High-voltage withstand tests are essential for electric equipment like power transformers, electric cable lines, gas insulated switchgears etc. The partial discharge (PD) measurement for such equipment under applied high voltage is also required at the same time. Pulse Width Modulation (PWM)-based variable frequency power supply (VFPS) finds wide applications in the series resonance high-voltage testing circuits. However, the steep rising and falling voltage edges in the PWM process will produce large amount of partial discharge interference in a wide spectrum range, which will confuse the real partial discharge signal of the device and lead to the wrong estimation of the insulation status. This paper proposes a new VFPS based on the high-efficiency linear power amplifier without PD interference. The topology and principle of the VFPS are given and discussed. A prototype rated at 232 V/35 A was designed and constructed to verify the feasibility of the proposed VFPS. Physical experiments were carried out on the prototype.

中文翻译：

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电气设备耐压试验和局部放电测量用并联二极管钳位线性变换器

电力变压器、电缆线路、气体绝缘开关设备等电气设备必须进行高压耐压试验，同时还需要对此类设备进行高压下的局部放电（PD）测量。基于脉宽调制（PWM）的变频电源（VFPS）在串联谐振高压测试电路中得到广泛应用。但PWM过程中陡峭的上升沿和下降沿会产生大量宽频谱范围内的局部放电干扰，混淆器件真实的局部放电信号，导致对绝缘状态的错误估计。本文提出了一种基于无PD干扰的高效线性功率放大器的新型VFPS。给出并讨论了 VFPS 的拓扑结构和原理。设计并建造了额定电压为 232 V/35 A 的原型，以验证所提出的 VFPS 的可行性。在原型机上进行了物理实验。