Achieve Power Factor Correction Research Articles

Sliding-mode control for boost converters under voltage and load variations

<p><span lang="EN-US">Boost converters are employed in DC motors, switch-mode power supplies, and other applications. Practical implementation difficulties, reliance on variable-frequency units, and delayed dynamic responses to changes in load and voltage are the main drawbacks of different control methods for the boost converter. In this paper, two techniques were proposed with the target of controlling the boost converter to improve the efficiency of the converter's performance. The two techniques used in this paper depended on fixed-frequency mode instead of variable-frequency mode because of the demerits of the latter factor. The first technique is the sliding-mode control for the AC-DC converter to achieve power factor correction and reduce the harmonic ratio significantly while regulating the output voltage. This technique was used for the DC-DC converter to obtain a rapid dynamic response to control sudden or considerable changes in loads or input voltages with a regulated output voltage. Moreover, the two-loop cascade control is the second proposed technique for the DC-DC converter to achieve an excellent dynamic response under step loads or input voltage variations with an excellently regulated output voltage. Re-simulation results validated the proposed design approach and illustrated the proposed controller's robustness and faster response time.</span></p>

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.

Bridgeless PFC Converter without Electrolytic Capacitor Based on Power Decoupling

Due to fewer conduction devices in operating condition, the bridgeless power factor correction (PFC) converter is more efficient than the traditional PFC circuit. However, to achieve a low output voltage ripple on the DC side, a large electrolytic capacitor must be connected in parallel to the output end. To reduce the value of capacitance, this paper proposes a dual-boost bridgeless PFC converter with a bidirectional buck/boost power decoupling converter in the latter stage. The bidirectional converter absorbs double-line-frequency ripple, lowering the power pulsation at the output end while realizing power decoupling. The one-cycle control is adopted in bridgeless PFC converter, so that the input current can follow the input voltage to achieve power factor correction and decrease harmonic pollution. The power decoupling circuit is designed with a voltage outer loop using PI control and a current inner loop using model predictive current control, which alleviates the output voltage fluctuation caused by the reduction of the capacitance value of the filter capacitor, for the purpose of realizing non-electrolytic capacitor. Finally, the topology and control strategy involved in this paper are simulated and experimented to verify the validity and superiority of the theory.

Variable-Switching-Frequency Single-Stage Bidirectional GaN AC–DC Converter for the Grid-Tied Battery Energy Storage System

This article presents a 10-kW novel gallium-nitride (GaN)-based three-phase grid to 48-V battery energy storage system (BESS). The BESS utilizes a single-stage ac–dc dual-active-bridge (DAB) converter with dual-phase-shift (DPS) and variable-frequency (VF) control. 600- and 80-V GaN power transistors, as well as planar magnetics, are used to achieve 96.6% efficiency and 50-W/in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^3$</tex-math></inline-formula> power density. The operation principle and power transfer characteristics are derived based on time-domain analysis of the DAB inductor current. VF and DPS are utilized to achieve power factor correction and zero-voltage switching simultaneously while minimizing the DAB rms current. An online calculation algorithm is presented with short execution time, which enables the closed-loop control of the BESS. Experimental results are presented to validate the novel control.

Surge voltage reduction method for dual active bridge matrix converter using circulating current

AbstractThis paper proposes an extended method of zero‐voltage switching (ZVS) range for a dual active bridge (DAB) matrix converter with a discontinuous current mode (DCM). In the traditional DAB converter, ZVS cannot be achieved at a light load condition. The duty ratio calculation to achieve power factor correction and ZVS is explained using a circulating current. From the experimental results using a 5‐kW prototype, the ZVS operation with zero transmission power is achieved by increasing the circulating current. In addition, the grid current distortion is lower than 5.0% at the rated power regardless of the DC voltage variation of plus or minus 20%.

A Single-Stage Dual-Active-Bridge AC–DC Converter Employing Mode Transition Based on Real-Time Calculation

In this article, a double degree-of-freedom variable control strategy with fixed frequency is proposed for a single-phase single-stage ac–dc rectifier based on dual active bridges. The proposed modulation strategy can achieve power factor correction without inner current ac current loop. In addition, the two control variables are calculated in real time without using look-up tables, and their combination not only achieves wider zero voltage switching range for switches but also lowers transformer current stress. The mode transition, the soft switching range, and working mode composition are analyzed. Besides, a 1-kW experimental prototype was built to verify the effectiveness of the control strategy.

Modeling and Simulation of Three Phase Power Factor Correctors with Fast Dynamic Response based on Fixed PWM and Bang-Bang control Techniques using DC-DC SEPIC Converter Modules

The main concerns of the power supply industry is to obtain a single stage converter with a low-cost for achieving power factor correction (PFC) complying with required harmonic standards and regulated output voltage simultaneously for three-phase applications. This paper presents the modelling and simulation of single stage three phase power factor correctors using DC-DC SEPIC converter modules based on cascade control strategy. It uses outer loop using proportional-integral (PI) controller to regulate the output voltage and three inner fixed PWM/bang-bang controllers to shape the source current. PI controller parameters are determined by using TYREUS-LUYBEN tuning method. Performance analysis has been made for the two proposed approaches by comparing the simulation results. Results reveal that the proposed scheme provides the power factor close to unity, low % total harmonic distortion (THD), regulated output voltage for load variations and effective set point tracking. Experimental results using fixed PWM technique is also presented.

An Electrolytic Capacitorless Modular Three-Phase AC–DC LED Driver Based on Summing the Light Output of Each Phase

The proposal of this paper is a modular three-phase ac–dc light-emitting diode (LED) driver for high-power luminaires based on LEDs that uses each phase to control an independent LED load removing in the process both the electrolytic capacitor and the second stage to increase both the lifetime and the efficiency. The driving of each LED load is done by means of a dc–dc converter operating as a loss-free resistor responsible for controlling the current across it. Furthermore, each dc–dc converter needs to achieve power factor correction (PFC) to comply with the restrictive IEC 61000-3-2 class C requirements, hence, achieving unity power factor and low total harmonic distortion. Taking advantage of the light properties, the output of the LED driver will be the sum of the light of each of the phases. Therefore, a theoretical study will be carried out to observe the feasibility of removing the electrolytic capacitor while guaranteeing a flicker-free behavior of the LED luminaire, even if the current of each string is pulsating at twice the mains frequency. This particular performance under high output current and voltage ripples requires reevaluating the well-known limits between the conduction modes in PFC converters. In addition, the theoretical analysis also discusses and proposes control methods for the LED driver, which thanks to its modularity can easily scale in power to drive high-power luminaires. In order to validate the theoretical analysis, a prototype has been built comprised three PFC boost converters disposing of their electrolytic capacitors. The designed prototype operates in the full range of the European three-phase line voltage, which varies between 380 and 420 V, and supplies an output light of 42.000 lm at a maximum power of 300 W while achieving an electrical efficiency of 97.5%.

Enhanced performance of substation dynamics during large induction motor starting using SVC

Static Var Compensators (SVC) have been widely used to separately improve each of voltage variation performance and steady state power factor of industrial substations. However, these two functions are interdependent, power factor improvement tends to do better voltage regulation. In this paper, a newly starting method with SVC for large induction motors is suggested. This method provides a controllable amount of reactive power precisely according to the requirement of the load. A combined controller consists of slow susceptance control besides fast acting voltage control will give SVC the ability to achieve power factor correction, and will present a constant voltage characteristic during large induction motor starting. An ideal compensator approach is proposed for both power factor correction and optimum voltage regulation. A case study of 1.4 MW large induction motor starting is presented with different starting methods. A comparative study is conducted to simulation results using Electrical Transient Analyzer Program (ETAP) for different starting cases. Finally, the simulation results provide bases for the safe and reliable operation and would insure a robust design of practical substation.

Power Factor Corrector with Bridgeless Flyback Converter for DC Loads Applications

Since power systems with a DC distribution method has many advantages, such as conversion efficiency increase of about 5–10%, cost reducing by about 15–20% and so on, the AC distribution power system will be replaced by a DC distribution one. This paper presents a DC load power system for a DC distribution application. The proposed power system includes two converters: DC/DC converter with battery source and power factor corrector (PFC) with a line source to increase the reliability of the power system when renewable energy or energy storage equipment are adopted. The proposed PFC adopts a bridgeless flyback converter to achieve power factor correction for supplying power to DC loads. When the bridgeless flyback converter is used to achieve PFC, it needs two transformers to process positive and negative half periods, respectively. In order to increase conversion efficiency, the flyback one can add two sets of the active clamp circuit to recover energies stored in leakage inductances of transformers in the converter. Therefore, the proposed bridgeless flyback converter can not only integrate two transformers into a single transformer, but also share a clamp capacitor to achieve energy recovery of leakage inductances and to operate switches with zero-voltage switching (ZVS) at the turn-on transition. With this approach, the proposed converter can increase conversion efficiency and decrease component counts, where it results in a higher conversion efficiency, lower cost, easier design and so on. Finally, a prototype with a universal input voltage source (AC 90–265 V) under output voltage of 48 V and maximum output power of 300 W has been implemented to verify the feasibility of the proposed bridgeless flyback converter. Furthermore, the proposed power system can be operated at different cases among load power PL, output power PDC1 of DC/DC converter and output power PDC2 of the proposed PFC for supplying power to DC loads.

Review of GaN Totem-Pole Bridgeless PFC

Switching-mode AC/DC converters are widely used in modern power supplies for computers, data centers and telecommunication equipment. Achieving Power Factor Correction (PFC) and high efficiency are the two most important requirements. In many cases, high power density is also of tremendous interest. Both power efficiency and power density are greatly influenced by the power devices, the topology and the control used. Compared with conventional Si power MOSFET and Si super-junction MOSFET, the newly introduced 600 V GaN devices not only eliminate the reverser recovery, but also have much lower switching and driving losses. These excellent properties enable the emergence of the totem-pole bridgeless AC/DC converter as the next generation preferred solution for PFC instead of the state-of-the art Si-based boost PFC. In this paper, the key technologies and designs for both hard-switching and soft-switching GaN totem-pole PFC are reviewed and the key performance metrics are compared. A soft switching, 3.2 kW totem-pole PFC prototype with 99% efficiency and 130 W/inch3 power density has been achieved in the author's group as a proof of the concept. Based on the power density comparison, the high frequency soft-switching GaN totem-pole PFC is the preferred choice to achieve both high efficiency and high power density at the same time.

반도체 변압기용 단상 계통 연계형 인버터의 소신호 모델링과 제어기 설계

In this paper, a small signal model for grid-connected inverter with unipolar pulse width modulation method is presented. Small-signal analysis allows to predict the stability and dynamics of the inverter. To regulate output voltage and to achieve power factor correction, inverter has two control loops. Loop gains are useful to identify the stability for multi-loop controlled system. Based on small-signal model, controllers are designed to improve audio susceptibility and output impedance characteristics. Proposed small-signal model and controllers are verified by PSIM simulation and experiments.

Design of Single-Stage Flyback PFC Converter for LED Driver

A light emitting diode (LED) driver based on single-stage power factor correction (PFC) is presented in this paper. The designed LED driver using flyback topology can achieve power factor correction and constant-current drive LED in boundary conduction mode. The circuit principle is described in detail, the formulas for MOS switch-on time, switching frequency and the main impact factor of power factor are proposed. The experiment results show that the designed LED driver has high power factor, stable output and it can drive the LED with high efficiency.

Interleaved Two Channel Boost Converter for Power Factor Correction using Boundary Conduction Mode

This paper presents the concept of interleaved pulse width modulation to achieve boost converter with power factor correction and regulated DC voltage. The boost converter employs boundary conduction mode and zero current switching to achieve power factor correction. The converter is having a high voltage conversion ratio with wide span of turn ON and OFF period, which will differentiate this proposed converter from the conventional boost converter. The interleaved pulse width modulation will reduce current ripples of input and output currents. The interleaving will also aid to the reduction in size of the inductor and capacitor used for the proposed converter. In this paper the circuit configuration, principle of operation, simulation results, experimental results of the proposed converter are presented.

High power factor LED power supply based on SEPIC converter

A single-ended primary inductor converter (SEPIC)-based light-emitting diode (LED) power supply, which can achieve power factor correction (PFC) and constant-current drive for LED in the critical conduction mode (CRM), is presented. The circuit principle is described in detail. Meanwhile the formulas for metal–oxide semiconductor field-effect transistor switch-on time, switching frequency and the main influences of power factor are given. Experimental results show that the power can drive the LED with high efficiency by virtue of its high power factor, low power loss and stable output. Furthermore, it can be applied to low-power lighting occasions with simple structure and high reliability.

A Low-Distortion Self-Oscillating Power Factor Correction Circuit for Low-Cost Applications

Self-oscillating converters operating in the critical conduction mode are popular in low power applications because of their simplicity and low cost. However, these converters are not suited for Power Factor Correction (PFC) because the peak switch current is controlled to regulate the output voltage and does not follow the shape of the line voltage waveform. A new control circuit implementation is proposed for a self-oscillating boost converter to achieve power factor correction. A full featured design example is provided which can be simplified for use in various cost sensitive applications such as electronic lighting, etc. This wide input voltage range self-oscillating PFC prototype achieves less than 10 percent line current distortion in the defined load range (10 W to 40 W).

An AC/DC PFC Converter with Active Soft Switching Technique

This paper proposes an AC-DC converter with the application of active type soft switching techniques. Boost converter with active snubber is used to achieve power factor correction. Boost converter main switch uses Zero Voltage Transition switching for turn on and Zero Current Transition switching for turn off. The active snubber auxillary switch uses Zero Current Switching for both turn on and turn off. Since all the switches of the proposed circuit are soft switched, overall component stress has been greatly reduced and the output DC voltage is expected to have low ripples. A small amount of auxillary switch current is made to flow to the output side by the help of coupling inductor. The proposed circuit is simulated using MATLAB Simulink. All the related waveforms are shown for the reference. The power factor is measured as 0.99 showing that the input current and input voltage is in phase with each other. The PFC circuit has very less number of components with smaller size and can be controlled easily at a wide line and load range.

A New Interleaved Three-Phase Single-Stage PFC AC–DC Converter

A new interleaved single-stage ac-dc converter is proposed in this paper to reduce line current harmonics while achieving power factor correction (PFC). The proposed rectifier can produce input currents that do not have deadband regions with high PFC, operate with a continuous output current, and minimize the input electromagnetic interference filter size. In this paper, the operation of the new converter is explained, its features and design are discussed in results, and its operation is confirmed with experimental results obtained from a prototype.

Comparison among Chargers of Electric Vehicle Based on Different Control Strategies

The charger of electric vehicle is a power electronic device which consists of rectifying devices and DC-DC converters. This nonlinear diode rectifier circuit has low power factor and high harmonic content. In order to improve power factor and reduce the harmonic distortion rate of the AC side current, single-phase non-controlled rectifier charger needs to install the active power factor correction device. A piece of power system analysis software which is called PSCAD is used in modeling of an EV charger which contains Boost-APFC. By means of simulation and analysis, differences of APFC characteristics between the hysteresis current control mode and average current control mode which has an influence on the power grid are compared. The consequence of simulation shows that the two control strategies achieve power factor correction and harmonic reduction requirements; Boost type power conversion circuit employs the average current control mode is better, which has following features: relatively faster settling time of the output voltage, relatively smaller overshoot, lower current harmonic distortion rate on AC side, lower switching frequency and better control effect.

Interleaved Boost-Flyback Converter with Boundary Conduction Mode for Power Factor Correction

This paper presents a new interleaved pulse-width modulation (PWM) boost-flyback converter to achieve power factor correction (PFC) and regulate DC bus voltage. The adopted boost-flyback converter has a high voltage conversion ratio to overcome the limit of conventional boost or buck-boost converter with narrow turn-off period. The proposed converter has wide turn-off period compared with a conventional boost converter. Thus, the higher output voltage can be achieved in the proposed converter. The interleaved PWM can further reduce the input and output ripple currents such that the sizes of inductor and capacitor are reduced. Since boundary conduction mode (BCM) is adopted to achieve power factor correction, power switches are turned on at zero current switching (ZCS) and switching losses are reduced. The circuit configuration, principle operation, system analysis, and design consideration of the proposed converter are presented in detail. Finally, experiments conducted on a laboratory prototype rated at 500W were presented to verify the effectiveness of the converter.