Power transmission system between AC network and reversible hydraulic turbine

Abstract

The present invention relates to a power transmission system (1), comprising a first branch (4) with a controlled switch (41) and a second branch (8) with a variable frequency converter (5) connected in parallel between an AC network (2) and a reversible pump-turbine (3), the variable frequency converter (5) comprising a first AC / DC converter (11) with a first DC interface and a second AC / DC converter (12) with a second DC interface, the first DC interface and the second DC interface being DC link. the second AC / DC converter (12) connected to the first branch (41) by a DC link (13); a control circuit (7) having a first mode and a second mode, in which in the first mode the switches (4) are simultaneously opened to transmit power until the frequencies of the two AC interfaces (61, 62) are the same, and in the second mode the control circuit (7) closes the switches (4) of the first branch (41); an energy storage system (14); and a switching system (15) for selectively connecting the energy storage system (14) to the DC link (13).

Description

Technical Field

[0001] The present invention relates to the transmission of electric power between an AC network and a reversible hydraulic turbine. In particular, the present invention relates to the use of a system that enables the startup of a reversible hydraulic turbine in pump mode.

[0002] Many hydroelectric dams include a reversible pump turbine that can be used either in pump mode to pump water into the dam or in turbine mode to generate electric power that is sent to the AC network. Known power transmission systems include a first branch and a second branch connected in parallel, forming a power link between the AC network and the reversible pump turbine. The first branch includes a control switch. When the control switch is closed, nominal power is exchanged between the AC network and the pump turbine, reducing the electrical losses of the power link. To start the pump turbine in pump mode, the first speed of this pump turbine must initially be zero and be accelerated until it reaches the synchronous speed of the AC network. Therefore, the second branch includes a variable frequency converter with a first AC / DC converter and a second AC / DC converter. The AC interfaces of these AC / DC converters are connected to the AC network and the pump turbine, respectively. The control switch is initially open. The variable frequency converter sends power to the pump turbine until it reaches the synchronous speed of the AC network. When this synchronous speed is reached, the control switch is closed.

[0003] Furthermore, this power transmission system may include a hybridization system with an AC / DC converter connected to a power link, and an energy storage system connected to the DC interface of the AC / DC converter. This energy storage system is a reversible DC power source that can store electrical energy from the AC network and feed that energy back to the AC network via the AC / DC converter. This hybridization system enhances the flexibility of the power transmission system by, for example, storing energy generated by a pump turbine when the AC network temporarily requires less power. Such a hybridization system is excellent at dynamically adapting to power demands. [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] However, the use of hybridization systems is costly, limiting their commercial development. The present invention aims to solve one or more of these problems. Accordingly, the present invention relates to a power transmission system as defined in Appendix Claim 1. [Means for solving the problem]

[0005] Furthermore, the present invention relates to modifications emphasized in the dependent claims. Those skilled in the art will understand that each feature of the specification or dependent claims can be combined independently with the features of the independent claims without intermediate generalization.

[0006] Furthermore, the present invention relates to a method for managing a power transmission system, as emphasized in the appended claims.

[0007] Furthermore, the present invention relates to a hydraulic system, and the system is A power transmission system as highlighted in the attached claims, An AC network connected to the first connection interface of the power transmission system, Includes a reversible pump turbine connected to a second connection interface of the power transmission system. [Brief explanation of the drawing]

[0008] Other features and advantages of the present invention will become clearer from the following description, with reference to the accompanying drawings below, as a guide, and in a completely non-limiting manner. [Figure 1] This is a schematic diagram of a power transmission system according to the first embodiment of the present invention. [Figure 2] This is a schematic diagram of a power transmission system according to a second embodiment of the present invention. [Figure 3] This shows one operating mode of the power transmission system according to the first embodiment in the operating modes of a reversible pump turbine. [Figure 4] This shows another operating mode of the power transmission system according to the first embodiment, in which power supplied by a reversible pump turbine bypasses the main switch. [Figure 5] This shows another operating mode of the power transmission system according to the first embodiment, in which the energy storage system restores energy to both the AC network and the reversible pump turbine in a different operating mode. [Figure 6] This illustrates another operating mode of the power transmission system according to the first embodiment, in which both the reversible pump turbine and the energy storage system transmit power to the AC network. [Figure 7] This is a schematic diagram of a power transmission system according to an independent aspect of the present invention. [Figure 8] This is a schematic diagram of a power transmission system according to a third embodiment of the present invention. [Figure 9] [Figure 10] [Figure 11] The following shows different operating modes of the power transmission system according to the third embodiment. [Figure 12] Figure 8 is a schematic diagram showing an example of an improved power transmission system. [Figure 13] The structure of a DC / DC converter usable in an energy storage device incorporated in the third embodiment is shown. [Figure 14] Another DC / DC converter that can be used in the energy storage device of the third embodiment is shown. [Figure 15] Another DC / DC converter that can be used in the energy storage device of the third embodiment is shown. [Figure 16] Figure 12 is a schematic diagram showing an example of an improved power transmission system. [Figure 17] This is a schematic diagram of a power transmission system according to a fourth embodiment of the present invention. [Figure 18] This is a schematic diagram of a power transmission system according to a fourth embodiment of the present invention. [Modes for carrying out the invention]

[0009] Figure 1 is a schematic diagram of a power transmission system 1 according to a first embodiment of the present invention. The power transmission system 1 includes a control switch 41, a variable frequency converter 5, a connection interface 61, and another connection interface 62. The power link includes a first power branch 4 and a second power branch 8. Power branches 4 and 8 are connected in parallel between connection interfaces 61 and 62. Branch 4 includes a control switch 41. Switch 41 may be an HVAC circuit breaker. Branch 8 includes a variable frequency converter 5. Connection interface 61 is connected to an AC network 2, typically a three-phase AC network. Connection interface 62 is typically connected to a pump turbine 3, which includes a synchronous motor / generator. The pump turbine 3 typically includes a hydraulic unit having a hydraulic wheel connected by a shaft to the rotor of a generator.

[0010] The variable frequency converter 5 includes an AC / DC converter 11, a DC link 13, a control switch 15, an energy storage system (generally represented by the initials ESS) 14, and another AC / DC converter 12.

[0011] The AC interface of the AC / DC converter 11 is connected to the connection interface 61, and the AC interface of the AC / DC converter 12 is connected to the connection interface 62. The AC / DC converters 11 and 12 are such that the current is reversible. The DC link 13 electrically connects the respective DC interfaces of the AC / DC converters 11 and 12 and enables power transmission between these DC interfaces.

[0012] The power transmission system 1 includes a control circuit 7 configured to control the switches 41 and 15 of the variable frequency converter 5. Thus, the control circuit 7 controls the power transmission via the first branch 4, the power transmission from the energy storage system 14, and the power transmission to the energy storage system 14. By means of the main switch 41, the AC interfaces 61 and 62 of the AC / DC converters 11 and 12, in other words, the motor of the pump turbine 3 and the power supply interface of the AC network 2, can be selectively connected / disconnected.

[0013] In particular, the control circuit 7 has a control mode in which the control circuit 7 simultaneously opens the switch 41 of the first branch 4 and sends power from the connection interface 61 to the connection interface 62 via the second branch 8 while increasing the frequency of the connection interface 62 until the frequency reaches that of the interface 61. The control circuit 7 also has another control mode in which the control circuit 7 closes the switch 41 of the first branch 4 and enables power transmission between the AC network 2 and the pump turbine 3.

[0014] The present invention makes it possible to integrate the energy storage system 14 at a low cost and obtain the benefits of efficient energy transmission using a power link. In fact, the energy storage system 14 connected to the DC link 13 shares the AC / DC converters 11 and 12 with the variable frequency converter 5 instead of having a dedicated AC / DC converter connected to the power link. Thereby, the variable frequency converter 5 can be used to transmit power to the power link even outside the pump startup time. Thereby, the power transmission system 1 can provide improved functionality without significantly increasing its cost.

[0015] The present invention is particularly advantageous for the startup variable frequency converter 5 since the AC / DC converters 11 and 12 typically have a nominal power of less than 20% of the nominal power of the switch 41, preferably less than 15% of this nominal power, and more preferably less than 10% of this nominal power. Thereby, such a variable frequency converter 5 can maintain its cost performance and maintain its miniaturization. The nominal power of the switch 41 is typically determined based on the current rating of this switch.

[0016] The DC link 13 may include a filtering circuit. The filtering circuit may include a small capacitor (not shown) which can store energy and contribute to stabilizing the voltage of the DC link 13. A control switch 15 selectively connects the energy storage system 14 and the DC link 13. The variable frequency converter 5 also includes a control circuit 16 and a control circuit 17 (which may be implemented as a global controller). Control circuit 16 is configured to control the AC / DC converter 11, in particular if the AC / DC converter 11 includes active components such as thyristors belonging to the rectifier. Control circuit 17 is configured to control the AC / DC converter 12. Control circuits 16 and 17 may be used to control the flow of power between the energy storage system 14, the AC network 2, and the reversible pump turbine 3. Control circuits 7, 16, and 17 may be based on circuits including intelligent components (microcontrollers, DSPs, ASICs, etc.). These control circuits can acquire information on the production mode of the hydraulic unit and associated states such as the hydraulic head, output power, or guide vane opening. These control circuits can utilize digital models of hydraulic units.

[0017] The energy storage system 14 of this embodiment may include energy storage devices selected from the group including supercapacitors, fuel cells, electrochemical batteries, electric motors that drive a flywheel, air compressors, and electromagnetic storage. The AC / DC converters 11 and 12 may include rectifiers that convert AC voltage to DC voltage in a three-phase network.

[0018] AC / DC converters 11 and 12 are configured to be reversible. Converters 11 and 12 are power inverters (VSIs). In one mode of control circuit 16, power is sent from the AC interface of AC / DC converter 11 to the DC interface of AC / DC converter 11, and in another mode of control circuit 16, power is sent from the DC interface of AC / DC converter 11 to the AC interface of AC / DC converter 11. In one mode of control circuit 17, power is sent from the DC interface of AC / DC converter 12 to the AC interface of AC / DC converter 12, and in another mode of control circuit 17, power is sent from the AC interface of AC / DC converter 12 to the DC interface of AC / DC converter 12.

[0019] Figure 2 is a schematic diagram of a power transmission system 1 according to a second embodiment of the present invention. This embodiment differs from the embodiment of Figure 1 only in the structure of the energy storage system 14. In this embodiment, converters 11 and 12 may be power inverters. The energy storage system 14 includes a DC / DC converter 141 and an energy storage device 142 used as an electrical converter to another form of energy. The DC / DC converter 141 electrically connects the storage device 142 and a control switch 15. The DC / DC converter 141 is configured to adjust the voltage level between the storage device 142 and the DC link 13. The energy storage system 14 includes a control circuit 143 configured to control the DC / DC converter 141. The control circuit 143 controls switches belonging to the DC / DC converter 141. The control circuit 143 can receive information about the DC link 13, such as current and voltage. The control circuit 143 can also receive information about the storage device 142, such as the output voltage and charge state of the storage device. The energy storage device 142 in this embodiment can be selected from a group including a supercapacitor, a fuel cell, an electrochemical battery, an electric motor that drives a flywheel, an air compressor, and an electromagnetic storage device.

[0020] Controllers 16 and 17 can advantageously receive information related to the status of the hydraulic unit and the energy storage system 14, such as the production mode, the charge and health status of the energy storage system 14, the water level (water head) of the container, or the opening of the wicket gate of the hydraulic unit. They can also receive information such as current and voltage related to the DC link 13. Controllers 16 and 17 can advantageously send and receive information to and from each other. These can be based on model predictive control means.

[0021] In the example in Figure 2, converters 11 and 12 may also be current source inverters (CSIs). The voltage of the DC link 13 may be reversible. The DC / DC converter 141 is reversible. It is advantageous for the DC / DC converter (141) to be a two-quadrant converter.

[0022] The DC link 13 may include two windings: a first winding located between the converter 11 and the switch 15, and a second winding located between the converter 12 and the switch 15.

[0023] Figure 3 shows one operating mode of the reversible pump turbine 3 in pump mode of the power transmission system 1 according to the first embodiment. In this operating mode, the control circuit 7 simultaneously opens the switch 41 of the first branch 4, increasing the frequency of the AC interface 62, and sends power from the AC interface 61 to the AC interface 62 until the frequency reaches the frequency of interface 61. In addition, the control circuit 7 opens the switch 15 of the second branch 8, so the energy storage system 14 is not used during power transmission.

[0024] Figure 4 shows another operating mode of the power transmission system 1 according to the first embodiment. The pump turbine 3 is used in turbine mode to supply power to the AC network 2. Here, the pump turbine 3 is driven at a rotational speed different from the frequency of the AC network 2. In this operating mode, if the frequencies of the AC interface 62 and the AC interface 61 are different, the control circuit 7 simultaneously opens the switch 41 of the first branch 4, transmitting the power generated by the reversible pump turbine 3 from the AC interface 62 to the AC interface 61. In addition, the control circuit 7 opens the switch 15 of the second branch 8, so that the energy storage system 14 is not used during power transmission.

[0025] Figure 5 shows another operating mode of the power transmission system 1 according to the first embodiment. In this operating mode, the control circuit 7 simultaneously opens switch 41 of the first branch 4 and closes switch 15 of the second branch 8. The control circuit 7 transmits power from the energy storage system 14 to the AC network 2 via converter 11, temporarily supplying power to the AC network 2. The control circuit 7 also sends power from the energy storage system 14 to the pump turbine 3 at a variable (increasing in this case) frequency. When the frequencies of the AC interfaces 61 and 62 become equal, the control circuit 7 can close switch 41, optimizing the power transmission between the AC network 2 and the pump turbine 3.

[0026] Furthermore, in order to shorten the operating mode time, the control circuit 7 can increase the frequency while transmitting power from the AC network 2 to the pump turbine 3 via converters 11 and 12, and transmit power from the energy storage system 14 to the pump turbine 3 via converter 12, thereby starting the pump turbine 3 in pump mode.

[0027] Figure 6 shows another operating mode of the power transmission system 1 according to the first embodiment. In this operating mode, the control circuit 7 simultaneously closes the switch 41 of the first branch 4 and the switch 15 of the second branch 8. The energy storage system 14 sends power to the AC network 2 via the AC interface 61. The energy storage system 14 can also transmit power to the AC network 2 via the AC interface 62. The reversible pump turbine 3 sends power to the AC network 2 via the switch 41 of the first branch 4. This allows the energy storage system 14 to temporarily supply power to the AC network 2 in addition to the power generated by the pump turbine 3, and to respond to temporary increases in power production in the AC network 2. Compared to the pump turbine 3, the energy storage system 14 enables more dynamic power adjustment in the AC network 2.

[0028] If the power consumption of the AC network 2 temporarily decreases, the power flow can be reversed in this operating mode, where both switches 41 and 15 are closed. The energy storage system 14 receives power from the pump turbine 3 via the AC interface 62. The energy storage system 14 can also receive power from the pump turbine 3 via the AC interface 61. The reversible pump turbine 3 also sends power to the AC network 2 via the switch 41 of the first branch 4.

[0029] In one embodiment, the energy storage system 14 has a maximum power between the maximum power of converter 11 or converter 12 and the combined power of converters 11 and 12. The power transmission from the energy storage system 14 to the network 2 is higher than the power transmission enabled by converter 11 or converter 12. This configuration allows the power transmission system 1 to use a more powerful energy storage system 14 than would be possible using only a single AC / DC converter connected between the connection interface 61 or 62 and the energy storage system 14.

[0030] Figure 7 is a schematic diagram of a power transmission system 1 according to another aspect of the present invention. The power transmission system 1 includes a control switch 41, a variable frequency converter 5, a connection interface 61, and another connection interface 62. The power link includes a first power branch 4 and a second power branch 8. Power branches 4 and 8 are connected in parallel between connection interfaces 61 and 62. Branch 4 includes a control switch 41. Switch 41 may be an HVAC circuit breaker. Branch 8 includes a variable frequency converter 5. Connection interface 61 is connected here to an AC network 2 (typically a three-phase AC network). Connection interface 62 is typically connected to a pump turbine 3 including a synchronous motor / generator.

[0031] The variable frequency converter 5 includes an AC / DC converter 11, a DC link 13, and another AC / DC converter 12. The AC interface of AC / DC converter 11 is connected to connection interface 61 via transformer 81. The AC interface of AC / DC converter 12 is connected to connection interface 62 via transformer 82. Transformers 81 and 82 are configured to adapt the voltages of connection interfaces 61 and 62 to the AC interfaces of converters 11 and 12. For example, transformers 81 and 82 can perform voltage conversion from 15kV to 3kV.

[0032] The power transmission system 1 comprises an energy storage system 14 and an AC / DC converter 18. The energy storage system 14 is connected to the DC interface of the converter 18. The AC interface of the converter 18 is connected between the transformer 81 and the converter 11. The AC interface of the converter 18 is also connected between the transformer 82 and the converter 12. In this embodiment, a control switch selectively connects the converter 18 and the energy storage system 14.

[0033] The control circuit 7 can control the transmission of power between the energy storage system 14 and the connection interfaces 61 and 62. The control circuit 7 can also control the switching of the switch 41.

[0034] Therefore, the control circuit 7 controls the transmission of power via the first branch 4 and the transmission of power to and from the energy storage system 14. The main switch 41 can selectively connect / disconnect the AC interfaces 61 and 62 of the AC / DC converters 11 and 12, in other words, it can selectively connect / disconnect the motor of the pump turbine 3 and the power interface of the AC network 2.

[0035] In particular, the control circuit 7 has a control mode in which it simultaneously opens the switch 41 of the first branch 4 and increases the frequency of the AC interface 62, sending power from the AC interface 61 to the AC interface 62 via the second branch 8 until the frequency of the AC interface 62 reaches the frequency of the AC interface 61. The control circuit 7 also has another control mode in which it closes the switch 41 of the first branch 4, enabling the transmission of power between the AC network 2 and the pump turbine 3.

[0036] This configuration also allows the power transmission system 1 to reduce the cost of the energy storage system 14. In fact, the cost is reduced if the converter 18 is connected to a voltage lower than that of the connection interfaces 61 and 62.

[0037] The energy storage system 14 of this embodiment may include energy storage devices selected from the group consisting of a supercapacitor, a fuel cell, an electrochemical battery, an electric motor that drives a flywheel, an air compressor, and electromagnetic storage. The AC / DC converters 11 and 12 may include rectifiers that convert the AC voltage of the three-phase network to the DC voltage.

[0038] Here, the AC / DC converters 11 and 12 have reversible current. The DC link 13 electrically connects the respective DC interfaces of the AC / DC converters 11 and 12, enabling the transmission of power between these DC interfaces.

[0039] The AC / DC converters 11 and 12 are reversible in their current. The DC link 13 electrically connects the respective DC interfaces of the AC / DC converters 11 and 12, enabling the transmission of power between these DC interfaces.

[0040] In the embodiments shown in Figures 8 to 12, converters 11 and 12 are power inverters (CSIs). In these embodiments, the current in converters 11 and 12 is unidirectional, but the voltage is bidirectional. Converters 11 and 12 may be two-quadrant converters. In these embodiments, the DC link 13 includes two DC conductors 131 and 132. Conductor 131 is connected between one port or pole of the DC interface of converter 11 and one port or pole of the DC interface of converter 12. Conductor 132 is connected between another port or pole of the DC interface of converter 11 and another port or pole of the DC interface of converter 12.

[0041] The energy storage system 14 is connected in series with the conductor 132. The control switch 15 selectively connects the energy storage system 14 to the conductor 132. The switch 15 is controlled by the control circuit 7.

[0042] The energy storage system 14 includes a DC / DC converter 141 and an energy storage device 142 used as an electrical converter to another form of energy. The DC / DC converter 141 electrically connects the storage device 142 and the conductor 132. The DC / DC converter 141 is configured to regulate the voltage level between the storage device 142 and the conductor 132. The energy storage system 14 includes a control circuit 1400 configured to control the DC / DC converter 141. The control circuit 1400 and the storage device 142 can be similar to those described in the example with reference to Figure 2.

[0043] Additionally, one inductor 133 is connected in series with the conductor 131.

[0044] In this structure, in the embodiments shown in Figures 8 to 15, the current in the DC link 13 is unidirectional, while the voltage is bidirectional. Figures 9 to 11 show different operating modes of the embodiment shown in Figure 8, highlighting the advantages of this embodiment. The arrows associated with the links to connection interfaces 61 and 62 indicate the power flow between converters 11 and 12 and connection interfaces 61 and 62, respectively.

[0045] In the first operating mode shown in Figure 9, the energy storage device 14 and converters 11 and 12 operate such that current flows from converter 11 to converter 12 in the bus 131, maintaining the same voltage at the DC interfaces of converters 11 and 12. The voltage at conductor 131 is higher than the voltage at conductor 132. As a result, power is supplied from connection interface 61 by converter 11 and sent to connection interface 62 by converter 12.

[0046] In the second operating mode shown in Figure 10, the energy storage device 14 and converters 11 and 12 operate such that current flows from converter 11 to converter 12 in conductor 131, maintaining the same voltage at the DC interfaces of converters 11 and 12. The voltage at conductor 132 is higher than the voltage at conductor 131. As a result, power is supplied from connection interface 62 by converter 12 and sent to connection interface 61 by converter 11.

[0047] In the third operating mode shown in Figure 11, the energy storage device 14 and converters 11 and 12 operate so that current flows from converter 11 to converter 12 in the conductor 131, and opposite voltages are maintained at the DC interfaces of converters 11 and 12. As a result, power is sent to the connection interface 62 by converter 12 and to the connection interface 61 by converter 11.

[0048] By combining this design with the direct connection of the energy storage system 14 between the respective DC ports of converters 11 and 12, if converters 11 and 12 are power inverters, the corresponding power transmission system 1 can maintain the same structure as converters 11 and 12, avoiding increased costs, while also providing an independent power flow from the energy storage system 14 using AC interfaces 61 and 62.

[0049] In the above example, where the power inverter is a combination of converters 11 and 12 connected in series with an energy storage system 14, the switch 15 is highlighted as an independent component. However, the switch 15 can be integrated into the energy storage system 14, particularly its DC / DC converter 141. The switch 15 may be a switching transistor or a controlled mechanical circuit breaker.

[0050] Figure 12 shows an improved version of the embodiment shown in Figure 8. This improved embodiment has the same features as the embodiment in Figure 8, except for the structure of the energy storage device 14. In the third operating mode described with reference to Figure 11, the voltage applied to the energy storage device is twice the nominal voltage U applied between the ports of converters 11 and 12. To withstand this voltage increase while maintaining a feasible solution and reasonable price for the energy storage device 14, the energy storage device 14 is divided into several modules. Each module comprises its own DC / DC converter 141 and its own storage device 142. The DC / DC converters are connected in series with the conductor 132.

[0051] Figure 13 shows a first possible structure of a DC / DC converter 141 that can be used in an energy storage device 14 incorporated in a third embodiment. This DC / DC converter 141 comprises an H-bridge connected to multiple poles of the storage device 142. Two poles of the H-bridge are connected in series to 143 and 144. The H-bridge comprises transistors (IGBTs in this example) 145 and 145 and diodes 147 and 148 of known structure.

[0052] Figure 14 shows a second possible structure of a DC / DC converter 141 that can be used in an energy storage device 14 incorporated in a third embodiment. In addition to the H-bridge highlighted in Figure 13, the converter 141 further comprises a capacitor 140 and an inductor 149. A branch includes a storage device 142 and an inductor 149 connected in series. This branch is connected in parallel with the branch including the capacitor 140 and smooths the modulated current flowing to the storage device 142 by switching action.

[0053] Figure 15 shows another structure of the DC / DC converter 141 that can be used in the energy storage device 14 incorporated in the third embodiment. To isolate the storage device 142, the DC / DC converter 141 includes a transformer 1412 interconnected between one DC / AC converter 1411 and another DC / AC converter 1413.

[0054] Figure 16 shows an improved version of the embodiment shown in Figure 12. This improved version has the same features as the embodiment in Figure 8, except for the structure of the energy storage device 14. Furthermore, the conductor 132 includes a bypass branch including a switch 151. This branch allows bypassing the energy storage device 14 when it is not in use. Additionally, the switch 15 can disconnect the energy storage device 14, allowing for maintenance or upgrade operations, for example. Furthermore, each energy storage module is equipped with a bypass switch 152. Such a bypass switch 152 can be closed when the corresponding energy storage device 142 or its DC / DC converter fails.

[0055] Figure 17 shows an energy storage device 14 connected between conductors 131 and 132 of the DC link 13 via a switch 15. This energy storage device 14 is connected in parallel to the smoothing capacitor 19.

[0056] Figure 18 shows an energy storage device 14 that can be selectively connected in series to conductor 132. This energy storage device 14 is connected by an H-bridge switching structure 150. The switching structure 150 comprises switches 1501, 1502, 1503, and 1504. One node of the switching structure 150 can be selectively grounded by switch 1505. The H-bridge switching structure 150 is connected to multiple poles of the energy storage device 14. Two poles of the H-bridge are connected to the series connection of conductor 132.

[0057] Furthermore, the conductor 132 includes a bypass branch containing a switch 151. This branch allows the energy storage device 14 to be bypassed when it is not in use. When switches 1501 and 1504 are closed, the energy storage device 14 discharges. When switches 1502 and 1503 are closed, the energy storage device 14 charges. When switches 1501 and 1503 are closed, the energy storage device 14 is bypassed.

[0058] The present invention has described a power transmission system 1 including a reversible pump turbine 3. In another aspect of the present invention, the pump turbine 3 described above can be replaced in combination with other components with another type of turbine, such as a gas turbine or a steam turbine, which is connected to the rotor of a generator by a shaft.

Claims

1. A power transmission system (1), The system includes a first connection interface (61) connected to an AC network (2) and a second interface (62) connected to a reversible pump turbine (3), with a first branch (4) and a second branch (8) connected in parallel between them. The first branch (4) is equipped with a control switch (41), The second branch (8) includes a variable frequency converter (5), The variable frequency converter (5) is A first AC / DC converter (11) having a first AC interface and a first DC interface connected to the first connection interface (61), A second AC / DC converter (12) having a second AC interface connected to a second connection interface (62) and a second DC interface, wherein the first DC interface and the second DC interface are connected by a DC link (13) to the second AC / DC converter (12), A control circuit (7) having a first mode and a second mode, wherein in the first mode, the control switch (41) of the first branch (4) is opened simultaneously, and power is transmitted from the first AC interface (61) to the second AC interface (62) while increasing the frequency of the second AC interface (62) until the frequency reaches the frequency of the first AC interface (61), and in the second mode, the control circuit (7) is closed, The power transmission system (1) further includes an energy storage system (14) connected to a DC link (13), The system includes a switching system (15) controlled by a control circuit (7) for selectively connecting an energy storage system (14) to a DC link (13), In the second mode, the control circuit (7) By keeping the control switch (41) in the closed state and closing the switching system (15), power is sent from the energy storage system (14) to the AC network (2), or the energy storage system (14) receives power from the reversible pump turbine (3). Power transmission system (1).

2. The power transmission system (1) according to claim 1, wherein the energy storage system (14) includes a DC power converter (142) and a DC / DC converter (141).

3. The power transmission system (1) according to claim 2, wherein the DC / DC converter (141) is configured to change the voltage level between the DC power converter (142) and the DC link (14).

4. The power transmission system (1) according to claim 2 or 3, wherein the DC power converter (142) is selected from the group including a supercapacitor, a fuel cell, an electrochemical battery, an air compressor, and an electromagnetic storage device.

5. The power transmission system (1) according to any one of claims 1 to 4, wherein the currents of the first AC / DC converter (11) and the second AC / DC converter (12) are reversible.

6. The power transmission system (1) according to claims 2 and 5, wherein the first AC / DC converter and the second AC / DC converter (11, 12) are power inverters, and the DC / DC converter (141) is a two-quadrant DC / DC converter.

7. The power transmission system (1) according to claim 1, wherein the DC link (13) includes a first winding connected to the first DC interface and the switching system (15), and a second winding connected to the second DC interface and the switching system (15).

8. The first AC / DC converter and the second AC / DC converter (11, 12) are power inverters, The DC / DC converter (141) is a two-quadrant DC / DC converter, The DC link (13) includes a first conductor (131) connected between the individual first ports of the first AC / DC converter and the second AC / DC converter (11, 12), and a second conductor (132) connected between the individual second ports of the first AC / DC converter and the second AC / DC converter (11, 12). The power transmission system (1) according to any one of claims 2 to 4, wherein the DC / DC converter (141) is connected in series with the second conductor (132).

9. The power transmission system (1) according to claim 8, comprising an individual two-quadrant DC / DC converter connected in series to the second conductor (132), and a DC electrical converter (142) connected to the individual two-quadrant DC / DC converter (141).

10. The first AC / DC converter and the second AC / DC converter (11, 12) are two power inverters. A power transmission system (1) according to any one of claims 1 to 4, wherein the power of the DC / DC converter (141) is reversible.

11. The power transmission system (1) according to any one of claims 1 to 10, wherein the nominal power of the first AC / DC converter (11) and the second AC / DC converter (12) is less than 20% of the nominal power of the first switch (41).

12. The power transmission system (1) according to any one of claims 1 to 11, wherein the energy storage system (14) is configured to provide a maximum power that is higher than the maximum power of the first AC / DC converter (11), higher than the maximum power of the second AC / DC converter (12), and lower than the sum of the powers of the first AC / DC converter and the second AC / DC converters (11, 12).

13. It is a hydraulic system, A power transmission system (1) according to any one of claims 1 to 12, The AC network (2) connected to the first connection interface (61) of the power transmission system (1), A reversible pump turbine (3) connected to the second connection interface (62) of the power transmission system (1) and Equipped with a hydraulic system.

14. A method for managing a power transmission system (1), The power transmission system includes a first connection interface (61) connected to an AC network (2) and a second interface (62) connected to a reversible pump turbine (3), with a first branch (4) and a second branch (8) connected in parallel between them. The first branch (4) is equipped with a control switch (41), The second branch (8) includes a variable frequency converter (5), The variable frequency converter (5) is A first AC / DC converter (11) having a first AC interface and a first DC interface connected to the first connection interface (61), The system includes a second AC / DC converter (12) having a second AC interface connected to a second connection interface (62) and a second DC interface, The first DC interface and the second DC interface are connected by a DC link (13). The aforementioned power transmission system (1) further, An energy storage system (14) connected to the DC link (13), The system includes a switching system (15) which is controlled to selectively connect the energy storage system (14) to the DC link (13), The aforementioned method, In the first mode, the control switch (41) of the first branch (4) is opened simultaneously, and power is transmitted from the first AC interface (61) to the second AC interface (62) while increasing the frequency of the second AC interface (62) until the frequency of the second AC interface (62) reaches the frequency of the first interface (61). In the second mode, the control switch (41) of the first branch (4) is closed, the energy storage system (14) is connected to the DC link (13), and power is sent to the AC network (2) or power is received from the reversible pump turbine (3). A method for managing a power transmission system (1).

15. A method for managing the power transmission system (1) according to claim 14, wherein the power transmission system (1) operates to provide a maximum power that is higher than the maximum power of the first AC / DC converter (11), higher than the maximum power of the second AC / DC converter (12), and lower than the sum of the powers of the first AC / DC converter and the second AC / DC converters (11, 12).

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