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This paper introduces a novel isolated hybrid resonant converter with smooth transition between multiple operating modes. With the simple addition of a bidirectional ac switch, the highly-efficient series resonant converter operating in the discontinuous conduction mode (DCM) is combined with a phase-shifted full-bridge buck converter and a pulse width modulated (PWM) boost converter in order to provide...
This paper analyzes the behavior of a pure capacitive output filter in parallel and series-parallel resonant converters. Unlike traditional resonant voltage-and current-driven rectifiers, pure capacitive output filters present interruptions in power transfer from the transformer primary to the secondary, owing to the existence of a parallel resonant capacitor. Therefore, existing formulas for different...
In this paper, a frequency-doubling LLC resonant converter with high step-down voltage gain for high input voltage applications is proposed. The three-level structure consisting two series half bridges is adopted in the converter to reduce the voltage stresses of the primary-side switches to only half of the input voltage. Thus the low-voltage rated power devices could be used to improve the converter...
This paper shows an innovative improvement of the constant on time (COT) control of transition mode boost PFC. The proposed control method employs a minimum current comparator to improve the harmonic distortion and power factor of the converter while maintaining the same complexity of the constant on time control. An overview and the enhancements of this method are presented in comparison to the standard...
This paper proposes a new topology for a pulse width modulation (PWM) rectifier which can achieves both sinusoidal input current on the ac side and ripple power decoupling on the DC side without additional switches. The AC inductor of the conventional H-bridge circuit is divided into two parts and only an auxiliary decoupling capacitor is added in the proposed circuit. Control scheme is also proposed...
Single-phase AC/DC or DC/AC systems inherently subject to harmonic disturbance which is caused by the well-known double line frequency ripple power. This issue can be eased through the installation of bulky electrolytic capacitors in the dc-link, but such passive filtering approach may inevitably lead to low power density and limited system lifetime. An alternative approach is to use active power...
This paper presents a high efficiency, continuous conduction mode (CCM), zero voltage switching (ZVS) bridgeless AC-DC power-factor-correction (PFC) converter for neighborhood electric vehicle (NEV) battery charging. The converter operates in both pulse-width-modulation (PWM) mode and resonant mode each switching cycle and utilizes standard average-current-mode control. This new modulation technique...
This paper investigates the dc link voltage ripple in a modular multilevel converter (MMC). It is found that switching-frequency ripple occurs on the dc link voltage in MMC when circulating current suppressing control is implemented. The mechanism of the switching-frequency voltage ripple is investigated and explained. Circulating current suppressing control will manipulate the average values for...
This paper suggests a new method to balance the voltage of the two capacitors in the three-level neutral-point clamped (NPC) converter. The proposed method only needs the information of two capacitor voltages. The two capacitor voltages are fed back to the controller and then the controller generates phase shifting value with which sinusoidal modulation will be adjusted to the left or right. This...
The fundamental building block of cascaded static synchronous compensator used in distribution grid is H-bridge based converter module. In this paper a type of "plug and play" module was introduced to improve the device compensation performance and reliability. The module based on IGBT parallel connection was discussed about the design of electrical parameters and physical structure. In...
With voltage-balancing control, the voltage difference among sub-module (SM) capacitors in a modular multilevel converter can be reduced. However, this comes at the cost of increased device switching frequency. In this paper, the relationship between the switching frequency and SM capacitor unbalanced voltage is investigated. As the relationship depends on the voltage-balancing control schemes, a...
DC capacitor voltage imbalance is an inevitable technical concern for the multilevel diode-clamped converters with number of levels higher than two. This paper addresses the balancing of the capacitor voltages based on the capacitor current equalization considering a minimum loss space vector pulse width modulation (MLSVPWM) algorithm for five-level diode-clamped converters. In diode-clamped converter...
A new method to selectively control the amount of dc-link voltage ripple by processing the desired reactive power by a DC/DC converter in an isolated AC/DC or AC/DC/AC system is proposed. The concept can reduce the dc-link capacitors used for balancing the input and output power and thereby limiting the voltage ripple. It allows the use of a smaller dc-link capacitor and hence a longer lifetime and...
One of the main technical challenges of the Modular Multilevel Converter (MMC) for medium-voltage adjustable-speed motor drive applications is the large magnitude of the SubModule (SM) capacitor voltage ripple under low-speed operation. This paper proposes two new techniques to reduce the magnitude of SM capacitor voltage ripple of the MMC for motor drive applications. The paper presents a comprehensive...
This paper introduces a low complexity implementation of the voltage balancing sorting algorithm to reduce the switching frequency of the power devices in modular multilevel converters (MMCs). Two modulation techniques are evaluated; staircase modulation and phase-disposition pulse-width modulation (PD-PWM) under the conventional and the proposed algorithm. Using a circulating current controller in...
This paper proposes the pulse width modulation (PWM) control strategy for low-speed operation in the three-level neutral-point-clamped (NPC) inverters based on the bootstrap gate drive circuit. For the purpose of the cost reduction, several papers have paid attention to the bootstrap circuit applied to the three-level NPC inverter. However, the bootstrap gate driver IC cannot generate the gate signal...
Engineering design of structure and bus bar for a three phase 1.2MVA hybrid clamped five-level (HCFL) converter module is presented in this paper. Firstly, the commutation characteristics of the HCFL topology are analyzed. Based on the analysis, a decoupling structural design is proposed to eliminate the negative effect of high frequency current. Secondly, a laminated design for bus bar is employed...
Nine-switch converter is a recently proposed reduced-switch equivalence of the twelve-switch back-to-back converter. The usual expectation is thus for the nine-switch converter to face some switching constraints and hence performance tradeoffs. However, this might not always be the case with an answer only available after performing a thorough analysis. For that, it is the intention now to compare...
In this paper, a new method to balance the DC bus capacitor voltages of two-stage AC-DC-AC converters with split-capacitor inverters is proposed. Converters use such split-capacitor inverters for various reasons such as cost, improved harmonic content and lower switch voltage stresses than those of conventional two-level, six-switch inverters, but the effectiveness of such inverters is limited by...
Transformer parameters such as leakage inductance and self-capacitance are rarely calculated in advance during the design phase, because of the complexity and huge analytical error margins caused by practical winding implementation issues. Thus, choosing one transformer architecture over another for a given design is usually based on experience or a trial and error approach. This work presents equations...
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