Jinmok Lee

Direct Digital Control of Single-Phase AC/DC PWM Converter System

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.

Power Quality Monitoring System Using Power Line Communication

This paper deals with the monitoring of power quality (PQ) variations continuously using power line communication (PLC). The power quality monitoring (PQM) has some merits to send and receive the PQ information without any new network lines as usual as in LAN communication. The PLC hardware and software techniques for PQM that meets the categories of IEEE Std. 1159 are described in this paper with some experimental results and also, this research shows that this system can be effectively applied for the power management of end user

Robust digital controller design for three-phase inverter using CRA method

This paper proposes a CRA based robust digital controller for three-phase PWM VSI inverter. To regulate the inverter output voltage with constant voltage and constant frequency, the usual inverter controller consists of double looped PI controllers. Those are an outer voltage controller and an inner current controller, then the order of system characteristic polynomial is high and so the gain tuning of the controllers is difficult. Considering the limited switching frequency of the devices and sampling frequency of the digital controller, the gain tuning is practically dependent on the engineering experiences with the try and error method. In this paper, the error-space approach is used to get the system model including the controller with low order, and the characteristic ratio assignment (CRA) method is proposed for the design of robust controller which has the advantage to design the optimal gain to meet the referenced response and overshoot within the limit range. The validity of the proposed controller is verified through the PSiM simulation and experimental results.

CRA based robust digital controller for a single phase UPS inverter

This paper proposes a robust digital controller for PWM voltage source inverter using CRA method. The usual inverter controller for the operation of constant voltage and constant frequency consists of a double looped PI controller for the outer voltage controller and the inner current controller, of which the order of characteristic polynomial is high and so the gain tuning is difficult. Considering the limited switching frequency of the devices and sampling frequency of the digital controller, the gain tuning is usually based on the engineering experiences with the try and error method. In this paper, the error-space approach is used to get the system model including the controller with low order, and the characteristic ratio assignment (CRA) method is proposed for the design of robust controller which has the advantage to design the optimal gain to meet the referenced response and overshoot within the limit range. The PSiM simulation and experience results are shown to verify the validity of the proposed controller.

Power disturbance classifier using wavelet-based neural network

This paper presents a wavelet-based neural network technology for the detection and classification of the various types of power quality disturbances. For the detection and classification of the PQ transient signals, it should be done at the same time and the automatic methodology is recommended. In this paper, the hardware and software of the power quality data acquisition system (PQDAS) is proposed. In this system, the auto-classifying system combines the properties of the wavelet transform and the advantages of neural networks. Especially, the additional feature extraction to improve the recognition rate is considered. The configuration of the hardware of PQDAS and some case studies are also described.

Decoupling IPD controller design for three-phase DC/AC inverter

This paper presents a decoupling IPD voltage control for three-phase DC/AC inverter. Though most of three-phase inverter system for UPS or stand alone renewable energy system have been analyzed by using DQ model and controlled with IPD controller. For the simplification of this DQ model coupled each other, DQ decoupling technique is proposed firstly and so the MIMO system can be changed to SISO system. Secondary, the CRA based design procedure for IPD controller is presented and it satisfies the specified time response and overshoot of the controller, of which parameters are determined practically by trial and error method. Finally, the performance of this proposed algorithm is verified through PSiM simulation.

Direct digital control of PWM converter using closed-loop identification

This paper presents a new technique of designing a direct digital controller for a single-phase pulse width modulation (PWM) converter system, based on closed-loop identification. It is difficult to analytically design a controller due to the double loop structure of the PWM converter control system. The design procedure consists of three steps. First, obtain a current controller for the inner loop system by using the error space approach, which is a powerful method for robust tracking control design. The outer loop is composed of a voltage controller, a current control loop including the current controller, a PWM converter, and a capacitor. Then, all the components, except the voltage controller, are identified by a discrete-time equivalent linear method, using the closed-loop output error (CLOE) method. Based on the 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.

Power quality monitoring system using wavelet-based neural network

This paper presents a wavelet-based neural network technology for the detection and classification of the various types of power quality disturbances. Power quality phenomena are short-time problems and of many varieties. Particularly, the transients happen during very short durations to the nano- and microsecond. Thus, a method for detecting and classifying transient signals at the same time and in an automatic way is recommended. The proposed wavelet network (WN) combines the properties of the wavelet transform and the advantages of neural networks. Especially, the additional feature extraction to improve the recognition rate is considered. The configuration of the hardware of WN (PQ-DAS) and some case studies are described.

Decoupling voltage controller design with time response specifications for three-phase DC/AC inverter

This paper presents the design controller satisfied with time specification by user for three-phase DC/AC inverter. To design the controller, a pole placement method and CRA (characteristic ratio assignment) method are used. Until now, the relationship between the characteristic function and the time response has been analyzed in only low order system less than second. Eventually, pole placement method is based on response of second order system. So it is hard to get the good result because it has two fixed pole. However CRA method can find controller gains though characteristic equation is high order. That controller satisfies time response specification. This paper shows the way to decide overshoot and settling time. Finally, the performance of this proposed algorithm is verified through PSiM simulation.

Robust Controller Design of a Single-Phase AC/DC PWM Converter

This paper proposes a robust digital controller for a single phase PWM converter. The proposed controller is based on a characteristic ratio assignment (CRA) method which has the ability to deal with the overshoot and response speed of an all-pole system directly. The error-space feedback control scheme to carry out the robust AC current tracking is used which is well known as an analytic state-feedback method to give a controller the ability to track a non-decaying input perfectly and to reject a non-decaying disturbance such as a sinusoidal input firstly. And then, the CRA design formulates a model matching problem whose reference model is selected from a target polynomial. So the state feedback gains can be determined by the CRA method instead of the pole-placement method. Finally, the validity of the proposed control technique is verified through the PSiM simulation and experimental results.