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Mobile QR Code QR CODE : Journal of the Korean Institute of Illuminating and Electrical Installation Engineers

Journal of the Korean Institute of Illuminating and Electrical Installation Engineers

ISO Journal TitleJ Korean Inst. IIIum. Electr. Install. Eng.

  1. (M.S and Ph.D. course, Department of Energy System Engineering, Chung-Ang University, Korea)
  2. (Undugraduate student, Department of Energy System Engineering, Chung-Ang University, Korea)
  3. (General Manager, ESS Department Head, Eon Co., Ltd, Korea)



Grid-connected inverter, HVRT, LVRT, TNPC

1. ์„œ ๋ก 

ํ™˜๊ฒฝ ์ด์Šˆ ๋ฟ๋งŒ ์•„๋‹ˆ๋ผ ๋Œ€์ฒด ์—๋„ˆ์ง€๋กœ๋„ ์ฃผ๋ชฉ๋ฐ›๊ณ  ์žˆ๋Š” ์‹ ์žฌ์ƒ ๋ฐœ์ „์›์„ ์ด์šฉํ•˜๋Š” ๋ถ„์‚ฐํ˜• ์ „์›์˜ ๋น„์ค‘์ด ์ฆ๊ฐ€ํ•˜๋Š” ์ถ”์„ธ์™€ ํ•จ๊ป˜, ๊ณ„ํ†ต ์•ˆ์ •์„ฑ์— ๋ฏธ์น˜๋Š” ๋ถ„์‚ฐํ˜• ์„ค๋น„์˜ ์˜ํ–ฅ ๋˜ํ•œ ์ฆ๊ฐ€ํ•˜๊ณ  ์žˆ์œผ๋ฉฐ, ์ด๋ฅผ ๊ณ ๋ คํ•˜์—ฌ ๋ถ„์‚ฐํ˜• ์ „์›์˜ ๊ณ„ํ†ต์—ฐ๊ณ„ ๊ธฐ์ค€์— ๋Œ€ํ•œ ์—„๊ฒฉํ•œ ๊ทœ์ •์ด ํ•ด์™ธ ๋ฟ๋งŒ์•„๋‹ˆ๋ผ ๊ตญ๋‚ด์—์„œ๋„ ์ œ์‹œ๋˜๊ณ  ์žˆ๋‹ค (1-6). ๊ณ„ํ†ต ์ „์••์ด ๊ธฐ์ค€ ์ „์••์˜ 0.9p.u. ๋ฏธ๋งŒ์ธ ์ƒํ™ฉ์—์„œ ๋™์ž‘ํ•˜๋Š” Low Voltage Ride Through(LVRT) ๊ธฐ์ค€๊ณผ 1.1p.u. ์ด์ƒ์—์„œ ๋™์ž‘ํ•˜๋Š” High Voltage Ride Through(HVRT) ์กฐ๊ฑด์€ ๋ถ„์‚ฐํ˜• ์ „์›์˜ ๊ณ„ํ†ต ์—ฐ๊ณ„์‹œ ์š”๊ตฌ๋˜๋Š” ๋Œ€ํ‘œ์ ์ธ ๊ธฐ์ค€์œผ๋กœ์จ ํ•œ๊ตญ์ „๋ ฅ๊ณต์‚ฌ์—์„œ๋Š” ์†ก์ „๊ณ„ํ†ต(5)๊ณผ ๋ฐฐ์ „๊ณ„ํ†ต ์—ฐ๊ณ„ ๊ธฐ์ˆ (6) ์—์„œ ๊ฐ๊ฐ ๋‹ค๋ฅธ LVRT ๋ฐ HVRT ๊ธฐ์ค€์„ ๊ฐ–๊ณ  ์žˆ๋‹ค. ๋ณธ ๋…ผ๋ฌธ์—์„œ๋Š” ํ•œ๊ตญ์ „๋ ฅ๊ณต์‚ฌ์˜ ์†ก์ „๊ณ„ํ†ต๊ณผ ๋ฐฐ์ „๊ณ„ํ†ต์— ๋Œ€ํ•œ ์ตœ์‹  ๊ทœ์ •์—์„œ ์ œ์‹œํ•˜๋Š” LVRT, HVRT ๊ธฐ์ค€์— ๋Œ€ํ•œ ๋ถ„์„์ด ์ˆ˜ํ–‰๋˜์—ˆ๋‹ค. ๋ฐฐ์ „ ๊ณ„ํ†ต ์—ฐ๊ณ„ ๊ธฐ์ค€์˜ LVRT ์กฐ๊ฑด์€ ์†ก์ „๊ณ„ํ†ต ์—ฐ๊ณ„ ๊ธฐ์ค€์˜ ์กฐ๊ฑด๊ณผ ๋น„๊ตํ•˜์—ฌ ์ƒ๋Œ€์ ์œผ๋กœ ๊ธด ๊ณ„ํ†ต์—ฐ๊ณ„ ์œ ์ง€์‹œ๊ฐ„์„ ํŠน์ง•์œผ๋กœ ํ•˜๊ณ  ์žˆ์œผ๋ฉฐ, ์ฆ๊ฐ€ํ•˜๋Š” ๊ตญ๋‚ด์˜ ๋ถ„์‚ฐํ˜• ์ „์›์˜ ๋น„์ค‘์— ๋”ฐ๋ผ, ๊ณ„ํ†ต์˜ ๊ณ ์žฅ์ƒํ™ฉ ๋ฐœ์ƒ ์‹œ ๋ถ„์‚ฐํ˜• ์ „์›์˜ ์—ฐ๊ณ„ ์‹œ๊ฐ„๋„ ์ ์ฐจ ์ฆ๊ฐ€ํ•˜๋Š” ์ถ”์„ธ๋กœ ๋ณ€ํ™” ๋  ๊ฒƒ์„ ๊ณ ๋ คํ•˜์—ฌ ํ˜„์žฌ ํ•œ์ „์˜ ๋ฐฐ์ „๊ณ„ํ†ต LVRT ๊ธฐ์ค€ ์—ญ์‹œ ์ ์ฐจ ์†ก์ „ ๊ณ„ํ†ต ๊ธฐ์ค€์— ์ค€ํ•˜๋Š” ์—ฐ๊ณ„์‹œ๊ฐ„์„ ๊ฐ€์งˆ ๊ฒƒ์œผ๋กœ ๋ถ„์„ํ•˜์˜€์œผ๋ฉฐ, ์ด์— ๋”ฐ๋ผ ๋ฐฐ์ „ ๊ณ„ํ†ต ์—ฐ๊ณ„ ๊ธฐ์ค€์˜ HVRT ์กฐ๊ฑด์„ ์ฐธ๊ณ ํ•˜์—ฌ, ์†ก์ „๊ณ„ํ†ต์— ์กด์žฌํ•˜์ง€ ์•Š๋Š” HVRT ์•Œ๊ณ ๋ฆฌ์ฆ˜์„ ๊ตฌํ˜„ํ•˜์—ฌ ๋ฐฐ์ „๊ณ„ํ†ต ์ „์•• ๋ ˆ๋ฒจ์—์„œ ๋™์ž‘ํ•˜๋Š” 3-level TNPC ์ธ๋ฒ„ํ„ฐ์— ๋ณธ ์•Œ๊ณ ๋ฆฌ์ฆ˜์„ ์ ์šฉํ•œ ๋‚ด์šฉ์„ ๋‹ค๋ฃจ์—ˆ๋‹ค. ๋˜ํ•œ ์—ฐ๊ณ„ ์œ ์ง€ ๋ฐ ์ค‘๋‹จ ์ƒํ™ฉ ๋ฟ ๋งŒ ์•„๋‹ˆ๋ผ ๋น„์ •์ƒ ์ „์•• ์ƒํ™ฉ ์‹œ ๊ณ„ํ†ต ์ง€์›์„ ๋ชฉ์ ์œผ๋กœ ๊ฐ ๊ณ„ํ†ต ์ „์••์— ๋”ฐ๋ผ ์œ ํšจ, ๋ฌดํšจ์ „๋ฅ˜์ œ์–ด ์ „๋žต์„ ์ ์šฉํ•จ์œผ๋กœ์จ ๊ณ„ํ†ต์ง€์› ์ƒํ™ฉ์„ ๋‹ค์–‘ํ•œ ์‹œ๋ฎฌ๋ ˆ์ด์…˜ ์ผ€์ด์Šค๋ฅผ ํ†ตํ•ด ๋ชจ๋ธ๋ง ๋ฐ ๋ถ„์„ํ•œ๋‹ค.

2. ๋ณธ ๋ก 

2.1 LVRT & HVRT ๊ธฐ์ค€

Fig. 1. Voltage boundary line of KEPCOโ€™s distribution system connection technology standard (LVRT, HVRT)
../../Resources/kiiee/JIEIE.2022.36.2.028/fig1.png

Fig. 2. Voltage boundary line of KEPCOโ€™s transmission grid connection technology standard (LVRT)
../../Resources/kiiee/JIEIE.2022.36.2.028/fig2.png

Fig 1์€ ํ•œ๊ตญ์ „๋ ฅ๊ณต์‚ฌ์˜ ๋ถ„์‚ฐํ˜• ์ „์›์˜ ๋ฐฐ์ „ ๊ณ„ํ†ต ์—ฐ๊ณ„ ๊ธฐ์ˆ (6) ์—์„œ ์ œ์‹œํ•˜๋Š” ๋น„์ •์ƒ ์ „์••์— ๋Œ€ํ•œ ์šด์ „ ์ง€์†์‹œ๊ฐ„๊ณผ ๋ถ„์‚ฐํ˜• ์ „์› ๋ถ„๋ฆฌ์‹œ๊ฐ„์„ ๊ฐ๊ฐ ๋‚˜ํƒ€๋‚ธ๋‹ค. ๊ฐ ์กฐ๊ฑด์— ๋Œ€ํ•œ ์„ค๋ช…์€ ๋‹ค์Œ๊ณผ ๊ฐ™๋‹ค. ๊ณ„ํ†ต์ „์•• 50% ๋ฏธ๋งŒ : 150ms ๋™์•ˆ ์šด์ „์„ ์ง€์†ํ•ด์•ผ ํ•˜๋ฉฐ, 499ms ๊นŒ์ง€ ์šด์ „์€ ์ค‘์ง€ํ•˜์ง€๋งŒ ๊ณ„ํ†ต๊ณผ ์—ฐ๊ณ„๋Š” ์œ ์ง€ํ•œ๋‹ค. ๊ทธ๋ฆฌ๊ณ  500ms๊ฐ€ ์ง€๋‚˜๋ฉด ๊ณ„ํ†ต๊ณผ ์—ฐ๊ณ„๋ฅผ ๋ถ„๋ฆฌํ•œ๋‹ค. ๋‹ค์Œ์œผ๋กœ ๊ณ„ํ†ต์ „์••์˜ 50% ์ด์ƒ 70% ๋ฏธ๋งŒ ๊ตฌ๊ฐ„์˜ ๊ฒฝ์šฐ 160ms๊นŒ์ง€ ๋ถ„์‚ฐํ˜• ์ „์›์€ ์šด์ „์„ ์ง€์†ํ•˜๋ฉฐ, 2์ดˆ ์ดํ›„ ๊ณ„ํ†ต๊ณผ ๋ถ„๋ฆฌํ•˜๊ณ  ๊ทธ ์ „ ๊นŒ์ง€๋Š” ์šด์ „ ์ค‘์ง€ ์ƒํƒœ์ด๋‹ค. ๊ณ„ํ†ต์ „์••์˜ 70%๏ฝž90% ๊ตฌ๊ฐ„์—์„œ๋Š” 1.5์ดˆ ๊นŒ์ง€ ๊ณ„ํ†ต์—ฐ๊ฒฐ ๋ฐ ์šด์ „ ์ง€์†์„ ํ•˜๋ฉฐ ์ดํ›„ ์šด์ „์„ ์ค‘์ง€ ํ•˜๋‹ค๊ฐ€ 2์ดˆ ์ดํ›„ ๊ณ„ํ†ต๊ณผ ๋ถ„๋ฆฌํ•œ๋‹ค. ๊ณ„ํ†ต ์ „์••์˜ 90%๏ฝž110%๋Š” ์ •์ƒ๋™์ž‘์ด๋‹ค. ๋‹ค์Œ์œผ๋กœ ๊ณ„ํ†ต์ „์••์˜ 110%๏ฝž120% ๊ตฌ๊ฐ„๋ถ€ํ„ฐ๋Š” HVRT ๊ตฌ๊ฐ„์œผ๋กœ์จ 200ms๊นŒ์ง€ ๊ณ„ํ†ต ์—ฐ๊ฒฐ ๋ฐ ์šด์ „์„ ์ง€์†ํ•˜๊ณ  ์ดํ›„ 1์ดˆ ๊นŒ์ง€๋Š” ์šด์ „์„ ์ค‘์ง€ํ•˜๋ฉฐ 1์ดˆ ์ดํ›„ ๋ถ„์‚ฐํ˜• ์ „์›์€ ๊ณ„ํ†ต๊ณผ ๋ถ„๋ฆฌํ•œ๋‹ค. ๊ณ„ํ†ต์ „์••์˜ 120% ์ด์ƒ ๊ตฌ๊ฐ„์—์„œ๋Š” ์šด์ „ํ•˜์ง€ ์•Š์œผ๋ฉฐ, 160ms ์ดํ›„ ๋ถ„์‚ฐํ˜• ์ „์›์€ ๊ณ„ํ†ต๊ณผ ๋ถ„๋ฆฌ๋œ๋‹ค. ๋‹ค์Œ์œผ๋กœ Fig 2๋Š” ํ•œ๊ตญ์ „๋ ฅ๊ณต์‚ฌ์˜ ์†ก,๋ฐฐ์ „์šฉ ์ „๊ธฐ์„ค๋น„ ์ด์šฉ๊ทœ์ •(5) ์—์„œ ์ œ์‹œํ•˜๋Š” ์†ก์ „์šฉ ์ „๊ธฐ์„ค๋น„ ์ ‘์†๊ธฐ์ค€์˜ ๊ณ„ํ†ต์—ฐ๊ณ„ ์œ ์ง€ ๊ธฐ์ค€์„ ๋‚˜ํƒ€๋‚ด๋Š” ๊ทธ๋ž˜ํ”„์ด๋ฉฐ 22.9kV ์†ก์ „๊ณ„ํ†ต์ด ์ฃผ์š” ์ ์šฉ ๋Œ€์ƒ์ด๋‹ค. Fig 1์˜ ๋ฐฐ์ „ ๊ณ„ํ†ต ๊ธฐ์ค€๊ณผ ๋น„๊ตํ•˜์—ฌ ๊ณ„ํ†ต์ „์••์ด ์ €์ „์•• ์ƒํƒœ๊ฐ€ ๋˜๋Š” ์˜์—ญ์—์„œ ์ƒ๋Œ€์ ์œผ๋กœ ๊ธด ์‹œ๊ฐ„ ๋™์•ˆ ๊ณ„ํ†ต ์—ฐ๊ฒฐ ๋ฐ ์šด์ „์„ ์ง€์†ํ•œ๋‹ค. ๊ทธ๋Ÿฌ๋‚˜ ํ•œ์ „์˜ ์†ก์ „๊ณ„ํ†ต ๊ธฐ์ค€์—์„œ๋Š” HVRT ์˜์—ญ์„ ์ œ์‹œํ•˜๊ณ  ์žˆ์ง€ ์•Š๋‹ค. ๋ณธ ๊ณ„ํ†ต ์ ‘์†๊ธฐ์ค€์€ ๋…์ผ์˜ LVRT ๊ธฐ์ค€ (2)๊ณผ ๋น„๊ตํ•˜์—ฌ ์œ ์‚ฌ์„ฑ์„ ์ง€๋‹Œ๋‹ค. 150ms ์ดํ•˜ ๊ตฌ๊ฐ„์—์„œ ๊ณ„ํ†ต์ „์••์ด 0p.u.๊ฐ€ ๋˜๋”๋ผ๋„ ๊ณ„ํ†ต๊ณผ ์ฆ‰์‹œ ๋ถ„๋ฆฌํ•˜์ง€ ์•Š๊ณ  ์šด์ „์„ ์ง€์† ํ•˜๋Š” ๊ฒƒ, ๊ทธ๋ฆฌ๊ณ  0.67p.u/sec ๊ธฐ์šธ๊ธฐ์˜ ๊ฒฝ๊ณ„์„ ์„ ๊ฐ–๋Š” ๊ฒƒ ๋“ฑ์˜ ์œ ์‚ฌ์ ์ด ์žˆ์œผ๋ฉฐ, ์ด ๋…์ผ์˜ ๊ทœ์ •์€ ๊ตญ๋‚ด ๋ฟ๋งŒ ์•„๋‹ˆ๋ผ ๋ฏธ๊ตญ, ์ผ๋ณธ, ์ค‘๊ตญ ๋“ฑ ๋‹ค์ˆ˜์˜ ๊ตญ๊ฐ€์—์„œ ๊ธฐ๋ฐ˜์œผ๋กœ ๋‘๊ณ  ์žˆ๋‹ค. ์†ก์ „๊ณ„ํ†ต ์—ฐ๊ณ„๊ธฐ์ˆ  ๊ธฐ์ค€์˜ LVRT ๊ฒฝ๊ณ„์กฐ๊ฑด์— ๋Œ€ํ•œ ์„ค๋ช…์€ ๋‹ค์Œ๊ณผ ๊ฐ™๋‹ค. ๊ณ„ํ†ต ์ „์••์ด 0 p.u.๊นŒ์ง€ ๊ฐ์†Œํ•˜๋Š” ์ƒํ™ฉ์—์„œ๋„ 150ms๊นŒ์ง€ ๋ถ„์‚ฐํ˜• ์ „์›์€ ๊ณ„ํ†ต ์—ฐ๊ณ„๋ฅผ ์œ ์ง€ํ•œ๋‹ค. 150ms๋ถ€ํ„ฐ 1.5s๊นŒ์ง€๋Š” ์ดˆ๋‹น 0.67p.u.์˜ ๊ธฐ์šธ๊ธฐ๋กœ ๊ฒฝ๊ณ„์„ ์ด ๊ตฌ๋ถ„๋˜๋Š”๋ฐ, ์ด ๊ฒฝ๊ณ„์„ ์˜ ์ขŒ์ธก์€ ๊ณ„ํ†ต ์—ฐ๊ฒฐ ๋ฐ ์šด์ „์ง€์† ์˜์—ญ์ด๊ณ  ์šฐ์ธก์€ ๊ณ„ํ†ต ๋ถ„๋ฆฌ ์˜์—ญ์ด๋‹ค. ๊ณ„ํ†ต์ „์•• 0.9p.u.๋Š” ์—ฐ๊ณ„์ ์˜ ์šด์˜์ „์•• ๋ฒ”์œ„์˜ ์ตœ์†Œ๊ฐ’์ด๋‹ค. ์ด ์†ก์ „๊ณ„ํ†ต ๊ธฐ์ค€์€ ๋ณ„๋„์˜ HVRT ๊ธฐ์ค€์ด ์š”๊ตฌ๋˜์ง€ ์•Š๋Š”๋‹ค. ๋ณธ ๋…ผ๋ฌธ์—์„œ๋Š” ํ•œ๊ตญ์ „๋ ฅ๊ณต์‚ฌ์˜ ์†ก์ „๊ณ„ํ†ต ๊ธฐ์ˆ ๊ธฐ์ค€์˜ LVRT ์กฐ๊ฑด๊ณผ ๋ฐฐ์ „๊ณ„ํ†ต์˜ HVRT ๊ธฐ์ค€์„ ๊ฒฐํ•ฉํ•œ ์•Œ๊ณ ๋ฆฌ์ฆ˜์„ 3-Level TNPC ์ธ๋ฒ„ํ„ฐ์— ์ ์šฉํ•˜์—ฌ PLEXIM-Plecs ์†Œํ”„ํŠธ์›จ์–ด๋ฅผ ํ†ตํ•ด ์‹œ๋ฎฌ๋ ˆ์ด์…˜์„ ์ˆ˜ํ–‰ํ•˜์˜€๋‹ค. ๋‘ ๊ธฐ์ค€์„ ๊ฒฐํ•ฉํ•œ ๊ทธ๋ž˜ํ”„๋Š” Fig 3์— ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค.

Fig. 3. Voltage boundary line of KEPCOโ€™s transmission grid connection technology standard (LVRT, HVRT)
../../Resources/kiiee/JIEIE.2022.36.2.028/fig3.png

2.2 LVRT & HVRT ์กฐ๊ฑด์—์„œ ์œ , ๋ฌดํšจ์ „๋ฅ˜ ์ฃผ์ž…๊ธฐ์ค€

LVRT & HVRT ์ƒํ™ฉ ์‹œ ๋ถ„์‚ฐํ˜• ์ „์›์€ ๊ณ„ํ†ต ์—ฐ๊ณ„๋ฅผ ์œ ์ง€ํ•  ๋ฟ๋งŒ ์•„๋‹ˆ๋ผ ์œ , ๋ฌดํšจ์ „๋ฅ˜๋ฅผ ์ฃผ์ž…ํ•˜์—ฌ ๊ณ„ํ†ต์„ ์ง€์›ํ•˜๋Š” ๊ธฐ์ค€ ๋˜ํ•œ ์ œ์‹œ๋˜๊ณ  ์žˆ๋‹ค. ๋ณธ ๋…ผ๋ฌธ์˜ ์ธ๋ฒ„ํ„ฐ ํšŒ๋กœ์—์„œ ์ ์šฉํ•œ ๋ฌดํšจ์ „๋ฅ˜ ์ฃผ์ž…๊ธฐ์ค€์„ ๊ทธ๋ž˜ํ”„๋กœ ๋‚˜ํƒ€๋‚ธ ๊ฒƒ์ด Fig 4์ด๋‹ค. ํ•ด๋‹น ๋ฌดํšจ์ „๋ฅ˜ ์ฃผ์ž…๊ธฐ์ค€์— ๋Œ€ํ•œ ์„ค๋ช…์€ ๋‹ค์Œ๊ณผ ๊ฐ™๋‹ค. ๊ณ„ํ†ต์ „์••์ด ๊ธฐ์ค€์ „์••์˜ 0p.u. ๋ถ€ํ„ฐ 0.5p.u.๋ฏธ๋งŒ ๊ตฌ๊ฐ„์—์„œ ๋ฌดํšจ์ „๋ฅ˜ ํฌ๊ธฐ๋Š” ์ •๊ฒฉ์ „๋ฅ˜์™€ ๋™์ผํ•˜๊ณ  ์œ ํšจ์ „๋ฅ˜๋Š” 0A๊ฐ€ ํ๋ฅธ๋‹ค. ๊ณ„ํ†ต์ „์••์ด ์ •๊ฒฉ์ „์••์˜ 0.5p.u.์ด์ƒ, 0.9p.u.๋ฏธ๋งŒ์ธ ๊ฒฝ์šฐ ๋ฌดํšจ์ „๋ฅ˜๋Š” k(0.9-Vg)In ์œผ๋กœ ๊ณ„ํ†ต์— ์ฃผ์ž…๋˜๋ฉฐ, ์—ฌ๊ธฐ์„œ K ๋Š” 2.5์˜ ๊ฐ’์„ ๊ฐ–๋Š”๋‹ค. ๊ณ„ํ†ต์ „์••์ด ๊ธฐ์ค€์ „์••์˜ 0.9p.u. ๋ถ€ํ„ฐ 1p.u. ๊นŒ์ง€๋Š” dead zone ์˜์—ญ์œผ๋กœ์จ ์œ ํšจ์ „๋ฅ˜๋Š” ์ •๊ฒฉ์ „๋ฅ˜์™€ ๋™์ผํ•œ ๊ฐ’์„ ๊ฐ€์ง€๋ฉฐ, ๋ฌดํšจ์ „๋ฅ˜๋Š” 0A๊ฐ€ ํ๋ฅธ๋‹ค. ๊ณ„ํ†ต์ „์••์ด ์ •๊ฒฉ์˜ 1.1p.u. ๋ถ€ํ„ฐ 1.2p.u. ๊นŒ์ง€๋Š” HVRT ๊ตฌ๊ฐ„์œผ๋กœ ํ•ด๋‹น ๊ตฌ๊ฐ„์˜ ๋ฌดํšจ์ „๋ฅ˜๋Š” -k(Vg-1.1)In A ์ด๋‹ค. ์œ , ๋ฌดํšจ์ „๋ฅ˜ ์ฃผ์ž…๊ธฐ์ค€์— ๋”ฐ๋ฅธ ์ˆ˜์‹์€ ์‹ (1)-(4)์— ๋‚˜ํƒ€๋‚˜ ์žˆ์œผ๋ฉฐ, ์ˆ˜์‹์— ์‚ฌ์šฉ๋œ ๊ธฐํ˜ธ์— ๋Œ€ํ•œ ์„ค๋ช…์€ ๋‹ค์Œ๊ณผ ๊ฐ™๋‹ค.

Fig. 4. Reactive current control curve in the event of grid voltage fault (k=2.5)
../../Resources/kiiee/JIEIE.2022.36.2.028/fig4.png

(1)
id=0A,Iq=IN(0p.u.โ‰คVg<0.5p.u.)

(2)

id=โˆšI2Nโˆ’I2q,Iq=k(0.9โˆ’Vg)IN

(0.5p.u.โ‰คVg<0.9p.u.)

(3)
id=IN,Iq=0A(0.9p.u.โ‰คVgโ‰ค1.1p.u.)

(4)

id=โˆšI2Nโˆ’I2q,Iq=โˆ’k(Vgโˆ’1.1)IN

(1.1p.u.<Vgโ‰ค1.2p.u.)

id=์œ ํšจ์ „๋ฅ˜[A],iq=๋ฌดํšจ์ „๋ฅ˜[A]

iN=์ •๊ฒฉ์ถœ๋ ฅ์ „๋ฅ˜[A],Vg=๊ณ„ํ†ต์ „์••[V],k=๋น„๋ก€์ƒ์ˆ˜

Fig. 5. 3-level TNPC inverter simulation circuit (Plecs)
../../Resources/kiiee/JIEIE.2022.36.2.028/fig5.png

2.3 TNPC ์ธ๋ฒ„ํ„ฐ LVRT & HVRT Plecs ์‹œ๋ฎฌ๋ ˆ์ด์…˜

Fig 5๋Š” PLEXIM Plecs ์‹œ๋ฎฌ๋ ˆ์ด์…˜ ํšŒ๋กœ๋„์ด๋ฉฐ Plant ํšŒ๋กœ์—๋Š”3-level TNPC์ธ๋ฒ„ํ„ฐ์™€ LVRT&HVRT ๊ณ„ํ†ต ์ „์•• ์ œ์–ด ์•Œ๊ณ ๋ฆฌ์ฆ˜์ด ์ ์šฉ๋œ ์ œ์–ดํšŒ๋กœ๊ฐ€ ๋ชจ๋ธ๋ง ๋˜์—ˆ๋‹ค. Controller part ์—๋Š” d-q ๋ณ€ํ™˜์‹œ์Šคํ…œ๊ณผ ์ „๋ฅ˜ ์ œ์–ด๋ถ€, 3-๋ ˆ๋ฒจ SVPWM ํšŒ๋กœ๊ฐ€ ์žˆ์œผ๋ฉฐ ์„œ๋ธŒ์‹œ์Šคํ…œ ํšŒ๋กœ ๋‚ด๋ถ€์—๋Š” PLLํšŒ๋กœ์™€ LVRT ์œ ,๋ฌดํšจ์ „๋ ฅ ์ œ์–ด์•Œ๊ณ ๋ฆฌ์ฆ˜ ๋“ฑ์ด ๊ตฌํ˜„๋˜์—ˆ๋‹ค. Table 1์€ ์„ค๊ณ„ํ•œ ์ธ๋ฒ„ํ„ฐ์˜ ์„ธ๋ถ€ ์‚ฌ์–‘์„ ๋‚˜ํƒ€๋‚ธ๋‹ค. Fig 6์€ LVRT & HVRT ์ƒํ™ฉ์‹œ ์œ , ๋ฌดํšจ์ „๋ฅ˜์™€ ์œ , ๋ฌดํšจ์ „๋ ฅ ์ œ์–ด ๋™์ž‘์„ ๋ณด์—ฌ์ฃผ๋Š” ํŒŒํ˜•์ด๋‹ค. ํ•ด๋‹น ์‹œ๋ฎฌ๋ ˆ์ด์…˜ ์กฐ๊ฑด์—์„œ๋Š” LVRT์™€ HVRT ๊ฒฝ๊ณ„์„ ์„ ๋„˜์–ด์„œ์ง€ ์•Š๋Š” ์กฐ๊ฑด ํ•˜์—์„œ ์‹œ๋ฎฌ๋ ˆ์ด์…˜์„ ์ˆ˜ํ–‰ํ•˜๋ฏ€๋กœ ์ธ๋ฒ„ํ„ฐ๋Š” ์—ฐ๊ณ„ ์šด์ „์„ ์ง€์†ํ•œ๋‹ค. ์ƒ์„ธํ•œ ์„ค๋ช…์œผ๋กœ๋Š” 0.1s ์ดํ›„ ๊ณ„ํ†ต์ „์••์ด 1p.u.์—์„œ 0.2p.u.๋กœ ๊ฐ์†Œํ•˜๋ฉด์„œ ๋ฌดํšจ์ „๋ฅ˜๋Š” ์ตœ๋Œ€, ์œ ํšจ์ „๋ฅ˜๋Š” 0A๋กœ ํ๋ฅด๋ฉฐ ์ดํ›„ 1.6s ๊นŒ์ง€ LVRT ๋ฐ HVRT ๊ฒฝ๊ณ„์„ ์„ ๋„˜์–ด์„œ์ง€ ์•Š๋Š” ์กฐ๊ฑด์—์„œ ์ธ๋ฒ„ํ„ฐ๋Š” ๊ณ„ํ†ต์— ์ •๊ฒฉ์ •๋ฅ˜๋ฅผ ๊ณต๊ธ‰ํ•ด์ค€๋‹ค. Fig 7(a)๋Š” ๋ฐฐ์ ผ๊ณ„ํ†ต ๊ธฐ์ค€์˜ LVRT ๋™์ž‘ ์‹œ๋ฎฌ๋ ˆ์ด์…˜์„ ๋ณด์—ฌ์ค€๋‹ค. 0.1s ์ดํ›„ ๋™์ž‘์€ ๊ณ„ํ†ต์ „์••์ด ์ •๊ฒฉ์˜ 50% ์ดํ•˜์ผ ๋•Œ 150ms ํ›„ ์ธ๋ฒ„ํ„ฐ ์šด์ „์ด ์ค‘์ง€๋˜๋Š” ๋ชจ์Šต์„ ๋ณด์—ฌ์ค€๋‹ค. 0.1s ์ „ ํ›„๋กœ ์œ , ๋ฌดํšจ์ „๋ฅ˜๋Š” ๋ฐ˜์ „๋œ ํŠน์ง•์„ ๋ณด์—ฌ์ฃผ๋ฉฐ ์ด๋Š” 1p.u.์™€ 0.5p.u.์—์„œ ๊ฐ๊ฐ ์‹ (3) ๊ณผ ์‹(1) ๋กœ LVRT ๋™์ž‘์ด ๊ตฌํ˜„๋œ ๊ฒƒ์ž„์„ ์•Œ ์ˆ˜ ์žˆ๋‹ค. Fig 7(b) ์—ญ์‹œ ๋ฐฐ์ ผ๊ณ„ํ†ต LVRT ๊ธฐ์ค€์œผ๋กœ ์ˆ˜ํ–‰ํ•œ LVRT ๋™์ž‘ ์‹œ๋ฎฌ๋ ˆ์ด์…˜์œผ๋กœ์จ 0.1s๏ฝž0.2s ๊ตฌ๊ฐ„๋™์•ˆ 0.55p.u.์˜ ๊ณ„ํ†ต์ „์••์ด 0.2s ์ดํ›„ 0.75p.u.๋กœ ์ฆ๊ฐ€ํ•˜์˜€์„ ๋•Œ์˜ LVRT ๋™์ž‘์„ ๋ณด์—ฌ์ค€๋‹ค. 0.55p.u.๋Š” 160ms์ด๋‚ด ํŠธ๋ฆฝ ๋˜์–ด์•ผ ํ•˜์ง€๋งŒ 100ms ์ดํ›„ 0.75p.u.๊ฐ€ ๋˜์—ˆ์„ ๋•Œ 1.5s๊นŒ์ง€ ์šด์ „์ง€์† ์˜์—ญ์ด ์—ฐ์žฅ๋œ๋‹ค. ๋ณธ ์‹œ๋ฎฌ๋ ˆ์ด์…˜์—์„œ๋Š” ๊ณ„ํ†ต์ „์••์ด 0.55p.u.๊ฐ€ ๋˜๋Š” ์‹œ์ ๋ถ€ํ„ฐ ์ธ๋ฒ„ํ„ฐ ์šด์ „์ด ์ค‘๋‹จ๋˜๋Š” ์‹œ์ ๊นŒ์ง€ 1.5s๊ฐ€ ์†Œ์š”๋˜๋Š”๊ฒƒ์„ ํ†ตํ•ด ๋ฐฐ์ „๊ณ„ํ†ต LVRT ์•Œ๊ณ ๋ฆฌ์ฆ˜์˜ ์ ์šฉ์„ ๊ฒ€์ฆํ•˜์˜€๋‹ค. Fig 8(a)๋Š” ์†ก์ „๊ณ„ํ†ต LVRT ๊ธฐ์ค€์œผ๋กœ ์ˆ˜ํ–‰ํ•œ ์‹œ๋ฎฌ๋ ˆ์ด์…˜์œผ๋กœ์จ 0.3s๋ถ€ํ„ฐ ์‹œ์ž‘๋˜๋Š” 0.75p.u.์˜ ๊ณ„ํ†ต์ „์••์ด 0.5s ์ดํ›„ ๊ฐ์†Œํ•˜๊ธฐ ์‹œ์ž‘ํ•˜์—ฌ 0.4p.u.๊นŒ์ง€ ๊ฐ์†Œํ•˜๋Š” ๋™์•ˆ 770ms์˜ ์‹œ๊ฐ„์ด LVRT ํŠธ๋ฆฝ ๊ฒฝ๊ณ„์„ ๊ณผ ๋งž๋‹ฟ์•„ LVRT ํŠธ๋ฆฝ ๋™์ž‘์ด ๋ฐœ์ƒ๋˜๋Š” ๋ชจ์Šต์„ ๋ณด์—ฌ์ค€๋‹ค. ๋˜ํ•œ Fig 8(b)๋„ Fig 8(a)์™€ ๋งˆ์ฐฌ๊ฐ€์ง€๋กœ ์†ก์ „๊ณ„ํ†ต LVRT ๊ธฐ์ค€์œผ๋กœ ์ˆ˜ํ–‰ํ•œ ์‹œ๋ฎฌ๋ ˆ์ด์…˜์œผ๋กœ์จ 0.2s์—์„œ 0.15p.u.๊นŒ์ง€ ๊ณ„ํ†ต์ „์••์ด ๊ฐ์†Œํ•˜์ง€๋งŒ, 0.8p.u๊นŒ์ง€ ์ „์••์ด ์ƒ์Šนํ•˜๋Š” ์‹œ๊ฐ„์ด LVRT ๊ฒฝ๊ณ„์„ ์„ ๋„˜์–ด์„œ์ง€ ์•Š์œผ๋ฏ€๋กœ ํŠธ๋ฆฝ๋˜์ง€ ์•Š๋‹ค๊ฐ€ 0.8p.u. ๊ฐ€ ์ง€์†๋˜๋ฉด์„œ 0.2s๋กœ๋ถ€ํ„ฐ 1350ms๊ฐ€ ํ๋ฅธ ์ง€์ ์—์„œ ์ธ๋ฒ„ํ„ฐ ๋™์ž‘์ด ์ค‘์ง€ ๋œ ๊ฒƒ์„ ํ†ตํ•ด LVRT ์ƒํ™ฉ์„ ๋ชจ๋ธ๋ง ํ•˜์˜€๋‹ค. Fig 9(a)๋Š” ์†ก์ „๊ณ„ํ†ต ์—ฐ๊ณ„๊ธฐ์ค€์— ์กด์žฌํ•˜์ง€ ์•Š๋Š” LVRT ์•Œ๊ณ ๋ฆฌ์ฆ˜์„ ์ถ”๊ฐ€ํ•˜์—ฌ ์‹œ๋ฎฌ๋ ˆ์ด์…˜์„ ์ˆ˜ํ–‰ํ•œ ๋‚ด์šฉ์œผ๋กœ์จ, 0.2s ์ดํ›„ 0.8s ๊นŒ์ง€ 0.7p.u์˜ ๊ณ„ํ†ต์ „์••์ด ์„œ์„œํžˆ ์ฆ๊ฐ€ํ•˜๋ฉด์„œ dead band์ธ 0.9p.u.๋กœ ๋„˜์–ด ์„ค ๋•Œ ๊นŒ์ง€๋Š” LVRT ๊ฒฝ๊ณ„์„ ์„ ๋„˜์–ด์„œ์ง€ ์•Š์œผ๋ฏ€๋กœ ์ธ๋ฒ„ํ„ฐ์˜ ์ถœ๋ ฅ์€ ๊ณ„์† ๋˜์ง€๋งŒ, 1.1p.u.๋ถ€ํ„ฐ์ „์••์ด ์ฆ๊ฐ€ํ•˜๋Š” 1.2s๏ฝž1.4s ๊ตฌ๊ฐ„๋™์•ˆ 200ms์˜ ์‹œ๊ฐ„์ด์ง€๋‚˜๋ฉด์„œ HVRT ํŠธ๋ฆฝ ๋™์ž‘์ด ์‹คํ–‰๋œ ๊ฒƒ์„ ๋ณด์—ฌ์ค€๋‹ค. ๋˜ํ•œ Fig 9(b) ๋Š” ์•ž์„œ Fig 9(a) ์™€ ์œ ์‚ฌํ•œ HVRT ๋™์ž‘์œผ๋กœ ๋ณด์ด์ง€๋งŒ, 1.1p.u. ์ดํ›„ 200ms์˜ ์‹œ๊ฐ„์ด ์ง€๋‚˜๊ธฐ ์ „ ๊ณ„ํ†ต์ „์••์ด 1.2p.u.๋กœ ์ƒ์Šนํ•˜๋ฉด์„œ HVRT ํŠธ๋ฆฝ๋™์ž‘๊ณผ ํ•จ๊ป˜ ์ธ๋ฒ„ํ„ฐ ์ถœ๋ ฅ์ด ์ค‘๋‹จ๋˜์—ˆ๋‹ค. ์—ฌ๊ธฐ์„œ 0.1s ์ดํ›„ 0.2p.u.๋ถ€ํ„ฐ 0.9p.u. ๊นŒ์ง€ ์ „์••์ด ์ƒ์Šนํ•˜๋Š” ์˜์—ญ ์—์„œ๋Š” ๊ณ„ํ†ต์ „์••์ด LVRT ๊ฒฝ๊ณ„์„ ์„ ๋„˜์–ด์„œ์ง€ ์•Š๊ณ  ๊ณ„์†ํ•ด์„œ ์ƒ์Šนํ•˜๋ฏ€๋กœ LVRT ํŠธ๋ฆฝ ๋™์ž‘์ด ๋ฐœ์ƒํ•˜์ง€ ์•Š์œผ๋ฉฐ, ๊ณ„ํ†ต ์ „์•• ๋ฒ”์œ„์— ๋”ฐ๋ผ ์œ  , ๋ฌดํšจ์ „๋ฅ˜ ๊ณต๊ธ‰์ด ์‹ (1), (2), (3), (4) ๊นŒ์ง€ ๋ชจ๋‘ ๊ตฌํ˜„๋œ ๊ฒƒ์„ ํ™•์ธํ•˜์˜€๋‹ค.

Table 1. Design specifications of the three-level TNPC inverter

Specifications

Values

Input Voltage, Vdc

800V

Rated output power

100kW

Grid voltage, Vg

220Vdc

Rated Output Current, In

145Arms

Switching frequency, fs

20kHz

Filter inductance 1, Lf1

200uH

Filter inductance 2, Lf2

200uH

Fig. 6. Simulation waveform of active and reactive current injection performance in LVRT & HVRT situation
../../Resources/kiiee/JIEIE.2022.36.2.028/fig6.png

Fig. 7. LVRT performance simulation waveform based on the grid voltage fluctuation condition of the KEPCO distribution system grid connection technology standard
../../Resources/kiiee/JIEIE.2022.36.2.028/fig7.png

Fig. 8. Simulation waveform of LVRT performance under grid voltage fluctuation condition of KEPCOโ€™s transmission system grid connection technology standard
../../Resources/kiiee/JIEIE.2022.36.2.028/fig8.png

Fig. 9. Simulation waveform of active and reactive current injection performance in LVRT & HVRT situation
../../Resources/kiiee/JIEIE.2022.36.2.028/fig9.png

3. ๊ฒฐ ๋ก 

๋ณธ ๋…ผ๋ฌธ์—์„œ๋Š” ํ•œ๊ตญ์ „๋ ฅ๊ณต์‚ฌ์˜ ์†ก์ „๊ณ„ํ†ต๊ณผ ๋ฐฐ์ „๊ณ„ํ†ต ๊ทœ์ •์—์„œ ์ œ์‹œํ•˜๋Š” LVRT, HVRT ๊ธฐ์ค€์„ ๋ถ„์„ํ•˜์˜€์œผ๋ฉฐ, ๋ฐฐ์ „๊ณ„ํ†ต์˜ LVRT ๊ธฐ์ค€๋ณด๋‹ค ๊ณ„ํ†ต ์œ ์ง€๊ธฐ์ค€์ด ์ƒ๋Œ€์ ์œผ๋กœ ์—„๊ฒฉํ•œ ์†ก์ „๊ณ„ํ†ต ๊ธฐ์ค€์—์„œ ํฌํ•จ๋˜์ง€ ์•Š์€ HVRT ๊ธฐ์ค€์„ ์ถ”๊ฐ€ํ•˜์—ฌ ๋ถ„์„ ๋ฐ ์‹œ๋ฎฌ๋ ˆ์ด์…˜์„ ์ˆ˜ํ–‰ํ•˜์˜€๋‹ค. ์ˆ˜ํ–‰๋œ ์‹œ๋ฎฌ๋ ˆ์ด์…˜์€ 3-LEVEL TNPC ์ธ๋ฒ„ํ„ฐ์— LVRT, HVRT ์•Œ๊ณ ๋ฆฌ์ฆ˜์„ ์ ์šฉํ•˜์—ฌ ๊ตฌํ˜„ํ•˜์˜€์œผ๋ฉฐ K=2.5๋ฅผ ๊ธฐ์ค€์œผ๋กœ ํ•œ ์œ , ๋ฌดํšจ์ „๋ฅ˜ ์ฃผ์ž… ๊ธฐ์ค€์„ ๊ธฐ๋ฐ˜์œผ๋กœ ์œ , ๋ฌดํšจ์ „๋ ฅ ์ œ์–ด ๋™์ž‘์ด ๊ตฌํ˜„๋˜๋Š” ๊ฒƒ์„ ํ™•์ธํ•˜์˜€์œผ๋ฉฐ, ๋ฐฐ์ „๊ณผ ์†ก์ „๊ณ„ํ†ต ์—ฐ๊ณ„๊ธฐ์ค€์˜ LVRT, HVRT ์กฐ๊ฑด์„ ๋‹ค์–‘ํ•œ ์ผ€์ด์Šค์˜ ์‹œ๋ฎฌ๋ ˆ์ด์…˜ ๋ชจ๋ธ๋ง์„ ํ•จ์œผ๋กœ์จ LVRT์™€ HVRT ๋™์ž‘์„ ์ƒ์„ธํžˆ ๋ถ„์„ํ•˜์˜€๋‹ค.

Acknowledgements

This work was supported in part by the National Research Foundation of Korea (NRF), Korea government(MSIT) (No. NRF2020R1A2C2099663) and in part by the Ministry of Trade, Industry and Energy, Korea, under the โ€œRegional Innovation Cluster Development Program (R&D, P0016220)โ€ supervised by the Korea Institute for Advancement of Technology(KIAT).

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Biography

Hyun-Bin Jo
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He received the B.S. degree in electronic engineering from Catholic University, Bucheon, South Korea, in 2016.

He is currently pursuing his M.S. and Ph.D. degrees at the Department of Energy System Engineering, Chung-Ang University, Seoul.

His current research interests include Grid connected Inverter and high-voltage pulsed-power supply systems.

Jong-Beom Park
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He is pursuing the B.S. degree at the Department of Energy System Engineering, Chung-Ang University, Seoul. South Korea, in 2016.

His research interests include power electronics and Grid connected Inverter.

Jae-Beom Ahn
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He received the B.S. degree in electronic engineering from Kook-min University, Seoul, South Korea, in 2019.

He is currently pursuing the integrated M.S. and Ph.D. degrees at the Department of Energy System Engineering, Chung-Ang University, Seoul.

His current research interests include power electronics, high-voltage pulse power systems and arc fault detection in DC PV systems.

Seung-Beom Lim
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He received his B.S., M.S., and Ph.D. degrees in Electrical Engineering from Dankook University, Yongin, Korea, in 2004, 2006, and 2014, respectively.

Since 2007, he has been a General Manager of ESS R&D department on EON Co., Ltd., Anyang, Korea.

His current research interests include multi-level converters/inverters, high-power density converter/inverter design, and modular UPSs.

Hong-Je Ryoo
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He received the B.S., M.S., and Ph.D. degrees in electrical engineering from Sungkyunkwan University, Seoul, South Korea, in 1991, 1995, and 2001, respectively.

From 2004 to 2005, he was a Visiting Scholar with WEMPEC, University of Wisconsin-Madison, Madison, WI, USA.

From 1996 to 2015, he joined the Electric Propulsion Research Division as a Principal Research Engineer, the Korea Electrotechnology Research Institute, Changwon, South Korea, where he was a Leader with the Pulsed Power World Class Laboratory, a director of Electric Propulsion Research Center.

From 2005 to 2015, he was a Professor with the Department of Energy Conversion Technology, University of Science and Technology, Deajeon, South Korea.

In 2015, he joined the School of Energy Systems Engineering, Chung-Ang University, Seoul, where he is currently a Professor.

His current research interests include pulsed-power systems and their applications, as well as high-power and high-voltage conversions.

Prof. Ryoo is the cooperation vice president of the Korean Institute of Power Electronics, a editorial director of the Korean Institute of Electrical Engineers, and the Vice President of the Korean Institute of Illuminations and Electrical Installation Engineers.