This paper presents the analysis and design of a multiple feedback loop control scheme for single-phase voltagesource uninterruptihle power supply (UPS) inverters with an L-C filter. The control scheme is based on sensing the current in the capacitor of the load filter and using it in an inner feedback loop. An outer voltage feedback loop is also incorporated to ensure that the load voltage is sinusoidal and well regulated. A general statespace averaged model of the UPS system is first derived and used to establish the steady-steady quiescent point. A linearized small signal dynamic model is then developed from the system general model using perturbation and small-signal approximation. The linearized system model is employed to examine the incremental dynamics of the power circuit and select appropriate feedback variables for stable operation of the closed-loop UPS system. Experimental verification of a laboratory model of the UPS system under the proposed closed-loop operation is provided for both linear and nonlinear loads. It is shown that the control scheme offers improved performance measures over existing schemes. It is simple to implement and capable of producing nearly perfect sinusoidal load voltage waveform at moderate switching frequency and reasonable size of filter parameters. Furthermore, the scheme has excellent dynamic response and high voltage utilization of the dc source.

This paper investigates t h e performance of multiple feedback loop control strategy for single-phase voltagesource UPS inverter with a n L-C fllter. In order t o select appropriate feedback variables and amsew t h e stability of t h e c l d loop operation of t h e overall system, t h e power circuit (inverter and fllter plus load) incremental dynamics is investigated using t h e state-space averaging technique and root locus method. T h e results of t h e stability analysis show that a control scheme which employs t h e filter capacitor current in a n inner feedback loop and t h e load voltage in an outer voltage control loop results in successful operation of t h e UPS system. Computer simulation results of a single-phase voltage-source half-bridge UPS inverter with a second order filter and ILL load is presented to demonstrate the performance of t h e proposed control scheme. Experimental verification of a laboratory model of t h e UPS system is also provided for both linear and nonlinear loads so (UI t o verify t h e predicted performance of t h e system. It is shown t h a t the control scheme offers improved performance measures over existing schemes. It is simple to implement and capable of producing nearly perfect sinusoidal load voltage waveform at moderate switching frequency and reasonable size of Alter parameters. Furthermore, t h e scheme has fast dynamic response and high voltage utilisation of t h e D C source.

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This paper proposes a closed-loop control strategy to operate an off-the-shelf single-phase induction motor (IM) as a symmetrical two-phase IM. The proposed control strategy employs the SFC technique to independently control the stator currents of both the main and auxiliary windings, and make them follow a predefined sinusoidal waveform. Simulation and experimental results show that the proposed scheme is successful in operating the conventional single-phase IM as a symmetrical two-phase IM with fast dynamic and transient responses. In addition, the proposed control system achieves cost-effectiveness in both initial and running costs.Index Terms-Electric motor drive, single-phase induction motor (IM), slip-frequency control (SFC), unsymmetrical two-phase IM.

In this paper, it is proposed to drive a single-phase induction motor with a two-phase supply. The two-phase supply is obtained from the conventional single-phase utility supply by using a two-phase inverter. The adverse effects of most of the harmonics associated with the use of the two-phase inverter are alleviated by cancelinglattenuating the dominant harmonics in the motor terminal voltages using the selective harmonic elimination (SHE) pulse width modulation (PWM) technique.. The performance of the motor is analyzed using computer simulation and is then compared with that of a conventional single-phase capacitor start induction motor. For a comprehensive comparison, the analysis is performed at both the transient and steadystate cases. Furthermore, frequency analysis is conducted with a view to provide more insight into the operation of the proposed scheme. The proposed mode of operation allows the single-phase induction motor to gain the advantages of the poly-phase motor such as starting torque, less torque harmonics and higher rated power. 1. r,=2.0I R, Pc,,e=17s w, X,,,=2.01 Q, r,=1.3 R, &r=&d, p(r,,.,,."+w,"d.p.)=75 w. Where, xmd, X,, are the direct and the quadrature The subscript "6' denotes d-axis quantities,The subscript "q" denotes q-axis quantities, The subscript '3" denotes stator, The subscript "r" denotes rotor,The subscript "P' denotes leakage. mutual reactance, respectively.