Classifications

• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
  • H02M3/00—Conversion of DC power input into DC power output
  • H02M3/22—Conversion of DC power input into DC power output with intermediate conversion into AC
  • H02M3/24—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters
  • H02M3/28—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC
  • H02M3/325—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC using devices of a triode or a transistor type requiring continuous application of a control signal
  • H02M3/335—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
  • H02M3/33569—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
  • H02M3/00—Conversion of DC power input into DC power output
  • H02M3/22—Conversion of DC power input into DC power output with intermediate conversion into AC
  • H02M3/24—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters
  • H02M3/28—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC
  • H02M3/325—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC using devices of a triode or a transistor type requiring continuous application of a control signal
  • H02M3/335—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
  • H02M3/33569—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
  • H02M3/33576—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements having at least one active switching element at the secondary side of an isolation transformer
  • H02M3/33584—Bidirectional converters
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
  • H02M3/00—Conversion of DC power input into DC power output
  • H02M3/22—Conversion of DC power input into DC power output with intermediate conversion into AC
  • H02M3/24—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters
  • H02M3/28—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC
  • H02M3/325—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC using devices of a triode or a transistor type requiring continuous application of a control signal
  • H02M3/335—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
  • H02M7/00—Conversion of AC power input into DC power output; Conversion of DC power input into AC power output
  • H02M7/42—Conversion of DC power input into AC power output without possibility of reversal
  • H02M7/44—Conversion of DC power input into AC power output without possibility of reversal by static converters
  • H02M7/48—Conversion of DC power input into AC power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
  • H02M7/483—Converters with outputs that each can have more than two voltages levels
  • H02M7/4835—Converters with outputs that each can have more than two voltages levels comprising two or more cells, each including a switchable capacitor, the capacitors having a nominal charge voltage which corresponds to a given fraction of the input voltage, and the capacitors being selectively connected in series to determine the instantaneous output voltage
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
  • H02M1/00—Details of apparatus for conversion
  • H02M1/0095—Hybrid converter topologies, e.g. NPC mixed with flying capacitor, thyristor converter mixed with MMC or charge pump mixed with buck

Definitions

• This invention relates to a DC to DC converter assembly for interconnecting DC electrical networks, and a method of controlling a DC to DC converter assembly for interconnecting DC electrical networks.
• HVDC high voltage direct current
• DC direct current
• a DC to DC converter assembly for interconnecting DC electrical networks, the DC to DC converter assembly comprising:
• each converter including first and second DC terminals for connection to a respective one of the DC electrical networks, each converter including a converter limb extending between the corresponding first and second DC terminals, the converter limb of the first converter having a pair of first limb portions separated by a first AC terminal, the converter limb of the second converter having a pair of second limb portions separated by a second AC terminal, each limb portion including at least one switching element, at least one first limb portion including at least one first module, at least one second limb portion including at least one second module, the or each module including at least one switching element and at least one energy storage device, the or each switching element and the or each energy storage device in each module combining to selectively provide a voltage source, the or each switching element in each limb portion being switchable to switch the corresponding limb portion into or out of circuit between the corresponding AC and DC terminals to control the configuration of an AC voltage at the corresponding AC terminal; an AC transmission link, the first AC terminal being connected to the second AC terminal via the AC transmission link, the
• the DC to DC converter assembly is operable to transfer power between the DC electrical networks. More particularly, to operate the DC to DC converter assembly to transfer power between the DC electrical networks, the switching elements of the limb portions of each converter are switched to selectively switch each limb portion into circuit between the corresponding AC and DC terminals over an operating cycle of the DC electrical networks.
• the formation of the current circulation path allows energy to be transferred between at least one first module and at least one second module, and so permits regulation of the energy stored in a given energy storage device, thereby obviating the problems associated with a deviation of the energy level of at least one energy storage device from the reference value.
• the configuration of the current circulation path may vary depending on the configuration and operation of the DC to DC converter assembly.
• auxiliary limb in each converter provides an additional route through which current can flow in the converter, and so provides greater flexibility in terms of the number of possible configurations of the current circulation path.
• the auxiliary limb of each converter may include an auxiliary terminal, and the auxiliary terminals of the first and second converters are electrically interconnected by a current return path, the current circulation path including the current return path.
• the configuration of each auxiliary limb may vary.
• each auxiliary limb may include a pair of DC link capacitors separated by the corresponding auxiliary terminal.
• the inclusion of the current return path in the current circulation path allows transfer of energy between at least one first module and at least one second module through control of the configuration of the AC voltage at each AC terminal to inject a common mode current into the current return path. Additionally, aside from providing a means of transferring energy from at least one first module to at least one second module, the provision of the current return path is particularly useful when it is required to limit the number of limb portions that are connected in the current circulation path.
• the controller may be configured to selectively control switching of the or each switching element in each limb portion to control the configuration of the AC voltage at the corresponding AC terminal to concurrently form the current circulation path and transfer power between the DC electrical networks. More particularly, the current circulation path may be formed during a common conduction period of an AC transmission link in which at least one first limb portion and at least one second limb portion at both ends of the AC transmission link are both switched into conduction (i.e. switched into circuit between the corresponding AC and DC terminals) to transfer power between the DC electrical networks.
• the converter limb 30 of the second converter 24 has a pair of second limb portions 38a, 38b separated by a second AC terminal 42. More particularly, in the converter limb 30 of the second converter 24, an "upper" second limb portion 38a is connected between the first DC terminal 26 and the second AC terminal 42, and a “lower” second limb portion 38b is connected between the second DC terminal 28 and the second AC terminal 42.
• Each first limb portion 36a, 36b includes a director switch 44 connected in series with a plurality of series-connected first modules 46a.
• Each second limb portion 38a,38b includes a director switch 44 connected in series with a plurality of series-connected second modules 46b.
• Each director switch 44 is in the form of a single switching element. It is envisaged that, in other embodiments of the invention, each director switch may include a plurality of series-connected switching elements.
• the current circulation path 74 is formed during a common conduction period 80 of the AC transmission link 56.
• the common conduction period 80 of the AC transmission link 56 is the period in which the "upper" first and second limb portions 36a,38a are both switched into conduction (i.e. switched into circuit between the corresponding AC and DC terminals 26,28,40,42) to transfer power between the DC electrical networks 32,34.
• the circulation current 76 (as shown in Figure 4d) combines with the voltage 82a,82b across the chain-link converter 54 of each "upper” limb portion 36a,38a during the common conduction period 80 to modify the power 84a, 84b generated in each "upper” limb portion 36a, 38a and, in turn, affect the energy 86a,86b stored in the chain-link converter 54 of each "upper” limb portion 36a, 38a.
• the polarity of the voltage 82a across the chain-link converter 54 of the "upper" first limb portion 36a is opposite to the polarity of the voltage 82b across the chain-link converter 54 of the "upper” second limb portion 38a. Consequently the circulation current 76 flowing through the current circulation path 74 has an opposite effect on each of the powers 84a,84b generated in each of the "upper” limb portions 36a, 38a (as shown in Figure 4d).
• the current circulation path 74 can be formed by the controller 65 controlling switching of the director switch 44 and switching elements in each module 46a,46b of the "lower" first and second limb portions 38 to generate a voltage across each chain-link converter 54 of the "lower” first and second limb portions 38, and thereby generate a differential AC voltage between the first and second AC terminals 40,42.
• a second DC to DC converter assembly 120 according to a second embodiment of the invention is shown in Figure 5.
• the second DC to DC converter assembly 120 of Figure 5 is similar in structure and operation to the first DC to DC converter assembly 20 of Figure 1 , and like features share the same reference numerals.
• the AC voltage 66a,66b,66c,68a,68b,68c at each AC terminal 40,42 of a given converter 22,24 is also phase-shifted by 120 electrical degrees relative to the AC voltage 66a,66b,66c,68a,68b,68c at each other AC terminal 40,42 of the given converter 22,24 during the operation of the DC to DC converter assembly to transfer power between the DC electrical networks 32,34.
• Formation of a current circulation path 74 in the second DC to DC converter assembly 120 in this manner not only provides a means of transferring energy from at least one first module 46a to at least one second module 46b, but also is particularly useful when it is required to limit the number of limb portions 36a, 36b, 38a, 38b that are connected in the current circulation path 74.
• Another way of enabling regulation of the energy level of each energy storage device 48 in each module 46a, 46b of the first and second converters 22,24 of the second DC to DC converter assembly 120 is by forming an alternative current circulation path 90 with a different configuration. To form the alternative current circulation path 90, the controller 65 controls:
• the alternative current circulation path 90 is formed during an overlap 92 between the common conduction periods 80a, 80b of the first and second AC transmission links 56a, 56b, so as to enable concurrent formation of the alternative current circulation path 90 and transfer of power between the DC electrical networks 32,34. Accordingly, as shown in Figure 7, the alternative current circulation path 90 passes through a first current circulation path portion, a second current circulation path portion and the auxiliary limbs 60 of the first and second converters 22,24.
• the first current circulation path portion includes the first AC transmission link 56a, the "upper" first limb portion 36a connected at a first end of the first AC transmission link 56a, and the "upper" second limb portion 38a connected at a second end of the first AC transmission link 56a.
• the polarities of the voltages 94a,94c across the chain-link converters 54 of the first limb portions 36a,36b of the first converter 22 that are connected in the alternative current circulation path 90 are opposite to the polarities of the voltages 94b, 94d across the chain-link converters 54 of the second limb portions 38a,38b of the second converter 24 that are connected in the alternative current circulation path 90.
• the combination of the first and second current circulation path portions in the alternative current circulation path 90 may be replaced by a combination of the second and third current circulation path portions, or a combination of the first and third current circulation path portions.
• the controller 65 is configured to selectively control switching of the director switches 44 and switching elements in each module 46a,46b of each limb portion 36a,36b,38a,38b to control the configuration of the AC voltage at the corresponding AC terminal 40,42 to first form a first current circulation path, the first current circulation path being identical to the aforementioned alternative current circulation path 90, followed by a second current circulation path.
• the second current circulation path passes through a first current circulation path portion, a third current circulation path portion and the auxiliary limbs 60 of the first and second converters 22,24.
• the first current circulation path portion includes the first AC transmission link 56a, the "upper” first limb portion 36a connected at a first end of the first AC transmission link 56a, and the "upper” second limb portion 38a connected at a second end of the first AC transmission link 56a.
• the third current circulation path portion includes the third AC transmission link 56c, the "lower” first limb portion 36b connected at a first end of the third AC transmission link 56c, and the "lower” second limb portion 38b connected at a second end of the third AC transmission link 56c.
• first and second current circulation paths are described above with respect to the first AC transmission link 56a
• the described formation of the first and second current circulation paths applies mutatis mutandis to each of the second and third AC transmission links 56b,56c to extend the period in which energy can be transferred to or from a given energy storage device 48 of the limb portions 36a,36b,38a,38b connected at both ends of each of the second and third AC transmission links 56b, 56c.
• each limb portion may omit the director switch. Omission of the director switch from each limb portion would require the plurality of series-connected modules to provide a voltage to offset the DC voltage at the corresponding DC terminal so as to configure the limb portion in a nonconducting state.

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Dc-Dc Converters (AREA)
• Direct Current Feeding And Distribution (AREA)
• Rectifiers (AREA)
• Electrotherapy Devices (AREA)

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• 2013
  • 2013-07-10 GB GB1312376.5A patent/GB2516068B/en not_active Expired - Fee Related
• 2014
  • 2014-07-08 WO PCT/EP2014/064574 patent/WO2015004120A2/en not_active Ceased
  • 2014-07-08 EP EP14739378.9A patent/EP3020126A2/de not_active Withdrawn

Non-Patent Citations (1)

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