S. M. Allam

Maximum power tracking of a grid-connected wind-driven Brushless Doubly-Fed Reluctance Generator using scalar control

This paper presents a scalar volt per hertz (v/f) control technique for maximum power tracking of a grid-connected wind-driven Brushless Doubly-Fed Reluctance Generator (BDFRG). The proposed generator has two stator windings namely; power winding, directly connected to the grid, and control winding, connected to the grid through a bi-directional converter. The presented control technique is based on the abc-axis and dq-axis dynamic model of BDFRG. A detailed abc-axis and dq-axis dynamic model, by which the dynamic behaviour of the BDFRG can be successfully predicted under different operating conditions, is presented. In addition, a soft starting method is suggested to avoid the over-current of the bi-directional converter. The presented simulation results ensure the effectiveness of the proposed control strategy for maximum wind-power extraction under wind-speed variations.

A simple CB-PWM technique for five-phase matrix converters including over-modulation mode

This paper presents a simple carrier-based PWM (CBPWM) technique to control a three-phase to five-phase matrix converter (3×5 MC). The proposed technique is based on the indirect configuration of the matrix converter in which the three to five-phase matrix converter is modeled as three-phase rectifier followed by a five-phase inverter. With this representation, CBPWM technique is suggested to control both stages in both linear and over-modulation modes. Using the proposed modulation technique, the maximum possible voltage transfer ratio (VTR) of the converter in the linear and over-modulation modes is achieved. The proposed modulation technique is modeled using Matlab/Simulink software and the overall system algorithms are compiled to a real time system based on DS1104 controller. A sample of the obtained experimental results is presented to support the viability of implemented three to five-phase matrix converter with the proposed modulation technique.

Vector control strategy for maximum wind-power extraction of a grid-connected wind-driven Brushless Doubly-Fed Reluctance Generator

This paper proposes a vector-control (power-winding flux orientation) strategy for maximum wind-power extraction of a grid-connected wind-driven Brushless Doubly-Fed Reluctance Generator (BDFRG) system. The adopted generator has two stator windings namely; power winding, directly connected to the grid, and control winding, connected to the grid through a bi-directional converter. In addition, a unity power-factor operation is also provided based on the proposed vector-control strategy. Moreover, a soft starting method is suggested to avoid the over-current of the bi-directional converter. A sample of the obtained simulation results is presented to check the effectiveness of the proposed strategy.

Voltage and frequency control of a stand-alone wind-energy conversion system based on PMSG

This paper presents a control strategy for a standalone wind-energy conversion system using Permanent Magnet Synchronous Generator (PMSG). The presented control strategy aims at regulating the load voltage in terms of magnitude and frequency under different operating conditions including windspeed variation, load variation and the unbalanced conditions. The wind generating-system under study consists of a wind turbine, PMSG, uncontrolled rectifier, DC-DC boost converter and voltage source inverter. The presented control strategy is based firstly upon controlling the duty cycle of the boost converter in order to convert the variable input dc-voltage, due to different operating conditions, to an appropriate constant dc-voltage. Hence, a sinusoidal pulse width modulated (SPWM) inverter is used to regulate the magnitude and frequency of the load voltage via controlling the modulation index. In order to verify the performance of the employed wind generating-system, a sample of simulation results is obtained and analyzed. The presented simulation results show the effectiveness of the employed control strategy to supply the load at constant voltage and frequency under different operating conditions.

Indirect space-vector PWM technique for three to nine phase matrix converters

This paper develops indirect space vector modulation technique for a three- to nine-phase matrix converter. The proposed technique is based on the double-stage configuration in which the matrix converter is modeled as three-phase rectifier followed by a nine-phase inverter. Both rectifier and inverter stages are controlled using space-vector modulation technique. In the rectifier stage, the modulation is based on input currents space-vectors. However, the modulation of the inverter stage is based on output voltages space-vectors. Two different schemes are suggested to control the inverter stage. In the first scheme, only largest space vectors are used in order to achieve maximum voltage transfer ratio of the inverter stage. In the second scheme, eight active vectors are used in each sector in order to minimize the switching stresses and to give a sinusoidal output voltage. It is observed that, using the first scheme results in achieving a higher value of the maximum overall voltage transfer ratio. However, the output voltages contain a significant amount of lower order harmonics. On the other hand, sinusoidal output voltages with a reduced value are obtained by second scheme. A sample of the obtained simulation results is presented to support the viability the proposed technique.

A sensorless scalar-control strategy for maximum power tracking of a grid-connected wind-driven Brushless Doubly-Fed Reluctance Generator

This paper presents a sensorless scalar volt per hertz (v/f) control technique for maximum power tracking of a grid-connected wind-driven Brushless Doubly-Fed Reluctance Generator (BDFRG). The proposed generator has two stator windings namely; power winding, directly connected to the grid, and control winding, connected to the grid through a bi-directional converter. The capability of the proposed sensorless scalar control for maximum wind-power extraction is based mainly upon the validity of the BDFRG speed-estimation approach. A simple and a cost-effective speed-estimation approach is presented. In order to enhance the performance of the proposed control system, a soft starting method is suggested to avoid the over-current of the bi-directional converter. The presented simulation results ensure the capability and the effectiveness of the presented control strategy for maximum wind-power extraction under wind-speed variations using a sensorless scalar control technique.

Sensored and sensorless scalar-control strategy of a wind-driven BDFRG for maximum wind-power extraction

AbstractThis paper presents a scalar volt per hertz (V/f) control technique for maximum power tracking of a grid-connected wind-driven brushless doubly fed reluctance generator (BDFRG). The proposed generator has two stator windings namely; power winding, directly connected to the grid and control winding, connected to the grid through a bi-directional converter. In order to enhance the performance of the proposed scalar-control strategy, a soft starting method is suggested to avoid the over-current of the bi-directional converter. Moreover, the capability of generator speed estimation for sensorless control is also studied. The capability of the proposed scalar-control technique is validated using a sample of simulation results. In addition, the presented simulation results ensure the effectiveness of the proposed control strategy for maximum wind-power extraction under wind-speed variations. Furthermore, the results show that the estimated generator speed is in a good accordance with the actual generato...

Maximum power extraction under different vector-control schemes and grid-synchronization strategy of a wind-driven Brushless Doubly-Fed Reluctance Generator

This paper proposes an advanced strategy to synchronize the wind-driven Brushless Doubly-Fed Reluctance Generator (BDFRG) to the grid-side terminals. The proposed strategy depends mainly upon determining the electrical angle of the grid voltage, θv and using the same transformation matrix of both the power winding and grid sides to ensure that the generated power-winding voltage has the same phase-sequence of the grid-side voltage. On the other hand, the paper proposes a vector-control (power-winding flux orientation) technique for maximum wind-power extraction under two schemes summarized as; unity power-factor operation and minimum converter-current. Moreover, a soft-starting method is suggested to avoid the employed converter over-current. The first control scheme is achieved by adjusting the command power-winding reactive power at zero for a unity power-factor operation. However, the second scheme depends on setting the command d-axis control-winding current at zero to maximize the ratio of the generator electromagnetic-torque per the converter current. This enables the system to get a certain command torque under minimum converter current. A sample of the obtained simulation and experimental results is presented to check the effectiveness of the proposed control strategies.

A comparative study of vector-control strategies for maximum wind-power extraction of a grid-connected wind-driven brushless doubly-fed reluctance generator

Abstract This paper proposes a vector-control technique of a grid-connected wind-driven Brushless Doubly Fed Reluctance Generator (BDFRG) for maximum wind-power extraction under three strategies, summarised as unity power-factor operation, minimum converter current and minimum copper losses. The adopted generator has two stator windings namely; power winding, directly connected to the grid, and control winding, connected to the grid through a bi-directional converter. In addition, a soft starting method is suggested to avoid the employed converter over-current. The first control strategy can be achieved by adjusting the command power-winding reactive power at zero for a unity power-factor operation. However, the second strategy depends on setting the command d-axis control-winding current at zero to maximise the ratio of the generator electromagnetic-torque per the converter current. This enables the system to get a certain command torque under minimum converter current. On the other hand, the third strategy can be realised by determining the control-winding current angle at which the BDFRG can operate with minimum copper losses. A sample of the obtained simulation results is presented to check the effectiveness of the proposed control strategies.

Load voltage control and maximum power extraction of a stand-alone wind-driven PMSG including unbalanced operating conditions

This paper presents a control strategy to enhance the performance characteristics of a stand-alone wind-driven Permanent Magnet Synchronous Generator (PMSG) under different operating conditions. The presented control strategy aims at regulating the load voltage, in terms of magnitude and frequency and extracting the maximum wind-power under both constant wind-speed and variable wind-speed including both balanced and unbalanced loading conditions. The wind generating-system under study consists of a wind turbine, PMSG, switch-mode rectifier (three-phase uncontrolled rectifier followed by DC-DC boost converter), bidirectional DC-DC buck-boost converter, battery bank, three-phase SPWM inverter, LC filter, three-phase isolating transformer and three-phase load. The employed control strategy is firstly based up controlling the duty cycle of the DC-DC boost converter, included in the switch mode rectifier, in order to extract maximum wind-power. Then, the operating mode (charging or discharging of the battery bank) of the bidirectional DC-DC buck-boost converter is controlled to attain an appropriate constant dc-voltage under different operating conditions. Finally, a sinusoidal pulse width modulated (SPWM) inverter is used to regulate the magnitude and frequency of the load voltage via controlling the modulation index. A sample of simulation results is obtained and analyzed in order to check the capability of the presented control strategy of the employed wind generating-system. The presented simulation results verify the effectiveness of the presented control strategy to supply the load at constant voltage and frequency with maximum wind-power extraction under different operating conditions.