Power Factor Control Research Articles

A static and dynamic model of a space vector modulated matrix-reactance frequency converter

The determination of a converter's passive elements and loadability margin for various load and power grid conditions is of great importance to the proper operation of matrix-reactance frequency converters. The modulation strategy of power switches is very important to the voltage gain and input power factor control. The space vector modulation is the most commonly used algorithm for the control of three-phase power converters. In this paper the average-state space method and the two-frequency d–q transformation are proposed as aids in the process of fast verification of the matrix-reactance frequency converter operation under specific conditions. The experimental verification of the proposed model is also presented.

A Single Stage Photovoltaic Inverter With Common Power Factor Control and Maximum Power Point Tracking Circuit

This paper presents a unique approach towards the reduction of steps employed in conversion of power produced by a photovoltaic energy system. When a Photovoltaic system feeds an ac load, the power conditioning system of a Photovoltaic energy conversion system consists of a boost converter at the first stage to boost up the direct current (dc) supply, and an inverter to convert this boosted supply to alternating current (ac) at the second stage. But in this conventional system, losses happen at both the stage which makes the whole system to have low efficiency. The proposed approach in this paper has only one stage conversion. In this single step conversion the direct current supply is boosted and converted to alternating current with the help of a single inverter circuit. This process of power conditioning is carried out with respect to the load connected as well to the maximum power with respect to the variant irradiation and temperature condition. The load connected to the system is tested under varying environmental conditions of the photovoltaic system. Nature of output power from the system is studied by varying the irradiation and temperature of the photovoltaic array.

Elimination of common mode voltage using phase shifted dual source matrix converter with improved modulation index

Purpose – The high-frequency common-mode voltage introduced by power converters, using conventional modulation techniques, results in common-mode current that has the potential to cause physical damage to the shaft and bearings of electric drives as well as unwanted tripping of ground fault relays in motor drives and electrical networks. The paper aims to provide a complete elimination of common mode voltage using a matrix converter (MC) with a new modulation strategy that reduces the size of the power converter system considerably. Further, a new MC topology is proposed to eliminate the common mode voltage with improved voltage transfer ratio (VTR). Design/methodology/approach – The direct MC topology is selected, as it is the only converter topology that has the potential to eliminate common mode voltage in direct AC to AC systems. Using the rotating space vector technique, common mode voltage is eliminated but this reduces the VTR of the converter. To improve the VTR, a modified MC topology with a modified rotating space vector strategy is proposed. In addition, for improving the power factor at the input, the input current control strategy is developed. Findings – The use of rotating space vector technique eliminates the common mode voltage even under all input abnormalities like unbalance and harmonics. By applying positive and negative rotating space vectors, input power factor control can be achieved. However, the control range is limited from unity power factor to the output power factor. It is observed that in the current controlled technique the modulation index reduces further. It is also found that there is a reduction in switching stresses of individual switches in proposed topology compared to direct MC topology. Originality/value – In this paper, a modified rotating space vector technique is applied to the proposed converter topology for elimination of common mode voltage with an increased VTR. The topology can be used for common mode voltage elimination in existing electric drives without the need for modifying the drive system.

Single-phase Active Power Filters With Reduced Number Of Power Switches And Optimum Voltage Control Angle


 This paper proposes some topologies of universal active power filter for single-phase applications with reduced number of components. Some configurations are proposed: two with both series and parallel converters connected in half-bridge, sharing the same d.c.-bus mid-point connection; and the others with the series and parallel converters sharing one leg. It will be demonstrated the existence of a coupling law between the two converters (Se and Sh) related to the voltage capabilities. All configurations compensate current and voltage harmonic and provide power factor control close to unit. Comparisons between the structures are made and the steady-state analysis are also presented to demonstrate that it is possible to obtain an optimum voltage angle in order to reduced the amplitudes of the converters’ currents and, consequently, the total losses of the systems. Simulated and experimental results validate the theoretical considerations.

Probabilistic Approach to Optimizing Active and Reactive Power Flow in Wind Farms Considering Wake Effects

This paper presents a novel probabilistic optimization algorithm for simultaneous active and reactive power dispatch in power systems with significant wind power integration. Two types of load and wind-speed uncertainties have been assumed that follow normal and Weibull distributions, respectively. A PV bus model for wind turbines and the wake effect for correlated wind speed are used to achieve accurate AC power flow analysis. The power dispatch algorithm for a wind-power integrated system is modeled as a probabilistic optimal power flow (P-OPF) problem, which is operated through fixed power factor control to supply reactive power. The proposed P-OPF framework also considers emission information, which clearly reflects the impact of the energy source on the environment. The P-OPF was tested on a modified IEEE 118-bus system with two wind farms. The results show that the proposed technique provides better system operation performance evaluation, which is helpful in making decisions about power system optimal dispatch under conditions of uncertainty.

UNITY POWER FACTOR CONTROL BY PWM RECTIFIER

This paper analyzes the principle of PWM rectifier and presents a unity power factor control method of PWM rectifier. Controller used double closed-loop PI control, which inner use s three-phase input current control method controll ed by unity power factor and outer controls the output DC voltage of rectifier. Voltage phase detection methods which proposed coul d eliminate the affection of the voltage harmonics on phase detection accuracy. The result of the simulation and experiment verify the feasibility and effectiveness of the method.

A Fixed Switching Frequency Direct Torque Control Strategy for Induction Motor Drives Using Indirect Matrix Converter

Direct torque control (DTC) is a very competitive control strategy because of its simple structure and good dynamic performance essentially in terms of torque response. However, there are some drawbacks which need to be eliminated or at least reduced, like the variable switching frequency and torque ripples. Matrix converters are the new generation of power converters which provide a very good quality of input and output waveforms with a controllability of input power factor, a bidirectional power flow and a compact sight structure. In this present paper, we propose a method used for a fixed switching frequency direct torque control (FSF-DTC) using an indirect matrix converter (IMC). This method is characterized by a simple structure, FSF-DTC which causes minimal torque ripple and unity input power factor. Using this strategy, we combine the IMCs advantages with those of DTC schemes. The technique used to obtain the constant frequency, based on a triangular waveform added to the reference of the torque to impose the dynamic of the torque slopes, is combined with the input current space vector to create the switching table for the IMC drives. The input current modulation allows the rectification stage control of the IMC, while the inverter stage is controlled using the classical DTC switching table. Simulation results clearly demonstrate a better dynamic and steady state performances of the proposed method.

High‐efficiency two‐switch tri‐state buck–boost power factor correction converter with fast dynamic response and low‐inductor current ripple

Two-switch tri-state buck-boost power factor correction (PFC) converter operating in pseudo-continuous conduction mode is proposed and analysed in this study. Different from tri-state boost PFC converter, the proposed two-switch tri-state buck-boost PFC converter does not need additional power switch to provide the additional degree of control freedom. Therefore it does not increase the complexity and affect the power conversion efficiency of the PFC converter as in the case of tri-state boost PFC converter. For the proposed two-switch tri-state buck-boost PFC converter, the current control loop and voltage control loop are decoupled, a simple voltage control loop with faster dynamic response can be designed to realise output voltage regulation and the additional degree of control freedom introduced by inductor current freewheeling stage helps to achieve unity power factor control. The operation principle, the input current, the inductor current ripple, the switch component stress and the small-signal characteristics of the proposed two-switch tri-state buck-boost PFC converter are analysed. The simulation and experimental results show that the proposed two-switch tri-state buck-boost PFC converter benefits with fast dynamic response, high-efficiency and low-inductor current ripple over single-switch buck-boost PFC converter or two-switch buck-boost PFC converter operating in continuous conduction mode and discontinuous conduction mode.

Control Strategy of the DC Drive Systems Based on the State Error Port-Hamiltonian Theory

A novel state error port-controlled Hamiltonian (PCH) system method is presented for speed control the direct current (DC) separately excited motor. The unity power factor regulation of three phase pulse width modulated (PWM) rectifier is also implemented. Then, the state error PCH system control theory, the PCH model of the PWM rectifier and DC motor are proposed. Moreover, the control algorithm of the duty ratio switch function is presented for the PWM rectifier. Theoretical analysis and simulation results show that the controller has good speed tracking and unity power factor control performances.

Reactive Power Automatic Compensation Controller Based on PLC

A high reliability, flexible reactive power automatic compensation controller based on PLC is designed, which the structure and principle of the system is explicitly specified. The controller adopts commercial PLC as the control core,TD400C as human-machine interface, and uses ABB RVT-6 power factor controller to control the switching of the capacitor. Blocking structure is used to design software, whose structure is clear and easy to debug and modify. Running result obtained from relevant application describing the novelty of reactive power compensators implemented with new technologies is also described.

Stable V/f control system with controlled power factor angle for permanent magnet synchronous motor drives

This study develops a scalar V/f control system for permanent magnet synchronous motor drives with two stabilising feedback corrections: a voltage-vector speed correction using active power variation, operating only in transient states and a voltage amplitude correction based on controlled power-factor regulation loop, employing reactive power. Motor/generator operating mode is allowed using the active-power sign information. Simulation and experimental results, and comparison with a medium complexity sensorless vector control prove good performance for the proposed control structure in steady and transient states, at low and rated speed operation with rated load disturbances.

Study of New Three- phase Voltage Source PWM Rectifier

It has been established that a mathematical model for the three-phase voltage source PWM rectifier based on the three-phase stationary symmetric coordinate system (a, b, c) and two-phase synchronous rotating coordinate system (d, q); adopted the power feedforward decouping control strategy, a double closed-loop control structure for three-phase voltage source PWM to solve the problem between the active and reactive power coupler. At last, the Space Vector PWM (SVPWM) control strategy has been put forward, which improved the utilization of DC voltage and robustness of the system. The simulation and experiment results show that the system which was designed has good waveform of AC side current, high stability, fast dynamic response speed, and can achieve the two-way flow of energy and the control of unit power factor.

3상 Z-소스 PWM 정류기의 입력 AC 전압 센서리스 제어

Respect to the input AC voltage and output DC voltage, conventional three-phase PWM rectifier is classified as the voltage type rectifier with boost capability and the current type rectifier voltage with buck capability. Conventional PWM rectifier can not at the same time the boost and buck capability and its bridge is weak in the shoot-through state. These problems can be solved by Z-source PWM rectifier which has all characteristic of voltage and current type PWM rectifier. By shoot-through duty ratio control, the Z-source PWM rectifier can buck and boost at the same time, also, there is no need to consider the dead time. This paper proposes the input AC voltage sensorless control method of a three-phase Z-source PWM rectifier in order to accomplish the unity input power factor and output DC voltage control. The proposed method is estimated the input AC voltage by using input AC current and output DC voltage, hence, the sensor for the input AC voltage detection is no needed. comparison of the estimated and detected input AC voltage, estimated phase angle of the input voltage, the output DC voltage response for reference value, unity power factor, FFT(Fast Fourier Transform) of the estimated voltage and efficiency are verified by PSIM simulation.

A Novel Three-Phase Power Factor Correction with Digital Control

A new three-phase power-factor-correction (PFC) scheme is discussed using two single phase power factor correction circuit parallel connected. Two phase orthonormal voltage is produced by means of a auto transformer from a three phase input,fluctuation of neutral point by three single phase power-factor-correction circuit parallel connected is canceled,coupling interference is reduced among three phases,digitally controlled Power Factor Correction Boost Converters is adapted,input current wave sine with unity power factor suppress the secondary harmonic of input AC side is realized,voltage and low current stresses across each switch are reduced. Simulation and experimental results prove that it can achieve high power factor,low current,good capability of anti-interference and high reliability.

Generalized Direct Modulation Control Methods for Matrix Converters under Balanced and Unbalanced Operations

In this paper, the modulation strategy is developed for N-phase to m-phase matrix converters. Three switching strategies based on pulse width modulation (PWM) technique for control of matrix converters are proposed here. These are named positive, negative and combined switching strategies. By these switching strategies, the balanced and unbalanced output voltages are generated by any set of balanced and unbalanced input voltages. In the combined switching strategy, the output voltages can be established from the α part of the positive switching strategy and β part of the negative switching strategy. The factors α and β have a strong influence on the control of the different characteristics such as control of the input power factor regardless of the load power factor, elimination of the input current harmonics, reduction of total harmonics distortion (THD), etc. The proposed control methods can be easily developed for different types of the matrix converters regardless of the number of phases and the type of waveforms in input and output sides. The experimental and simulation results verify the capabilities of the proposed control methods in generating the desired output voltages.

Common-Mode Voltage Reduction Methods for Current-Source Converters in Medium-Voltage Drives

Common-mode voltages (CMVs) can lead to premature failure of the motor insulation system in medium-voltage current-source-fed drives. By analyzing the CMV values at all switching states under different operating conditions of a current-source-inverter (CSI)-based motor drive, this paper first indicates that the CMV peaks are produced by the zero states in most of the cases. The nonzero-state (NZS) modulation techniques employed in voltage-source converters are adapted for use in a space-vector-modulated current-source converter (CSC) to reduce the CMV magnitude. For NZS modulation in CSCs, the nearest three-state (NTS) modulation sequences are designed with good low-order harmonic performances in their linear modulation region of ma ≥ 0.67 and with no increase in the device switching frequency. A combined active-zero-state (AZS) modulation technique is also proposed as compensation, for a lower modulation index in the range of 0.4-0.67, when a compromise is made between the dc-link current minimization and high input power factor control. The simulation and experimental results are provided to validate the CMV reduction effects and harmonic performances of the NTS and combined AZS modulation methods in CSI-fed drives.

Research of Sensorless Drive of Permanent Magnet Synchronous Motor Based on Power Factor Control

For the traditional sensorless vector control systems of permanent magnet synchronous motor, a new sensorless vector control method is proposed based on the power factor control. On the basis of analysis of the mathematical models for the permanent magnet synchronous motor, established a power factor voltage reference frame system. The rotor position and speed is estimated by the control of power factor angle, and then from the point of view of efficiency drive to configure the stator current. This stator current is arranged in the vicinity of the current minimum trajectory. This method not only can control the speed, but also ensure high power factor and high drive efficiency of the permanent magnet synchronous motor. The simulation results proved the effectiveness and feasibility of this control method.

Design and Simulation of the New Three-Phase Voltage Source PWM Rectifier

Based on the principle of the three phase voltage source PWM rectifier, firstly, describes the topology of the three-phase VSR, and establishes the three-phase VSR’s mathematical model based on the three-phase stationary symmetric coordinate system (a,b,c) and two-phase synchronous rotating coordinate system (d,q); then analysis the three-phase VSR’s control strategy, and discusses the feedforward decoupling control strategy of the inner current loop, the outter voltage loop control strategy and the Space Vector PWM (SVPWM) control strategy. Secondly, builds a simulation model, simulates it in Matlab\Simulink environment.The simulation results show that the system has good current waveform of AC side current, high system stability, fast dynamic response speed, and can realize two-way flow of energy, energy feedback, and unit power factor control.

Nine-to-Three Phase Direct Matrix Converter with Model Predictive Control for Wind Generation System

The power conversion from variable AC voltage into a desired AC voltage with fixed magnitude and fixed frequency is attracting more attention especially in case of grid-connected wind generation system. Indeed, the Direct Matrix Converter (DMC) can be used as a suitable solution for such AC/AC conversion to fulfill the requirement of the output voltage with desired magnitude and frequency. Nine to three phase matrix converter developed in this paper is proposed to ensure the conversion of nine-phase input voltage into three- phase voltage, the output current magnitude and frequency control and the input current power factor control. Among the existing control techniques, The Model Predictive Control (MPC) is considered to be one of the most effective control techniques. In this paper MPC is used to control the twenty-seven switches used in the topology of the nine-to-three phase matrix converters, where the main aim is to achieve principal control functions such as, the output current magnitude and frequency control and input current control to ensure a reduced shift phase, hence a nearly unity power factor in the input side of the DMC.

Five-phase AC/DC/AC converter with pulse-width modulation rectifier

The paper presents an AC/DC/AC power electronic converter system with a five-phase two-level active rectifier and a five-phase two-level inverter with a DC-link. This is an extension of a three-phase active rectifier with two additional legs. This topology may find its application in five-phase variable speed generator such as wind electric generator system and in multi-phase electric drive systems. The front end converter has two control loops; the DC-link voltage control and the source side current control with controllable power factor operation. This paper discusses the multiphase active rectifier applications in multi-phase motor drive system. Simple hysteresis controllers are used to control the input from the source and output to the load currents (five-phase induction motor stator current). The validity of the control is validated using analytical and simulation approaches.