Passive Filter Design for China High-Speed Railway ... - IEEE Xplore

IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 30, NO. 1, FEBRUARY 2015

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Passive Filter Design for China High-Speed Railway With Considering Harmonic Resonance and Characteristic Harmonics Haitao Hu , Student Member, IEEE, Zhengyou He , Senior Member, IEEE, and Shibin Gao

Abstract—In order to make high-speed trains (HSTs) lighter and more reliable, LC or LCL high-pass filters, which are widely adopted to mitigate high-order harmonics, are not installed in most of China HSTs. Therefore, the harmonic problem is a concern, because of the significant adverse impacts it has on the tractive drive system of the train and power quality of the utility system. The harmful harmonic distortions in high-speed railways (HSRs) are mainly caused by harmonic resonance and massive characteristic harmonics emission. This paper presents the results of harmonic assessment and harmonic filter design for a typical HSR line in China. Harmonic penetration analysis (HPA) is implemented and carried out to determine the harmonic distorted types for a wide range of possible train-operating conditions in a timetable. Both statistical field test and numerical calculation are used in passive filter design for HSRs. A C-type filter is designed here to address these typical harmonic distortions. The studies will be validated by detailed simulations based on the train timetable by counting the 95% index of the 24-h profile of harmonic results. Index Terms—C-type filter, China high-speed railway, filter design, harmonic penetration analysis, harmonic resonance.

I. INTRODUCTION

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ITH THE rapid development of the large power capacity, high operation speed, and density of high-speed trains, the resulting harmonic distortions have been a critical power-quality (PQ) issue for power utilities and electrical railways. Harmonic distortion can cause overvoltage problems with capacitive devices and arresters, electrical equipment overheating, motor failure, inaccurate metering of current transformers (CTs) and potential transformers (PTs), and electromagnetic interference (EMI) with communication systems [1]–[3]. Since no grid-tied filters are installed on the ac side of the train [3], the massive harmonics generated from the high-speed train (HST) are propagated and magnified through the catenary system into the utility system. Thus, harmonic problems

Manuscript received June 29, 2014; revised August 07, 2014; accepted September 05, 2014. Date of publication October 02, 2014; date of current version January 21, 2015. This work was supported by the National Natural Science Foundation of China (U1134205, 51177139, 51477145). Paper no. TPWRD-00781-2014. The authors are with the College of Electrical Engineering, Southwest Jiaotong University, Chengdu 610031, China (e-mail: [email protected]; [email protected]; [email protected]). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TPWRD.2014.2359010

in the high-speed railway (HSR) are mainly characterized by harmonic resonance of the specific rail system topology, and high-frequency characteristic harmonics injected from the trains [4]–[6]. A. Harmonic Problems in HSR Most of the HSTs running in an ac railway system adopt a pulsewidth-modulation (PWM) voltage-source converter (VSC) [3]. Although harmonic distortion of the VSC output current is usually below 5%, the current contains high-frequency components near the PWM switching frequency (frequencies: 2–15 kHz) [7]. Other VSC installations, such as photovoltaics and wind turbines, have adopted grid-tied filters to mitigate the injected high-order harmonics [8], [9]. However, most of China's HSTs do not employ such grid-tied filters. As a consequence, the massive characteristic harmonics, for example, a three-level VSC of the China railway high-speed train (CRH2) and a two-level VSC of CRH3, are centered around 50 p.u. and 34 p.u., respectively. One will result in the high-frequency characteristic harmonic propagation and amplification though the catenary system. And the massive characteristic harmonics will distort voltage waveforms of both power system and catenary lines [3], [6]. Meanwhile, the multiple tractive conductors with the distributed capacitor will be resonant with the supply system [4]–[6]. Based on the literature and field test, these resonance frequencies, which range from 15 to 35 p.u., are the root of many insulation issues in HSRs. Therefore, harmonic resonance and high-order characteristic harmonics should be taken into account when designing a filter scheme. B. Mitigation Schemes for HSR There are three categories of technical methods utilized to deal with the two types of harmonic distortions. First, eliminate or reduce the harmonic currents generated by the nonlinear loads (NLLs) through the optimizing control strategy, control method, and parameter design method [10]. Second, harmonic filters (e.g., passive filter, active filter, and hybrid filter) are the common solutions used to reduce system impedance or compensate anti-harmonic currents for voltage distortion suppression [11], [12]. Third, optimize or modify the sensitive electrical parameters of the system to avoid global harmful resonance and offer a lower impedance path at resonance frequencies [6], [13]. The first category addresses the root of harmonic distortion caused by NLLs. Eliminating or reducing the harmonics injection of the NLLs is an effective way to achieve local harmonic suppression. This method, however, is not practical

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in many cases because of the wide frequency band of various NLLs. Meanwhile, resonance may be amplified to high level of harmonic distortions even though the NLLs' harmonic emissions comply with the standards. Moreover, the other methods have been adopted in many practical applications due to their economy and effectiveness of which the most frequently managed solutions are passive filters. The published papers dealing with passive filter design have focused on the following issues: • filter placement; • type selections and combinations of filters; • parameter design and optimization of filters. In traditional filtering methods, single-tuned and high-pass filters are widely adopted for mitigating harmonic current injections [11], [14], [15]. Single-tuned filters provide strong attenuation at a specific tuned frequency. However, these filters always introduce an additional parallel resonance point below the original resonance point. The high-pass filers, such as the firstand second-order filters, can be effective for filtering high-frequency harmonic components. However, the resistor, in series with a capacitor, also consumes kilowatts power loss. Few papers have discussed harmonic elimination for electrical railways. Brenna, et al. [16] proposed a filter at the interaction point between dc and ac railway systems. However, the harmonic features of the trains are not included, and the railways in many countries do not have such interconnection points, which make these filters relatively impractical. Moreover, the variations in the HSR system due to train organization may lead to potential harmful distortion issues, which have been rarely reported. Because of the harmonic features of HSR, the filters are required to damp varying resonance points and mitigate high-frequency harmonic components.

Fig. 1. Electrical traction system of an ESS and two supply phases.

C. Contributions This paper attempts to address the practical harmonic issues in China HSR by adopting C-type filters. Because of the time-varying positions, power demands, and harmonic spectra of trains, the C-type filter design is based on the field test and numerical data in key buses and trains. • The 95% maximum index of field measurements is adopted to determine the harmful harmonic distortion conditions (i.e., resonance and characteristic harmonics), and the information is used to make a mitigating scheme. • The resonance damping effect of the C-type filter is analyzed to select the parameters for an ac railway system. • A harmonic penetration program, taking into consideration the detailed train timetable in a 24-h period, is applied to verify the filtering results. II. HSR SYSTEM UNDER CONSIDERATION A. Traction Power-Supply System A typical traction power-supply system (TPSS) scheme in China HSR is shown in Fig. 1. The three-phase 220-kV utility is stepped down to two single-phase 2 27.5-kV feeders by a V/x tractive transformer in an electrical substation (ESS) to supply the all-parallel autotransformer (AT)-fed network. The ATs, installed in the AT substation (ATS) or section post (SP), are distributed along the track at about 10–15 km. The trains running

Fig. 2. Train timetable and topology model of TPSS for HPA in an hour.

on the tracks are the main harmonic sources that result in harmonic distortions through the overall system. An ESS offers four feeders for the uptracks and downtracks of each supply phase. The harmonic problems in ESS, which include time-varying and nonlinear features, differ from those of other industrial systems. As seen in Fig. 2, the information from the train timetable provides the positions of the trains and can determine the speeds, loading levels, and harmonic spectra of the running trains during the entire operation. B. Harmonic Current Penetration Fig. 3 shows a typical current spectrum of a CRH380A train, and Fig. 4 shows the statistical harmonic contents of the secondary-side voltage of the tractive transformer in ESS during a 24-h profile of measured data. Instead of providing the 24-h profile of harmonic results, the single index showing the average value or the value that is not exceeded by 95% of the entire time (called 95% index) [17] is adopted as the key standard for assessing mitigating results. The voltage distortion conditions in Figs. 3 and 4 can be classified into two categories: one is the characteristic harmonic

HU et al.: PASSIVE FILTER DESIGN FOR CHINA HSR

Fig. 3. Measured mean current harmonic contents of China's HSTs when at full 127.3 A, 3.14%). load during a four-second window (

Fig. 4. Measured catenary voltage harmonic contents of ESS in a 24-h period 27.5 kV): (a) resonance band and (b) characteristic switching band. (

band (e.g., 45th–55th order) and the other is the resonance harmonic band (e.g., 23rd–25th order). The former one depends on the typical spectrum of the trains that are made up of the dominant harmonic components, and cannot be completely mitigated. The most useful way to mitigate these harmonics is to supply apparent low-impedance paths near these high frequencies. The resonance harmonic band results in the occurrence of the resonance point over the entire system. If the resonance points are damped or transferred, the sideband harmonics will be reduced accordingly and will not be a problem. III. HARMONIC MODELING AND ASSESSMENT The train timetable shows the variations of the numbers, positions, and power demands of the running trains with time. It results in time-varying harmonic distortions of the entire system. Therefore, the dynamic HPA and statistical harmonic indices should be considered to cover multiple operation conditions. The following comments should be included in the HPA method for such conditions. 1) The utility power system is assumed as a pure sinusoidal system without background harmonics, and can be equivalent to a Norton circuit, which consists of a constant fundamental current and a short-circuit impedance in the frequency domain which can be calculated from system capacity. 2) The ESS transformer, a symmetric V/x type, is represented by the ideal transformer connected in series with the re-

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sistor and leakage inductance of primary and secondary windings [6]. 3) The all-parallel 2 27.5-kV AT-fed network is modeled as PI-distributed ten-port transmission lines [4], [6], that is, uptrack T-lines (including contact wire and catenary wire), F-lines (feeder wire), downtrack T-lines, F-lines, and R-lines (including rails, integrated grounding lines, and protective lines). The long line and skin effects are also considered. The lengths of each part are determined by the slides (the sections of the locations of ATSs, trains, SPs, etc.). 4) ATs along the catenary are modeled as 1:1 ratio transformers with a midpoint with the leakage impedance connected to the rails. 5) The trains are modeled as the Norton model by using the mean measured current spectrum described in [6]. Meanwhile, the equivalent impedance of the Norton circuit is represented by the leakage impedance of the locomotive transformer. In order to evaluate the most probable severity harmonic distortions caused by running trains, all of the trains are assumed to be at full load. This assumption will simplify the calculation procedure of train modeling. The only information required is the positions of the trains, which can be directly obtained from the train timetable. The results will be accurate, because the trains' individual harmonic injections are relatively fixed under different operations [3]. The typical harmonic spectrum can also be found in Appendix A. The test system takes into consideration the full traction phases for evaluating the synthesis of the harmonic distortions of three phases of the primary system. As a result, the th harmonic injection can be solved through the following formula [18]: (1) where is the harmonic injection vector; is the system nodal admittance matrix, and is the voltage response vector. At a specific time, the topology of the TPSS is determined and can be computed from the train timetable. This information is used for the HPA program and to further evaluate the harmonic distortions during the time. The HPA program, under the Matlab environment, is used to compute voltage distortions of key buses (e.g., ESS, ATS, and SP) determined with or without installing filter units. The results calculated from each configuration are applied to be the basis for making a filtering scheme. Because of the time-varying nature of the TPSS, this paper does not present results of a “case study” for a particular field condition. The various results are based on computer modeling of different TPSS operations of the train timetable. This makes it possible to draw more general conclusions about the effect of the method dealing with filter design for HSR. IV. FILTER UNIT DESIGN FOR HSR A. Filter Types and Characteristics In recent years, active filters have emerged as an efficient solution for addressing harmonic problems. However, in many

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It should be mentioned that the first-order filter has the best performance in mitigating high-order harmonics. B. Damped Filter Parameters Design

Fig. 5. Impedance results by installing different filters. Power loss: (a) 3.85 kW, (b) 3.84 kW, (c) 13.55 W, (d) 0.02 W, and (e) 0 W.

cases, passive filters are considered to be a simple, reliable, and cost-effective solution for harmonic control. Therefore, in cases where the harmonic distortion is not excessive, well-designed shunt passive filters are widely adopted in many industrial systems due to their simple construction and economy [14], [15]. Moreover, the stability and reliability of the passive filter are other important advantages which are the primary consideration of China HSR. Thus, for HSR lines, the purpose of harmonic filter planning is to reduce the harmonic pollution in the primary system (220 kV in China) and to diminish the harmonic distortion, and to avoid the potential harmful resonance in TPSS, which ensures that the equipment can operate correctly with power factor correction, while operational constraints are met. The damping for harmonic resonance is the key factor of resonance control, and must be included in filter design and optimization. Moreover, the high-order harmonics will propagate through the low-impedance path when the filter has enough capacitance. The filter is also designed to suppress the characteristic harmonic contents of the HSTs, actually, such as the 45th–55th orders. The impedance results under different filter installations show that the filters have the same and compensate reactive power. Also, the filters are all tuned to the resonance frequency. As seen from Fig. 5, it is clear that: 1) the third-order high-pass and single-tuned filters have introduced additional resonance points and 2) the first- and second-order high-pass filters have shown comparative damping results at resonance and high frequencies. Unfortunately, these filters also produce more fundamental power loss and cannot be tuned at a specific frequency that damps the resonance amplification. Thus, the C-type filter has the best filtering performance, and the resonance amplification is also reduced adequately. Meanwhile, the C-type filter does not introduce any power loss and provides a low-impedance path for tuned and high frequencies.

The first-order filter consisted of series and . The secondorder, third-order, and C-type filters are derivatives of the firstorder one, because they are composed of either the branch or LC branch [19]. Among the aforementioned damped filters, these filters can be designed to address the specific harmonic issues of HSR mentioned earlier. The advantage of the C-type filter is mainly that it can be tuned at a specific frequency and eliminate the power loss through the resistor. In such cases, the capacitor is sized for the compensatory required reactive power. Meanwhile, and are tuned at the fundamental frequency that bypasses the parallel in order to eliminate the filter's kilowatt losses. Moreover, is designed with to provide a low-impedance path at high frequencies. For most operation conditions, fewer than two trains run at two supply phases. As mentioned in [5] and [6], the resonance frequencies of the entire system consist of those of each independent phase as a result of their weak coupling in the substation. The filter units are independently designed for each supply phase. As a consequence, the reactive power compensation is below the single train's reactive power consumption. (2) denotes the rated fundamental voltage of T-R, and where is the fundamental angular frequency. The assumption is made to consider the 99.5% power factor of the CRH380A-type train at full power 9.6 MW. In order to avoid overcompensation under most operation times, should satisfy

(3) In each C-type filter, we assume since the filter unit in one supply phase needs a double filter (an ESS has two supply phases). It will be described in the following subsection. To eliminate fundamental power loss through and are tuned to the fundamental frequency (4) The C-type filter is tuned to the system resonance frequency, and (5) Let (5) divide (4), yielding (6) With different capacitances, the resulting resonance frequencies and costs should be considered to achieve the best mitigation performance with minimum cost. The varying resonance frequency should be kept at a safe zone.


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Fig. 6. Topology of the C-type filter and impedances of the system. Fig. 7. Filtering results determined by different

.

C. Resonance Damping Analysis of the filter involves and affects The shunt capacitor the original resonance point. Meanwhile, the resistor works as a damping resistor that shows good performance in mitigating resonance amplification. Taking into consideration the impedance-frequency curve obtained by the frequency scan at the T-bus of ESS, the equivalent circuit topology is shown in Fig. 6. The driving impedance has a resonance point and the C-type filter is also tuned at this frequency. The admittance of the shunt filter is obtained in (7). And

(7)

in , when at the resonance frequency, approaches the maximum value, and, thus, reaches the minimum value. At this time, it is possible to obtain the best resonance damping performance. However, the resonance will be transformed at the cross point of the filter impedance and system impedance. Fortunately, this resonance is directly damped by the if the impedance of is higher than that of the LC branch in order to attenuate the interaction between the LC branch of the filter and the impedance of the system at the new resonance point. In order to control the magnitude of the resulting resonance point, is designed as at

(12)

Alternatively, near and above the switching frequency, the LC branch is bypassed by , the C-type filter is equivalent to the first-order filter and, hence, (8) can be updated as

Thus, the system transmittance is derived as (8) This product reflects the mitigation levels of each harmonic, and we assume , then

(13) is inversely proportional to the The formula means that damp high-frequency harmonics. In order to emphasize the damping effect, should satisfy near

(9) Assume the equivalent impedance . Equation (8) is then expressed as

(10) This term denotes the voltage response ratio between before and after installing the C-type filter. Near the tuned resonance frequency (also the resonance frequency) and yield (11) The resonance damping is mainly determined by . The product can be regarded as the damping impact of the filter at the resonance frequency. As seen in (9), divide

(14)

at the Therefore, can be set near or slightly below resulting resonance frequency. In this case, can be sized by 90–150 . The power loss through is composed of a fundamental power loss and harmonic power loss, where the fundamental power since and are tuned at the fundamental frequency that bypasses . In fact, the harmonic power loss is the distortion power from the fundamental power but it does not increase the additional power loss. The harmonic power loss is not included in this paper. Thus, the power loss will be free for C-type filters. Considering the driving impedance at the T-bus of ESS, the impedance at the resonance frequency reaches 14 k . When is selected to 100–200 , the resonance magnitude is strongly attenuated below 400 , and the resonance frequency is then shifted to 15–17 p.u. The harmonics near the switching frequency (47–53 p.u,) are also damped. At the resonance frequency and higher frequencies, with the increase of , the damping effect at the resulting resonance frequency is degraded. Thus, – will be the suitable value dealing with harmonic resonance and characteristic harmonics.

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Fig. 9. Filtering results when filters are installed at different locations. Fig. 8. Filter unit design for the AT-fed system.

D. Filter Unit Design As discussed before, The C-type filter has good suppression at the tuned frequency and does not provide a parallel resonance point. Moreover, it is applicable to randomly varying loads, such as the high-speed trains, because it offers lower power losses and mitigates high-order characteristic harmonics. Therefore, this filter topology is adopted for further harmonic mitigation for a 2 27.5-kV AT-fed system of China HSR. For an all-parallel AT-fed system, the symmetry is a very important characteristic that keeps a 1:1 ratio for the autotransformers. This so-called filter unit is designed for the AT-fed system shown in Fig. 8. The filter unit contains two symmetrical damped harmonic filters (DHFs), a linkage protection switch (LPS), a data-collection system, and current sensors (CSs). The data-collection system measures and calculates the currents through the DHF and voltages across the AT. The voltage signals of the AT are measured from the ATS or SP so that it is not necessary to install an expensive PT. If the currents (i.e., ) though the capacitors measured by the CSs exceed the limits of the IEEE 18 standard (which will be described in Section V-C), the LPSs will turn off in order to protect the filter unit. When the distortions from the voltage signals (i.e., ) occur, the LPS will be reclosed. The limitation of the capacitor current can be set by considering the system's capacity and current limitations. Similarly, if no trains are running on the tracks, the LPS can also be turned off, because the harmonic components of the AT exceed the limitation that had been set for implementing the filter unit. E. Placement of the Filter Unit Only limited available positions can be selected to place such a filter unit, such as T and F buses in ESS, ATS, or SP. In order to measure the filtering results of different placements of the C-type filter, the T and F bus in ESS are the key buses because they are directly connected to the primary system. Meanwhile, the filter unit installed in ESS can be effective for reducing the harmonic injection to the primary power system. Thus, together with considering the results in Fig. 9, ESS will be the better choice for placing such filters. That is because the harmonic currents produced by the trains are propagated to the power system, and the filter acts as the lower impedance path, as shown in

Fig. 10. System description of an HSR line.

Fig. 9. Alternatively, if the filter unit is also designed for mitigating overvoltage when the train passes through the neutral section between adjacent supply phases, the SP will be the better choice. V. FULL CASE STUDIES A. System Descriptions Considering a typical China HSR line, the two supply phases of an electrical substation (ESS) are supplied by a V/x transformer, shown in Fig. 10. The transformer in ESS is a V/x type, which is stepped down 220 kV to double 2 27.5-kV feeders to the supply and phases, respectively. The lengths of the two supply phases are also included since the resonance frequencies of each phase are almost independent. The parameters of the test system can be found in Appendix B. The ESS is the main and intermediary unit between the traction system and the connected utility system. With considering the harmonic spectra of the HSTs and the statistical harmonic contents in the substation, the mitigation scheme is then issued. The filtering performance is evaluated by using the international standards (e.g., IEC 1000-3-6 and IEEE 519 standards, and the State standard GB14549 in China). The limits are 1.5% for THD and 1.0% for individual harmonics. For GB, the limits are 2.0% for THD, 1.6% for odd harmonics, and 0.8% for even harmonics. Fig. 11 shows the measured total harmonic distortion of voltage (THDV) of the key buses at 220 kV and 27.5 kV and the power demands of ESS during the time period of the HSR test run in April 2013. The THDV of the B-phase at the primary system sometimes exceeds the 2% limit of GB. The THDV of the T bus at ESS almost exceeds 10%. By performing HPA with a train timetable, we have calculated the 95% indices of


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TABLE I FILTERING RESULTS UNDER DIFFERENT CASES

at those frequencies and have enough damping to mitigate the resonance amplification or eliminate the resonance. Fig. 11. T bus of the ESS field test before the HSR was adopted: (a) THDV of the T bus voltage at 27.5 kV. (b) THDV of the B-phase voltage at 220 kV (2 times); the limit for (b) is 2%.

Fig. 12. The 95% maximum voltage distortions during 24-h operation profile by simulations: (a) three phase of the 220-kV system and (b) T-bus of the 27.5-kV system (resonance frequency 24–27 p.u.).

the harmonic contents for primary and secondary buses, shown in Fig. 12. As seen in Fig. 12, compared to the typical spectrum of the modern train shown in Fig. 3, the harmonic distortions are the 24th–27th order (resonance band) and the 45th–55th order (characteristic harmonic band). When considering a passive filter, at high frequency ( 45 p.u.), the filter should offer a low-impedance path to filter characteristic harmonics. While at resonance frequencies (24–27 p.u.), the filter should be tuned

B. Filtering Results Comparison As seen from the filtering results from adopting an optimal C-type filter installed in the ESS, the resonance magnification is strongly damped under approximately one-tenth of the resonance magnification without a filter. Moreover, the characteristic harmonics have also been mitigated. However, as a consequence, the characteristic harmonics around 50 p.u. have become a significant concern if further elimination is required. Then, the total capacitor size of the filter unit is determined. The available filter topologies and combinations for such a TPSS are listed as follows: Case 1) single-tuned filter at 50 p.u.; Case 2) first-order high-pass filter; Case 3) second-order high-pass filter tuned at 24 p.u.; Case 4) third-order high-pass filter; Case 5) C-type filter tuned at 24 p.u. Under different conditions, the 95% indices of THDVs are presented in Table I. The first-order filter has the best filtering performance among five individual filters. This filter also has a better damping effect on high-order harmonics. However, the kilowatts power loss is the main concern. The costs of all filters are approximately the same because they have the same compensation reactive power which occupies the major part of the entire cost. As shown in Fig. 13, the 95% index of the resonance and switching frequency harmonics after installation of C-type and first-order filters has been effectively attenuated. Compared to other filters listed in Table I, C-type filters have better mitigation performance on resonance and high-order characteristic harmonics. It should be mentioned that C-type and first-order filters can both be effective at mitigating the distortion conditions of the TPSS. As mentioned earlier, the C-type filter has a better damping effect on resonance than that of the first-order filter. C. Filter Operations Check Filter units are susceptible to failures and even breakdown if the voltage or current exceeds the limitations. Therefore, IEEE Standard 1531 [21] and ANSI/IEEE Standard 18 [22] “shunt power capacitors” were sponsored for checking the continuous operation under the contingency system and bank conditions,

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Fig. 14. RMS voltage profile of the T bus at SP during 24 h.

VI. FURTHER FILTER OPTIMIZATION

Fig. 13. The 95% maximum harmonic contents of the three-phase primary power system: (a) C type. (b) First-order filter.

TABLE II CONSTRAINTS OF IEEE STANDARD 18

and they must be able to withstand several factors. Mostly, the 95% indices and the IEEE limits are compared in Table II. In most cases, the filter unit works under safe configurations, and the filtering results meet the limits. Meanwhile, considering the previously listed limitations, the LPS of the filter unit is applied to ensure that the filter works under the acceptable distorted environment. Some of the limits are specified by the China Railway Bureau and the State Grid Corporation to ensure normal supply safe voltage for the pantographs of the trains. The fundamental voltage of the centenary system (T bus) should be below 29 kV and above 17 kV. A voltage profile taken during a 24-h time period is presented in Fig. 14. The centenary voltages of the SP meet the requirement during a 24-h period, and the voltage has been boosted a little. To reduce power loss, it is very useful to boost the supply voltage and control it below the limit voltage (29 kV).

The process of filter optimization is the process by which the best or optimum parameters of the filter are selected in order to obtain the best system performance. The objective here is to address resonance harmonics and characteristic harmonics. On the one hand, the potential harmful resonance frequency should be shifted out of the potential harmonic source (especially the characteristic harmonics) and used to damp the resonance amplification. However, the system parameters cannot be easily adjusted. At this time, the harmonic filter installed is required to control the harmonics, and the parameters are further used to adjust for achieving better optimization performance. Resonance sensitive indices can be effective for shifting the harmful resonance frequency and reducing the resonance magnitude. Sincethe space is limited, the resonance frequency/magnitude shift procedure is not included here and can be detailed in [23]. On the other hand, the filter offers a low-impedance or highpass path for characteristic harmonics to control these harmonic components under the required levels. Moreover, if the loworder harmonics such as the 3rd-, 5th-, and 7th-order harmonics need to be eliminated, a set of single-tuned filters can be composed to the C-type filter. This work has been studied in many published papers [11], [14]. The combinations and effects of those filters should be considered. VII. CONCLUSION The voltage distortions of the catenary system in ESS caused by HSTs are compared with the typical current spectrum of the trains. The harmonic causes of HSR, for example, harmonic resonance and massive characteristic harmonics, are then determined. The 95% indices of harmonic results calculated by HPA, including the train timetable, are utilized to compare the performances of available passive filters. The C-type filter is selected and designed to address such harmonic problems based on the resonance damping analysis. The filter unit based on the C-type filter is then developed for a typical 2 27.5-kV AT-fed system in China. Comparing the suppression results and costs, the designed filter unit can be effective to address harmonic resonance and high-frequency characteristic harmonic issues. Moreover, the HPA program by considering the train timetable can be further developed to evaluate and forecast power demands and potential power-quality issues for optimizing the train schedule


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TABLE III TYPICAL HARMONIC SPECTRUM OF CRH380A-TYPE HST (FOR ONE UNIT)

TABLE IV ELECTRICAL PARAMETERS OF THE TEST SYSTEM

Fig. 15. Geometrical layout of traction lines of the test system: IGL—integrated grounding line; PW—protection wire; MW—messenger wire; CW—contact wire.

APPENDIX B SIMULATION SYSTEM PARAMETERS TABLE V TRACTION LINES PARAMETERS

The parameters of the test system and tractive conductors are shown in Tables IV and V. The geometrical layout of traction lines is shown in Fig. 15. The calculation of the electrical parameters can be found in [6] and [24]. REFERENCES

and checking the operations of the filter unit and TPSS in an HSR line.

APPENDIX A TYPICAL HARMONIC SPECTRUM OF CRH380A HST The measured harmonic spectra of the HST at full load under tractive mode is shown in Fig. 3 and listed in Table III. And this harmonic spectrum can be used for harmonic penetration analysis of the traction power system for China HSR. The leakage impedance of the locomotive transformer is (at 25 kV for one unit).

[1] A. Iagar, G. N. Popa, and I. Sora, “Analysis of electromagnetic pollution produced by line frequency coreless induction furnaces,” WSEAS Trans. Syst., vol. 8, no. 1, pp. 1–11, 2009. [2] P. Pinato and D. Zaninelli, “Harmonic disturbances in electric traction system overhead lines,” in Proc. IEEE 10th Int. Conf. Harmonics Qual. Power, Oct. 2002, pp. 748–753. [3] G. W. Chang, H. W. Lin, and S. K. Chen, “Modeling characteristics of harmonic currents generated by high-speed railway traction drive converters,” IEEE Trans. Power Del., vol. 19, no. 2, pp. 766–773, Apr. 2004. [4] H. Lee, C. Lee, and G. Jang, “Harmonic analysis of the Korean highspeed railway using the eight-port representation model,” IEEE Trans. Power Del., vol. 26, no. 2, pp. 979–986, Apr. 2006. [5] A. Dolara, M. Gualdoni, and S. Leva, “Impact of high-voltage primary supply lines in the 2 25 kV 50 Hz railway system on the equivalent impedance at pantograph terminals,” IEEE Trans. Power Del., vol. 27, no. 1, pp. 164–175, Jan. 2012. [6] Z. He, H. Hu, Y. Zhang, and S. Gao, “Harmonic resonance assessment to traction power-supply system considering train model in China highspeed railway,” IEEE Trans. Power Del., vol. 29, no. 4, pp. 1735–1743, Aug. 2014. [7] M. P. Kazmierkowski and L. Malesani, “Current control techniques for three-phase voltage-source PWM converters: A survey,” IEEE Trans. Ind. Electron., vol. 45, no. 5, pp. 691–703, Oct. 1998.

514


[8] S. Liang, Q. Hu, and W. J. Lee, “A survey of harmonic emissions of a commercially operated wind farm,” IEEE Trans. Ind. Appl., vol. 48, no. 3, pp. 1115–1123, May/Jun. 2012. [9] F. Wang, J. L. Duarte, M. A. M. Hendrix, and P. F. Ribeiro, “Modeling and analysis of grid harmonic distortion impact of aggregated DG inverters,” IEEE Trans. Power Electron., vol. 26, no. 3, pp. 786–797, Mar. 2011. [10] Y. W. Li, “Control and resonance damping of voltage-source and current-source converters with LC filters,” IEEE Trans. Ind. Electron., vol. 56, no. 5, pp. 1511–1521, May 2009. [11] A. B. Nassif, W. Xu, and W. Freitas, “An investigation on the selection of filter topologies for passive filter application,” IEEE Trans. Power Del., vol. 24, no. 3, pp. 1710–1718, Jul. 2009. [12] Q. Liu, L. Peng, Y. Kang, and S. Tang et al., “A novel design and optimization method of LCL filter for shunt active power filter,” IEEE Trans. Ind. Electron., vol. 61, no. 8, pp. 4000–4010, Aug. 2014. [13] S. L. Varricchio, N. Martins, and L. T. G. Lima, “A Newton-Raphson method based on eigenvalue sensitivities to improve harmonic voltage performance,” IEEE Trans. Power Del., vol. 18, no. 1, pp. 334–342, Jan. 2003. [14] G. W. Chang, H. L. Wang, and S. Y. Chu, “A probabilistic approach for optimal passive harmonic filter planning,” IEEE Trans. Power Del., vol. 22, no. 3, pp. 1790–1798, Jul. 2007. [15] G. W. Chang, H. L. Wang, and S. Y. Chu, “Strategic placement and sizing of passive filters in a power system for controlling voltage distortion,” IEEE Trans. Power Del., vol. 19, no. 3, pp. 1204–1211, Jul. 2004. [16] M. Brenna and F. Foiadelli, “Analysis of the filters installed in the interconnection points between different railway supply systems,” IEEE Transs Smart Grid, vol. 3, no. 1, pp. 551–558, Mar. 2012. [17] D. Salles et al., “Assessing the collective harmonic impact of modern residential loads—Part I: Methodology,” IEEE Trans. Power Del., vol. 27, no. 4, pp. 1937–1946, Oct. 2012. [18] N. R. Watson, T. L. Scott, and S. J. J. Hirsch, “Implications for distribution networks of high penetration of compact fluorescent lamps,” IEEE Trans. Power Del., vol. 24, no. 3, pp. 1521–1528, Jul. 2009. [19] M. A. Zamani et al., “C-type filter design based on power-factor correction for 12-pulse HVDC converters,” in Proc. IEEE 34th Annu. Conf. Ind. Electron., Nov. 2008, pp. 3039–3044. [20] D. Bohaichuk, C. Muskens, and W. Xu, “Mitigation of harmonics in oil field electric systems using a centralized medium voltage filter,” in Proc. 9th IEEE ICHQP, Oct. 2000, pp. 614–618.

[21] IEEE Guide for Application and Specification of Harmonic Filters, IEEE Standard 1531-2003, Nov. 2003. [22] IEEE Standard for Shunt Power Capacitors, IEEE Standard 18-2002, Oct. 2002. [23] H. Hu, Z. He, Y. Zhang, and S. Gao, “Modal frequency sensitivity analysis and application using complex nodal matrix,” IEEE Trans. Power Del., vol. 29, no. 2, pp. 969–971, Apr. 2014. [24] M. Brenna, F. Foiadelli, and D. Zaninelli, “Electromagnetic model of high speed railway lines for power quality studies,” IEEE Trans. Power Syst., vol. 25, no. 3, pp. 1301–1308, Aug. 2010.

Haitao Hu (S'13) received the B.Sc. degree in electrical engineering from Zhengzhou University, Zhengzhou, China, in 2010 and is currently pursuing the Ph.D. degree in electrical engineering at Southwest Jiaotong University, Chengdu, China. From 2013 to 2014, he was a Visiting Doctoral Scholar at the University of Alberta, Edmonton, AB, Canada. His main research interests are power quality and harmonics of electric traction systems.

Zhengyou He (M'10–SM'13) received the B.Sc. and M.Sc. degrees in computational mechanics from Chongqing University, Chongqing, China, in 1992 and 1995, respectively, and the Ph.D. degree in electrical engineering from Southwest Jiaotong University, Chengdu, China, in 2001. His research interests include signal processing and information theory applied to electrical power systems, and the application of wavelet transforms in power systems.

Shibin Gao received the B.Sc., M.Sc., and Ph.D. degrees in electrical engineering from Southwest Jiaotong University, Chengdu, China, in 1986, 1999, and 2006, respectively. Currently, he is the Chair Professor in the College of Electrical Engineering at Southwest Jiaotong University. His research interests are the protection and control of electric traction systems.