There is an upward trend that human activities involve more electric power nowadays and for years to come. And we will soon be facing shortage of electricity supply if we rely solely on non-renewable power generation from fossil fuels such as coals. Renewable energy generation has proven effective in meeting the demand. At the same time it has brought about a few issues to existing electricity infrastructure such as complex power flow due to distributed generations and unstable grid voltage and/or frequency profiles due to local generation and intermittent nature of renewable energy sources such as solar photovoltaicand wind power
