SUN Kai¹, ZUO Feng², LU Xiao-nan¹, YAN Gan-gui²

(1.State Key Lab of Power Systems, Department of Electrical Engineering, Tsinghua University, Beijing 100084, China; 2. Northeast Dianli University, Jilin 132012, China)

Abstract: In order to restrain the negative impact of voltage sags of utility grid on micro-grids, a dynamic voltage support method based on grid-connected inverters is proposed in this paper. The controller and circuit are developed to realize the principle that a voltage drop on the inductor is generated when the reactive power flows through it. Once the voltage sag of utility grid occurs, an arbitrary reactive power is injected into the grid by grid-connected inverters, which generates a voltage drop on the decoupled inductor to compensate the grid voltage sag. This can maintain the local bus voltage of micro-grids. According to the magnitudes of voltage sags, several actions of the grid-connected inverters are designed and implemented to generate reactive power and maintain local bus voltage, which ensures the normal operation of loads. Design considerations of the controller are discussed in detail. Simulations by using MATLAB/Simulink are conducted, which demonstrate the feasibility and effectiveness of the proposed method. 

Key words: microgrid; grid-connection; local voltage support; reactive power; decoupled inductor

 

Study on single-phase photovoltaic grid-connected inverter system

LI Lian-bing，WANG Tong-guang，SUN He-xu

（School of Control，Hebei University of Technology，Tianjin 300130，China）

Abstract：The paper introduces the software and hardware of single phase grid connected inverter control circuit, comprising of the single-phase photovoltaic system topological structure and maximum power point tracking function, as well as anti-islanding effect function. The grid-connected inverter output control for voltage source system guarantees the input DC voltage is adjustable as quick as possible, and implements photovoltaic array MPPT control. The MPPT uses a combined control algorithm of fixed parameter method and perturbation and observation method. Islanding detection method is based on non characteristic harmonic impedance of power system active passive combined detection method. And on this basis, using TMS320F2406 and IPM as the hardware core, a 5kW practical product prototype is developed. Test results show that the proposed control scheme has good dynamic and steady state performance. Comparing the LCL filter with the L filter, we found that LCL filter is better.

Key words：inverter；photovoltaic grid connected；maximum power point tracking；anti islanding

 

YANG Yu-gang, WU Jian-hong

（Electrical Control Engineering Institute ,Liaoning Technical University, Huludao 125105, China）

Abstract: To improve the electrical characteristics (such as the output power, low output voltage ripple) of essential safety power source, this article introduces the interleaving magnetic integrated theory for the essential safe source and proposes the concept of the equivalent electrical inductance and essence safety inductance, through increasing electrical inductance and reducing essence safety inductance to make the converter to improve the electrical characteristics, so as to meet the internal intrinsic safety characteristics. Taking the two-phase interleaving magnetic integrated boost converter for example, by analyzing the internal intrinsic safety characteristics of the converter, the internal intrinsic safety criterion of the converter can be obtained. And by comparing with the conventional single-channel boost converter when two types of converter meet the internal intrinsic safety characteristics, it can prove that the interleaving magnetic boost converter can effectively improve the electrical characteristics. Finally, simulation and experiment confirm the correctness of theoretical analysis.

Key words: output power; interleaving magnetic integration; equivalent electrical inductance; equivalent essence safety inductance; inner-intrinsic safety

 

ZHU Shi-you¹, RUAN Bai-shui², QUAN Heng-li², ZHANG Gang³

(1. Guangzhou Metro, Guangzhou 510380, China;

2. School of Electrical Engineering, Beijing Jiaotong University, Beijing 100044, China;

3. Beijing Qiansiyu Electric Co., Ltd., Beijing 100082, China)

Abstract: Due to the low power factor of traction power supply system for urban rail transit in rush hours, a reactive power compensation scheme based on energy-feedback traction power supply system was proposed in this paper. The causes of the low power factor of power supply system were given, as well as the structure and working principle of the energy-feedback traction power supply equipment. A reactive power compensation strategy was proposed according to the distribution of reactive power. At last, a prototype rated 2MW was built and tested, and demonstrates that the reactive power compensation strategy proposed is feasible.

Key words: urban rail transit; energy-fed traction power supply equipment; reactive power compensation

 

LIN Wei-ming, HONG Cui, HUANG Chao, ZHANG Qiang

(College of Electrical Engineering and Automation, Fuzhou University, Fuzhou 350108, China)

Abstract: Traditional boost Power Factor Correction（PFC） suffers from the high conduction loss in the input rectifier-bridge. Higher efficiency can be achieved by using the bridgeless boost topology. This new circuit has issues such as voltage sensing, current sensing and EMI noise. In this paper, improved one cycle control technique is analyzed and used to solve the issues of the voltage sensing and peak current sensing. A prototype was set up to verify the theoretical analysis.

Key words: efficiency; THD; peak current sampling; improved one cycle control; bridgeless PFC

 

XUE Shang-qing, CAI Jin-ding，LIU Li-jun

(College of Electrical Engineering & Automation, Fuzhou University, Fuzhou 350108, China)

Abstract: Reactive power capacity of wind farm with doubly fed induction generator(DFIG) is limited under voltage fluctuation or grid fault in the fact that wind farm is usually operated in unity power factor using reactive power compensator to meet reactive power demand of wind farm. Aiming at the problem, a controller is proposed for the coordinated voltage and reactive power control between wind farm and static synchronous compensator (STATCOM). Action dependent heuristic dynamic programming is used to design the controller, which contains action network and critic network. The ADHDP controller not only fully utilizes the capacity of STATCOM, but also reduces the level of voltage sags during grid fault and keeps wind farm operate in constant power factor. The controller also acts as a supplementary damping controller, and therefore, improves voltage oscillation damping after grid faults. Simulation results verify the effectiveness of the proposed controller.

Key words: DFIG; wind farm; STATCOM; ADHDP; coordinated control; supplementary damping

 

ZHANG Qiang¹，REN Xiao-yong¹，CHEN Qian-hong¹，YU Suo-ping²

（1. Nanjing University of Aeronautics & Astronautics, Nanjing 210016，China；

2. Leader Electronics Co. ，Ltd.，Zhenjiang 212000，China)

Abstract: The MPPT based on Fibonacci numbers has some advantages: large searching range, not affected by environment, no initial value problem, etc. This paper introduces the basic principle and the software realization of this method, establishes solar battery mathematical model based on graphic fitting method, and simulates it by Simulink combined with VB in order to realize the real time observation for the internal parameter in each optimizing step. The result shows that this simulation can be very intuitive to see each step of Fibonacci searching method, and verifies the accuracy of the method. At the same time, it puts forward that the method can reselect the condition of convergence, in order to improve the efficiency of the method. In the experiment, Boost circuit is used as main circuit, with using dspic33f502 chip to program in the MAPLAB platform, and to research the MPPT method with a piece of 250W solar battery. The experimental result verifies the MPPT based on Fibonacci numbers, and also verifies the accuracy of the simulation and feasibility to reselect the condition of convergence.

Key words: MPPT method based on Fibonacci numbers；Simulink combined with VB；simulation and experiment

 

GUO Xu-dong¹, GE Bao-ming¹, BI Da-qiang², YANG Xin-yu³

(1. School of Electrical Engineering, Beijing Jiaotong University, Beijing 100044, China;

2. State Key Lab of Power System, Dept. of Elec. Eng., Tsinghua University, Beijing 100084, China; 3. Electrical Engineering and Renewable Energy School, Three Gorges University, Yichang 443002, China）

Abstract: Wind farms with vanadium battery energy storage system are approved and welcomed. Against the phenomenon of unreasonable current distribution when vanadium batteries are directly paralleled，a control strategy of parallel vanadium battery based on the state of charge (SOC) is proposed. The current control formula is given in this paper. Vanadium batteries are paralleled to adjust the power grid at the exit of wind farms by bidirectional DC/DC converter. A wind farm model with vanadium battery energy storage system is simulated on MATLAB/Simulink. The simulation results show that this system can adjust the power grid of wind farms, and achieve the goal that the charging and discharging of vanadium batteries are completed according to their SOC, so as to avoid the overcharge or over-discharge successfully. Due to the control of current of vanadium battery, vanadium batteries' working condition has been improved. The effectiveness of the proposed method can be verified well.

Key words: vanadium battery; state of charge; parallel operation; bidirectional DC/DC converter; wind farm

 

FANG Ming-jie, WANG Qun-jing

（College of Electrical Engineering and Automation, Anhui University, Hefei 230601, China）

Abstract: Based on the analysis of main factors SOC estimation, strong points and disadvantages of traditional SOC algorithms, a new improved Ah counting approach to accurately predict the state of battery is described in this paper. It corrects the major factors affecting the value of SOC. The algorithm adopts a combination battery model based on simple electrochemical model and Extended Karlman Filter (EKF). Comparision result indicates that it keeps an excellent precision during estimation process of SOC.

Key words: SOC; Ah counting approach; battery model; extended Karlman filter

 

SI Wen-rong，HE Lin, JIN Heng, FU Chen-zhao，HUANG Hua

(Electric Power Research Institute. SMEPC, Shanghai 200437, China)

Abstract: To validate a novel voltage-divider based on the capacitive voltage transformer (CVT) to measure overvoltage waveshape for power system, an element C3 in series connection with high-voltage capacitance C1 and media-voltage capacitance C2 as the low voltage part of sensor (LVPS) is used. A CVT of 500kV level provided by Nissin Electric Wuxi CO., LTD was modified within a element C3 of 54µF in series connection. Lots of tests with ac simulation overvoltage, switch impulse and lightning impulse are done respectively to the modified CVT. Voltage waveshapes from the element C3 with digital sampling are analyzed in both time and frequency domains, and the stabilization of the voltage division ratio is also verified. The results of tests and data analysis show that the voltage waveshapes from the element C3 developed in series connection within CVT have a good characteristic with stable waveshape parameters, no overshoot and oscillation, and the relative deviation is lower than 1%. It is feasible to be used in overvoltage waveshape measurements of power system with ultra-high voltage level.

Key words : CVT; low-voltage capacitance; overvoltage measurement; testing research

 

LEI Xiao¹，WANG Hua-wei¹，ZENG Nan-chao¹，YAN Chao²，XIE Guo-ping¹，LI Xin-nian¹，WU Nan³

(1.China Electric Power Research Institute，Beijing 100192，China；　　　　　　　　　　  　　　　　 2.Patent Examination Cooperation Center of the Patent Office，SIPO，Beijing 100190，China；　　　　 3.China BCEL International Engineering Co.,Ltd, Beijing 100026，China)

Abstract：A hybrid multi-terminal HVDC system consisting of five LCC convertor stations and one VSC station is designed．This configuration can exploit the advantages both of LCC and VSC on different voltage levels to the full，and can extend the range of MTDC．A monopole model is built based on EMTDC/PSCAD，and the stable operation and transient faulty process of parallel multi-terminal HVDC system are studied．The DC power balance controller is worked out to achieve power cooperative control between converter stations．The control and protection coordinative sequences for emergency stop of one station is put forward，and simulation results prove the practicability of this configuration and the efficiency of the strategy．

Key words：hybrid-MTDC；ultra-HVDC；cooperative control；VSC

 

Method for test of FFT window width of voltage harmonic in power quality analyzers

CAI Wei¹, HE Wei², ZHANG Hong-chuan¹,WANG Jian-wei¹

(1. North China Electric Power Research Institute, Beijing 100045, China;

2. Xinjiang Xinneng Information and Communication Co., Ltd., Urumqi 830000, China)

Abstract: The length of spectrum analysis test about harmonic analysis in power quality analyzer has been studied. The method is in accordance with the harmonic measurement request of standard and the harmonic analysis theory. The core is to test the frequency resolution which can be reacted from the output values. We need to detect the harmonic subgroup measurement according to the grouping theory. And we also check the weighting form which can realize by the different spectral leakage using rectangular weighting and others. After knowing these we can know the window width. The correctness of this method and the viability of this solution have been verified by many test experiments.

Key words: harmonic measurement; FFT window width; spectral leakage ; window function; power quality analyzer

 

Effects of thermostatically controlled load on low-frequency oscillations in power systems 

XU Chang-hong, LI Pei-qiang, LI Xin-ran, XU Zhen-hua, PAN Yuan

(College of Electrical and Information Engineering, Hunan University, Changsha 410082, China)

Abstract: Load model plays an important role in the power system stability analysis and digital simulation. In the composite load model there is a load which is controlled by thermostat controller, such as industrial heating, electric water heater and electric space heater. With the proportion of the thermostatically controlled load increasing in the composite load, the influence to the power system small disturbance stability is more significant. For this reason research object of this paper is the thermostatically controlled load. The load model which based on the equation of the thermal transients due to the thermostat operation was built. Based on the power system analysis toolbox (PSAT) in MATLAB, a typical example of a 4-generator 2-area interconnected power system is given. The impact of the parameters of this load on power system’s low-frequency oscillations was discussed and some valuable conclusions are drawn.

Key words: thermostatically controlled load; small disturbance stability analysis; low-frequency oscillations; PSAT

 

SHAO Zhen-guo¹，WU Dan-yue^{2, 3}，ZHANG Yan¹

(1. College of Electrical Engineering and Automation, Fuzhou University, Fuzhou 350108, China;

2. Electric Power Research Institute of Fujian Electric Power Company Limited, Fuzhou 350007, China; 3. State Grid Power Quality Analysis Laboratory, Fuzhou 350007, China)

Abstract: Voltage flicker measured at the point of common coupling is usually caused by more than one flicker source. It is insufficient for the main source determination, not to mention the contribution distribution. The method of distributing the contribution to flicker at PCC among the interference loads and supplier in distribution system is proposed in this paper. First the voltage fluctuation of PCC is divided into components resulting from customers and supplier connected to PCC with variant impedance model used. Then the instantaneous perceptibility and short-time flicker severity according to the fluctuation components are respectively computed. The short-time flicker severity indicates the potential flicker severity of customers or supplier. And the percent of instantaneous perceptibility to total of them indicates the corresponding flicker contribution. A simple 10kV distribution system has been simulated with PSCAD to verify the validity of the proposed method.

Key words: contribution distribution; voltage flicker; voltage fluctuation; power quality

 

MAO Peng¹, LI Ying², LI Jian³, CHEN Ying², SHUAI Ling-ling¹

(1. Jiangxi Electric Power Company Extra-high Voltage Sub-company, Nanchang 330029, China;

2. State Key Lab of Power Systems, Dept. of Elec. Eng., Tsinghua University, Beijing 100084, China; 3. Jiangxi Electric Power Information and Communication Center, Nanchang 330077, China)

Abstract: By analyzing the power system data hierarchy, the role and function of CIM model in power data hierarchy is stated, and the concept of data service interface is appended to CIM model. Besides, the specific conformance requirement of CIM data is investigated. Based on conformance test theory of OSI reference model, the environment of CIM conformance test is designed, the framework of CIM conformance test declaration is discussed, and the flow chart of CIM conformance test is drawn up. Finally, taking the ABB40 CIM data as an example, the steps of test process and evaluation form of results are illustrated.

Key words: CIM; conformance test; OSI reference model; conformance test declaration

 

LIU Kai, LIAO Xiao-qun

(Xi’an University of Science & Technology，Xi’an 710054, China)

Abstract: The paper describes the transformation in automatic meter reading system. Q/GDW 376.1 protocol is briefly described. Attention is concentrated on the conversion between Q/GDW 376.1 protocol and DL/T645 protocol. To realize communication protocol conversion, embedded protocol conversion module is added between electric energy metering device or OLT server and multi-function meter, and the parametric variable for electric energy data volume and electric energy metering device according to Q/GDW 376.1 protocol and DL/T 645 protocol is encoded. And communication protocol conversion can be realized, based on connection oriented TCP communication and asynchronous serial communication. 376.1 GB of data acquisition terminal software (GBMS) and serial debugging software (Securer CRT) are used to test our designation. The result obtained agrees with the requirements of communication protocol conversion software. The protocol conversion can be applied to many aspects, such as electric energy data acquisition remote communication.

Key words: Q / GDW 376.1 protocol; DL645 protocol; protocol conversion; AMRS

 

ZUO Lan¹，DAI Peng¹，LI Jian-gong²，XIA Chen-yang¹，WU Xiao-jie¹

(1. College of Information and Electrical Engineering, China University of Mining and Technology, Xuzhou 221000, China; 2. Puyang Power Supply Company, Puyang 457000, China)

Abstract: To aim at the problem that there are many factors affecting the transmit power and efficiency of the ICPT system, which made the parameter design of system too difficult and the optimization calculation for its efficiency too complex, the design model and the parameters constraints of ICPT system are introduced firstly. Then, based on an improved swarm optimization algorithm used to solve the equation constrained optimization problem, the equation constrained optimization algorithm with introduction of the shrinkage factor and the mutation operator effectively improved the convergence speed and accuracy. Next, to aim at a given output power ICPT system, system efficiency was improved at most by means of optimizing the system mutual inductance coupling coefficient, resonance frequency, load resistance and other parameters. Finally, simulation and experimental platform is built for comparing and analyzing transmission power and efficiency of systems with combination of different parameters, and the numerical results and the experiment results verified the effectiveness of the algorithm.

Key words: ICPT; efficiency; optimization; PSO

 

DENG Ya-feng¹, XUE Jian-guo², QIAO Xiang-jie³, ZHANG Xu-peng⁴

(1. School of Material and Mechanical Engineering, Beijing Technology and Business University, Beijing 100024, China; 2. Tsinghua University, Beijing 100084, China; 3. Beijing Union University, Beijing 100101, China; 4. Beijing Special Equipment Inspection &Testing Center, Beijing 100049, China)

Abstract: Low coupling coefficient can be compensated by joining high quality factor intensifier coils between primary and secondary coils, thereby transmission distance of wireless power supply system is increased. The paper takes dual intensifier coils electromagnetic resonant wireless power supply system as research object, and the theoretical calculation formula of maximum effective transmission distance is derived first time in critical coupling condition. Experimental result shows that the theoretical calculation formula of maximum effective transmission distance is right.

Key words: wireless power supply; intensifier coils; maximum effective transmission distance

 

OUYANG Le-cheng，WU Guang-ning， GAO Guo-qiang，LI Tian-zhi

(School of Electrical Engineering，Southwest Jiaotong University，Chengdu 610031，China )

Abstract: The vehicle-mounted vacuum circuit breaker will open the circuit when locomotive regenerative braking or passing the articulated phase insulator. It will produce high operating overvoltage. Simplified circuit model is established in this paper according to the power supply system of locomotive. The transient process of vacuum circuit breaker interruption is simulated using EMTP. Based on the simulation results, influencing factors of overvoltage and two different overvoltage protection devices are analyzed. The parameters of the protectors are also determined. The results indicate that, the greater the ground capacitance of transformer is, the lower the overvoltage peak will be; MOA can limit the amplitude of overvoltage obviously, but it is not effective enough to reduce the gradient and frequency of overvoltage; RC device can reduce the amplitude、steep degree and frequency of overvoltage well.

Key words: vacuum circuit breaker；EMTP；overvoltage；protection；arrester

 

YANG Ming-qiang, CHEN Qian-hong, ZHANG Chao

(Nanjing University of Aeronautics & Astronautics, Nanjing 210016, China)

Abstract：In order to implement the voltage spike interference test of airborne electrical equipment, the paper developed a voltage spike generator that meets the RTCA - DO160E and GJB181-1986 standard by combining the full-bridge inverter circuit with LC resonant and outputs voltage spikes. In the paper, the function of circuit component parameters and voltage spikes is derived, and the design method of pulse transformer in the main circuit is given. By analyzing the main circuit, the paper describes the principle and method of how the LabVIEW generates the drive signal to control the voltage spike generator, and the switch drive logic. Finally, a voltage spike generator is built and subjected to experiment. The experimental waveform verifies the correctness of the theoretical analysis and is in full compliance with the provisions of voltage spike waveform in the RTCA of DO160E and GJB181-1986.

Key words: voltage spike; LC resonant; LabVIEW

 

On-line monitoring system for substation power quality

TENG Zhi-jun¹, WANG Zhong-bao¹, SUO Da-xiang²,，LI Guo-qiang¹

（1．Department of Information Engineering, Northeast Dianli University, Jilin 132012,China;

2．Tianjin electric power corporation, Tianjin 300010，China）

Abstract：This paper briefly expounded the theory and the process of the power quality data monitoring in substation using ZigBee, and the design of the software and hardware in all relative parts is completed and the power quality data in coal mine environment is tested. The result of the tests showed that the installation and debugging of the monitoring system is simple and convenient. The whole system is steady and the electromagnetic compatibility is very well, so the system has great application value.

Key words：substation; power quality; ZigBee; monitoring

 

NAN Xiao-qiang, LI Qun-zhan, WU Hao

(Electrical Engineering of School, Southwest Jiaotong University, Chengdu 610031, China)

Abstract: Based on the aerodynamic model of variable speed wind turbine and hill-climbing search， one of the Maximum Power Point Tracking (MPPT) algorithms, definition formula of probability function used in simulated annealing algorithm is referenced in the paper. It is used to define the adaptive step. The purposes are that dynamic characteristics is fine at beginning of searching stage, and steady state characteristics is more stable at the end of searching stage. The model of variable speed wind turbine and the effects of output power when wind speed is changing are realized in Matlab. The conclusion is that improved algorithm can make output power stabilized at new state, and dynamic characteristics and steady state characteristics are stratifying.

Key words: Maximum Power Point Tracking (MPPT); variable-speed wind-power generation; simulated annealing algorithm; hill-climbing search algorithm

 

YANG Xiao-feng¹，WU Jing-bing²

(1. Baoji Power Supply Company of Limited Company of Shanxi Regional Electric Power Group, Baoji 721004, China; 2. Fuzhou Electric Power Industry Bureau, Fuzhou 350009, China)

Abstract: High voltage Static Var Compensator (SVC) is regarded as the research target in this paper. In view of the problem that traditional PID is difficult to track the setting value and to suppress the disturbance, the paper proposes a novel control method consisting of nonlinear neural PID control and a second order derivative control to achieve the aim for keeping the voltage stability in point of common coupling. Improved neural learning algorithm is used to optimize the parameters of the controller to achieve best transient response and control performance, and on-linear function is introduced to eliminate the overshoot of the system. Experimental results verify that the proposed control strategy is able to guarantee the output of tracking of the set value of SVC system fast and nonovershooting, has good adaptability and robustness, and can improve the compensation accuracy of system.

Key words: high voltage static var compensator；nonlinear；neuron PID control；second order derivative control

 

LI Juan, CHEN Xiao-jin, WANG Kun, ZHOU Jian-ying, YAN Nai-xin

(School of Electrical Engineering , Northeast Dianli University, Jilin 132012, China)

Abstract: In order to improve the economy of system operation, IPC (Interphase Power Controller) is put into the network to control power flow so as to realize network loss optimal. In this paper, based on the optimization model of network loss, in the condition of maintaining the original network node admittance matrix symmetry, the loss optimization mathematical model of IPC is established on the basis of the basic structure of IPC. In this model, the influence of IPC to network is equivalent to the node additional injected power and the network loss optimization model equation constraints are introduced. Then the constraints of branch power containing IPC and IPC parameter are introduced into the inequality constraints. By the penalty function and decoupling method, the optimization of network loss is solved. The results of IEEE5 and IEEE14 node example analysis demonstrate the effectiveness of the model, and show IPC can achieve the network loss optimization, and is helpful for economic operation of the system.

Key words: IPC；flow control; network loss optimization; additional power injection； multiplierpenalty function；decoupling method

 

SHANG Li-qun, ZHAO Jia-jia, WANG Jiang-ning

(1. Xi’an University of Science and Technology, Xi’ an 710054, China; 2. Yulin Electric Power Supply Corporation, Yulin 719000, China; 3. Tianshui Electric Power Supply Corporation, Tianshui 741000, China)

 Abstract: Hilbert-Huang Transform (HHT), a kind of new methods, deals with nonlinear and non-stationary signal. The core of HHT is named EMD, which can self-decompose complicated signals into a set of single-component signals, each of which has physical sense. But when using the EMD to dispose the nonlinear and non-stationary signal, the EMD will produce endpoint effects which make the decomposed modal component serious distortion, then affecting the accuracy of the fault line greatly. Based on this, the paper uses a self-adaptive waveform matching extending method to improve the HHT algorithm, and then builds the non-solidly earthed system simulation model, which is used to test the effect of applying improved HHT detection method to detect the fault line. The simulation test showed that the improved method not only effectively inhibits the endpoint effect of HHT, but also improves the accuracy rate of one-phase ground fault location.

Key words: improved HHT; self-adaptive waveform match; non-solidly earthed; line detection