Topology Derivation Method of Common-Ground Transformerless Single-Phase Inverters Based on Graph Theory

Common-ground transformerless single-phase inverters are widely used in the photovoltaic generation systems because of no common mode leakage current, but there is no systematic theory on topology derivation of them. Therefore, a general topology derivation method of the double-grounded single-phase inverters based on graph theory is proposed. The common-ground topologies can be derived by determining the properties of the common-ground topologies and inserting switches, inductors, and capacitors to the undirected graphs, respectively. The topologies with four nodes, four switches, three inductors, and three capacitors are taken as an example to illustrate the derivation method. One of the derived topologies is taken as an example to illustrate the operating principle of the inverter, which has high voltage gain. The system is a single-stage system, so efficiency of the system can be improved. The reference voltage expression is simplified to reduce the digital signal processor (DSP) computation time. Finally, simulation and experimental results verify the theoretical analysis.