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为了满足交联聚乙烯(XLPE)电缆对检测电源的要求,设计了一种采用两个高频高压变压器作为升压变压器的超低频高压电源。详细阐述了系统的硬件设计及软件控制策略,优化了变压器的结构及绝缘,大大缩小了变压器的体积及质量,减小了变压器的分布参数。并根据电路拓扑的特点,首次采用先进的三闭环控制技术,动态地对高频部分及低频部分的输出进行了监控与调整,减小了高频高压变压器分布参数对电源性能的影响。同时对采样数据采取了分段化的处理方法,大大减小了程序的计算量,使它能够应用于单片机控制。采用所设计的35kV/0.1Hz电源对电气特性等效于XLPE电缆的高压电容(1.5μF)进行了实验,其总谐波畸变率(THD)为2.76%,完全满足IEEE 400.2标准对总谐波畸变率<5%的要求。实验结果验证了理论的可行性与正确性。
In order to meet the requirements of XLPE cables for testing power supply, an ultra-low frequency high voltage power supply using two high-frequency high-voltage transformers as step-up transformers was designed. The system hardware design and software control strategy are elaborated. The structure and insulation of the transformer are optimized. The size and quality of the transformer are greatly reduced and the distribution parameters of the transformer are reduced. According to the characteristics of the circuit topology, the advanced three-closed-loop control technology is adopted for the first time to monitor and adjust the output of the high-frequency part and the low-frequency part dynamically to reduce the influence of the distribution parameters of the high-frequency high voltage transformer on the power performance. At the same time, the sampling data has been taken a segmentation approach, which greatly reduces the amount of computation, so that it can be applied to SCM control. A 35kV / 0.1Hz power supply was designed to test the high-voltage capacitor (1.5μF) with the same electrical characteristics as the XLPE cable. The total harmonic distortion (THD) was 2.76%, which completely meets the requirements of IEEE 400.2 standard for total harmonic Distortion rate <5% of the requirements. The experimental results verify the feasibility and correctness of the theory.