CURRENT CONTROLLED VOLTAGE SOURCE INVERTER UNDER SATURATION-ANALYSIS AND NEW ALGORITHMS

摘要

This paper presents the dynamic analysis of the currents during controller saturation of a three phase Voltage Source Inverter (VSI), connected to the Point of Common Coupling (PCC). Closed-form solutions of the VSI currents are obtained using a piecewise linear, state-space averaged model of the VSI under the linear and saturated regimes of the current controller. Using these results, two new algorithms are proposed which best improve current dynamics during controller saturation, while simultaneously limiting the reference voltage within the modulation range. This ensures that no lower order harmonics are introduced in the VSI currents, resulting in simplification of the ripple filter design. Simulation results obtained are compared with those from existing algorithms. The simulation model includes device switching and uses multi-rate sampling, for the physical plant and controller, to reflect major non-idealities of a practical system. It is shown that the proposed algorithms result in decoupled current control and faster current dynamics.