Multi-Objective VSC Intelligent Control Strategy Applied to PV-BESS-Grid System for Single-Phase Critical Load Applications

In this research paper a single-phase, Multi-Mode operated combination of solar Photo Voltaic (PV), Battery Energy Storage System (BESS) connected to grid through a Voltage Source Converter (VSC) has been realised. The operation Modes include Grid Connected Mode (GCM), Islanded Mode (IM) and Night Mode (NM) respectively. GCM and IM involve power generation from PV whereas in NM there is no power generated from the PV side. An intelligent master control strategy is proposed for smooth operation at steady state and seamless transition from mode to mode respectively. Least Mean Fourth (LMF), fourth-order adaptive filter algorithm is utilised to extract the fundamental weight component of the load current. A synchronising controller is utilised to isolate/reconnect the utility mains smoothly on grid-outage/grid-restoration. Proportional Resonant (PR) compensator based direct VSC current control strategy is employed to regulate the grid current under surplus/deficit power situations of PV when in GCM operation of VSC. The Multi-Loop Inductor current feedback with Load Current Feedforward (MILF) PR controller with harmonic compensator (HC) voltage control strategy is utilised to maintain load voltage amplitude, frequency and quality when at IM. A dual-loop control strategy ensures regulation of DC link and charging/discharging of BESS under surplus/deficit power situations respectively, when the system operates in GCM. State-Of-Charge (SOC) of BESS gets monitored through the same dual-loop DC/DC converter control so as to protect it from overcharging/deep-discharging conditions. The proposed system stability is analysed in frequency domain. The prime objective of the proposed system is to supply continuous power to critical loads under different operating conditions. The performance of the proposed system is realised in MATLAB environment in Discrete-Time Frame (DTF) using Simulink and Sim Power System (SPS) toolboxes when the converters are operated with a switching frequency of 10kHz, respectively.