C.F. Christiansen

Sliding mode control of wind energy systems with DOIG-power efficiency and torsional dynamics optimization

Wind turbines with double output induction generators can operate at variable speed permitting conversion efficiency maximization over a wide range of wind velocities. However, random wind fluctuations, wind shear and tower shadow, may excite the oscillation mode of the mechanical system, producing large torque ripple. Consequently, damage to drive train components and power quality problems may occur. In this paper, a sliding mode control is developed which provides a suitable compromise between conversion efficiency and torque oscillation smoothing. The resultant sliding dynamics is completely robust to uncertainties in the electrical variables and parameters. In addition, to prevent windup problems due to saturation, a combined sliding surface that incorporates such limitations is proposed.

A synchronization technique for static delta-modulated PWM inverters

A synchronization technique for static delta-modulated PWM inverters is presented. This control strategy removes the frequency modulation inherent in the delta-modulated inverter. Furthermore, synchronization of the PWM pulses with the reference signal ensures balanced phase voltages in three-phase applications. The performance of the modulator is analyzed using digital simulations and is verified with experimental circuits. >

Brief paper: Multivariable PID control with set-point weighting via BMI optimisation

The paper focuses on the design of multivariable PID controllers with set-point weighting. The advantage of this PID structure is that the responses of the system to disturbances and to changes in the set-point can be adjusted separately. The proposed design methods rely on the transformation of the tuning of the controller gains into a static output feedback (SOF) problem. Hence, multivariable PID controllers can be designed by solving an optimisation problem with bilinear matrix inequalities (BMIs). The paper addresses the design of both time-invariant and gain-scheduled robust controllers. All of the tuning methods discussed through the paper are based on a PID structure with filtered derivative term, thus guaranteeing the well-posedness of the closed loop system.

Dynamical sliding mode power control of wind driven induction generators

Summary form only given as follows. This paper concerns power regulation of variable-speed wind energy conversion systems. These systems have two regions of operation, depending on the tip speed ratio of the wind turbines. They are distinguished by a minimum phase behavior in one of these regions and a nonminimum phase one in the other. A sliding mode control strategy is proposed that assures stability in both regions of operation and imposes the ideally designed feedback control solution in spite of model uncertainties. Moreover, power regulation by the proposed sliding control in the minimum phase region is completely robust to wind disturbances and parameter uncertainties.

Power FET Controlled Dimmer for Incandescent Lamps

V-shaped metal-oxide-semiconductor (VMOS) dimmers in direct and inverse phase control schemes are analyzed and compared with conventional thyristorized ones. The absence of turn-off circuits and bulky radio frequency interference (RFI) filtering circuitry are the main advantages of the method. A 1-kW prototype with closed-loop overcurrent protection in an inverse-phase-control version is presented.

Spectral analysis of a synchronized delta modulated PWM inverter

Abstract A spectral analysis of a synchronized delta modulated PWM inverter is performed. In order to fulfill this purpose, the modulation process is modelled. A simplified model, that has been previously obtained from a phase plane analysis, is improved with a detailed study of the transient behaviour. The simulated model and the experimental set-up show a close correspondence between them.

Design of a DSTATCOM using a 5-level cascade asymmetric multilevel converter

The power quality in distribution systems is affected by the pollution introduced by the customers. One way to improve the power quality is using a DSTATCOM to compensate reactive power and harmonics. The use of multilevel inverters in medium voltage applications is a good solution. In particular, the cascaded asymmetric multilevel converter (CAMC) appears as a very attractive alternative among the 5-level converters for this application. In this paper, the design of a DSTATCOM employing a CAMC in a medium voltage distribution power system, is presented. The model and the control strategy are discussed in d-q coordinates. The performance of the proposed compensator is tested with SPICE simulations.

Analysis of the synchronized delta modulated PWM inverter: mathematical model

In this paper, the performance of a synchronized delta modulated PWM inverter is studied analytically. This modulation strategy allows one to obtain an output waveform continuously variable from a nearly sinusoidal to a square wave without an increase in circuit complexity. The analytical solution allows learning about the harmonic spectra and the amplitude of the first harmonic of the inverter output wave, when the reference frequency varies over a wide range. These results can be profitably used in the inverter design, in order to obtain a proper control circuit according to the power stage requirements.