Digital Power Factor Research Articles

An intelligent digital low voltage power factor optimizer

In this paper, an intelligent digital low voltage power factor optimizer has been built. This power factor optimizer operates according to the measurement the value of phase shift angle between both of current and voltage, thus the power factor has been measured. It is simply that it will improve the power factor through connecting a set of shunt capacitors in order to reach to an optimal value of the power factor (close to unity). The proposed intelligent digital power factor optimizer for low voltage is built and simulated using the software which is called electronic work bench package (EWB) Multisim. Finally, this optimizer presents a good result when applied to different loads and variable currents. This optimizer is feasible, affordable and ready to be implemented especially in countries that suffer from higher prices of electrical power.

A Digital Power Factor Controller for Primary-Side-Regulated LED Driver

In this study, a digital primary-side controller for a flyback light-emitting diode driver with superior line regulation, high power factor (PF), and low total harmonic distortion (THD) was proposed. Conventional constant on-time control is hampered by input current distortion, leading to high THD. To achieve high PF and low THD, a digital switching frequency limiter with quasi-resonant control was proposed. In addition, owing to the turn-off delay of the MOSFET and propagation delay of the feedback signals, a primary-side-controlled flyback converter experiences poor line regulation. To achieve superior line regulation, delay compensation was proposed and analyzed. A digital controller was realized using a field-programmable gate array and was applied to an input voltage of 90– $264~V_{\mathrm {ac}}$ and an output current of 1 A in a hardware prototype to verify the feasibility of the proposed control solution. The experimental results indicate that line regulation was within ±3%, PF was higher than 0.95, and THD was lower than 5% at universal input voltage.

Novel Online Parameter Tuning Method for Digital Boost PFC With Transition Current Mode

A new online parameter tuning method for digital power factor corrector (PFC) with transition current mode (TCM) control is proposed in this paper. The proposed method copes with the parameter variation issue, which results in discontinuous current mode operation and larger current ripple. The proposed method is to give one more current sample in one sampling period in order to estimate the inductance of a boost inductor online, thereby tuning the parameter of the predicted switching period. It will be shown by experimental results that the proposed online parameter tuning method can retain TCM operation even under full-load condition and slightly increase the converter efficiency. Experimental results derived from a digital-signal-processor-based controller are presented for confirmation. The PFC is with 270-W power rating, 100-V/50-Hz input, and 385-V/dc output. Experimental results demonstrate the effectiveness of the proposed online parameter tuning method for digital PFC under TCM control.

Contribution to digital power factor correction controllers in high intensity discharge lamps electronic ballast applications

Utility voltage fluctuations not compensated by the low-frequency voltage loop of the power factor correction (PFC) stage cause a perceptible variation in the light emitted by lamps, unpleasant for the human eye and known as flicker effect. A novel extension of the digital control for PFC stages analyses the input voltage, detects the fluctuations in the range of human flicker sensitivity and modifies the PFC output voltage controller to avoid their propagation to the DC bus. The purpose of the controller is to make the PFC compatible with any second stage lamp driver, assuring the mitigation of the lamp light variation caused by utility disturbances in consistent with the human eye perception. The controller is implemented in a field programmable gate array. A constant lamp luminance is achieved with this digital controller with no dependence on the next ballast stage.

Single ADC Digital PFC Controller Using Precalculated Duty Cycles

Traditional digital power factor correction (PFC) uses three sensors to measure the input and output voltages and the input current. Each sensor, especially the input current one, increases the cost of the system and generates power losses in case of resistive sensors. This paper presents a controller for boost PFC converters. It uses precalculated duty cycles generated offline, and applies them to the switch. In order to control the converter with nonnominal conditions, just one analog-to-digital converter (ADC) is used, which measures the output voltage. Measuring the average and the ripple of the output voltage with this ADC, the controller takes compensation action for changes in the input voltage but also in the load of the converter. The average value is used to control the input voltage changes, while the ripple value is used to control load changes. These two loops present low frequency bandwidth, so the ADC and the whole system can be low cost. Finally, a comparator is used to detect the zero-crossing of the input voltage, so the precalculated values are synchronized with the ac mains. In this way, the converter only uses one ADC and one comparator, both with low bandwidth. Results show that high power factor and normative compliance are reached, even under nonnominal conditions.

Methods of power factor correction

This paper shows the possibility of electromagnetic compatibility problems when using different equipment and justifies the necessity of usage of power factor correctors to reduce the negative impact on mains by electricity consumers. The basic methods of correcting the power factor are considered. Comparison of the methods of control for high-frequency power factor correction devices is carried out, for each method the functional electrical scheme is shown. The advantages of digital control systems over analog are specified. The forecast of a possible future transition to digital power factor correction systems is made.Reference 6, figures 5.

A digital prediction algorithm for a single-phase boost PFC

A novel digital control algorithm for digital control power factor correction is presented, which is called the prediction algorithm and has a feature of a higher PF (power factor) with lower total harmonic distortion, and a faster dynamic response with the change of the input voltage or load current. For a certain system, based on the current system state parameters, the prediction algorithm can estimate the track of the output voltage and the inductor current at the next switching cycle and get a set of optimized control sequences to perfectly track the trajectory of input voltage. The proposed prediction algorithm is verified at different conditions, and computer simulation and experimental results under multi-situations confirm the effectiveness of the prediction algorithm. Under the circumstances that the input voltage is in the range of 90–265 V and the load current in the range of 20%–100%, the PF value is larger than 0.998. The startup and the recovery times respectively are about 0.1 s and 0.02 s without overshoot. The experimental results also verify the validity of the proposed method.

Single-Phase PFC Converter for Plug-in Hybrid Electric Vehicle Battery Chargers

In this paper, a front end ac–dc power factor correction topology is proposed for plug-in hybrid electric vehicle (PHEV) battery charging. The topology can achieve improved power quality, in terms of power factor correction, reduced total harmonic distortion at input ac mains, and precisely regulated dc output. Within this context, this paper introduces a boost converter topology for implementing digital power factor correction based on low cost digital signal controller that operates the converter in continuous conduction mode, thereby significantly reducing input current harmonics. The theoretical analysis of the proposed converter is then developed, while an experimental digital control system is used to implement the new control strategy. A detailed converter operation, analysis and control strategy are presented along with simulation and experimental results for universal ac input voltage (100–240V) to 380V dc output at up to 3.0 kW load and a power factor greater than 0.98. Experimental results show the advantages and flexibilities of the new control method for plug-in hybrid electric vehicle (PHEV) battery charging application. DOI: http://dx.doi.org/10.11591/ijpeds.v2i3.1255

A Simple Digital Power-Factor Correction Rectifier Controller

This paper introduces a single-phase digital power-factor correction (PFC) control approach that requires no input voltage sensing or explicit current-loop compensation, yet results in low-harmonic operation over a universal input voltage range and loads ranging from high-power operation in continuous conduction mode down to the near-zero load. The controller is based on low-resolution A/D converters and digital pulsewidth modulator, requires no microcontroller or DSP programming, and is well suited for a simple, low-cost integrated-circuit realization, or as a hardware description language core suitable for integration with other power control and power management functions. Experimental verification results are shown for a 300-W boost PFC rectifier.

Digital power factor control and reactive power regulation for grid-connected photovoltaic inverter

The overall efficiency of photovoltaic (PV) systems connected to the grid depends on the efficiency of direct current (DC) of the solar modules to alternate current (AC) inverter conversion. The requirements for inverter connection include: maximum power point, high efficiency, control power injected into the grid, high power factor and low total harmonic distortion of the currents injected into the grid. An approach to power factor control and reactive power regulation for PV systems connected to the grid using field programmable gate array (FPGA) is proposed. According to the grid demands; both the injected active and reactive powers are controlled. In this paper, a new digital control strategy for a single-phase inverter is carried out. This control strategy is based on the phase shift between the inverter output voltage and the grid voltage, and the digital sinusoidal pulse width modulation (DSPWM) patterns, in order to control the power factor for a wide range of the inverter output current and consequently the control and the regulation of the reactive power will be achieved. The advantage of the proposed control strategy is its implementation around simple digital circuits. In this work, a simulation study of this strategy has been realized using Matlab/Simulink and PSIM. In order to validate its performance, this control has been implemented in a FPGA. Experimental tests have been carried out demonstrating the viability of this control in order to control the power factor and the injected power into the grid.

New digital control method for power factor correction

For conventional digital power-factor correction (PFC) control methods, the duty cycle is calculated in every switching period. One main implementation barrier for the digital control of PFC is the limited switching frequency due to the limited processor speed. A new digital PFC control method is proposed to solve this problem. Based on the input current and duty cycles of the previous half-line periods, the new digital PFC control method uses an optimization algorithm to generate all of the duty cycles in advance, which are required to achieve PFC for one half-line period. Total harmonic distortion, which is directly related to the power factor, is adopted as the objective function. The proposed new digital PFC control strategy overcomes the problem of limited switching frequency due to a limited digital signal processor (DSP) speed. The proposed algorithm can be implemented by a low-cost DSP. Simulation results show that unity power factor is achieved using the proposed method.

A Digital Power Factor Correction (PFC) Control Strategy Optimized for DSP

A predictive algorithm for digital control power factor correction (PFC) is presented in this paper. Based on this algorithm, all of the duty cycles required to achieve unity power factor in one half line period are calculated in advance by digital signal processors (DSP). A boost converter controlled by these precalculated duty cycles can achieve sinusoidal current waveform. One main advantage is that the digital control PFC implementation based on this control strategy can operate at a high switching frequency which is not directly dependent on the processing speed of DSP. Input voltage feed-forward compensation makes the output voltage insensitive to the input voltage variation and guarantees sinusoidal input current even if the input voltage is distorted. A prototype of boost PFC controlled by a DSP evaluation board was set up to implement the proposed predictive control strategy. Both the simulation and experimental results show that the proposed predictive strategy for PFC achieves near unity power factor.

Digital power-factor correction for a capacitor-charging power supply

The design and construction of a low-power low-cost power supply capable of charging an energy storage capacitor from a 120-V AC source and capable of power-factor correction (PFC) is presented. The load that is generally connected to a capacitor-charging power supply (CCPS) is a pulsed power load (i.e., laser, cardiac defibrillator, or flash lamp). A flyback converter was incorporated into the CCPS because it is capable of charging a capacitor while maintaining a high power factor. The control system of the CCPS uses peak current control to achieve PFC and is implemented using standard off-the-shelf digital logic components. A 300-V prototype has been constructed and tested. The experimental results show that a high power factor is obtained by the CCPS utilizing a flyback converter and the digital logic control system.

Behaviour of power-factor meters under non-sinusoidal current and voltage

Different types of analogue and digital power-factor meters used for low frequencies are studied. Their errors are calculated when the current or voltage waveform is distorted. It is shown that large errors appear under these working conditions. A new measuring instrument is proposed. It has very small errors, even under highly distorted waveforms, having low-pass filters at the inputs to prevent errors generated by high frequency harmonics.

A digital power factor meter based on a ratiometric analogue-to-digital converter

The development of an electronic power factor meter to replace conventional electrodynamic types is described. The design is based on an analogue-to-digital converter (ADC) provided with ratiometric facilities. A signal proportional to the peak voltage (Vm) is applied to the reference input voltage of the ADC, while another signal proportional to the product of the peak voltage (Vm) and power factor (cos phi ) is applied to the analogue input. The result is a power factor reading.

Digital power factor meter based on digital frequency divider

This work relates to the modification of a digital frequency multiplier to perform the operation of dividing two frequencies giving information about power factor (PF) between two phase-shifted sinusoidal signals. The circuit employs both linear and digital integrated circuits in the realization of PF in digital output display form.

A novel digital power-factor meter design

This paper describes a novel design for a digital power-factor (PF) meter. The design is based on a new digital processor that gives an output frequency proportional to its input voltage, as well as a digital output inversely proportional to the input voltage. The output frequency is made directly proportional to the product of the peak voltage and the power factor V m cos ⊘, while the digital output is inversely proportional to the peak voltage V m . The digital and frequency outputs are applied to a binary rate multiplier (BRM). The BRM frequency output is summed over a specified period of time to provide PF information.

Digital power factor meter based on non-linear analogue-to-digital conversion

ABSTRACT The paper describes the development of an electronic power factor meter to replace the conventional electrodynamic type. The design is based on a non-linear analogue-to-digital converter (NL-ADC). Each of the alternating voltage and current signals is applied to a zero-crossing detector and then exclusive OR-ed and filtered to obtain a DC signal proportional to the phase angle between the voltage and current. The NL-ADC introduces a digital number proportional to the square and fourth powers of this DC signal. The power factor is then obtained by using only three terms of Maclaurin's series of the cosine function. A microprocessor-controlled analogue-hybrid computer type EAI-1000 is used in the circuit design which has highly efficient analogue devices.

A digital power-factor meter design

This paper is concerned with the development of a digital power-factor (PF) meter to replace the electrodynamic type. A new method is chosen to perform a PF measurement ; it is baaed on voltage-to-frequency conversion and counting techniques. One voltage-to-frequency converter (VFC) is used to convert the two DC signals into frequencies proportional to Vm and Vm cos φ, where Vm is the peak of the voltage signal and φ is the phase angle between voltage and current. A division scheme is implemented to perform the digital PF measurement.

Digital power factor meter design based on voltage-to-frequency conversion

Digital power factor meter design based on voltage-to-frequency conversion