Azziddin M. Razali

Analysis and Design of New Switching Lookup Table for Virtual Flux Direct Power Control of Grid-Connected Three-Phase PWM AC–DC Converter

This paper proposes a comprehensive and systematic approach in developing a new switching lookup table for direct power control (DPC) based on grid virtual flux estimation, implemented in a grid-connected three-phase ac-to-dc converter. The approach provides detailed information regarding the effects of a particular converter voltage space vector to the instantaneous input active and reactive power distributions in the converter system. Thus, the optimal converter switching states are able to be selected by the switching table, allowing the smooth control of the active and the reactive power for each sector. The usage of input ac voltage sensors for synchronization and input power calculation is avoided by applying a virtual flux concept in the control scheme. The grid virtual flux estimation technique is used to extract the grid voltage information from the converter switching states, line currents, and dc-link output voltage. Detailed explanation and analysis regarding the development of virtual flux DPC utilizing the proposed switching lookup table is given in this paper. Finally, the steady-state as well as dynamic performances of the proposed controller is tested both in simulations and laboratory experiments. There exist close agreements between the simulation and experimental results.

An Experimental Implementation of the

A successful development and implementation of the dq-axis components and the wavelet packet transform (WPT)-based hybrid technique for power transformer protection is introduced in this paper. In this approach, the high-frequency subband contents of the dq-axis components of the differential current is extracted using the WPT. This characterization helps to provide enough information to efficiently detect and discriminate internal faults from inrush currents in power transformers. This hybrid method provides accurate information with only one level of the WPT of the dq-axis components of the differential current for power transformer protection. A real-time experiment is carried out for different normal and abnormal operating conditions, such as inrush and internal faults for different cases of loading, to test the efficacy of the proposed algorithm. The experimental results show fast, accurate, and reliable responses to all different types of disturbances that may occur in power transformers.

dq

This paper investigates a virtual flux control for reducing the number of sensors in the direct power control of a three phase ac-dc voltage source converter. The usage of input ac voltage sensors to determine the grid voltage angle for synchronization and estimation of the instantaneous active and reactive powers, are avoided by applying a virtual flux concept in the control scheme. The virtual flux control technique is used to extract the grid voltage from the converter switching states, dc output voltage, and line currents. An improved virtual flux direct power control utilizing the new switching table has been proposed in this work. The switching table is developed based on the instantaneous power derivative method which relies on the sign and magnitude of the change in instantaneous active and reactive powers. The steady state as well as dynamic performances of the proposed system are presented and analyzed by means of Matlab simulation and experimental verification.

-Axis Wavelet Packet Transform Hybrid Technique for Three-Phase Power Transformer Protection

This paper investigates a new approach to develop and implement a virtual flux oriented control (VFOC) for the front-end three phase bidirectional voltage source converter (VSC) by adapting the principle operations of voltage oriented control (VOC) and power estimation used in virtual flux direct power control (VFDPC). The proposed VFOC operates with minimal number of sensors by avoiding the used of ac voltage supply sensors. In addition, the proposed control scheme utilizes the direct and quadrature (d-q) decoupling and feed-forward components to enhance the performance of front-end VSC during load and supply voltage disturbances. The steady-state as well as the dynamic performance of the proposed controller is presented and analyzed by means of the Matlab simulation, and verified through experiment. The ac-dc converter utilizing VFOC is able to produce adjustable dc output voltage, fixed switching frequency, unity power factor and low harmonic distortion of the line current.

An analysis of direct power control for three phase AC-DC converter

This paper presents the implementation of Differential Evolution (DE) algorithm to solve Harmonic Elimination Pulse-Width Modulation (HEPWM) problem. HEPWM is widely used in eliminating the low frequency harmonic of output voltage of the inverter. The DE is a simple and efficient evolutionary algorithm in solving the HEPWM transcendental equation. Operations of DE technique were elaborated and the best approach of mutation strategy has been analyzed. Switching angles of HEPWM were calculated offline using DE technique. Then, the switching angles were applied to three-phase voltage source inverter (VSI). Simulation of DE technique and VSI experiment set up were run in Matlab/Simulink.

Real-time implementation of d-q control for grid connected three phase voltage source converter

This paper aims to implement an independent speed control for dual-PMSM drives fed by a single Five-Leg Inverter (FLI). In general, dual-motor drives are designed to reduce size and cost with respect to single motor drives. However, dual-motor drives using a single three-leg inverter has its limitation in the case of operation at different operating conditions and independent speed control requirement. By employing this FLI topology, the dual-motor drives can be used for four-quadrant control, variable speed operation and load disturbance rejection. In other words, it can be operated for different applications. This paper investigates the behaviour of independent speed control for Dual-Permanent Magnet Synchronous Motor drives. The speed and current controllers are implemented in d-q rotor reference frame using Simulink/MATLAB and the switching signals are generated by the built-in function and dSPACE. The overall performance of the drives is presented in terms of speed responses under forward and reverse operation. The three-phase current and quadrature current responses are also included. The experimental results of the drives under investigated study have proven that dual-PMSM can independently controlled by using FLI.

HEPWM using differential evolution technique for three phase voltage source inverter

This paper describes the method to control a hybrid robot whose main task is to climb a pole to place an object on the top of the pole. The hybrid pole-climbing robot considered in this paper uses 2 Planetary PG36 DC-motors as actuators and an external rotary encoder sensor to provide a feedback on the change in robot orientation during the climbing movement. The orientation control of the pole-climbing robot using self-tuning method has been realized by identifying the transfer function of the actuator system under consideration, being followed with the calculation of control parameters using the self-tuning pole-placement method, and furthermore being implemented on the external rotary encoder sensor. Self-tuning pole-placement method has been explored to control the parameters q 0 , q 1 , q 2 , and p 1 of the controller. The experiments were done on a movement path in a form of a cylindrical pole. The first experiment was done based one the change in rotation angle of the rotary sensor with the angle values greater than 50˚ in the positive direction, whereas the second experiment was done with the angle values greater than -50˚ in the negative direction. The experiment results show that the control of the robot under consideration could maintain its original position at the time of angle change disturbance and that the robot could climb in a straight direction within the specified tolerance of orientation angle change.

Independent control for dual-PMSM drives using Five-Leg Inverter

This paper proposes Fuzzy Logic Controller scheme in sensorless (PMSM) drives based on fundamental excitation. Fuzzy Logic Control (FLC) is suitable for a controller design when the system is difficult to model mathematically due its complexity, nonlinearity and imprecision. Especially for sensorless drives of PMSM which uses the complex estimators equations and adaptation mechanism. Fuzzy Logic Controller is widely used in high performance drives to obtain precise speed control irrespective of load disturbances and parameter variations. Most of the sensorless techniques are based on the voltage equations of the PMSM and the information of the terminal quantities, such as line voltages and phase currents. By using this information, the rotor angle and speed are estimated directly or indirectly. This paper presents the sensorless drives based on differential of d-q voltage and current equations, which are manipulated from the fundamental excitation. The elimination of speed sensor in PMSM drives specifically using Fuzzy Logic Controller, will reduce the overall cost, size and complexity without degrading the system performance. The proposed method is simulated by using MATLAB/Simulink. The simulation results of the sensorless PMSM drives are successfully achieved. The applied technique shows good speed regulation and proves that PMSM can be controlled for forward or reverse operating conditions as well as for load disturbance.

An Analysis of Virtual Direct Power Control of Three-Phase AC-DC Converter

This paper presents the solution for odd and even number of switching angles of harmonic elimination pulse width modulation (HEPWM). HEPWM capable to eliminate low order harmonics of inverter output voltage by solving the transcendental equation of the switching angles. The optimum switching angles are calculated using differential evolution (DE) algorithm. DE is simple and effective algorithm. The calculated switching angles applied to the three-phase voltage source inverter (VSI) and harmonic performance of output voltage are examined using MATLAB/Simulink software. The Total harmonic Distortion (THD) of line to neutral of inverter is analyzed for different number of switching angles. The simulation result showed that the low order harmonics, namely 5th, 7th, 11th, 13th, 17th, 19th, 23th was eliminated individually by N=3,4,5,6,7 and 8.

Fuzzy logic controller of PMSM for sensorless drives

This paper presents a vector current controller scheme, which operates according to grid virtual flux orientation for the three phase, 3-wire pulse-width modulated voltage source converter (VSC). The usage of voltage sensors to determine the grid voltage angle for synchronization and the grid voltage magnitude for the controller operation are avoided by applying a virtual flux concept in the proposed control scheme. The virtual flux concept is utilized to obtain the input power equations, which will be used to calculate the reference d (direct) and q (quadrature) axis currents. The estimated grid virtual flux provides a new approach in developing the proposed control structure of three phase VSC by including the d-q axes decoupling and the feed-forward components to enhance the performance of front-end VSC during load and supply voltage disturbances. Computer simulation and laboratory experiment are conducted to verify the operation and performances of the VSC under steady-state and transient conditions. The results indicate VSC utilizing the proposed virtual flux oriented control (VFOC) is able to produce unity power factor operation, low harmonic distortion of input line current, adjustable dc output voltage and fixed switching frequency.