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In this thesis we propose a top-down design method for air-
conditioners drivenby inverters. We adopt the CLF/CLTD method
and use the parameters of the structu and collected data of the
weather to calculate the cooling load induced from heat sources.
We modified the thermal equivalent model in Matlab and propose a
practical model which includes the calculation of cooling load.
Using this new method, we design three temperature controllers,
those are(1) ON-OFF controller, (2) P controller. and (3) PI
controller. The simulation results show that P controller
already works very well. We also study the method to design the
inverter for the air-conditioner. The inverter with three-phase
PWM outputsis our choice. Five different modulation waveforms
have been considered and analyzed here, those are sinusoidal
wave, sinusoidal wave with the third harmoniccomponent, "2/5"
trapezoidal wave, space vector wave, and modified
trapezoidalwave. After the comparison of the five associated
utilization of the dc voltages and the accumulated total
harmonic distortions, we find that the 2/5 trapezoidal
modulation wave is the best choice in our design. We use the
circuit board with 8051 CPU to implement the function of the
inverter. By carefully evaluating the performance of 8051, we
propose a look-up table method to synthesize three-phase 2/5
trapezoidal PWM waves.The results have shown that our method can
utilize the performance of 8051 to the upmost.The frequency
modulation indices can be designed up to 21~23. This result
shows our implementation method is pretty practical.
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