Question

Exercise 1

Suppose you are given a single-phase inverter using a unipolar PWM switching thod. Given the DC input as 50 V and the output load is a combination of resistance R = 5Ω and inductance L = 40 mH. You are required to design the necessary parameters in order for the inverter to operate with the 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 the necessary parameters that need to be determined? (other than the given parameters). Modulation index to be used? Switching frequency to be used?

Assumption that can be made to simplify the design process?

Exercise 2

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

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

Exercise 3

The South Korean which is using a 380 kV_l-l,rms , 60 Hz 3-phase system is planning to sell electricity to Japan which is using a 210 kV_l-l,rms , 50 Hz 3-phase system. As for the implementation, a HVDC transmission line is proposed for the 214 km power transmission line between Fukuoka in Japan to Busan in South Korea. The conductor used for the undersea transmission line has a total resistance of 15Ω and inductance of 15 mH. The Japanese is set to receive 500 MW of clean power daily from the Korean side. As part of the team implementing the project, you are required to design the necessary parameters for the operation of the HVDC system. The following steps will help you in the design process.

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

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

Thankyou :)

Answer 1