flexible voltage regulator, on-load voltage regulation, power electronic converter, stepless voltage regulation, reactive power compensation, power electronic transformer, Applications of electric power, TK4001-4102

As the increasing proportion of renewable energy and power electronic devices in the power grid, voltage fluctuations are becoming frequent. In response to the current voltage regulation and reactive power compensation requirements of the distribution network, a new type of flexible on-load tap changer is designed that integrates traditional transformers and power electronic converters. This novel transformer can simultaneously provide voltage regulation and reactive power compensation capabilities. Firstly, the principles of voltage regulation and reactive power compensation on the series and parallel sides of the power electronic converter are analyzed. Then, considering the operation of the on-load tap changer, two series parallel voltage and reactive power coordination control strategies based on minimum voltage amplitude and minimum active power loss are proposed to achieve continuous voltage regulation while providing maximum range of reactive power. Finally, the structural rationality of the on-load tap changer and the correctness of the voltage and reactive power coordination control strategy are verified through simulation and experiments. The stepless voltage regulation and reactive power compensation under multiple objectives can be realized by the voltage and reactive power coordinated control strategy for flexible on-load tap changer.