When an inverter is tested with a motor emulator, most of the power circulates in a loop consisting of inverter, emulator, and DC-DC converter. Only the device losses are compensated from the grid, so they usually do not exceed 20% of the circulating power. Most commonly, an isolated bi-directional DC-DC converter is used between the back ends of motor emulator and inverter. In this work, the bi-directional DC-DC converter is replaced by a three phase high frequency system between two PWM (AC-DC) converters. Furthermore, two frequency current components are used independently based on two different reference frames: the 60 Hz is utilized for power trading with the grid, whereas 2 kHz is employed for power circulation. The high frequency link is especially beneficial, since it reduces the size of isolation transformer drastically. The effectiveness of the control algorithm is supported by computer simulation and experimental results.

中文翻译：

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电机仿真系统中两种频率的功率循环方法


当使用电机仿真器测试逆变器时，大部分功率在逆变器、仿真器和 DC-DC 转换器组成的环路中循环。仅设备损耗由电网补偿，因此通常不超过循环功率的20%。最常见的是，在电机仿真器和逆变器的后端之间使用隔离式双向 DC-DC 转换器。在这项工作中，双向 DC-DC 转换器被两个 PWM (AC-DC) 转换器之间的三相高频系统取代。此外，基于两个不同的参考系独立使用两个频率电流分量：60Hz用于与电网进行电力交易，而2kHz用于电力循环。高频链路尤其有益，因为它大大减小了隔离变压器的尺寸。计算机仿真和实验结果支持了控制算法的有效性。