Grid Forming Control for Stable Power Systems with. up to 100 % Inverter Based Generation: A Paradigm. Scenario Using the IEEE 118-Bus System

Transcription

1 Grid Forming Control for Stable Power Systems with up to 100 % Inverter Based Generation: Paradigm Scenario Using the IEEE 118-Bus System 17 Oct 2018 Mario Ndreko, Sven Rüberg, Wilhelm Winter

2 Power System Stability with High Level of Power Electronic Interfaced Generation (PEIG) today Power System Stability (voltage, rotor angle, frequency) ssociated with physical response of synchronous generation units future ssociated with the control loops of C/DC power converters used in RES and HDC systems SGs provide: Synchronization effect, system Inertia, high short circuit currents PE-Based RES and HDC systems do not provide inherently a synchronization effect to the system, neither contribution to system inertia 2

3 PEIG Main Characteristics? Power Electronic Interfaced Generators Need a minimum short circuit power level in order to properly synchronise to the grid (during normal and fault conditions ) Highly controllable non-linear modules which interact dynamically with the grid resonance in the sub- and super-synchronous region The prime mover is generally decoupled from the grid through the power electronic interfaces Possible to release stored energy via control loops Exhibit limited overloading capacity and fault current injection highly controllable in the positive and negative sequence 3

4 Instability of Power Electronic Dominated Grids Undamped oscillations between PEIG/HDC and the grid in the subsynchronous as well above-synchronous frequency. Erroneous contribution to grid support functions (voltage, frequency control and synthetic inertia). Loss of synchronism from RES/HDC when the short circuit power is reduced below certain levels. Instability of systems with PEIG Loss of fault ride through capability and trip during grid faults which could also place risks for frequency stability. 4

5 Realising a PE-Dominated Power System Enhancement of system stability Long-term solutions Synthetic Inertia Short-term solutions Grid Connection Codes Mitigation measures Grid Forming Control nscilary services synchrornous condensers dvanced use of HDC RES/ Storage 5

6 Grid Forming Control Concept Generic illustration of a Grid following SC unit: Inverter based plant C Zc Uc I c U s Zline Load Zgrid Grid Equivalent C Sources of instability 1. PLL 2. C current controller I c, ref I c ector current control scheme U s Phase-Locked Loop (PLL) s Grid forming Control for power systems with up to 100% PE based generation units inverter based plant C Zvsc Zc U c I c Zline Load Zgrid Grid Equivalent C P ref c, Q ref c Grid forming control 6

7 Grid Forming Control Schemes vailable grid forming control concepts: irtual Synchronous machine (SM) - Mimics the swing equation of the synchronous generator - Usually does not use a PLL during normal operation - Provides inherent inertia without frequency measurements - Fault response not well studied in the literature Power Synchronization Control (PSC) - Does not use a PLL for normal operation but requires a back-up PLL during faults in order to limit the current - Demonstrate proven response for very weak grids - During grid faults, shifts to current control with PLL - Provides inherent inertia through the power synchronization loop Direct power control (DPC) - It controls the voltage and angle of the converter - very simple in its use and implementation - used widely for stand alone applications and UPS systems 7

8 Enhanced DPC I wt dc f ref P ref P U wt dc u s, abc P f pll 1 R d PLL Cdc U dc pll 1 G 1 Js I m q, out dc R ch y m q y abc c Ps U 3 dq dc m abc Current Limitation During Grid Faults psc U dc 2 oltage limiter x m d, out x m d x pll 1 Ts v u ca, u cb, u cc, r r r L L L mabc U dc u 2 i s, abc Q i sc i sb c,max Q ref P s u sc, i sa u sb, u sa, u s, abc abc dq abc dq i s, dq u s, dq pll u q, s u The SC unit during normal operation regulates the active and the reactive power via controlling its internal voltage angle and amplitude. The output current is the result of voltage drop across the phase reactor. During faults, a current controller is used to limit the current. U s m q ds, 0 q- axis c U c jz I c c m d U s pll t d- axis 8

9 Enhanced DPC Control block which enables fault current limitation ref i sd, u ds, m d i sd, + st - + m d, out - st 1 m d,lim Fault Detect i sq, st - m q,lim - + st 1 + m q, out ref i sq, u qs, m d During grid faults, the converter shifts its operation to current limiting mode. No need to activate and deactivate the PLL No angle jumps 9

10 Simple Test System- Proof of Concept fter the opens the gray zone goes to 100% inverter based generation Inverter based power plant pi-section Line T:380/150k Uk=15% '' S k pi-section Line pi-section Line pi-section Line PCC T:150/ 33kk Uk=10% C DC pi-section Line Resistive Load 380k Grid T:150/ 33kk Uk=10% pi-section Line 10

11 Simple Test System- Proof of Concept SC response for a 150s fault (at t=6s) Spike due to detection delay SC current reactive current active current 11

12 Simple Test System- Proof of Concept SC response for islanding k Grid Current deg Converter angle Hz Frequency of the PLL 12

13 oltage Stability ssessment IEEE 118-Bus SC with current control B55 345k, 138k 7 Large SGs 18 SC-Based units Three fault locations 50% and 70% PE generation B90 Synchronous generator B107 13

14 oltage Stability ssessment IEEE 118-Bus >> 150ms fault at B55 oltage and angle response at the H level The simulations are for the case that the SCs apply conventional control 50% 70% In the 70% case, the voltage drops are bigger and the effect a wider area. 70% 14

15 Effect of high levels of PE bove 70% Simulated events Disconnection of SG1 Disconnection of SG3 time (s) 67% 80% 90% 5s 8s WPP_10 SG3 SG2 WPP_3 SG1 Reduction of the SCR at PCC leads to control interactions observed in the sub-synchronous range 15

16 BRK2 BRK3 BRK4 trip_sg4 Isc_abc Grid forming to mitigate instability Isc trip_sg4 P = Q = = P = Q = = P = Q = = BUS3 BUS4 TL_3_1_1 TL_4_5_1 TL_29_28_1 TL_28_27_1 BUS1 = 102 P = Q = TL_4_11_1 TL_3_5_1 TL_29_31_1 BUS29 BUS28 TL_32_27_1 TL_1_2_ [M] [k] / 33 [k] TL_5_11_ [uf] BUS31 BUS11 TL_5_6_1 BUS5 TL_31_32_1 TL_115_27_1 TL_3_12_1 BUS8 BUS27 BUS2 TL_11_12_1 BUS6 TL_113_32_1 TL_32_114_1 TL_114_115_1 BUS115 TL_6_7_1 BUS114 TL_2_12_1 BUS113 BUS32 BUS7 TL_8_30_1 TL_31_17_1 TL_27_25_1 TL_117_12_1 TL_11_13_1 BUS117 TL_12_16_1 TL_12_7_1 TL_113_17_1 BUS12 BUS16 BUS26 BUS25 TL_16_17_1 TL_32_23_1 TL_30_26_1 BUS13 TL_25_23_1 TL_12_14_1 TL_17_15_1 TL_13_15_1 BUS30 TL_23_24_1 BUS23 BUS14 BUS18 TL_14_15_1 TL_18_17_1 TL_23_22_1 P = Q = = TL_24_72_1 P = Q = = BUS15 BUS17 TL_18_19_1 BUS24 TL_20_21_1 TL_21_22_1 BUS72 P = Q = = BUS19 BUS22 P = Q = = TL_19_15_1 TL_19_20_1 BUS21 BUS20 TL_72_71_1 TL_19_34_1 #2 TL_24_70_1 #1 BUS71 BUS34 33 [k] / [k] [M] P = Q = = trip TL_71_73_1 P = Q = = TL_34_43_1 = 98.8 P = Q = TL_71_70_1 BUS73 TL_15_33_1 TL_34_37_1 TL_34_36_1 TL_30_38_1 BUS43 BUS70 TL_43_44_1 #2 #1 33 [k] / [k] [M] TL_70_75_1 P = Q = TL_75_118_1 TL_118_76_1 BUS76 Isc=6k = BUS44 TL_70_74_1 trip P = Q = = BUS118 BUS36 TL_44_45_1 P = Q = TL_70_69_1 P = Q = = 97.4 = TL_35_37_1 TL_35_36_1 TL_74_75_1 TL_75_77_1 TL_76_77_1 P = 0 Q = 0 = trip BUS35 BUS45 BUS74 TL_45_46_1 TL_75_69_ [MR] BUS75 BUS [M] [k] / 33 [k] TL_47_69_1 TL_46_47_1 TL_77_78_1 P = Q = P = Q = = TL_33_37_1 = BUS46 BUS47 TL_69_77_1 TL_77_80_1 BUS78 TL_86_85_1 trip P = Q = = TL_46_48_1 TL_45_49_1 TL_77_80_2 TL_78_79_1 TL_77_82_1 BUS86 Isc=20 k TL_47_49_1 P = 71.4 Q = BUS33 TL_38_65_1 TL_49_69_1 TL_68_81_1 = BUS38 BUS79 TL_83_85_1 P = 38.5 Q = = trip BUS69 BUS81 TL_79_80_1 TL_85_89_1 TL_83_84_1 TL_89_90_1 TL_89_90_2 TL_48_49_1 TL_90_91_1 TL_91_92_1 BUS91 BUS48 BUS90 TL_37_39_1 TL_65_68_1 TL_83_82_1 TL_85_84_1 BUS68 TL_85_88_1 TL_39_40_1 TL_40_42_1 BUS83 BUS84 TL_88_89_1 P = Q = = BUS88 BUS39 BUS85 TL_37_40_1 TL_41_42_1 TL_42_49_1 TL_42_49_2 TL_65_64_1 TL_89_92_1 TL_89_92_2 BUS89 TL_94_92_1 BUS37 TL_40_41_1 BUS42 BUS65 BUS40 BUS41 BUS66 TL_80_96_1 BUS82 TL_51_49_1 TL_49_66_1 TL_49_66_2 TL_82_96_1 TL_66_62_1 TL_66_67_1 TL_96_94_1 TL_94_93_1 TL_93_92_1 BUS64 TL_95_94_1 BUS93 BUS51 TL_96_95_1 BUS94 TL_64_63_ [M] [k] / [k] TL_67_62_1 TL_49_50_1 BUS67 BUS95 TL_51_52_1 TL_51_58_1 TL_97_96_1 TL_80_97_1 BUS96 BUS50 BUS58 BUS52 BUS49 BUS [M] [k] / [k] TL_94_100_1 TL_62_61_1 BUS92 BUS97 TL_58_56_1 BUS61 TL_62_60_1 TL_92_100_1 TL_92_102_1 TL_50_57_1 TL_56_59_1 TL_56_59_2 TL_61_60_1 TL_61_59_1 BUS62 TL_52_53_1 BUS102 BUS56 TL_59_60_1 TL_56_55_1 TL_49_54_1 BUS59 BUS57 TL_49_54_2 TL_80_98_1 TL_102_101_1 BUS53 TL_56_54_1 BUS98 TL_98_100_1 TL_100_101_1 Isc=12k BRK2 P = Q = 7.01 BUS101 TL_57_56_1 TL_54_59_1 = P = Q = TL_53_54_1 = TL_80_99_1 TL_99_100_1 BRK2 trip_sg3 SWING BUS99 TL_100_103_1 SG 3 BUS54 TL_59_55_1 trip_sg3 TL_100_104_1 P = Q = = TL_104_103_1 TL_54_55_ [MR] [MR] BUS100 BUS104 BUS103 BUS55 BUS80 = 106 P = Q = = P = Q = TL_104_105_1 TL_103_110_1 P = Q = = 128 P = Q = = [MR] BRK_SC10 TL_100_106_1 TL_103_105_1 BUS110 BRK_SC10 TL_110_112_1 P = Q = = [MR] BUS60 = P = 104 Q = TL_110_109_1 BUS112 TL_106_105_1 TL_105_108_1 BUS108 TL_108_109_1 BUS105 BUS109 P = Q = TL_105_107_1 = P = Q = = TL_106_107_1 P = Q = = [MR] BUS106 BUS107 P = Q = = 120 BRK_SG1 Isc=5k Fault BRK_SG1 = 120 BC->G P = Q = = 120 SG 4 SG3 Battery with PSC Battery with PSC Battery with PSC P = Q = = [M] [k] / [k] SC [M] [k] / [k] [M] [k] / [k] SC 204 Battery with PSC SC 7 SC 209 P = Q = = [M] [k] / [k] [M] [k] / [k] [M] [k] / [k] [M] [k] / [k] Battery with PSC SC 203 SC 210 SC 207 Battery with PSC SG2 Battery with PSC part of the unstable PPMs are replaced by PPMs using grid forming control. It is assumed here that the DC voltage is constant and there is storage element available [uf] PPM SG1 SC 10 P = Q = = SC 6 SC 206 SG 1 P = Q = = 106 SC 3 SC 1 SC 5 Battery with PSC SC 8 SC 4 SC 2 16

17 Effect of high levels of PE Use of Grid forming Simulated events Trip SG1 Trip SG2 Trip SG3 Fault Trip PPM The system is stable when part of generated power from PPMs is with grid forming control 67% 2s 3s 4s 100 % d-axis voltage time (s) Grid forming units can change P and Q (assuming DC constant voltage) q-axis voltage The lower voltage profiles are due to lack of reactive power flow in the network. 17

18 Effect of high levels of PE Use of Grid forming Simulated events Trip SG1 Trip SG2 Trip SG3 67% 2s 3s 4s 100 % time (s) PLL frequency of grid forming PPM Internal voltage angle of grid forming PPM 18

19 Effect of high levels of PE Use of Grid forming Simulated events Trip SG1 Trip SG2 Trip SG3 Fault Trip PPM 67% 2s 3s 4s 100 % time (s) Time domain response of selected voltages in the IEEE-118 for a three phase fault in the case of 100% PE. The fast reactive current injection provides a voltage boosting at all monitored nodes. PLL frequency of grid forming PPM Note: In the 100% PE case the frequency variation reflects the changes in the voltage angles in the system 19

20 BRK2 BRK3 BRK4 SC 202 P = Q = = 125 BUS3 BUS4 TL_3_1_1 TL_4_5_1 TL_29_28_1 TL_28_27_1 BUS1 TL_4_11_1 BUS29 BUS28 = Q = P = TL_3_5_1 TL_29_31_1 TL_32_27_1 TL_1_2_1 TL_5_11_1 SC [uf] BUS31 BUS11 TL_5_6_1 BUS5 TL_31_32_1 TL_115_27_1 TL_3_12_1 BUS8 BUS27 BUS2 TL_11_12_1 BUS6 TL_113_32_1 TL_32_114_1 TL_114_115_1 BUS115 TL_6_7_1 BUS114 TL_2_12_1 BUS113 BUS32 BUS7 TL_8_30_1 TL_31_17_1 TL_27_25_1 TL_117_12_1 TL_11_13_1 BUS117 TL_12_16_1 TL_12_7_1 TL_113_17_1 BUS12 BUS16 BUS26 BUS25 TL_16_17_1 TL_32_23_1 Psg2 Psg1 TL_30_26_1 BUS13 TL_25_23_1 TL_12_14_1 TL_17_15_1 TL_13_15_1 BUS30 TL_23_24_1 BUS23 BUS14 BUS18 TL_14_15_1 TL_18_17_1 TL_23_22_1 TL_24_72_1 TL_18_19_1 BUS17 BUS24 BUS15 TL_20_21_1 TL_21_22_1 BUS72 TL_19_15_1 BUS19 BUS22 TL_19_20_1 BUS21 BUS20 TL_72_71_1 TL_19_34_1 SC 204 TL_24_70_1 BUS71 BUS34 TL_71_73_1 TL_34_43_1 = Q = P = TL_71_70_1 BUS73 TL_15_33_1 TL_34_37_1 TL_34_36_1 SG 7 TL_30_38_1 SC 8 BUS43 BUS70 SC 7 TL_43_44_1 TL_70_75_1 TL_75_118_1 SG 2 P = Q = = BUS76 BUS44 TL_70_74_1 TL_118_76_1 BRK3 BRK2 P = Q = = BUS118 BUS36 TL_44_45_1 P = Q = = P = Q = = TL_70_69_1 P = Q = = TL_35_37_1 TL_35_36_1 TL_74_75_1 TL_75_77_1 TL_76_77_1 BRK3 Fault BUS35 BUS45 BUS74 TL_45_46_1 TL_75_69_ [MR] [M] [k] / 33 [k] TL_47_69_1 BUS75 BUS77 BC->G TL_46_47_1 TL_77_78_1 SC 6 P = Q = = P = Q = TL_33_37_1 = BUS46 BUS47 TL_69_77_1 TL_77_80_1 BUS78 TL_86_85_1 SC 9 BRK3 TL_46_48_1 TL_45_49_1 TL_77_80_2 BUS86 TL_47_49_1 TL_78_79_1 TL_77_82_1 P = Q = P = Q = BUS33 TL_38_65_1 TL_49_69_1 = BUS38 BUS69 BUS79 TL_83_85_1 = 140 P = Q = BUS81 TL_79_80_1 TL_85_89_1 TL_83_84_1 TL_89_90_1 TL_89_90_2 SC 4 = TL_48_49_1 SWING TL_90_91_1 TL_91_92_1 BUS48 BUS91 TL_37_39_1 TL_65_68_1 BUS90 TL_39_40_1 TL_40_42_1 BUS68 TL_68_81_1 TL_83_82_1 TL_85_84_1 TL_85_88_1 BRK2 BUS83 BUS84 TL_88_89_1 BRK3 BUS39 BUS88 TL_37_40_1 BUS85 TL_41_42_1 TL_42_49_1 TL_42_49_2 TL_65_64_1 TL_89_92_1 TL_89_92_2 BRK3 BUS89 BUS37 TL_40_41_1 BUS42 BUS65 BUS40 BUS41 BUS66 TL_80_96_1 BUS82 TL_51_49_1 TL_49_66_1 TL_49_66_2 TL_94_92_1 TL_66_62_1 TL_82_96_1 TL_66_67_1 TL_96_94_1 TL_94_93_1 TL_93_92_1 BUS64 BUS51 TL_95_94_1 P = Q = TL_64_63_ [M] [k] / [k] TL_67_62_1 TL_96_95_1 = BUS94 BUS67 TL_49_50_1 TL_51_52_1 TL_51_58_1 TL_97_96_1 BRK3 BRK2 BUS95 SC 1 BRK3 BUS96 BUS58 BUS52 BUS49 BUS [M] [k] / [k] TL_80_97_1 BUS93 BUS50 TL_62_61_1 TL_94_100_1 P = Q = BUS92 BUS61 BUS97 TL_58_56_1 TL_62_60_1 = TL_50_57_1 TL_56_59_1 TL_56_59_2 TL_61_60_1 TL_92_100_1 TL_92_102_1 TL_61_59_1 BUS62 SG 3 TL_52_53_1 BUS56 TL_59_60_1 BUS102 TL_56_55_1 TL_49_54_1 BUS60 BUS59 BUS57 TL_49_54_2 TL_80_98_1 TL_102_101_1 BUS53 TL_56_54_1 TL_57_56_1 TL_54_59_1 BUS98 TL_98_100_1 TL_100_101_1 BUS101 TL_53_54_1 P = Q = = TL_80_99_1 TL_99_100_1 BUS99 TL_100_103_1 BUS54 TL_59_55_1 TL_100_104_1 TL_104_103_ [MR] = Q = P = P = Q = = TL_54_55_1 SC [MR] BUS100 BUS104 BRK3 BUS55 BUS103 BUS80 TL_104_105_1 TL_103_110_1 P = Q = SC 2 = Q = P = = Q = P = SC 203 = [MR] Fault SG 5 TL_100_106_1 TL_103_105_1 BUS110 SC 206 BC->G SC 207 TL_110_112_1 = Q = P = TL_110_109_1 BUS112 TL_106_105_1 TL_105_108_1 BUS108 TL_108_109_1 SC 210 BUS105 BUS109 SC 5 P = Q = BUS106 TL_105_107_1 = BRK3 P = Q = = TL_106_107_1 SG 1 BUS107 P = Q = = SC 3 70% Penetration and SCs with grid forming on the IEEE 118 Compatibility with SGs [M] [k] / [k] SC 209 P = 0 Q = 0 = P = Q = = [M] [k] / [k] [M] [k] / [k] SG [M] [k] / [k] [M] [k] / [k] [M] [k] / [k] P = Q = 231 = [M] [k] / [k] [uf] P = Q = = P = Q = -18 = P = Q = = P = Q = =

21 Summary The presented results with the IEEE 118-Bus shows that bulk transmission systems are stable when part of the PEIG applies grid forming control. Balancing active power in the case of the 100% PE-based network is performed using the PLL frequency. The PLL frequency reflects the changes in the voltage angles as a result of changes in the power flow. The stability of the 100% PE-Based system lies in the ability to maintain the voltage angle stability. The provision of rated reactive current injection from SCs with grid forming control requires additional control and fast fault state detection to avoid over-current spikes. 21

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