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Research of static var compensator’s time characteristics and system-level model of controlled current source
ZHANG Chao1，JIANG Qi-rong2，LI Juan1，TIAN Xu2，SUN Shou-xin1
(1. College of Electrical Engineering, Northeast Dianli University, Jilin 132012, China;
2. College of Electrical Engineering, Tsinghua University, Beijing 100084, China)
Abstract: In view of lacking research on response time of static var compensator (SVC), this paper established the controlled current source model which can achieve the same effect in response time and reactive compensation with the physical model of SVC by analyzing of characteristics in reactive power compensation and the response of the SVC physical model. Through the time module in control signal of controlled current source, it can accurately calculate the response time of SVC. It tested the consistency of two models through the simulation of a rolling mill start experiment in PSCAD.
Key words: static var compensator (SVC); controlled current source model; response time
A reference voltage vector synthesizing algorithm for N-level inverter based on virtual-dwell-time transformation
ZHONG Li-ping, GU Qi-min, KONG Wei-tao, LI Xin
(School of Elec. and Automation Eng., Changshu Institute of Technology, Changshu 215500, China)
Abstract: This paper presented a novel algorithm combining non-orthogonal coordinates transformation and linear transformation. By means of this method any voltage vector can be transformed into the 60°non-orthogonal coordinate system, and the virtual dwell time of the two basic long vector which synthesizing this reference voltage vector as well as the nearest three vectors (NTV) can be simply deduced from its coordinate figure. The dwell time of these NTV can be acquired from the virtual time by using a linear transition. Simulation and experimental results verified the validity of the proposed approach.
Key words: non-orthogonal coordinates transformation; linear transition; multi-level; virtual dwell time
Research on essential safety performance for interleaving magnetics buck converter
YANG Yu-gang, LI Na
(Electrical Control Engineering Institute, Liaoning Technical University, Huludao 125105, China）
Abstract: In order that the maximum released energy of the output short circuit is less to meet the essential safety requirements in the buck converter, the paper proposes that magnetic integration technique is applied to the interleaving buck converter. By properly designing the channel number N and duty cycle D, the circuit can achieve rather ideal output current ripple. Taking two-interleaving magnetics buck converter for example, the reverse coupling integration between inductance and inductance can reduce the single channel output current ripple, which may reduce the maximum released energy of the output short circuit and improve the transient response speed of the circuit. These are beneficial to the realization of essential safety. The interleaving magnetics buck converter is simulated in MATLAB and experimented. Finally, the result proves the correctness of the proposed method.
Key words: essential safety; magnetic integration technique; output current ripple; the max released energy of the output short circuit
A passive and isolated battery voltage monitoring method
HUANG Jun1, LING Zhi-bin1, CAI Xu1,2
(1.Key Laboratory of Control of Power Transmission and Transformation, Wind Power Research Center, School of Electronic Information and Elec. Eng., Shanghai Jiao Tong University, Shanghai 200240, China; 2.State Key Laboratory of Ocean Eng., School of Naval Architecture, Ocean and Civil Eng., Shanghai Jiao Tong University, Shanghai 200240, China )
Abstract: In battery energy storage technology, a large number of batteries in series bring a high battery terminal voltage which brings difficulties to the voltage detection and capacity monitoring. A passive and isolated battery voltage monitoring method is proposed based on correcting the linearity of digital optocouple. This voltage monitoring circuit consists of four parts: digital optocoupler isolation circuit, current-voltage conversion circuit, signal conditioning circuit and voltage reference section. In this paper, transmission characteristics and temperature drift characteristics of the optocoupler are analyzed, and piecewise linear correction method is proposed. Finally the experiment results show that this method can easily solve the isolation problem of high voltage and low voltage. Moreover, the passive voltage monitoring is also achieved with a low cost.
Key words: linearity correction; voltage monitoring; digital optocoupler; isolation
Application of electromagnetism-like mechanism algorithm for economic operation of hydropower station
ZHANG Zhi-sheng1, GONG Wen-jie2, DUAN Xiao-yan2, BI Guo-wei3
(1. School of Automation Engineering, Qingdao University, Qingdao 266071, China; 2. Qingdao Electric Power Company, Qingdao 266002, China; 3. Weihai Electric Power Company, Weihai 264200, China)
Abstract: Economic operation of hydropower station is an important research issue for power system, which can increase the economic benefits of hydropower station. Many algorithms have been used to solve this problem. Electromagnetism-like mechanism algorithm is firstly used in economic operation of hydropower station in this paper. Electromagnetism-like mechanism algorithm is a stochastic evolutionary technique based on the electromagnetic theory in physics. This algorithm simulates attraction and repulsion mechanism for particles in the electromagnetic field. Every solution is regarded as a charged particle, and it moves to optimum solution according to certain criteria which need several steps including local searching, calculating synthetic force and moving particle. Electromagnetism-like mechanism algorithm possesses excellent global optimal performance, simple programming realization and good convergence. Comparing with other algorithms, simulation results validate that electromagnetism-like mechanism algorithm can effectively solve economic operation problem of hydropower station. It can be used to solve other research problems in power systems.
Key words: power system; hydropower station; economic operation; electromagnetism-like mechanism algorithm
Modeling and control for energy storage bi-directional DC-DC converter based on switching system
LI Ji-fang1,2, TANG Tian-hao1, YAO Gang1
(1. Logistics Engineering College, Shanghai Maritime University, Shanghai 200135, China;
2. Kaifeng University, Kaifeng 475004, China)
Abstract: AC motor variable frequency speed regulation system has been widely used in industrial and agricultural production. Recycling is the important approach to save energy which is caused by braking of motors systems. Supercapacitor based energy saving system can absorb the braking energy when motor decelerate, which achieves energy-saving. In this paper, the architecture of an energy storage system is analyzed to get the equivalent circuit firstly. Then, the switching system model is established for the bi-directional DC-DC converter of the energy storage system, and Lyapunov function is constructed to get the system switch rules. Simulation result shows that with the control of the switching rules, the model can fully absorb and utilize the feedback electrical energy of the motor.
Key words: energy storage; bi-directional DC-DC converter; switching system; modeling and control
Small signal analysis of interleaved flyback converter with magnetic integration
MAO Chun-feng, CHEN Wei, LU Zeng-yi
(Fuzhou University, Fuzhou 350108, China)
Abstract: In the application of high current converter, interleaving technique is widely adopted to decrease the output ripple, improve the heat dissipation and enhance transient performance. This paper introduces the two-phase interleaved flyback DC/DC converter with magnetic integration, derivating the equivalent circuit of the converter by building the dual relationship between magnetic circuit and electric circuit, analysing the equivalent circuit with small signal model, and gaining the transfer functions of the converter. Then the prototype with 48V input and 12V/10A output was built for experimental verification.
Key words: interleaved; magnetic integration; equivalent circuit; small signal model
Research on method of theoretical calculation of energy loss for distribution network after small source connected
LI Xiao-long1，ZHANG Xu-hui2，ZENG An-li2， ZHOU Li-xing1，CHEN Wei-tu1
（1. Changsha University of Science ＆ Technology, Changsha 410076, China；
2. Hunan Power Grid Corporation Shaoyang Power Supply Bureau, Shaoyang 422000, China）
Abstract: In view of the character of the distribution network which was directly connected with small source, an improved method of equivalent capacity was proposed combining with the equivalent resistance model after analyzing several line loss calculation methods. This proposed method considered the complex situations of operating nodes changing in power distribution network on the representation day, and the situations including the two-way flow of power system tidal current between small source supply and distribution network. Practical examples were used to verify the improved method.
Key words: small sources；distribution network；electric energy loss；equivalent capacity；operating mode changing
Development of 30V/100A wide-variable-frequency current power amplifier
in relay protection testing apparatus
WU Hao, GUAN Song-min, CHEN Qian-hong, QIAN Hai
(Nanjing University of Aeronautics & Astronautics, Nanjing 210016, China)
Abstract：Power amplifier is an important part of the relay protection testing apparatus. Compared with conventional inverters, it requires high output precision and high power density while its frequency can vary widely. Considering the system performance and application, a system design method of 30V/100A current power amplifier is given in this paper. Then, by setting and solving the gain function equations, the parameters of inverter output filter is designed. Finally, experimental results of each part show that the system design and the parameters design method of inverter output filter are feasible.
Key words：wide variable frequency; current power amplifier; inverter output filter
Analysis and realization of LLC resonant converter with following PWM control strategy
GUAN Song-min1, ZHANG Chao1, YU Suo-ping2, CHEN Qian-hong1
(1. Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China;
2. Leader Electronics Co., Ltd., Zhenjiang 212000, China)
Abstract: LLC resonant converter will work with PWM control mode during current-limiting condition. But few literatures address the characteristic of LLC resonant converter with PWM control mode. In this paper, symmetrical PWM control strategy and asymmetrical PWM control strategy are discussed and a novel PWM control strategy is proposed. Based on the illustration of the operating principles, the soft-switching characteristic of the duty cycle is analyzed in detail. The results of analysis and experiment on a 48V/480W converter verify that this control scheme could realize the soft-switch control under the constant duty cycle to the converter.
Key words: LLC resonant converter; PWM control strategy; soft switching
Study on single-stage dual-output PFC converter for HB-LED driver
YANG Jing, ZHUANG Sheng-xian, LIU Xue-shan
(School of Electrical Engineering, Southwest Jiaotong University, Chengdu 610031, China）
Abstract: High-brightness light emitting diode（HB-LED）driver based on single-stage dual-output power factor correction (PFC) flyback converter operating in discontinuous-conduction mode (DCM) is proposed in this paper. To avoid cross-regulation of two outputs of converter and improve the reliability of the driver, time-multiplexing signal (TMS) is used to regulate each output current independently, and it enables different output to drive different types of LED strings. The failure of one output does not affect other output, improving the reliability of driver. The converter can achieve high power factor by working in DCM, fixed frequency and fixed duty cycle. Additionally, the converter can achieve dual-output constant current output by using only one magnetic device, and it realizes the power factor correction at the same time, thus reduces the cost of the driver. Finally, simulation and experimental results are presented to describe and verify the proposed technique.
Key words：dual-output constant current source; independent regulation, single-stage PFC; timing-multiplexing
Research of calculation of flicker values based on inter-harmonics measurement
LI Fei-fei1,3, YANG Hong-geng1,3, HUI Jin1,3, YE Mao-qing2
(1. School of Electrical and Information, Sichuan University, Chengdu 610065, China;
2. Sichuan Electric Power Research Institute, Chengdu 610072, China)
Abstract: This paper proposed a new method to calculate the voltage flicker values based on inter-harmonics measurement. In this method, the concept of “AM- inter-harmonic pair” and “PM- inter-harmonic pair” are proposed to distinguish the modulation wave and general inter-harmonics which will cause flicker based on the voltage distortion theory. The proposed method obtains the parameters of each frequency component using the odd points interpolation correction method, which reducing the leakage at interpolating, based on the specified signal processing recommendations by IEC61000-4-7. Considering the voltage flicker perceptible frequency range and the signal transform equations, we can estimate the parameters of flicker signal. According to the theory of IEC flicker meter, we can calculate the instantaneous flicker sensation level caused by each frequency component or the total flicker signal. Compared with the Square method, the simulation example and the field data of an electric arc furnace voltage signal demonstrate the accuracy and feasibility of this method.
Key words: power quality; flicker; inter-harmonics; frequency domain analysis
Investigation of control strategy for matrix-converter-excited system
LI Hui1，YANG Chun-hua1，DENG Wen-lang2
(1. School of Information Science and Engineering, Central South University, Changsha 410083, China;
2. School of Information Engineering, Xiangtan University, Xiangtan 411105, China)
Abstract: Compared with traditional AC-DC-AC converter, matrix converter (MC) is a new type of AC-AC converters. MC has the advantages of controllable input power factor without the need for DC energy storage devices, compact structure, small size, and so on. In this paper, the MC is used for exciting system of double-fed induction generator (DFIG). The control theory of matrix-converter-exciting system is proposed to achieve the purpose of grid connection and power generation. The proposed method, which combines vector control of stator-voltage-oriented and indirect space vector control of MC, can achieve the purpose of grid connection and decoupled control of power. The experimental results are reported to show that the control method not only achieved grid-connection, but also transmitted active power and reactive power. The feasibility of the proposed method is verified. Therefore it has the value of practical applications.
Key words: matrix converter; doubly-fed induction generator (DIFG); AC-excitation; space vector pulse wide modulate（SVPWM）
Analysis of breaking capacity and design of structure optimization on auxiliary switch of high-voltage circuit breaker
JIN Li-jun1，WANG Ke1，LIU Jian-gang2, YAN Shu-jia1，ZHANG Yong1
（1.Tongji University, Shanghai 201804, China; 2.Ningbo Yaohua Electric Factory, Cixi 315324, China）
Abstract：In order to reduce the electric field maximum and homogenize the electric field distribution, a two-dimensional numerical model for arc-quenching chamber of FK-口auxiliary switch was established to analyze the internal electric field distribution. Based on electric-field simulation, we know that the electric field distribution is uneven, and maximum is located at the interval between moving and static contacts. It was the weak spot for dielectric breakdown. To improve the breaking capacity, the dielectric strength is calculated using a bit uneven electric field theory, and a judgment condition of dielectric breakdown after current was zero was given. The dielectric strength is in inverse proportion to electric field. To avoid the breakdown failure, the shape of contacts and wall structure of arc-quenching chamber are optimized. By optimization, we know that the contact shape has more influence on electric field distribution. Finally, by the total optimization, the electric strength is decreased, arcing performance is improved, and that was tested by experiment. The research provides the direction for optimization design of auxiliary switch.
Key words：auxiliary switch; breaking capacity; configuration optimization
Future power grid — Multiple-level DC loop grid and “Cloud Powering”
XIAO Li-ye1,2, LIN Liang-zhen1,2, XU Ming-ming1,2, DAI Shao-tao1,2
(1. Key Laboratory of Applied Superconductivity, Chinese Academy of Sciences, Beijing 100190, China; 2. Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100190, China)
Abstract: In the future, the renewable energy will be the dominant energy. Due to the special performance and the distribution picture of the renewable energy, it will need to develop a corresponding future power grid. In this paper, we suggest that a multiple-level DC loop grid would be the suitable mode for power grid, in which DC-based loop grid for wide-area transmission system, distribution system and distributed network should be developed, and all the power sources and customers would be connected to the loop grids. The power transmission line and cable are used to connect all the loops. Therefore, the future power grid would be able to make full use of the complementarities of all of the energy resources distributed in the wide area including large-scale power plants and distributed power plants. This means that the future power supply would be a "Cloud Powering" mode other than the present mode.
Key words: renewable energy; complementarities of the energy resources; Multiple-level DC loop grid; distributed power grid; Two-way power exchange control; cloud powering
Research on a high-speed contactor used for voltage-downcast compensation apparatus
WANG Pu-qing1，YUAN Duan-li1，DONG En-yuan2, QIN Tao-tao2
(1. Pinggao Gruop Co.LTD, Pingdingshan 467001, China; 2. Dalian University of Technology, Dalian 116023, China)
Abstract: Enterprise’s important devices such as micro motor, precision instrument and so on, demand high quality power transmission. Instant voltage-downcast due to line-fault or power failure will reduce the yield of production. In traditional high-efficiency UPS supply, the price of power electronic devices is expensive and running losses is high whose loss-heat can damage to components because of semiconductor’s long-time working. So a high-speed contactor consists of repulsion actuator and permanent magnet actuator is present in this paper, which can act reliably by high speed and has big current-transit capacity. When the power faults occur, the high-speed contactor will break quickly, and a power electronic device which is parallel with it will finish the remaining task. Ansys software is used for finite element simulation, and the results are analyzed, based on which the model machine is manufactured. Finally test shows the novel contactor can move fast, and the energizing time is very short which can ensure the compensation system work successfully.
Key words: voltage-downcast; high-speed contactor; repulsion actuator; Ansys simulation
Research on self-power supply system of inspection robot for high-voltage power transmission lines
WANG Peng, MEI Sheng-wei, LIU Feng, WANG Guan-qun, WANG Ke-fei
(State Key Lab of Power Systems, Dept. of Elec. Eng., Tsinghua University, Beijing 100084, China)
Abstract: Inspection robot is a promising technique in automatic fault detecting for high-voltage power transmission lines. However, the small energy capacity of the battery holds back the application of the inspection robots. To solve this problem, a self-power supply system utilizing the energy coupling from the current on the transmission line is designed to realize the online battery charging. Discussion is made in details on the key issues related to the optimal design and practical implementation of the self-power supply system, including the induction module, the power conversion module and the logic of power charging and supply. Tests have been carried on to demonstrate the validity and effectiveness of the designing.
Key words: self-power supply system; robot; induction
Research on voltage-balanced asymmetric multi-level inverter for motor’s speed control
CAO Ying, FU Guang-jie, HOU Yong-qiang
(Northeast Petroleum University，Daqing 163318，China)
Abstract: Nowadays, multi-level inverter technique is already widely used in the high-voltage and high-power field. Meanwhile the hybrid asymmetric 6-level inverter has been focused on for its simple construction and waveforms without 0 level. However, we all know that mid-point voltage control is one of the technical difficulties to high-voltage high-power multi-level inverter circuit. So a new single-phase hybrid asymmetric 6-level inverter is researched in this paper. In the inverter a 3-level Half-bridge unit and a Half-bridge unit are cascaded to form an inverter phase leg. This kind of construction can make the mid-point voltage balance without any other special circuit and complicated control methods. Meanwhile, 6-lever will be put out at the end of the circuit. The EPWM control method is proposed considering the construction of the inverter. The experiment on the voltage-balanced asymmetric 6-level inverter for motor’s speed control is carried out and the ideal output waveforms show the feasibility of the construction and the reasonableness of the EPWM method.
Key words: voltage-balanced; asymmetric 6-level; inverter
Research on photovoltaic distributed maximum power point tracking
based on non-inverting buck-boost converter
WU Chun-hua, XU Kun, HUANG Jian-ming, YANG Yu, XU Fu-qiang
(Shanghai University, Shanghai Key Lab of Power Station Automation Technology, Shanghai 200072, China)
Abstract: The working principle, working mode and impedance transformation of photovoltaic distributed maximum power point tracking (MPPT) based on non-inverting buck-boost converter are analyzed. The essence of MPPT is elaborated in detail from the perspective of the load impedance matching and a MPPT control strategy for non-inverting buck-boost converter is proposed in this paper. The algorithm can select different working mode automatically in order to make system working at maximum power point. The experimental results verify the feasibility and efficiency of the algorithm.
Key words: distributed; buck-boost; maximum power point tracking (MPPT); non-inverting
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