This paper develops a self-design model of automatic voltage regulator (AVR) with criteria of performance indices recommended in IEEE Std 421.5. During the control parameters design and model simulation phase, we can verify all performance indices to see if they meet the specification, such as the steady state error in time domain, phase margin, and the zero crossover frequency in frequency domain, etc. So it is easy to create a full design procedure step by step deterministically.In the voltage constant mode of the excitation control system of a synchronous generator, there is an exciter time constant compensation function to reduce the effective exciter field time constant and increase the small signal response bandwidth. The exciter time constant compensation consists essentially of a direct negative feedback around the exciter with signal coming from exciter field current (Ife). However, it is the main control loop in field constant mode of excitation system. In a traditional analog-based or in a modern digital-based excitation system, loss of exciter time constant compensation is a failure to cause generator terminal voltage unstable. The deteriorated phase margin will impact on power system stability maybe, or result in unit trip unexpectedly.From the point of operation risk assessment and management, we still have to evaluate stability margin in the design phase. This paper suggests that this failure mode should be taken into design consideration besides small signal performance indices.A simple way to resolve the stability margin is to restore the loop forward gain K2 properly to improve the phase margin. It is also necessary to offer a standard operation procedure (SOP) for operators to follow after loss of exciter time constant compensation function once it really happens.Keywords: generator excitation system, digital-based excitation system, exciter time constant compensation.
I. INTROCTIONWith the adoption of IEEE standard 421.5 in 1992-the "IEEE recommended practice for excitation systems models for power system stability studies", there are many new types of excitation system developed. Most of them are digital-based with microprocessor technology implemented for the control algorithms. In doing the simulations, however, there are various models for excitation systems but no general approach for parameters setting, even for the IEEE and IEC standard.A digital-based computer model for a newer controller on excitation system is the subject of this paper. To solve the problems of parameters setting, a methodology satisfying its performance index is proposed.In the voltage constant mode of the excitation control system of a synchronous generator, there is an exciter time constant compensation function to reduce the effective exciter field time constant and increase the small signal response bandwidth. Especially in a high initial response field controlled alternator excitation system, exciter time constant compensation plays a very important role. Even failure of the exciter field current transducer, th...
-In this paper, a conceptual design and a detailed design of novel cylindrical magnetic levitation stage is introduced. This is came from planar-typed magnetic levitation stage. The proposed stage is composed of cylinder-typed permanent magnet array and semi-cylinder-typed 3 phase winding module. When a proper current is induced at winding module, a magnetic levitation force between the permanent magnet array and winding module is generated. The proposed stage can precisely move the cylinder to rotations and translations as well as levitations with the magnetic levitation force. This advantage is useful to make a nano patterning on the surface of cylindrical specimen by using electron beam lithography under vacuum. Two methods are used to calculate required magnetic levitation forces. The one is 2D FEM analysis, the other is mathematical modeling. This paper shown that results of two methods are similar. An assistant plate is introduced to reduce required currents of winding module for levitations in vacuum. The mathematical model of cylindrical magnetic levitation stage is used for dynamic simulation of magnetic levitations. A lead-lag compensator is used for control of the model. Simulation results shown that the detail designed model of the cylindrical magnetic levitation stage with the assistant plate can be controlled very well.
There is a tendency for excitation control system to upgrade to the digital-based type, with the functions and benefits discussed in [1]. New computer models had been developed for representation of the renewal digital-based excitation system in transient stability studies after IEEE Std 421.5[2] adoption. This paper provides a guide line for replacement of the excitation control system from analog-based to digital-based. These techniques had been used on large steam generator excitation systems of a nuclear power plant in Taiwan.An optimal set of excitation system settings plays a very important role in power system stability. This paper will address the parameters setting and field tuning method for a self-excited exciter rewired to be separated-excited with station auxiliary power. The performance indices were also checked and compared with IEEE Std 421.2[3].
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.