Advanced Materials Research Vols. 960-961

Abstract: Reliability of measurements received from automatic meter reading (AMR) systems is important. This paper presents method of bad data detection. The method allows to estimate the value of systematical error of each AMR complex in case of sufficient statistical sampling.

Abstract: This paper addresses the problems, connected with implementation of 110-220 kV power transformer structural model for automated equipment functional state assessment system based on test and technical diagnostics data. This article describes the basic construction principles of hybrid neural network using Takagi-Sugeno fuzzy method. The paper also provides the statistical data analysis results for power transformers (of real energy grid part) to define fuzzy neural network criteria (layers).

Abstract: With permanent magnetic actuator monostable circuit breaker as the research object, it gets three different running status signal data, normal circuit breaker closing state , break-brake spring single loss and Institutions unsmooth Through constructing data acquisition platform. The performance of the three methods of feature extraction is compared, short-time Fourier transform, wavelet packet energy entropy and Hilbert huang transform, through fuzzy c-means clustering analysis algorithm. Through the comparative study, it is concluded that adopt wavelet packet transform method to get the best classify performance of time-frequency entropy vector .

Abstract: This paper studies the instantaneous output power characteristics of photovoltaic inverters and its flexible power control strategy under unbalanced grid faults. Then the optimal parameters model of the power control is established with minimum integrated fluctuation amplitude of the active and reactive power as a goal when the constraint of the output current harmonic distortion of photovoltaic inverters is taken into account. Finally, the optimal power control of photovoltaic inverters based on dead-beat current tracking is realized and the feasibility of the proposed control strategy is verified with the power system transient software PSCAD/EMTDC.

Abstract: In order to study the steady-state performance of modular multilevel voltage source converter (MMC-HVDC), a 21-level MMC-HVDC system is modeled by PSCAD/EMTDC software. This system uses the DC voltage and active power controls, which are designed by the fundamental operation principles and mathematical models of MMC-HVDC. By analyzing the steady-state performance of MMC-HVDC, the corresponding simulation waveforms verify the correctness and validity of the simulation model.

Abstract: Photovoltaic systems can not meet the needs in the power grid without the impact, due to its penriodicity, intermittent and randomness, thus the key to solve the core technology of photovoltaic power generation system is important to achieve PV grid-connected. This article explains the two-stage topology system control and modeling of single-phase PV grid-connected: Modeling of DC / DC converter provides basis for maximum power point tracking; DC / AC inverter in grid-connected modeling offer efficient communication basis for grid-connected, it research on the control strategies for DC / DC and DC / AC circuit: that PV grid-connected complete alternating current of unit power factor using the booster circuit and inverter control structure, in order to offer photovoltaic systems flexible grid-connected the foundation.

Abstract: The mathematical model VSC-HVDC system in dq reference frame is derived.For the VSC-HVDC system of transmitting power to passive network ,a constant DC voltage is used in the rectifier-side;a constant AC voltage controller is used in the inverter-side.Digital simulation models are set up by MATLAB/Simulink. Simulation results verify that VSC-HVDC has a independent control of active and passive power,and demonstrates superiority of transmitting active and passive power simultaneously when connecting to passive network.

Abstract: Power generation becomes a main way of using new energy. However, the access of distributed generation(DG) causes the ordinary protection system develop a series of problems. In this paper, the structure of distribution network with DG is introduced firstly.Secondly,it is analysed that the effect that DG brings to distribution network protection, and then a new protection scheme of distribution network with DG is put forward. The segment I, II of direction three-current protection on the line which is at the upstream of DG, and the next line’s segment I, II consists of a simple communication unit. Through the comprehensive judgment of two protections’ action results, fault can be isolated in minimum range quickly and accurately. Finally, the correctness and feasibility of the new protection principle are verified by simulating a 10KV distribution system.

Abstract: To highlight the main factors, only the crowding shaft was taken as elastic component, while the other crowding system parts, such as girth, driving shaft and swing arm were taken as rigid components; the effects of damping were ignored; the dynamical model of excavator’s crowding system was simplified to a two degree of freedom model; mathematical and mechanical models were derived by Lagrange equation method; the locked rotor condition, when the bucket rod was perpendicular to the boom, was used as the calculation condition; the calculated dynamic load coefficient of the crowding system was compared with that in multi degree of freedom model and the result shows: to simplify calculation, it is practicable to replace multi degree of freedom models with two degree of freedom models in the preliminary design stage.

Abstract: In order to study the application of the liquefied natural gas (LNG) on diesel engine, a turbocharged diesel engine was converted into a dual-fuel engine ignited by diesel fuel. The effects of load ratio on fuel economy and emissions of dual-fuel engine were compared and analyzed at engine speed of 1200 r/min, 1600 r/min and 2200 r/min. The experimental results show that, the specific fuel consumption is reduced with the increase of load ratio at different speeds. As the load ratio increases, CO emission of dual-fuel reduces, but it increases slightly at high loads and full load. When the load ratio is less than 40%, HC emission of dual-fuel is reduced significantly with the increase of load, but increases when the load ratio continues to increase, and finally HC emission is stable. When the load ratio is less than 40 %, NOx emission is relatively low, as the load ratio increases, increases sharply, but at high loads and full load, reduces slightly.