An improved control strategy for the three‐phase grid‐connected inverter with space vector pulse‐width modulation (SVPWM) is proposed. When the grid current contains harmonics, the d ‐ and q ‐axis grid currents will be interacted, and then the waveform quality of the grid current will be poorer. As the reference output voltage cannot directly reflect the change of the reference grid current, the dynamic response of the grid‐connected inverter is slow. In order to solve the aforementioned problems, the d ‐ and q ‐axis grid currents in the decoupled components of the grid current controller can be substituted by the d ‐ and q ‐axis reference grid currents, respectively. The operating principles of the traditional and proposed control methods are illustrated. Experimental results for a 15‐kVA three‐phase grid‐connected inverter with SVPWM verify the theoretical analysis. Compared with the traditional control strategy, the grid‐connected inverter with the improved control strategy has a high waveform quality of the grid current, small ripple power and fast dynamic response.

As there is shoot-through problem and common mode leakage current in conventional transformerless grid-connected PV inverters, a transformerless grid-connected PV inverter without common mode leakage current and shoot-through problems is proposed. The proposed inverter consists of a buck-boost converter and a dual-buck half-bridge inverter, so there is no shoot-through problem in the proposed inverter. As grounds of the input source and the grid are shorted, there is no common mode leakage current. No current flows through the body diodes of switches, so efficiency of the system is improved. Operating principle of the proposed inverter is elaborated in detail. Experimental results of a 350 W proposed inverter validate the theoretical analysis.

As conventional transformerless PV grid-connected inverters have shoot-through problem and common mode leakage current issue, a doubly grounded transformerless PV grid-connected inverter is proposed. The proposed inverter consists of a buck converter and a buck-boost converter, which operates at positive and negative half-line cycles, respectively. There is no shoot-through problem in the proposed inverter, so dead-time in gate signals is not required. As grounds of the PV array and the grid are shorted, the common mode leakage current can be eliminated. No current flows through the body diodes of switches, so there is no reverse recovery issue of the body diodes of switches. Only one switch operates at high frequency in each half-line period, so efficiency of the system is improved. Operating principle of the proposed inverter is elaborated in detail. The control strategy is given. The control method is simple and the grid-connected inverter is a single-stage system in each half-line cycle. Loss calculation and example is given in detail. Finally, simulation and experimental results of the proposed inverter validate the theoretical analysis.

Shoot-through issue of traditional bridge-type grid-connected inverters (GCIs) imposes a risk to GCIs’ reliability and efficiency, so dual-buck type single-phase GCIs are widely used in the applications requiring high reliability and high efficiency. These type of GCIs are reviewed in this paper. As there is no shoot-through issue in the reviewed inverters, reliability of the inverters is improved. The dead time between switches are not required, so quality of the grid current is high. Freewheeling current flows through the independent freewheeling diode instead of the body diode of the switch, so efficiency of the system can be improved. Topologies of the dual-buck type single-phase GCIs can be divided into two categories, i.e., buck and boost GCIs. Derivation of the reviewed topologies is given. Modulation strategies of the presented GCIs are illustrated. Different dual-buck type topologies are compared. Finally, applications of the dual-buck type single-phase GCIs are given.

Photovoltaic (PV) transformer‐less single‐phase inverters are widely used in the solar generation systems because of low cost, high power density, and high efficiency. However, there is a common mode leakage current in the transformer‐less inverters, which may endanger personal safety. In order to reduce the common mode leakage current, extra semiconductors should be added into the PV inverters to decouple the dc side from the ac side. However, the common mode leakage current is affected by the environmental condition and parameters of power devices. Since grounds of the PV array and the output terminal of the inverter are shorted, the common mode leakage current in the doubly grounded inverters can be eliminated thoroughly. Topologies of the doubly grounded inverters are reviewed in this paper, which can be divided into two categories, that is, hybrid topologies and topologies using energy storage elements. Derivation of the reviewed topologies is given. Different topologies of doubly grounded transformer‐less single‐phase inverters are compared.

Doubly grounded transformerless grid-connected inverters are widely used in the PV application because of no common mode leakage current. A boost converter should be added into the doubly grounded PV inverters under shading condition to have boost function. However, the inverter with boost capability is a two-stage system and all switches are operated at high frequency, which reduce efficiency of the system. In addition, processing power of the boost converter is high. Therefore, a single-stage doubly grounded transformerless PV grid-connected inverter with boost function is proposed. The proposed inverter consists of two boost and one buck converters. A cooperative control method among different periods is proposed to reduce processing power of the boost converter and simplify the two-stage system to a single-stage system in each period. In addition, only one switch is operated at high frequency in each period, so efficiency of the system can be improved. Operating principle of the proposed inverter is illustrated. Control strategy is designed. Filter design guidelines and example are given. Loss calculation of the proposed inverter is given. Simulation and experimental results of the proposed inverter verify the theoretical analysis. Finally, comparison among other inverters and the proposed inverter is provided.