Parallel diode‐clamped linear converter for withstand test and partial discharge measurement of electric equipment

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.