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With the rapid development of large scale renewable energy sources and HVDC grid, it is a promising option to connect the renewable energy sources to the HVDC grid with pure DC system, in which high-power high-voltage step-up DC-DC converters are the key equipment to transmit the electrical energy. This paper proposes a resonant converter which is suitable for grid-connected renewable energy sources...
A simple third-order equivalent circuit model of series resonant converter (SRC) is proposed in this paper. Up to now, the most successful equivalent circuit model of SRC is based on extended describing function concept, which is proposed by Dr. E. Yang [30]. However, the equivalent circuit is a complicated fifth-order circuit with the cross-coupling effect and no analytical solution is provided for...
"Direct Adaptive Current Control" (DACC) is a completely adaptive current control scheme with excellent control quality and high dynamics. It is based on the detection of the current slopes during each switching state of the utilized inverter and identifies the system within one period. No control path parameters are needed for setup. One method to measure the current slopes is fast oversampling...
In hard switching boost-type or buck-type three-phase power factor corrected rectifier systems the turn-on losses in continuous conduction mode (CCM) are usually higher than the turn-off losses. This is mainly caused by the reverse recovery effect of the freewheeling diode. The reverse recovery related turn-on losses however may be eliminated if the converter is operated in boundary conduction mode...
Coupled inductor has been widely adopted in VR applications for many years because of its benefits such as reducing current ripple and improving transient performance. In this presentation, coupled inductor concept is applied to interleaved MHz totem-pole CRM PFC converter with GaN devices. The coupled inductor in CRM PFC converter can reduce switching frequency variation, help achieving ZVS and reduce...
The transformerless grid-connected PV system suffers from leakage current and neutral voltage imbalance if three-level inverters are utilized. This paper first investigates the common-mode voltage (CM voltage) reduction/elimination methods in three-phase PV inverters, especially three-level inverters. Several mainstream common-mode voltage reduction/elimination methods, including AZSPWM, 2MV1Z, 3MV,...
Thermal loading of wind power converters is critical to their reliability performance. Especially for IGBT modules applied in a converter, both of the mean value and variation of the junction temperature have significant impact on the lifetime. Besides other strategies to reduce the thermal loading of the IGBT modules, the power losses and thereby the thermal stresses can be controlled by varying...
In computer and telecommunication power supplies, the front end DC-DC stage is required to operate with a wide input voltage range to provide hold up time when AC voltage fails. Conventional LLC converter serving as the DC-DC stage is not suitable for this task, as the normal operation efficiency at 400Vin will be penalized once the converter is designed to achieve high peak gain, i.e. the wide input...
This paper presents an algorithm for seeking the most suitable operating point and the maximum efficiency in respect of the operating conditions in a dual active bridge converter. The method is the most suitable for half-bridge variants of the dual active bridge since the previously presented modulation methods are derived only for full-bridge configurations. The maximum efficiency point tracking...
This paper proposes reduced switching random PWM (RPWM) techniques based on Space Vector PWM (SVPWM) technique for conventional two-level inverters. In the proposed RPWM techniques, the switching frequency is randomized within a band lower than the nominal switching frequency at and around the peaks of the three-phase output currents. For the rest of the fundamental cycle, the switching frequencies...
This paper proposes a variable sampling frequency model predictive control (VSF-MPC) to achieve fixed-switching frequency operation for a neutral-point clamped (NPC) inverter. The proposed control technique simultaneously considers load current control, balancing of DC-link capacitor voltages, mitigation of common-mode voltage, and elimination of even-order and inter-harmonics in the load current...
This paper presents a method to synchronize doubly-fed induction generators (DFIGs) to the grid using a virtual direct power control (DPC) scheme. The nonlinearity of the hysteresis-based controller in DPC approach causes variable switching frequency for rotor side converter, which complicates the filter design. Also, the large ripples in the stator active and reactive power calculations are the major...
This paper presents a new switched-capacitor (SC) based partial power architecture which enhances the performance of resonant dc-dc converters operating at high frequency (HF, 3 MHz–30 MHz) and very high frequency (VHF, above 30 MHz). A wider input and output range, larger voltage conversion ratio, smaller size and excellent transient performance are expected. The prototype comprises of a 20MHz resonant...
This paper proposes an isolated single switch dc-dc converter suited to a high frequency switching operation. The impedance seen at the drain to source node of the switch is mainly designed for achieving zero voltage switching (ZVS) operation and reducing the voltage stress across the switch device. In the proposed converter, leakage inductances of the transformer are integrated to the resonant network...
An improved buck-boost + LLC (IBB LLC) cascaded converter appropriate for wide input voltage situation is presented in this paper, which can be used as a constant voltage source or a constant current source charger for battery. The control strategy of dual frequency PWM (DFPWM) is introduced. For the LLC converter, ZVS for MOSFETs and ZCS for diode are achieved. As a result, the switching loss is...
In order to reduce the power loss of phase-shift full-bridge(PSFB) converter under light load and standby conditions, this paper proposes a simple control method to achieve zero-voltage switching (ZVS) at light load without any additional auxiliary components. The converter with the proposed control method operates in discontinuous conduction mode (DCM) by decreasing switching frequency and all the...
This paper points out the low accuracy of the traditional fundamental harmonic approximation (FHA) in predicting the gain characteristics and resonant behaviors of the full-bridge isolated bidirectional CLLC resonant converter, which results in great impediments in optimally designing the resonant tank parameters. Given these drawbacks of FHA for CLLC converter, this paper proposes a novel operation...
Reducing the power loss of a converter without increasing volume or cost in hardware has always been a much sought-after, but challenging goal. This paper discusses a scheme to improve the system overall efficiency while still meeting a given THD requirement by implementing variable instantaneous switching frequency method without any hardware changes. This paper aims at minimizing the combined switching...
The light load efficiency has drawn more and more attention for the LLC resonant converters. And the high frequency LLC converters are emerging in recent years. The conventional burst mode control cannot fix to the efficiency-optimal state during the burst-on time. Optimal Trajectory Control (OTC) for burst mode can solve this problem by using fixed 3-pulse pattern; however, the burst operation range...
A two-phase buck converter with optimum phase selection for low power applications is presented in this paper. The two-phase converter has a baby-buck phase optimized for light load and a heavy-load phase optimized for heavy load. The phase selector selects an appropriate phase depending on the load current to improve the efficiency. The two phases adopt pulse frequency modulation with constant on-time...
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