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In this article, a highly efficient battery-balancing circuit with output voltage regulation for mobile applications is proposed and analyzed. The proposed circuit performs a cell-balancing operation for series-connected multiple-battery cells and voltage regulation operation simultaneously without additional power conversion stages. Therefore, it can be integrated into a battery pack with maximized power density and efficiency. These features are essential for recent low-power applications with multiple batteries, such as wireless/smart speakers, drones, and electronic point-of-sale, that require high power density. The operational principle, electrical modeling, and tradeoff relationship between the system power losses and balancing characteristics are derived, and the optimal design candidates of the proposed topology are discussed in terms of Pareto optimization. The effectiveness of the proposed system is verified with a prototype board using GaN switches, and 96.05% efficiency is achieved with a 1.8 V, 0.5 A load. [ABSTRACT FROM AUTHOR]

This paper presents a droop control for a stable grid-integrated operation of doubly fed induction generator (DFIG) within microgrid. While the leakage inductances were neglected in the conventional control method, the proposed droop control uses the leakage inductances of DFIG as the output filter inductance by simply just changing the field orientation. This additional output filter inductor improves the system stability by adjusting the output impedance in the microgrid, of which the line impedance is mainly resistive. Also, the virtual impedance method, which is used for the power decoupling and the system stabilization in an inverter-based generator, is introduced to the proposed droop control of DFIG for the case that the leakage inductances are insufficient. To validate the proposed droop control method of DFIG, the simulation and experimental results in the resistive line impedance, where the conventional droop control of DFIG is unstable, are presented. [ABSTRACT FROM AUTHOR]

The six-step operation of surface-mounted permanent magnet machine drives in a flux weakening region has many advantages compared to the pulse width modulation mode, such as the reduced switching loss and fully utilized inverter output voltage. However, if the ratio of the sampling frequency to the fundamental frequency is low in fixed sampling system, the low-frequency oscillation in the current can be incurred in the six-step operation. The low-frequency current causes a system stability problem and reduces system efficiency due to an excessive heat and high power loss. Therefore, this paper proposes the variable time step controller for six-step operation. By updating an output voltage, sampling phase currents, and executing the digital controller synchronized with the variable sampling time, the turn on and off switch signals for six-step operation can be generated at the exact moment. As a result, the low-frequency oscillation in the phase current can be eliminated. In addition, the system transfer function of the proposed control method is discussed for the system stability and system dynamic analysis. The effectiveness of the proposed method is verified by the comparative simulation and experimental results. [ABSTRACT FROM AUTHOR]

A double inverter fed wound machine (DFWM) needs two inverters on the rotor as well as the stator side. This scheme gives more freedom to operation of an electric machine and improves the output power capability and the efficiency, but its control method becomes more complex because the number of control variables and the operating constraints increase. This paper deals with a control method of DFWM for minimizing the copper loss in maximized operating area. The possible operation area considering all constraints of currents, voltages, and flux is analyzed on the stator currents plane to maximize the operating area. For the minimum copper loss operation in the operating area, different modes are defined and the optimal currents are determined in each mode. Also, the optimal current selection algorithm is proposed to achieve the torque control using the optimal currents. The simulation and experimental results about wound machines are presented to show the feasibility of the proposed control method. [ABSTRACT FROM PUBLISHER]

This paper presents a novel family of single-switch resonant dc–dc converters with low switch voltage stress. The single-switch resonant converter which has a ground-referenced switch is advantageous for implementing the gate drive circuit and operating at several-MHz switching frequency. However, the conventional ones mostly have high voltage stress on the switch, roughly 4–5 times the input voltage. In this paper, we propose the single-switch converter topologies derived from the drain-source impedance networks consisting of two inductors and two capacitors. The switch voltage of the proposed converters is shaped into a near trapezoid by designing the resonant networks to have the desired drain-source impedance. Furthermore, a simple and specific design scheme is presented here so that the peak switch voltage is lowered to 2.2–2.5 times the input voltage while zero voltage switching is achieved. Experimental results from a 20-W GaN-based prototype operating at 10 MHz demonstrate the feasibility of the proposed converter topologies and the design method. [ABSTRACT FROM AUTHOR]

In this paper, a control method for motor drive system without electrolytic capacitor is proposed. Since dc-link capacitor of this motor drive is about 1% of the conventional one, it can satisfy the grid current regulation of IEC61000-3-2 without bulky filter circuits by directly controlling the electric output power of the inverter. However, dc-link voltage of this drive fluctuates as the rectified grid voltage. It causes higher motor current, especially at the low dc-link voltage area, and severely harms the drive efficiency. To solve this problem, proposed method keeps the dc-link voltage higher than certain limit while controlling the output power. It can improve the efficiency of the drive by lowering the d-axis current at low dc-link voltage area, with satisfying the regulation with small grid current harmonics. The proposed method includes the motor current reference generation for the limited dc-link voltage and selection of the limitation value. The improved performance of the proposed method was verified by the experimental results. [ABSTRACT FROM PUBLISHER]

In this paper, a synchronous motor with an inverter integrated rotor (SMIIR) is introduced, and its control scheme is proposed. This presents a new breed of synchronous motor in that it integrates an inverter inside the rotor. The basic operational principle and control strategies are discussed. Given these new strategies, the SMIIR can be considered as a synchronous motor which changes its field according to the harmonic voltage of the stator inverter. The feasibility of the proposed structure of the drive system and its operation principle are evaluated through experimental results. [ABSTRACT FROM AUTHOR]