Near-unity Power Factor Research Articles

A dSPACE-based implementation of ANFIS and predictive current control for a single phase boost power factor corrector

This paper presents an innovative control scheme designed to significantly enhance the power factor of AC/DC boost rectifiers by integrating an adaptive neuro-fuzzy inference system (ANFIS) with predictive current control. The innovative control strategy addresses key challenges in power quality and energy efficiency, demonstrating exceptional performance under diverse operating conditions. Through rigorous simulation, the proposed system achieves precise input current shaping, resulting in a remarkably low total harmonic distortion (THD) of 3.5%, which is well below the IEEE-519 standard threshold of 5%. Moreover, the power factor reaches an outstanding 0.990, indicating highly efficient energy utilization and near-unity power factor operation. To validate the theoretical findings, a 500 W laboratory prototype was implemented using the dSPACE ds1104 digital controller. Steady-state analysis reveals sinusoidal input currents with minimal THD and a power factor approaching unity, thereby enhancing grid stability and energy efficiency. Transient response tests further demonstrate the system’s robustness against load and voltage fluctuations, maintaining output voltage stability within an 18 V overshoot and a 20 V undershoot during load changes, and achieving rapid response times as low as 0.2 s. Comparative evaluations against conventional methods underscore the superiority of the proposed control strategy in terms of both performance and implementation simplicity. By harnessing the strengths of ANFIS-based voltage regulation and predictive current control, this scheme offers a robust solution to power quality issues in AC/DC boost rectifiers, promising substantial energy savings and improved grid stability. The results affirm the potential of the proposed system to set new benchmarks in power factor correction technology.

POWER FACTOR IMPROVEMENT BY USING STATIC VARIABLE COMPENSATOR

This project aims to improve the power factor of transmission lines using a static variable compensator. Traditional methods using large rotating parts were inefficient and prone to damage. Static VAR Compensation under FACTS employs Thyristor Switched Capacitors (TSC) controlled by a programmed microcontroller. This system compensates the power factor using thyristor-switched capacitors, where the zero voltage and zero current pulses are fed to a microcontroller. Previously, power factor compensation relied on large machines like synchronous condensers or switched capacitor banks. Shunt capacitive compensation, where a shunt capacitor is connected to draw current leading the source voltage, improves the power factor for inductive loads. The program controls opto-isolators interfaced with SCRs to achieve near-unity power factor. The project can be further enhanced with thyristor-controlled triggering for precise power factor correction.

Coreless DC Transformer With Near-Unity Power Factor by a Reactive Power Injector

Coreless DC Transformer With Near-Unity Power Factor by a Reactive Power Injector

Unity Power Factor Operation in Microgrid Applications Using Fuzzy Type 2 Nested Controllers

The issue of low-power factor operation microgrids was reported for several layouts. Although numerous power factor improvement strategies have been applied and tested, various concerns remain to be addressed such as transient performance, simplicity of implementation, and satisfying the power-quality standards. The presented research aimed to design and implement controllers that can improve the transient response of microgrids due to changes in the load demand and achieve a near-unity power factor at the AC grid side, to which the DC microgrid is connected. Due to the nonlinear nature of microgrids, as they rely on power electronics converters, a Fuzzy type 2 controller was designed, implemented, and tested. The focus was given to improving the power factor of the DC microgrids. The validation of the proposed technique was verified by comparing its performance with Fuzzy type 1 and autotuned conventional PI controllers. To achieve the set aims, two nested control loops were designed with an inner current loop and an outer voltage loop. Besides MATLAB/Simulink simulations, a 10 kHz-sampling dSPACE platform was used to implement the suggested system. Two operational scenarios were tested: (1) a step change in the DC link voltage and (2) a change in the AC load (increase and decrease) at the output of the power inverter, connected to the DC grid. The simulation and experimental results confirmed that the proposed Fuzzy type 2 controller performed better than the other two techniques regarding the dynamic response, steady-state error, and compliance with power quality standards. Conventional approaches develop controllers using a linearized model, which limits the model accuracy and ignores higher-order variability. The method employs the nonlinear model. Fuzzy type 2 can better approximate high-precision problems than Fuzzy type 1.

A single-phase level-shifted duty controlled multilevel rectifier-based EV charger for wide output voltage range

Nowadays, electric vehicles (EVs) are gaining popularity with customers and as an environmentally-friendly option owing to the rise in petroleum prices and pollution, respectively. The battery is the prime source of power for EVs. This paper presents, a level-shifted duty controlled multilevel power factor correction (PFC) AC-DC converter, followed by a phase-shifted full-bridge converter (PSFBC) as an efficient charging solution for EVs. The adopted topology uses fewer semiconductor switching devices than traditional multilevel converters, which minimises switching losses, making it a good choice for a compact EV charger. Complete system design is carried out for a single-phase, 3.3 kW, EV charger, with 220 vrms AC input and 48-72 V DC output voltage for batteries. This EV charger has improved the system reliability and efficiency, along with the near-unity power factor (UPF) in compliance with the international IEC-61000-3-2 PQ standard. MATLAB/Simulink and experimental results are presented to validate the aforementioned functionalities of this EV charger.

Performance Analysis of Isolated Bridgeless SEPIC Converter for EV Battery Charging

The conventional Electric Vehicle(EV) battery charging systems with power factor correction circuits have limitations due to conduction losses present in the input side bridge rectifiers. This paper presents a Bridgeless Isolated Single-Ended Primary Inductance Converter (SEPIC) with improved power factor and reduced THD to increase performance. Throughout the charging time of the Electrical Vehicle, the input side maintains a near-unity power factor. Because the DBR is eliminated, the current is conducted through a smaller number of devices, resulting in considerable reductions in conduction losses. This optimizes the charging system's efficiency in alternative to the existing BL SEPIC converter. A constant current/constant voltage controlling mode is used to charge the EV battery, which delivers good results in terms of intrinsic PFC and decreased THD, hence increasing the charging performance of this system.

Voltage-Sourced Converter Fed High-Speed Switched Reluctance Motor Drive System With Energy Feedback and Near-Unity Power Factor

The diode bridge rectifier fed asymmetric half-bridge converter (AHBC) is conventionally employed to drive switched reluctance motors (SRMs), which leads to poor grid-side power quality. In the proposed system, a topology made up of a voltage-sourced converter and an AHBC is employed to drive the high-speed SRM. Stable SRM operation can be obtained by manipulating the active power flowing to motor side, and on the basis of that, the grid-side power quality is enhanced by directly manipulating input reactive power. Predictive deadbeat control with disturbance observer is employed to follow the power references, thereby achieving controllable speed, energy feedback, near-unity grid-side power factor, and low grid-side current distortion simultaneously. Additionally, an improved asymmetric modulation method is developed for switching frequency reduction. Experiments are carried out to test the proposed drive system in steady and dynamic conditions. Performance comparisons validate the improvement of the proposed high-speed SRM drive system.

Analysis of a new SEPIC AC–DC PFC converter for light emitting diode applications

Active power factor correction (PFC) converters are used to increase the power factor and improve the total harmonic distortion as a result of reducing the harmonics in the current. In this paper, a new bridgeless single-ended primary inductor converter (SEPIC) topology used in light emitting diode (LED) load is proposed to obtain near-unity power factor. By eliminating the input bridge in the bridge PFC converter, the total harmonics distortion is improved and a lower cost is obtained. The reactive power control is used to generate the reference current signal in the proposed converter to control the LED current. To demonstrate the applicability of the proposed topology and to compare its performance with the bridge SEPIC topology, PSIM circuit simulation was used, and an experimental prototype was performed. In the experimental study, 25 Vrms input voltage was applied, and 10 V DC voltage was obtained at the output. Using the proposed converter, the total harmonic distortion value was reduced from 5.722% to 1.837%, and the power factor was increased to 0.999. The experimental and simulation results showed that the total harmonic distortion value of the input current improved and that the proposed SEPIC PFC converter for low-power circuits, particularly in LED applications, is a very good option.

Design and Implementation of Input AC Filters and Predictive Control for Matrix-Converter Based PMSM Drive Systems

Matrix converters have many advantages, including high-efficiency, single-stage AC/AC energy conversion, bidirectional power flow, a near-unity input power factor, sinusoidal three-phase input currents, and sinusoidal three-phase output currents. However, matrix converters have 360 Hz voltage pulsations at the virtual DC-bus, which produce input harmonic currents and output harmonic currents, which cause unsatisfactory responses. To solve the problem of the input harmonic currents, a systematic design of an input three-phase current modulation method and an input three-phase AC filter that uses two different design methods are proposed. In addition, to improve dynamic responses, two predictive speed controllers are investigated and compared, and a predictive current controller is studied to reduce the output harmonic currents. A digital signal processor and an FPGA are used to execute the control algorithms. Several experimental results validate the theoretical analysis and show that the proposed methods effectively improve the power quality of the PMSM drive system and its input power-source quality.

An LCLC-LC-Compensated Capacitive Power Transferred Battery Charger With Near-Unity Power Factor and Configurable Charging Profile

Capacitive power transfer (CPT) techniques are attracting widespread attention due to some unique advantages compared to conventional plug-in systems and inductive power transfer techniques. Since Lithium-ion batteries have been widely used in many energy storage applications, a well-compensated CPT charger should provide an efficient charging profile consisting of first constant current (CC) and later constant voltage (CV), while maintaining nearly unity power factor and soft switching of power switches simultaneously. However, many CPT systems can only realize either CC output or CV output with the input zero-phase angle. Thus, a high-performance CPT charger should possess at least one CC frequency and one CV frequency to charge the battery from CC mode to CV mode by simply switching the operating frequency. In this article, an LCLC-LC-compensated CPT charger is systematically analyzed to achieve these characteristics. Design principle of the CPT charger is also derived with arbitrarily given coupler and configurable charging profile, proving enough design freedom. Besides, the sensitivities of input impedance, output current, and output voltage to variations of compensation parameters are also discussed to realize soft switching. Finally, an LCLC-LC-based CPT prototype with 48 V/2 A charging capability is built to verify the analysis.

An Isolated Power Factor Corrected Cuk Converter with Integrated Magnetics for Brushless DC Ceiling Fan Applications

The usage of BLDC motors in the low-power range is increasing rapidly in home appliances such as ceiling fans. This has necessitated the development of reliable, compact and efficient AC-DC power supplies for motor drive circuitry. This paper presents a power supply design consisting of an AC-DC isolated PFC Cuk converter with integrated magnetics that supplies a single-shunt voltage source inverter for the sensorless drive of the BLDC fan motor. The proposed power supply design is comprised of an integrated magnetics structure in which the two inductors and the transformer windings share the same core. The zero input and output ripple current conditions have been derived from the reluctance model of the magnetic assembly. Smooth operation of the motor by minimizing the motor torque ripples is evident from the results. The Cuk converter operates in continuous conduction mode (CCM), employing the current multiplier method. The CCM-based current multiplier control loop ensures a near-unity power factor as well as low total harmonic distortion in the supply current. The current loop also provides over-current protection, enhancing reliability of the system. Moreover, the speed of the BLDC motor is controlled by the field oriented control (FOC) algorithm, which enables direct operation with alternate energy sources such as batteries and solar photovoltaic panels. The performance of the proposed supply is validated: motor torque ripple is reduced to only 2.14% while maintaining 0.999 power factor and only 4.72% THD at full load. Failure modes analysis has also been performed through software simulations, using the PLECS simulation environment. Due to the reliable power supply design with low ripples, it is well suited for low-power BLDC motors in home appliances and small power tools, in addition to ceiling fans.

A Novel Clamp Coil Assisted IPT Battery Charger With Inherent CC-to-CV Transition Capability

A constant current (CC) output followed by a constant voltage (CV) threshold is usually needed for an inductive power transfer (IPT) charger to comply with the battery charging profile. This letter proposes a novel clamp coil assisted IPT battery charger that features inherent, passive, automatic, and smooth CC-to-CV transition. Since the CC-to-CV transition eliminates the necessity of state-of-charge detection, wireless feedback communication, and active control, the proposed IPT charger is rugged and reliable. The inherent CC-to-CV transition capability also tackles the open-circuit risk during a CC charging process. As minimalist design is achieved in the secondary, the proposed IPT charger is suitable for wireless onboard charging applications. Near-unity power factor design is also considered to minimize the voltage-ampere rating and permits soft switching. Experiment results validate the inherent CC-to-CV transition capability.

DC-Link and Switched Capacitor Control for Varying Coupling Conditions in Inductive Power Transfer System for Unmanned Aerial Vehicles

The use of wireless power transfer technology in unmanned aerial vehicle (UAV) systems is rapidly improving in different application areas. The main limitations of electric-powered UAVs are their charging range and stability in dynamic conditions. To solve these, this article proposes a hybrid control method based on dc-link and switched capacitor control with a fixed operating frequency. The dc-link voltage is regulated by the boost power factor correction converter to smoothen the output voltage, and the switched capacitor is used to dynamically compensate for self-inductance variations under dynamic coupling conditions. The output voltage stabilization and near-unity power factor of the input impedance can be achieved by applying the hybrid control method. Therefore, efficiency improvement can be achieved. Furthermore, the proposed control method can also be applied to systems with large coupling variations. To verify the proposed control method, a 500-W prototype was set up in the laboratory, and the experimental results proved that the control method could ensure a stable output voltage with horizontal and vertical offsets of 200 and 62 mm. respectively. Additionally, the results show that the maximum efficiency of the proposed control method is 91.9%, demonstrating that the proposed method effectively improves the efficiency.

Inclusive Design and Development of Front-End Multiphase Rectifier With Reduced Magnetic Rating and Improved Efficiency

This article proposes a 20-pulse asymmetric multiphase converter (AMPC) suitable for medium- and high-power applications. Unlike the other state-of-the-art 20-pulse delta-connected autotransformers, the proposed delta-connected AMPC has an ability to reduce input harmonics, maintains high efficiency, and requires a magnetic rating of only 30.12% of the nominal load; thereby, a significant reduction in space, weight, and overall cost required is the salient features of the proposed AMPC. A detailed power quality performance analysis and an efficiency calculation are discussed. First, the proposed AMPC configuration is simulated in MATLAB/Simulink environment for evaluating its viability under different loading conditions, and the results are illustrated. A detailed comparison of the proposed AMPC configuration with other multipulse transformers is included, which confirms the merits of the proposed system. Also, a prototype is developed, and the experimental measurements obtained are presented to validate the feasibility and operability of the proposed AMPC. The proposed AMPC offers a total harmonic distortion of 3.7% and can operate at near-unity power factor complying with the IEEE and IEC standards.

A 20-Pulse Autotransformer Rectifier Unit for More Electric Aircrafts

In more electric aircraft (MEA), the power rating and the number of electric loads have considerably been increased. Most of these new loads are power electronics interfacing loads and motor drive systems. As a result, the onboard power system may encounter with power quality problems. To limit the harmonics generated by these loads, multipulse rectifiers with the capability of power factor correction and low total harmonic distortion (THD) are required. An increase in the number of pulses in the multipulse autotransformer rectifier unit (MPATRU) will lead to an increase in the kVA rating, cost, and complexity of the rectifier. Due to the weightlessness and simplicity of the MPATRU, an autotransformer rectifier unit (ATRU) is quite popular and widely employed in the industry. In this article, a novel 20-pulse ATRU based on T-connected autotransformer is introduced, discussed, simulated, and implemented with an acceptable power rating for MEA applications. The T-connected autotransformer makes use of only two main windings, resulting in saving of space, size, volume, weight, and cost. Its simulation results confirm that the proposed novel rectifier has several advantages: it can operate at near-unity power factor and the THD of the input current is less than 8% within IEEE-519 Standard limits for SCR >20. Compared with the other MPATRUs, the kVA rating of the proposed 20-pulse ATRU is 44.48% of the load power.

A Reconfigurable On-Board Power Converter for Electric Vehicle With Reduced Switch Count

This paper proposes a compact reconfigurable on-board power converter for low voltage electric vehicle. The proposed converter serves the purpose of a battery charger as well as a 3-phase voltage source inverter (VSI) to drive the traction motor. The 3-phase VSI is the backbone of this converter that can be either reconfigured to a propulsion unit or to a battery charger by adding few more power electronics components. During charging mode, the topology is reconfigured to form a front-end boost power factor correction rectifier which is cascaded by a DC-DC converter through a DC link. The same power stage is reconfigured to operate as a 3-phase VSI to drive the traction motor during propulsion mode. Thus, it reduces the switch count by eliminating the requirement of a separate inverter stage. Simultaneously the weight, volume, and cost of the overall system are reduced. Unified control technique is implemented which is capable to achieve near-unity power factor operation of front-end boost rectifier as well as optimal battery charging without sensing the DC link voltage. This control scheme implements a single control loop for both stages by eliminating the need of two separate control loop for each stage of the charger. A 470 W scaled-down prototype is developed and its performance is validated with Constant Current-Constant Voltage charging of a 24 V, 30Ah battery pack in charging mode and with a 400W BLDC motor in propulsion mode.

Coordinated Two-Stage Operation and Control for Minimizing Energy Storage Capacitors in Cascaded Boost-Buck PFC Converters

Cascaded boost-buck PFC (CBBPFC) converters offer a wide voltage conversion ratio and a near-unity power factor but require a large output electrolytic capacitor, leading to poor reliability and power density. In this paper, a coordinated two-stage operation and control strategy is proposed to significantly minimize the capacitor requirement without any other hardware changes. In a conventional CBBPFC converter, the boost and buck stages either operate independently nor complementally. In contrast, the proposed method operates the two stages in a concerted manner, so it is possible to use the dc-link capacitor with certain voltage fluctuation to buffer the power imbalance between the AC input and DC output. A new coordinated control strategy and a fluctuation-ratio based design consideration are developed to coordinate the operation of the two stages, further complement the system design. A 200W CBBPFC prototype based on the design concept exhibits a maximum reduction of the output capacitor by 83%, a peak efficiency of 95.8%, and a power factor of 0.99.

Resonant Bridgeless AC/DC Rectifier With High Switching Frequency and Inherent PFC Capability

Boost-based converters are used in a variety of non-isolated step-up applications, such as power factor correctors, because of their simplicity. The power density of these converters can be increased in higher switching frequencies, which reduces the size of the magnetic elements. This increases the switching losses, but that can be solved by soft-switching techniques. This paper proposes a resonant bridgeless power factor correction converter that provides soft switching for all of the semiconductors. The proposed structure can provide zero voltage switching for the switches and zero current switching for the diodes. In the proposed structure, the input current is inherently sinusoidal with low total harmonic distortion, even with small inductances. Therefore, a high input power factor is achieved without requiring a current control loop in the circuit. This reduces the complexity of the control circuit. An experimental prototype has been constructed to investigate the validity of the claims. Experimental results show near-unity power factor, as well as $\text{2}\%$ efficiency improvement at full load when compared to a conventional interleaved boost converter with the same components.

Near-Unity Power Factor, Voltage Step-Up/Down Conversion Pulse-Width Modulated Switching Rectification for Wireless Power Transfer Receiver

The pulse-width modulated (PWM) switching rectification that can achieve a high power factor (PF) for increasing the energy transfer efficiency between an LC resonator and a rectifier and voltage step-up and -down conversion is proposed for a wireless power transfer (WPT) receiver. The proposed method can emulate the switching rectifier as a resistive load by using an inductor and integrated phase synchronizers. Additionally, similar to a switched-inductor converter that controls the duty cycle ratio ( D ), the proposed PWM rectifier can control the output voltage V OUT when the input is a rectified, wirelessly coupled voltage instead of a constant voltage. Thus, unlike a conventional PWM switching rectifier for ac mains, an additional voltage conditioning circuit would not be needed after the proposed rectifier for WPT. The proposed PWM switching rectification is implemented in the AMS 0.18 μ m 1.8 V/5 V CMOS process. PF = 1 is measured, indicating the most efficient energy transfer, compared to only 0.55–0.65 in a peak detection rectifier. Additionally, 88.2% of peak power conversion efficiency of the switching rectifier is achieved, and the maximum output power is 80.3 mW at 500 kHz of the WPT frequency. Moreover, the measured voltage conversion ratios ranging between 0.73× and 2× are demonstrated in this paper.

FPGA Implementation of Passivity-Based Control and Output Load Algebraic Estimation for Transformerless Multilevel Active Rectifier

This paper presents the design and embedded implementation of a robust controller for the transformerless multilevel active monophase rectifier. In order to reduce the effects caused by the uncertainty originated by the output load, an algebraic estimator is devised. Then, a linear controller based on the exact static error dynamics passive output feedback (ESEDPOF) is proposed, where the uncertainty estimation is taken into account. Since the controller estimator is based on the continuous-time plant model, its real-time implementation on a digital platform requires a discretization of the controller under sufficiently fast sampling, such that the properties of the closed-loop nonlinear sampled-data system are preserved. For this reason, the medium-scale field-programmable gate array Spartan-6 XC6SLX16 is used for implementing the ESEDPOF controller, the online algebraic estimator, the enhanced phase-locked loop, and the multilevel pulsewidth modulator. The parallel processing provided by these devices and the capability in the design of custom modules allow optimizing the hardware description and obtaining an update time for the control law of 9.683 $\mu$ s. Experimental validation shows an excellent dynamical performance and a near-unity power factor.