Dumitru Stanciu

Single-phase active power filter with improved sliding mode control

This paper presents a study about a single-phase shunt active power filter with sliding mode control. The operation mode of the shunt active filter is detailed, introducing a new operating mode for the inverter in order to improve the behavior of the line current during the zero-passings. Regarding sliding mode control, the sliding surface, the existence condition and the equivalent control are analysed. The steady-state error is diminished by implementing a proposed sliding surface, which includes the current error and its integral. The expected results are confirmed through simulation.

Streetlight monitoring and control system Part I: System structure

The paper presents the modern street lighting control systems with microcontroller AC regulator for lighting applications [1]. The system makes it possible to accurately control and monitor the lighting. The control cabinets are online all the time; the solution guarantees energy savings, due to the dimming option, traffic safety and lighting comfort. The basic idea of the system is for a group of street lights, typically for a stretch of road, to be controlled by a lighting office.

Zero steady-state error PWM control system for sinusoidal voltage

The paper presents a PWM control system of a sinusoidal voltage using a single-phase inverter that comprises at the output a LC low-pass filter with resistive load. The PWM control strategy of a sinusoidal voltage and the optimization of the control loop via the modulus criterion, for step input signals, are presented. The steady-state error of the PWM control system is analyzed for sinusoidal input signal and methods for reducing the steady-state error by increasing the switching frequency and by adding an integral element series to the modulus criterion optimized controller are presented. If analyzed as a linear system, the addition of an integral element would make the system unstable, due to a double pole in the origin, but it is shown that by analyzing the system as a nonlinear system having an ideal relay-type nonlinearity, stability is preserved. Further, knowing that the steady-state error for sinusoidal input can be nullified by introducing a resonant element, a new utilization of a resonant element is proposed, namely its introduction instead of the integral element in the optimal transfer function according to the modulus criterion. The theoretical considerations are confirmed by simulation results.

Sliding coefficients estimation for fixed frequency sliding mode control of boost converter

The paper presents and analyses a control system for the Boost converter in which sliding mode control and classical PWM are combined into a fixed frequency sliding mode control system that emphasizes the advantages of both control methods. This leads to good responses of the power converter in dynamic and in steady-state regime, but a proper estimation of the control parameters is needed. Thus the fixed frequency sliding mode control is analyzed, the control function, the existence conditions and the stability conditions are calculated. Based on this calculations the conditions for the sliding mode coefficients are determined and interpreted for design purposes. Finally a algorithm for the estimation of sliding mode coefficients is proposed and the stated considerations are verified through simulation.

Design optimization methods of an intelligent controller from a speed control system

The paper presents fuzzy logic simple and combined with evolution strategies and neuro-fuzzy designs of a duty-cycle compensation controller in order to linearize the nonlinear external characteristics family of a step-down or forward DC-DC converter that supplies DC motors. The controller is additionally introduced in high precision speed control systems. Comparisons between classical PI controllers and fuzzy controllers are made. Advantages of combined methods of computational intelligence domain are revealed.

PWM Three-Level Inverter Control

This paper analyses a PWM control circuit for a three-level three-phase inverter. The power circuit of inverter and the PWM control principles, using a mirror triangular waveform, are explained. The output voltages of the inverter are represented by 21 Park vectors, from which 3 vectors are null. The PWM circuits with synchronization, used to control the switches of the inverters, are inserted. A circuit that changes instantaneously two phases each other, maybe used for reversible electric drivers, is proposed. The principle of this circuit issues from producing of two triangular waveforms in quadrature, that by a functional transform are converted into sinus and cosines; these waveforms are inputs of PWM modulator. Experimental results, introduced here, confirm all theoretical assumptions

DSP based vector control system for permanent magnet motors. Part I: Algorithm description

In this paper (part I) a speed control system for a permanent magnet motor (PMM) with sinusoidal stator currents is presented. The vector control algorithm of the PMM, the space vector modulation (SVM), the reconstruction of the phase currents from the current measured through the shunt resistor connected on the d.c.-link of the inverter and the detection of the rotor position are presented. The hardware implementation based on dsPIC30F3010, the corresponding software and experimental results are presented in part II of this work.

DSP based vector control system for permanent magnet motors. Part II: Practical application

In part I a speed control system for a permanent magnet motor (PMM) was presented. In this paper (part II) the practical application, based on the specialized signal microprocessor (DSP) type dsPIC30F3010, the corresponding software and experimental results are presented. Details are presented referring the microprocessor modules used, the software flowchart, the speed and current control loops.

Stability analysis of nonlinear voltage inverter-induction motor system

The paper highlights the increased instability of the induction motor due to the nonlinearity introduced by the voltage inverter, nonlinearity produced by the dead time required for switching devices on the same phase. Voltage errors on phase and between phases against the load null are presented, as well as the fact that phase voltage error against load null is in phase with the current. This permits us to consider that the inverter behaves on each phase as an ideal voltage source series connected with a variable resistance, that leads to an increased motor instability degree. The results obtained by computer simulation are presented.

Design, modeling, simulation and implementation of a switching power supply

The paper presents switching power supplies with MC34063 and muA78S40 monolithic switching regulator subsystems and DC-DC step-down converter. General description of MC34063 and muA78S40 operation modes, mathematical design and PSpice under ORCAD simulation of the whole switching power supply, a numerical example and the practical implementation are included. Some practical considerations are also presented.