High voltage DC/DC converter with cascaded resonant tanks

• US 9,350,250 B2
• Filed: 06/08/2011
• Issued: 05/24/2016
• Est. Priority Date: 06/08/2011
• Status: Active Grant

• Current Assignee: Alstom Technology Ltd. (Alstom SA)
• Original Assignee: Alstom Technology Ltd. (Alstom SA)
• Inventors: Whitehouse, Robert S.
• Primary Examiner(s): Laxton, Gary L
• Application Number:
  US14/124,704
• Publication Number:
  US 20140098575A1
• Time in Patent Office: 1,812 Days
• Field of Search: 363/21.02, 363/21.03, 323/239, 323/242
• US Class Current: 1/1
• CPC Class Codes: H02J 3/36 Arrangements for transfer of electric power between ac networks via a high-tension dc link
• CPC Class Codes: H02M 3/07 using capacitors charged and discharged alternately by semiconductor devices with control electrode , e.g. charge pumps
• CPC Class Codes: H02M 3/33507 with automatic control of the output voltage or current, e.g. flyback converters H02M3/33561, H02M3/33569 take precedence
• CPC Class Codes: H02M 3/3376 with automatic control of output voltage or current
• CPC Class Codes: H02M 3/338 in a self-oscillating arrangement H02M3/337 takes precedence
• CPC Class Codes: H02M 7/103 Containing passive elements (capacitively coupled) which are ordered in cascade on one source
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
• CPC Class Codes: Y02E 60/60 Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]

Abstract

A converter, for use in high voltage direct and alternating current power transmission comprises a primary charge transfer converter. The charge transfer converter includes first and second primary terminals for connection to one or more electrical networks. The primary charge transfer converter also includes a plurality of charge transfer elements and a plurality of primary switching elements which are connected in a cascade circuit between the first and second primary terminals. Each charge transfer element includes at least one resonant circuit. The primary switching elements are operable to selectively cause charging and discharging of each resonant circuit to transfer charge between the charge transfer elements and thereby create a voltage difference between the first and second primary terminals.

Claims

1. A converter for use in high voltage direct and alternating current power transmission, the converter comprising a primary charge transfer converter, including first and second primary terminals for connection to one or more electrical networks, a plurality of charge transfer elements, and a plurality of primary switching elements connected in a single series connected circuit between the first and second primary terminals, each charge transfer element including at least one resonant circuit having a resonant frequency, the plurality of charge transfer elements and the plurality of primary switching elements being connected in a cascade circuit wherein the plurality of charge transfer elements comprise a first set of charge transfer elements connected in series between the first and second primary terminals and a second set of charge transfer elements connected in series, each charge transfer element being connected in parallel with a different set of at least one primary switching element, a primary switching element of each different set of at least one primary switching element being shared in parallel with a charge transfer element of said first set and a charge transfer element of said second set, and wherein the primary switching elements are operable at a frequency equal or approximately equal to the resonant frequency of the resonant circuit to selectively cause charging and discharging of each resonant circuit to transfer charge between the charge transfer elements and thereby create a voltage difference between the first and second primary terminals.

2. The converter according to claim 1, wherein the junction between adjacent primary switching elements defines a secondary terminal.

3. The converter according to claim 1, wherein at least one resonant circuit of each charge transfer element includes at least one inductor connected in series with at least one capacitor.

4. The converter according to claim 1, wherein at least one charge transfer element includes a plurality of parallel-connected resonant circuits.

5. The converter according to claim 1, wherein each primary switching element is or includes a semiconductor device.

6. The converter according to claim 5, wherein each primary switching element further includes an anti-parallel diode connected in parallel with the semiconductor device.

7. The converter according to claim 5, wherein the semiconductor device is an insulated gate bipolar transistor, a gate turn-off thyristor, a field effect transistor, a transistor, an injection enhancement gate transistor, an insulated gate commutated thyristor or an integrated gate commutated thyristor.

8. The converter according to claim 6, wherein the plurality of primary switching elements define a cascade arrangement of alternating odd and even primary switching elements, the primary switching elements being controllable to selectively put each of the odd primary switching elements in a first open/closed state and each of the even primary switching elements in a second open/closed state opposite the first open/closed state.

9. The converter according to claim 8, wherein the plurality of primary switching elements of are controllable to alternate between a closed state and an open state.

10. The converter according to claim 9, wherein each of the primary switching elements is controllable to delay switching between the open state and the closed state.

11. The converter according to claim 10, wherein each of the primary switching elements is controllable to vary the length of the delay in switching between open and closed states.

12. The converter according to claim 1, wherein the resonant circuit of each charge transfer element is tuned to the same resonant frequency.

13. The converter according to claim 1, further including at least one DC link capacitor connected in parallel with the primary charge transfer converter.

14. The converter according to claim 1, further including a primary auxiliary unit connected to the second primary terminal thereof, the primary auxiliary unit defining either a charge store or a charge generator including an auxiliary terminal for connection to an electrical network.

15. The converter according to claim 14, wherein the primary auxiliary unit defines a charge store including at least one reservoir capacitor (44a) to store said charge.

16. The converter according to claim 14, wherein the primary auxiliary unit defines a charge generator including an oscillator circuit to introduce an AC voltage component into the charge transfer elements of the primary charge transfer converter.

17. The converter according to claim 15, wherein the oscillator circuit operates at a frequency that approximates the resonant frequency of the charge transfer elements.

18. A converter assembly comprising the converter according to claim 14, wherein the first primary terminal is connected in use to a positive terminal of a first DC network, wherein the auxiliary terminal of the auxiliary unit is connected in use to a negative terminal of the first DC network, and wherein each junction between adjacent primary switching elements defines a secondary terminal which is connected in use to one of a positive terminal, a negative terminal and a ground terminal of a second DC network.

19. A converter assembly comprising the converter according to claim 14, and a plurality of parallel-connected secondary charge transfer converters each having a first and a second secondary terminal, wherein the first secondary terminal of each secondary charge transfer converter is connected to the auxiliary terminal of the converter and wherein a respective secondary auxiliary unit is connected to the second secondary terminal of each secondary charge transfer.

20. The converter assembly according to claim 19, wherein each secondary auxiliary unit comprises an auxiliary terminal and further including a transformer connected between the auxiliary terminal of each secondary auxiliary unit and a respective phase of a multiphase AC network.

21. The converter assembly according to claim 19, further including a second converter according to claim 14, the auxiliary terminal of the second converter being connected to the auxiliary terminal of each secondary auxiliary unit the first primary terminal of each converter being connected in use to respective positive and negative terminals of a first DC network, and each secondary charge transfer converter including a secondary terminal for connection in use to a respective phase of a multiphase AC network.

22. A converter assembly comprising a plurality of converters according to claim 14, and further including at least one converter limb having first and second limb portions, each limb portion including a said converter, the auxiliary terminal of the auxiliary unit in the converter in the first limb portion being connected in series with the auxiliary terminal of the auxiliary unit in the converter in the second limb portion to connect the converters in a given convert limb with one another end to end the first primary terminal of the converter in the first limb portion being connected in use to a positive terminal of a first DC network, the first primary terminal of the converter in the second limb portion being connected in use to a negative terminal of the first DC network, and the series connection between the auxiliary terminals defining a phase terminal connected in use to an AC network, the auxiliary unit of each limb portion being operable to switch the respective limb portion in and out of circuit so as to generate a voltage waveform at the phase terminal of the respective converter limb.

23. The converter assembly according to claim 22, defining a plurality of converter limbs, each converter limb including a phase terminal for connection to a respective phase of a multiphase AC network.

24. The converter assembly according to claim 19, wherein each auxiliary unit includes a reference terminal which is connected in use to a lower voltage potential than the corresponding auxiliary terminal.