A Blended Improved H5 Topology With ILQG Controller to Augment the Performance of Microgrid System for Grid-Connected Operations

The development of the world demands on the progress of electricity operation and quality enhancement. Microgrid (MG) is a solution that manages the additional need of electricity. The MG generates electricity mostly from renewable energy sources, e.g. solar, wind and hydro. Most renewable energy sources require energy storage system as they are highly unpredictable in nature. An inverter is needed to convert that stored DC power to AC. The presence of a capacitor within the grid provides a galvanic connection that varies the common mode (CM) voltage of the inverter. Thus, the leakage current as well as the total harmonic distortion (THD) of the grid voltage and current increases. The increase of the leakage current hampers the safe operation of the MG. Now-a-days transformerless inverter is gaining more attention because of high efficiency, low cost, less weight and the capability of eliminating the high frequency component from the inverter CM voltage. In addition, a controller inclusion with a transformerless inverter can maintain a near-seamless performance. This paper proposes a blended technique of an improved H5 topology with an Integral Linear Quadratic Gaussian (ILQG) controller for grid-connected MG operations, that reduces the inverter leakage current by keeping the CM voltage constant. Thus it has the capability to reduce the THD of voltage and current. A comparative analysis has been carried out between this technique and existing topologies with different modulation techniques that helps to find out the most optimum inverter package to eliminate the leakage current and reduce the THD of grid voltage and grid current to almost zero.