Three-phase diode rectifier with a low input current distortion and regulated output voltage

ABSTRACTThree-phase converters using diode or silicon-controlled rectifier (SCR) are widely employed to convert the commercial AC supply to DC. Such converters inject harmonics into the power supply system and thereby distort supply system voltage waveform. A simple input current wave-shape improvement technique using a shunt-connected harmonic current compensator is presented in this work, intended to reduce the total harmonic distortion (THD) of input current of three-phase diode and SCR phase-controlled rectifiers operating with inductive loads, by matching them to the specific converter as a combined package. The compensator proposed here comprises of a three-limb voltage source converter using insulated-gate bipolar transistor, working on instantaneous current and voltage measurements of the compensator only and not of the load. The technique uses a simple feedforward control for AC source current harmonic compensation of rectifiers without monitoring the AC line currents, i.e. use of online computation. The proposed system is simulated and tested on a laboratory prototype. The measured input current THD values without additional line filters are found to be below 8.3%, which is within acceptable limits, proving that the new technique is capable of compensating predetermined current harmonics of diode or SCRs.

This paper describes a technique for shaping the input current to a three-phase diode rectifier using a two-switch series-connected dual boost converter and a three-phase bidirectional switch circuit. Circuits are described for generating a single voltage DC output, "single DC-rail", or a dual output DC voltage using center-tapped capacitors, "split DC-rail". Both rectifier types can be operated with the boost inductors located either on the DC or the AC side of the rectifier. The resultant rectifier circuit configurations have an excellent immunity to the "shoot-through" fault condition and use active switching elements with low per-unit current ratings and low switching losses. These features increase the reliability factor and lower the cost penalty associated with unity fundamental power factor three-phase rectifiers. Test results are presented for the rectifiers using simulation and experimental results.

To reduce the conduction loss, a novel three-phase current source rectifier, named Delta-type Current Source Rectifier (DCSR), has been proposed in previous research. This rectifier has delta-type connection on its input side, and its dc-link current can be shared by multiple devices at a time to reduce up to 20% conduction loss. A high-efficiency modulation scheme for DCSR has been proposed, where the conduction states involve more switches to share the dc-link current. However, it causes current distortion when the input voltages have intersections. In this paper, the phenomenon is analyzed in detail. The clamped voltage on the diode bridge will fluctuate at the voltage intersections, resulting in false current pulse and distortion. An improved modulation scheme is then proposed for DCSR to reduce the input current distortion without sacrificing much efficiency. Through experiment in a 7.5 kW prototype, its effectiveness is verified and the total harmonic distortion (THD) of the input current is reduced dramatically.

In this paper, a new bridgeless single phase ac-dc power factor correction (PFC) rectifiers based on Buck topology operating in Discontinuous Capacitor Voltage Mode (DCVM) is proposed. The bridgeless topology and the presence of only one or two semiconductor switches in the current flowing path during each interval of the switching cycle result in lower conduction losses compared to the conventional DCVM Buck PFC rectifier. The DCVM operation offers additional advantages such as: zero-voltage turn-off in the power switches, zero-voltage turn-on in the output diode, and continuous input current. Hence, the electromagnetic interference (EMI) noise emission is minimized. The converter achieves high power factor naturally with low total harmonic distortion (THD) in the input current. Theoretical analysis and experimental results for 100 W/48 V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dc</sub> at 100 V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rms</sub> line voltage are provided to evaluate the performance of the proposed scheme. The measured conversion efficiency reached 96.4%.

In this paper, a digital-based pulse train (PT) control technique for a boost power factor correction (PFC) converter operating in a discontinuous conduction mode (DCM) is presented, which can achieve nearly unity power factor (PF) over a universal input voltage range. Different from traditional digital control techniques, which usually require complex arithmetic operations, the digital-based PT control technique only needs a simple operation. Besides, a DCM boost PFC converter with digital PT control can operate at a high switching frequency, which is less dependent on the processing speed of a digital controller. Thus, the proposed control strategy can be implemented with general purpose digital controllers, such as low-speed and low-cost microcontroller unit, for the DCM boost PFC converter where the cost is a focus. The operation principle of the digital PT controlled DCM boost PFC converter is analyzed. Experimental results are provided, which show that high PF and low input current total harmonic distortion can be maintained over a universal input voltage range of 90–264 V ac.

A high-quality rectifier for supplying resistive loads is presented. It features high power factor, low input current distortion and high efficiency. It is a step-down power converter and its device stresses are the same as for a buck power converter, while input current is continuous. The power converter, suitable for heating and lighting applications, is analyzed and experimentally tested on a 1 kW prototype.

This paper proposes a new modulation technique that can reduce the current distortion and extend the current reconstruction range for a three-phase inverter using only dc-link sensor. The proposed pulsewidth modulation (PWM) technique is a hybrid method which consists of space vector modulation method and the PWM method without using null switching states. The former provides low current distortion; however, it is with narrower current reconstruction range. In contrast, the latter extends the current reconstruction range at the cost of higher current distortion. For the proposed method, in the measurable region of space vector modulation method, space vector modulation is used to reduce the current distortion. Moreover, as the modulation range is out of the measurable region, the PWM method without using null switching states is applied to extend the current reconstruction range. Furthermore, the current reconstruction limitation using only dc-link sensor is analyzed. The analysis shows that the reduction of PWM switching frequency and acquisition time can extend the current reconstruction range. Comparison of experimental results derived from a field-programmable gate array-based controlled inverter is included. It will be demonstrated that using the proposed hybrid PWM technique, the three-phase current signals of the inverter can be reconstructed even under very low modulation index range while providing low current harmonic distortion of inverter output.

The paper proposes a new modulation technique which can reduce the current distortion and extend the current reconstruction range for three-phase inverter using only DC-link sensor. The proposed PWM technique is a hybrid method which consists of space vector modulation method and the PWM method without using null switching states. The former provides low current distortion, however it is with narrower current reconstruction range. In contrast, the later extends the current reconstruction range at the cost of higher current distortion. For the proposed method, in the measurable region of space vector modulation method, space vector modulation is used to reduce the current distortion. Moreover, as the modulation range is out of that measurable region, the PWM method without using null switching states is applied to extend the current re-construction range. Furthermore, the current reconstruction limitation using only DC-link sensor is analyzed. The analysis shows that reduction of PWM switching frequency and acquisition time can extend the current re-construction range. Comparison of experimental results derived from an FPGA-based controlled inverter is included. It will be demonstrated that using the proposed hybrid PWM technique the three-phase current signals of inverter can be reconstructed even under very low modulation index range while providing low current harmonic distortion of inverter output.

This paper presents a multi-cell single-phase high power factor boost rectifier in interleave connection, operating in critical conduction mode, employing a soft-switching technique, and controlled by field programmable gate array (FPGA). The soft-switching technique is based on zero-current-switching (ZCS) cells, providing ZC (zero-current) turn-on and ZCZV (zero-current-zero-voltage) turn-off for the active switches, and ZV (zero-voltage) turn-on and ZC (zero-current) turn-off for the boost diodes. The disadvantages related to reverse recovery effects of boost diodes operated in continuous conduction mode (additional losses, and electromagnetic interference (EMI) problems) are minimized, due to the operation in critical conduction mode. In addition, due to the interleaving technique, the rectifier's features include the reduction in the input current ripple, the reduction in the output voltage ripple, the use of low stress devices, low volume for the EMI input filter, high input power factor (PF), and low total harmonic distortion (THD) in the input current, in compliance with the IEC61000-3-2 standards. The digital controller has been developed using a hardware description language (VHDL) and implemented using a XC2S200E-SpartanII-E/Xilinx FPGA device, performing a true critical conduction operation mode for all interleaved cells, and a closed-loop to provide the output voltage regulation, like as a pre-regulator rectifier. Experimental results are presented for a implemented prototype with two and with four interleaved cells, 400 V nominal output voltage and 220 Vrms nominal input voltage, in order to verify the feasibility and performance of the proposed digital control through the use of a FPGA device

The paper describes the operation of an AC-DC power converter in which the harmonic distortion in the input current is reduced using a second harmonic-injected PWM scheme. The boost power converter uses a constant switching discontinuous current mode. Expressions for the harmonic components are derived. Simulated and experimental waveforms of an AC-DC power converter are presented and the total harmonic distortion computed. >

In this paper, a bee colony optimization (BCO) algorithm is adapted to the current control strategy of power factor (PF) correction for a Sheppard-Taylor converter. The control approach is developed to eliminate the input current harmonics in the converter. The BCO algorithm is a new population-based search algorithm which is one of the metaheuristic techniques based on swarm intelligence. This algorithm depends on modeling the natural behavior of real honey bees. In this approach, duty cycles are generated by the BCO algorithm for the Sheppard-Taylor converter switch to obtain unity PF (UPF) and lower total harmonic distortion of the input current. The duty cycles for half a line period are calculated and stored in a lookup table. By synchronizing the memory with the line, near-unity PFs can be achieved in an operating point. The feedforward is also used into the control algorithm with the maximum value of the input voltage. The implementation of feedforward improves the converter performance. The input current of the converter is operated in continuous conduction mode. The simulation and experimental results show that the proposed control strategy works well and the UPF can be achieved with wide input voltage, load, and parameter variation. The results are compatible with the International Electrotechnical Commission (IEC) 61000-3-2 current harmonic standard.

Harmonic analysis currently plays an important role for the power quality analysis because the non-linear loads, as source of the harmonic distortion, have significantly increased. The harmonic distortion influences power quality in power systems such as overheating of electrical equipment and aging of electrical equipment. Therefore, non-linear loads should be monitored in real time. This research proposes the design and implementation of the prototype current harmonic analysis that can be applied in real time based on S-transform Method. The equipment of this prototype can be explained as follows: CT-235, TZ2L9 and CT for KWH meters as current sensor, microcontroller AT mega 8535 as data acquisition, and Visual Basic software as displaying current waveform, current spectrum, rms current value, and total harmonic distortion (THD) for current. S-transform method is used to obtain the THD for current. The experimental result is validated by FLUKE 43B and the THD for current is accurately measured.

A new magnetic-coupled high power factor converter (MCHPFC) with a single switch/single stage is proposed. The proposed converter gives good power factor correction, low current harmonic distortions, and tight output voltage regulation. The prototype shows that the IEC555-2 requirements are met satisfactorily with nearly unity power factor. A proposed MCHPFC is particularly suited for low-power-level power supply applications.

The Power Factor Correction (PFC) in Switched Reluctance (SR) motor is discussed in this article. The SR motors are applicable for multiple applications like electric vehicles, wind mills, machineries etc. The doubly salient structure of SR motor causes the occurrence of torque ripples, which affects the power factor of the motor. To improve the power quality, the power factor has to be corrected and the ripples have to be minimized. In order to achieve these objectives, a novel power factor correction (PFC) method is proposed in this work. Here, the conventional Diode Bridge Rectifier (DBR) is replaced by a Bridgeless Hybrid Resonant (HR) converter, which assists in improvising the output in a wider range. The converter is chosen because of having variety of beneficial measures including high gain. The converter’s output is fed to the SR motor by means of an asymmetric Bridge Resonant (BR) converter. The proposed converter operates in continuous mode of conduction with the switching frequency of 10 KHz. A hysteresis current controller and Proportional Integral (PI) controller are utilized for reducing the harmonics in the source current along with the regulation of output voltage. In addition, the speed control of SR motor is accomplished by means of the Whale Optimization Algorithm (WOA) assisted PI controller. The proposed methodology is effective for the control of unity power factor, torque and current ripples. The Total Harmonic Distortion (THD) of the source current is also minimized, which suits the standard of International Electrotechnical Comission IEC 61000-3-2. By this methodology, the power factor of 0.99 is achieved with 97% efficiency and 3.92% THD. The proposed methodology is validated in simulation by MATLAB and in hardware by FPGA Spartan 6E.

A comparison of fuzzy self‐tuning (FST), sliding mode control (SMC) and conventional proportional–integral (PI) control methods is performed under unbalanced grid conditions using a bridgeless power factor correction (PFC) converter. The bridgeless PFC converter operates the correction of AC line current to obtain a DC output voltage without full bridge rectifier based on these control methods. These control methods generate the duty cycles to provide higher unity power factor and lower total harmonic distortion of input current, even if AC line voltage is distorted. This study focuses on the performance analysis of FST and SMC methods adaptation to the input current for the bridgeless PFC converter and comparing with the conventional PI controller. Although the SMC method is only used in the current control loop, the FST method is used in both current and voltage control loops for eliminating harmonics of input current and regulating of output voltage. The performance of control methods is evaluated with a TMS320F2812 digital signal processor. The simulation and experimental results are compatible with the limits for harmonic current emissions, IEC 61000‐3‐2 and show that the FST and SMC are better than the conventional PI control method and FST is superior to the SMC.