Zhishan Liang

Design of stabilizing controllers of upper triangular nonlinear time-delay systems

Abstract In this paper, it is considered the state feedback controller design for a class of upper triangular nonlinear systems with simultaneous input and state delays. By using the state transformation of nonlinear systems, the problem of designing controller can be converted into that of designing a dynamic parameter, which is dynamically regulated by a dynamic equation. Then, by appraising the nonlinear terms of the given systems, a dynamic equation can be delicately constructed. At last, with the help of Lyapunov stability theorem, it is provided the stability analysis for the closed-loop system consisting of the designed controller and the given systems. Both discrete delays and continuous delays with integral form are considered here. Different from many existing control designs for upper triangular nonlinear systems, neither forwarding recursive nor saturation computation is utilized here, and thus our design procedure is simpler. A simulation example is given to demonstrate the effectiveness of the proposed design procedure.

Finite-time consensus of time-varying nonlinear multi-agent systems

This paper investigates the problem of leader–follower finite-time consensus for a class of time-varying nonlinear multi-agent systems. The dynamics of each agent is assumed to be represented by a strict feedback nonlinear system, where nonlinearities satisfy Lipschitz growth conditions with time-varying gains. The main design procedure is outlined as follows. First, it is shown that the leader–follower consensus problem is equivalent to a conventional control problem of multi-variable high-dimension systems. Second, by introducing a state transformation, the control problem is converted into the construction problem of two dynamic equations. Third, based on the Lyapunov stability theorem, the global finite-time stability of the closed-loop control system is proved, and the finite-time consensus of the concerned multi-agent systems is thus guaranteed. An example is given to verify the effectiveness of the proposed consensus protocol algorithm.

The multi-objective coordinated control of excitation and ASVG of SMIB system based on hamiltonian principle

A multi-objective co-ordinated control scheme for ASVG and synchronous machine excitation to achieve transient stability and voltage regulation enhancement of power systems is presented. First, the new third order nonlinear state-space system model for rotor power angle stability is derived for a single-machine infinite-bus power system with ASVG, the new third order nonlinear state-space system model of ASVG for voltage regulation is given. Then, the non-linear property of the dynamic system is well preserved and utilized, which can meet the requirement of power rotor angle stability and that of ASVG voltage support. with the help of Hamiltonian energy control theory, the variation of system structure, the parameter and the interconnection between the synchronous machine and ASVG are taken into consideration in the multi-objective cocoordinate controller design. In the end, the performance of the proposed multi-objective control scheme is evaluated through a real time test by means of the real time digital simulation. It is shown that the proposed multi-objective coordinated control of excitation and ASVG can provide better system stability and local voltage control.

Nonlinear Excitation Model Predictive Control for Electric Power System

Abstract How to improve both power angle stability and terminal voltage dynamic characteristic of generator still stays in the stage of investigation for the whole world. This paper presents a new approach to nonlinear control design for single-generator to infinite bus system using model predictive control theory. The new mathematical model in the form of an affine nonlinear system is set up for the nonlinear excitation control design. The results of computer simulation shows that the proposed approach in this paper can improve both power angle stability and terminal voltage dynamic characteristic of generator, it is more effective than differential geometry theory.

Energy Shaping Repetitive Control (ESRC) for Three-Phase Three-Wire Shunt Active Power Filter

Active Power Filter (APF) is usually used to compensate the harmonic and reactive currents which are generated by the nonlinear load, and its compensation performance mainly depends on the design of controller. When the parameters of the line and load are uncertain or unknown, the system may be unstable. In order to solve this problem, this paper adopts the energy shaping repetitive control (ESRC) to improve the output current waveform of three-phase three-wire shunt active power filter. In this control strategy, the Energy Shaping control is used to guarantee system dynamic performance and the repetitive control is to correct current waveform quality. The new controller design procedure is analyzed in detail. Theoretical analysis and experimental results demonstrate the validity of the proposed method and the filtering performance is improved obviously.

Modeling and performance analysis of the fractional order quadratic Boost converter in discontinuous conduction mode-discontinuous conduction mode

In this paper, based on the fact that the inductors and capacitors are of fractional order in nature, the four-order mathematical model of the fractional order quadratic Boost converter in type I and type II discontinuous conduction mode (DCM)–DCM is established by using fractional calculus theory. Direct current (DC) analysis is conducted by using the DC equivalent model and the transfer functions are derived from the corresponding alternating current (AC) equivalent model. The DCM–DCM regions of type I and type II are obtained and the relations between the regions and the orders are found. The influence of the orders on the performance of the quadratic Boost converter in DCM–DCM is verified by numerical and circuit simulations. Simulation results demonstrate the correctness of the fractional order model and the efficiency of the proposed theoretical analysis.

Modeling and performance analysis of the fractional order quadratic Boost converter in discontinuous conduction mode-continuous conduction mode

Based on the fact that the inductors and the capacitors are fractional order in nature, the four-order mathematical model of the fractional order quadratic Boost converter in discontinuous conduction mode (DCM)-continuous conduction mode (CCM) is established by using fractional calculus theory. Direct current (DC) analysis is conducted by using the DC equivalent model and the transfer functions are derived from the corresponding alternating current (AC) equivalent model. The DCM-CCM region is obtained and the relations between the region and the orders are found. The influence of the orders on the performance of the quadratic Boost converter in DCM-CCM is verified by numerical and circuit simulation. Simulation results demonstrate the correctness of the fractional order model and the efficiency of the proposed theoretical analysis and indicate the fractional model has an important theoretical significance and practical applied value for design and performance analysis of the quadratic Boost converter.

Passivity-based controller design of electric dehydrator

Electric dehydrator plays an important role in oil and chemical industrial production. Control law design method for electric dehydrator is introduced in this paper. A new mathematical model of the power circuit of electric dehydrator is developed. DC side voltage control and unity power factor control based on the passivity-based control technique in the electric dehydrator are investigated in details. Electric dehydrator controlled by the proposed passivity-based control strategy has many advantages, such as, enhancing robustness under model uncertainties, decoupling current-loop dynamics, guaranteeing zero steady-state error and asymptotic rejection of dynamic load disturbance. The results of 60KW prototype electric dehydrator simulation with MATLAB/ SIMULINK show that the passivity-based control strategy is feasible.