Exercise 1

Suppose you are given a single-phaseinverter using a unipolar PWM switching thod. Given the DC input as50 V and the output load is a combination of resistance R= 5Ω and inductance L = 40 mH. You are required to designthe necessary parameters in order for the inverter to operate withthe following condition.

1. a fundamental output of 22.5 Vpk at 50 Hz frequency
2. the current THD of less than 15%

Hint: In this question what are thenecessary parameters that need to be determined? (other than thegiven parameters). Modulation index to be used? Switching frequencyto be used?

Assumption that can be made tosimplify the design process?

Exercise 2

A single-phase square-wave inverterwith a 250 V DC input voltage is operating at a frequency of 50 Hz.The inverter output is connected to the load which is combinationof resistance R = 15Ω and inductance L = 33mH.

1. study the effect of varying the frequency operation at ±50%from the original frequency of 50Hz to the fundamental output loadcurrent. Give your conclusion.
2. study the effect of varying the frequency operation at ±50%from the original frequency of 50Hz to the load current THD. Giveyour conclusion.
3. study the effect of varying the frequency operation at ±50%from the original frequency of 50Hz to the power produced at theload. Give your conclusion.

Exercise 3

The South Korean which is using a 380kV_l-l,rms , 60 Hz 3-phase system is planning to sellelectricity to Japan which is using a 210 kV_l-l,rms , 50Hz 3-phase system. As for the implementation, a HVDC transmissionline is proposed for the 214 km power transmission line betweenFukuoka in Japan to Busan in South Korea. The conductor used forthe undersea transmission line has a total resistance of 15Ω andinductance of 15 mH. The Japanese is set to receive 500 MW of cleanpower daily from the Korean side. As part of the team implementingthe project, you are required to design the necessary parametersfor the operation of the HVDC system. The following steps will helpyou in the design process.

1. set the appropriate transmission line DC voltage at the receiveside, determine the required delay angle at the receiver side’sconverter
2. determine the required DC current based on the amount of powerreceived, as well as the voltage drop along the transmission lineand the losses
3. based on (ii.), determine the voltage and the required angle atthe sender side’s converter
4. Analyse the peak-to-peak variation in the DC current based onthe first two AC terms

Based on your answer from (i.) to(iv.), in case the team need to improve the losses and ripplecurrent performance to about 50% from its current condition,suggest which design parameters to be changed. Verify your answerthrough calculation.

Thankyou :)