Abstract
Grid-connected inverters (GCI) are commonly used in PV system applications to generate a regulated AC current to feed into the grid. Transformerless inverters are the most advanced inverters that are used in industry, which provide efficiency with smaller size and lower cost. This paper proposes a grid-connected single-phase transformerless inverter with the technology of common ground and the virtual DC bus concept. In this topology, the grid neutral is connected directly to the PV ground, which generates a constant common mode voltage (CMV), thus leading to the elimination of the leakage current caused by the PV array’s parasitic capacitance. The proposed inverter has a buck–boost circuit with a flying capacitor to generate the DC bus for a negative power cycle, four switches, and two diodes. A unipolar sinusoidal pulse width modulation (SPWM) technique is used which reduces the output filter requirements. In addition, only one switch carries the load current during the active states of both the negative and positive power cycle, thus minimizing the conduction losses. One more advantage presented in the proposed inverter is its ability to charge the flying capacitor during all operation states due to the existence of the buck–boost circuit. Design and theoretical calculations were conducted in this paper to optimize the losses. Moreover, the PSIM simulation was used to validate the proposed topology inverter, verify the performance by showing leakage current elimination, and achieve unipolar voltage in the output bus. The simulation results show a peak efficiency of 98.57% for a 2 kW inverter, which agrees with the theoretical calculations.
Highlights
In recent decades, the growth in renewable energy systems has increased exponentially
This paper proposes a new transformerless inverter topology based on the common ground concept and virtual DC bus
This leads to the minimization of the size of the flying capacitor (330 μF) as compared with similar inverters that utilize the flying capacitor concept, and it reduces the current spikes experienced by the other topologies that charge the flying capacitor directly without limiting the current, as achieved in the proposed topology by the buck–boost inductor
Summary
The growth in renewable energy systems has increased exponentially. The galvanic isolation serves to i the overall system safety to achieve the corresponding safety standards required f or a low-frequency AC side transformer. PV systems; at the same time, these transformers lead to bulky inverters with overall system safety to achieve the corresponding safety standards required for grid-tied. PV systems; at theefficiency same time, [5,6] These transformers lead toresidential bulky inverters with higher cost ers utilized due to their lower cost, market, highertransformerless efficiency, and smaller size and have lower been efficiency [5,6]. The galvanic isolation serves to improve the overall system safety to achieve the corresponding safety standards required for gridtied PV systems; at the same time, these transformers lead to bulky inverters with higher cost and lower efficiency [5,6]. (CMV), which leads to high leakage current and high electromagnetic interference tionally, the leakage current can be decreased the0126-1-1
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