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This paper presents a model predictive current control (MPCC) for three-phase four-switch converters (TPFSC) connected to surface permanent magnet synchronous generators (SPMSGs) in oscillating water column (OWC) wave energy plants, that brings some benefits over the existing control methods used in this type of plants. The proposed MPCC for TPFSC follows the current references with great accuracy, whereas the switching frequency of the insulated-gate bipolar transistor (IGBTs) is fixed and low. This method minimizes the current reference tracking error, and its fast response makes it suitable for the power take-off systems present in wave energy converters. Furthermore, the system features a fast capacitor voltage offset suppression control. The dynamic performance and the voltage offset control of the proposed strategy for TPFSC feeding a SPMSG is evaluated in the Simulink environment. Later, experimental studies are carried out on an 8.7 kW laboratory SPMSG prototype. Finally, the capability of the proposed method to harvest the maximum energy from irregular waves is assessed using an OWC power plant emulator. [ABSTRACT FROM AUTHOR]

Self-powered realization for synchronous switching circuits is a hot spot for piezoelectric vibration energy harvesting. Two typical kinds of switches, bipolar junction transistor (BJT) or metal–oxide semiconductor field effect transistor (MOSFET) are popularly used without a clear understanding about the performance difference. In this paper, comparative investigations about adopting these two types of switches based on a case study are performed. It is determined that the performance difference comes from three aspects: the gate parasitic capacitance, the turning-on threshold, and the driven mechanism. In particular, the third one imposes a critical influence on the performance. Investigations are performed on the self-powered synchronous switching circuit of two possible methods: with electronic breakers or with external control units. The results from simulations and experiments show that the current-driven mechanism limits the available performance in the case of the BJT switch in comparison with the case of the MOSFET switch. The difference is especially obvious for the cases of large piezoelectric capacitance and open-circuit voltage. A preliminary design guideline is concluded that the MOSFET is probably a better choice with the same voltage and current ratings in most cases. [ABSTRACT FROM AUTHOR]

This paper presents a novel three-phase DC-link multilevel inverter topology with reduced number of input DC power supplies. The proposed inverter consists of series-connected half-bridge modules to generate the multilevel waveform and a simple H-bridge module, acting as a polarity generator. The inverter output voltage is transferred to the load through a three-phase transformer, which facilitates a galvanic isolation between the inverter and the load. The proposed topology features many advantages when compared with the conventional multilevel inverters proposed in the literatures. These features include scalability, simple control, reduced number of DC voltage sources, and less devices count. A simple sinusoidal pulse-width modulation technique is employed to control the proposed inverter. The performance of the inverter is evaluated under different loading conditions and a comparison with some existing topologies is also presented. The feasibility and effectiveness of the proposed inverter are confirmed through simulation and experimental studies using a scaled down low-voltage laboratory prototype. [ABSTRACT FROM AUTHOR]

High-voltage (HV) pulses are used in electroporation to subject pulsed electric field (PEF) onto a sample under treatment. Pulse-waveform shape, voltage magnitude, pulse duration, and pulse repetition rate are the basic controllable variables required for particular PEF application. In practice, a custom-made pulse generator is dedicated for each PEF application with limited flexibility in changing these variables. In this paper, a universal pulse-waveform generator (UPG) is proposed, where the controller software algorithm can manipulate a basic generated multilevel pulse waveform to emulate many different PEF pulse waveforms. The commonly used PEF HV pulse waveforms can be generated as bipolar or monopolar with controllable pulse durations, repetition times, and voltage magnitudes. The UPG has the ability to generate multilevel pulses that have controllable $dv/dt$, which allows reduction of the electromagnetic interference generated by the converter. The UPG topology is based on half-bridge modular multilevel converter (HB-MMC) cells forming two transition arms in conjunction with two bistate arms, together creating an H-bridge. The HB-MMC cell capacitors provide a controllable energy source which charge from the dc input supply and discharge across the load, while the two bistate arms allow charging the HB-MMC cell capacitors. Hence, the UPG topology offers modularity, redundancy, and scalability. The HB-MMC individual cell capacitance is low and the cell voltages are balanced by employing the sorting and rotating algorithm used in conventional HB-MMC topologies for HV dc transmission applications. The viability of the proposed UPG converter is validated by MATLAB/Simulink simulation and scaled-down experimentation. [ABSTRACT FROM PUBLISHER]

In this paper, the concept of a modulated-ramp pulse-width modulation (PWM) generator is presented. The specific nonlinear behavior of this generator enables an exact linear control-to-output static conversion characteristic of DC-DC switching converters, such as the boost (step-up), buck/boost, Ćuk, or SEPIC, operating in continuous conduction mode. The resulting linearization leads to a significant improvement of the control accuracy and simplification of the converters, operating mainly in the open-loop architecture. In this paper, the concept of the modulated-ramp PWM generator is described, followed by a detailed steady-state and small-signal AC analysis. The key aspects for practical implementation are also highlighted. All results and benefits of the modulated-ramp PWM generator are demonstrated here on the boost converter power stage. [ABSTRACT FROM AUTHOR]

Flapping electromagnetic-reed generators are investigated to harvest wind energy, even at low cutoff wind speeds. Power electronic interfaces are intended to address ac–dc conversion and power conditioning for single- or multiple-channel systems. However, the generated voltage of each generator reed at low wind speed is usually below the threshold voltage of power electronic semiconductor devices, increasing the difficulty and inefficiency of rectification, particularly at relatively low output powers. This paper proposes a multiinput bridgeless resonant ac–dc converter to achieve ac–dc conversion, step-up voltage and match optimal impedance for a multichannel electromagnetic energy harvesting system. Alternating voltage of each generator is stepped up through the switching LC network and then rectified by a freewheeling diode. Its resonant operation enhances efficiency and enables miniaturization through high frequency switching. The optimal electrical impedance can be adjusted through resonance impedance matching and pulse-frequency-modulation control. A 5 cm × 3 cm, six-input standalone prototype is fabricated to address power conditioning for a six-channel wind panel. [ABSTRACT FROM PUBLISHER]

This paper presents the development of a wind interior permanent-magnet synchronous generator (IPMSG)-based dc microgrid and its operation control. First, the derated characteristics of PMSG systems with various ac/dc converters and operation controls are comparatively analyzed. Then, the IPMSG followed by a three-phase Vienna switch-mode rectifier is developed to establish the common dc bus of dc microgrid. Good developed power and voltage regulation characteristics are achieved via the proposed commutation tuning, robust current, and voltage controls. Second, a single-phase three-wire inverter is constructed to serve as the test load. Good ac 220 V/110 V output voltage waveforms under unknown and nonlinear loads are preserved by the developed robust waveform tracking control scheme. Third, a battery energy storage system is established, and the fast energy storage support response is obtained via the proposed droop control approach with adaptive predictive current control method. In addition, a chopped dump load is equipped to enhance the energy balance control flexibility. [ABSTRACT FROM AUTHOR]

In this paper, a bidirectional dc-dc converter is proposed for the automotive engine/battery hybrid power generators. The two-stage bidirectional converter employing a fixed-frequency series loaded resonant converter is designed to be capable of operating under zero-current-switching turn-on and turn-off regardless of voltage and load variation, and hence its magnetic components and EMI filters can be optimized. Also, a new autonomous and seamless bidirectional voltage control method that combines two individual controllers for low-voltage side control and high-voltage side control by introducing a variable current limiter is proposed to provide uninterrupted power to critical ac loads and reduce the size of the dc bus capacitor and the transition time. Experimental results from a 5-kW prototype are provided to validate the proposed concept. [ABSTRACT FROM AUTHOR]

This paper proposes a hardware in-the-loop simulation (HILS) system as a new method to develop and test control algorithms and operation strategies for a microgrid. The HILS system is composed of a real-time digital simulator (RTDS) for real-time simulation of the microgrid, a prototype microgrid management system (MMS) under test, and a communication emulator for interface between the prototype MMS and the RTDS. The prototype MMS is designed to operate microsources of microgrid and to control power flow at the point of common coupling (PCC) in the grid-connected mode, and voltages and frequency in the islanded mode of the microgrid. The MMS is tested in the grid-connected mode and in the islanded mode, respectively, to show the validation of the proposed HILS system. [ABSTRACT FROM PUBLISHER]