Selections of performances weighting functions for H∞ non-fragile robust control to a superheated steam temperature system

HENG Qing-hai1，LU Jing1，HENG Qing-zhu2，LI Bo3
（1. Beijing Information Technology Institute, Beijing 100101, China; 2. Tianjin University, Tianjin 300072, China; 3. Beijing Institute of Machinery, Beijing 100085, China）

Abstract：The concept of the selections of the performances weighting functions to different disturbance is presented so that the common control system with the perturbations of the controlled members and the controllers can be designed. It is suggested that a class of design problem of the non-fragile robust controller can be formulated as a H∞ mixed sensitivity. The performance can be improved to actual different disturbances of the system. The selections of the weighting functions of the uncertainties and the performances are discussed. The parameters of the PI controllers are designed. The simulation results show that the proposed method is efficient and feasible.
Key words：disturbance; performances weighting functions; non-fragile robust control; robust performance; controller

A novel PFM SMPS for anti-corrosion of oil-conveyance pipelines

ZHANG Jia-sheng, PAN Da-wei
(China University of Petroleum，Dongying 257061, China)

Abstract: This paper proposes a new type power converter for the cathode anticorrosion of oil-conveyance pipelines. Its circuit topology and operation principle are discussed . Also the operating process is analyzed and calculated by means of state locus charts generalized, thus the relevant design formulas are derived. A kind of distinctive pulse frequency modulation (PFM) control method is presented in accordance with the working characteristics of the converter as a specific case. The switch mode power supply  (SMPS) which are developed for cathode anticorrosion protection on the basis of the converter are of high power, low ripple output and  high reliability.
Key words: cathode anticorrosion; topology; zero current switching; trajectory of state; SMPS

Calculation of ampacity reduction factors for buried cables with surroundings based on FEM

LIANG Yong-chun1,2, CHAI Jin-ai1, LI Yan-ming1, WANG Zheng-gang3, LI Zhong-kui3
（1. Xi’an Jiaotong University, Xi’an 710049, China;
2. Hebei University of Science and Technology, Shijiazhuang 050054, China;
3.Zhengzhou Electric Power Company, Zhengzhou 450006, China）

Abstract: Finite element method (FEM) was used to partition the area of buried cables with outer heat sources and calculate the temperature field with given cable load. Bin-search method was used to calculate the cable load until the temperature of conductor is equal to the long endurable temperature of insulation and obtain the ampacity of buried cables with outer heat source and variation of temperature of air. The result gives out the relationship of the ampacity with the distance between outside of cables and outer heat source and the relationship of the ampacity with the variation of temperature of air. The result gives out a reference for practice.
Key words: FEM; bin-search method; outer heat source; buried cable; ampacity

Research on DBD-type ozone generator powered by series resonant inverter with inductive control

TANG Xiong-min1, YI Na2, PENG Yong-jin2　　　
(1. Guangdong University of Technology, Guangzhou 510006, China;
2. College of Electric & Information of Hunan University, Changsha 410082, China)

Abstract: The Dielectric Barrier Discharge circuit powered by full bridges series resonant inverter with inductive load is studied. By analyzing the on-off conditions of the power switches and the states of discharge and no discharge in DBD circuit, the two working states, the relevant working modes of whole circuit are obtained and the equations that describe these modes are deduced. Based on these equations, the expressions of the main electric parameters are derived and the regulating characteristics of the inverter are studied. By these expressions and regulating characteristics, the power supply for DBD circuit is studied in the paper. The error analysis between calculation results and experiment results are analyzed and the error analysis proves that the analytical method and the conclusion are correct.
Key words：inductive load; serial resonant; dielectric barrier discharge circuit

Research on variation mechanism of neutral-point potential for three-level NPC inverter based on voltage vector diagram partition

SONG Wen-xiang1, CHEN Guo-cheng2, CHEN Chen1
(1. Dept. of Electrical Engineering, Shanghai Jiaotong University, Shanghai 200030, China;
2. Dept. of Automation, Shanghai University, Shanghai 200072, China)

Abstract: This paper investigates the variation mechanism of neutral point (NP) potential in detail, establishes the average NP current model, thus the theory basis is built for the balancing control of neutral point potential, and several important conclusions about variation of NP potential are given. Theoretical analysis and experimental results indicate that the proposed method for NP balancing control is effective. The effectiveness of proposed research approach in this paper is verified by simulative and experimental results.
Key words: three-level Inverter; SVPWM; variation mechanism of neutral-point potential

Thermal design considerations for high-frequency power planar transformer

MAO Xing-kui, CHEN Wei　 
(College of Electrical Engineering & Automation, Fuzhou University, Fuzhou 350002, China)

Abstract: Higher power density requirement and dramatically increasing eddy current loss (including winding and core loss) impose severe challenges on thermal design of high-frequency planar transformer. Through heat transferring analysis of the planar transformer, a novel thermal model considering temperature rise of winding and core independently is proposed. Then a new design guideline of core temperature by analyzing relation between core loss and temperature is also given. The thermal model and the design guideline are helpful to improve the planar transformer thermal design. Experiments verified the thermal model and design consideration.　
Key words: switch-mode power supply; planar transformer; thermal design; winding loss; core loss

Dynamic analysis and improved design of current regulators for permanent magnet synchronous motors

ZHU Xiao-hui1, LI Ying-hui1, FU Ming-ming2

(1. Engineering Institute of AFEU, Xi’an 710038, China;
2. Heilongjiang Education Institute, Harbin 150080, China)

Abstract: The complex vector model for permanent magnet synchronous motors(PMSM) is presented and the performance of the equivalent complex current controller is investigated using complex vector root locus and complex frequency response functions. The frequency response function and dynamic stiffness function are used to analyze the performance of the proportional-integral current (PI) regulator in synchronous reference frame, and the results reveal that dynamic response deteriorates with the external disturbance injected and the fundamental excitation rising. The wavelet-based multi-resolution PI controller is introduced to improve its design. Both the theoretical and simulation results show that the improved regulator has better ability to provide disturbance and noise rejection compared with the conventional PI regulator.
Key words: PMSM; current regulators; complex vector root locus; complex vector frequency response; wavelet controller

A Robust Deadbeat Control Method for UPS Inverters　　　　　　　　

WANG Meng1, LI Fang-zheng, HUANG Li-pei, SAKANE Makoto2
(1. State Key Lab of Power Systems, Dept. of Electrical Engineering, Tsinghua University, Beijing 100084, China;
2. GS Yuasa Power Electronics Ltd., Osaka 569-1115, Japan)

Abstract: The traditional deadbeat control for UPS inverters has a robustness problem. The parametric imprecision can greatly harm the stability of the system, which restricts the application. A novel robust deadbeat control method is proposed in this paper to deal with the problem. In the proposed control method, a proportional element is added to the traditional deadbeat control in order to improve the robustness to parametric imprecision. To eliminate the error between output voltage and voltage reference caused by environmental noise and parametric deviation, a model reference adaptive regulator is also added to the control method. A 1kVA prototype is built based on DSP. Theoretical analysis and experimental results show that the robustness for parametric variation of the proposed method is much better than the traditional deadbeat control. The system can remain stable even when the systemic parameters have a large deviation from calculating parameters. The system has small static error and fast dynamic response with the new control method. This method is easy to realize in DSP and is suitable for full digital realization of UPS.
Key words: UPS inverter; deadbeat control; robustness; model reference adaptive control

A new method for SAPWM in direct current control of PWM rectifier

LI Jie，CHEN Guo-cheng，WANG De-li，MA Yi-wei
（Shanghai University，Shanghai 200072，China）

Abstract: SVPWM (space vector pulse width modulation) is often used for improving the utilities of DC bus voltage and decreasing the grid-connected harmonic current in control of three-phase VSR (Voltage Source Rectifier). However SVPWM is a sort of complicated in algorithm and can not be understood easily. SAPWM (Saddle Pulse Width Modulation) is a method of carrier wave modulation that can be understood and realized easily and equivalent to SVPWM actually. Using SAPWM in three-phase VSR direct current control also can achieve the aim of improving the utilities of DC bus voltage and decreasing the grid-connected harmonic current. This paper presents a method which can realize SAPWM（Saddle Pulse Width Modulation）in VSR direct current control by using 0-axis harmonic injection. The harmonic components of SAPWM modulation wave are analyzed by Fourier series, and triangle wave equivalent to the harmonic components is constructed. The method of realizing SAPWM by injecting triangle wave from 0-axis is expatiated. The simulation and experiment were presented to verify the proposed theories.
Key words：PWM rectifier；direct current control；SAPWM；0-axis harmonic injection

Fundamental characteristics study of thermophotovoltaic system

CHEN Xue, HAN Yu-ge, LI Qiang, XUAN Yi-min
(School of Power Engineering, Nanjing University of Science & Technology, NanJing 210094, China)

Abstract: Technology advances in thermophotovoltaic (TPV) diodes and improvements in spectral control filters have enabled consideration of TPV for power applications technology, it requires a new evaluation of the TPV efficiency. This report presents an assessment of the efficiency of thermophotovoltaic (TPV) energy conversion systems. By calculating of the efficiency and power density under different conditions , we address some important points in TPV system design , and provide a better understanding of the basic system limitations that will enable successful long-term development of TPV energy conversion technology.
Key words: TPV; efficiency; Monte-Carlo method; photovoltaic cell

Cooperative control scheme for phase lock loop and load sharing
in parallel operation of UPS with no control interconnections

LIN Xin-chun, DUAN Shan-xu, KANG Yong
 (Huazhong University of Science and Technology, Wuhan 430074, China)

Abstract: In the parallel operation of UPS with no control interconnections, the droop characteristic is widely adopted as the current-sharing control strategy. However, as the phase lock loop and the frequency droop characteristic may simultaneously change the inverter’s output frequency when power supply is normal, there may be disturbance between the phase lock loop and the frequency droop characteristic, which may cause oscillation or even instability of the UPS paralleled system. Aiming at this disturbance, this paper presents a cooperative control scheme, which not only can completely eliminate the disturbance between the phase lock loop and the frequency droop characteristic, but also can achieve good load-sharing, and at the same time the presented cooperative control scheme also can achieve high utility phase tracking precision. The dynamic and static experimental results for different loads are presented for two paralleled UPS with no control interconnections, which prove the feasibility of the proposed control scheme.
Key words: UPS; parallel operation with no control interconnections; phase lock loop; control scheme

Study on aging characteristics for inverter-fed traction motor inter-turn insulation based on analysis of dielectric characteristic parameters

HE Jing-yan, WU Guang-ning, GAO Bo, LEI Ke-gang, WU Jian-dong 
(School of Electrical Engineering, Southwest Jiaotong University, Chengdu 610031, China)
Abstract: It has been shown that the waveforms generated by the power converters play a major role in inverter-fed traction motor insulation degradation. Deeper investigation of aging phenomena caused by supply voltage waveforms is needed, especially regarding the relation between aging factors and stress conditions. Accelerated aging tests under different supply voltage waveforms and temperatures were conducted on twisted pairs simulating inter-turn insulation of inverter-fed traction motor. Tan and sample capacity were measured under different testing voltages to investigate influence of tan and capacity under different aging additions. Based on analysis of dielectric loss and mechanics of square wave pulses, the experimental results show that PDIV is increasing with the increase of voltage amplitude in the early aging stage. PDIV is affected significantly by space charge accumulation under bipolar waveforms, which is almost independent of frequency among three factors. Small change of temperature has a strong impact on insulation. Impulse amplitude, frequency and temperature have a cooperative effect, which shows that strengthening or weakening of each factor will alter trend of other factors effect on insulation.
Key words: inverter-fed motor; inter-turn insulation; aging; dielectric loss; space charge

Measurement and analysis system for partial discharge under continuous square pulse voltage

  ZHOU Kai, WU Guang-ning, WU Jian-dong, LIU Jun, LIU Xi
(Southwest Jiaotong University, Chengdu 610031, China)

Abstract: In this paper, a partial discharge measurement and analysis system is presented under square pulse voltage. Response of sensors made by different core materials was compared in order to obtain better response at high frequency. Also, wavelet package is used to filter out high and low frequency interference. Furthermore, depending on analysis for partial discharge under pulse voltage, statistical method is discussed to obtain different statistical parameters, and features of statistical parameter have been investigated. In particular, a relationship between aging time and statistical parameter was observed in specimens. The measurement system contributes to study partial discharge under square pulse voltage. These conclusions could be used to further investigate properties of aging under PWM voltage.
Key words: pulse voltage; partial discharge; wavelet package; skewness

Two level inverter controlled by single DSP

WANG Feng-yan1,2, ZHAO Wei-gang1, XU Jian-ping2
( 1. National EW Laboratory, CETC No.29 Research Institute, Chengdu 610036, China;
2. College of Electrical Engineering, Southwest Jiaotong University, Chengdu 610031, China)

Abstract: The paper studied “DC/DC converter + DC/AC inverter” two level converter which is controlled by single DSP controller. The principle of the circuit is introduced. The transfer functions of DC/DC converter and DC/AC inverter are designed based on a more accurate model proposed. The influence of digital controller’s control delay is analyzed and simulated. The validity of circuits and control transfer function is verified by the experiment on a 500VA 28VDC/115V 400Hz inverter prototype.
Key words: inverter; converter; digital control; DSP

Assessment of black-start schemes for power grid based on relational matrix analysis

MENG Xian-peng, YAO Li, LIN Ji-keng
（School of Electrical and Automation Engineering, Tianjin University, Tianjin 300072, China)
 
Abstract: The restoration of power system after a complete blackout is a very important problem. Evaluation of schemes of black-start can help dispatchers to establish black-start schemes and restore power system as quickly as possible. As a system evaluation method based on matrix modules，relational matrix analysis has the advantage of combining objective with subjective evaluation. The paper uses the method of relational matrix analysis to analyse and assess various schemes, so that scientific and instructive decision reference can be provided to the dispatchers.
Key words: black start; relational matrix analysis; analysis and assessment; restoration; decision reference

Effect of packed quartz pellets on DBD plasma treating with NO

ZHONG Kan1,2, NIE Yong1,2 , WANG Jingyi1,2, GUAN Zhicheng1,2, JIA Zhidong1,2, WANG Liming1,2 
（1.Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China; 2.Department of Electrical Engineering and Applied Electronic Technology, Tsinghua University, Beijing 100084, China)

Abstract: Two-step plasma-assisted selective catalytic reduction of NOx is one of the promising methods of NOx treatment. DBD is a common method to produce plasma, and dielectric pellets packed into the DBD reactor could further enhance the discharge intensity. In this paper, the performance of NO treatment in DBD reactor packed with quartz pellets was compared with that in an empty DBD reactor, including NO conversion efficiency and NO energy yield. Meanwhile, the electric field simulation in DBD reactor with ANSOFT software was also analyzed. Results showed that the performance of DBD reactor packed with quartz pellets was superior to empty reactor on NO conversion efficiency and NO energy yield at lower applied voltages, although the energy consumed in packed reactor was a bit higher. These phenomena are due to that quartz pellets packed in DBD reactor could enhance the partial discharge at lower voltages, promote the uniform distribution of the electric field and reacting gas stream in DBD reactor, and improve the contacting chance of the reacting gas stream with DBD plasma.
Key words: NO; DBD plasma reactor; quartz pellets; packed reactor; energy yield; electric field

Research on the ramp compensation of sensorless current mode control switching DC-DC converter

TAO Xue-hui, XU Jian-ping, WU Song-rong
(School of Electrical Engineering, Southwest Jiaotong University, Chengdu 610031, China)

Abstract: Several kinds of conventional current sensing methods for switch mode power supply are firstly introduced in this paper, and the drawbacks of these current sensing methods are also analyzed. On the basis of which, sensorless current mode control method with no need of any current sensing circuit is introduced. Through detailed study and analysis on the operation principle of the sensorless current mode control and the subject on ramp compensation of the sensorless current mode control, it is found that improved stability of the control loop can be achieved by compensating a ramp with an appropriate slope to the output signal of the error amplifier. Thus, the problem of the instability of the control loop can be solved by this method.
Key words: switch mode power supply; current mode control; sensorless current mode control (SCM); ramp compensation; stability