Question

2. Renewable energy system requires a boost converter with input voltage variation of 18 V to 42 V (de) and gives output of 120 V at 0.6 kW. For the converter the switching frequency is set at 50 kHz. a) Find the operating duty cycle range for each switch of the converter0 marks b) 196 What is the inductor value which should keep inductor current variation below under all input voltages [30 marks] c) Find the capacitor value which should keep voltage ripple 0.05 V [20 marks] d) If your load start to draw variable power from 8 kW to 15 kW what will be the smallest new switching frequency you need to have to make the inductor current ripple always below 1 % 30 marks If you decide to use a buck-boost converter for this application, what will the resultant average inductor current when output load is at 0.6 kW and input voltage is at 42 V e) [10 marks]

Answer 1

18-42v 5 CON) 0 T -whern switch is off er吋リ Volt-Sec Balaroc, eguaton. -2 A veyage voltag I- D

0 V o 18120V D 12018 0. 85 20 D 120-42 = 0-6 5 2 O Ameri-Sec Balance equat ons Average crwurt thy 0 O N (avg) AIL DT Vo= Vs に0 V I2o When V-18 p:0.85 (1-0) D Vo 0:0

(o O) = 30,6 mH (Charge) Astra under the ONpOuod 0 Vo supple Vol 600 o os f t m

1 2 DE 0.65 0.os

d) レ LA J Vo = 120 Tv 드24n 5 2. 2 4 L: 30.6-mW 1 8 2- D f: (0.358) (1-0:358) Xui 38-17 kHz 30. 6 x 0. 0l 51.6 KHz whem Vs 12 516 Vo 438-17-1 1- 4 2 f ะ 6.904) (1-o.gov)X y38,17 KHz:

1 Ic Buck Boost Convehte

on volt ec bolaum u ejuohon I- D от 12.0 し12-0 12 0 12o02 D D 120 0.74 2. 0 from e9uahJn Avenage indudex usremt Ttont) Ltav I- D -0.74 I.