Pei-Hwa Huang

Passive fuzzy controller design for nonlinear systems with multiplicative noises

Abstract This paper proposes a passive fuzzy controller design methodology for nonlinear system with multiplicative noises. Applying the Itos formula and the sense of mean square, the sufficient conditions are developed to analyze the stability and to design the controller for stochastic nonlinear systems which are represented by the Takagi–Sugeno (T–S) fuzzy models. The sufficient conditions derived in this paper belong to the Linear Matrix Inequality (LMI) forms which can be solved by the convex optimal programming algorithm. Besides, the passivity theory is applied to discuss the effect of external disturbance on system. Finally, some numerical simulation examples are provided to demonstrate the applications of the proposed fuzzy controller design technique.

Robust fuzzy control for uncertain stochastic time-delay Takagi--Sugeno fuzzy models for achieving passivity

This paper focuses on the robust passive stability and stabilization problems for uncertain nonlinear stochastic time-delay systems. Via the fuzzy modeling approach, the nonlinear stochastic system is described by Takagi-Sugeno (T-S) fuzzy model in which the consequent parts are presented by linear stochastic time-delay differential equation. With Lyapunov-Krasovskii function and improved Jensens inequality, the stability criteria are derived. In addition, the passivity theory is employed to discuss external disturbance effect on system for achieving attenuation performance. According to the proposed design method, the fuzzy controller is carried out by parallel distributed compensation (PDC) concept to guarantee the robust asymptotical stability and attenuation performance of system in the sense of mean square. Finally, a synchronous generator power system is presented to manifest the application and effectiveness of the proposed fuzzy control method.

Fuzzy controller design for passive continuous-time affine T-S fuzzy models with relaxed stability conditions.

In order to design a fuzzy controller for complex nonlinear systems, the work of this paper deals with developing the relaxed stability conditions for continuous-time affine Takagi-Sugeno (T-S) fuzzy models. By applying the passivity theory and Lyapunov theory, the relaxed stability conditions are derived to guarantee the stability and passivity property of closed-loop systems. Based on these relaxed stability conditions, the synthesis of fuzzy controller design problem for passive continuous-time affine T-S fuzzy models can be easily solved via the Optimal Convex Programming Algorithm (OCPA) and Linear Matrix Inequality (LMI) technique. At last, a simulation example for the fuzzy control of a nonlinear synchronous generator system is presented to manifest the applications and effectiveness of proposed fuzzy controller design approach.

Power system stabilizer using local and remote signals

The main purpose of this paper is to study the utilization of wide area (remote) information obtained via synchronized phasor measurement in the design of power system stabilizer. We aim to advance the performance of the conventional power system stabilizer that is designed essentially by using local measurements as input signals. Both the wide area signal from some remote area and the local signal are employed as the input signals for the power system stabilizer installed on the generating unit. The proposed multi-input power system stabilizer is investigated for enhancing the stability of the overall system. Results from applications to a multi-area power system are demonstrated.

Effects of power system stabilizer on inter-area oscillation in a longitudinal power system

Modern power systems bring many benefits but they may also contain many potential problems such as low-frequency oscillations which threat the stability of the system. The main objective of this paper is to report a preliminary study of the effects of power system stabilizer on the small-signal stability and the damping of low-frequency oscillations of a power system which is under fast development and has a longitudinal grid pattern. Spontaneous low-frequency oscillations are potential to occur in the exchange of regional power flow under normal operation, especially in the operation of an interconnected power system with a longitudinal network structure. The inter-area oscillations often have features of being low frequency, lightly damped, and affecting relatively more generating units located in multiple areas. The method of eigen-analysis is utilized to perform the study of the inter-area oscillations with an emphasis on the oscillation mode with low frequency and light damping. The eigenvalue, eigenvector, and participation factors associated with the inter-area oscillation mode are calculated in details and possible locations of PSS are chosen for study accordingly. The results demonstrate for the PSS the effectiveness in damping inter-area oscillatory modes and thus the contribution to the improvement of stability of the study system.

Robust fuzzy control for passive Continuous Stirred Tank Reactor system with multiplicative noise

This paper focused on the robust fuzzy controller design for passive Continuous Stirred Tank Reactor (CSTR) system with multiplicative noise term. In order to simplify difficultly in stabilization problems for considered nonlinear system, the Takagi-Sugeno (T-S) fuzzy model technique was employed to carry out the proposed design method. For considering the real complex operation conditions, the time-varying delay, uncertainties and stochastic behaviors were considered in this paper. During derivation of stability condition, the Lyapunov-Krasovskii function and strictly input passive were applied with Itôs formula. In order to apply the convex optimization algorithm, the sufficient stability condition must be converted into Linear Matrix Inequality (LMI) problem. Finally, a simulation results were proposed to verify the applications of the proposed fuzzy controller design technique for nonlinear CSTR system.

Observer-based robust fuzzy controller design for uncertain stochastic T-S fuzzy model with passivity performance

The issue of observer-based robust passive fuzzy controller design is discussed and investigated in this paper for uncertain stochastic Takagi-Sugeno (T-S) fuzzy model with external disturbance. For describing the stochastic behaviors of system, the stochastic differential equation is used to structure the stochastic T-S fuzzy model for representing the nonlinear stochastic systems. Using the Lyapunov function and passivity theory, the sufficient stability condition can be derived in term of Linear Matrix Inequality (LMI) by Itôs formula. With stability conditions, a less conservatism design method is developed to synthesize the state feedback fuzzy controller and fuzzy observer for guaranteeing the asymptotical stability and strictly input passivity of system in the mean square.

Fuzzy controller design with passivity performance for Single Machine Infinite Bus Power systems

This paper presents a passive affine fuzzy controller design method for a single machine infinite bus power (SMIBP) system with external disturbances. In order to approximate the trajectories of the SMIBP system accurately, the affine Takagi-Sugeno (T-S) fuzzy model is employed to analyze the stability of the system. For resisting the perturbation from the load side or environment, the passivity theory can be employed to attenuate the external disturbance and to achieve system stability. In addition, the Lyapunov function is used to be the storage function that can represent the total energy of the system. Besides, the optimal convex algorithm and iterative linear matrix inequality (ILMI) algorithm are proposed to solve the present control problem. Finally, simulation results are provided to show that the proposed fuzzy controller can achieve the strict input passivity and Lyapunov stability for the SMIBP system.

Load Modeling Study Using Measurement Data for Taiwan Power System

The modern power system is an integrated complex dynamic system. Due to its scale and complexity, the power system operation and control heavily rely on numerical simulations based on power system models which includes load models. It has been observed that using different load models in the power system simulation may produce quite different, and even contradictory simulation results. Although the importance of load modeling on system dynamics has been well known, load modeling is still a very challenging problem. Thus, there remains a strong necessity for the development of an accurate dynamic load model for power system dynamic analysis because an inaccurate load model may mislead system operators and planners to make incorrect decisions. A Load Model Parameter Derivation (LMPD) program developed by EPRI has been used to investigate the measurement based approach of modeling loads. This paper presents the study results of deriving the load parameters by using measured data of the events from Taiwan Power system. Thirteen disturbance events from over 500 events in the Taiwan power system have been selected, and then the load model parameters are derived via the measurement data of those events. In this paper, the LMPD method is first introduced. Then the procedures of data processing and event selection are briefly discussed. Study results, which provide the static and dynamic parameters of load at each substation, and observations are presented and analyzed. The final part is conclusions.

Study on Communication Protocol Application in Smart Grid

The main purpose of this paper is to study the application of IEC61850 in the smart grid. Smart grid is going through significant development due to the inclusion of microgrid in a view to increasing power capability and decreasing power losses and pollution. IEC61850 provides one feasible solution for integrating various functions of intelligent devices in the smart grid. The message interchange via IEC61850 is based on TCP/IP network protocol and the broadcasting mode. It is found that the information communication among Intelligent Electronic Devices (IEDs) can be achieved by the proposed network protocol based on IEC61850 and GOOSE application.