Current Error Control Research Articles

Random slope PWM inverter using existing system background noise: Analysis, design and implementation

Random slope PWM (RSPWM) is one of the most easily realised RPWM techniques for reducing the acoustic noise due to PWM switching harmonics. However, it is difficult to analyse it in closed form and it is thus difficult to design quantitatively. The development of an RSPWM inverter using existing system background noise and its applications are presented. First, the effects of the random signal's attributes on the harmonic spectrum distributed characteristics of the RSPWM inverter output are observed intuitively. Then according to the observed phenomena, a quantitative design procedure is derived through using the equivalent instantaneous frequency change concept. For the ease of implementation, the random signal used for random slope modulation is extracted from the current tracking control error signal with suitable filtering. Finally, the realisation of the designed RSPWM scheme using a commercially available voltage-controlled oscillator integrated circuit is achieved. The designed RSPWM inverter is employed to power an induction motor drive, and its effectiveness is demonstrated experimentally.

Stability Analysis of the Direct Field Oriented Control System of the Induction Motor without a Speed Sensor using the Adaptive Rotor Flux Observer

The vector control of the induction motor without a speed sensor required the estimations of the rotor flux and the rotor speed. Since the estimations use the machine parameters and the stator voltage and current components as input quantities, the stability of the systems is sensitive to the variations of the machine parameters and the measured stator voltage errors and the current control errors compared with the vector control systems with a speed sensor.In this paper, the small signal stability analysis is carried out on the direct field oriented control system of the induction motor without a speed sensor using the adaptive rotor flux observer (MRAS method) and allows for the stability effects of the stator resistance and rotor resistance and the gain of the speed controller to be studied. The stability effects of the MRAS method are compared with that of the vector control system of the induction motor without a speed sensor based on _??_1q-feedback control (_??_1q-feedback method). Furthermore, theoreitical step responses of the rotor speed are compared with the experimental results.

Speed Sensor-Less Vector Control of Secondary Flux Controlled Induction Motor.

The vector controlled induction motor has been widely used for variable speed drive systems and its application fields are expanding. In these application fields, drive systems without various sensors are expected to be realized from a simplicity and reliability standpoint.The paper presents a new type of sensor-less vector controlled Induction Motor (IM), that is, the secondary flux controlled IM without a speed and a voltage sensors. Since the original secondary flux control does not have a direct current loop which is commonly used in the conventional vector control, the proposed sensor-less algorithm is based on the current control error caused by an estimation error of speed. The proposed system only requires a current detector, and whole control processing including the vector control and the speed estimation is performed by a software using DSP-TM S 32010 within 99 μs. The experimental result showed the steady state speed control range of 1:30 under rated load and of 1:100 under no load conditions, respectively. Moreover, an adaptive operation to the unknown mechanical parameter using a learning process was introduced and, as a result, the specified speed transient characteristics were realized.

Phasor-Based Instantaneous Current Control of Single-Phase PWM AC/DC Converter.

This paper presents a current control strategy for a single-phase PWM AC/DC converter. The input current is sinusoidal and an effective power factor is unity. Since the control variables of the single phase converter are sinusoidal, the conventional control strategy requires high control gains to achieve zero steady state error. However, the gains are limited because of sampling delay.To solve the problem, the authors propose a new current control scheme of a single-phase PWM converter which has two special features: One is that a fast response of current is achieved by introducing a converter model in the controller. Another one is that the steady-state AC current control error is canceled even if the parameter differences between the converter model and the actual converter exist. Moreover, the steady-state current error can be eliminated under low gains by a feedback loop of the fundamental component of current error.The experimental data show the proposed control to be effective.

Suppression of converter introduced harmonic currents using a forced-commutated cycloconverter

A method of current harmonic suppression through application of a modified forced-commutated cycloconverter is described. The cycloconverter is operated using current-error control with hysteresis. Advantage is taken of the multiple source voltage switching choices available with the cycloconverter to produce corrective harmonic current injection that tracks the command with minimum error. A numerical simulation of the filter is made with a three-phase, six-pulse rectifier load. The results are presented in the forms of both harmonic residual components and Fourier spectra. >