D-STATCOM for a Distribution Network with Distributed PV Generation

Abstract

Power quality in an AC power distribution system is reduced by nonlinear loads which draw non-sinusoidal current. When this distorted current interacts with the line impedance of the distribution network (the grid), the system voltage becomes distorted which could adversely affect other electrical devices connected to the grid. In the traditional grid, this is compensated at the substation by the utility. Adding PV into the distribution system can complicate the situation when power flow reverses due to excess generation resulting in back-feeding into the grid. It has been proposed that the photovoltaic inverter should actively improve the power quality by compensating harmonic and reactive current. However, this adds complexity and cost to the inverter as well as reduces the inverter reliability. To maintain high power quality in the distribution system, it is necessary to develop a means to compensate for the reactive and harmonic currents locally. This paper investigates the use of a distribution static synchronous compensator (D-STATCOM) for harmonic power compensation in a distribution network. The proposed topology is based on a matrix converter topology (MC) which is controlled using model predictive control (MPC) which enables inductive energy storage instead of requiring electrolytic capacitors that have well-known failure modes. Compensating the harmonic current in the distribution system improves the overall reliability of the grid. Simulation is performed using MATLAB/Simulink to investigate the performance and capability. It is envisioned that the device can be deployed and dispatched by the utility as needed in the distribution network to prevent upstream-propagation of the harmonic current, which could lead to transformer overheating and other deleterious effects.