.

Claims

1. A functional test system for solid-state transformers based on the low-power energy feed-to-drive method, characterized in that, include: The power grid operating condition simulation module has its output port electrically connected to the input port of the solid-state transformer under test. It is used to simulate power grid operating conditions according to actual functional test requirements and output power grid simulation signals. The solid-state transformer under test (SST) responds to the grid simulation signal to perform regulation and outputs the regulated signal. The output port of the SST is electrically connected to the input port of the grid operating condition simulation module to form an energy feedback loop with closed energy loop. The functional test module is electrically connected to the output port of the power grid operating condition simulation module, the output port of the solid-state transformer under test, and the input port of the solid-state transformer under test, respectively. It is used to collect the first electrical parameter at the output port of the power grid operating condition simulation module, the second electrical parameter at the output port of the solid-state transformer under test, and the third electrical parameter at the input port of the solid-state transformer under test, and to test the function of the solid-state transformer under test based on the first electrical parameter, the second electrical parameter, and the third electrical parameter.

2. The solid-state transformer functional test system based on the low-power energy feed-to-drive method according to claim 1, characterized in that, The power grid operating condition simulation module integrates a low-voltage AC port, a low-voltage DC port, and a medium-voltage AC port. The low-voltage AC port is used to receive low-voltage AC power output from the power supply module that is electrically connected to the low-voltage AC port, and convert the low-voltage AC power into low-voltage DC power. The low-voltage DC port is used to receive low-voltage DC power and the closed-loop feedback power of the energy feed-to-drive circuit, and to convert the low-voltage DC power into medium-voltage AC power. The medium-voltage AC port is used to simulate the grid operating conditions based on medium-voltage AC power and according to the actual functional test requirements, combined with closed-loop feedback power, and output grid simulation signals. Specifically, the output port of the power grid operating condition simulation module is a medium-voltage AC port, and the input port of the power grid operating condition simulation module is a low-voltage DC port.

3. The solid-state transformer functional test system based on the low-power energy feed-to-drive method according to claim 2, characterized in that, The system, based on medium-voltage AC power as a simulation foundation and according to actual functional test requirements, combines closed-loop feedback power to simulate grid operating conditions and outputs a grid simulation signal, including: Pre-set the corresponding theoretical power grid operating parameters according to the actual functional test requirements; Based on theoretical power grid operating parameters and closed-loop feedback power, the waveform of medium-voltage AC is reconstructed to generate simulated operating waveform, and the initial power grid simulation signal is obtained based on the simulated operating waveform. The deviation between the actual power grid operating parameters and the theoretical power grid operating parameters of the initial power grid simulation signal is obtained. Based on the deviation, the initial power grid simulation signal is corrected and the power grid simulation signal is obtained and output. The actual functional test requirements include at least the power quality optimization function test, the multi-port output function test, the voltage and frequency support function test, and the power factor regulation function test.

4. The solid-state transformer functional test system based on the low-power energy feed-to-drive method according to claim 3, characterized in that, The waveform reconstruction of medium-voltage AC power based on theoretical power grid operating parameters and closed-loop feedback power includes: The impact of closed-loop feedback power on theoretical grid operating parameters is obtained based on the module's electrical characteristic parameters. The theoretical grid operating parameters are then corrected based on the impact. Finally, the waveform of medium-voltage AC power is reconstructed based on the corrected theoretical grid operating parameters.

5. The solid-state transformer functional test system based on the low-power energy feed-to-drive method according to claim 1, characterized in that, The test of the solid-state transformer under test based on the first, second, and third electrical parameters includes: According to the actual functional test requirements, the second electrical parameter is compared with the first electrical parameter. If the comparison is successful, the function of the solid-state transformer under test is verified by combining the first electrical parameter and the third electrical parameter according to the actual functional test requirements. Otherwise, it indicates that the power grid simulation signal is distorted and an error is reported.

6. The solid-state transformer functional test system based on the low-power energy feed-to-drive method according to claim 5, characterized in that, The comparison of the second electrical parameter with the first electrical parameter according to actual functional test requirements includes: The target comparison parameters are determined according to the actual functional test requirements. The parameter difference between the target comparison parameter in the second electrical parameter and the target comparison parameter in the first electrical parameter is obtained. If the parameter difference is less than the preset difference, the comparison is successful; otherwise, the comparison fails.

7. The solid-state transformer functional test system based on the low-power energy feed-to-drive method according to claim 5, characterized in that, The verification of the function of the solid-state transformer under test, based on actual functional test requirements and in conjunction with the first and third electrical parameters, includes: Based on the actual functional test requirements, the corresponding functional test indicators are determined. The parameter data corresponding to the functional test indicators are extracted from the first electrical parameter and the third electrical parameter. The actual test values ​​corresponding to the functional test indicators are obtained based on the parameter data. If the actual test values ​​all meet the preset functional qualification standards, the functional test is judged to be qualified; otherwise, it is judged to be unqualified.

8. The solid-state transformer functional test system based on the low-power energy feed-to-drive method according to claim 1, characterized in that, The functional test module is also communicatively connected to the energy compensation module for issuing energy compensation commands. The energy compensation module is electrically connected to the power grid operating condition simulation module for outputting compensation energy to compensate the power grid operating condition simulation module according to the energy compensation commands.

9. The solid-state transformer functional test system based on the low-power energy feed-to-drive method according to claim 2, characterized in that, The power grid operating condition simulation module also integrates a control and protection submodule, which is used to monitor and regulate the operating status of the low-voltage AC port, the low-voltage DC port, and the medium-voltage AC port.

10. A functional test method for solid-state transformers based on the low-power energy feed-to-drive method, applicable to the functional test system for solid-state transformers based on the low-power energy feed-to-drive method as described in any one of claims 1-9, characterized in that, include: Simulates power grid operating conditions based on actual functional test requirements and outputs power grid simulation signals; It performs regulation in response to the grid analog signal and outputs the regulated signal; The first electrical parameter at the output port of the power grid operating condition simulation module, the second electrical parameter at the output port of the solid-state transformer under test, and the third electrical parameter at the input port of the solid-state transformer under test are collected, and the function of the solid-state transformer under test is tested based on the first electrical parameter, the second electrical parameter, and the third electrical parameter.

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