ATTACH THIS SHEET AS THE FIRST PAGE OF YOUR ASSIGNMENT
Assignment 6, ECE 464, FS 08 Name:__________________________
Due: Nov. 10, 2008; 9:00 AM READING: Chapter 6 Score:__________
6.1) A single-phase, full-bridge inverter has a switching frequency of 100 Hz and a DC
voltage of 200 V. The inverter is not using pulse-width modulation; instead, it is just
producing a square-wave output into a series RLC load. If the resistance of the load is 3
ohms, the inductance is 10 mH, and the capacitance is chosen so that the resonant
frequency is 10 Hz, then plot the steady-state current waveform in the load.
6.2) A single-phase, full-bridge, pulse-width modulated inverter is used to drive an RL
load. The DC voltage is 310 V. Assume the carrier is a triangle wave that varies, from a
minimum of zero and a maximum of one, with a relatively high frequency. Choose a duty
cycle command that will produce a load voltage of 150 Vrms at 45 Hz.
6.3) Repeat 6.2) for a three-phase inverter with a wye-connected load. The output
voltage should instead be 200 Vrms, 60 Hz, line-to-line.
6.4) A single-phase, pulse-width modulated, full-bridge inverter has IGBTs with parallel
diodes for switches. Assume the voltage drop across the switch is 1.5 V when either the
diode or IGBT conducts (in reality, their voltage drops are a little different). If the DC
voltage into the converter is 400 V, then what is the efficiency of the inverter? If the DC
voltage is 800 V, then what is the efficiency? What if the DC voltage is 48 V?
6.5) The solar inverter sketched below consists of three main parts: a boost converter that
tracks the maximum power, an inverter that produces PWM AC, and a 60-Hz transformer
that steps up the voltage to the power grid. The inverter connects a single PV panel to
The entire solar inverter needs to be 96% efficient at full power (as shown).
a) If the transformer is 99% efficient, and the boost converter is 98% efficient, then what
must the efficiency of the PWM inverter be? Is this reasonable given the answers in
6.4)?
b) Write down the expression for the instantaneous output power of the solar inverter.
Assuming solar inverter is essentially 100% efficient, and the DC voltage from the PV
panel is essentially constant, what current must be filtered by the capacitor?
Boost
Converter Full-Bridge
1-phase
PWM Inverter
60-Hz
Transformer
PV
Panel
~24 VDC ~48 VDC ~35 Vrms
60 Hz
Grid
220Vrms
60 Hz
Solar Inverter 1 Arms
60 Hz