相关报告专利软著-v27.16revision of manuscript-16pesgm1123

1、A Practical Real-Time Hybrid Simulator for Large er erfacing and External Transient Shuqing Zhang, Yanan Zhu Department of Electrical Engineering Tsinghua UniversityBeijing, Kaijian Ou, Qi Guo, Yun Hu, Wei er Research China er Guangzhou, Since the year 1988, scientists have begun to do research on e

2、lectromechanical and electromagnetic hybrid simulation 1- 2. Nowadays, there are several mainstream hybrid simulation platformssessing value of practical application. RTDS company has launched the frequency depended network equivalent (FDNE) method and app d itohybrid simulation, by which the simula

3、tion scale has been expended 3-4. However, it cant break the restriction of the system scale totally which results from the heavy compu ion burden and complexity of the FDNE method 5. China Electrical er Research Institute has developed the advanced digitaler system simulator (A Practical Real-Time

4、Hybrid Simulator for Large er erfacing and External Transient Shuqing Zhang, Yanan Zhu Department of Electrical Engineering Tsinghua UniversityBeijing, Kaijian Ou, Qi Guo, Yun Hu, Wei er Research China er Guangzhou, Since the year 1988, scientists have begun to do research on electromechanical and e

5、lectromagnetic hybrid simulation 1- 2. Nowadays, there are several mainstream hybrid simulation platformssessing value of practical application. RTDS company has launched the frequency depended network equivalent (FDNE) method and app d itohybrid simulation, by which the simulation scale has been ex

6、pended 3-4. However, it cant break the restriction of the system scale totally which results from the heavy compu ion burden and complexity of the FDNE method 5. China Electrical er Research Institute has developed the advanced digitaler system simulator (SS). Basing on the highly performed PC clust

7、er, theSS can handle the hybrid real time simulation of large-scale AC/DCer system 6. But meanwhile, the validation of electromagnetic ms and algorithms for HVDC lines and apparatus,er electronic are stilder discus. And the conventional way it takes to deal witherface betn electromagnetic and electr

8、omechanical sub-systems will bring inevitable errors, eraction error, 0+ error and error caused by erface equivalen7.There are also some hybrid simulation methods based on PSCAD, which represent offlineEMT/TS hybridAbstractes sary to utilize electromechanical hybrid simulator to modern large HVAC er

9、 system, where multiple HVDC links oconcentrated load areas. In this r, a practical real-hybrid simulator is ed. The simulator makes RTDS external transient program running on a computer link together effectively and smoothly. The entire erface schemes for hybrid simulation are discussed on both alg

10、orithm and implemen ion layers. Aiming at the problem on unexpected low frequency non-characteristic harmonics, an angle circuit is employed, with fast calculation method. At last, based on a large case system China Southern Grid, the hybrid simulator is compared to the electromagnetic simulation on

11、 27 RTDS racks to validate verify the ed Index Termshybrid simulation，impedance algorithm and ion, RTDS and transient economy is so The surge in and tthe scale and complexity of the er system continued to soar. To satisfy the demand for electricitydistricts away from energy-generating centers, his r

12、, the principle and the implemen ion HVDC links are fed o modern HVAC er systems with concentratedloadstoefficientlydeliver required erenergy. Moreover, plenty of er electronic devi of large capacity and high voltage are put o use in modern er grids.of hybrid simulator ly discussed in .III presents

13、an impedance angle erface circuit, unexpected harmonics.ast,thesimulatoristestedby a case system of China Southern Grid (CSG).Among benefits of these technologies is the t we limited ways to research and simulate such kind CHEMES ON ALGORITHM systems both accura y and efficiently. The AC-DC combined

14、 er systems in the developed areas in China, such as Beijing, Shanghai and Guangzhou all call for the simulation tools which can describe the tightly coupled electromagnetic and electromechanical pro ses happening in the systems, and finely handle the diversity and complexity of the operation mode a

15、s well. However, those traditional simulation tools cant meet the demand. On this occa , the electromagnetic transient (EMT) and electromechanical transient (TS) hybrid simulation emerges as the times IONA. Basic Algorithm of EMT and TS Hybrid Fig. 1 lays out the overall scheme of the ed and TS hybr

16、id simulator. In the hybrid simulation, an entire HVAC and HVDC er system is partitioned at the AC buses of HVDC convertor transformers to split o two sub grids. Then the HVAC grid is simulated by the TS program, while the HVDC links by the EMT program. Comparing ThisworkpportedbytheNaturalScienceFo

17、undationother methods to partition the system, such as an area wi fault is in electromagnetic simulation and the rest is in the electromechanical simulation, this method is more practical.As Fig. 1 lays out, the hybrid simulator is comprised of three major components: RTDS, digital computer, and GTF

18、PGA communication card. RTDS is ready for precise emulation of HVDC links, and is well prepared for admisofphysical control and protection system. The self-developed TS program runs on a computer. It is capable of emulating largegrids in real time and sharing some computing time to communicate and k

19、eep synchronous with RTDS. At the beginning of eacheraction step,erface variables are transferred bilaterally betn the RTDS and computer. During eacheraction step, a variable denoting timing mark is transferred from the RTDS to computer. All communication and daransferring jobs are done by the GTFPG

20、A card 12 13, which supports two types of numbers: single preci float poAs one program is computing and solving its s, other methods to partition the system, such as an area wi fault is in electromagnetic simulation and the rest is in the electromechanical simulation, this method is more practical.A

21、s Fig. 1 lays out, the hybrid simulator is comprised of three major components: RTDS, digital computer, and GTFPGA communication card. RTDS is ready for precise emulation of HVDC links, and is well prepared for admisofphysical control and protection system. The self-developed TS program runs on a co

22、mputer. It is capable of emulating largegrids in real time and sharing some computing time to communicate and keep synchronous with RTDS. At the beginning of eacheraction step,erface variables are transferred bilaterally betn the RTDS and computer. During eacheraction step, a variable denoting timin

23、g mark is transferred from the RTDS to computer. All communication and daransferring jobs are done by the GTFPGA card 12 13, which supports two types of numbers: single preci float poAs one program is computing and solving its s, sub-system in the other part is expressed equivalent s. To obtain real

24、-time performance, parallel protocol is employed 1-2, and the EMT and TS parts exchangeerface parameters in parallel at a certain erval, which is always the same asegration step of The TS simulation, e.g. 10 milliseconds. We define erval To distinguish each sary for the float-poerval exactly, it var

25、iable to 10-which requires about 10-bit mantissa. Thus the rest 13-mantissa can only record 213 seconds, equivalently about 2.3 hours. It is undesirablet two simulation parts can keep synchronous for a little moren 2 hours in continual simulation and test. So we use aneger-type timing mark instead o

26、f float-poone. A double precivariable records the current simulation time in RTDS. It can be multip d by 100 and truncated to omit the decimal parts, and to get theeger-type timing mark, which denotes the number of 10-millisecond period the simulation has taken. By eger-type timing mark, it can be a

27、chievedt two simulation parts keep synchronous for about 5965 hours - 231 times 10 milliseconds.In each EMT simulation step, the RTDS visit buffer memory on the GTFPGA card and update the timing mark; once the TS program finishes calculation of the current step, it visits the same buffer memory and

28、fetches the timing mark. If it increases, the TS program will know new eraction step starts. Then both parts exchange the erface variables.Figure1.chemesforEMT/TShybridsimulationonalgorithmand implemen ion layershe TS program, the er grid is by a set of coupled sequence networks, and the er dynamic

29、elements, such as synchronous machines, are simply m ed and only coupled to the itive sequence HVDC systems are m ed as er sour 9 in three- sequence form. It has been fully discussed in 10 how the three-sequence fundamental er can be accura y extracted. At the beginning of each erface step, six er v

30、alues of each erface port are transferred from EMT side to T e.And the Thevenin equivalent voltage are here to characterize the AC system 1. Because the HVAC system he TS part mainly contains large er and voltage sour of great inertias, the Thevenin equivalent IMPEDANCE ANGLE ERFACE are widely used

31、in digital hybrid simulation. Thus, A. Impedance Angle Character within Low Frequency As Section II mentioned, in the EMT part of hybrid simulation, the erface equivalent branch only represents the port electrical character around fundamental frequency, instead of full frequency band. The most notic

32、eable problem is incorrect angle of the inner impedance of the equivalent voltage source, which mainly determines how fast the low frequency non-characteristic harmonics d . Here the beginning of eacherface step, six values of three- sequence fundamental voltage phasors are transferred from side to

33、EMT side. However, when simulating large er systems, there arises a major problemerface anderaction of both parts: irrational transient non-characteristicharmonicsduringsome In the EMT part of hybrid simulation, equivalent branch only presents the correct port carried out to illustrate the problem.

34、In character of the fundamental frequency, instead of full frequency band. Due to incorrect por ectrical character, the irrational transient non-characteristic harmonics sibly appear at the erface buses, which may be magnified fast during the transients and lead to incorrect actions of HVDC control

35、and protection system.hybrid simulation, the inner impedance is implemented as the traditional equivalent circuit (Fig. 2(a).B. Framework of RTDS and Computer Based Hybrid To implement the EMT and TS hybrid simulation, we employ RTDS and self-developed TS simulation program 11.Figureerfacecircuits(a

36、)originalone,(b)improvedWith non-linear ax,2 f mFigure3.Three-phasebusvoltagesoftheHVDCinvertertransformerandFFTresultsofthejR2 fX1 R2 jfX1g(f)(1)RCSG is a typical HVAC / HVDC er The CSG year 2011 m is employed as the case system, as Section IV shows. An instantaneous short-circuit fau isturbs the s

37、ystem near the inverter of one HVDC link during the period from 1 second to 1.1 seconds. Fig. 3 presents 3-phase voltages at the AC bus of the HVDC invertor transformer, yielded by the hybrid simulation. As we can see, the unexpected low frequency harmonics appear, and fail to decayfistheper unit fr

38、equency.We tR jfX k(X jfR),k SubstitutingoafterWith non-linear ax,2 f mFigure3.Three-phasebusvoltagesoftheHVDCinvertertransformerandFFTresultsofthejR2 fX1 R2 jfX1g(f)(1)RCSG is a typical HVAC / HVDC er The CSG year 2011 m is employed as the case system, as Section IV shows. An instantaneous short-ci

39、rcuit fau isturbs the system near the inverter of one HVDC link during the period from 1 second to 1.1 seconds. Fig. 3 presents 3-phase voltages at the AC bus of the HVDC invertor transformer, yielded by the hybrid simulation. As we can see, the unexpected low frequency harmonics appear, and fail to

40、 decayfistheper unit frequency.We tR jfX k(X jfR),k Substitutingoafter clearance of the disturbance. The FFTysis reveals t main components of the harmonics he frequency band, fromabout 100Hz to500As we know, the impedance of Thevenin equivalent 1R f 2dReX jf (dX eXg( f ) k X2 (fXis ed of and an indu

41、ctance in connection. The reactance increases fast and linearly with Xd (R R)R,e(1frequency while keeps constant. The ratio grows fast, which imp t the bus which the HVDC link connects to is not capable of ing the harmonics.From the research on HVDC project 14-15, reasonable values of the equivalent

42、 impedance angle spread in a certain range, which can be determined by bound values: h(f ) tan(arg(g( f ) f (dX ef 2dRand max . Thus, besides the fundamental impedance, the erface circuit is expected to character the impedance he frequency oflow-orderharmonics,To get the peak ofh(t), we calculate it

43、s dh(f ) (dX eB. erface Circuit and Its (eX f 2d( f 2dReXTo character the impedance angle, several ways are available. The most common one is to build the dependent he EMT side. However, it is one of So the peak of h(t) is obtained if eX f 2dR=0, most complicated methods. And it is not easy to acqui

44、re the reliable frequency dependent impedance. All in all, a practical method is required.1f f Thus a simply erface circuit is ed (1(R/ X)2approximate the equivalent impedance angle, as Fig. presents. X and X1 denote the t f fdh(f )/d f softheequivalent Thevenin.And we while f f dh(f)/d f 0. So h(t)

45、 gains the value when f =f . By (10) we can place theum of all, the fundamental frequency of two circuits should be the same. Since R, X can be obtained measure or from parameters of the for simulation, away from the frequency where abnormal harmonics t h(f ) goes below Furthermore, it is also avoid

46、able as f increases,bydecreasing LettingR1(1)R (01),wehavenon-linearOnce erface circuit form is improved, the same jR 2 1 R is carried out. Here is chosen as 2/3. Figure 4 shows the unexpected abnormal harmonics disappear.R2 R2 X jthe real-time electromagnetic simulator when regulating the direct cu

47、rrent ander, as Fig. 7 lays out.Figure4.Three-phasebusvoltagesoftheHVDCinvertertransformerand the FFT results of the voltageslitude and angle of the equivalent impedance are compared in Fig. 5. Thelitudes are similar, andonly show a little difference in higher frequency band. By contrast, the angle

48、after the modification the real-time electromagnetic simulator when regulating the direct current ander, as Fig. 7 lays out.Figure4.Three-phasebusvoltagesoftheHVDCinvertertransformerand the FFT results of the voltageslitude and angle of the equivalent impedance are compared in Fig. 5. Thelitudes are

49、 similar, andonly show a little difference in higher frequency band. By contrast, the angle after the modification deviates from the original obviously. The modification makes the impedance angle fall o the appropriate range. So the circuit is able to dnon-character harmonics fast, whichcoincides wi

50、ththe Figure 7. DC voltage, current erofB. Strict Contrastive Tests n the Hybrid and the Real-Time Electromagnetic Referring the results of RTDS real-time electromagnetic simulator as standard ones, we conduct the simulation of the transient and dynamic pro s by the hybrid simulator, considering the

51、 asymmetrical modes of operation and faults. and after the modificationVALIDATION BY COMPARING TO ELECTROMAGNETIC A. Contrastive Tests e of Hybrid n the Steady e and the At the moment the hybrid simulator Super Mixed Real Time (SMRT) transits from open-loop to closed-loop, the testing case comes to

52、the steady s e immedia y and smoothly, matching the initial steady s e setting exactly as well. Relative deviation of the nodal voltage of the whole systemis less n 0.02%, oftheDC erisless n 1MVA, not up to 0.1% relatively.Figure 8. The electromagnetic-electromechanical hybrid simulation The network

53、 structure of the test systemis presented in 8. The case system, an equivalent and simplified m according to the CSG system, includes the mainnetwork, parts of the 220 kV network and five HVDC lines. The electromagnetic sub-system, including five HVDC lines, calls for a 10-rack RTDS set computing in

54、 parallel. The red lines stand for 800 kV Yun-Guang HVDC lines, while the blue ones stand for Tian-Guang, San-Guang,-Zhao and Xing-An HVDC lines. The electromechanical sub-system, including 102 generators,116 loads,1207 lines and 536 nodes, calls for the TS program to compute.There is also an electr

55、omagnetic simulation Figure6.Three-phasevoltageofthe erfacebusattherectifierThe black line is the result from hybrid simulation, while the red one, which is regarded as the standard result, is the result from real-time electromagnetic simulation. As Fig. depending on RTDS for the same case system. T

56、hus we can test the hybrid simulator by comparing the results of the two types of simulation. The electromagnetic simulation m calls for a 27-rack RTDS set to compute in parallel.shows, waveforms of the voltage and othare essentially coincident when the case runs stably.By researching on the CSG yea

57、r 2011 m s as follows:, we can During the steady s e of the case system, we can get the highly compatible results of the SMRT hybrid simulator 1) During and after the fault, the waveforms of the phase voltage and rectifier and inverter es one of the most practical and gotten by the hybrid simulator

58、mostly agree with those gotten by the real-time electromagnetic simulator.solutions to simulate on modern large HVAC and systems accura y. A hybrid simulator based on RTDS and computer is sucsfully made, according to the procheme on bolgorithm and implemen ion layers.2) During the transient s produc

59、ed by faults, DC voltage, current er results of the two are consistent with each 3) By comparing the waveforms related to t during erface algorithm mainly includes AC / DC partitioning, three-sequence equivalent ing and n the two simulators, we can ty es one of the most practical and gotten by the h

60、ybrid simulator mostly agree with those gotten by the real-time electromagnetic simulator.solutions to simulate on modern large HVAC and systems accura y. A hybrid simulator based on RTDS and computer is sucsfully made, according to the procheme on bolgorithm and implemen ion layers.2) During the tr