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.