INTEGRATION OF PV PLANT INTO ELECTRICITY GRID CASE

INTEGRATION OF PV PLANT INTO ELECTRICITY GRID: CASE OF LITHUANIAN ENERGY INSTITUTE Dr. Virginijus Radziukynas Lithuanian Energy. Institute (presented by Arturas Klementavicius) CYSENI 2019, May 23 -24, Kaunas, Lithuanian Energy Institute

Introduction i. Distributed. PV Why are we tackling integration? PV integration may destabilize distribution grid • particularly on large-scale connection of PVs What is grid destabilization? • Voltage instabilities (overloadings, underloadings, voltage fluctuations, voltage dips) • Thermal overloading of grid conductors • if not counteracted, stabilities cause the cut-off of the network How is are identified grid stability limits? • By means of high-accuracy calculation of power flows in the considered network Solar PV on the distribution grid: smart integrated solutions of distributed generation based on solar PV, energy storage devices and active demand management 2

i. Distributed. PV Nature of voltage regulation Theoretical ls fundamenta Pgen feeds Active Power injected to grid U = f (P, Q) – controllable parameters Pload Active Power withdrawn from grid Qgen Reactive Power injected to grid Qload Reactive Power withdrawn from grid overvoltage U feeds U undervoltage U U undervoltage Pgen is interrelated with Qgen Solar PV on the distribution grid: smart integrated solutions of distributed generation based on solar PV, energy storage devices and active demand management 3

i. Distributed. PV Centralised voltage control in grids with distributed generation d. U ralize em t n e C t ol sys contr Inverter Smart meter Automatic on-load tap changer PV unit Solar PV on the distribution grid: smart integrated solutions of distributed generation based on solar PV, energy storage devices and active demand management 4

i. Distributed. PV Objective of the study Investigation is centred on distribution grid with integrated solar (PVs) generation. It is aimed at evaluation of grid stability subjected to intermittent RESelectricity generation for the selected test case. The investigation deals with grid stability in terms of voltage levels in steady-state conditions, namely: - minimum voltages; - maximum grid thermal capacities Solar PV on the distribution grid: smart integrated solutions of distributed generation based on solar PV, energy storage devices and active demand management 5

i. Distributed. PV PV integration study: Showcase of public building (Lithuanian Energy Institute) Solar PV on the distribution grid: smart integrated solutions of distributed generation based on solar PV, energy storage devices and active demand management 6

i. Distributed. PV LEI connection-to-grid: detailed scheme ib. r t s di k. V ations 0 11 bst su LEI grid 10 2 nd alternative PV connection (100 k. W) k. V 1 st alternative PV connection (100 k. W) G G Solar PV on the distribution grid: smart integrated solutions of distributed generation based on solar PV, energy storage devices and active demand management 7

LEI connection-to-grid: simulated scheme i alia on m A tati s sub i. Distributed. PV 1 st alternative PV connection (100 k. W) va a r Mu tation s sub 2 nd alternative PV connection (100 k. W) Figure. Grid with medium voltage (10 k. V) connected public consumer (LEI) with 100 k. W of PV unit on LV side Solar PV on the distribution grid: smart integrated solutions of distributed generation based on solar PV, energy storage devices and active demand management 8

i. Distributed. PV Network flow calculation results E PSS/ ) g n i Us 33. 0. v ( tool. Solar PV on the distribution grid: smart integrated solutions of distributed generation based on solar PV, energy storage devices and active demand management 9

i. Distributed. PV PSS/E interface window LEI-connection buses Solar PV on the distribution grid: smart integrated solutions of distributed generation based on solar PV, energy storage devices and active demand management 10

i. Distributed. PV PV generation impact of bus voltages (1) Mode Winter (Pmax) Voltage variation in the circuit TR 1 - bus 5113 – bus 10921 under different loading and generation modes Power generated (Pg), MW Bus number 5113 10902 10920 10921 0. 1 (normal case) Summer (Pmin) Winter (Pmax, no generation) Summer (Pmin, no generation ) 5113 10902 10920 10921 0. 1 (normal case) Voltage. k. V 117. 84 (1. 0713 PU) 10. 296 (1. 0296 PU) 10. 293 (1. 0293 PU) 0. 4080 (1. 0200 PU) 120. 12 (1. 0920 PU) 10. 563 (1. 0562 PU) 10. 561 (1. 0561 PU) 0. 4221 (1. 0552 PU) Active power, MW Apparent power, MVA 8. 1 0 0 8. 9 8. 7 0 0 3. 8 4. 3 3. 3 0. 1 3. 5 0. 1 Permissible generation, MW 1. 59 overvoltages, U>1. 10 PU Maximum generation 0. 865 overvoltages, U>1. 10 PU 5113 10902 10920 10921 0 117. 84 (1. 0712 PU) 10. 296 (1. 0296 PU) 10. 285 (1. 0285 PU) 0. 4053 (1. 0133 PU) 8. 2 0. 1 9 8. 9 0. 1 5113 10902 10920 10921 0 120. 12 (1. 0920 PU) 10. 563 (1. 0562 PU) 10. 561 (1. 0561 PU) 0. 4214 (1. 0534 PU) 3. 9 3. 3 0 0 4. 4 3. 4 0 0 Solar PV on the distribution grid: smart integrated solutions of distributed generation based on solar PV, energy storage devices and active demand management No generation 11

PV generation impact of bus voltages (2) Mode Bus number 5158 10901 10910 10911 Summer (Pmin) Winter (Pmax, no generation) Summer (Pmin, no generation) 0. 1 (normal case) Winter (Pmax) Voltage variation in the circuit TR 2 - bus 5158 – bus 10911 under different loading and generation modes Power generated (Pg), MW 5158 10901 10910 10911 0. 1 (normal case) 5158 10901 10910 10911 0 0 Voltage. k. V Active power, MW Apparent power, MVA 117. 94 (1. 0722 PU) 10. 218 (1. 0218 PU) 10. 216 (1. 0216 PU) 0. 4015 (1. 0037 PU) 5. 9 5. 6 0. 3 0. 4 6 0. 33 0. 43 120. 16 (1. 0923 PU) 10. 535 (1. 0533 PU) 10. 532 (1. 0532 PU) 0. 4207 (1. 0519 PU) 2. 2 0. 1 2. 4 0. 1 117. 94 (1. 0722 PU) 10. 214 (1. 0214 PU) 10. 212 (1. 0212 PU) 0. 3983 (0. 9959 PU) 6 5. 6 0. 4 6. 5 6 0. 4 120. 16 (1. 0923 PU) 10. 535 (1. 0535 PU) 10. 534 (1. 0534 PU) 0. 4206 (1. 0516 PU) 2. 3 0 0 2. 5 2. 4 0 0 i. Distributed. PV Permissible generation, MW 2. 5 overvoltages, U>1. 10 PU Maximum generation 1. 98 overvoltages, U>1. 10 PU Solar PV on the distribution grid: smart integrated solutions of distributed generation based on solar PV, energy storage devices and active demand management No generation 12

Discussion of results 1) Under grid maximum loading, grid voltage is close to nominal value along the chain from 110 k. V bus (5158) to 0. 4 bus (10911). The addition of 100 k. W generation output raises the voltage at the most sensitive bus only by 0. 007 PU (from 0. 9959 to 1. 0037 PU). i. Distributed. PV Insignificant impact 2) Under grid minimum loading, grid voltage persists to be on 1. 05 PU level. The addition of PV generation of 100 k. W to bus 10911 insignificantly raises the voltage from 1. 0516 to 1. 0519 PU (by 0. 3%). 3) The grid stability is limiting theoretical LEI’s generation up to 2500 k. W, i. e. 25 times larger than normal generation value (100 k. W) in winter loading mode. As for summer loading, the stability limit is 1980 k. W, i. e. 20 times larger. The stability limiting factors are overvoltages caused by huge injections of PVs. Large grid transfer capacities available Solar PV on the distribution grid: smart integrated solutions of distributed generation based on solar PV, energy storage devices and active demand management 13

Thank you for your attention ! Presenter: Dr. Arturas Klementavicius System control and automation laboratory Lithuanian Energy Institute Phone number: +370 616 48814 Questions? http: //www. lei. lt 14