A Non-isolated Hybrid Boost Three Level DC-DC Converter with High Step-up Conversion Ratio

Nowadays renewable energy sources are increasingly used to meet the world’s increasing demand for energy. In grid connected photovoltaic (PV) generation systems, a single PV array can supply lower dc voltage. In order to connect PV array to the grid, the voltage has to be boosted to higher levels that is demanded by the grid side. A hybrid boost three level dc-dc converter based on traditional single phase three level diode clamped inverter can be used to connect low voltage PV array to the high voltage grid. Only one inductor, two capacitors in series, and those power switches and diodes, which are needed to establish the topology with high voltage gain. Pulse width modulation (PWM) control method is used for the control of power switches. Power switches of this converter works with duty cycles closer to 0.5. This hybrid three level dc-dc converter works with high gain without a transformer or coupled inductor. In addition, voltages across the capacitors in series are balanced in both steady and dynamic states. Therefore capacitor voltage balancing circuitry can be avoided. Also, blocking voltages of the power switches are half of the output dc voltage. This hybrid converter is suitable for PV generation systems connected to the grid with parallel- connected low-voltage PV arrays.