25 Journal of Technology, Vol. 30, No. 1, pp. 25-31 (2015) 1, * 2 3 1 2 3 ( Microinverter) (Centralized) (String) 250 W 60/72 Cell 230 W 220 V UL 1741 A SINGLE-STAGE GRID-CONNECTED MICROINVERTER WITH UNITY-POWER-FACTOR FOR PHOTOVOLTAIC APPLICATIONS Ching-Ming Lai 1, * Hsien-Peng Yu 2 Wei-Chih Liu 3 1 Departent of Vehicle Engineering National Taipei University of Technology Taipei, Taiwan 106, R.O.C. 2 Graduate Institute of Mechanical and Electrical Engineering National Taipei University of Technology Taipei, Taiwan 106, R.O.C. 3 UPE-Power Technology Co., Ltd. Taichung, Taiwan 420, R.O.C. Key Words: icro-inverter, Interleaved flyback converter topology. ABSTRACT Grid-connected photovoltaic () icro-inverters deliver the solar energy fro a single panel to AC utility. Copared with conventional centralized/string inverters, icro-inverters have several advantages, such as higher axiu power tracking efficiency, easier installation, lower *e-ail: peclai@gail.co Corresponding author: Ching-Ming Lai, e-ail: peclai@gail.co
26 unit price and a longer life-tie. In this paper, a single-stage -connected icro-inverter based on interleaved flyback converter topology is presented. First, the circuit topology and syste operation principle of the studied icro-inverter are introduced. The design considerations of the key coponents are also described. To coply with the UL 1741 regulation, the realized syste onitors the voltage, current as well as frequency/phase, and then these paraeters are cobined with the passive detection ethod to prevent the islanding phenoenon. Finally, a prototype with input power rating of 250 W and output power rating of 230 W/220 Vac is constructed and copatible with 60 cell and 72 cell solar odules applications. Experiental results verify the feasibility of the developed icro-inverter. 2012 100 GW 2007 300 W 1 (single-stage) (two-stage) [1, 2] 100 W~300 W [3, 4] [5][6][7-9] (axiu power point tracking control) (pulse-width odulation, PWM) (unfolder) (boost converter) 200 V 400 V (discontinuous conduction ode, DCM) 50% 50% 50% SOLAR PANEL 1 SOLAR PANEL 2 SOLAR PANEL 3 100% 100% 50% SOLAR PANEL 1 SOLAR PANEL 2 SOLAR PANEL 3 1 (unity-power-factor) 2 (S 1, S 2 ) ( S 1g, S 2g ) (rectified sinusoidal reference)
27 Interleaved Flyback Converter H-bridge Unfolder Module C in EMI Filter i pri1 i pri2 S H1 S H2 L o1 D 1 D 2 N p1 N p2 C bus i sec1 i sec2 L o2 C o Grid S 1 S 2 N s1 N s2 S L1 S L2 2 Module Interleaved Flyback Converter H-bridge Unfolder EMI Filter i Grid S 1g S 2g Current Regulator#1 Current Regulator#2 i DSP Controller (iref calculation) i S H1g S H2g S L2g S L1g + _ v v Zero-Crossing Detection &PLL i v P&O MPPT i Rectifier 4 (D 1, D 2 ) (S H1, S H2, S L1, S L2 ) ( S H1g, S H2g, S L1g, S L2g ) S H1 S L2 S H2 S L1 3 180 / 4 (zero-crossing detection, ZCD) (phase-locked loop, PLL) (reference current envelope) (MPPT) (current regulator) i pri1 i pri2 i sec1 i sec2 S 1g S 2g S H1g S L2g S H2g S L1g 3 /
28 i V (0.5 V I = P ) K (5) V i 5 I pk V pv/l 1 I pk/n 1 DCM Operation Reflection fro priary to secondary 1 L K 4P V T (5) s (6) 1 L d 4P sint (6) V Ts V /N 2 L 1 DT s D 1T s T s 6 返馳式轉換器 DCM 1. 4 5 (i = Kv ) 6 (1) 1 I pk i isec d1 (1) 2 N V V I pk d Ts ; d1 Nd L v (1) (2) i 2 2 d VTs 2L v (2) (average duty cycle) (3) K v d ; v V sint (3) V (3) (2) (4) V P i = Kv (7) D MAX D (7) 1, MIN 1 (voltage-second balance) (8) D MAX NV (1 ) 1 (8) V (6) (8) (9) T NV s L V (1 ) 4P V PQ3225/PC95 250 W ( 125 W) V = 30 V 78 khz N s1 /N p1 = N s2 /N p2 = 7 (9) 6 uh 2. () (Δv in ) (10) 2 (9) i K V T 2L 2 2 s 2 V v (4) C in P V v in (10)
29 V_PRI V_SEC + Interleaved Flyback & Feedback H-Bridge Unfolder - EMI- Filter L1 N L2 V I S1g S2g SH1g~SH2g SL1g~SL2g Micro Controller PWM1 PWM2 OUT_H OUT_L VAC IAC Photocoupler & Gate Driver Photocoupler & Gate Driver AC Feedback Circuit 7 所研製之單級太陽能微型逆變器 = 2 f = 120 (angular frequency) 250 W V = 50 V v in = 2 V C in = 6.6 F 4 1.8 F/63 V 3. (R DS = 7.2 ) IPB072N15N3G 150 V/100 A C2D05120E 1200 V/5 A CoolMOS 150 V/17 A 0.29 Paraeter Values/Part No. Input capacitor bank (C in ) 1800 uf/63 V 4 pcs Magnetizing inductance (L 1, L 2 ) 6 uh Transforer turn-ratio (N 1, N 2 ) N s1 /N p1 = N s2 /N p2 = 7 Priary power MOSFET (S 1, S 2 ) IPB072N15N3G Secondary power diode (D 1, D 2 ) C2D05120E H-bridge unfolder (S H1, S L1, S H2, S L2) SPB17N80C3 Bus filter capacitor (C bus ) 22 nf/310 V 2 pcs Output filter Inductance (L o1, L o2 ) 150 uh Output filter Inductance (C o ) 0.33 uf/330 V 7(a) Microchiop dspic33fj16gs504t [(0.1805z-0.1595)/(z-1)] 7(a) 7(b) () V dc 25-59 V v o,rs 220 V() P o 230 W() f o 60 Hz 8 C bus (S L1g, S L2g ) [2s/div] 圖 8 直流鏈電壓 [CH2:100 V/div] 以及相對應開關閘極訊號 (CH1:S L1, CH3:S L2 ) [5 V/div] 9 230 W 5% IEEE 1547 93% 10 250 W
30 [5s/div] 9 v o [CH2200 V/div] i o [CH40.5 A/div] 11 [X axis: 3A/div, Y axis: 70W/div] (X-Axis,Y axis ) [2s/div] 10 250 W v [CH1offset = 29 V, 1V/div] i [CH45 A/div] 12 ( Chroa 62100H- 600S ) Chroa 62100H-600S I-V/P-V (perturbation and observation, P&O) 10 V oc 34.8 V V p 29.67 V 0 A 8.33 A 9 11 11 12 P-V UL 1741 [10] RLC (R = 185 L = 194 HC = 35.7 uh) 13 3 250 W 60/72 Cell 230 W
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