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This study introduces a new single phase nine-level inverter using two capacitors and a single DC source. Voltage imbalances in the capacitors are eliminated using two control algorithms namely charging algorithm and discharging algorithm. The charging algorithm is used to change the inverter switching states when the measured voltage across the capacitors is less than the prescribed value. Alternatively, if the voltage across the capacitors is greater than the set value, the discharging algorithm determines the switching pattern of the inverter switches. The proposed voltage balancing algorithm is very simple to implement and makes the proposed inverter attractive for industrial applications. An extensive comparison of the proposed inverter is made against other topologies proposed in the literature in terms of the components used. The proposed inverter is tested in both standalone and grid connected modes. The proposed inverter is simulated and implemented as a prototype in the laboratory. Experimental results obtained from the prototype confirm the high-quality transient performance of the proposed inverter in terms of its dc capacitor voltage balancing capability.

In this paper, a novel single-phase cascaded grid connected multilevel inverter (MLI) is proposed for feeding power to microgrid from renewable energy sources (RESs). The proposed inverter is capable of feeding power to microgrid with low total harmonic distortion (THD). The proposed inverter consists of two H bridge inverters connected in cascade, namely, upper and lower inverters. The upper inverter is fed from photovoltaic (PV) array through a DC–DC boost converter, whereas the lower inverter is fed from wind turbine (WT) coupled to permanent magnet synchronous generator (PMSG) through an uncontrolled rectifier and DC–DC boost converter. The upper inverter operates at high frequency, whereas the lower inverter operates at fundamental frequency. To extract maximum power from the WT and PV array, a sliding mode control based maximum power point tracker (MPPT) is used. The proposed inverter is connected to the single phase 230 V, 50 Hz grid, and the control algorithm is implemented in the SPARTAN 3A digital signal processor (DSP) board. The proposed inverter is simulated using matlab/simulink, and detailed experimental results are presented to show the efficacy of the proposed inverter under different environmental conditions.

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There is a strong trend in the photovoltaic (PV) inverter technology to use transformerless topologies in order to acquire higher efficiencies. This paper presents a singlephase five-level grid connected PV inverter with a novel dual reference modulation technique. Two reference signals identical to each other with an offset equivalent to the amplitude of the rectified inverted sine carrier signal were used to generate PWM signals. The inverter consists of a fullbridge inverter and an auxiliary circuit comprising four diodes and a switch. The inverter produces output voltage in five levels: zero, +1/2V dc , V dc , -1/2V dc and -V dc . The validity of the proposed inverter is verified through simulation.