Zhixiang Yu

Bio: Zhixiang Yu is an academic researcher. The author has contributed to research in topics: Photovoltaic system. The author has an hindex of 1, co-authored 1 publications receiving 3 citations.

Analysis and Design of a Transformerless Boost Inverter for Stand-Alone Photovoltaic Generation Systems

Abstract: A novel transformerless boost inverter for standalone photovoltaic generation systems is proposed in this paper. The proposed inverter combines the boost converter with the traditional bridge inverter. The switch S1 not only realizes the boost function but also participates in inverting process. The inverter has a higher voltage gain and good characteristics when the inductor L1 is operated in discontinuous mode (DCM) and the nonpolarized capacitor can be chosen as bus capacitor, which makes the volume smaller and the service life of the inverter is increased. The inverter consists of five switches in which only two switches are operated at high frequency state and a monopole sinusoidal pulse width modulation (SPWM) strategy is used. Therefore, the modulation strategy of switches is very simple and the switching loss is reduced. The principle of inverter is described in detail and mathematical models are built by small-signal analysis. Finally, the correctness of the theoretical analysis is verified by simulation and experiment.

A Novel and High-Gain Switched-Capacitor and Switched-Inductor-based DC/DC Boost Converter with Low Input Current Ripple and Mitigated Voltage Stresses

Abstract: High voltage gain DC-DC boost converters are used widely in grid-connected applications through integration with the Renewable Energy Sources (RESs). Photovoltaic (PV) arrays or Fuel Cells (FCs) generate a limited value of the DC voltages and then for high power and high voltage applications, at the first stage, these voltages should be increased. This study presents a high gain, single-switched, and efficient DC-DC boost converter using the switched-capacitor and switched-inductor cells. These blocks easily can enhance the voltage and present an input current with the less values of the ripples. This will be done through replacing the location of the input inductors and by applying a switched-inductor block. Magnetizing in parallel and demagnetizing in series for the inductors present the smaller input current stresses. A single switch is used for the proposed boost converter that directly decreases the complexity of the control circuit for obtaining a fixed DC voltage at the output side for flexible input voltages or loads. More voltages will be presented by the used switched-capacitor cell simply by adding several diodes and capacitors. A deep and detailed mathematical analysis will be presented for continuous (CCM) and discontinuous conduction modes (DCM) and a 200 W laboratory-scaled prototype is presented. The results of the hardware tests confirm the correctness of the theoretical analysis and simulation results.

A Novel and High-Gain Switched-Capacitor and Switched-Inductor-Based DC/DC Boost Converter With Low Input Current Ripple and Mitigated Voltage Stresses

Abstract: High voltage gain DC-DC boost converters are widely used in grid-connected applications through integration with the Renewable Energy Sources (RESs). Photovoltaic (PV) arrays or Fuel Cells (FCs) generate a limited value of the DC voltages and then for high power and high voltage applications, at the first stage, these voltages should be increased. This study presents a high gain, single-switched, and efficient DC-DC boost converter using the switched-capacitor and switched-inductor cells. These blocks easily can enhance the voltage and present an input current with the least values of the ripples. This will be done through replacing the location of the input inductors and by applying a switched-inductor block. Magnetizing in parallel and demagnetizing in series for the inductors present the smaller input current stresses. A single switch is used for the proposed boost converter that directly decreases the complexity of the control circuit for obtaining a fixed DC voltage at the output side for flexible input voltages or loads. More voltages will be presented by the used switched-capacitor cell simply by adding several diodes and capacitors. A deep and detailed mathematical analysis will be presented for continuous (CCM) and discontinuous conduction modes (DCM) and a 200 W laboratory-scaled prototype is presented. The results of the hardware tests confirm the correctness of the theoretical analysis and simulation results.

Control of a Single Stage Boost Inverter Based on Dynamic Sliding Mode Control with Power Decoupling

Abstract: In this paper, the problem of control a single-stage boost inverter is studied. The goal is to achieve a system with robustness against variations in parameters, fast response, high-quality AC voltage, and smooth DC current. To this end, a new type of dynamic sliding mode control is proposed to apply to various scenarios such as parameter uncertainties and DC input voltages. In comparison with the conventional double-loop controllers, the proposed sliding mode controller utilizes only a single loop in its design, while having attractive features such as robustness against parametric uncertainties. In addition, a methodology is proposed for the decoupling of double-frequency power ripples based on proportional-resonant (PR) control to remove the low-frequency current ripples without using additional power components. Compared to conventional controllers, the proposed controller provides several features such as fast and chattering-free response, robustness against uncertainty in the parameters, smooth control, proper steady-state error, decoupled power and good total harmonic distortion (THD) over the output voltage and input currents, and simple implementation. In a fair comparison with classical sliding mode control, simulation results demonstrate more satisfactory performance and effectiveness of the proposed control method.

An Intelligent Control Strategy for a Highly Reliable Microgrid in Island Mode

Abstract: An intelligent control strategy based on a membership cloud model in a high reliable off-grid microgrid with a reconfigurable inverter is proposed in this paper. The operating principle of the off-grid microgrid with the reconfigurable inverter is provided, which contains four operating modes. An open-circuit fault diagnosis for the inverter is presented first. The polarities of the midpoint voltages defined in the paper are used to recognize the faulty power switch. The reconfigurable inverter allows the power switches of different bridges to be reconfigured, when there are power switches faulty, to let the inverter operate in faulty state. The working principle of the reconfigurable inverter is given. The membership cloud model with two output channels is built to obtain the virtual impedance to suppress the circulating currents between inverters when the reconfigurable inverter is in faulty state. A pulse resetting method is presented. The general intelligent control strategy for the reconfigurable inverter is formed as the droop-virtual impedance-voltage-current-pulses resetting control. The validity of the intelligent control strategy of the system is verified by simulation.