Grid tied solar micro-converter with optimizer-mode operation for weak-grid operation

There is a critical need to make use of renewable energy sources such as solar energy to develope efficient and economical solutions to the energy crisis that many countries are facing. This need is worsened in developing countries by the presence of weak or unreliable electrical grids. A popular solution is the use of solar based single phase micro-inverters feeding AC power to the grid. However, they require a stable grid and input current pulsation at twice the line frequency is an inherent disadvantage. This limitation is typically remedied by a large electrolytic input capacitor that increases the cost and reduces the efficiency of the converter. This paper therefore proposes a dual mode flyback based hybrid converter that can support both a grid tied mode and islanded mode operation to extract maximum power from the solar PV source at all times. It is also designed to employ active power decoupling to draw constant input current with reduced filter size at the terminals of the PV panel in both AC and DC output power modes. The ability of the proposed converter to produce both DC and AC output allows flexibility of operation in environments where the grid may not be available for as high as 80% of sunlight hours while maintaining the advantages of micro-inverters. This paper presents the analysis, P-SIM simulation as well as the experimental validation of the proposed converter system on a 240 watt prototype. The results obtained validate that this approach can be applied to large distributed generation networks of micro inverters in weak grid communities.