1、 AbstractA centralized frequency regulation strategy of PV plant based on equal adjustable capacity proportion mode is proposed in this paper.When the system frequency changes due to some disturbances,the requirement of adjust active power value is calculated according to the frequency changing,then
2、 original active power reference is added with this adjust value to obtain the final active power reference as to change the active power output of PV units to participate in system primary frequency regulation.On this basis,in order to allow all PV units in same PV plant to coordinate with each oth
3、er,also to prevent some PV units from excessive regulation,a proportional regulation of power method(PROP)is implemented to allocate active power reference to each PV unit more reasonable,namely,each PV units output is according to equal adjustable capacity proportion.Finally,an actual PV plant mode
4、l is established on DIgSILENT PowerFactory platform to verify the effectiveness of the proposed control strategy.Index TermsPV plant,centralized frequency regulation,proportional regulation of power,DIgSILENT PowerFactory Manuscript received July 15,2018.This work was supported by the Natural Scienc
5、e Foundation of China under Grant 51607160,Research Program of State Grid Corporation of China(Study on active frequency and voltage control technologies for second level power disturbance in photovoltaic power plant),and Innovation Fund Program of China Electric Power Research Institute(NY83-17-003
6、).M.H.Qian,D.W.Zhao and D.J.Jiang are with Renewable Energy Research Centre,China Electric Power Research Institute(State Key Laboratory of Operation and Control of Renewable Energy&Storage Systems,Jiangsu Engineering Technology Research Center for Energy Storage Conversion and Application)(correspo
7、nding author:M.H.Qian,).J.Ma is with the School of Electrical and Information Engineering,University of Sydney;Sydney NSW 2006,Australia(e-mail:j.masydney.edu.au).M.S.Ding and L.Xiang are with State Grid Ningxia Electric Power Company Limited,Yinchuan 750001,China(e-mail:).I.INTRODUCTION n recent ye
8、ars,large-capacity photovoltaic(PV)power plants(hundreds of megawatts)have been built at home and abroad.Due to the characteristics of solar irradiance and the rapid development of PV power generation,the integration of PV power brings new challenges to power system stability analysis and control 1-
9、3.For example,a comprehensive demonstration project of renewable energy invested by China Minsheng Investment Co.,ltd in Ningxia(Yanchi)plans to build a PV power project with installed capacity of 2GW.The demonstration project covers an area of about 60 thousand mu and is the largest single PV power
10、 plant in the world by now.In order to make full use of renewable energy,the maximum power point tracking(MPPT)method is usually adopted in the existing wind and PV power generation systems.However,the demand of power system for frequency regulation of renewable power generation is increasing.Renewa
11、ble energy 4-8,energy storage system 9 and load sources 10-11 can all provide frequency support for power system.In China,the national standards 12-13 specify that wind farms and PV power plants need to have the ability to participate in power system frequency regulation.In Northwest power grid of C
12、hina,fast frequency response capability of the PV inverters was tested,and it is shown that the fast frequency response contribution of PV inverters is better than conventional thermal generators with the same capacity 5.With regard to the control strategies of renewable energy participating in prim
13、ary frequency regulation for power grid,more research is focused on wind power,while less research on PV.A centralized frequency regulation control system for PV power plants is designed in this paper taking PV power plants as a whole to participate in the system frequency modulation.When the power
14、grid frequency changes due to the system disturbance,a correction amount P is added to the original A Centralized Frequency Regulation Strategy of PV Power Plant based Equal Adjustable Capacity Proportion Mode Min-hui Qian1,Da-wei Zhao1,2,3,Jin Ma4,Da-jun Jiang1,Mao-sheng Ding5,Li Xiang5 1.State Key
15、 Laboratory of Operation and Control of Renewable Energy&Storage Systems(China Electric Power Research Institute),Nanjing 210003,Jiangsu Province,China;2.State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources(North China Electric Power University),Changping District,
16、Beijing 102206,China;3.Jiangsu Engineering Technology Research Center for Energy Storage Conversion and Application,China Electric Power Research Institute,Nanjing 210003,Jiangsu Province,China;4.University of Sydney,Sydney NSW 2006,Australia;5.State Grid Ningxia Electric Power Company Limited,Yinch
17、uan 750001,Ningxia Hui Autonomous Region,China I 2018 China International Conference on Electricity Distribution Tianjin,17-19 Sep.2018CICED2018 Paper No.201805280000292 Page1/5 1797 power command oldP to get the final power output value newP in order to change the active power output of PV modules
18、to participate in the primary frequency control of the system.Furthermore,active power distribution mode of solar power units based on equal adjusted capacity proportion principle is used to make the PV modules in the same power plant coordinate with each other and prevent a certain PV module from t
19、aking too much disturbance.This distribution mode allows the active power adjustment amount taken by the PV power plant to be reasonably distributed to each solar power unit,improving the accuracy of frequency regulation control.Finally,based on the DIgSILENT PowerFactory platform 14,the model of PV
20、 power system is built to verify the effectiveness of the proposed control strategy.II.CENTRALIZED FREQUENCY REGULATION STRATEGY The principle of the PV power plant frequency regulation control system is shown in Figure 1.The system selects frequency reference value(frequency target value)and the me
21、asurement value of the grid-connected point including active power,reactive power,voltage and frequency as input signals.When the grid frequency changes beyond the frequency regulation control dead zone,the frequency control system of PV power plant first calculates the adjustment of PV power plant
22、based on the deviation between the actual value and the target value of the frequency of the grid-connected point.This step is aimed at active power setting.Then,the frequency control system of PV power plant adjusts the active power output of each solar power unit according to PV power prediction i
23、nformation in real time until the grid frequency is restored to the target value.That is the power distribution process.PCCActive Power SettingActive Power DistributionPV inverter1PV_1PV inverter2PV_2PV inverternPV_nref_1Pref_2Pref_nPrefPPower Prediction InformationTemperature RadiancePCC PCC PCC PC
24、CP/Q/U/freff_2 _2 _2P/Q/U_1 _1 _1P/Q/U_n _n _nP/Q/U pdP Fig.1.Block diagram of PV power plant control principle When the active power setting system of the PV power plant detects that the difference between the measurement value and adjustment target value of grid frequency exceed the control dead z
25、one,it calculates the active power output value of the PV power plant according to the frequency deviation.The specific calculation method is as follows:P P*()ref meas ref meask f f=+(1)WhererefP is the reference value of the active power of the PV power plant;measP is the measurement value of the a
26、ctive power of the PV power plant;reff is the reference value of the frequency regulation system;measf is the measurement value of the frequency of the grid-connected point;k is the frequency-active regulation coefficient of PV power plant.Figure 2 shows the implementation of active power setting in
27、 centralized frequency regulation mode.11meassT+fmeasf-kf measPrefP Fig.2.Frequency controller III.EQUAL ADJUSTABLE CAPACITY PROPORTION MODE In order to synchronously increase or decrease the disturbance amount of each PV module to aviod the phenomenon that the active output of some PV modules has r
28、eached the limits but the active power of others can still be adjusted,the mode of equal adjustable capacity proportion(PROP)is adopted in this chapter,and the specific implementation is as follows:The adjustable capacity proportioniP of the ith PV module is defined as:maxmax min100%i BiiiiPPPPP=(2)
29、Where maxiP is the maximum output of the ith PV module;miniP is the minimum output of the ith PV module;BiP is the basic output of the ith PV module.In this mode,each PV module has the same adjustable capacity proportioniP.The range of iP is as follows:01iP(3)Then,according to the mode of equal adju
30、stable capacity proportion,assuming that there are n independent PV modules in the PV power plant,the adjustable capacity proportion of the PV modules satisfies the following relationship:max1 1 max 2 2 maxmax1 min1 max 2 min 2 max minB B n BnnnP P P P P PP P P P P P=(4)2018 China International Conf
31、erence on Electricity Distribution Tianjin,17-19 Sep.2018CICED2018 Paper No.201805280000292 Page2/5 1798 When the minimum output of the ith(1,2,n)i=PV module is min0iP=,then the formula(4)can be transformed into:12max1 max 2 max1 1 1Bn BBnP PPP P P=(5)Simplify the formula(5)to obtain:12max1 max 2 ma
32、xBn BBnP PPP P P=(6)Assume that the total active output of the PV power plant before the disturbance occurs is oidsP,the active output of the ith PV module isoldiP,and the sum of the maximum active outputs of PV modules is max sP.The amount of power change undertaken by the ith PV module isiP.iP is
33、the power adjustment command given by the coordinated control system.The total power change assumed by the PV Plant issP,then the following constraints can be obtained:1212max1 max 2 max maxold old oldn oldsnsnsP P P PP P P PP P P P+=+=+=(7)The formula(7)can be expressed as:1 1 2 2max1 max 2 maxold
34、old oldn nnP P P P P PP P P+=(8)Therefore,it can be solved by equation(8):()max 22 1 1 2max1old oldPP P P PP=+(9)According to this method,the relationship between1P and the power variations assumed by other PV modules in the PV power plant can be obtained in turn,and the relationship between 1P and
35、sP can also be obtained:()max11max1ss old oldsPP P P PP=+(10)Then,the power adjustment command issued by the coordinated control system to the 1th PV module is:()max111maxolds s oldsPP P P PP=+(11)Similarly,it can be concluded that the power adjustment command received by the ith PV module is:()maxm
36、axii olds s oldisPP P P PP=+(12)IV.SIMULATION A.Construction of the Simulation Model In this chapter,a two-area four-machine system based on PowerFactory platform 14 including 4 generators and 11 busbars is built.The system model is shown in Figure 3.420.201.01-16.99320.601.03-6.8011231.901.01-13.42
37、10226.200.98-23.739223.410.97-32.158218.180.95-18.557221.030.96-4.69220.201.0110.506224.970.983.725231.481.0113.80120.601.0320.26Shunt/Filter(1)-0.00-330.24 Shunt/Filter0.00-184.70 2-Winding.-700.00-102.6478.112-Winding.700.00185.0078.11L91767.00100.00 2-Winding.-700.00-115.3580.15 2-Winding.700.002
38、02.0880.152-Winding.-719.00-89.9279.852-Winding.719.00176.0079.85Line(7)-706.0834.9745.11Line(7)719.0089.9245.11Line(6)-1385.57123.0589.87Line(6)1406.0880.3889.87Line(5)195.41-24.3213.03Line(5)-190.7253.6013.03Line(4)195.41-24.3213.03Line(4)-190.7253.6013.03Line(3)199.946.0713.06Line(3)-195.1524.301
39、3.06Line(2)200.476.1513.10Line(2)-195.6824.3313.10L7967.00100.00 GG4700.00202.0880.95GG3719.00176.0082.25GG1700.00185.0080.45Line(1)1387.71128.9389.42Line(1)-1367.4172.4889.422-Winding.-700.08-145.6481.232-Winding.700.08234.7281.23Line700.00102.6444.13Line-687.6316.7144.13GG2700.08234.7282.04DIgSILE
40、NT Fig.3.Two-area four-machine system based on PowerFactory platform In order to facilitate the study of the operating performance of the PV power plants participating in the system frequency regulation control,large-scale PV power plants are integrated to Bus08 and Bus09 in the classic two-area fou
41、r-machine system.Specifically,four PV plants are integrated into Bus08 whose installed capacity are 200MW(Plant I)、100MW(Plant II)、200MW(Plant III)、200MW(Plant IV)and two PV power plants with installed capacity of 400 MW(Plant I)and 400 MW(Plant II)are integrated into Bus09.In order to analyze and c
42、ompare the difference between the centralized frequency regulation control mode and the decentralized frequency regulation control mode,two PV plants under Bus08,Plant I with 8 feeders and Plant II with 4 feeders,are selected to set up in detail in the modeling process.It can be shown in Figure 4.T2
43、_Plant III0.31.0 23 2.3T1_Plant III0.31.0 23 2.3T35_Plant III3 5.21.0 0-1.035kV collect Plant.3 4.50.9 9-1.4110kV POI(Plant III)2 2 8.10.9 9-4.0092 2 7.90.9 9-4.5110kV POI(plant II)2 2 7.90.9 9-4.3110kV POI(Plant I)2 2 7.90.9 9-4.1TI-1.3 5.91.0 31.7TI-1.3 5.91.0 31.7TI-1.3 5.91.0 31.735kV collect Pl
44、ant II3 4.10.9 80.535kV collect Plant I3 4.10.9 80.5TI-13 5.91.0 31.735kV Busbar(Plant II)/I 段3 4.835kV Busbar(Plant II)/II 段3 4.80.9 91.0TV-23 6.01.0 31.8TV-13 6.01.0 31.8TIV-23 6.01.0 31.8TIV-13 6.41.0 42.0TIII-23 6.41.0 42.1TIII-13 6.41.0 42.1TII-23 6.51.0 42.1TII-13 6.21.0 41.935KV 母线/I 段3 5.535
45、KV 母线/II 段3 5.51.0 11.42-W inding.41.6-1 6 2.62 8.30.4 1 81 6 2.9-2 0.42.7 4 61 6 2.9-2 0.42.7 4 6Line POI Plant I(.27.5-1 6 2.92 0.42.7 4 61 6 6.1-1 9.62.7 4 6V_Plant III-185.18 5.0-5.0177.98.V-01T_Plant III75.7-1 6 6.11 9.62.7 4 68 5.0-5.0177.98.8 5.0-5.0177.98.SVC Plant III 0.0-0.00.0 0 0Line(1)2
46、6.1-1 6 2.22 5.80.4 1 61 6 2.6-2 8.30.4 1 82-W inding.41.6-1 6 2.62 8.30.4 1 81 6 2.9-2 0.42.7 4 61 6 2.9-2 0.42.7 4 6Line(3)12.3-7 5.51 6.70.1 9 67 5.5-1 9.40.1 9 7Line(2)23.6-1 4 4.03 5.20.3 7 61 4 4.2-3 7.30.3 7 7Shunt/Fil.Shunt/Fil.2-W inding.78.7-7 5.51 9.40.1 9 77 5.7-1 2.71.2 9 87 5.7-1 2.71.
47、2 9 82-W inding.75.2-1 4 4.23 7.30.3 7 71 4 4.5-2 5.02.4 8 01 4 4.5-2 5.02.4 8 0SVC Plant II 0.00.00.0 0 0SVC Plant I 0.00.00.0 0 0B re aker/S.0.0 L3523(4)6.5-1 9.33.10.3 2 42 0.0-3.10.3 2 5B re aker/S.0.0 L3523(3)6.5-1 9.33.10.3 2 42 0.0-3.10.3 2 5B re aker/S.0.0 L3523(2)6.5-1 9.33.10.3 2 42 0.0-3.
48、10.3 2 5B re aker/S.0.0Line PO I Plant II26.0-7 5.71 2.71.2 9 87 7.3-1 2.31.2 9 8Line PO I Plant I49.6-1 4 4.52 5.02.4 8 01 5 0.5-2 3.52.4 8 0L3523(1)6.5-1 9.33.10.3 2 42 0.0-3.10.3 2 53 8.7-6.10.6 4 9BK_35480.0 L35486.2-1 8.93.00.3 1 21 9.3-3.00.3 1 2BK_35430.0 L35436.2-1 8.93.00.3 1 21 9.3-3.00.3
49、1 2BK_35380.0 L35386.3-1 9.03.00.3 1 21 9.3-3.00.3 1 3BK_35330.0L35336.2-1 8.82.90.3 0 91 9.3-2.90.3 0 9BK_35280.0 L35286.2-1 8.72.90.3 0 81 9.3-2.90.3 0 9BK_35230.0 L35236.2-1 8.72.90.3 0 81 9.3-2.90.3 0 9L35186.2-1 8.72.90.3 0 81 9.3-2.90.3 0 8BK_35180.0BK_35140.0 L35136.2-1 8.82.90.3 1 01 9.3-3.0
50、0.3 1 07 5.6-1 1.81.2 4 5 Fig.4.Feeder settings of PV plants B.Process of the Simulation 2018 China International Conference on Electricity Distribution Tianjin,17-19 Sep.2018CICED2018 Paper No.201805280000292 Page3/5 1799 Case1：Load sudden drop When t=3s,the load L7 connected to Bus07 drops 200MW s
