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Choice of converter configuration
- 1. Choice of converterconfiguration content Converter configuration Analysis of 12 Pulse converter Prepared By Mr.K.Jawahar, M.E., Assistant Professor Department of EEE Choice of converter configuration Kongunadunadu College of Engineering and Technology Department of EEE
- 2. Choice of converter configuration 1. Pulse number • The number of pulsations ( cycle of ripple ) per cycle of alternating voltage. • The conversion from AC to DC involves switching sequentially different sinusoidal voltages on to the DC circuit. • The output voltage of the converter consists of a DC component and a ripple whose frequency is determined by the pulse number. hdc= np hac= np ± 1 Choice of converter configuration Kongunadunadu College of Engineering and Technology Department of EEE
- 3. 2. Valve and switches • It can be treated as switch which can be turned on at any instant, provided the voltage across it is positive. • A diode is an uncontrolled switch which will turn on immediately after the voltage becomes positive where as thyristors switching can be delayed by an angle. • the opening of the switch (both for diode and thyristor) occurs at the current zero. Choice of converter configuration Kongunadunadu College of Engineering and Technology Department of EEE
- 4. 3. Converter configuration • The configuration for given pulse number is selected in such a way that both the valve and transformer utilization are maximized. • converter configuration can be defined as basic commutation group and the number of groups connected in series and parallel. Kongunadunadu College of Engineering and Technology Department of EEE Choice of converter configuration
- 5. 4. Valve rating • The valve rating is specified in terms of PIV. The ratio of PIV to the average dc voltages is an index of the valve utilization. 𝑣 𝑑𝑜 = 𝑆 𝑞 2𝜋 −𝜋 𝑞 𝜋 𝑞 𝐸 𝑚 𝑐𝑜𝑠𝜔𝑡 𝑑𝜔𝑡 • −𝜋 𝑞 𝜋 𝑞 𝐸 𝑚 𝑐𝑜𝑠𝜔𝑡 𝑑𝜔𝑡 =2 0 𝜋 𝑞 𝐸 𝑚 𝑐𝑜𝑠𝜔𝑡 𝑑𝜔𝑡 𝑝𝑟𝑖𝑜𝑟𝑖𝑡𝑦 𝑖𝑠 𝑒𝑣𝑒𝑛 𝑣 𝑑𝑜 = 2𝑆 𝑞 2𝜋 0 𝜋 𝑞 𝐸 𝑚 𝑐𝑜𝑠𝜔𝑡 𝑑𝜔𝑡 = 2𝑆 𝑞𝐸 𝑚 2𝜋 sin 𝜔𝑡 0 𝜋 𝑞 = 𝑆 𝑞𝐸 𝑚 𝜋 𝑠𝑖𝑛 𝜋 𝑞 − 0 = 𝑆 𝑞𝐸 𝑚 𝜋 𝑠𝑖𝑛 𝜋 𝑞Kongunadunadu College of Engineering and Technology Department of EEE Choice of converter configuration
- 6. 5. Peak inverse voltage • If q is even, 𝑃𝐼𝑉 = 2𝐸 𝑚 • If q is odd, 𝑃𝐼𝑉 = 2𝐸 𝑚 𝑐𝑜𝑠 𝜋 2𝑞 6. Utilization factor The ratio of PIV to the average DC voltage is known as utilization factor. For q is even 𝑃𝐼𝑉 𝑉 𝑑𝑜 = 2𝐸 𝑚 𝐸 𝑚 𝑆𝑞 𝜋 𝑠𝑖𝑛 𝜋 𝑞 𝑃𝐼𝑉 𝑉𝑑𝑜 = 2𝜋 𝑆𝑞𝑠𝑖𝑛 𝜋 𝑞 𝑓𝑜𝑟 𝑞 𝑖𝑠 𝑜𝑑𝑑 𝑃𝐼𝑉 𝑉𝑑𝑜 = 𝜋 𝑆𝑞𝑠𝑖𝑛( 𝜋 2𝑞 ) Kongunadunadu College of Engineering and Technology Department of EEE Choice of converter configuration
- 7. S.No. q r S PIV/Vdo 1 2 1 3 1.047 2 2 3 1 3.142 3 3 1 2 1.047 4 3 2 1 2.094 5 6 1 1 2.094 Kongunadunadu College of Engineering and Technology Department of EEE Choice of converter configuration
- 8. 7. Transformer rating The current rating of a valve is given by 𝐼𝑣 = 𝐼 𝑑 𝑟 𝑞 𝑆𝑡𝑣 = 𝑃 𝐸 𝑚 2 𝐼𝑣 𝑆𝑡𝑣 = 𝑃 𝑉𝑑𝑜 𝜋 2𝑆𝑞𝑠𝑖𝑛 𝜋 𝑞 ∗ 𝐼 𝑑 𝑟 𝑞 P =6, S=2, q=3, r=1 to find transformer utilization factor 𝑆𝑡𝑣 𝑉𝑑𝑜 𝐼 𝑑 = 𝑃𝜋 2𝑆𝑞𝑠𝑖𝑛 𝜋 𝑞 𝑟 𝑞 𝑆𝑡𝑣 𝑉𝑑𝑜 𝐼 𝑑 = 6𝜋 2 ∗ 2 ∗ 3 ∗ 𝑠𝑖𝑛 𝜋 3 ∗ 1 ∗ 3 Kongunadunadu College of Engineering and Technology Department of EEE Choice of converter configuration
- 9. = 6𝜋 2 ∗ 6 ∗ 1 ∗ 3 ∗ sin 𝜋 3 = 𝜋 2.449 ∗ 0.866 𝑆𝑡𝑣 𝑉𝑑𝑜 𝐼 𝑑 = 1.480 Choice of converter configuration
- 10. Analysis of a 12 pulse converters • Two transformers with primary windings connected in star and connected to the common supply voltage. • The current supplied by the supply are sum of the currents flowing in the two primary. • Let the phase voltages of the 12 pulse converter are star connected of the transformer phase voltage as, Kongunadunadu College of Engineering and Technology Department of EEE Analysis of 12 pulse converters
- 11. Kongunadunadu College of Engineering and Technology Department of EEE Analysis of 12 pulse converters
- 12. In delta connected transformer whose ratio is 1: 3 where line voltage is equal to phase voltage. Kongunadunadu College of Engineering and Technology Department of EEE Analysis of 12 pulse converters
- 13. • Comparing the above equations we note that the voltages applied to the bridges has difference of 30 degree to the voltage applied to bridge 1. • Thus the valve 3 is second bridge will be fired 30 degree after the valve 3 in bridge 1 is fired. • Thus 12 pulse converter has 12 pulse of output with each duration of 30 degree. Then the transformers are connected on star-star and star-delta in bridge 1, bridge 2 respectively, to obtain the output of 12 intervals Kongunadunadu College of Engineering and Technology Department of EEE Analysis of 12 pulse converters
- 14. Kongunadunadu College of Engineering and Technology Department of EEE Analysis of 12 pulse converters
- 15. Reference: • Padiyar, K. R., “HVDC power transmission system”, New Age International (P) Ltd., New Delhi, Second Edition, 2010. Analysis of 12 pulse converters Kongunadunadu College of Engineering and Technology Department of EEE