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This paper describes the conception and analysis of a unidirectional hybrid three-phase rectifier suitable for medium-and high-power applications. The rectifier is composed of a single-switch diode bridge boost-type rectifier in parallel with a pulsewidth modulation (PWM) three-phase unidirectional boost rectifier. The objective is to obtain a structure capable of providing sinusoidal input currents with low harmonic distortion and dc output voltage regulation. The diode rectifier operates at low frequency and has a higher output power rating. Therefore, the PWM unidirectional rectifier is designed to operate with a small power rating and at a high switching frequency. The total harmonic distortion of the proposed structure varies between 0% and 32%, depending only on the amount of power processed by the PWM three-phase unidirectional rectifier. The rectifier topology conception, principle of operation, control scheme, and simulation and experimental results of a 20-kW laboratory prototype are also presented in this paper. Index Terms--High-power application, hybrid rectifier, power factor improvement, pulsewidth modulation (PWM) unidirectional rectifier.

A systematic analysis of line-current distortions of the discontinuous-conduction-mode and the continuous-conduction-mode boundary boost power factor correction converter due to valley switching (VS) and switching-frequency limitation, where VS is either maintained or lost after the onset of switching-frequency limitation, is provided. Closed-form expressions for the line current are derived. It is shown that if the switching frequency is limited and VS is not maintained, the line current is more distorted with voltage-mode control than with current-mode control. The effects of line-current distortions are demonstrated with both simulation and experimental results. Index Terms--Boost converter, discontinuous conduction mode (DCM)/continuous conduction mode (CCM) boundary, line-current distortion, power factor correction (PFC), single-phase rectifier, switching-frequency limitation, valley switching (VS).

In this paper, the first single-loop current sensorless control (SLCSC) in continuous current mode (CCM) for single-phase boost-type switching-mode rectifiers (SMRs) is developed and digitally implemented in a DSP-based system. Compared to the conventional multiloop control with one inner current loop and one outer voltage loop, there is only one voltage loop in the proposed SLCSC, where the voltage loop's output is used to shift the nominal duty ratio pattern generated from the sensed input and output voltages. Because of no current loop, the efforts of sampling and tracking inductor current can be saved. It implies that the proposed SLCSC is simple and very adaptable to the implementation with mixed-signal ICs. First, the effects of shifting nominal duty ratio pattern on the input current waveform are analyzed and modeled by considering the inductor resistance and conduction voltages. The result of analysis shows that the pure sinusoidal current can be inherently generated by the nominal duty ratio pattern where the current amplitude is roughly proportional to the controllable phase of nominal duty ratio pattern. Then, a voltage controller is included to regulate the dc output voltage by tuning this controllable phase. Finally, some simulated and experimental results have been given to demonstrate the performance of the proposed SLCSC. Index Terms--Power factor correction, sensorless control, switching-mode rectifier (SMR).

Recently, a new multilevel inverter--Hexagram inverter has been reported for medium-voltage (MV) variable-speed drives (VSDs). This paper will propose a Hexagram rectifier as the active front end for the Hexagram-based MV VSD systems. The control of the Hexagram rectifier is based on one-cycle control--an excellent control scheme for switching power converters. With the proposed control scheme, unity power factor at the source side can be achieved, the six modules will equally share the output power, and the voltage stress of the converter will be reduced six times. A 1-MW simulation model and a 1.2-kW experimental prototype have been built to demonstrate the proposed Hexagram rectifier and its control scheme. Index Terms--Multilevel systems, pulsewidth-modulated (PWM) power converters, rectifiers, variable-speed drives (VSDs).

A new double-ended type zero-voltage switching (ZVS) half-bridge zeta (HBZ) converter employing a double-ended rectifier (DER) is proposed. The proposed DER for the HBZ converter provides a bidirectional powering path in the rectifier. As a result, the improved voltage waveform of the rectifier reduces the output filter size and voltage stresses on rectifier components. Moreover, it offers a wide ZVS range. In addition, to minimize the secondary snubber loss, a simple lossless snubber is adopted. The operational principles and characteristics of the proposed converter are to be analyzed and verified experimentally. Index Terms--Double ended rectifier (DER), half-bridge zeta (HBZ) converter, single-ended rectifier (SER), zero-voltage switching (ZVS).

In this paper, an improved current-doubler rectifier with coupled inductors is proposed. The proposed rectifier can extend duty ratio to reduce the peak current through the isolation transformer winding and lower output current ripple as well as voltage stress of the rectifier diodes. In this study, a 500-W prototype with a full-bridge phase-shift converter, the proposed rectifier, with input voltage of 400 V and output voltage of 12 V was built. Theoretical analysis and experimental results have verified that the proposed rectifier is attractive for high step-down voltage and high-power applications. Index Terms--Coupled inductors, current-doubler rectifier, full-bridge phase-shift converter, isolation transformer, tapped inductor.

This paper presents a new control scheme for an active front-end rectifier using model-based predictive control. The control strategy minimizes a cost function, which represents the desired behavior of the converter. Future values of currents and power are predicted using a discrete-time model. The active and reactive powers are directly controlled by selecting the optimal switching state. The main advantages of this method are that there is no need of linear current controllers, coordinates transformations or modulators. The rectifier operates with sinusoidal input currents and unity power factor. Simulation and experimental results are presented to verify the performance of the proposed power control scheme. Index Terms--AC-DC power conversion, power control, predictive control.

A new phase-shifted full-bridge converter with a voltage-doubler-type rectifier for a high-efficiency power-sustaining module of a plasma display panel is proposed in this paper. The proposed converter employs a voltage-doubler rectifier without an output inductor. Since it does not have an output inductor, the voltage stresses of the rectifier diodes can be clamped at the output voltage level. Thus, since no dissipative resistor-capacitor snubber for rectifier diodes is needed, high-efficiency low-noise output voltage can be realized. Due to the elimination of the large output inductor, it features simpler structure, lower cost, smaller mass, and lighter weight. Furthermore, the proposed converter has wide zero-voltage-switching ranges of lagging leg switches with low current stresses of the primary power switches by using the magnetizing current. In addition, the resonance between the leakage inductor of the transformer and the rectifier capacitors can reduce the current stresses of the rectifier diodes and conduction losses. In this paper, the operational principles, analysis, design considerations, and experimental results are presented. Index Terms--Phase-shifted full-bridge (PSFB) converter, plasma display panel (PDP), voltage-doubler-type rectifier.

In this paper, a systematic review of bridgeless power factor correction (PFC) boost rectifiers, also called dual boost PFC rectifiers, is presented. Performance comparison between the conventional PFC boost rectifier and a representative member of the bridgeless PFC boost rectifier family is performed. Loss analysis and experimental efficiency evaluation for both CCM and DCM/CCM boundary operations are provided. Index Terms--Bridgeless power factor correction (PFC), common-mode noise, continuous-conduction mode (CCM), discontinuous-conduction mode (DCM)/CCM boundary, dual-boost PFC rectifier, single-phase rectifier.

A three-phase, multilevel rectifier using active voltage injection with one MOSFET device is presented. The injector consists of a bidirectional switch that modifies the behavior of a 12-pulse rectifier resulting in either 24-pulse or multilevel pulsewidth-modulated (PWM) operation. The resultant input currents are almost sinusoidal, the line current THD being 2.36% for 24-pulse operation and 1.06% for PWM operation. The MOSFET current is 2.9% of the load current. The circuit operation, idealized waveforms and modulation strategy are explained and experimental results are presented. Index Terms--High-power factor rectification, three-phase multipulse rectifier.

Diode rectifiers have been widely used for an ac-to-dc converter. A big problem is that they include large harmonic components in the input currents. A 12-pulse configuration is useful for reducing them, but it still includes the (12 m[+ or -]1)th (m: integer) harmonics in the input currents. In order to further reduce the input current harmonics a single-phase square wave auxiliary voltage supply is inserted in the middle dc bus. It reduces harmonics especially the 11th and 13th and the harmonic characteristic becomes almost equivalent to a 24-pulse rectifier. Theoretical analysis of the combined 12-pulse diode rectifier with the auxiliary supply is presented, and a control method of the auxiliary supply is proposed. The reduction in the input current harmonics is verified by simulation and experimental results. The auxiliary supply is also applied to a 12-pulse thyristor rectifier. Index Terms--Auxiliary voltage supply (AVS), diode rectifier, harmonic reduction, thyristor rectifier, twelve-pulse converter.

With steadily increasing wind turbine penetration, regulatory standards for grid interconnection have evolved to require that wind generation systems ride-through disturbances such as faults and support the grid during such events. Conventional modifications to the doubly fed induction generation (DFIG) architecture for providing ride-through result in compromised control of the turbine shaft and grid current during fault events. A DFIG architecture in which the grid side converter is connected in series as opposed to parallel with the grid connection has shown improved low voltage ride through but poor power processing capabilities. In this paper, a unified DFIG wind turbine architecture which employs a parallel grid side rectifier and series grid side converter is presented. The combination of these two converters enables unencumbered power processing and robust voltage disturbance ride through. A dynamic model and control structure for this architecture is developed. The operation of the system is illustrated using computer simulations. Index Terms--Doubly fed induction generator (DFIG), dynamic voltage restorer, voltage sag ride-through, wind turbine.

Active resonant tank (ART) cells are proposed in this paper to achieve zero-voltage-switching (ZVS) and eliminate body-diode conduction in dc-dc converters with synchronous rectifiers (SRs). In low-output-voltage dc-dc converters, SRs are widely utilized to reduce rectifier conduction loss and improve converter efficiency. However, during switches' transition, SRs' parasitic body diodes unavoidably carry load current, which decreases conversion efficiency because voltage drop across body diodes is much higher than that across SRs. Moreover, body diodes' reverse recovery leads to increased switching losses and electromagnetic interference. With the proposed cells of an ART, the body diode conduction of the SR is eliminated during the switching transition from a SR to an active switch, and thus body diode reverse-recovery-related switching and ringing losses are saved. An ART cell consists of a LC resonant tank and an auxiliary switch. A resonant tank cell is charged in a resonant manner and energy is stored in the capacitor of the tank. Prior to a switching transition from a SR to an active switch, the energy stored in the tank capacitor is released and converted to inductor current, which forces the SR current changes direction to avoid conduction of the body diode and related reverse recovery when the SR turns off. Moreover, at the help of energy released from the ART, the active switch's junction capacitance is discharged, which allows the active switch turns on at ZVS. Since energy commutation occurs only during switching transition, conduction loss in the ART cell is limited. Moreover, the auxiliary switch turns off at ZVS and the SR operates at ZVS. The concept of ART cells is generally introduced and detailed analysis is presented based on a synchronous buck converter. Experimental results show the proposed ART cell improves conversion efficiency due to the reduced switching loss, body diodes' conduction, and reverse-recovery losses. Index Terms--Buck, converter, dc-dc, resonant tank, reverse recovery, synchronous rectifier (SR), topology, zero-voltage-switching (ZVS).

Three-phase multipulse ac-dc converters (MPC) are developed for improving power quality to reduce harmonics in ac mains and ripples in dc output. This paper deals with the multipulse ac-dc converter configurations, state of art, their performance, power quality aspects, components selection considerations, latest trends, future developments, and potential applications. It is targeted to provide broad perspective on multipulse converter technology to the researchers, engineers, and designers dealing with them. A classified fist of more than 250 research publications on the subject is also given for quick reference. Index Terms--AC-DC converters, harmonics reduction, multi-pulse, power quality, rectifiers.

In a phase controlled rectifier, the fastest response can be achieved by predictive current control without any overshoot. However, any error in the load parameters can cause steady state errors between a reference current and the feedback current because this current control scheme depends on the mathematical relationships between the output current, the firing angle, and the power source voltage. Thus, in the predictive current control, an accurate parameter is necessary for attaining a zero steady-state error. In this paper, the load resistance and inductance are estimated using the least square method of an online parameter calculation based on digitally sampled instantaneous voltage and currents. For the careful sampling of data and the reduction of the calculation time, a new timer-based gating algorithm is proposed and explained in detail. Using the proposed algorithm, the fastest current control performance in the transient state is obtained by the online correction of load parameters in various simulations and experimental results. Index Terms--Parameter estimation, phase controlled rectifier, predictive current control.

This paper introduces a new method for stability analysis and design of fast voltage-loop compensators in rectifiers with power factor correction (PFC). The method has few constraints and can be used with various implementations of the fast voltage loop. It is based on utilization of circle criterion, which unifies frequency domain and nonlinear system analysis. A step-by-step procedure of stability assessment and compensator design is described and demonstrated on two controller implementations. In the first system, the voltage-loop dynamic response of an experimental 200-W digitally-controlled boost-based PFC is improved with a self-tuning comb filter. In the second implementation, it is shown how the circle criterion can be used to design a fast voltage loop for controllers with regulation band, i.e., 'dead-zone' element for ripple elimination. Index Terms--Circle criterion, fast voltage loop, power factor correction (PFC).

A single-phase voltage-quadrupler rectifier with sinusoidal input current is presented. This has the circuit configuration that is based on the combination of a half-bridge rectifier and pump circuits. The circuit can be operated in the switching states for pumping action to pump twice the peak supply voltage onto each of the output capacitor and for forcing the input current to follow its sinusoidal reference in the vicinity of a zero crossing of the supply. The prototype tested, using the insulated gate bipolar transistors and a controller for the output voltage regulation, is implemented to investigate the operation. The experimental and the simulated results confirm that the input current can be waveshaped sinusoidally with a near-unity power factor. Index Terms--Half-bridge, insulated gate bipolar transistor (IGBT) modules, pump circuit, single-phase rectifier, sinusoidal input current, voltage-quadrupler.

An inductor-capacitor (LC) filter is normally required at the input of a pulse-width modulation (PWM) current source rectifier (CSR), to assist in the commutation of switching devices and to mitigate line current harmonics. To dampen the LC resonance introduced by the input filter, an effective damping method is proposed in this paper by using a hybrid combination of a virtual harmonic resistive damper and a three-step control signal compensator. The virtual harmonic resistor, which is immune to system parameter variations, can dampen the LC resonance caused by an external disturbance or control command changes without affecting the fundamental power flow. But the high-pass filter used for fundamental component elimination leads to poor dynamics. Therefore, a proposed three-step compensator is inserted into the DC current closed-loop control path which can effectively eliminate the resonance within the control loop by shaping the modulation signal. Compared to the two-step Posicast controller, the proposed three-step compensator has significant implementation advantages in medium voltage CSRs, where a low switching frequency is needed. By using a hybrid combination approach, dynamics of the virtual harmonic resistor can be improved with the transient overshoot mitigated by the three-step compensator. At the same time, the parameter sensitivity of the three-step compensator can be reduced, as any residual resonant oscillations can be dampened by the virtual resistor. Simulation and experimental results are provided to verify the effectiveness of the proposed approach. Index Terms--Active damping, current source rectifier, Posicast controller, three-step compensator, virtual harmonic damper.

In this paper, a four-switch voltage-doubler boost rectifier is analyzed. A new control scheme is proposed to eliminate the output voltage imbalance when the load is unevenly distributed across the two output dc rails. Unipolar pulsewidth modulation switching patterns are adopted to slow down the discharging rate of the output capacitor with the lower voltage. No dc or out-of-phase component is injected in the source current. Thus, the unity input power factor can be genuinely achieved. Two hysteresis comparators are employed in the presented controller. One is used for the source current to track its command. The other comparator is to confine the output voltage imbalance within a reasonable level. Modified averaged circuit models are adopted to derive the limits of the ratio of the dual loads for output voltage balance. Experimental results on prototype circuits confirm tightly with the theoretical analysis. Index Terms--Compensation strategy, dual loads, four-switch half-bridge (HB) boost rectifier, output voltage imbalance, single load.