Direct current control strategy of SVG based on dual sequence dq coordinates under asymmetric load condition

Abstract

In the case of asymmetric loads of power grid, load currents are composed of four components: positive sequence active and reactive components and negative sequence active and reactive components that can pollute the power grid with harmonics and reactive power and interrupt the normal operation of power grid. Therefore, increasing numbers of static var generators (SVGs) are used to stabilize the power grid. In this study, a new type of current compensation control strategy of a three-phase three-wire SVG under an asymmetric load is proposed. According to the symmetric component method and dual dq synchronous transformation theory, the load currents are transformed into four components under dual dq coordinates. Each component is compensated separately by the SVG Simultaneously, the proportional-limiter method is adopted to minimize the harmonics from the SVG by optimizing the waveform of the modulation wave and limiting its amplitude. Finally, the validity and feasibility of the control strategy are verified by simulation and experimental results.