Modelling and analysis of shunt-connected voltage source converter for voltage dip mitigation

Abstract

Distribution Static Synchronous Compensator (D-STATCOM) is a Custom Power Device based on a Voltage Source Converter (VSC) shunt connected to the grid. By injecting a controllable current, it can improve the quality of the load current, e.g. compensating harmonic currents or °uctuating currents. If a D-STATCOM is equipped with an energy storage, the system is also called Energy Storage Equip- ment STATCOM (E-STATCOM). This thesis focuses on the E-STATCOM for mitigating voltage dips. A short descrip- tion of power quality problems has been done, with particular attention a in-depth study on voltage dip problem and its solution has been conducted. Afterwards the control system for the E-STATCOM has been derived. The vector current- and voltage-controllers have been designed and their behaviour has been studied. The impact of controller bandwidths and of model parameters has been investigated. The dual vector current- voltage-controllers (DVCC DVVC) have been designed in order to improve the performance con the control system also under unbalanced conditions. All results are veri¯ed in MATLAB and simulated in PSCAD/EMTDC. The system has been tested to mitigate both balanced and unbalanced voltage dips, with several types of loads.