Optimization of Active and Reactive Power Dispatch among Multi-Paralleled Grid-Connected Inverters Considering Low-Frequency Stability

Abstract

This paper presents an optimization method of active and reactive power dispatch among multi-paralleled voltage source grid-connected inverters (GCIs) considering stability enhancement in low-frequency range. DQ impedance model of GCI with outer power control loop, inner current control loop and phase-locked loop (PLL) is first established. Then, effects of active and reactive power references on terminal impedance frequency characteristics of GCI, e.g., passivity, are theoretically derived. It's found that high active power reference tends to destabilize the power system, and high reactive power reference tends to stabilize the power system. On the basis of it, an active and reactive power dispatch method for stability enhancement in low-frequency range is proposed, where more/less active power and less/more reactive power are allocated to the GCIs with narrow/wide bandwidths of power control loop and PLL. Simulation is performed on a five-GCIs-based power system to validate effectiveness of the proposed active and reactive power dispatch method considering low-frequency stability enhancement.