Unity Power Factor Correction Research Articles

Near Unity Power Factor Correction Vienna Rectifier for Plug-In Type Three Phase EV Charging Station

Near Unity Power Factor Correction Vienna Rectifier for Plug-In Type Three Phase EV Charging Station

O Splines-Based Fixed-Frequency Integral Sliding-Mode Controller for PFC Rectifier

This paper proposes a fast-response sliding mode controller (SMC) for a semi-bridgeless boost converter under large and quick load fluctuations to ensure tight output voltage regulation and unity power factor correction (PFC) at the line side. In this sense, a novel approach for estimating the reference current profile is presented focusing on the real-time phasor estimation via the O-splines of the discrete-time Taylor-Fourier transform (DTTFT). This method allows for improving the computational efficiency and dynamic performance of the estimations of amplitude, frequency and phase of the network voltage used for the generation of the reference current profile. Several aspects of the controller design are discussed, including the choice of the sliding surface, the existence and stability conditions, and the implementation of an adaptive hysteresis band to fix the switching frequency and reduce zero-crossing distortion. Experimental results of a GaN-based prototype validate the theoretical predictions, exhibiting a PF close to 1 and a total harmonic distortion lower than 3.2% in presence of load changes of up to 50% and changes in the output voltage set point. Several comprehensive experimental comparisons between the proposed framework and the most widely used methods recently reported in the literature are accomplished in terms of transitory and steady-state responses. The robustness of the proposed control approach is experimentally demonstrated under sag conditions and a wide operating range of the input voltage.

Cascaded AC-DC Power Conversion Interface for Charging Battery

This paper develops a cascaded AC-DC power conversion interface (CADPCI) to convert AC power to charge the battery set. The proposed CADPCI is composed of a cascaded converter (CC) and a dual-input buck converter (DIBC). The CC is formed by connecting a full-bridge converter (FBC) and a bridgeless rectifier (BLR) in series. The CADPCI generates an 11-level input voltage and performs unity power factor correction. The switching loss is reduced because only the FBC with a lower DC port voltage is switched at a high frequency. The DIBC uses a buck converter and a selection switch set to generate a two-level DC voltage on the DC port of the BLR. By controlling the DC input voltage of the buck converter, the injected power of the BLR can match the input power of the utility. Therefore, the FBC does not require to handle the real power, saving an isolated converter for regulating the DC port voltage of the FBC, thus simplifying the power circuit of the CC. The buck converter also acts as a DC active filter to filter out low-frequency ripples of the charging current. A prototype is constructed to verify the performance of the proposed CADPCI.

Phase Voltage-Oriented Control of a PMSG Wind Generator for Unity Power Factor Correction

This paper presents the power factor control of a permanent magnet synchronous wind generator (PMSG) wind turbine using a phase voltage-oriented control (PVOC) scheme, which is different from the conventional rotor flux-oriented control (RFOC) method and without using a rotor position sensor or sensorless estimator. The proposed control system is operated in two separately synchronously rotating d-q frames. One is for a phase-locked loop (PLL) and the other is for the PVOC current control loop. A PI controller functioned as a low-pass filter in the PLL loop is designed for extracting the phase voltage angle for the coordinate transformation between the stationary α-β frame and the synchronously rotating d-q frame in the PVOC control loop. The d-q modeling of the PMSG with the three-phase voltage vector aligned on the d-axis is then derived and based on which an another PI controller followed by decoupling control is designed, so that the three-phase currents are in phase with the three-phase output voltages of the wind generator for unity power factor correction. The simulation results in PSIM show the performance of the proposed control system which is also experimentally verified by using a TI TMS320F28335 digital control chip.

Performance Analysis of Unipolar SPWM Inverter: Resistive load and Inductive load

This paper presents the performance analysis of the Unipolar SPWM Inverter for the resistive and inductive load testing. The common criteria reported in various technical papers where the resistive load will produce a unity power factor correction and lagging power factor behaviour for inductive load. This paper is to demonstrate the performance of both loads that are tested to the single phase Unipolar SPWM inverter under the modulation ratio of 0.8. The performances will be covered in term of the waveform behavior and THDv performance. The project are carried out through the simulation using PSIM software and real implementation to the real hardware. The selection of filter for this paper is the low pass passive LC filter.

Direct Load Voltage Control for Electrolytic Capacitorless Wireless Power Transfer System Without DC/DC Converter

This article presents a new direct load voltage control method for electrolytic capacitorless wireless power transfer (WPT) system without dc/dc converter. In specific, the three-phase low-frequency ac to the high-frequency ac (HFac) converter is employed into the electrolytic capacitorless WPT system by using the bidirectional power switches. The HFac voltage is directly generated on the transmitting tank without using the electrolytic capacitor. Furthermore, in order to realize the discretionary and accurate load voltage control without dc/dc converter, the nine voltage vectors, including six effective voltage vectors and three zero voltage vectors, are selectively exported for the transmitting tank with different duty cycles. In addition, the unity power factor correction and direct load voltage control are both achieved only by transmitting side control. Meanwhile, theoretical analysis of double series-compensated transmitting network and duty cycles under resonant frequency calculation in microchip are demonstrated in detail. Finally, both simulation and experimental results are provided to verify the feasibility and correctness of the proposed system, which operates at 85 kHz with 90% efficiency and about 9% total harmonic distortion.

Development of an SDBC-MMCC-Based DSTATCOM for Real-Time Single-Phase Load Compensation in Three-Phase Power Distribution Systems

This paper proposes a newly developed single-delta bridge-cell, modular multilevel cascade converter (SDBC-MMCC)-based distribution-level static synchronous compensator (DSTATCOM) for single-phase load compensation in three-phase, three-wire electric power distribution systems. Each main circuit arm of the DSTATCOM uses a modular multilevel cascade converter based on full-H-bridge (FHB) cells. The three main DSTATCOM arms are delta-connected to allow phase-independent operations for phase balancing and unity power factor correction of the single-phase load in three-phase, three-wire electric power distribution systems. By using the symmetrical components method, a feedforward compensation algorithm was employed for the DSTATCOM. A simulation of the DSTATCOM was performed for functioning verification. Finally, a hardware test system was built by using a multi-DSP-based control system. The test results verified the effectiveness of the proposed SDBC-MMCC-based DSTATCOM in single-phase load compensation.

A novel bidirectional converter control for plug-in electric vehicles

In this paper, a novel bidirectional converter modelling and control is presented for the applications in plug-in electric vehicles. The controller is developed to enforce a pseudo-resistive behaviour at input terminals of the converter to ensure the unity power factor correction in power conversion. The proposed controller is based on a nonlinear sliding mode approach utilising a modified sliding manifold based on PI structure, as well as boundary layer solution to perform chattering compensation. The input resistance of the converter is regulated and controlled to positive and negative values depending on the charging or discharging state of the electric vehicle. Numerical simulations in PSIM environment are presented that evaluate performance of the proposed modelling and feedback control scheme.

A Programmable Controller IC for DC/DC Converter and Power Factor Correction Applications

This paper presents the design of a low-cost programmable controller integrated circuit (IC) for general power electronics applications. The architecture of the programmable controller IC consists of 10-bit ADC and DAC, programmable counter array (PCA), which is configured to function as PWM, and a control unit (processor) for regulation. The processor unit is configured as digital compensator, through fewer program steps to perform accurate compensation on the voltage control loop of the converter system. Limit-cycle oscillation is minimized through inclusion of a sufficiently low integral gain term in the control law. A hybrid control method is first used to control the input voltage and current waveforms to achieve a unity power factor correction. It is observed that the programmable converter achieves the high efficiency power conversion. The conversion efficiency of the digital controlled boost converter is 91% with a 0.8% ripple voltage performance. While in power factor correction (PFC) circuit application, the power factor and output ripple voltage of converter are 0.995 and 0.93%, respectively. The chip is implemented with TSMC 0.25 um CMOS process.

The analysis of average sliding control method applied on Sheppard–Taylor power factor correction converter

This paper presents an average sliding control (ASC) method to be used in power factor correction (PFC) converters to decrease the total harmonic distortion (THD) of the input current by eliminating the input current harmonics. The ASC algorithm is adapted to digital signal processor due to its well-known properties such as robustness, stability and good regulation in a wide range of operating conditions. The control approach is operated in continuous conduction mode. In this approach, all the duty cycles required to achieve unity power factor in a half line period are calculated in advance using ASC method. The feed forward is also used in the control algorithm using rms value of the input voltage. The implementation of feed forward improves the converter performance to obtain a near unity power factor correction with a lower input current THD. The converter used in simulation and experimental studies is a Sheppard–Taylor PFC converter. The stability analysis of proposed control method is performed with the effect of changes in input voltage and load. In addition, the performance of ASC method is compared with UC3854AN traditional analog PFC control method. The experiments performed in the laboratory for different cases of operation verify the theoretical and simulation studies performed in MATLAB/Simulink. The experimental results are satisfied by IEC 61000-3-2 Current Harmonic Standard.

A DSP based power factor correction converter to reduce total harmonic distortion of input current for improvement of power quality

This paper proposes a controlled approach to be used in power factor correction (PFC) circuits to decrease total harmonic distortion (THD) of input current by eliminating the input current harmonics. This method removes the problems of the conventional PFC converters. Since in conventional PFC circuits the input current is controlled to follow the ac input voltage, it will have the same harmonics of the input voltage. This is an important disadvantage of the conventional method especially when the input voltage is distorted. In this approach, a sinusoidal signal is generated by the DSP microprocessor and is used as reference in controlling the converter switch to obtain a sinusoidal input current based on zero crossing points of distorted input voltage. Due to the reflection of input voltage distortions to the output voltage, an adaptive digital FIR filter is designed and embedded into the voltage control loop. The feed forward is also used into the control algorithm. The implementation of feed forward and adaptive digital FIR filter improves the converter performance to obtain a near unity power factor correction with lower input current THD. Average current control mode is implemented and operated in continuous conduction mode. The experiments performed in the laboratory for different cases of operation verify the theoretical and simulation studies performed in MATLAB/Simulink. The control approach is programmed by the TMS320F2812 DSP microprocessor. The experimental results are good in accordance with IEC 61000-3-2 Current Harmonic Standard.

Voltage Doubler를 이용한 4-스위치 3상 BLDC 전동기 구동 알고리즘

Over the years, traditionally, six-switch three-phase inverters have been widely utilized for variable speed alternating current motor drives. Recently, some efforts have been made on the application of four-switch three phase inverter for uninterruptible power supply and variable speed drives. This is due to some advantages of the four-switch three phase inverter over the conventional six-switch three-phase inverters such as reduced price due to reduction in number of switches, reduced switching losses, reduced number of interface circuits to supply logic signals for the switches, simpler control algorithms to generate logic signals, less chances of destroying the switches due to lesser interaction among switches, and less real-time computational burden. However such as slow di/dt and speed limitation, are the inherent characteristics and main drawbacks of the four-switch configuration. Those problems can be overcome in conjugation with Voltage-doublers which has additional advantage, such as unity power factor correction.

Fuzzy controller tuning of a boost rectifier unity power factor correction by experimental designs

This paper shows the validity of experimental designs as an efficient on-site tuning tool for fuzzy controllers, dedicated to electrical engineering applications with multi-objective criteria. Our purpose is to improve the input and output system characteristics that is to say the global quality of the electrical power in a boost rectifier with unity power factor correction. The desirability notion here combines the time dynamic and harmonic criteria and illustrates the trade-off that has to be satisfied between different properties.

A Unity Power Factor Correction Preregulator With Fast Dynamic Response Based on a Low-Cost Microcontroller

Low cost passive power factor correction (PFC) and single-stage PFC converters cannot draw a sinusoidal input current and are only suitable solutions to supply low power levels. PFC preregulators based on the use of a multiplier solve such drawbacks, but a second stage dc-dc converter is needed to obtain fast output voltage dynamics. The output voltage response of PFC preregulators can be improved by increasing the corner frequency of the output voltage feedback loop. The main drawback to obtaining a faster converter output response is the distortion of the input current. This paper describes a simple control strategy to obtain a sinusoidal input current. Based on the static analysis of output voltage ripple, a modified sinusoidal reference is created using a low cost microcontroller in order to obtain an input sinusoidal current. This reference replaces the traditional rectified sinusoidal input voltage reference in PFC preregulators with multiplier control. Using this circuitry, PFC preregulator topologies with galvanic isolation are suitable solutions to design a power supply with fast output voltage response (10 or 8.33 ms) and low line current distortion. Finally, theoretical and simulated results are validated using a 500 W prototype.

FUZZY CONTROLLER TUNING FOR UPFC BOOST RECTIFIER BY EXPERIMENTAL DESIGNS

This paper shows the validity of experimental designs as an efficient on-site tuning tool for fuzzy controller dedicated to electrical engineering applications with multi-objective criteria. Our purpose is to improve the input and output system characteristics as well as the quality of electrical power. The desirability notion combines here time dynamic and harmonic criteria for a boost rectifier with unity power factor correction and illustrates the trade-off that has to be made between the different properties.

Improved DSP-controlled online UPS system with high real output power

A circuit topology is proposed for single-phase online UPS systems. The proposed circuit incorporates a built-in bidirectional AC/DC converter, which provides power factor correction and active power filtering. The input stage, based on a bidirectional AC/DC converter, functions as a rectifier with unity power factor correction for normal AC line mode operation, and as an active power filter for outage mode operation. During input power failure, the bidirectional AC/DC converter functions as an active power filter, providing reactive power to the load. Simultaneously, the DC/AC voltage inverter output stage supplies real power from the battery bank to the critical load. The real power capability is improved compared with that of a conventional online UPS system, and extra loads can be connected to the UPS system during outage. The power circuit of the proposed UPS system is presented and analysed. Circuit models are derived and a UPS digital control system using a digital signal processor (DSP) is developed. Finally, simulated and experimental results obtained from a laboratory prototype are presented to confirm the feasibility and features of the proposed UPS scheme.

Single-phase power-factor-correction AC/DC converters with three PWM control schemes

Three pulse-width modulation (PWM) control schemes for a single-phase power-factor-correction (PFC) AC/DC converter are presented to improve the power quality. A diode bridge with two power switches is employed as a PFC circuit to achieve a high power factor and low line current harmonic distortion. The control schemes are based on look-up tables with hysteresis current controller (HCC) to generate two-level or three-level PWM on the DC side of diode rectifier. Based on the proposed three control schemes, the line current is driven to follow the sinusoidal current command which is in phase with the supply voltage, and two capacitor voltages on the DC bus are controlled to be balanced. The simulation and experimental results of a 1 kW converter with load as well as line voltage variation and shown to verify the proposed control schemes. It is shown that unity PFC is achieved using a simple control circuit and the measured line current harmonics satisfy the IEC 1000-3-2 requirements.

Three-phase current-fed soft-switching PWM converter with auxiliary commutation inductors and resonant snubber

A new three-phase current-fed soft-switching PWM converter is presented. This converter utilises two types of switching commutation scheme to improve the PWM current utilisation rate. It is shown by means of computer simulation that this converter has low THD and offers unity power factor correction.

Current-fed three-phase and voltage-fed three-phase active converters with optimum PWM pattern scheme and their performance evaluations

This paper describes a new approach to select the optimum sinewave pulsewidth modulation (PWM) patterns suitable for a large-capacity current-fed active PWM power converter and a practical design procedure to determine circuit constants of a low-pass filter connected to suppress higher line current harmonics flowing into the utility-grid AC power source. A feasible test is implemented by building a prototype 500 kW three-phase current-fed PWM power converter which is designed and controlled on the basis of the proposed considerations. It is verified from a practical point of view that these new conceptual considerations are more effective and acceptable to minimize higher harmonic current components flowing into the utility-grid AC power source. This experimental setup provides highly efficient steady-state characteristics of the current-fed three-phase PWM power converter under the operating condition of a unity power factor correction and sinewave line current shaping schemes. Furthermore, this unique optimum PWM pattern derived from the theoretical method proposed here is conveniently applicable to a voltage-fed three-phase PWM converter. It is verified that this optimum PWM pattern provides excellent switching performance with a lower switching frequency mode than the conventional carrier-based PWM scheme.

Feasible single-phase UPS incorporating switched-mode PFC rectifier with high-frequency transformer link

The general purpose high performance single phase UPS topologies are indispensable for the considerable reduction of harmonic current components in a.c. mains as well as the realization of unity power factor correction (PFC). In particular, the single phase PFC rectifier with a high-frequency isolation transformer link has some feasible advantages as an electrically isolated a.c./d.c. conversion circuit for small scale UPS. This UPS is capable of eliminating harmonic currents and realizing an isolation between a.c. input and d.c. output power stage as well as matching the d.c. side input voltage of the PWM inverter by means of incorporating a compact high-frequency transformer into high-frequency intermediate stage. Electrically isolated PFC rectifiers designed for 2 kVA, 3 kVA and 5 kVA UPSs are put into practical use as new topological versions. This paper presents a circuit configuration of high-frequency link PFC rectifier for small scale UPS, its operating principle and related control strategy. The steady state and dynamic state performances of three power classes of UPSs which incorporate this type of PFC converter are evaluated from a practical point of view.