Single Phase Solar Inverter with Inertia Emulation

Synchronous machines or alternators form the core of the power generation capability in the traditional electrical power system. They have a rotating flywheel which enables them to impart stability to the grid. With the increasing penetration of distributed renewable energy sources, DC to AC conversion systems has gained huge popularity. Proper stable operation of the electrical grid depends on the fact that the alternator has a rotating flywheel(mechanical inertia), which can quickly absorb or release energy in a controlled manner. The flywheel is not available for a traditional DC to AC converter i.e. inverter used in renewable energy conversions. This is where the idea of an inverter with emulated inertia can play a significant role. It can convert energy efficiently from DC sources to AC for further transmission of power through the grid and still retain all the features of a traditional alternator that help in stabilising the grid. In this paper, focus has been put on single phase inverters as single phase inverters on home rooftops form a huge segment of the future renewable energy generation prospect. Moreover, renewable energy sources always have an element of unpredictability associated with it. Injection of this unpredictable amount of power into the grid makes the grid more unstable. So, with steady increase in the use of inverters powered by renewable energy sources, such inertia emulation ability is essential for grid-connected inverters to keep the stability of the grid intact, especially in rapidly changing atmospheric conditions where the amount of available renewable energy keeps varying. To solve this problem, the idea of single phase solar inverter with inertia emulation is proposed here. Calculations have been shown here to estimate the capacity of energy storage required for proper operation. The proposed inverter is controlled through synchronous reference frame based control method instead of popularly used hysteresis based methods, which allows for superior quality power to be injected to the grid.

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