Showing papers in "Advanced Technology of Electrical Engineering and Energy in 2014"

Review of energy storage technology for new energy power system

Abstract: This paper reviews the research status of energy storage technology for the new energy power system which contains wind power. Firstly,the great significance of energy storage technology for power system containing a high proportion of wind power is discussed. Secondly,the present research progress of various energy storage technologies are systematically compared. On one hand,the paper described the theory of various energy storage technologies and analyzed the characteristics of energy storage technologies. On the other hand,it also summarized the advantages,problem and application range of various energy storage technologies. Thirdly,it adopted a new method that coordinates a variety of energy storage technologies for new energy power system and combines energy storage technology with large capacity and quick response. Lastly,it pointed out that optimal allocation of energy storage in the new energy power system has become a subject which needs further research.

Cycle efficiency evaluation method of multi-stage RCAES system

Abstract: Due to the uncertainty and anti-peaking nature,integration of large scale renewable energy brings great challenges to the operation and dispatch of power systems. CAES( Compressed Air Energy Storage) system provides new ideas to solve this problem as its characteristics of fast regulating,flexible location and long service life.Especially,RCAES( Regenerative Compressed Air Energy Storage) system is widely concerned as its repurposing of the heat released in the compression process. The efficiency of energy conversion is a key indicator of RCAES system. However,current research mostly focuses on the thermodynamic process and few works has been done on the efficiency analysis of the whole RCAES system. Based on the electrical-mechanical-thermal dynamic process and with measurable parameters,we present an efficiency evaluation method of RCAES system in this paper. A typical RCAES design scheme is studied to illustrate and validate the effectiveness of the proposed method.

Combined membership function and its application on fuzzy evaluation of power quality

Abstract: In the fuzzy evaluation process of the power quality,different membership functions can lead to different results,which affect the credibility of the evaluation. In order to avoid subjectivity of choosing membership function,a combined membership function based on the Variance-covariance optimized combination method is proposed. Firstly,five typical intermediate membership functions are selected. Secondly,weights of each function are calculated by the Variance-covariance optimized combination method,and then a combined membership function of general applicability is constructed according to the weights. Thirdly,the fuzzy evaluation is performed by using this combined membership function. Finally,an application of this combined membership function in the fuzzy evaluation of power quality of a power supply substation shows that this function can improve credibility of the evaluation result.

Study on signal reverse transmission in ICPT system

Abstract: According to the problem of digital signal reverse transmission in the Inductively Coupled Power Transfer( ICPT) system,a new method for signal reverse transmission based on reflected impedance modulation is proposed. This method is implemented to regulate the capacity value of the secondary loop according to the signal transmitted,then monitor the current wave of the primary circuit to demodulate signal. In this paper,how the reflected impedance influence the current is analyzed and approved by the experimental verification.

Operation errors analysis of electric energy metering device and state evaluation method research

Abstract: The operation errors of the electric energy metering device directly affect the accuracy of the trade settlement for both sides of the power supply. So,it is important for state evaluation on the operation of the electric energy metering device. This paper divides the electric energy metering device into four parts: electric energy meter,current transformer,voltage transformer and the secondary loop. The influencing factors on operation errors of each part are summarized. In addition,the influence of power grid operation condition is analyzed and illustrated. Aiming at the shortages of the device test,an new operation state evaluation method is put forward. Based on the operation state of electric energy metering device test,the data of voltage,current,frequency,etc.,can be obtained. Combining with the periodic inspection data,and taking into account influence of the actual power grid operation environment on the accuracy and reliability of the energy metering device,the comprehensive evaluation can be made. A number of indicators from all sides and the corresponding weights are chosen and formulated to establish the state evaluation standard. According to the state evaluation results,different inspection strategies are proposed.

Exploration of switching characteristics of SiC-based power devices

Abstract: Compared with silicon devices,SiC-based power devices feature high voltage capability with low switching losses and high operating temperature. The differences of switching characteristics between SiC-based devices and Si-based devices are analyzed. Then,a buck converter test bench is built,and the switching characteristics of SiC-based devices and Si-based devices are tested and compared. Experimental results verify the correctness of the above analysis,and provide design guidelines for the proper selection and application of SiC-based power devices.

Planning of electric vehicle charging stations considering users' convenience

Abstract: The main function of electric vehicle charging stations is to provide users with a convenient charging service. In order to solve this problem,a planning method of electric vehicle charging stations considering the users' convenience is proposed in this paper. The planning area is divided into several grid zones considering the limits of the road network and the charging station's capacity. The consumption of users driving to the charging stations is used as the objective function and Genetic Algorithm( GA) is applied to solve the optimal problem of howto choose the best location of the charging station in each zone. With repeated calculation and adjustment of the coverage of grid zones and sites of charging stations,the reasonable planning scheme of electric vehicle charging stations in the study area is obtained. Finally the feasibility of the model and the method proposed in this paper are validated by a practical example.

Model predictive direct torque control of induction motors

Abstract: This paper presents a novel model predictive direct torque control( MPDTC) methodology for induction motors to remedy the drawback with large pulsating torque and stator flux output of the traditional direct torque control( DTC). On the basis of the mathematical model of an inverter driving induction motor,a discrete-time predictive model has been developed. By utilizing the online optimization algorithm,a cost function evaluates the square sum of torque and stator flux magnitude errors for each switching state in a two-level inverter. The voltage vector with the lowest error is then selected to be applied on inverter. The performance of the presented MPDTC scheme is compared with the traditional DTC. Simulation results show that the presented MPDTC scheme can reduce the flux and torque ripple effectively and lower the current harmonic distortion while inherit the fast transient response from the traditional DTC.

Heat dissipating performance research of direct-cooling IGBT module

Abstract: The temperature of the components of the power electronic equipment is one of the key factors for its performance and reliability. For the heat dissipation of the IGBT power module,one of the most popular research focus is using the direct cooling technology to integrate the radiating fins into the copper substrate of the power module in the design phase. This structure ensures the installation of the IGBT module doesn't need to use the thermal interface materials to connect the module copper substrate and the cooling plate any longer,thus makes the entire thermal resistance of the module to be reduced significantly. In this paper,we tested the heat dissipating performance of a self-developed 2 in 1 direct cooling IGBT module and contrasted with the traditional indirect cooling module. The experiment results show that entire thermal resistance of the direct cooling module is reduced up to 33%, meanwhile the temperature field distribution is more uniform. In this paper,we also established a simulation model for the direct cooling power module,which has a satisfied consistency with the test results,therefore we can use the model to research the heat dissipating performance of the direct cooling module deeply.

Design and initial implementation of smart electric appliance network

Abstract: Development of intelligent electricity is one of the important aspects of building the smart grid. Based on previous concepts of intelligent electricity,smart home and automatic demand response,this paper presents the definition of the smart electric appliance network. The smart electric appliance network is to form a network combined of the user side's all kinds of electrical appliances by the energy information gateway. It is aimed at building a network based on the Internet of Things,the Internet and the smart grid technology with the massive electricity users.The smart electricity network can not only help power consumers save energy and provide them with intelligent,friendly,personalized and differentiated services,but can also guide power consumers to participate in the collabo-rative demand response in a flexible interactive way to help achieve the optimal operation of the power grid. The hardware part of the smart electric appliance network consists of the smart sockets,the smart infrared controllers,the energy information gateways,the cloud servers,the mobile devices and other components. The software part of the smart electric appliance network is developed on the Android platform. Currently,the smart electric appliance network has been put into trial operation in Tsinghua ZiJing dormitory,and the results show that the proposed method is feasible and effective.

Dual-redundancy fault tolerant permanent magnet motor control system

Abstract: In this paper,compared with traditional fault-tolerant system and traditional redundancy system,a control strategy of dual redundant motor system applied in fault tolerant permanent magnet motor with dual-winding is analyzed. A fault-tolerant permanent magnet machine of centralized winding is introduced,which has the property of physical insulation,magnetic flux and fault insulation. And vector control is adapted in this system. The Matlab simulation model is established which contains the motor model,SVPWM,speed controller,three-phase full-bridge inverter and current controller. The simulation results reveal that the constant speed mode and constant torque mode can be switched in the dual-redundancy control system. Experiment results show that the speed is constant when the load torque changes under constant speed mode,and the torque is constant when the speed changes under constant torque mode. Both the simulation and experiment results show that fault-tolerance control of the system is achieved when open-circuit fault occurs while maintaining the power and speed unchanged.

Power system load forecasting based on quantum behavior particle swarm optimization algorithm-chaotic neural network

Abstract: This paper presents a combinative method of power system load forecasting based on quantum behavior particle swarm optimization and chaotic neural network. Based on the quantum behavioral characteristics of the particle swarm,and using the identical particle system to update the particle's position,the shortcomings of the traditional particle swarm optimization,such as low accuracy,dissipation easy,and slow convergence rate can be avoided. Using particle swarm optimization algorithm to optimize the chaotic neural network weights and thresholds,we can overcome the shortcomings that it is difficult and slow to determine the parameters of chaotic neural network. Using the weights and thresholds,through the improved particle swarm optimization algorithm-chaotic neural network model,the corresponding time load value of the predicting date can be obtained. Finally,through the practical application,it can be proved that the method has higher prediction accuracy and better accuracy,with some practical value.

Material compatibility research of evaporative cooling technology applied to large electronic equipment cooling

Abstract: With the development of the electronics and information technology,the heat dissipation problem has become the development bottleneck of electronic equipment,especially large-scale high-density electronic devices. Evaporative cooling technology of the Institute of Electrical Engineering,Chinese Academy of Sciences,utilizing phase change latent of cooling medium,cooling capacity has the great advantage than traditional air-cooled cooling technology. When it is applied to large electronic equipment cooling,material compatibility is an important problem,which requires the first study. This paper describes materials compatibility experimental research and analysis between cooling media and electronic equipment. And the experimental results provide cooling media screening guidance for electronic equipment,which provide important technical support for evaporative cooling technology applying to large-scale electronic equipment,in future.

Charging power demand of electric taxi modeling and influence factors analysis

Abstract: With the accelerated pace of the electric taxi,the growing charging power demand will have certain influence on the grid. As a precondition of safety operation for power grid,studies on electric taxies' charging load model is also the theoretical basis of electric taxi charging. Firstly,based on the analysis of Poisson process,random sequence of charging start time is expressed; then,the calculation model of electric taxi charging serving time is set up. Finally,charging power demand model of electric taxi is build. According to this model,electric taxi charging power curve within a day was calculated and presented with the operating data in a demonstration electric taxi charging station. The results of the simulation examples show that the modeling method of the charging power demand model is effective.

Researches on electro-thermal model for junction temperature prediction in IGBT modules

Abstract: With the development of IGBT module and its increase of power level and density,system failures caused by junction temperature problem due to power loss are more and more severe. Deep researches on device and heatsink system can contribute to power device package design,device selection,system layout and inverter stable operation. This paper models and extracts the transient thermal impedance through FEM( Finite Element Method),with simulation results in line with manufacturer's datasheet. It also verifies the thermal impedance curve's universality and sets up electro-thermal model based on thermal characteristic RC equivalent network, which can be used for dynamic junction temperature prediction.

Streamer corona discharge simulations of coaxial gap in SF_6/N_2 gas mixtures

Abstract: The use of gas-insulated transmission line as an effective supplement for cables and overhead lines will play an important role in power development. The fluid method is used to analyze streamer corona discharge mechanism in coaxial gap in SF6/N2 gas mixtures which is the future alternative for pure SF6. The finite element-flux corrected transport technique( FEM-FCT) based on the unstructured mesh is used to solve continuity equations for electrons,positive ions,and negative ions. The finite element method( FEM) is used to solve Poisson electric field distortion caused by space charge. 2-dimensional simulations of streamer corona discharge process in SF6/N2 gas mixtures between coaxial electrodes are achieved. The results show that electric field is balanced by streamer corona,and streamer corona will disappear after a period of time with low applied voltage. Less time is needed to form streamer corona in SF6 than 50%-50% SF6/N2 gas mixtures. The effect of photoionization is stronger than photoemission. \

Novel push-pull forward converter for high reliability and high input voltage applications

Abstract: A novel push-pull forward converter is proposed for high input voltage and high reliability applications. The converter is constructed by series connecting and coupling two forward cells via an integrated magnetizing core. Switches' voltage stress of this converter is clamped at input voltage and the leakage energy and magnetizing energy of the transformer are recycled. In addition,high reliability can be guaranteed since no direct-short path existed in the converter. All these features make the proposed PPFC suitable for high-reliability,high-input voltage,and high power density power conversion applications. Operation principle and detailed analysis of the proposed converter are given and verified with experimental results.

Experiment on GaAs PCSS's on-resistance with solid-state planar Blumlein line

Abstract: In order to develop the compact pulse power system,the experiment on GaAs photoconductive semiconductor switch( PCSS) 's on-resistance has been studied. With 2mm-thick solid-state planar Blumlein line,GaAs PCSS is triggered with the high power pulse laser diode. GaAs PCSS turned-on the lock-on mode under the pulsed bias voltage. A 22. 3kV high voltage pulse was obtained on load through Blumlein line,which satisfied the design of compact pulse power system. The PCSS's on-resistance of 4. 1Ω was calculated according to bias voltage,output voltage and impedance of Blumlein line. Moreover,the relationship between GaAs PCSS's on-resistance and bias voltage,laser energy were studied under the lock-on mode of PCSS.

Study of hybrid compensation scheme based on TCSC damping sub-synchronous oscillation

Abstract: A novel hybrid thyristor controlled series compensation( HTCSC) scheme for damping the sub-synchronous oscillation is studied. In HTCSC structure,TCSC device is connected to single phase and the other two phases use only the fixed compensation capacitor. Under basic power frequency,the three phase impedance is equal;while under sub-synchronous frequency,impedance of three phase is unequal,thus the three-phase current is imbalance,which can weaken the coupling between generator and electrical system and inhibit SSO to a certain extent. Compared with three-phase TCSC,the new structure reduces number of thyristor by 2 /3,and lowers the device cost and control difficulty. Synchronous voltage reversal( SVR) method is used as the control strategy and a supplementary active damping controller is designed. The simulation result shows that with the active damping controller based on SVR,HTCSC can effectively suppress the sub-synchronous oscillation caused by unreasonable line compensation degree. Moreover,the steady-state value of line voltage unbalanced rate under HTCSC scheme after a short-circuit fault can meet the requirements of national standard.

Study on harmonic distortion of voltage signal acquisition method based on compressed sensing theory

Abstract: In view of the quick changing of power quality signal and large amount of data that need to be collected,we discussed application of compressed sensing theory to power quality signal acquisition in this paper.Also we demonstrated a new algorithm of constructing the rotation matrix according to the specific requirements for power quality signal,which we called weighted observation matrix.Regulating the weight could lead to reconstruct accuracy change at different parts of signal independently.By adjusting the weight of different frequencies of signal according to signal characteristics known in advance and specific requirement to the measurement,this new algorithm has the ability to get more accurate reconstruction results of signal under higher compression ratio condition.The performance of this algorithm was evaluated under different compression ratios.Compared with classical observation matrix such as Gaussian random matrix and the traditional rotation matrix,our method demonstrated higher compression ratio,higher reconstruction accuracy and better robustness.