Analysis and design of a multiple feedback loop control strategy for single-phase voltage-source UPS inverters

Abstract

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.

High-Performance Voltage Controller Design Based on Capacitor Current Control Model for Stand-alone Inverters

“…Although the response of an inverter is faster with a single feedback loop, a multiple feedback loop is more advantageous in shutting off overcurrent and improving the transient response of inductor [1][2][3][4][5][6][7][8]. The multiple feedback loop control method is widely used by researchers because of the ease of implementation and good performance [9,10]. A multiple feedback loop controller is typically composed of voltage control in the outer loop and current control in the inner loop.…”

“…A multiple feedback loop controller is typically composed of voltage control in the outer loop and current control in the inner loop. Numerous control strategies such as PI [9,10], predictive control [11,12], deadbeat control [13,14], and repetitive control [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] are used for controlling the outer and inner loops. However, these controllers have a problem to make a design of controller optimally, which should be considered on both outer loop and inner loop.…”

Simulation of SPWM Control Method for UPS System

“…The simulation circuit is consists of three phase source, controlled rectifier, inverter, SPWM controller, filter, multilevel inner loop controller [9], [10], [11] and three phase nonlinear load. The simulation is done by Matlab /Simulink environment.…”

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“…Switching techniques such as unipolar and bipolar were used in article [1], for analyzing the harmonics in the inverter circuit with filter. Article [2] explains how inverter can be interface with photovoltaic panels to ac network, and also paper discusses how current harmonics in inverter can be eliminated by unipolar and bipolar switching techniques. After simulation result paper concluded that for low value of switching frequency, bipolar switching techniques provide less current distraction but it is not suitable for high switching frequency.…”