Control Strategy and Dynamic Characteristics of Voltage Source Converter Based on Time-Varying Voltage Unbalance

The fluctuation amplitude of the output power and DC side voltage will be directly affected by the change in voltage unbalance (UVF) on AC side of the converter. In order to further analyze the influence of UVF on the output characteristics of voltage source converter (VSC), The positive sequence, negative sequence and zero sequence decomposition of voltage and current are done by symmetric component method, and the mathematical model and output power expression of VSC are derived; the current is decomposed into active component and reactive component, on this basis, variable parameters are introduced into the instruction current to provide the comprehensive expression of the instruction current under different control objectives; afterwards, the relational expressions between UVF and active power, reactive power, DC voltage are derived receptively, and the relation-ships between UVF, variable parameters and active power, reactive power, DC voltage are elaborated in detail. Simulation experiments were carried out in PSCAD software, and the experimental results were consistent with the theoretical analysis.