J.H.R. Enslin

Digital control and optimization of a rolling rotor switched reluctance machine

A motor having a rotor which is free to roll on the inside of the stator, without bearings restraining it to a fixed axis, is proposed. Using the axial rather than the tangential forces between rotor and stator, this motor develops considerable torque at low speeds. A digitally based controller and a power electronic implementation which minimizes vibrational effects and torque pulsations and also increases overall motor efficiency are described. Attention is drawn to the robustness and simplicity of the motor, making it ideal for low-cost applications, where large torque at low speeds is required from a compact gearless construction. Valuable design considerations have been gained by the use of a finite element analysis on the rolling stator switched reluctance motor.<<ETX>>

Digital adaptive control of a three phase dynamic power filter under unsymmetrical loading conditions

A digital adaptive current controller for implementation on a three-phase voltage source inverter is proposed for a demonstration 40 kVA dynamic power filter (DPF). The digital dynamic compensator controller is based on a TMS320E15 digital signal processor (DSP), which will be implemented in a hybrid power compensator of +or-100 kVA power rating. The hybrid power compensator consists of a three-phase thyristor controlled reactive (TCR) source, combined with the three-phase 40 kVA voltage-fed system. The characteristics of the digital current controller for the DPF are introduced and described. Simulation results of this digital control technique on a single-phase DPF are shown and compared with practical results obtained from a low-power (+or-300 VA) single-phase DPF.<<ETX>>

Adaptive control of a TCR for hybrid compensators using the energy distribution optimization approach

An energy related approach for the interpretation and subsequent compensation of electrical power networks is introduced. It is proposed that optimum supply utilization is brought about by the correct time distribution of the energy drawn from the source and supplied to a load. Hybrid compensators are proposed in order to perform cost-effective energy redistribution between the source, the load, and the compensators. A time-domain-based digital adaptive control technique for TCRs (thyristor controlled reactors) in such a compensation system is described. An optimum reactive current is calculated in the time domain, and a linear extrapolation predictor is further implemented in real time to estimate future values of the firing angles for the thyristors. This feature is implemented in order to improve the dynamic response of the system for changing load conditions.<<ETX>>

Drive of a high torque, low speed switched reluctance machine

A novel switched reluctance machine, based on the fact that the rotor rolls on the inside of the stator, is described and evaluated. An efficient power converter for controlling the freewheeling energy in its rotor coils requiring only a low number of switches, is also presented. Tests on an experimental model are compared with theoretical calculation. Attention is drawn to the robustness and simplicity of the motor, so that it can be considered for low cost applications where large torque and low speed are required from a gearless construction.<<ETX>>

A high-frequency matrix converter for high-efficient power conversion in renewable energy systems

A practical power converter based on a high-frequency primary converter and a matrix secondary converter is discussed. The matrix converter is used as a cycloconverter. The high-frequency link power is converted to a 50 Hz sinusoidal output voltage loading with a nonlinear load in general. The results achieved to date indicate that the composite converter can meet the demands of high efficiency, high dynamic response, and low cost. Simulations were used to design the converter topology and the control strategy, while practical results show the performance of the composite converter system, which can be implemented in renewable energy systems.<<ETX>>

Intelligent static VAr compensator control for supply loading optimization

A digitally adaptive static Var compensator (SVC) controller for supply-side loading minimization is proposed. The control scheme is based on a model reference control structure where a model (which includes its nonlinear behavior) for the thyristor controller reactor is present within the digital signal processor. This allows minimization software to use time-domain samples of three-phase line voltages and load currents to minimize the supply side loading (i.e., maximize power factor). This type of control uses the minimization of a cost function and therefore this same controller automatically also compensates for imbalance in a multiphase supply.

A regenerative snubbing technique using a self-oscillating DC to DC converter

The energy dissipated in a snubber circuit is proposed as a power supply for the control electronics and auxiliary equipment in a 5 kVA inverter. The power supply circuit is initially supplied by the main DC supply but automatically changes to the snubber circuit as source when the snubber capacitor voltage exceeds a threshold voltage. This increases the total efficiency and reliability of the power supply system, and its effect on the operation of the high-power converter is illustrated.<<ETX>>

Real-time, dynamic controller for dynamic power filters in supplies with high contamination

A real-time, closed-loop controller system for controlling active power compensators under rapidly varying load conditions is proposed. With the aid of a dedicated signal processor, using correlation algorithms, real-time, analog compensation reference signals for dynamic power compensators are generated. In order to facilitate a cost-effective compensation system, separate compensation of the fundamental reactive power component and the harmonic components is further proposed. An algorithm time of 312 mu s in a 50 Hz system is achieved, providing an effective controller system bandwidth of 1.6 kHz.<<ETX>>

Power measurements in power systems using a personal computer

The need and operational criteria for an instrument capable of performing time-domain electrical power analysis are investigated and justified. The instrument is linked to a host personal computer, which performs the signal processing and mathematical analysis. This time-domain correlation technique can be used to analyze the different power components in power networks and calculate the effects of distortion. Effective compensation of polluted power systems can be designed using this instrument. Practical results have shown the excellent online operational characteristics of this measurement system, with excellent accuracy being obtained in both the time and the frequency domains.<<ETX>>