Embed Size (px)
DESCRIPTION
3 + V in – – V out + i L L C i C I i d i in Practice Problem Hint #1: This is a buck-boost converter Hint #2: P in = P out P in = DV in I L = V in I in P out = V out I out Hint #3: I C = 0 I out = (1-D) I L i in ILIL V in DT Since the input voltage is constant only the dc component of i in contributes to Pin ! t
Citation preview
1
150V
T T2 T 0
0V
Practice ProblemThe periodic waveform shown is applied to a 100Ω resistor. What value of α yields 50W average power to the resistor?
2 2, (1 )0RMS TRI RMSV V
22 150
3RMSV
α is the “duty cycle”
2RMSV PR
23
2
+
Vin –
– Vout
+ iL L C iC
Iout
id iin
4a. Assuming continuous conduction in L, and ripple free Vout and Iout , draw the “switch
closed” and switch open” circuits and use them to develop the in
outVV
equation.
4b. Consider the case where the converter is operating at 50kHz, Vin = 40V, Vout = 120V, P =
240W. Components L = 100µH, C = 1500µF. Carefully sketch the inductor and capacitor currents on the graph provided.
4c. Use the graphs to determine the inductor’s rms current, and the capacitor’s peak-to-peak
current. 4d. Use the graphs to determine the capacitor’s peak-to-peak ripple voltage.
Practice Problem
3
+
Vin –
– Vout
+ iL L C iC
Iout
id iin
Practice Problem
Hint #1: This is a buck-boost converter
Hint #2: Pin = Pout
Pin = DVin IL = VinIin
Pout = Vout Iout
Hint #3: IC = 0
Iout = (1-D) IL
iin
IL
Vin
DT
Since the input voltage is constant only the dc component of iin
contributes to Pin
!
t
4
December 16 was a brilliant solar day here in Austin. Consider a PV installation that has 60º tilt, and 225º azimuth (i.e., facing southwest). Use the following equation,
2/)cos()cos(
)( mWDHGHDHP incidentzenithsun
incident
,
and the graphs on the following page to estimate 5a. the maximum incident solar power density on the panels (in W/m2), and 5b. the time at which the maximum occurs.
Practice Problem
5
Sun Zenith Angle (Top Curve), and Incident Angle on Panel (Bottom Curve), for Dec. 16
(Panel Tilt and Azimuth = 60 and 225 Degrees, Respectively)
0
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
11 11.5 12 12.5 13 13.5 14 14.5 15 15.5 16 16.5 17
Hour of Day
Deg
rees
Global Horizontal (Top Curve), and Diffuse Horizontal (Bottom Curve), for Dec. 16
0
50
100
150
200
250
300
350
400
450
500
550
600
650
11 11.5 12 12.5 13 13.5 14 14.5 15 15.5 16 16.5 17
Hour of Day
Wat
ts P
er S
quar
e M
eter
Zenith
Incident
GH
DH
