• Proceedings of the KIPE Conference
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• 2003.07b
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• pp.965-968
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• 2003

This paper describes the PWM-VSI controller of three-phase UPS system using stationary reference frame. This controller meets the specification the UPS inverter output voltage even under the unbalanced or nonlinear load. This controller is also constructed with duble control loop of the outer voltage control loop and the inner current control loop. For the fast response of the output voltage control, yhr inner current control loop of the capacitor current os used. To get the good property against overshoot, the If controller us used. The outer voltage controller is designed with P controller and the high gain transfer function is used for the zero steady state error. All control gains of both controller is designed base on the CDM method.

• Journal of Power Electronics
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• v.10 no.5
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• pp.518-527
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• 2010

This paper presents a new technique for directly designing a linear digital controller for a single-phase pulse width modulation (PWM) converter systems, based on closed-loop identification. The design procedure consists of three steps. First, obtain a digital current controller for the inner loop system by using the error space approach, so that the power factor of the supply is close to one. The outer loop is composed of a voltage controller, a current control loop including a current controller, a PWM converter, and a capacitor. Then, all the components, except the voltage controller, are identified by a discrete-time equivalent linear model, using the closed-loop output error (CLOE) method. Based on this equivalent model, a proper digital voltage controller is then directly designed. It is shown through PSim simulations and experimental results that the proposed method is useful for the practical design of PWM converter controllers.

• The Transactions of the Korean Institute of Power Electronics
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• v.5 no.2
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• pp.115-122
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• 2000

In design of a digital current controller for a 3cP PWM converter, its conventional model is used in obtaining i its discretized version. But, it has errors since the characteristics of SVPWM and time delay are not taken i into consideration. In this paper, the new reference frame model of a 3c~ PWJVI converter is proposed C considering these problems. Also, the direct digital current controller based on this model is designed without a any extra algolithm. A simple tuning algorithm for the proposed current controller is given to compensate the i inductaηce mismatch problem. Then simulation and experimental results show the validity of the algolithm.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.6
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• pp.767-781
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• 2013

In this paper, we proposes the AC input voltage and current sensorless control scheme to control the input power factor and DC output voltage of the three-phase Z-source PWM rectifier. For DC-link voltage control which is sensitive to the system parameters of the PWM rectifier, fuzzy-PI controller is used. Because the AC input voltage and current are estimated using only the DC-link voltage and current, AC input voltage and current sensors are not required. In addition, the unity input power factor and DC output voltage can be controlled. The phase-angle of the detected AC input voltage and estimated voltage, the response characteristics of the DC output voltage according to the DC voltage references, the FFT results of the estimated voltage and current, efficiency, and the response characteristics of the conventional PI controller and fuzzy-PI controller are verified by PSIM simulation.

• Journal of Power Electronics
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• v.11 no.1
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• pp.64-73
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• 2011

The stability of PWM rectifiers with a deadbeat current controller is seriously influenced by computation time delays and low-pass filters inserted into the current-sampling circuit. Predictive current control is often adopted to solve this problem. However, grid current predictive precision is affected by many factors such as grid voltage estimated errors, plant model mismatches, dead time and so on. In addition, the predictive current error aggravates the grid current distortion. To improve the grid current predictive precision, an improved deadbeat current controller with a repetitive-control-based observer to predict the grid current is proposed in this paper. The design principle of the proposed observer is given and its stability is discussed. The predictive performance of the observer is also analyzed in the frequency domain. It is shown that the grid predictive error can be decreased with the proposed method in the related bode diagrams. Experimental results show that the proposed method can minimize the current predictive error, improve the current loop robustness and reduce the grid current THD of PWM rectifiers.

• Journal of Power Electronics
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• v.14 no.6
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• pp.1322-1333
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• 2014

To track the sinusoidal current under stationary frame and suppress the effects of low-order grid harmonics, the multi-resonant quasi-proportional plus resonant (PR) controller has been extensively used for digitally controlled LCL-type pulse-width modulation (PWM) converters with capacitor-current-feedback active damping. However, designing the controller is difficult because of its high order and large number of parameters. Moreover, the computation and PWM delays of the digitally controlled system significantly affect damping performance. In this study, the delay effect is analyzed by using the Nyquist diagrams and the system stability constraint condition can be obtained based on the Nyquist stability criterion. Moreover, impact analysis of the control parameters on the current loop performance, that is, steady-state error and stability margin, identifies that different control parameters play different decisive roles in current loop performance. Based on the analysis, a simplified controller design method based on the system specifications is proposed. Following the method, two design examples are given, and the experimental results verify the practicability and feasibility of the proposed design method.

• Proceedings of the KIEE Conference
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• 1995.07a
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• pp.410-412
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• 1995

From the cost-effective product point of view, it is very important to design a new current controller with the highest utilization factor of current capacity of power devices. This paper deals with a state-deadbeat current controller for PWM converters, which shows the fastest current control response without overshoot irrespective of the saturation of control voltage. No-overshoot control response means that the current capacity could be fully utilized in the control sense. Simulational results done by Matlab's Simulink show good current control characteristics.

• Journal of Power Electronics
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• v.14 no.2
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• pp.302-314
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• 2014

Due to advancements in power electronics and inverter topologies, the current controlled multilevel voltage-source pulse width modulated (PWM) inverter is usually preferred for accurate control, quick response and high dynamic performance. A multilevel topology approach is found to be best suited for overcoming many problems arising from the use of high power converters. This paper presents a comprehensive review and comparative study of several current control (CC) techniques for multilevel inverters with a special emphasis on various approaches of the hysteresis current controller. Since the hysteresis CC technique poses a problem of variable switching frequency, a ramp-comparator controller and a predictive controller to attain constant switching frequency are described along with its quantitative comparison. Furthermore, various methods have been reviewed to achieve hysteresis current control PWM with constant switching frequency operation. This paper complies various guidelines to choose a particular method suitable for application at a given power level, switching frequency and dynamic response.

• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.3
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• pp.303-312
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• 2002

In this paper, a fuzzy logic controller(FLC) for parallel operation system of PWM converters with high performances is proposed and a PI controller is also realized to compare with the performances of the proposed FLC. The simulation and experimental results show that performances of the proposed FLC are far more excellent compared with those of PI controller, especially in points of DC voltage transient response characteristics and current control transient response characteristics at step increase of rated load. To verify the superiorities of the proposed FLC and actually apply it in industrial field, Simulation iud experimental results are provided to verify the implemented a PWM converter system with 15kw capacity in paralleled with two 7.5kW PWM converters.

• Proceedings of the KIEE Conference
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• 1997.07f
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• pp.2210-2212
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• 1997

A sensorless input current controller for three phase PWM converter is proposed. A merit of this controller is that sinusoidal input line current, unity power factor, and ripple-free DC voltage can be achieved with low-cost. The paper describes the proposed control strategy and its implementation. Simulation result for the proposed controller is compared with that of the sensor based version.