B.J. Cook

Digital hardware implementation of a current controller for IM variable speed drives

This paper presents the design of an induction machine current controller that is entirely implemented in digital hardware. A hardware current controller allows high switching frequencies with only modest processing power as well as simplified controller hardware and software. The paper briefly presents the concepts of the algorithm implemented, and then outlines the changes that are made to make the digital implementation even more efficient. It then discusses the architecture used for the hardware design. Experimental results are presented to demonstrate the algorithms performance.

Outline of the Control Design for a Cascaded H-Bridge STATCOM

The cascaded H-bridge converter (CHC) topology is ideal for implementation of direct connection static compensators (STATCOMs). However the topology requires significantly different control strategies as compared to conventional two level transformer connected STATCOMs and other multilevel STATCOMs. This paper outlines all aspects of a novel controller for a CHC STATCOM, from the capacitor voltage balancing, limiting strategies, through to the real and imaginary power loops. Simulation and experimental results are presented to demonstrate its viability and performance.

A digital current controller for three phase voltage source inverters

The usual techniques for implementing current control for hard switched inverters usually involve PI control or hysteresis based control. PI strategies suffer from poor transient performance, and the latter requires complex analog circuitry to give a constant switching frequency. This paper describes a new current control algorithm suitable for implementation in software or digital hardware. A novel feature of the algorithm is that it is able to identify the required machine parameters online. Furthermore there is no tuning of control parameters required from the user. The algorithm output is the switching times for the inverter switches. Comprehensive simulation results are presented, and issues related to hardware digital implementation are presented.

Nonlinear Adaptive Control of an Inverter-Fed Induction Motor Linear Load Case

An adaptive nonlinear control system for an inverter-fed induction motor is presented. The approach taken is fundamentally different from previous work on induction motor control in that the aim is to control shaft speed directly. Further, the inverter control variables, frequency and-voltage, are related via the steady-state model to the shaft speed and motor current. By making the controller adaptive, neither load nor machine parameters need be specified, although in practice the, latter are usually available from the machine manufacturer, and, of course, full use can be made of this knowledge.

Optimal Pulsewidth Modulation for Current Source Inverters

This paper describes an off-line pulsewidth modulation (PWM) technique intended for the reduction of detrimental current harmonics in current source inverter systems. The procedure is based on the minimization of the amplitudes of offending harmonics through the determination of optimal-pulse positions using a gradient primal-dual algorithm.

Instantaneous power control-an alternative to vector and direct torque control?

This paper presents a new algorithm for the control of AC machines based on the concept of controlling the instantaneous real and imaginary power. This strategy, called instantaneous power control (IPC), allows decoupled control of the torque and flux in the machine. This paper outlines the basic algorithm and then presents simulation results of its performance.

Outline of the design of a cascaded H-bridge medium voltage STATCOM

The University of Newcastle and its joint venture company, ResTech Pty Ltd, are developing a cascaded H-bridge based multilevel STATCOM. This tutorial paper outlines the salient design issues for this system. The issues covered in the paper include the choice of the converter topology, the structure of the control system hardware, the software structure and methodology, some details on the control algorithm, and the rationale behind the design decisions.

Practical aspects of instantaneous power control of induction machines

High performance induction machine control is usually implemented using field oriented control (FOC) or direct torque control (DTC). These strategies have their strengths and weaknesses. The concept of instantaneous power control (IPC) has been used in power compensators and to control the voltage on the DC link of inverters, but it is a new concept for the control of induction machines. The idea is that by controlling the instantaneous real and imaginary power into the machine one can control the torque and flux of the machine. This paper outlines the development of the algorithm, and then focuses on some practical issues associated with the implementation of the algorithm.