SE1000811A1 - A converter cell with limited current in case of a short-circuit - Google Patents
A converter cell with limited current in case of a short-circuitInfo
- Publication number
- SE1000811A1 SE1000811A1 SE1000811A SE1000811A SE1000811A1 SE 1000811 A1 SE1000811 A1 SE 1000811A1 SE 1000811 A SE1000811 A SE 1000811A SE 1000811 A SE1000811 A SE 1000811A SE 1000811 A1 SE1000811 A1 SE 1000811A1
- Authority
- SE
- Sweden
- Prior art keywords
- cell module
- capacitor
- short
- capacitor unit
- cell
- Prior art date
Links
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
- 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
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
- H02H9/02—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess current
Abstract
En cellmodul för en modulär multinivåströmriktare presenteras. Cellmodulen innehåller en första kondensatorenhet i parallell med en andra kondensatorenhet och där den första kondensatorenheten innehåller en kommuteringskondensator med förhållandevis låg kapacitans och där den andra kondensatorenheten innehåller en andra kondensator som utgör huvuddelen av cellmodulens totala kapacitans och är kopplad i serie med en strömbegränsningsenhet.(Fig. 3.)A cell module for a modular multi-level inverter is presented. The cell module contains a first capacitor unit in parallel with a second capacitor unit and where the first capacitor unit contains a commutation capacitor with relatively low capacitance and where the second capacitor unit contains a second capacitor which forms the main part of the cell module total capacitance and is connected in series with a current limiting unit. 3.)
Description
20 25 30 10637SE 2 2010-07-30 loop inductance of the cell. However, the higher the switching frequency is, the closer to a desired approximation of a fundamental frequency sine wave the output voltage become, and the number of harmonics of the output voltage is kept at a minimum. 20 25 30 10637SE 2 2010-07-30 loop inductance of the cell. However, the higher the switching frequency is, the closer to a desired approximation of a fundamental frequency sine wave the output voltage become, and the number of harmonics of the output voltage is kept at a minimum.
The converter cell conventionally comprises four valves, each valve comprising at least one semiconductor device of turn-off type, e.g. IGBTs. A free-wheeling dlode, also denoted anti-parallel diode, is connected in anti-parallel with each IGBT and conducting in the opposite direction of the IGBT. The valves are connected in an H- bridge arrangement comprising two parallel-connected phase-legs which are connected in parallel with a capacitor unit, also denoted cell capacitor. Each phase- leg comprises two valves connected in series.The converter cell conventionally comprises four valves, each valve comprising at least one semiconductor device of turn-off type, e.g. IGBTs. A free-wheeling dlode, also denoted anti-parallel diode, is connected in anti-parallel with each IGBT and conducting in the opposite direction of the IGBT. The valves are connected in an H-bridge arrangement comprising two parallel-connected phase-legs which are connected in parallel with a capacitor unit, also denoted cell capacitor. Each phase- leg comprises two valves connected in series.
The chain-link converter needs a substantially large DC capacitor in each cell converter due to the fact that the total phase current is led through each cell. The large capacitor and a low loop inductance in order to reduce Iosses in the valves result in a high shorf-circuit current lf one of the two phase-legs becomes short- circuited. The short-circuit current can be in the region of 1000 kA. The high short- circuit current could seriously damage equipment within the failed cell as well as neighbouring cells and its surroundings. One obvious solution to cope with the short- circuit currents would be to construct a chain-link converter dimensioned for said short-circuit current. However such an over-dimensioned chain-link converter would be very expensive as the short-circuit makes great demands upon IGBT modules and bus bars.The chain-link converter needs a substantially large DC capacitor in each cell converter due to the fact that the total phase current is led through each cell. The large capacitor and a low loop inductance in order to reduce Iosses in the valves result in a high shorf-circuit current lf one of the two phase-legs becomes short- circuited. The short-circuit current can be in the region of 1000 kA. The high short-circuit current could seriously damage equipment within the failed cell as well as neighboring cells and its surroundings. One obvious solution to cope with the short-circuit currents would be to construct a chain-link converter dimensioned for said short-circuit current. However such an over-dimensioned chain-link converter would be very expensive as the short-circuit makes great demands upon IGBT modules and bus bars.
Summary of the invention lt is an object of the invention to provide a cell module which limits the current in case of a short-circuit.Summary of the invention lt is an object of the invention to provide a cell module which limits the current in case of a short-circuit.
The object is achieved by the provision of a cell module according to claim 1.The object is achieved by the provision of a cell module according to claim 1.
A cell module for a chain-link converter is provided. The cell module comprises a split cell capacitor, where said split cell capacitor is meant to be an arrangement where a first capacitor unit is connected in parallel with a second capacitor unit, and where the 10 15 20 25 30 1 O637SE 3 2010-07-30 first capacitor unit compríses a commutation capacitor with a comparatively low capacitance and where the second capacitor unit compríses a second capacitor constituting a major part of the total capacitance of the cell module and is connected in series with a current Iimiting device which limits the magnitude of a short-circuit current by increasing its reactance.A cell module for a chain-link converter is provided. The cell module comprises a split cell capacitor, where said split cell capacitor is meant to be an arrangement where a first capacitor unit is connected in parallel with a second capacitor unit, and where the 10 15 20 25 30 1 O637SE 3 2010-07- 30 first capacitor unit comprises a commutation capacitor with a comparatively low capacitance and where the second capacitor unit comprises a second capacitor constituting a major part of the total capacitance of the cell module and is connected in series with a current Iimiting device which limits the magnitude of a short-circuit current by increasing its reactance.
An advantage with the cell module according to the present invention is its ability to limit the magnitude of the short-circuit current in case the cell capacitor becomes short-circuited. As a consequence, the failed cell module, neighbouring cell modules and its surroundings will not be damaged due to the failed cell module. ln accordance with a first embodiment of the invention, the current Iimiting device compríses an inductor. ln accordance with a second embodiment of the invention, the current limiting device compríses a resistor. ln accordance with a third embodiment of the invention, the current Iimiting device compríses a frequency dependent resistor. ln accordance with a forth embodiment of the invention, the first capacitor unit is connected in parallel with a battery. The battery has a rather low short-circuit current and thus, the short-circuit current is limited if a phase-leg becomes short-circuit.An advantage with the cell module according to the present invention is its ability to limit the magnitude of the short-circuit current in case the cell capacitor becomes short-circuited. As a consequence, the failed cell module, neighboring cell modules and its surroundings will not be damaged due to the failed cell module. In accordance with a first embodiment of the invention, the current Iimiting device comprises an inductor. In accordance with a second embodiment of the invention, the current limiting device comprises a resistor. In accordance with a third embodiment of the invention, the current Iimiting device comprises a frequency dependent resistor. In accordance with a forth embodiment of the invention, the first capacitor unit is connected in parallel with a battery. The battery has a rather low short-circuit current and thus, the short-circuit current is limited if a phase-leg becomes short-circuit.
Brief description of the drawings The present invention will be more fully described by way of example with reference to the accompanying drawings in which: Figure 1 illustrates a principle single line diagram of a chain-link converter, as it is known in the art, Figure 2 illustrates a cell module of a chain-link converter, as it is known in the art, Figure 3 illustrates a split cell capacitor with increased inductance of the second capacitor unit in accordance with the invention, 10 15 20 25 30 10637SE 4 2010-07-30 Figure 4 illustrates a split cell capacitor with increased resistance of the second unit in accordance with the invention, Figure 5 illustrates a split cell capacitor with frequency dependent resistance (R2a, R2a) of the second capacitor unit in accordance with the invention, and Figure 6 illustrates a cell capacitor in combination with a battery in accordance with the invention.Brief description of the drawings The present invention will be more fully described by way of example with reference to the accompanying drawings in which: Figure 1 illustrates a principle single line diagram of a chain-link converter, as it is known in the art, Figure 2 illustrates a cell module of a chain-link converter, as it is known in the art, Figure 3 illustrates a split cell capacitor with increased inductance of the second capacitor unit in accordance with the invention, 10 15 20 25 30 10637SE 4 2010- 07-30 Figure 4 illustrates a split cell capacitor with increased resistance of the second unit in accordance with the invention, Figure 5 illustrates a split cell capacitor with frequency dependent resistance (R2a, R2a) of the second capacitor unit in accordance with the invention, and Figure 6 illustrates a cell capacitor in combination with a battery in accordance with the invention.
Detailed description of embodiments of the invention Figure 1 shows a principle single line diagram of a chain-link converter with the phases in a delta-connected arrangement as it is known in the art. The phases can also be connected in a Y-arrangement. The chain-link converter is configured in shunt connection with a three-phase electric power network with tree phases L1, L2 and L3 and comprises a number of links also denoted converter cells or cell modules, connected in series. ln the figure, a phase with only four cell modules in series is shown for the sake of simplicity of the drawing, but the number thereof may be any conceivable and is normally in the order of 10 to 100. The series-connected cell modules provide a desired ac voltage to the electric power network, being the sum of the ac voltages of each cell module.Detailed description of embodiments of the invention Figure 1 shows a principle single line diagram of a chain-link converter with the phases in a delta-connected arrangement as it is known in the art. The phases can also be connected in a Y-arrangement. The chain-link converter is con fi gured in shunt connection with a three-phase electric power network with tree phases L1, L2 and L3 and comprises a number of links also denoted converter cells or cell modules, connected in series. ln the fi gure, a phase with only four cell modules in series is shown for the sake of simplicity of the drawing, but the number thereof may be any conceivable and is normally in the order of 10 to 100. The series-connected cell modules provide a desired ac voltage to the electric power network, being the sum of the ac voltages of each cell module.
Figure 2 shows a cell module, as it is known in the art, comprising four valves V1, V2, V3 and V4 each comprising at least one semiconductor device of turn-off type, such as for instance an insulated gate bipolar transistor (IGBT), and a free-wheeling diode, also denoted anti-parallel diode, connected in parallel therewith and conducting in the opposite direction of the at least one semiconductor device. The valves are connected in an H-bridge arrangement with a cell capacitor. Each cell module delivers a voltage Uac being zero, +Udc or -Udc where Udo represents the voltage over its cell capacitor.Figure 2 shows a cell module, as it is known in the art, comprising four valves V1, V2, V3 and V4 each comprising at least one semiconductor device of turn-off type, such as for instance an insulated gate bipolar transistor (IGBT) , and a free-wheeling diode, also denoted anti-parallel diode, connected in parallel therewith and conducting in the opposite direction of the at least one semiconductor device. The valves are connected in an H-bridge arrangement with a cell capacitor. Each cell module delivers a voltage Uac being zero, + Udc or -Udc where Udo represents the voltage over its cell capacitor.
Consequently, a phase voltage of the chain-link converter equals the sum of each voltage Uac delivered by each of the cell modules.Consequently, a phase voltage of the chain-link converter equals the sum of each voltage Uac delivered by each of the cell modules.
Figure 3 illustrates a first embodiment of the invention where the current limiting device comprises an inductor L2 which limits the magnitude of a short-circuit current by increasing its reactance. Prior to a short-circuit in one of the phase-legs of the cell module the inductance of the inductor L2 is substantially low in order to not influence 10 15 20 25 10637SE 5 2010-07-30 the reactance of the second capacitor unit in a decisive way. However, in case one of the phase-legs is short-circuited the magnitude of the short-circuit current will be limited by an increased reactance. Said reactance is increased as a result of the short-circuit current. One possible way to achieve the increased reactance would be a current limiting device which is adapted to be transforrned into a shape of a coil when current paths of an original shape is broken due to melting caused by the short-circuit current.Figure 3 illustrates a first embodiment of the invention where the current limiting device comprises an inductor L2 which limits the magnitude of a short-circuit current by increasing its reactance. Prior to a short-circuit in one of the phase-legs of the cell module the inductance of the inductor L2 is substantially low in order to not influence 10 15 20 25 10637SE 5 2010-07-30 the reactance of the second capacitor unit in a decisive way. However, in case one of the phase-legs is short-circuited the magnitude of the short-circuit current will be limited by an increased reactance. Said reactance is increased as a result of the short-circuit current. One possible way to achieve the increased reactance would be a current limiting device which is adapted to be transforrned into a shape of a coil when current paths of an original shape is broken due to melting caused by the short-circuit current.
Figure 4 illustrates a second embodiment of the invention where the current limiting device comprises a resistor R2 which limits the magnitude of the short-circuit current by increasing its resistance.Figure 4 illustrates a second embodiment of the invention where the current limiting device comprises a resistor R2 which limits the magnitude of the short-circuit current by increasing its resistance.
As shown in figure 5 the current limiting device could be a frequency dependent resistor. An example of such a frequency dependent resistor is a bus-bar that has a higher resistance for high frequency currents due to a skin effect where the current path is longer for high frequency currents than for low frequency currents. Another solution to obtain a high resistance at high frequencies is to use different materials in the bus-bar. The frequency dependent resistor is in figure 5 represented by the series connection of resistor R2b and inductor L2 in parallel with resistor R2a.As shown in Figure 5 the current limiting device could be a frequency dependent resistor. An example of such a frequency dependent resistor is a bus-bar that has a higher resistance for high frequency currents due to a skin effect where the current path is longer for high frequency currents than for low frequency currents. Another solution to obtain a high resistance at high frequencies is to use different materials in the bus-bar. The frequency dependent resistor is in 5 gure 5 represented by the series connection of resistor R2b and inductor L2 in parallel with resistor R2a.
Another embodiment is shown in figure 6 where the current limiting device comprises a battery. The battery has a comparably low short-circuit current and thus, the short- circuit current is limited. However, since the battery contains high energy, a breaker must be used to disconnect the battery.Another embodiment is shown in Figure 6 where the current limiting device comprises a battery. The battery has a comparably low short-circuit current and thus, the short-circuit current is limited. However, since the battery contains high energy, a breaker must be used to disconnect the battery.
Claims (5)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE1000811A SE1000811A1 (en) | 2010-08-02 | 2010-08-02 | A converter cell with limited current in case of a short-circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE1000811A SE1000811A1 (en) | 2010-08-02 | 2010-08-02 | A converter cell with limited current in case of a short-circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| SE1000811A1 true SE1000811A1 (en) | 2010-08-02 |
Family
ID=42617383
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| SE1000811A SE1000811A1 (en) | 2010-08-02 | 2010-08-02 | A converter cell with limited current in case of a short-circuit |
Country Status (1)
| Country | Link |
|---|---|
| SE (1) | SE1000811A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2014090272A1 (en) * | 2012-12-10 | 2014-06-19 | Siemens Aktiengesellschaft | Submodule for limiting a surge current |
| WO2021174281A1 (en) * | 2020-03-05 | 2021-09-10 | Avl List Gmbh | Converter assembly and test stand having a converter assembly |
-
2010
- 2010-08-02 SE SE1000811A patent/SE1000811A1/en not_active Application Discontinuation
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2014090272A1 (en) * | 2012-12-10 | 2014-06-19 | Siemens Aktiengesellschaft | Submodule for limiting a surge current |
| CN104813578A (en) * | 2012-12-10 | 2015-07-29 | 西门子公司 | Submodule for limiting a surge current |
| WO2021174281A1 (en) * | 2020-03-05 | 2021-09-10 | Avl List Gmbh | Converter assembly and test stand having a converter assembly |
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| Date | Code | Title | Description |
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| NAV | Patent application has lapsed |