Applied Mechanics and Materials Vol. 740

Abstract: In order to improve the development using FPGA solar panels generating speed, through the study on the solar panel maximum power output perturbation method (MPPT) how to develop and how to improve the development efficiency were studied. This algorithm through MATLAB Simulink simulation is confirmed, then use generator to simulate the algorithm, and the algorithm is downloaded into the FPGA, the hardware co_simulation, design of MPPT circuit will be in accordance with the circuit parameters of the modified. Through the hardware circuit operating results, it is proved that the algorithm design of circuit is correct and meet the design requirements, also demonstrate the utility of using generator hardware co_simulation method for the development of FPGA. The development method can improve the design speed, shorten the reliability of control, the development cycle and reduce development costs, achieve a fully compatible and replace physical circuit.

Abstract: This paper mainly discusses the tower models in lightning overvoltage calculation, especially analysis the lossless and lossy models. Build the muti-wave impedance model of the most commonly used towers, which are portal tower, glass tower, cat head tower and strain tower in accordance with the reality. The simulation shows that muti-wave impedance model has a higher lightning overvoltage than simple model under the same condition. This is because the simple model ignores the influence of resistance and inductance, so the more accurate the model is, the more effective the protection will be.

Abstract: This paper proposes an improved L index which is adapted to analyze the voltage stability of power system with the ZIP loads. First it introduces derivation of the traditional L index. Then, it analyzes the differences between ZIP loads and PQ loads and then proposes an improved version of L index based on the derivation. Furthermore, the proposed improved index is used to analyze the voltage stability under different operation conditions of the power system with ZIP loads. The simulations show the effectiveness of the proposed improved L index.

Abstract: UHV-DC transmission system presents certain adverse reactive characteristics to its receiving-end grid. Based on the approach of P-V curve and V-Q curve, this paper presents a method of voltage stability analysis for the receiving-end grid of UHV-DC transmission system, which gives its available transmission capacity (ATC), voltage limit and reactive power margin, with the consideration of the normal, N-1 and N-2 operation situations and the situation of the commutation failure. Different with traditional ATC analysis, the characteristics of UHV-DC transmission system is included here. With the real UHV-DC project of ±800kV HaZheng in China, the effectiveness and efficiency of the proposed mothed are verified.

Abstract: As large-scale wind farms are connected to the grid, a single type compensator cannot meet the demand. STATCOM has ability of rapid reaction and harmonics suppression, SVC can compensate large capacity reactive power. In this study, a compensator, which is able to coordinate Static Var System (SVS) with STATCOM is proposed. Large-scale wind power integration is simulated respectively with the compensator of STATCOM alone and coordinated compensator of SVS and STATCOM by DIgSILENT/Powerfactory15.0. Simulations results clearly verify that the compensator of SVS and STATCOM improves transient stability and performance of the photovoltaic systems.

Abstract: The particle swarm optimization (PSO) algorithm as a stochastic search algorithm for solving reactive power optimization problem. The PSO algorithm converges too fast, easy access to local convergence, leading to convergence accuracy is not high, to study the particle swarm algorithm improvements. The establishment of a comprehensive consideration of the practical constraints and reactive power regulation means no power optimization mathematical model, a method using improved particle swarm algorithm for reactive power optimization problem, the algorithm weighting coefficients and inactive particles are two aspects to improve. Meanwhile segmented approach to particle swarm algorithm improved effectively address the shortcomings evolution into local optimum and search accuracy is poor, in order to determine the optimal reactive power optimization program.

Abstract: Corona cage is an important supplementary method for studying corona phenomenon, which is an indispensable for designing transmission lines. In this paper, the bundle conductors are chosen as research objects and the charge simulation method (CSM) is applied to build calculation model, using line electric charges to simulate bundle conductors, walls of corona cage and space charges. The method of tight coupling of electric field and potential is first introduced in corona processing, in which the Kaptzov hypothesis is directly applied to establish equations of charge - electric field and charge - electric potential. In addition, in order to analyze the capacitance value variation of corona cage when corona onset occurs, the emission, migration and composite process of space charges is simulated. Finally, 4, 8, 12 conductors in corona cage under different meteorological conditions are modeled, and the research results are analyzed. This research can also be applied to model corona cage and high voltage transmission lines at different voltage levels and different bundles under different meteorological conditions.

Abstract: As for transient stability simulation, Chinese researchers often use PSASP (Power System Analysis Software Package) as an auxiliary analysis tool while PSS/E (Power System Simulator for Engineering) is commonly used overseas. The correspondence of models contained in these two software packages will be discussed in this paper. Correspondent model parameters can be converted mutually based on the inner link of PSASP and PSS/E. Similar testing results of one standard IEEE case show that this data conversion method is primarily workable.

Abstract: Optimal algorithm is an important factor for identifying the dynamic load model parameters accurately which with the nonlinear characteristic. The paper adopts the improved genetic algorithm with optimal reservation strategy (OGA) at the beginning and finds that the problem of convergent to local optimal solution is still exist. Considering the Simulated Annealing algorithm (SA) has good performance in respect of local searching characteristic which can prevent convergence from local optimal, so the hybrid algorithm combined with SA algorithm and GA algorithm (GASA) is proposed in this paper. Case studies showed it can improve the accuracy of parameter identification and reduce the P Q fitting errors .The efficiencies of identifying substation load model based on the PMU measure data is proved as well.

Abstract: Y-type insulator string has advantages of external insulation and reduction of corridor width. This paper establishes a 3D finite element model of Y-type composite insulator string of 1000 kV AC double-circuit transmission line, including tower, insulator, grading rings, phase conductors and other hardware fittings, the model is used to calculate electric field distribution of composite insulator and grading ring. Then the parameters of grading ring are optimized based on the electric field results. According to the results, the optimum parameters of the racetrack grading ring are R=700 mm, r=120 mm, H=200 mm. The results can give a reference for design of UHV AC Y-type insulator string.