E. Akpinar

Modeling and performance of slip energy recovery induction motor drives

This program can be used to examine the transient performance of slip energy recovery drives for the proper rating of semiconductor devices or to examine the effects of faults on the associated power system on the drive performance. Current and speed controllers designed using linear techniques can be evaluated using this program as well. A computer using a fourth-order Runga-Kutta integration routine has been developed that uses a newly proposed model to predict the detailed operation of a slip energy recovery drive both in the transient and in the steady state. The hybrid model is between the well-known d, q and the phase variable models and retains the actual rotor states. This makes it possible to include the rectifier commutation impedance without any difficulty. The harmonics of the rectifier and inverter are not neglected, as was often done in the literature. Variables such as the DC link current, rotor phase current, stator current, and inverter recovered current were predicted accurately. Commutation overlap was incorporated into the model and predicted accurately, both in the steady-state and transient conditions. >

Harmonic analysis and performance improvement of slip energy recovery induction motor drives

Slip energy recovery induction motor drives are used in high power applications, in which by controlling the slip power a variable speed drive system is provided. However, poor power factor is a disadvantage of the system. Presence of sub-harmonics of the line frequency on the stator side is one of the special features of these drives. A phase-controlled inverter can absorb the reactive power from the supply and inject the low-order current harmonics with relatively high amplitudes to the supply. This paper simulates the harmonic content of waveforms in various points of drive at different speeds, based on the hybrid model (dqabc). Then the sinusoidal pulse-width-modulation (SPWM) control technique is used in order to improve the power factor of the drive and to weaken the injected low-order harmonics to the supply. Based on the frequency spectrum, total harmonic distortion, distortion factor and power factor, two phase control and SPWM techniques are compared and the advantage of the SPWM technique over the phase control technique is shown.

A computer program to predict the performance of slip energy recovery induction motor drives

Details are provided, in the form of a flowchart, to permit the reconstruction of a computer program to predict the transient and steady-state performance of slip energy recovery induction motor (IM) drives. Slip energy recovery IM drives are different from most other drives in that the inverter is generally connected only after the machine has reached a predetermined speed. The initial conditions of the inverter are therefore nonzero and difficult to obtain. Three techniques that can be used to calculate the initial conditions are discussed. Theoretical predictions are supported by practical results. >

Starting transients in slip energy recovery induction motor drives. I. Formulation and modeling

The authors examine the starting transients of slip-energy recovery induction motor (IM) drives when started directly with the rotor rectifier. The starting transients of slip energy recovery IM drives comprising three stages are presented: starting from zero speed with a starting resistor connected to the output of the rectifier; the transmission period in which the inverter is connected through a DC link; and the final period when the starting resistor is disconnected from the rectifier output. A hybrid model is used which retains the actual rotor phase variables but transforms those of the stator only, to examine the starting transients of a slip energy recovery drive system. >

Wavelet transform application in active power filter used for slip energy recovery drives

In this paper, discrete wavelet transform (DWT) and symmetrical component (SC) analysis are used together for extracting the fundamental component and oscillations in supply current drawn by slip energy recovery drive (SERD). Discrete Meyer wavelet is used as mother wavelet due to its orthogonal and biorthogonal properties to generate reference signal for active power filter (APF) in order to compensate current harmonics. Simulations are performed wing Matlab Simulink and Wavelet Toolbox. Simulation results show that the DWT algorithm can abstract the fundamental component of supply currents effectively and the oscillations in the supply currents are considerably reduced when the DWT is combined with SC analysis for generating the reference current of the APF.

Transformerless Single Phase Inverter Design for LCD Television

A LCD (liquid crystal display) has the CCFL (cold cathode fluorescent lamp) for backlight illumination. The CCFL is fed at high voltage and high frequency voltage by an inverter in the LCD TVs. The backlight unit consumes almost %40 of input power. The inverter with step-up transformer for this unit is commonly supplied from the switch mode power supply. In this work, a parallel resonance inverter without a step-up transformer is used to eliminate the transformer power loss. The circuit is analyzed in PSPICE package program and the results are compared with implementation.

Cascade PI controller for single-phase STATCOM

This paper presents state space model of singlephase STATCOM based on continues switching function. Continues switching functions for bipolar voltage source inverter (VSI) have been used to derive the transfer function for complete controller. Two proportional integral (PI) controllers which are a DC PI for DC link voltage control and an AC PI for alternating current control are implemented in cascade topology in reactive power compensation. Proposed control method has been analyzed in simulation by using MATLAB. Root locus technique is used to design AC PI controller parameters.

Assessment of two different reactive power estimation methods on single phase loads

In this paper single-phase instantaneous reactive power (p-q) method and non-active current method have been compared. Reactive power and reactive current calculation using these methods have been considered here under distorted voltage and current waveforms. It has been shown that these two methods have some limitations for reactive power compensation. The p-q method with hysteresis current controller and non-active current theory with sinusoidal pulse width modulation (SPWM) controller have been analyzed in Matlab/Simulink. A prototype system has been designed using TMS320F2812 EzDSP in the laboratory and assessment based on simulation and experimental results is given for these methods in this paper.

Calculation of the overlap angle in slip energy recovery drives using a d,q/abc model

A closed-form expression for estimating the overlap angle in a slip energy recovery system is presented. The prediction of the overlap angle is important in the case of doubly-fed induction motor drives, because of its influence on speed and torque. A closed-form expression is derived using a hybrid model of the induction motor and a dynamic model of the rotor rectifier. The ripple content of the DC link current and the inverter input voltage are neglected. The results predicted by the closed-form expression are verified experimentally. >

Starting transients in slip energy recovery induction motor drives. II. Flowchart and performance

For Pt.I, see ibid., vol.7, no.1, p.238-44 (1992). The authors present a flowchart for the solution of the system equations developed in part I and present detailed simulation results, backed up with a detailed set of experimental and theoretical results, to give insight into the expected behavior of the drive. The starting resistor allows the peak motor torque to be developed at starting or for the starting currents to be limited to a prespecified value. The transients associated with the initial connection of the inverter can be limited by the appropriate choice of the inverter firing angle. A transient occurs when the resistor is finally disconnected because of the removal of a parallel current path. Both the overlap in the rotor rectifier and the harmonics reflected by the inverter have been included in the modeling and the computer program. This removes the need for correction factors to be used in the design of a practical drive. >