This paper presents a new bridgeless buck-boost power factor corrector with the use of the active virtual ground technique, which is named as the Manitoba Rectifier. The proposed topology can convert the grid ac voltage into a wide range of voltage outputs within a single-stage circuit. It is in a bridgeless structure and simple in design. During the operation, an LC filter is generated at the system input, where continuous grid current is guaranteed in a buck-boost characteristic topology. In addition, the filter capacitor helps to clamp the voltage ripple between the grid and the output bus terminal. Both leakage current and common mode noise are kept in a relatively small value. Thus, a single-stage and low common-mode buck-boost converter system is built. The proposed topology is successfully implemented on an 800 W prototype, and the performance is experimentally verified, which shows good agreement with the theoretical findings.

The paper presents a new transformerless single-phase single-stage buck-boost grid-connected voltage source inverter (VSI) topology. The topology can achieve efficient power conversion with a wide input voltage range, number of magnetic devices reduction and low leakage current. The proposed VSI topology consists of high frequency semiconductors for shaping inductor currents, and low frequency semiconductors to form grid CL filter structure for different conditions. This CL filter uses the same buck-boost inductor, thus no additional line frequency inductor is required. Besides, common mode voltage, a main problem of transformerless grid-connected VSI, is mitigated, since the capacitor in the CL filter clamps the voltage between the grid and the bus terminal. The performance of the proposed VSI is experimentally verified. The results show that the proposed VSI guarantees sinusoidal output current and wide input voltage range, and has a good agreement with the theoretical findings.

This paper presented a new hybrid circuit breaker solution for using in dc microgrids. The proposed solution can offer a high-reliability protection feature for the dc microgrid with low conduction loss, bidirectional current flow, and galvanic isolation function. In the design, it is combined with a group of mechanical switches and semiconductors, where the mechanical switches handle the current conduction during normal operation and the semiconductors handle the breaker response during transient operation. The design fully utilizes the advantage of both types of switches and maximizes the performance and life time of the system. Throughout the design, it maintains only one mechanical switch in series with each power line, thereby the high conductivity of the circuit breaker is maintained. At the same time, through the hybrid design, the electrical stress applied to the mechanical switch is eliminated. Thus, an effective and high-reliability solution is provided for the design of dc circuit breakers. The operation principle is explained in details and the design guideline is provided. A 150/380 V and 15 A circuit breaker is successfully implemented and the performance is experimentally verified which shows good agreement with the theoretical findings.

Constructing LCL filter with only three inductors is made possible by a topology called the reconfigurable filter in three-phase converters, in which the filter is reconfigured six times during the ac line cycle. While the existing reconfigurable filter reduces the magnetic components by half, it cannot be installed as an add-on filter to existing converters due to requiring a dc link connection. In this article, a novel reconfigurable LCL filter applied in photovoltaic transformerless inverters is proposed, which not only inherits the merits of the existing reconfigurable filter but also eliminates the need for a dc link connection, enabling easy installation in existing converters. In addition, the proposed reconfigurable filter effectively clamps the common-mode voltage to neutral at high frequencies, resulting in the reduction of leakage current. Therefore, the proposed topology offers several advantages with one solution, including injecting high-quality grid current, magnetic component reduction, leakage current reduction, compatibility with add-on installations, and reactive power support. Comprehensive equivalent circuits, modeling, and analysis are provided to study the operation modes, leakage current capability, and loss breakdown of the proposed topology. The proposed topology is verified and compared with the existing reconfigurable filter by a 1-kW experimental prototype. All the experimental results agree with the theoretical concepts.

The continuously increasing demand of renewable energy has advanced the development of photovoltaic (PV) systems and maximum power point tracking (MPPT) algorithms. The classic hill-climbing plus proportional-integral technique is being challenged under rapidly changing environmental conditions. This paper proposes an MPPT algorithm with fast transient responses, while maximizing the efficiency of PV applications. This novel approach employs a dp/dv tracking method in conjunction with a second-order switching surface controller in a boost-type converter. Successful tracking of the maximum power point (MPP) is achieved in switching-cycle level with a precise voltage ripple control. A 280-W converter embedded with the proposed controller is built and tested with multiple PV panels. Experiment results show that the proposed scheme can reach a new MPP in 300 μs and show a good agreement with the derived theory.

Three-phase power factor correction (PFC) converters are the front-end stage of the power conversion that are required to be connected to the grid with a proper filter to meet international standards. A high-order LCL filter is a widely used solution to reduce the component size of the filter although it requires six inductors. In this article, a novel reconfigurable LCL filter that consists of only three inductors is proposed. The principle of the reconfigurable filter is to fully utilize the converter-side inductors by changing their position from the converter side to the grid side and vice versa. The filter is reconfigured by using three low-frequency (LF) bidirectional switches. The ultimate goal of the proposed topology is to reduce the magnetic components by half and achieve comparable grid current quality as the conventional topology. The proposed PFC topology is verified by a 1-kW experimental prototype. All the experimental results agree with the theoretical concepts and prove that the grid current quality of the proposed topology is comparable with the conventional topology.