Applied Mechanics and Materials Vols. 672-674

Abstract: The loose coupling structure of Contactless Electrical Power Transfer System (CEPTS) is the main cause of transmission inefficiency. Compensation capacitors were calculated and mounted on both sides of primary and secondary coils which forming the following four compensation topologies: primary secondary series (SS compensation), primary series-secondary parallel (SP compensation), primary parallel-secondary series (PS compensation) and primary secondary parallel (PP compensation). Experiment results show that the transmission efficiency differs according to different compensation topologies. SP structure is the most efficient among these four topologies and the transmission efficiency of SP structure is about 40% higher than that of basic structure without compensation.

Abstract: The paper makes the simulation and analysis to the power harmonic which is produced by the AC drive device of the hot strip mill in the background of the metallurgical industry. Aiming at the line-side effects of AC-AC frequency conversion and AC-DC-AC frequency conversion control system harmonic, the paper makes the MATLAB simulation and analysis in three circumstances, such as the load parameters, the inductance value changes of transformer primary side and secondary side, and adding reactor etc., and defines the functions and value ranges of the line reactor. The simulation results can provide a design basis for the harmonic control and the power supply system when the system uses the variable frequency devices, and then improves the power supply quality of the large drag device.

Abstract: To analyze the influence of distribution network with grid-connected photovoltaic (PV) generation on the power supply reliability, in this paper it firstly regards interconnected PV generation as an equivalent generator with rated capacity as well as the island operation mode of PV to set up a model for reliability calculation and analysis. Based on the network equivalent method, the structure of distribution system with PV is simplified and then the reliability indexes of distribution system are worked out based on Failure Mode and Effects Analysis (FMEA). At last, a comparative calculation between the distribution network with incorporated PV generations and that without PV generations is made. After analyzing a real example, the results suggest that integrating PV power generations reasonably into the distribution network can enhance the reliability of whole distribution system.

Abstract: A dual-loop (inner current loop and outer voltage loop) control scheme for micro electric source inverters in microgrid is improved in this paper. In order to make dual-loop control analysis more accurate, LC filter, SVPWM module equivalent are included in the inverter supplied system model. Based on the fully decoupled dq axis model,the PI controller are used in both inner current loop and outer voltage loop. The inner current loop is designed with engineering algorithm and the outer voltage loop with bode diagram and step response. The simulation results show the validity of the designed control in that the proposed design methodology not only enhances steady state performance of the system, improves the voltage quality but also enables the current limiting.

Abstract: Distributed way of traveling-wave fault location algorithm is a new theory founded in recent years. By installing sensing points in distributed way, the accuracy of fault location result can be clearly improved comparing to traditional methods. First, PSCAD is used to simulate the transmission line model and measure the three-phase current data. Second, by using wavelet transformation and phase to-module transformation, these current data is mathematically processed and modulus maximum is achieved easily. Finally, time difference between the adjacent modulus maximum points is calculated and the location is figured out by using the module time-difference algorithm. The test result shows that the method above is valid and the relative error is rather small.

Abstract: This paper expounds the double closed-loop control configuration which is composed by the AC inner current control loop and the DC outer current loop of the CSR PWM rectifier ,and the functions of the inner current loop and the outer current control loop are pointed out. To improve the control performance ,a current controller whose DC outer current loop is designed by the fuzzy algorithm is used. The DC outer current loop error fuzzy variable E’s membership functions is researched ,and also the Rate of change of the current error fuzzy variable EC and the fuzzy variable Δi which is exported by fuzzy controller. Their influences to the control performance are considered. After the simulation experiments, it shows that the DC outer current loop fuzzy control is feasible and effective. The performance of the outer current control loop can be improved.

Abstract: When calculating the grounding current under DC bias, there are many uncertainties. Then an efficient calculation method based on point estimate method is proposed. This method can make the results more reasonable because it takes into account the uncertainties of input quantity and conditions. This paper will value the grounding resistances as variables, and use the point estimate method for the calculation of the grounding current under DC bias. The results are proved to be more realistic and satisfactory.

Abstract: Electronic current transformers are more suitable for the development of power system compared with traditional electromagnetic current transformers. Rogowski coil current transformer is one of three electric current transformers. According to the measurement principle of Rogowski coils, the equivalent circuit of PCB Rogowski coils is analyzed. By using four PCB Rogowski coils combined, a PCB Rogowski coil current transformer is designed and tested. The results show that the designed PCB Rogowski coil transformer has good linearity and high sensitivity and measurement accuracy and it can meet the requirement of power system.

Abstract: The changes of energy pattern and the development of smart grid technologies bring new challenges to the active power balance under normal conditions, but also bring a more extensive means of regulation. This paper make a study on the classification management method of non-emergency reserve in a regional grid. On the basis of the analysis of the influence factors of non-emergency reserve under the ‘Source-Grid-Load’ interactive condition, the classification rule and dispatching method, the capacity computing methods , counting and monitoring methods have been studied. At last, the economic advantage of the classification management method of non-emergency reserve proposed in this paper is analyzed by an example.

Abstract: On the basis of comparative research on primary frequency regulation (PFR) evaluation index of each grid bureau, a comprehensive evaluation index system of PFR is established, including some specific solution scheme according to problems existing in PFR evaluation index of Central China power grid bureau. The index system ensures a more precise and accurate evaluation of actual PFR process. Meanwhile, accurate data source is provided for correct calculation of PFR index through signals processing of wide area measurement system (WAMS) data.