Off-grid inverter parallel operation test system

Abstract

The invention discloses an off-grid inverter parallel operation test system, and the system comprises an isolation type programmable DC power supply module which is used for providing an independent DC power supply for a plurality of inverters; the dynamic load device comprises a plurality of independently controlled load units and is used for simulating the operation states of the inverter under different load conditions; the data acquisition device is used for acquiring output parameters of the plurality of inverters; the fault injection and fault tolerance device is used for injecting a fault signal to test and analyze the fault tolerance performance of the system in the parallel operation process of the plurality of inverters; the upper computer system is connected with the data acquisition device, the dynamic load device, the fault injection and fault tolerance device and the isolated programmable direct-current power supply module, and is used for carrying out data processing and display on the parallel operation performance of the inverter; the plurality of inverters simulate off-grid parallel operation in a parallel connection mode; and the parallel operation performance of the inverter is tested and analyzed in real time through the upper computer system.

Description

Technical Field

[0001] The present application relates to the field of power connection, and in particular to an off-grid inverter parallel testing system. Background Art

[0002] With the rapid development of renewable energy technologies, off-grid power generation systems such as photovoltaic and wind power have gained widespread adoption in remote areas and specialized applications. As a key device for converting DC power into AC power, the parallel operation performance of inverters is directly related to the stability and reliability of the entire system. In off-grid environments, operating multiple inverters in parallel can effectively improve the capacity and redundancy of the power supply system. However, due to voltage, frequency, and phase differences when multiple inverters are connected in parallel, achieving stable, synchronized parallel operation of each inverter to ensure system stability, current sharing, and efficiency has become a key technical challenge in inverter R&D and testing.

[0003] Currently, most systems used to test the performance of parallel inverters on the market are single-inverter test platforms, which cannot fully simulate the actual operation of multiple inverters in an off-grid environment. Furthermore, existing inverter test equipment often lacks flexible load simulation devices and fault injection mechanisms, making it difficult to comprehensively evaluate the performance of parallel inverter systems in dynamic environments. Consequently, these shortcomings in the test system significantly slowed down the development of parallel inverter control algorithms and the algorithm optimization process. Summary of the Invention

[0004] A first aspect of the present application provides an off-grid inverter parallel testing system method, comprising:

[0005] Isolated programmable DC power supply module, used to provide independent DC power to multiple inverters;

[0006] Dynamic load device, which includes multiple independently controlled load units and is used to simulate the operating state of the inverter under different load conditions;

[0007] A data acquisition device for collecting output parameters of multiple inverters, including voltage, current, power factor and harmonic content;

[0008] Fault injection and fault tolerance device, used to inject fault signals during the parallel operation of multiple inverters to test and analyze the fault tolerance performance of the system;

[0009] A host computer system connected to the data acquisition device, the dynamic load device, the fault injection and fault tolerance device, and the isolated programmable DC power supply module, for processing and displaying data on the parallel performance of the inverter;

[0010] Multiple inverters, the L lines and N lines of the multiple inverters are connected together, the DC input end of the inverter is connected to the isolated programmable DC power supply module, and the AC output end is connected to the dynamic load device, for simulating off-grid parallel operation;

[0011] The parallel operation performance of the inverter is tested and analyzed in real time through the host computer system.

[0012] Optionally, the dynamic load device includes a plurality of independent controllable load units.

[0013] Optionally, the host computer system includes a data processing module and a display module, the data processing module is used to analyze the phase synchronization error between inverters, and the display module is used to display key parameters such as voltage, current and power factor in real time.

[0014] Optionally, the fault injection device includes an inverter grounding fault injection module, an inverter AC side output overvoltage fault injection module, and an inverter AC side overcurrent fault injection module, and fault injection is achieved by controlling the resistor or power supply in the fault injection device through the host computer.

[0015] Optionally, the system also includes a stand-alone performance development mode, a parallel performance development mode, and a fault and diagnosis development mode. The stand-alone performance development mode and the parallel performance development mode include a manual control mode and an automatic test mode, which are used to analyze various states of the inverter during the research and development process.

[0016] Optionally, the parallel performance development mode supports user-defined dynamic load changes, realizes load mutation, load periodic fluctuation and load random change by setting algorithms, and processes and analyzes the collected data in real time to evaluate the performance indicators of the inverter parallel system under dynamic load changes.

[0017] Optionally, the performance indicators include:

[0018] Analyze the differences between the output voltage amplitude and frequency of each inverter;

[0019] Analyze the data difference between the output current of each inverter and the load current;

[0020] Calculate the active power and reactive power of each inverter and determine whether the load distribution is balanced;

[0021] Perform harmonic analysis to obtain the harmonic content of the system.

[0022] Optionally, the system includes a communication module for remote data transmission and monitoring between the host computer system and the inverter parallel system.

[0023] Optionally, the system further includes a current sensor and a voltage sensor. The output L line of a single inverter is connected to the current sensor In, where n=1, 2...n. The L line and N line connected in parallel are connected to the voltage sensor. The L line connected in parallel is connected to the current sensor I. The output signals of the current sensors I and In are connected to a data acquisition device, and the output signal of the voltage sensor is connected to a data acquisition device. The inverter further includes a communication output Sn, where n=1, 2...n, and is connected to the data acquisition device. The communication output Sn includes voltage data and current data collected from inside the inverter.

[0024] Optionally, the system further includes a plurality of controllable relays, and a single controllable relay is connected in series with a single inverter via an output line L.

[0025] It can be seen from the above technical solutions that this application has the following advantages:

[0026] 1. The isolated programmable DC power supply provides DC power for the inverter. The isolation mode is used to isolate each inverter from the others, simulating the off-grid and parallel state of the inverter, thus realizing the parallel operation of the inverter.

[0027] 2. During operation, the load simulation device and fault injection mechanism in the system randomly inject fault signals into the inverter, comprehensively evaluate the performance of the inverter parallel system under a dynamic load environment, promptly discover system problems, and improve system reliability.

[0028] 3. The data acquisition device can collect the operating status of the inverter, and the host computer system monitors and analyzes the operating status of the inverter in real time to ensure the stability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in this application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of this application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 This is a schematic diagram of the power connection of the off-grid inverter parallel test system provided in this application. DETAILED DESCRIPTION

[0031] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0032] Example 1: This application provides an off-grid inverter 06 parallel test system, please refer to Figure 1 The system includes:

[0033] The isolated programmable DC power supply 05 module is used to provide independent DC power to multiple inverters 06, for example, see Figure 1 , inverter 06 includes inverter 1, inverter 2...inverter n.

[0034] The isolated programmable DC power supply 05 is an efficient and reliable power source, providing DC power to multiple inverters 06. By utilizing digital control technology and integrated circuit design, it achieves rapid voltage response and precise regulation. Inverter 06 converts the DC power provided by the isolated programmable DC power supply 05 into AC power, providing power support when disconnected from the grid.

[0035] An isolated DC power supply includes multiple controllers that regulate and control the power supply's switching. Inverters 06 are connected in parallel, integrating multiple power supplies with a single controller, or using multiple controllers to control different power switches, to independently power multiple inverters 06.

[0036] The isolated programmable DC power supply 05 and multiple inverters 06 provide DC power. The inverters 06 are connected in parallel to achieve isolation between each inverter 06, truly simulating actual off-grid parallel operation to ensure effective power distribution and stable operation of each inverter 06.

[0037] The dynamic load device 03 includes multiple independently controlled load units for simulating the operating state of the inverter 06 under different load conditions;

[0038] The Dynamic Load Device 03 is a test device used to simulate equipment operating conditions under various conditions. It consists of multiple independent load cells that can be controlled independently to simulate different loading conditions. Each load cell provides a specific load, allowing for precise evaluation.

[0039] Through the control system, dynamic load device 03 adjusts the load type, conditions, and size according to a preset program. A rapid switching simulator is used to achieve instantaneous load changes, including sudden increases, decreases, and periodic fluctuations. These sudden increases, decreases, and periodic fluctuations are simulated by the host computer module using the load simulator's rapid switching capabilities to simulate the sudden load changes encountered in the inverter 06 parallel system. By controlling the load simulator to rapidly switch load size or type at preset time points, the response speed and stability of the inverter 06 parallel system are tested.

[0040] The dynamic load device 03 can perform accurate testing and analysis under different load conditions, providing an important tool for evaluating the performance of the inverter 06, ensuring that the inverter 06 can achieve the expected results in actual operation, and improving the accuracy and reliability of system testing.

[0041] The data acquisition device 02 is used to collect output parameters of the plurality of inverters 06, including voltage, current, power factor and harmonic content;

[0042] The data acquisition device 02 is a device used to collect, store, and process data. After the data acquisition device 02 collects data, it will process the data. The output L lines of multiple inverters 06 are first connected to N. The output line L of the inverter 06 is connected to the current sensor I. The L and N lines are connected to the voltage sensor. The L line is connected to the current sensor I. The current sensor I and In output are connected to the data acquisition device 02. The voltage sensor output is connected to the data acquisition device 02. The inverter 06 includes multiple communication outputs S connected to the data acquisition device 02. For example, see Figure 1 Communication outputs include S1, S2, ...Sn. Voltage and current data are collected internally by inverter 06, and power is calculated based on these data. Harmonic content is the ratio of the RMS value of harmonic voltage or current within a certain range to the RMS value of the fundamental wave. Harmonic content is a criterion for determining AC power stability. Harmonic analysis is performed using the collected data to determine the harmonic content.

[0043] The data acquisition device 02 collects the output voltage, current, power and other parameters of the inverter 06 in real time, monitors the circuit conditions of multiple inverters 06 in real time, and ensures the safety and stability of power supply.

[0044] The fault injection and fault tolerance device 04 is used to inject fault signals during the parallel operation of multiple inverters 06 to test and analyze the fault tolerance performance of the system;

[0045] The fault injection and fault tolerance device 04 is used to test and evaluate the system's fault tolerance capabilities. By introducing faults into the system to simulate potential fault conditions that may occur during actual operation, the system's response and recovery capabilities are tested. In the inverter 06 system, fault injection may include simulating circuit breakers, short circuits, and other fault conditions. Once the fault is injected, the fault tolerance device detects the fault information and quickly switches control strategies to achieve stable operation after the fault.

[0046] Fault injection includes ground fault injection on Inverter 06, overvoltage fault injection on the AC side of Inverter 06, and overcurrent fault injection on the AC side of Inverter 06. The ground fault on Inverter 06 involves the grounding resistor within the fault injection device, which is adjusted via host computer control. Overvoltage fault injection on the AC side of Inverter 06 involves the AC power supply within the fault injection device, with output control achieved via host computer commands. The fault injection device includes current and voltage sensors on the output cables, which provide feedback signals to the fault injection device controller for closed-loop control.

[0047] The fault injection and fault tolerance device 04 can significantly improve the system's power supply continuity. Fault injection allows testing of the system's response and recovery capabilities under various fault conditions, thereby improving system reliability. The fault tolerance device can quickly switch control schemes after a fault occurs, ensuring stable operation and avoiding system downtime or performance degradation caused by the fault.

[0048] The host computer system 01 is connected to the data acquisition device 02, the dynamic load device 03, the fault injection and fault tolerance device 04, and the isolated programmable DC power supply 05 module, and is used to process and display the parallel performance of the inverter 06;

[0049] The host computer system 01 is used to monitor and control remote systems. It establishes a communication connection with the data acquisition device 02, dynamic load device 03, fault injection and fault tolerance device 04, and isolated programmable DC power supply 05 modules, and executes control commands sent by the host computer. The slave computers also include the data acquisition device 02, dynamic load device 03, fault injection and fault tolerance device 04, and isolated programmable DC power supply 05. After receiving data from the slave computers, the host computer processes and analyzes the data, which can include parameters such as voltage, current, power factor, and harmonic content. The processed data is displayed through a visual interface.

[0050] It acquires and processes various data in real time, providing real-time monitoring, data collection, remote control, alarm and fault diagnosis, data analysis, and optimization. Processed data is displayed through a visual interface, providing an intuitive understanding of system status. The host computer system 01 improves system efficiency and reliability through automated monitoring and control, and centralized monitoring and management facilitates system maintenance.

[0051] Multiple inverters 06, L lines and N lines of multiple inverters 06 are connected together, the DC input end of the inverter 06 is connected to the isolated programmable DC power supply 05 module, and the AC output end is connected to the dynamic load device 03, for simulating off-grid parallel operation;

[0052] The L lines and N lines of multiple inverters 06 are connected together, and the DC input end of the inverter 06 is connected to the isolated programmable DC power supply 05 module, so that the multiple inverters 06 are in a parallel relationship. The AC output end is connected to the dynamic load device 03. The inverter 06 converts the DC power at the DC input end into AC power, providing stable AC power for the dynamic load device 03.

[0053] By connecting the L lines and N lines of multiple inverters 06 together and connecting them to the isolated programmable DC power supply 05 and the dynamic load device 03, the actual off-grid parallel operation is effectively simulated, thereby improving the stability of the system power supply.

[0054] The parallel performance of the inverter 06 is tested and analyzed in real time through the host computer system 01.

[0055] The data collected by the data acquisition device 02 is transmitted to the host computer system 01 through the communication output S. The host computer system 01 obtains and processes the operating data of the inverter 06 in real time, understands the operating status of the inverter 06 in real time through the visual interface, realizes parallel performance analysis and harmonic content analysis in voltage and current, and timely discovers potential problems by testing the efficiency of the parallel system, so as to adjust the inverter 06 through remote control.

[0056] The host computer system 01 effectively manages and optimizes system performance through real-time monitoring, data acquisition, remote control and other functions, thereby improving the system's operating efficiency and reliability.

[0057] In this embodiment, an isolated programmable DC power supply 05 provides DC power to inverter 06. This isolation ensures that each inverter 06 is isolated from the others, simulating the off-grid and parallel operation of inverter 06 and enabling parallel operation of inverter 06. During operation, the system's load simulation device and fault injection mechanism randomly inject fault signals into inverter 06, comprehensively evaluating the performance of the inverter 06 parallel system under dynamic load conditions, promptly identifying system problems and improving system reliability. Data acquisition device 02 can collect the operating status of inverter 06, and host computer system 01 monitors and analyzes the operating status of inverter 06 in real time to ensure system stability.

[0058] In the second embodiment, in the off-grid inverter parallel test system, the dynamic load device 03 includes a plurality of independent controllable load units.

[0059] These load units simulate different load conditions, such as resistance, inductance, and capacitance. By adjusting the combination and parameters of these load units, various complex load conditions can be simulated to test the performance and stability of the off-grid inverter 06. In the parallel test system, multiple dynamic load devices 03 are used to simulate different load conditions. For example, one load device is set to simulate a pure resistive load, another load device to simulate an inductive load, and another load device to simulate a capacitive load. In this way, the performance of the off-grid inverter 06 under different load conditions can be comprehensively tested. The dynamic load device 03 is also used to test the dynamic response performance of the off-grid inverter 06. For example, the parameters of the load device can be suddenly changed to simulate a sudden load change, thereby testing the rapid response capability of the off-grid inverter 06.

[0060] The dynamic load device 03 simulates various complex load conditions in the off-grid inverter parallel test system, helping the system to comprehensively evaluate the performance and stability of the off-grid inverter 06.

[0061] In the third embodiment, in the off-grid inverter parallel test system, the host computer system 01 includes a data processing module and a display module. The data processing module is used to analyze the phase synchronization error between the inverters 06, and the display module is used to display key parameters such as voltage, current and power factor in real time.

[0062] In the off-grid inverter parallel test system, host computer system 01 is responsible for data processing and analysis, and also provides an intuitive display interface for real-time monitoring and evaluation of inverter 06's performance. The data processing module of host computer system 01 is used for phase synchronization error analysis, and the display module of host computer system 01 is used for data display, data playback, and user data interaction. The following is a detailed introduction to host computer system 01:

[0063] Phase synchronization error analysis collects the output signals of each inverter 06, calculates the phase difference between them, analyzes the magnitude and trend of the phase synchronization error, and determines the synchronization performance between the inverters 06. Based on a preset threshold, the phase synchronization error is evaluated to determine whether it is within an acceptable range. The analyzed data is stored in a data logging and storage system. The data logging and storage system records key parameters during the test, such as voltage, current, and power factor, and stores the data in a database to facilitate subsequent data analysis and report generation.

[0064] The display module displays key parameters such as voltage, current, and power factor for each inverter in real time. This data is presented in the form of charts or digital dashboards, providing an intuitive understanding of the system's current operating status. When historical data is needed for comparison, it can be searched in the data log and repository. By comparing data from different time periods, performance trends of the inverter can be analyzed.

[0065] In this embodiment, the data processing module and display module of host computer system 01 together constitute the core of the parallel test system for off-grid inverter 06. They not only provide powerful data processing capabilities but also, through an intuitive display interface, monitor the operating status of inverter 06 in real time, monitor and evaluate inverter 06's performance in real time, detect potential faults or abnormalities, and trigger an alarm mechanism when an abnormality is detected, thereby ensuring the accuracy and efficiency of the test.

[0066] In the fourth embodiment, in the off-grid inverter parallel test system, the fault injection device includes an inverter 06 ground fault injection module, an inverter 06 AC side output overvoltage fault injection module, and an inverter 06 AC side overcurrent fault injection module. The fault injection is achieved by controlling the resistor or power supply in the fault injection device through the host computer.

[0067] In the off-grid inverter parallel test system, the fault injection device includes the inverter 06 ground fault injection module, the inverter 06 AC side output overvoltage fault injection module, and the inverter 06 AC side overcurrent fault injection module. These modules are controlled by the host computer to simulate and inject faults.

[0068] The Inverter 06 Ground Fault Injection Module simulates a ground fault in Inverter 06. A ground fault on either the DC or AC side of Inverter 06 triggers the system's ground fault protection mechanism, potentially causing equipment downtime or damage. This module simulates a ground fault by injecting current or voltage into the ground loop of Inverter 06. This involves changing the resistance of the ground loop or directly connecting a ground wire to Inverter 06. The Inverter 06 Ground Fault Injection Module tests the response capability and effectiveness of Inverter 06's protection mechanisms in the event of a ground fault, ensuring that the fault can be promptly isolated in actual operation to prevent further damage.

[0069] The Inverter 06 AC Output Overvoltage Fault Injection Module simulates an overvoltage condition on the Inverter 06 AC output. Overvoltage, caused by grid fluctuations, sudden load changes, and other factors, poses a threat to the Inverter 06 and other electrical equipment. This overvoltage fault is simulated by adjusting the voltage at the Inverter 06 output beyond its normal operating range. This can also be achieved by increasing the external power supply voltage or adjusting Inverter 06's internal control parameters. The Inverter 06 AC Output Overvoltage Fault Injection Module tests the Inverter 06's self-protection capabilities against overvoltage conditions and assesses system stability.

[0070] The Inverter 06 AC Side Overcurrent Fault Injection Module simulates excessive output current on the AC side of Inverter 06. Overcurrent can be caused by a short circuit, excessive load, or other factors, potentially leading to overheating or even damage to the device. By adding an additional current load to the output circuit of Inverter 06, the output current exceeds the rated value, simulating an overcurrent fault. The Inverter 06 AC Side Overcurrent Fault Injection Module verifies Inverter 06's protection measures in overcurrent situations, verifying whether the overcurrent protection activates promptly and whether Inverter 06 can safely handle overcurrent events without damaging internal components.

[0071] In this embodiment, the fault injection device in the off-grid inverter 06 parallel test system ensures the reliability and safety of inverter 06. By simulating various potential fault conditions, the performance and protection mechanisms of inverter 06 can be effectively evaluated, providing reliable data for the optimized design and safe operation of inverter 06.

[0072] In a fifth embodiment, the off-grid inverter parallel test system also includes a stand-alone performance development mode, a parallel performance development mode, and a fault and diagnosis development mode. The stand-alone performance development mode and the parallel performance development mode include a manual control mode and an automatic test mode, which are used to analyze the various states of inverter 06 during the development process. These modes support the development process of inverter 06 by simulating different operating conditions and fault conditions, helping the system test and optimize the performance of inverter 06.

[0073] In manual control mode, the system automatically starts and stops the inverter, adjusts its operating parameters, and observes its performance under different conditions, helping to understand its basic operating characteristics and response behavior. In automatic control mode, the system automatically executes a series of predefined test procedures to evaluate the inverter's performance indicators, such as efficiency, stability, and output quality. Automatic testing can be repeated to ensure consistent and repeatable test results.

[0074] Parallel Performance Development Mode In Manual Control Mode In this mode, multiple inverters 06 can be controlled simultaneously to simulate parallel operation and analyze the interaction and coordination between the inverters 06. Parallel Performance Development Mode In Automatic Control Mode In this mode, the automatic test program will take into account the coordinated operation of multiple inverters 06 and evaluate the comprehensive performance of the entire system, including load sharing, synchronous operation and failover.

[0075] The fault and diagnosis development mode simulates various possible fault conditions, such as ground fault, overvoltage, overcurrent, etc., through a fault injection device to test the fault detection and response mechanism of inverter 06; at the same time, it collects the operating data of inverter 06 under normal and fault conditions, and uses advanced data analysis technology to perform fault diagnosis and performance evaluation to identify potential problems and make improvements.

[0076] In this embodiment, the off-grid inverter 06 parallel test system's multiple development modes provide comprehensive support for the R&D of inverter 06. From stand-alone to parallel, and then to fault diagnosis, they together form a powerful test system for improving inverter 06's performance.

[0077] In Example 6, in an off-grid inverter parallel test system, the parallel performance development mode supports user-defined dynamic load changes. By setting an algorithm to implement load mutations, load periodic fluctuations, and random load changes, the collected data is processed and analyzed in real time to evaluate the performance indicators of the inverter 06 parallel system under dynamic load changes. The following is a detailed introduction to the parallel performance development mode:

[0078] Sudden load changes simulate significant load changes over a short period of time, such as the sudden addition or removal of high-power equipment. This type of load change can verify the responsiveness and stability of the Inverter 06 parallel system in the face of sudden load changes. Cyclic load fluctuations simulate the cyclical load changes encountered in actual operation by setting a cyclically changing load pattern, such as a sine wave or other periodic function. This test assesses the parallel system's adaptability and efficiency to long-term cyclical load changes. Random load changes use a random number generation algorithm to create unpredictable load change patterns, simulating various non-cyclic load fluctuations that may be encountered in actual operation. This test provides a more comprehensive assessment of the parallel system's reliability.

[0079] During the test, the system collects and processes data in real time, including key parameters such as voltage, current, and frequency. This data is used to evaluate the parallel system's performance under varying load conditions, such as output stability, response time, and conversion efficiency. Analysis of the collected data provides a comprehensive understanding of the parallel system's overall performance under dynamic load variations.

[0080] In this embodiment, the parallel performance development mode within the off-grid inverter 06 parallel test system is used to simulate and evaluate the performance of the inverter 06 parallel system under various dynamic load variations. Based on the test results, the control of the inverter 06 is optimized to improve the performance of the inverter 06 under complex dynamic load environments. By simulating various extreme and complex load variations, the parallel system is ensured to operate stably and reliably after actual deployment, maintaining excellent performance even under the most adverse conditions.

[0081] Example 7: In the off-grid inverter parallel test system, the detection of performance indicators is the key to ensure the stable operation of the system. The performance indicators tested include:

[0082] Analyze the differences between the output voltage amplitude and frequency of each inverter 06;

[0083] In an off-grid inverter parallel test system, analyzing the differences in output voltage amplitude and frequency between each inverter 06 is an important step in evaluating its performance and synchronization. The following is a detailed analysis of this performance indicator:

[0084] Differences in voltage amplitude directly impact the stability and efficiency of a parallel system. Inconsistent output voltage amplitudes across inverters 06 can lead to uneven load distribution, impacting overall system performance. Using precision measurement equipment, such as a digital power meter, we measure the output voltage amplitude of each inverter 06 and analyze this data to identify any differences. If significant differences in voltage amplitude are detected, we adjust the inverter 06's control parameters to minimize these differences and ensure that the output voltages of all inverters 06 are as close as possible.

[0085] Frequency differences can cause phase shifts between inverters 06, which in turn affects the power quality and stability of the entire system. In a parallel system, use a frequency meter or the frequency monitoring function built into each inverter 06 to measure the output frequency of each inverter 06. This data can be used to assess frequency synchronization. If the frequency difference is large, adjust the inverter 06's phase-locked loop settings to improve frequency matching and ensure that all inverters 06 operate at the same frequency.

[0086] The voltage amplitude and frequency difference is achieved by comparing the amplitude and frequency of the output voltage of each inverter 06 to evaluate the synchronization between them and identify possible phase deviation or frequency inconsistency problems in the parallel system.

[0087] Analyze the data difference between the output terminal current of each inverter 06 and the load terminal current;

[0088] In the off-grid inverter parallel test system, when analyzing the data difference between the output current of each inverter 06 and the load current, it is necessary to pay attention to the influence of conversion efficiency, load characteristics and other factors.

[0089] Impact of conversion efficiency: Due to losses in components like resistors and inductors within the inverter 06, as well as energy lost during switching, actual conversion efficiency is typically less than 100%. This means that for the same output power, the input current must be greater than the output current to compensate for these losses. The output current is equal to the input current multiplied by the inverter 06's conversion efficiency, so conversion efficiency directly affects the ratio of input to output current.

[0090] Impact of Load Characteristics: When the load increases, inverter 06 needs to provide more energy to ensure stable operation, so the input current also increases accordingly. However, due to differences in conversion efficiency and load characteristics, the increase in input current is not always proportional to the increase in output current. Changes in load characteristics may cause changes in the operating state of inverter 06, thereby affecting the relationship between input and output currents.

[0091] In addition to conversion efficiency and load characteristics, the relationship between inverter 06's input and output currents may also be affected by other factors, such as power quality, ambient temperature, and inverter 06's capacity and type. These factors can cause performance changes in inverter 06's internal components, thereby affecting the relationship between input and output currents. By comprehensively considering conversion efficiency, load characteristics, and other possible influencing factors, we can more accurately analyze and understand the data discrepancy between inverter 06's output current and load current.

[0092] Calculate the active power and reactive power of each inverter 06 and determine whether the load distribution is balanced;

[0093] Active power P can be calculated from the voltage RMS value U, the current RMS value I, and the cosine value of the phase difference Φ between them. The calculation formula is: P = UIcosΦ.

[0094] Reactive power Q reflects the energy exchange between the inductor or capacitor components in the circuit and the power supply. It does not consume energy. The calculation formula is: Q = UIsinΦ.

[0095] By accurately calculating active and reactive power, power resources can be managed and allocated more effectively, ensuring efficient and economical operation of the system.

[0096] Load balance is determined by adjusting the active and reactive power of inverters 06. Active and reactive power are distributed by controlling the output voltage of parallel inverters. When all inverters 06 distribute power evenly, the system load is balanced. When a particular inverter 06 delivers too much or too little power, the load is unbalanced. When the load is unbalanced, the resistance in inverter 06 is increased or decreased to adjust the output voltage and achieve equal power distribution. When the output voltage is stable and the output power of each inverter 06 is similar, the load is considered balanced.

[0097] By adjusting the output voltage of the inverter 06, the output power of the inverter 06 is evenly distributed. By regulating the power of the inverter 06 to determine whether the load is balanced, the load state of the inverter 06 can be determined more accurately, thereby ensuring the stable operation of the inverter 06 under unbalanced load conditions.

[0098] Perform harmonic analysis to obtain the harmonic content of the system.

[0099] Harmonic content is the proportion of frequency components other than the fundamental component in inverter 06. This is determined by collecting voltage or current data using a data acquisition device and calculating the ratio of the effective value of the voltage or current to the effective value of the fundamental. Harmonic content is a criterion for determining AC power stability. Analysis of harmonic content can identify nonlinear loads or fault sources in the power system, such as transformer saturation and capacitor damage, allowing for targeted maintenance and repairs to ensure stable power system operation.

[0100] In this embodiment, the performance index detection of the off-grid inverter 06 parallel test system covers multiple aspects. Through comprehensive detection and analysis of performance indicators, the stable operation of the off-grid inverter 06 parallel system is ensured.

[0101] In the eighth embodiment, the off-grid inverter parallel test system further includes a communication module for remote data transmission and monitoring between the host computer system 01 and the inverter 06 parallel system.

[0102] Through the communication module, host system 01 monitors the operating status of inverter 06 in real time, including key parameters such as output power, current, and voltage. The host computer sends control commands to the inverter 06 parallel system through the communication module, while also receiving operating data and status information from inverter 06. The communication module ensures real-time data exchange between host system 01 and the inverter 06 parallel system. The data collected by the communication module can be used to analyze and optimize the operating performance of the inverter 06 parallel system. For example, operating parameters can be dynamically adjusted based on real-time data, automatically executing preset control strategies to adapt to varying power demands and environmental conditions to ensure stable system operation. If a fault occurs in the inverter 06 parallel system, the communication module quickly transmits the fault information to host system 01, which then remotely shuts off the power supply, identifies and locates the problem, and initiates appropriate maintenance measures.

[0103] In this embodiment, the communication module of the off-grid inverter 06 parallel test system not only supports real-time communication and data transmission but also enables system monitoring. It is a key component for ensuring efficient and stable operation of the inverter 06 parallel system. The communication module enables efficient data transmission and processing in the off-grid inverter parallel test system, enhancing the system's intelligence, security, and reliability.

[0104] In the ninth embodiment, the off-grid inverter parallel test system further includes a current sensor and a voltage sensor. The output L line of a single inverter 06 is connected to the current sensor In, where n=1, 2...n. The L line and N line after parallel connection are connected to the voltage sensor. The L line after parallel connection is connected to the current sensor I. The output signals of the current sensors I and In are connected to the data acquisition device 02, and the output signal of the voltage sensor is connected to the data acquisition device 02. The inverter 06 also includes a communication output Sn, where n=1, 2...n, and is connected to the data acquisition device 02. The communication output Sn includes voltage data and current data collected from the inside of the inverter 06.

[0105] The output L line of each inverter 06 is connected to a current sensor In, where n = 1, 2, ..., n. These sensors measure the output current of each inverter 06. The L and N lines of all inverters 06 are connected in parallel to a voltage sensor. This connection facilitates measurement of the total voltage of the entire system. The parallel L lines are connected to a total current sensor I, which measures the total output current of the entire system.

[0106] The output signals of the current sensors I and In and the output signals of the voltage sensor are connected to the data acquisition device 02. This enables the system to collect and analyze the current and voltage data from each inverter 06 and the entire system.

[0107] Inverter 06 includes communication outputs Sn, where n = 1, 2, ... n. These outputs are connected to data acquisition device 02, enabling data acquisition device 02 to receive more detailed performance information about inverter 06. Furthermore, voltage and current data collected from within inverter 06 are transmitted to host computer system 01 via communication outputs Sn.

[0108] In this embodiment, the off-grid inverter 06 parallel test system can accurately measure and monitor the output current and voltage of each inverter 06, as well as the total current and voltage of the entire system, through these circuit connections, providing strong data support for the test system and ensuring the effective operation and performance evaluation of the system.

[0109] In the tenth embodiment, the off-grid inverter parallel test system further includes a plurality of controllable relays 07 , and a single controllable relay 07 is connected in series with a single inverter 06 via an output line L.

[0110] In an off-grid inverter parallel test system, controllable relay 07 automatically adjusts output based on current and voltage fluctuations to maintain stable circuit or system operation. For example, in a power system, controllable relay 07 can automatically adjust generator output power based on grid load fluctuations to ensure stable power supply. In the event of an overload, short circuit, or other abnormality in a circuit, controllable relay 07 can quickly cut off power to prevent equipment damage. For example, in a circuit system, if a device or equipment overheats, the relay will automatically cut off power to prevent damage.

[0111] When maintenance or upgrades are required on a particular inverter 06, the corresponding controllable relay 07 can be controlled to disconnect it from the system without affecting the normal operation of other inverters 06. In the parallel test system, controllable relays 07 are dynamically adjusted based on the load requirements of the inverters 06, thereby controlling the activation and deactivation of different inverters 06 and improving system efficiency and stability.

[0112] In this embodiment, by controlling the on / off state of a single controllable relay 07, it is possible to determine whether to connect or disconnect a single inverter 06 from the system. Even if one or two inverters 06 are damaged, the system can continue to operate, providing flexibility and convenience for parallel testing of inverters 06. If an abnormality occurs in the circuit system, the relay automatically cuts off the power supply, protecting the circuit safety and preventing equipment damage.

[0113] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0114] In the several embodiments provided in this application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are merely schematic. For example, the division of units is only a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interface, device or unit, which can be electrical, mechanical or other forms.

[0115] Units described as separate components may or may not be physically separate, and components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of these units may be selected to achieve the purpose of this embodiment according to actual needs.

[0116] In addition, the functional units in the various embodiments of the present application may be integrated into a single processing unit, or each unit may exist physically separately, or two or more units may be integrated into a single unit. The aforementioned integrated units may be implemented in the form of hardware or software functional units.

Claims

1. An off-grid inverter parallel test system, characterized in that: The system comprises: Isolated programmable DC power supply module, used to provide independent DC power to multiple inverters; A dynamic load device, which includes multiple independently controlled load units, is used to simulate the operation of the inverter under different load conditions; A data acquisition device for collecting output parameters of multiple inverters, including voltage, current, power factor and harmonic content; Fault injection and fault tolerance device, used to inject fault signals during the parallel operation of multiple inverters to test and analyze the fault tolerance performance of the system; A host computer system, connected to the data acquisition device, the dynamic load device, the fault injection and fault tolerance device, and the isolated programmable DC power supply module, for processing and displaying data on the parallel performance of the inverter; A plurality of inverters, L lines and N lines of the plurality of inverters are connected together, the DC input end of the inverter is connected to the isolated programmable DC power supply module, and the AC output end is connected to the dynamic load device, for simulating off-grid parallel operation; The parallel operation performance of the inverter is tested and analyzed in real time through the host computer system.

2. The off-grid inverter parallel test system according to claim 1, characterized in that: The dynamic load device comprises a plurality of independently controllable load units.

3. The off-grid inverter parallel test system according to claim 1, characterized in that: The host computer system includes a data processing module and a display module. The data processing module is used to analyze the phase synchronization error between inverters, and the display module is used to display key parameters such as voltage, current and power factor in real time.

4. The off-grid inverter parallel test system according to claim 1, characterized in that: The fault injection device comprises an inverter grounding fault injection module, an inverter AC side output overvoltage fault injection module, and an inverter AC side overcurrent fault injection module. The fault injection is achieved by controlling the resistor or power supply in the fault injection device through the host computer.

5. The off-grid inverter parallel test system according to claim 1, characterized in that: The system also includes a single-machine performance development mode, a parallel performance development mode, and a fault and diagnosis development mode. The single-machine performance development mode and the parallel performance development mode include a manual control mode and an automatic test mode, which are used to analyze various states of the inverter during the research and development process.

6. The off-grid inverter parallel test system according to claim 5, characterized in that: The parallel performance development mode supports user-defined dynamic load changes, realizes load mutations, load periodic fluctuations and load random changes by setting algorithms, and processes and analyzes the collected data in real time to evaluate the performance indicators of the inverter parallel system under dynamic load changes.

7. The off-grid inverter parallel test system according to claim 6, characterized in that: The performance indicators include: Analyze the differences between the output voltage amplitude and frequency of each inverter; Analyze the data difference between the output current of each inverter and the load current; Calculate the active power and reactive power of each inverter and determine whether the load distribution is balanced; Perform harmonic analysis to obtain the harmonic content of the system.

8. The off-grid inverter parallel test system according to claim 1, characterized in that: The system comprises a communication module, which is used for remote data transmission and monitoring between the host computer system and the inverter parallel system.

9. The off-grid inverter parallel test system according to claim 1, characterized in that: It also includes a current sensor and a voltage sensor. The output L line of a single inverter is connected to the current sensor In, where n=1, 2...n. The L line and N line connected in parallel are connected to the voltage sensor. The L line connected in parallel is connected to the current sensor I. The output signals of the current sensors I and In are connected to a data acquisition device, and the output signal of the voltage sensor is connected to the data acquisition device. The inverter also includes a communication output Sn, where n=1, 2...n, and is connected to the data acquisition device. The communication output Sn includes voltage data and current data collected from inside the inverter.

10. The off-grid inverter parallel test system according to claim 1, characterized in that: It also includes a plurality of controllable relays, wherein a single controllable relay is connected in series with a single inverter via an output line L.

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