Power Factor Correction Function Research Articles

Interleaved Modified SEPIC Converters with Soft Switching and High Power Factor for LED Lighting Appliance

A novel ac/dc LED driver with power factor correction and soft-switching functions is proposed. The circuit topology mainly consists of two modified single-ended primary inductance converters (SEPIC) with interleaved operation. The first half stage of SEPIC operates like a boost converter and the second half stage operates like a buck–boost converter. Each boost converter is designed to operate in discontinuous current mode (DCM) to function as a power factor corrector (PFC). The two buck–boost converters that share a commonly coupled inductor are designed to operate at near boundary conduction mode (BCM). Without using any active clamping circuit, auxiliary switch or snubber circuit, the active switches can achieve zero-voltage switching on, and all diodes achieve zero-current switching off. First, operation modes in steady state are analyzed, and the mathematical equations for design component parameters are derived. Finally, a prototype circuit of 180 W rated power was built and tested. Experimental results show satisfactory performance of the proposed circuit.

A Novel Integrated Electronic Lighting Driver Circuit for Supplying an LED Projection Lamp with High Power Factor and Soft Switching Characteristics

The traditional light source of projection lamps adopts a halogen lamp, which has the advantages of high brightness, but its luminous efficiency is not good and consumes energy. A light-emitting diode (LED) has the characteristics of high luminous efficiency and energy savings and can be used as a new light source for projection lamps. The conventional two-stage electronic lighting driver circuit for supplying an LED projection lamp is composed of an AC-DC converter with power factor correction (PFC) as the first stage and a DC-DC converter for providing rated lamp voltage and current as the second stage. The conventional LED projection lamp driver circuit has more circuit components, a higher cost and limited efficiency. Therefore, this paper proposes a novel electronic lighting driver circuit for supplying an LED projection lamp with PFC function, which integrates a modified stacked dual boost converter and a half-bridge LLC resonant converter into a single-stage power-conversion circuit. The inductor inside the modified stacked boost converter is designed to operate at discontinuous conduction mode (DCM) for the driver circuit achieving PFC. Wide bandgap semiconductor devices silicon carbide (SiC)-based Schottky diodes are utilized to reduce power diode losses, and soft switching is implemented in the proposed LED projector lamp driver circuit to reduce the switching losses of the power switches and thus improve circuit efficiency. This paper has completed a single-stage prototype driver circuit for an LED projection lamp with PFC function, and the prototype circuit has a high power factor (PF > 0.98), low input current total-harmonic-distortion (THD < 6%) and high efficiency (>89%) in the case of an AC input power supply with an RMS value of 110 volts, and both power switches have the characteristics of soft switching.

A Hybrid Quasi-Single-Stage AC-DC Converter with Low Twice-Line-Frequency Output Voltage Ripple

Power factor correction (PFC) converters have been frequently employed in various switching power supply devices to reduce input current harmonics. However, the PFC converter suffers from an obvious twice-line-frequency output voltage ripple due to the instantaneous power imbalance between constant output power and variable input power. Suppression of twice-line-frequency ripple usually can be realized by the post-stage DC-DC converter of the two-stage cascade PFC converter; however, the two-stage cascade PFC structure is challenging to realize high efficiency since the energy is transferred twice. To achieve high power factor, high efficiency, and low twice-line-frequency ripple, a hybrid quasi-single-stage (QSS) AC-DC converter is presented in this paper, which consists of a dual output hybrid Boost/Flyback PFC converter and a Buck ripple compensation circuit (RCC). The fundamental principles of the proposed converter and the critical conditions of operation mode transition are discussed in the paper. To confirm that the twice-line-frequency ripple is effectively suppressed, the small signal model of Buck RCC is built and analyzed. Moreover, the main characteristics, including operation mode transition angle, input current, power factor, and switching frequency of the proposed hybrid QSS AC-DC converter, are analyzed. By building a 120 W experimental prototype to validate the feasibility of the proposed hybrid QSS AC-DC converter, the experimental results show that the proposed converter can realize PFC function with high efficiency and extremely low twice-line-frequency output voltage ripple.

Single‐stage triple‐output Cuk power factor correction converter

SummaryTraditional multiple‐output AC‐DC power supply with power factor correction (PFC) function usually employs a two‐stage cascaded topology that is composed of prestage PFC converter and N independent poststage DC‐DC converters to achieve PFC and voltage or current regulation of N outputs. Hence, the conventional two‐stage cascaded multiple‐output AC‐DC power supply needs N + 1 magnetic components as power inductors or transformers and N + 1 controllers, which increases the cost and size of the multioutput converters. The conventional multiple‐string AC‐DC LED driving circuits usually employ a two‐stage topology to realize PFC and independent current regulation of each LED string. To address the issue of complexity, high cost, and large size of the two‐stage multistring LED driving circuit, a single‐stage triple‐output Cuk PFC converter is proposed by cascading boost converter and single‐inductor triple‐output buck converter with sharing main power switch in this paper. The topology operation principle, control strategy, design consideration, and operation characteristics of the proposed circuit are investigated in detail. With the switch sharing and inductor multiplexing technologies at the same time, the proposed converter utilizes only single‐stage converter to achieve PFC function, independent regulation of triple‐channel output current, and flicker‐free with low twice line frequency LED current ripple. The proposed converter is verified by a 50‐W experimental prototype of LED driver for triple string LEDs. The proposed converter only uses two power inductors and a set of controller to achieve greater than 0.945 PF, up to 90.5% efficiency, low LED current ripple, and independent current regulation for triple LED strings with different forward voltage, which may significantly reduce the cost and size of the traditional AC‐DC multistring LED driving circuit.

An AC-DC LED Integrated Streetlight Driver with Power Factor Correction and Soft-Switching Functions

The use of light-emitting diodes (LEDs) in street lighting applications has been greatly welcomed with the current trends of energy saving, environmental protection, carbon reduction, and sustainable development. This paper presents a novel AC-DC LED integrated streetlight driver that combines an interleaved buck converter with a coupled inductor and a half-bridge series resonant converter with a full-bridge rectifier into a single-stage power conversion topology with power factor correction (PFC) and soft switching capabilities. The PFC is achieved by designing the coupling inductor in the interleaved buck converter sub-circuit in discontinuous conduction mode. In addition, the resonant tank in the half-bridge series resonant converter sub-circuit is designed to be similar to an inductive load, thus giving the power switch a zero-voltage switching (ZVS) function, decreasing switching losses and increasing the overall efficiency of the proposed circuit. A prototype circuit of the proposed LED integrated streetlight driver with a power rating of 165 W (235 V/0.7 A) and 110 V input utility voltage has been developed and tested. According to the measurement results, a power factor greater than 0.98, a total harmonic distortion coefficient of the input current less than 3%, and an efficiency greater than 89% were obtained in the AC-DC LED integrated streetlight driver. Therefore, the experimental results are satisfactory and demonstrate the functionality of the proposed AC-DC LED integrated streetlight driver.

Cuk PFC Converter Based on Variable Inductor

When the input inductor operates in discontinuous current mode (DCM), the Cuk converter can automatically achieve power factor correction (PFC) function with only a simple voltage mode control loop. However, the conventional Cuk PFC converter suffers from high intermediate capacitor voltage because of the lack of feedback of the intermediate capacitor voltage and relatively low power factor (PF). In this paper, a Cuk PFC converter using variable inductor which varies with the transient rectified input voltage is proposed to enhance the PF and reduce the intermediate capacitor voltage by injecting a controlled DC bias current into the auxiliary winding of the variable input inductor. The operating principles of the proposed Cuk PFC converter based on variable inductor are analyzed in detail, and the analysis of PF, the voltage of intermediate capacitor, and design considerations are provided. To verify the feasibility of the proposed scheme and compare the characteristics of both the traditional and proposed Cuk PFC converter, a 108W experimental prototype of the proposed converter is built and tested. The experimental results show that the proposed Cuk PFC converter can significantly enhance the PF, decrease the intermediate capacitor voltage, and increase efficiency compared with the traditional Cuk PFC converter.

Power Factor Correction Modulated Wireless Power Transfer System With Series-Series Compensation

Power factor correction (PFC) is usually realized with a boost converter in a traditional power converter. This paper introduces a PFC modulated WPT method which can realize PFC function through phase-shift modulation of the primary-side inverter of a series-series (SS) WPT system. A close-loop control method of the phase-shift modulated system is also proposed for practical implementations. Without using a PFC converter, the structure of a WPT system can be simplified. Theoretical analysis and experimental results are provided to verify the idea.

Wiener Variable Step Size With Variance Smoothening Based Adaptive Neurons Technique for Utility Integrated PV-DSTATCOM System

In this article, the Wiener variable step size with variance smoothening (WVSSV) technique is introduced for the utility supportive solar photovoltaic (PV) system. This system performs the function of power factor correction, compensation of nonactive component, and reduction of total harmonics distortion (THD) from the utility grid. The dc–ac converter is used in between the PV array and the common connection point and it is controlled through the WVSSV technique to produce the switching signals. The WVSSV technique presents impressive robustness and good adaptation in highly adverse nonlinear load conditions by estimating the clean and harmonic less fundamental component. The presented technique has a good convergence rate even at the starting of adapting and the step size is adjusted to eliminate the variety of noise and harmonics of nonlinear loads. The efficacy of the WVSSV control technique is presented through simulated and test results and depicts the improved steady-state as well as dynamic performances of the PV system. The THDs of grid parameters are found under the IEEE-519 standard in different working conditions.

Optimized Multi-Carrier PWM Strategy and Topology Review for Multi-Cell Series-Parallel Medium-Voltage Rectifier

Solid-state transformer (SST) acting as a medium-voltage (MV) rectifier is a viable solution to supply low-voltage DC (LVDC) loads directly from the MV ac grid. Different from a classical boost-derived power-factor-correction (PFC) topology, the multicell series-parallel (MCSP) converter steps down and distributes the input ac voltage by multiple switching cells while providing the PFC function. We propose an optimized multicarrier pulsewidth modulation (PWM) strategy to avoid unwanted modes by modified multicarrier waveforms for ensuring frequent parallel connectivity to improve balancing effect while preserving simple current control implementation. Compared with conventional phase-shifted (PS) PWM and other modified multilevel carrier methods, the proposed method has no adverse effect on the input current distortion and optimizes the balancing effect on the capacitor voltages resulting suppressed circulating currents. Effectively reduced current stresses on the switch devices could lead a reduction of conduction loss on the device. Topology discussion, circulating currents, digital implementation, and loss analysis are provided. Finally, the superiority of the proposed PWM method is validated by thermal-based simulation presenting a power loss breakdown and comparing with other PWM methods. A full-scale prototype is developed, and the experimental outcomes verify the remarkable performance of proposed PWM scheme in balanced and even suppressed switch currents with improved system efficiency.

Research on Bidirectional Isolated Charging System Based on Resonant Converter

This paper proposes a two-stage bidirectional isolated charging system, which can realize the bidirectional flow of electric energy, not only making the electric energy flow from the grid side to the battery side but also converting the battery’s energy into single-phase alternating current to supply other electric equipment. The charging system also has the function of power factor correction and wide-range voltage output. The front stage of the charging system is a bidirectional totem pole structure power factor correction converter with a voltage and current double closed-loop control strategy to ensure the stability of the DC bus voltage, and the rear stage is a bidirectional CLLLC resonant converter, which adopts a high-frequency soft start strategy to reduce the inrush current during start-up and ensure the safe operation of the converter. Moreover, the frequency control strategy is used to make it have a wide range of DC output characteristics. In this paper, the principle analysis and parameter calculation of the charging system is carried out, the simulation platform and hardware circuit design are built, and a test prototype is piloted to verify the bidirectional operating characteristics of the charging system. The simulation and experimental results demonstrate the correctness of the theoretical analysis and topology design.

Automatic power factor correction based on Pearson similarity for distribution networks

In this paper, an online algorithm of automatic power factor correction (APFC) for distribution power grids is presented. The algorithm depends on Pearson similarity of voltage and current signals, which can easily be measured locally using voltage and current transformers, respectively. The proposed method not only evaluates the original power factor (PF), but also functions the APFC more quickly. In this work, the compensation index and reactive power compensation can be identified using new mathematical formulas based on the cross-correlation coefficients calculated between the phase voltage and current signals. Moreover, the coefficients are useful for detecting any abnormal condition. The method performance is examined on a large-scale network with real parameters’ data, which is simulated using the alternative transient program (ATP) environment, and the proposed algorithm is developed in MATLAB package. Numerous simulation results confirm the APFC relay feasibility, and the unity PF can be achieved. Besides, the proposed algorithm is characterized by its high operating speed, safety and accuracy for PF compensation, where its performance accuracy is greater than 99.7%. The approach offers novel operating/tripping curves based on the correlation coefficients for both power factor correction (PFC) and protection functions. Therefore, it is described with high level of functionality integration, and its security and sensitivity are controllable easily using the correlation settings.

Design and Implementation of a Single-Stage PFC Active-Clamp Flyback Converter with Dual Transformers

This paper proposes an AC/DC single-stage structure by integrating a boost topology and an active clamp flyback (ACF) circuit with power-factor-correction (PFC) function. The PFC function can be achieved by controlling a boost PFC topology operated in the discontinuous conduction mode. With the coordination of active clamping components, a resonant technique is obtained and zero-voltage-switching (ZVS) can be achieved. The proposed converter is combined with the advantages of: (1) compared with two-stage circuit, a single stage circuit decreases the component of the main circuit and reduces the complexity of the control circuit; (2) a boost topology with PFC function operated in discontinuous conduction mode can be accomplished without adding any current detecting technique or detecting input signal; (3) by using the inductor from the PFC stage, ZVS function can be achieved without any additional inductor; (4) the increment of switching frequency facilitates the optimization of power density; (5) the conducting loss at the secondary side can be reduced by adding the synchronous rectification; (6) in this proposed scheme, the dual transformers with series-parallel connection are utilized, the current at the secondary side can be shared for lowering the conduction loss of the synchronous transistors. Finally, a prototype converter with AC 110 V input and DC 19 V/6.32 A (120 W) output under 300 kHz switching frequency is implemented. The efficiency of the proposed converter reaches 88.20% and 0.984 power factor in full load condition.

A Novel and Cost-Effective Drive Circuit for Supplying a Piezoelectric Ceramic Actuator with Power-Factor-Correction and Soft-Switching Features

This paper proposes a novel and cost-effective drive circuit for supplying a piezoelectric ceramic actuator, which combines a dual boost AC-DC converter with a coupled inductor and a half-bridge resonant DC-AC inverter into a single-stage architecture with power-factor-correction (PFC) and soft-switching characteristics. The coupled inductor of the dual boost AC-DC converter sub-circuit is designed to work in discontinuous conduction mode (DCM), so the PFC function can be realized in the proposed drive circuit. The resonant tank of the half-bridge resonant inverter sub-circuit is designed as an inductive load, so that the two power switches in the presented drive circuit can achieve zero-voltage switching (ZVS) characteristics. A 50 W-rated prototype drive circuit providing a piezoelectric ceramic actuator has been successfully implemented in this paper. From the experimental results at 110 V input utility-line voltage, the drive circuit has the characteristics of high power factor and low input current total-harmonic-distortion factor, and two power switches have ZVS characteristics. Therefore, satisfactory outcomes from measured results prove the function of the proposed drive circuit.

Research of the Negative Influence of Dimmed LED Luminaires in Context of Smart Installations

This article deals with the investigation of the negative impacts of dimmed public, industrial and office LED (light emitting diode) light installations. This approach is required due to the uncertain design of LED ballasts, while manufacturers do not implement the required PFC (power factor correction) function. Therefore, the focus is on a brief description of the principles of negative influences such as: low power factor, high inrush current and high total harmonic distortion based on direct confrontation with actual standards (IESC EN, NEMA, ENERGY STAR). Further, the behavior of LED drivers is explained under nominal load and dimmed up to critical level. Presented findings confirm issues reported by users from larger installations where LED fittings are dimmed over a certain level. The article includes recommendations for consumers and producers of LED fittings about main issues from the scientific and user points of view. Presented facts conclude on the necessity of studying the marginal operating state of LED fittings aiming at THD (total harmonic distortion), PF (real power factor) and inrush currents.

A Novel Single-Switch Single-Stage LED Driver with Power Factor Correction and Current Balancing Capability

A novel single-switch single-stage high power factor LED driver is proposed by integrating a flyback converter, a buck–boost converter and a current balance circuit. Only an active switch and a corresponding control circuit are used. The LED power can be adjusted by the control scheme of pulse–width modulation (PWM). The flyback converter performs the function of power factor correction (PFC), which is operated at discontinuous-current mode (DCM) to achieve unity power factor and low total current harmonic distortion (THDi). The buck–boost converter regulates the dc-link voltage to obtain smooth dc voltage for the LED. The current–balance circuit applies the principle of ampere-second balance of capacitors to obtain equal current in each LED string. The steady-state analyses for different operation modes is provided, and the mathematical equations for designing component parameters are conducted. Finally, a 90-W prototype circuit with three LED strings was built and tested. Experimental results show that the current in each LED string is indeed consistent. High power factor and low THDi can be achieved. LED power is regulated from 100% to 25% rated power. Satisfactory performance has proved the feasibility of this circuit.

Integrated Charger-Inverter for High-Performance Electric Motorcycles

A high-performance electric motorcycle (HPEM) integrated charger-inverter (ICI) with an induction motor (IM) is proposed in this article. Typical components are shared in drive and charge modes, resulting in savings of weight, volume, and cost. A two-stage ICI for AC induction motor powertrain with power factor correction (PFC) and battery charger functions is considered. Despite high voltage ripple on the DC link, a high bandwidth nonlinear controller can reject such a drawback and adequately provide a constant current or constant voltage charging process. The simulation results of 7 kW ICI are provided to validate the effectiveness and feasibility of the proposed system. Finite element analysis (FEA) determines the torque and losses of IM in charging mode.

A Power Factor Correction Buck Converter-Fed Switched Reluctance Motor with Torque Ripple Suppression

The switched reluctance motor (SRM) suffers the main drawback of torque ripples, and a buck converter-fed SRM motor drive has been proposed to suppress torque ripples and correct a power factor in this paper. The buck converter reduces the torque ripple by supplying appropriate DC-link voltage; meanwhile, the buck converter realizes a function of power factor correction at AC mains. An enhanced performance has been obtained on speed control and power quality improvement. An experimental SRM motor drive is formed, and the experimental results show that the proposed drive possesses an improved function with suppression of torque ripples and power factor correction.

Unbalanced current analysis of three‐phase AC–DC converter with power factor correction function based on integrated transformer

Three-phase AC–DC converter based on integrated transformer is a novel converter which is capable of handling high power levels and can realise power factor correction function. Owing to different parameter tolerances of the primary windings, grid current could be unbalanced, which usually could not be solved through traditional control methods. To handle this problem, a current balancing method is adopted in this study to improve former current control loop. Meanwhile, based on the principle of instantaneous power balance, a dual loop control strategy with an outer voltage loop and an inner current loop is designed. Besides, load current feedforward control is introduced to enhance the dynamic response. Moreover, phase-shift control is employed as the modulation method, in which duty ratios change along with sinusoidal signals. Simulation and experimental results show that the control strategy could make the three-phase current of the converter sinusoidal and balanced.

Design and Implementation of Four-Switch Current Sensorless Control for Three-Phase PFC Converter

Four-switch current sensorless control for three-phase four-switch converter with power factor correction (PFC) function is presented in this letter. In comparison with conventional multiloop control methods, the proposed control strategy requires sensing of two line voltages and two capacitor voltages only to achieve PFC function. As there is no sensing current, the proposed sensorless control scheme reduces the cost and complexity of design. The performance of the proposed control is validated by its implementation in digital signal processing (DSP) TMS320F28335, and the result shows that the proposed scheme is able to provide comparable PFC performance without sensing current.

A Magnetically Controlled Single-Stage AC–DC Converter

In this letter, a magnetically controlled single-stage ac-dc converter is proposed for low-power application which has the following features. First, single-stage operation is achieved by sharing switches between LLC resonant converter and totem-pole bridgeless power factor corrector (PFC) converter. Second, the power factor correction function is inherently achieved by designing the PFC converter to operate in discontinuous conduction mode. Third, the dc-link voltage is almost constant. Fourth, fixed switching frequency and duty cycle can be implemented for the switches, which simplifies the magnetic component and driver circuit design. Fifth, the LLC resonant converter is designed to operate at series resonant frequency, the highest efficiency operating point, so the converter can always achieve the maximum efficiency operation. Meanwhile, at this operating point, the converter output voltage is independent of the load so that it is functioning as a dc transformer; and finally, soft switching for all semiconductors is achieved. A 75-W experimental prototype is built to validate the proposed magnetically controlled single-stage ac-dc converter.