Advanced Materials Research Vols. 732-733

Abstract: Whether the bed temperature of circulating fluidized bed boiler (CFBB) is stable or not affects the efficiency of the entire unit. According to the characteristics of an uncertain system with large delay, large inertia and time-varying of the bed temperature system, this paper proposed an adaptive dynamic matrix control (DMC) algorithm based on the real-time error correction. The algorithm can make the dynamic matrix controller more accurately, more flexibly and more applicably on reflecting system changes by revising the errors during the feedback regulating. The simulation results show that the control algorithm is of good adaptability and robustness and satisfactory control effect in the bed temperature system can be achieved.

Abstract: Based on power system stabilizer (PSS) and the damping controller of flexible AC transmission system (FACTS),a problem of optimal design is researched by the example of static var compensator (SVC). Minimum damp ratio of system electromechanical oscillation modes eigenvalue in the weak damping operation condition is selected as the object function. Parameters of damping controllers are optimized by the algorithm which is combined by genetic algorithm (GA) and back propagation (BP) neural network based on adaboost (Ada-BP). Simulation shows the optimized damping controllers can restrain the low frequency oscillation in multi-operating conditions of system. The algorithm provides an effective solution for optimization calculations which calls the complicated calculations.

Abstract: This paper presents a development of measuring device and software for 3-phase measurement of electric power quantities according to IEEE Std. 1459-2010. Blackman-Harris windowed FFT algorithm is used for the harmonic analysis to reduce the errors from leakage problems. Result verification with a technical paper has been made. Actual implementation with an adjustable speed drive at a laboratory has been carried out and crosschecked with a commercial power quality meter.

Abstract: The dynamic process analysis of the generator self-excitation was proposed in this paper, considering the effect of the active power load in the isolated system. Firstly, generator self-excitation generation mechanism was introduced in this paper. Then, with a simple analysis system, two situations, which include the undercompensation system and the over compensation system, are discussed to analyze the dynamic process of the generator self-excitation phenomenon. Analysis results show that when there is the active power load in the isolated power system, the rotate speed of the generator in this system can be limited after the load rejection faults occurrence in system. Therefore, the overvoltage of the system caused by self-excitation can be limited obviously. Hence, the equipment in the system can be protected.

Abstract: This article presents an energy information model of a power supply system that is necessary for formation and functioning of the new system of technical policy in the field of distribution networks. The article deals with the key issues, methods and functions related to formation of the energy information model.

Abstract: Power system small signal stability concerns the ability of the power system to maintain stability subject to small disturbances. The analysis of small signal stability often has to deal with high-order system matrix due to the large number of generating units so that it is not easy to calculate and analyze the original system matrix and the whole set of eigenvalues. In this paper a new approach is proposed to take advantage of the specific feature of the parallel structure of artificial neural network for calculating the most critical eigenvalue or all eigenvalues of the unstable oscillation mode. The developed algorithm is tested on a sample power system to validate the feasibility of the proposed method for the calculation of the critical eigenvalue.

Abstract: Battery swap stations for electric vehicles are getting more and more attention, but there is still no comprehensive protection scheme in distribution system when battery swap stations discharging to the grid. The present paper presents the structural topology and the corresponding detail control model of charge and discharge machines in the battery swap station. Then with an example of a 10kV distribution system composed by a battery swap station, the fault features of the battery swap stations outlet and the grid are simulated when the battery swap station works in different state and various short circuit faults occur in the grid through PSCAD/EMTDC. Based on the above, the impact of the battery swap stations operating status on the grids fault features is analyzed in detail. In the end, the outcomes of the paper can provide evidence for improving such distribution grids protection.

Abstract: A new continuation power flow method based on local geometric parameterization technique is proposed for voltage stability analysis of AC/DC hybrid power system. By means of the alternating iteration method as the AC/DC power flow algorithm, the proposed method takes the coupling relationship between AC and DC systems into account to modify Jacobian matrix of AC system. Constraints of variables in DC system are also considered, as well as the adjustment of converter transformers tap position and the conversion of converters control modes. Based on the predictor-corrector method, this paper adopts the geometric corrector, and changes the direction of convergence effectively. According to different operation modes of AC/DC system, accurate voltage stability limit and the entire PV curve can be acquired. Simulation results of IEEE test systems are used to show the validity of the proposed algorithm.

Abstract: This paper proposes a novel Internal Model Control (IMC) method for the control of superheater steam temperature. The IMC is known for good robustness including handling of systems with time delays. While Iterative Learning Control (ILC) is a strategy for dealing with periodic disturbances. By using a combination of IMC and ILC, their individual advantages are used to increase the robustness against modeling uncertainties and handling time as well as decreasing the influence of the periodic disturbances affecting the superheater steam. Some simulation examples are shown to illustrate performance improvements that can be achieved by the new method over the conventional IMC and PID methods. Key Words: Superheater Steam Temperature; Internal Model Control; Iterative Learning Control

Abstract: In allusion to the discrepancies of the equivalent generator's equivalent inertia based on mechanical inertia time constant and that of the power system under practical operations, the concept of effective inertia is proposed. By analyzing a two-generator system, the main factors influencing the dominant mode damping ratio of inter-area oscillation, besides the supplementary damping control, are analyzed as the three: effective inertia, load level and network structure. When the former two are constant, the crucial factor for dynamic stability reducing in terms of operation mode change can be ascribed to the effective inertia competition. Practical calculation of Gansu power grid simulation is conducted and the result of argument is verified.