Improving Power Quality of a Hybrid Grid-Connected Photovoltaic–Wind Microgrid Using Shunt Active Power Filter and Distribution Static Synchronous Compensator

Abstract

Unbalanced voltage and harmonics are major challenges in a microgrid. Single- and two-phase loads and short circuit can make unbalanced voltage. Besides, nonlinear loads create harmonic components in the grid. Thus, compensating both of the unbalanced voltage and harmonic distortion is necessary. Otherwise, they could cause low power quality, resonance, and stability issues. The present paper suggests a combination of distribution static synchronous compensator (DSTATCOM) and shunt active power filter (SAPF) to address the unbalanced voltage and harmonic pollution in hybrid grid-connected microgrid. A four-wire distributed static synchronous compensator has been adopted to deal with the negative- and zero-sequence components of the microgrid, extracting these components by using second-order generalized integrator (SOGI). To solve the harmonic issue, a SAPF is presented to dynamic compensation of grid current and voltage harmonic components in addition to DSTATCOM. The SAPF relies on estimating the fundamental frequency positive-sequence component (FFPSC) of the load current by applying the second-order sequence filter (SOSF). Since combining the reference signals of voltage balancer and harmonic eliminating at one controller is impossible, two independent devices are presented. Although both of the equipment have a same conception, their control and operation are different. So, simultaneous incorporation of distributed static synchronous compensator and SAPF for mitigating the unbalancing and distortion in the grid-connected microgrid based on hybrid solar and wind power is the work’s novelty. Some merits of this scheme include simple structure, fast real-time controller, low computational burden, and more effective operation. Robustness and effectiveness of such very simple scheme are evaluated by simulation in MATLAB/Simulink environment. Simulation report demonstrates that the total harmonic distortion (THD) of grid voltage and current decrease well under 1.44% and 2.33%, respectively. Meanwhile, the voltage unbalance factor (VUF) of negative and zero sequence of grid voltage reduces to 1.1% and 0%, respectively.