This paper proposes a novel integrated multiport bidirectional back-to-back power converter for a type-4 wind turbine that accommodates a battery and supercapacitor for energy storage. The circuit topology reduces 4 switches compared to the traditional configuration. Moreover, owing to the dual-buck structure embedded in the phase leg, the circuitry has no short-circuit path, therefore it withstands short-circuited events for a much longer time than the normal phase-leg and prevents the reverse current in turn-off recovery. The use of a hybrid energy storage system with battery and supercapacitor helps smooth out the power output under wind gusts and stabilizes the DC-link voltage under grid fault conditions. The case studies are carried out with a 1.5 MW wind turbine system. Simulation results are provided for the theoretical validation.

This paper proposes a novel integrated multiport bidirectional dc-dc converter to interface the battery, the ultra-capacitor, the fuel cell, or other energy sources with the dc-link capacitor of the hybrid energy systems such as the hybrid electric vehicle (HEV) and fuel cell vehicle (FCV) applications. The proposed converter can be applied to the distributed generation systems which include local energy sources, storage, and loads. It can perform both buck and boost functions with fewer switches. In addition, it is extendable when more inputs and/or outputs are required. The operating principle and control strategy of the proposed converter will be analyzed in detail. For verification, simulation, and experimental results of the four utilized operating modes of an HEV/FCV are provided.

The real-time models of offshore wind turbines are proposed in this study, which are developed in compliance with the Western Electricity Coordinating Council (WECC) standard to meet the industry requirements. In addition to basic functionalities of the generic WECC turbine model such as power curtailment and voltage ride through, the sequence current control and sequence current limit are designed for future electromagnetic transient (EMT) testing and control of offshore wind farms. Both average-value and switching detailed models are modeled in the Opal-RT simulator. Both balanced and unbalanced faults are studied to show the feasibility of the proposed turbine models. The models are validated against the WECC second-generation generic wind turbine model. The active and reactive power results for low-voltage ride through cases validated the turbine model’s performance against WECC generic model in the balanced system. In addition, the models provide extended capability in mitigating the active power oscillation during unbalanced fault conditions.

The circulating current among the parallel inverter-based distributed generations (DGs) in the microgrid (MG) system causes several negative impacts on the operation of inverters. The suppression of circulating current should be considered in the controller design of the inverter, especially in the case of using finite control set model predictive control (FCS-MPC) in which the switching frequency of the inverter is varied. This paper proposed an MPC with constant switching frequency for the inverter in the MG system. The proposed MPC is based on the use of virtual state vectors in addition to the real state vectors of the inverter. The discrete time model of inverter is used to find the optimal state vector of inverter including virtual states. The modulation voltage is calculated accordingly. The pulse width modulation is used to obtain the constant switching frequency of inverter. The MG system with three inverter-based DGs are used to show the impact of the proposed controller on the circulating current suppression. The effect of different number of virtual state vectors is presented in this study. The feasibility of the proposed controller is validated by the real time simulation using OP5600 of OPAL technologies.

Battery energy storage systems (BESSs) have been widely used to minimize wind power fluctuations in microgrids. BESSs control systems are usually based on vector-controlled techniques with inner current control loops and outer control loops. Owing to the complexity of a control system, it is difficult to apply additional functions such as predicting wind power. This paper presents a detailed description of predictive power control in the BESS for smoothing wind power fluctuations. The proposed control system includes the Kalman filter used to predict wind power. Simulation results are provided to confirm the performance of the proposed control system.