Real-time implementation of sliding mode controller for standalone microgrid systems for voltage and frequency stabilization

Abstract

This paper presents for stabilizing the output voltage and frequency of the hybrid source microgrid system (HSMG) and standalone solar photovoltaic microgrid system (SAPV), under varying source and loading conditions. An HSMG system consists of a solar, wind and battery system incorporated with a solar boost converter, wind rectifier/boost converter and bidirectional converter, respectively. These different dc level outputs are applied to the multiple input dc–dc converter for obtaining the constant dc level and then converted into three-phase power with suitable inverters. The source-side converters are designed to obtain the maximum output irrespective of the input conditions with PI controllers. The multiple input dc–dc converter controls the dc link voltage with the well-designed proportional, proportional integral, proportional integral derivative controller. The three-phase inverter is premeditated to obtain the constant voltage and frequency even under varying load patterns. The tuning of the PID controller is incorporated with Ziegler Nichols’s technique to reduce the frequency deviation and steady-state error. A SAPV microgrid system is developed with a high-capacity solar system incorporated with two-stage power conversion. Stage 1 and 2 are constant dc/constant ac obtained using suitable converters incorporated with an adaptive controller. The sliding mode controller (SMC) is an adaptive controller that performs better in dynamic operations. In this work, SMC maximizes the solar output and stabilizes the DC voltage using an appropriate PWM pulse to the boost converters. Also, the output voltage and frequency are maintained constant during the different operating situations. All simulations are carried out in MATLAB. PID and SMC controllers are implemented to the HSMG and SAPV microgrid systems in the OPAL-RT environment to validate the results in real-time applications respectively. The different operating conditions are tested for both the systems and the results prove that the chosen controllers are more suitable for these applications.