The contribution of this paper is to propose a new design method and a nonlinear optimal control law which are based on the new achievements of differential geometric theory for excitation control of multimachine syst...
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The contribution of this paper is to propose a new design method and a nonlinear optimal control law which are based on the new achievements of differential geometric theory for excitation control of multimachine systems. The model of a multimachine system is set up as an affine nonlinear equation set, which is defined on a manifold M. The control strategy obtained for each individual generator is not only an optimal one but also a decoupled law. The stability of the global multimachine system with the control law and the engineering realization problem of the new control scheme are discussed. And the results of simulation to a six-machine system are quite convincing.
This paper proposes a method to compute the maximal reactive power load which can be consumed at a given set of buses, subject to a set of operating constraints, involving for instance generator reactive production an...
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This paper proposes a method to compute the maximal reactive power load which can be consumed at a given set of buses, subject to a set of operating constraints, involving for instance generator reactive production and bus voltage limits. It can be used in particular to determine margins with respect to voltage collapse or, more generally, with respect to unsatisfactory operation. An efficient decoupling procedure allows solving a reactive power/voltage only problem. The optimization is performed by means of the Newton method and fully exploits sparsity. It is illustrated by several numerical examples.
The presently used TBC and FFC methods have satisfactorily maintained power system frequency within a prescribed tolerance. With steady increase in power system capacity, however, undue fluctuations in tie-line power ...
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The presently used TBC and FFC methods have satisfactorily maintained power system frequency within a prescribed tolerance. With steady increase in power system capacity, however, undue fluctuations in tie-line power flow has become prominent. This fact suggests the shear necessity of establishing a more sophisticated LFC system. Intensive research efforts have been concentrated on applications of modern control theory, above all linear optimal control (LOC) using the state regulator theory. This paper presents a decentralized suboptimal LFC method which makes use of the frequencies of adjacent areas in addition to local information to calculate the control variables of each area. This artifice has made it possible to realize a practical yet almost optimal control scheme. Simulation studies on a 4 area system have demonstrated the effectiveness of the proposed method.
A digital voltage controller is presented, based on the optimal-aim control method, and able to enhance the dynamic and transient stability of single- and multi-machine power networks. The single- and multi-machine co...
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A digital voltage controller is presented, based on the optimal-aim control method, and able to enhance the dynamic and transient stability of single- and multi-machine power networks. The single- and multi-machine controllers are, thus, built upon the same theory, the multi-machine case being a generalization of the single-machine case. The theoretical basis are presented, as well as simulations results on some typical networks. The possibilities to minimize the amount of data transmission between the power plants are also studied and validated.
The dynamic once-through subcritical steam generator model, based on the plant design data, is presented. This model allows the investigation of power plant system transients. Detailed description of the simulation re...
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The dynamic once-through subcritical steam generator model, based on the plant design data, is presented. This model allows the investigation of power plant system transients. Detailed description of the simulation results is documented on the example of once-through subcritical steam generator of 200 MW power unit. For the purpose of both the similarity with the physical process and intelligibility of the model for a design engineer, familiar with technology, the structural boiler model was chosen. This one is composed of the following parts: combustion system, evaporator, uncontrolled and controlled superheater, main steam line, and a representation of the boiler load (steam consumer - reheat turbine). The boiler model is applied both to investigate the dynamical behavior of uncontrolled plant and to verify controllers and control concepts too. As the example of the model used for control testing the cascade superheated steam temperature control is described. The superheater model taken from the whole large boiler model was completed with regulating unit, nonlinearities, etc. Various controllers, especially PI and LQ STC, were compared in the role of the main controller.
The mechanism of nonlinear oscillations induced by static friction in a control valve is discussed. The valve controls the flux of fuel-oil in the start-up firing system of a large coal-fired electric power plant. The...
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The mechanism of nonlinear oscillations induced by static friction in a control valve is discussed. The valve controls the flux of fuel-oil in the start-up firing system of a large coal-fired electric power plant. The existence of static friction in the control valve, combined with other factors, can be a cause of oscillations of the fuel pressure, which may become unacceptable under some conditions. The mechanism that leads to these phenomena is discussed in physical terms and a computer model of the control loops involved is described and used to evaluate a number of strategies. The loss of stability margin due to the presence of the nonlinearity described is discussed and studied by simulation.
When a power system is subject to large network perturbations, the most fundamental questions in steady state analysis are (i) whether a solution for the perturbed load-flow problem exists and (ii) if so, what the sys...
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When a power system is subject to large network perturbations, the most fundamental questions in steady state analysis are (i) whether a solution for the perturbed load-flow problem exists and (ii) if so, what the systems response to the perturbations is. Conventional load-flow based methods seek the solution of the power system nodal equation and hence represent a general approach to the problem. As an expected result, (i) the test for existence of solution are impractical and conservative and (ii) the load-flow solution has to be obtained by iterative means. On the contrary, network-based methods as presented here, are useful only for the study of the power system response to network perturbations. Their basis is a selected form of Tellegen's equation, rather than the system nodal equation. As a result, (i) the tests for existence of solution are simple and expeditious and (ii) the response is evaluated noniteratively. In this paper this alternative modelling of powersystems subject to network perturbations is presented. This includes background review, formulation of the problem in the context of linear systems theory, testing for existence of load-flow solution, development of noniterative formulas, analysis of multiple solution regions, and presentation of illustrative numerical results.
Due to the increasing complexity of electrical networks in developing countries as well as decreasing reserve capacity in the networks of industralized countries, power system restoration is gaining increased interest...
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Due to the increasing complexity of electrical networks in developing countries as well as decreasing reserve capacity in the networks of industralized countries, power system restoration is gaining increased interest. As emphasized in the paper, a reduction of the restoration time requires not only theoretical work, but also the installation and coordinated operation of automatic control facilities in control centers and power plants. Bayernwerke AG, the electricity generation and transport company of Bavaria, has done extensive studies in developing plans for network restoration after major disturbances. For some of these studies the simulation facilities developed at Duisburg University have been instrumental. After a survey of the strategies developed, the paper will shows the simulation results for the cases: Restoration;of the total Bavarian grid system with auxiliary powerfrom external networks, and black start of a partial system.
The paper describes a simulated real-time test bed for the testing and comparison of programs implementing state estimation algorithms. The test bed is used to compare the performance of a program implementing a tradi...
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The paper describes a simulated real-time test bed for the testing and comparison of programs implementing state estimation algorithms. The test bed is used to compare the performance of a program implementing a traditional Newton-Raphson weighted least-squares state estimation algorithm with that of a program implementing a novel state estimation algorithm.
The French power system voltage control is organized in three hierarchical levels, which concern distinct geographical areas and time constants. The rapid and random variations are compensated by local primary and aut...
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The French power system voltage control is organized in three hierarchical levels, which concern distinct geographical areas and time constants. The rapid and random variations are compensated by local primary and automatic actions on the generators ***. Then the slow variations are regulated by the secondary actions (at regional level) and the tertiary actions (performed by an operator at national level). The evolution of the French power system leads EDF to modify the principles of the regional regulator and to develop a new control system called 'Co-ordinated control'. In order to implement this system, robustness studies had to be performed. In this paper we focus on how communication delays may affect the performance of the 'Co-ordinated control' system. In addition we present two methods which ensure its robustness in regard to reasonable delays.
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