Input Power Factor Research Articles

A Two-Stage Output Current Ripple-Free Flyback-Buck AC-DC LED Driver with High Power Factor

A two-stage output current ripple-free flyback-buck AC-DC LED driver with high power factor is presented. The first stage is a flyback power factor correction (PFC) converter and the second stage is a ripple-free zero-voltage-switching (ZVS) synchronous buck converter. Nearly unity input power factor can be obtained by using a flyback PFC converter. In the second stage, the output capacitor is eliminated because the output current ripple is completely removed by utilizing additional circuit composed of a coupled inductor, a series inductor, and a series capacitor. Thus, the proposed circuit is suitable to long-lifespan LED driver. Moreover, by using synchronous switch, ZVS condition is satisfied in the main switches and also the reverse recovery problems in the body diode of switch are solved. Therefore, the efficiency, lifespan and the stability for LED driver is improved. A prototype LED driver for 80W is built up to verify theoretical analysis and experiment results are presented.

Unity Power Factor Operation of Indirect Matrix Converter Tied to Unbalanced Grid

This paper presents a new control method for indirect matrix converter operating under unbalanced grid voltages. The proposed method aims to achieve balanced output voltages as well as a near unity input power factor operation. First, an opportune reference current accurately generated, and a proportional integral resonant controller are designed in a dq reference frame that is synchronized with the positive sequence of the grid voltages so as to achieve a perfect tracking of input reactive power reference. Then, a real-time estimator of the virtual dc-link voltage is developed with the aim to provide balanced output voltages; therefore, an almost constant active power free of low frequency ripple is supplied from the grid. Experimental results are presented to verify the feasibility and effectiveness of the proposed control method.

A Simple Method for Sinusoidal Input Currents of Matrix Converter Under Unbalanced Input Voltages

When matrix converter works under unbalanced input voltages, sinusoidal input currents could be obtained if the input power factor angle in conventional control strategy is modified based on the positive and negative sequence components of input voltages. Some existing literature realized this goal by using sequence component separation, which was usually complicated and/or storage-consuming. Instead, a simple realization method is proposed by this letter to obtain sinusoidal input currents, which constructs the expected input power factor angle by filtering the square of input voltage vector with a notch filter. The proposed method is easy to implement, since no sequence extraction algorithm is required. Experimental results demonstrate that compared with the existing realization methods, the proposed method reduces the computation time and storage space with identical performance of improving input currents quality.

A novel adaptive control approach for three-phase improved power quality converter under distorted and unbalanced AC mains

In this paper, a novel simplified control technique is proposed to control three-phase improved power quality converter for disturbed AC mains. The proposed technique is based on retransformation of Clarke transformation. The trajectory of reference vector is very important for SVM technique to obtain exact switching times. Due to disturbed supply in a three-phase system, the trajectory of reference vector gets affected which results in low input power factor, high input current THD and high ripple factor of the DC output voltage in power converters. In the proposed technique, PI operation is implemented for the retransformation of Clarke transformation. The modified Clarke transformation generates a required shape of the trajectory of reference vector so that the system performs satisfactorily even under disturbed AC mains. Moreover, the proposed scheme has the advantage of fast response and is simple enough to be implemented in a single-chip microcontroller. The simulation results are presented to demonstrate the effectiveness of the new proposed control technique.

An Analysis on the Effectiveness of Harmonics Reduction for Variable Frequency Drive by Reactors

Recently, due to the rapid development of Power Electronics, the usage of Non Linear Load variable frequency drivers (VFDs) is increasing in the electric propulsion vessels and offshore plants. And harmonics which is generated by the variable frequency drives is an important issue should be solved. Ac line reactors and dc link reactors are widely used in variable frequency drives to improve the drive performance such as reducing input current harmonics, elevating input power factor, and protecting the drives from surges, etc. The effectiveness of both types of reactors in reducing input harmonics is affected by the loading of the drives and the system source impedance. And it considered that inductance of DC link reactors should be about 1.7 times of AC line reactors for same effect. The rules to evaluate the needs and effectiveness using ac line or dc link reactors are proposed for practical appications. In this paper, a simulation is performed to investigate of such factors using software PSIM.

Modelling and control of VIENNA rectifier a single phase approach

Input harmonic and power factor (PF) regulations necessitate the use of front end active PF correction (APFC) circuit for power electronic converters. In recent times, the VIENNA rectifier has become a popular choice for three-phase APFC applications. The converter is a fifth-order system and results in a highly complex model. This calls for a complex control design procedure and involves enormous computation requiring the use of a high end digital signal processor (DSP). This can be simplified if the order of system is reduced. In this study, it is proposed to decouple and analyse the converter as three independent single phase units operating in parallel with current mode control, thereby reducing the order to two, simplifying the analysis and control design. The transfer function of the proposed small-signal model is derived and its Bode plot is drawn. A high bandwidth inner average current controller and a low bandwidth outer voltage controller are designed to obtain a 60° phase margin. With the proposed design, a 10 kW prototype VIENNA rectifier is developed with a low cost analogue integrated circuit (IC) and validated. The results obtained prove the accuracy of the proposed model and effectiveness of the control. Single phase operation is also made feasible with the proposed technique.

Neural Network Based Control for Power Quality Improvement and Voltage Regulation in Multi Output Switched Mode Power Supply

Medical electronic equipments and personal computers stand in need of switched mode power supplies (SMPS) with isolated and regulated voltages of ± 12V, ± 5V and + 3.3 V. In this paper a neural network controlled forward boost converter based SMPS of 175 W rating is proposed. The SMPS is designed to have isolated and regulated voltages of ± 12V and ± 5V suitable for PC power supply. Power quality in terms of, total harmonic distortion (THD) and input power factor and output voltage regulation are analyzed for variation in supply voltage and load conditions by simulating the proposed circuit in MAT LAB/Simulink software. To highlight the performance of the proposed multi output SMPS, it is compared with that of conventional controller. Simulation results prove the efficacy of the proposed neural network based control for multi output SMPS. Improved power quality in terms of THD, almost unity power factor and voltage regulation are achieved for varying source and load condition.

Single-Phase AC–AC Double-Star Chopper Cells (DSCC) Converter Without Common DC-Link Capacitor

This paper presents a single-phase ac–ac converter based on a modular multilevel cascade converter (MMCC) with double-star chopper cells (DSCC). The converter topology is composed of three DSCC legs, in which the middle leg is shared, and it does not present a common dc-link capacitor. It is suitable for nonregenerative or regenerative low-power and medium-power ac–ac conversions. A voltage-balancing control is presented for regulating the floating dc capacitor voltages. Furthermore, a grid current and load voltage control is presented to correct the input power factor and to ensure input/output sinusoidal waveforms. A phase-shifted carrier (PSC) pulsewidth modulation (PWM) commands submodules (SMs) using half of PSCs, preserving the characteristics of conventional modulation. Details about a downscaled prototype rated at 3.3 kW and 220 V are also presented. The experimental results allow validating the control strategies and the effectiveness of the proposed system.

Independent Control of Input Current, Output Voltage, and Capacitor Voltage Balancing for a Modular Matrix Converter

This paper presents a novel control scheme for the modular matrix converter (MMxC), in terms of balancing capacitor voltages in addition to controlling output voltage and input current along with a comprehensive mathematical model. The proposed technique has been designed based on a fully decoupled current control of the positive-, negative-, and zero-sequence components of each MMxC subconverter in addition to the feedforward instantaneous power control to suppress the capacitor voltages fluctuation. The frequency of the zero-sequence is the output frequency for the load. Therefore, the positive-sequence current component is used to control the input current to achieve unity input power factor, the negative-sequence current component is used to balance the capacitor voltages among all MMxC arms, and the zero-sequence current component is used to control the output voltage. The effectiveness of the proposed control scheme for controlling the MMxC has been verified theoretically, using simulation software, and experimentally, using a laboratory prototype based 3 kVA, 200 V.

A Novel Wall-Switched Step-Dimming Concept in LED Lighting Systems Using PFC Zeta Converter

This paper presents the design, simulation, and implementation of a non-isolated discontinuous conduction mode operated Zeta-converter-based light-emitting diode (LED) driver with the novel wall-switched step-dimming concept to achieve power quality improvement at universal ac mains. The power-factor-corrected Zeta converter maintains constant output current to an LED load of 26 W and conserves the power quality requirements as per IEC 61000-3-2 for class C equipment with high efficiency. Moreover, to obtain cost benefit and size reduction, this converter utilizes reduced control circuitry for general-purpose LED lighting solutions. A cost-effective single-level dimming concept is implemented with current injection technique using a Zeta converter. A prototype is developed using AP1682, which utilizes pulse frequency modulation technique to regulate the output current for improving the input power factor and low total harmonic distortion (THD) of the input current. At full load and rated voltage of 220 V, the measured input power factor is 0.993 and current THD is 2.81% with an efficiency of 90.51%.

Realization of SVM Algorithm for Indirect Matrix Converter and Its Application in Power Factor Control

Compared with AC-DC-AC converter, matrix converter (MC) has several advantages for its bidirectional power flow, controllable power factor, and the absence of large energy storage in dc-link. The topology of MC includes direct matrix converter (DMC) and indirect matrix converter (IMC). IMC has received great attention worldwide because of its easy implementation and safe commutation. Space vector PWM (SVM) algorithm for indirect matrix converter is realized on DSP and CPLD platform in this paper. The control of the rectifier and inverter in IMC can be decoupled because of the intermediate dc-link. The space vector modulation scheme for IMC is discussed and the PWM sequences for the rectifier and inverter are generated. And a two-step commutation of zero current switching (ZCS) in the rectifier is achieved. Input power factor of IMC can be changed by adjusting the angle of the reference current vector. Experimental tests have been conducted on a RB-IGBT based indirect matrix converter prototype. The results verify the performance of the SVM algorithm and the ability of power factor correction.

Control of the reactive power supplied by a WECS based on an induction generator fed by a matrix converter

This paper introduces an integrated energy storage and reactive power compensation in a large wind power plant, and it deals to regulate the reactive power supplied by a variable-speed Wind Energy Conversion System (WECS), based on an induction generator fed by a Matrix Converter (MC). The control strategy used in this paper is input current observer, implemented using an estimation of the modulation index, and a nonlinear control loop that regulates the displacement angle at the matrix converter input. This paper is described the implemention of the matrix converter to control the reactive power by using the Space Vector Pulse Width Modulation (SVPWM) technique in large wind farms and combining them into one system to maintain stability control of the wind power plant. Control of reactive power increases the regulating capacity, which can provide voltage stability in the wind farm. In this work, Matlab/Simulink TM model and simulation of the three phase matrix converter have been performed using the space vector control algorithm. The algorithm uses a simpler method than the other control algorithms to control the input power factor. To verify the performance of the proposed Matrix Converter, modulation strategy, and control design methodology, various simulation results are presented.

An Electronically Isolated 12-Pulse Autotransformer Rectification Scheme to Improve Input Power Factor and Lower Harmonic Distortion in Variable-Frequency Drives

Diode rectifier front-ends with large dc bus capacitors used in variable-frequency drives draw discontinuous current from the power system, resulting in a poor input power factor and high input current distortion. The 12-pulse and 18-pulse techniques used to reduce input current harmonics are popular because of their simplicity but are bulky and expensive. Autotransformer techniques require additional external magnetic components that are bulky and add to the cost of the system. A new electronically isolated 12-pulse autotransformer topology that does not need bulky external magnetic components is proposed in this paper. The proposed topology employs active switches to achieve electronic isolation between the two rectifiers, resulting in continuous input current with reduced harmonics. The proposed nonregenerative active scheme achieves less than 5% total harmonic distortion at a much lower cost compared with other passive or active topologies currently in the market. Experimental results from a 240-V 75-hp system are given to prove the concept.

Isolated AC/DC Offline High Power Factor Single-Switch LED Drivers Without Electrolytic Capacitors

Energy-efficient residential lighting such as household light-emitting diode (LED) lamps with ac input require an ac/dc converter (or driver) with large output capacitance to minimize the low frequency LED current ripple. The energy storage capacitor used in the conventional ac/dc LED driver is usually an electrolytic capacitor due to its low cost and high energy density. However, the average lifetime of an electrolytic capacitor is at least 2–3 times less than that of an LED device. Hence, the potential lifetime of the LED lamp is significantly affected by the presence of the electrolytic capacitor in the driver circuit. In this paper, two novel isolated single-switch ac/dc high power factor LED drivers without using any electrolytic capacitors are proposed. In the proposed circuits, the energy storage capacitor is moved to the rectifier side, with a three-winding transformer used to provide isolation; input power factor correction as well as to store and provide the required energy to the output. As a result, the energy storage capacitance is significantly reduced, which allows film capacitor to be used to replace the conventionally used electrolytic capacitors. The circuit’s operating principles and its characteristics are described in this paper. Simulation and experimental results are given on a 120 $\text{V}_{\rm rms}$ , 12 W prototype to confirm that a power factor of at least 0.96 is achieved.

A Novel Control Scheme for Power Factor Improvement in Modified Bridgeless Boost Converter

In Green Energy technologies like wind energy conversion systems and Domestic applications like SMPS and UPS systems, the input voltage amplitude and input frequency are time varying in nature. Fast-Escalating and extremely challenging high efficiency requirements for AC-DC power supplies for notebooks, desktop computers are to minimize the power losses (Conduction losses). In the conventional rectifiers power losses are more and power factor is poor resulting in loss of efficiency. Normally, the bridgeless topologies, also referred to as dual boost power factor correction (PFC) rectifiers, may reduce the conduction losses by reducing the number of semi-conductor components in the line current path. Power supply units have to make the load compatible with the source. The presence of non-linear load results in poor power factor operation and produces harmonic components in the line. So PFC techniques are necessary to meet harmonic regulations and standards such as IEC 61000-3-2 and IEEE 519. A modified bridgeless topology may be used for such applications. A novel switching controller is developed that regulates the input resistance to a desired value. Hence input power factor is unity and also the total harmonic distortion is controlled to a tolerable limit. In the proposed model, the modified bridgeless boost converter is activated in to a pure resistance mode. Finally the performance of the modified bridgeless boost converter is compared with the existing basic bridgeless boost converter.

The Three-Level Sine-Wave Inverter with Power Factor Correction (PFC)

Nowadays, the uninterruptible power supply (UPS) is important in reliability for electric device. The UPS need high quality electricity. Therefore, the simulation of the three-level sine-wave inverter with power factor correction (PFC) is proposed in this paper. Moreover, the circuit’s guidelines of the active PFC controller in the active PFC and the sinusoidal output voltage are also presented. Validity of the proposed the three-level sine-wave inverter with the active PFC is confirmed by simulation. The simulation results show the very small current harmonics, the input power factor most nearly unity and constant output voltage when the suddenly step-load changed.

Voltage sensorless control of the three‐level three‐switch Vienna rectifier with programmable input power factor

The three-level, three-switch Vienna rectifier is fast emerging as the preferred topology for the high-power factor front end converter in many applications. Conventional control algorithms for the Vienna rectifier requires sensing of both the supply voltage and the line current. However, in many applications, where an electrical generator feeds the rectifier, the ‘supply voltage’ is not available for measurement. Even for grid-connected applications the supply voltage may contain significant harmonic distortion which, in turn, increases the harmonic distortion of the rectifier input current. To mitigate these disadvantages, this study presents a novel voltage sensorless control algorithm for the Vienna rectifier. Voltage sensorless control algorithms reported in the literature for this rectifier, so far permit only unity rectifier terminal power factor operation. In contrast, the proposed control algorithm can operate the rectifier at programmable power factor. For the verification of the algorithm, experiments were conducted on a laboratory prototype of the Vienna rectifier using both voltage sensorless and sensor-based control algorithms. Performances of both these algorithms were found to be similar under transient conditions. The voltage sensorless controller achieved better input line current total harmonic distortion in steady state.

Simulation and Practical Analysis on Power Factor Correction Techniques for Welding Applications

The most of the industrial welding applications involving of electronic circuits such as AC-DC, and DC-AC and AC-DC converters. The input power factor of such a system is reduced due to the presence of more harmonics due to the non-linear devices within the converters which leads to creates more adverse effects. There by a need of suitable AC-DC converter with power factor correction technique to condition the supply current. The power factor correction rectifier that requires best current control from i) Peak current control ii) Average current control and iii) Hysteresis current control. This paper presents a comparative analysis from above mentioned power factor correction control topologies. The simulation of these control techniques are carried out using “Plecs” with “MATLAB/SIMULINK”. The simulation results shows that Hysteresis control has low THD, good DC link voltage regulation and better performance than other control techniques. The same control technique is implemented in TMS320F2812 DSP and results are proved.

Front-End Converter With Integrated PFC and DC–DC Functions for a Fuel Cell UPS With DSP-Based Control

This paper presents the development of a boost converter with integrated power factor correction (PFC) and dc-dc functions for a proton exchange membrane fuel cell (PEMFC) uninterruptable power supply (UPS). Through the use of a passive resonant soft-commutation cell, which besides providing improvements in efficiency and reduced electromagnetic interference, produces a naturally controlled supercapacitor charger circuit. Supercapacitors are employed in order to provide a proper startup of the PEMFC and to improve its dynamic response. The control strategy is implemented using a digital signal processor and is based on the average current control method for sinusoidal input current imposition ensuring, therefore, a high input power factor and low harmonic distortion of current. The main features of the proposed solution are the use of a PEMFC as an energy storage system, which replace the battery banks commonly used in UPS systems, eliminating the common drawbacks related to working life and maintenance issues, and the use of a front-end converter with integrated PFC and dc-dc functions eliminating the necessity of using an additional and dedicated dc-dc converter for the PEMFC. During power failure or even in conditions of severe voltage sags on the ac mains, the PEMFC is activated assuring the continuous power supply to the electronic load connected to the dc link. In this paper, the authors present the full study description including experimental results that corroborate with the theory herein presented.

Implementation of Hybrid Filter for 12-Pulse Thyristor Rectifier Supplying High-Current Variable-Voltage DC Load

This paper presents a parallel combination of a shunt-connected passive filter and a distribution static compensator (DSTATCOM) for a 12-pulse thyristor rectifier feeding a high-current variable-voltage electrolyzer load. Since the process requires variation of voltage and current over a wide range, the reactive power consumed by the thyristor rectifier also varies enormously. As the passive filter is only able to provide a fixed compensation, the DSTATCOM is used to meet variable reactive power demand to keep the input power factor high even at partial load. In order to keep the DSTATCOM rating small, the bulk of reactive power is supplied by the dominant harmonic passive filter. Moreover, DSTATCOM does not provide any harmonic compensation, which is also taken care by the passive filter. Design and control of this system are discussed briefly, and more emphasis is laid on the implementation of the hybrid filter. An experimental system is tested rigorously, and detailed results are presented.