Power quality and reactive power of water electrolyzers supplied with thyristor converters

Industrial water electrolyzers apply direct current in kiloampere ranges. Therefore, rectifiers are typically based on thyristors despite the high amplitude current fluctuation excited by the rectifier. This paper studies the effect of thyristor rectifiers on the power quality of the electrolyzer stack and the supplying AC grid. The thyristor bridge excites high current and power fluctuation causing additional losses in the electrolytic cells. Further, the both AC supply side and DC output power factors are low especially under partial load conditions. The reactive power is divided into phase shift and distortion components. In the case of thyristor rectifier without any passive filter components the distortion reactive power component is dominating. The simulated results are supported by the power factor measurements of an industrial alkaline water electrolyzer. It is proposed that electrolyzer stack manufacturers should give requirements for the DC power quality to maximize the stack energy efficiency and lifetime.