In this paper, a nonlinear controller with a currentlimitingudproperty is proposed to guarantee accurate dc outputudvoltage regulation and unity power factor operation for singlephaseudPWM rectifiers without the need of a phase-locked-loopud(PLL). The proposed current-limiting controller is fully independentudof the system parameters and can guarantee asymptoticudstability and convergence to a unique solution for the closedloopudsystem using nonlinear control theory. Without requiringudthe instantaneous measurement of the grid voltage, a PLL,udan external limiter or a saturation unit, the proposed strategyudguarantees that the input current of the rectifier will alwaysudremain below a given value. An analytic framework for selectingudthe controller parameters is also presented to provide a completeudcontroller design procedure and it is also proven that the currentlimitingudproperty is maintained even when the grid voltageuddrops. Extensive experimental results are presented to verifyudthe proposed controller when the load changes, the referenceuddc output voltage changes and the grid voltage drops.
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