Faz Rahman

Over-voltage protection using power Zener diode for matrix converter and matrix-Z-source converter

This paper proposes a method of over-voltage protection using power Zener diode for ac-ac matrix converter, ac-dc matrix converter, and matrix-Z-source converter. The analysis and design consideration have been explained, and the discussion on both advantage and drawback of this method also has been given. The effectiveness of this method has been experimentally verified.

Sensorless control of linear permanent magnet synchronous motors using a combined sliding mode adaptive observer

A novel combined sliding mode adaptive observer for flux and speed estimation of direct thrust controlled surface mounted Linear Permanent Magnet Synchronous Motor (LPMSM) without using position sensors is proposed. The observer comprises a linear state observer combined with a novel nonlinear sliding mode component. The sliding mode component is improved by using two boundary layers which reduce the chattering without compromising the robustness. The novel observer is experimentally validated. The flux, speed and position estimation errors are small resulting in reliable observer performance.

Performance analysis of a new concentratedwinding interior permanent magnet synchronous machine under Field Oriented Control

This paper analyzes the performance of a new fractional-slot, concentrated-winding (FSCW) Interior Permanent Magnet Synchronous Machines (IPMSM) under Field Oriented Control (FOC). The FSCW IPMSM is being developed vigorously in recent years because of its high-power density, high efficiency, wide field-weakening capability, and high fault tolerance compared to the distributed-wound IPMSMs. The major disadvantage of concentrated winding is often cited to be its non-sinusoidal stator MMF. However, using appropriate combination of slots and poles, nearly sinusoidal EMF and very low cogging torque can be achieved. Although steady-state performance such as efficiency and constant power speed range of this type of PM machines have recently been published, dynamic performances have yet not been reported. The FOC scheme which rely on the machine model, were applied to a prototype a 14-pole/ 18-slot, double layer concentrated-wound IPM machine. The dq model for distributed wound IPMSM was used for the control. This paper investigates performances of the test machine in terms of torque and current ripple, transient responses for the step variations of speed and load under maximum torque per ampere and field weakening control regimes. The experimental results on the concentrated winding IPM machine indicate that the distributed windng dq model is not sufficiently accurate to harness the full capability of the new machine.

An investigation of a segmented rotor interior permanent magnet (IPM) machine for field weakening

The interior permanent magnet (IPM) machine is considered to be the one of the most efficient electrical machine. The high efficiency along with good performance characteristic makes them suitable for drive with wide speed range. The conventional IPM machine has almost nil or very little field weakening range. Many attempts have been made to improve the range by modification of rotor configuration. In this paper, different types of rotor configuration of IPM machine that is suitable for flux weakening operation has been reviewed. A new rotor design of segmented magnet has been studied by finite element (FE) analysis. The result of FE model of segmented magnet rotor and a conventional rotor of IPM machine has been compared and discussed. In the new design an improved flux weakening aspect has been noticed. Since the new design does not need any special construction effort, it could be a better solution for IPM rotor configuration suitable for field weakening operation.

Modulation and Control Schemes for A New Power Converter Based on Z-source and Matrix Converter for ISA 42 V PowerNet System

This paper proposes two arbitrary zero-placement (discontinuous) PWM strategies for DC-AC three-phase voltage-source-inversion and three-phase AC-DC voltage-source-rectification respectively. They are based on the general space vector modulation approach derived from matrix converter theory. The two PWM strategies are sharing the same algorithm in calculating space vector duty-cycles. The one for DC-AC inversion together with the maximum constant boost control method can achieve the controllable boost-type DC-AC inversion after topologically coupling a Z-source network at the power stage. Both the two PWM strategies were verified by simulated implementation in a new converter based on matrix converter theory and Z-source inverter concepts for the study of ISA 42 V PowerNet

Time delay compensation for a current-source active power filter using state-feedback controller

The inevitable time delay in a digital signal processing (DSP) based controller can significantly degrade the performance of an active power filter. With a current-source active power filter (CS-APF) the problem can be more severe as this time delay can excite the filter resonance and cause oscillations in the compensation current. The paper derives the state space model for the CS-APF where the time delay is modeled properly into the state equations of the system. This makes the system dynamic model more accurate and the time delay can be compensated when a controller is designed for the system. State space control strategy is selected for the CS-APF controller. Experimental results from our prototype CS-APF system are presented to show the effect of the time delay on the CS-APF response and the validity of the proposed approach.

Sliding mode control of current-source active power filter with control delay compensation

This paper presents the use of sliding mode control with a current-source active power filter. From the analysis of the system model, a suitable sliding control function is proposed and its implementation on a DSP-based controller is discussed. A new switching control strategy for the active filter converter with sliding mode control is also proposed. In addition, the effect of control delay on the system response is discussed and a simple measure to compensate this delay is presented. Simulation results show the validity the proposed approach.

Cogging Torque and Torque Ripple in a Direct-Drive Interior Permanent Magnet Generator

This paper investigates the cogging torque and torque ripple in high pole number interior permanent magnet generators, designed for direct-drive applications. Two interior permanent magnet rotor topologies — flat-shaped and V-shaped were considered with distributed wound and fractional slot concentrated wound stators. A comparison of torque performances was made between distributed wound and fractional-slot concentrated wound generators. Cogging torque was minimized by finding an optimum magnet pole arc length and torque ripples were minimized by finding optimum slot-opening and flux barrier shape. Design analysis was carried out in finite element models. It was found that flat-shaped rotor topology in the fractional slot concentrated wound stator can provide the best torque performance regarding low cogging torque and torque ripple. This finding was verified in constructed prototype machine.

Study on medium-frequency transformer isolated substation

In this paper study on solid-state medium-frequency transformer isolated substation is modeled in detail. The substation is formed by AC/DC rectifier, six-pulse DC/AC inverter, high-frequency transformer, DC/AC six-diode rectifier and DC/AC inverter. Both AC/DC rectifier at high AC grid-1 side and DC/AC inverter at lower grid-2 side are controlled by proportional resonant controller and are interfaced with the grids through LCL filters. LCL filters interfaced with both grids are optimized and the controller parameters are also optimized using differential evolution algorithm. It is found by adding passive filter between six-pulse inverter and medium-frequency transformer, it is possible to remove most harmonic voltage components and ensure that the voltage applied across medium- frequency transformer can be quite close to sinusoidal waveform. By doing so, the core losses could be effectively contained, thereby leading to higher frequency and efficiency operation.

Plenary talk — The evolution of power electronic converters for electric drive systems

Summary form only given. This talk will trace the evolution and the current state of the art of the power electronic switching devices and inverters/converters for variable-speed motor drive systems. The talk will start with a brief review of the transition from the early thyristors of late 1960s to modern power electronic devices such as IGBT, GTO, and SiC devices. The power switching capacity in terms of voltage and current, switching frequency, efficiency and reliability will be the factors to emphasise the trends and the underlying reasons for their adoption. The topology of an inverter and its controller for bi-directional power follow into a superconducting coil based active filter will also be described.