Multilevel common‐ground inverter with voltage boosting for PV applications

Abstract

Nowadays, transformer-less Photovoltaic-based grid-connected inverters are more popular in renewable energy application due to their reduced size, cost, and high efficiency. However, the absence of galvanic isolation leads to the flow of leakage current in such system hindering personal safety, and deteriorating power quality. Therefore, this paper presents a five-level transformer-less inverter topology for PV applications with less component count and reduced complexity. The proposed inverter topology completely eliminates the common mode leakage current. Besides, the proposed topology has an inherent capability to boost the voltage without using any magnetic component or boosting circuit, and is based on the principle of switched/auxiliary capacitor. The proposed topology do not have any limitation of modulation index since the auxiliary capacitors are naturally balanced, hence less complex or no dedicated control scheme is required for balancing/regulating the auxiliary capacitor voltages. In order to verify the performance of the proposed inverter topology, a laboratory prototype is developed which confirms the operation, and feasibility of the proposed inverter. Results depicting the output voltage, load current, and voltage across the auxiliary capacitor are presented for various operating conditions. Further, simulation results depicting the leakage current in the proposed, H5, and H6 topologies are included. Finally, a quantitative comparison study is done, highlighting the benefits of the proposed inverter topology regarding boosted voltage, elimination of leakage current, and reduced component count. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Topology review of doubly grounded transformer‐less single‐phase inverters

“…Therefore, the other method is that the combination of the converters with different polarity of the output voltage can be used to construct the doubly grounded inverters [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39]. In addition, energy storage elements, that is, flying capacitors and flying inductors, can be used to generate positive and negative constant voltage or current by semiconductors, so doubly grounded topologies using energy storage elements can be deduced [40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55]. Therefore, categorization of doubly grounded transformer-less single-phase inverters can be obtained in Figure 2.…”

Three‐phase transformerless photovoltaic inverter without common mode leakage current

“…The core loss of L 4 can be calculated as 0.126 W from (24), Table 1 and Reference 27. Thus, the total core loss of inductors is 23.986 W. In addition, the total copper loss of inductors can be calculated as 12.814 W from (25) and Table 1. Therefore, the total loss of inductors is 36.8 W.…”

“…Single‐phase common‐ground‐type PV inverters have become a research hotspot in recent years. Grounds of the grid and PV array are connected directly, so the common‐ground‐type inverters can completely eliminate the CMLC of PV system 23–25 . However, there are no TPT common‐ground‐type PV inverters.…”

“…Grounds of the grid and PV array are connected directly, so the common-ground-type inverters can completely eliminate the CMLC of PV system. [23][24][25] However, there are no TPT common-ground-type PV inverters.…”

Hybrid bypass technique to mitigate leakage current in the grid-tied inverter

“…Due to the increase in levels the overall stress on the power devices is decreased and the power quality is also improved. Similar to this another multilevel inverter is proposed in [21] which carries the same benefits of eight switch five level inverter. A five-level inverter that employs series parallel switching conversion along with common ground technique is presented in [22].…”