Author: Huang Zhengfeng AMETEK Programmable Power Sector E-mail: wanner. As the installed capacity of photovoltaic power generation systems in the power system continues to increase, the overall grid has higher and higher requirements for the quality and capability of photovoltaic inverters. Conventional electrical characteristics such as over-voltage, over-under-frequency, anti-islanding and other projects are based on verifying the inverter's tolerance to the grid and not allowing the introduction of unsafe hazards, while new requirements such as low voltage ride through, high Projects such as voltage traversal and reactive power injection further require the inverter to compensate and support the abnormal conditions of the power grid to help improve the quality of the power grid. Powerful grid simulators help R&D and testers easily test these emerging features in the lab without having to build complex test benches, no additional dedicated equipment, and no need to change cable connections every time you change test conditions Therefore, the workload of testing and verification can be greatly reduced, and the capital investment and space occupation of additional equipment can also be saved. The intelligent inverter needs to be adjusted in real time according to the condition of the power grid. It can provide certain support when the grid is unstable, including the ability to inject inductive reactive power and capacitive reactive power, which is the working capability of the grid simulator used for testing. Put forward higher requirements. The AMETEK Group's California Instruments Mx/RS Series Grid Simulator supports bi-directional power input and output up to 100% of rated power in the 16-500Hz operating frequency range, and supports capacitive and inductive reactive power injection. Four quadrant power supply. Figure 1 AMETEK California Instruments Mx/RS Series Grid Simulator The construction of the entire test environment does not require the intervention of other loads or power supplies. The Mx/RS can fully absorb the power from the inverter, which also enables the Mx/RS to monitor the operating status of the inverter in real time, which can be preset. Safety limits to ensure that the inverter is within normal operating range. The rated voltage of domestic industrial power is 380V line voltage, that is, 220V phase voltage. Therefore, the general grid simulator provides a phase voltage position of 300V to cover the test voltage requirements. At the same time, the grid simulator generally supports overcurrent output capability within a certain range, that is, when the voltage is lower than 300V, the output current can be increased accordingly, so that full power output can be achieved within the corresponding voltage range. Take the RS90 of California Instruments as an example, its full power is 90KVA, the current output capability is 100A at 300V, and when the voltage drops to 240V or below, the maximum current can reach 125A, that is, it is in the range of 240V-300V. It is capable of achieving 90KVA full power, while at less than 240V the output power capability decreases with voltage drop (see Figure 2). Figure 2 RS90 power coverage in 300V gear If you need to simulate a phase voltage of 110V in some areas, the grid simulator of the 300V gear will only be able to supply ~50% or even lower power. In order to solve this problem, California Instruments' Mx/RS series power supply is equipped with two range gears of 150V and 300V, so that users can switch to 150V when they need to simulate a 110V power grid, thus greatly expanding their low voltage. Power coverage at the time (see Figure 3). Figure 3 Power coverage of the RS90 dual-range gear (the area where the shadow area is extra) The input power of California Instruments' Mx/RS series when connected to an inverter is consistent with the range of its output power, that is, the above power capability curve is also suitable for receiving inverter backfill. When the inverter is deployed in a photovoltaic power station, the rated voltage of the grid terminal needs to be determined according to the actual situation of the local power station. Commonly used 400V, 600V, 800V line voltage levels, corresponding to phase voltage is 230V, 346V, 461V and so on. As a key device in the power station, the inverter needs to be able to cope with various grid abnormalities. High voltage ride-through is a test project to simulate grid voltage surge faults. Figure 4 is a typical voltage curve envelope diagram of high voltage ride through, no longer than 0.5 seconds duration, voltage amplitude not higher than 130% of the rated value, and the subsequent duration is no longer than 9.5 seconds, the voltage amplitude is not high At 120% of the rated value, the inverter should not operate off-grid and have the ability to continuously regulate active power and the ability to inject reactive current into the power system during this period. Figure 4. A typical voltage curve envelope for high voltage ride through Different countries and regions, different manufacturers will have different details of high voltage ride-through requirements for specific inverters, but basically the test equipment will be required to provide controllable output of up to 130%-140% inverter rated voltage, if It is an inverter with 600V line voltage (346V phase voltage), which requires grid simulator output up to 840V line voltage (485V phase voltage); if it is 800V line voltage (461V phase voltage) inverter, it needs grid simulator output up to 1120V line voltage (647V phase voltage). For this type of testing needs, the grid simulator needs to provide a higher voltage output range. In addition to the original 400V phase voltage option, California Instruments' Mx/RS series power supplies also offer special ultra-high voltage options that extend the output voltage to 500V, 600V or even 650V phase voltage, fully covering high voltage crossovers from different customers. Test requirements. With the optional ultra-high voltage option, a transformer of the preferred design is added inside the housing of the Mx/RS power supply. The precisely debugged output characteristics ensure the maximum range of output impedance matching, thus maximally avoiding oscillations. At the same time, the internal heat dissipation channel and over-temperature protection circuit of the power supply have been redesigned to provide such high-voltage and full-power output in the same machine size. The performance of the entire machine maintains the consistent performance of AMETEK California Instruments brand AC power. Taking the -XVC650 option as an example, the power supply can still support 125% overcurrent capability in the 650V range, enabling full power output in the 525V to 650V range. Figure 5 shows the output voltage and current capability curve of the RS90-XVC650. Figure 5 Output V/I curve of RS90-XVC650 It is worth mentioning that these high-voltage options are an additional third range, customers can still use the original 150V and 300V range, so that a single power supply can provide sufficient power coverage over a very wide voltage range. The inverter technology is continuously improving, and the requirements for the corresponding test equipment are also continuously improved. The four-quadrant working capability and the output voltage capability of up to 650V phase voltage have become the necessary capabilities to meet the current many inverter test requirements. At the same time, as a powerful grid simulator, it should be able to provide sufficient power coverage over as wide a range of voltages as possible to enable testing of as many inverters as possible. AMETEK's California Instruments Mx/RS series power supply products fulfill these requirements and provide strong support for customer testing. AMETEK Group is headquartered in Pennsylvania, USA with annual sales of approximately $4.5 billion. The group is currently divided into two business divisions, electronic instrumentation and electromechanical division. Focus on providing differentiated and value-added products and services to help customers solve problems while achieving outstanding shareholder value. AMETEK Programmable Power Supply (http://) is a subsidiary of AMETEK and currently includes Sorensen, ELGAR, AMREL, and California Instruments. It has the world's broadest line of program-controlled power supplies, providing customers in a variety of fields. s solution. 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