DC / DC conversion device, medium-voltage DC / ac converter system, and method for operating such a medium-voltage DC / ac converter system

Abstract

The present invention relates to a DC / DC conversion device (1) comprising: - a connection input (3) intended to be connected to one or more DC electrical energy sources (5), - a connection output (11) intended to be connected to a central DC collection power line (13), - a first compartment (23) housing a DC / DC converter (15), - a second compartment (25) filled with a dielectric fluid and housing a controllable disconnector (29), the controllable disconnector (29) being arranged in line with the DC / DC converter (15) and downstream thereof, the controllable disconnector (29) being configured to have a closed position in which current is able to pass between the connection input (3) and the connection output (11), and an open position in which current is interrupted between the connection input (3) and the connection output (11).

Description

DC / DC conversion device, medium voltage DC / AC converter system and method for operating such a medium voltage DC / AC converter system

[0001] The field of the present invention relates to current conversion devices, particularly medium-voltage devices. More specifically, the invention relates to a DC / DC conversion device, a medium-voltage DC / AC converter system comprising such a DC / DC conversion device, and a method for operating such a medium-voltage DC / AC converter system.

[0002] In medium voltage networks connecting a large number of modest power converters, for example 250kW for a + / - 10kV network, the implementation of switchgear functions (sectioning, earthing) takes up a non-negligible volume, which may be much larger than that of the converter itself, and there is a challenge in not resorting to standard solutions known for high voltage AC currents.

[0003] The present invention can be deployed more specifically in the field of electricity transport in electrical energy transmission and distribution networks, particularly in medium voltage alternating current and direct current, and more particularly to an electrical energy transmission and / or distribution network.

[0004] In medium-voltage AC distribution networks, it is essential to ensure continuity of service by providing selectivity in protection devices and fault clearing without interruption. This is achieved using medium-voltage AC circuit breakers, typically within a ring network architecture.

[0005] Common solutions on the market are known as "Ring Main Units" (RMUs). Such a main unit has three main functions: - Close the line (to ensure continuity of service) - Disconnect a DC / DC converter from the line (for maintenance or in case of fault, for example)

[0006] However, the size and cost of the solutions on the market are significant, and the equipment requires indoor installation, hence the need for integration into a dedicated building. As a result, the known solutions occupy a volume of over 30m³.

[0007] The present invention aims to make it possible to do without these cumbersome solutions known on the market while ensuring network protection and the functionality of protection selectivity and converters.

[0008] To this end, the present invention aims to provide a DC / DC conversion device comprising: - a connection input intended to be connected to one or more DC electrical power sources, - a connection output intended to be connected to a central DC power collection line, - a first compartment housing a DC / DC converter, - a second compartment filled with a dielectric fluid and housing a controllable disconnector, the controllable disconnector being arranged in line with the DC / DC converter and downstream of it, the controllable disconnector being configured to have a closed position in which current can pass between the connection input and the connection output, and an open position in which current is interrupted between the connection input and the connection output.

[0009] The invention may further include one or more of the following aspects taken alone or in combination: - The controllable disconnector is, for example, a pre-armed disconnector. - The controllable disconnect switch can be configured to be controlled by an actuator. - The controllable disconnect switch is, for example, a rotary load switch. - The dielectric fluid is, in particular, oil. - The first and second compartments can form a single compartment. - The first and second compartments can be distinct and separated by a partition wall. - The first and second compartments are fluidly connected to each other. - The DC / DC conversion device also includes a malfunction detector.

[0010] The invention also relates to a medium voltage DC / AC converter system (100) comprising - at least one DC / AC converter, - a central DC power collection line, the terminal(s) of the central power line being intended to be connected to one or two electrical power distribution networks via said DC / AC converter(s), - at least one DC / DC conversion device as described above, the DC / DC conversion device(s) being connected by their connection outputs in parallel to the central DC power line of collection and upstream of the DC / AC converter(s).

[0011] The DC / AC converter system may also include the following aspects: - The medium voltage DC / AC converter system also includes - at least two DC / AC converters, and - a central unit configured to receive fault signals from DC / DC conversion devices and to shut down said DC / AC converter(s) upon receiving a fault signal from at least one of the DC / DC conversion devices.

[0012] The invention also relates to a method for operating a medium-voltage DC / AC converter system as described above, in which - the controllable disconnect switch of a DC / DC conversion device is activated to isolate it from the central DC power collection line.

[0013] The process may also include one or more of the following aspects, taken alone or in combination: - The DC / AC converter system is switched off - we delay for a predetermined amount of time, - The DC / AC converter system is powered back on. - before activating the controllable disconnect switch, the DC / AC converter system is switched off.

[0014] For better understanding, the invention is described below in more detail using certain embodiments and in association with the accompanying schematic drawings.

[0015] [Fig 1] Figure 1 represents a simplified diagram of an embodiment of a DC / DC conversion device according to the present description,

[0016] [Fig 2] Figure 2 shows a simplified diagram of another embodiment of a DC / DC conversion device according to the present description,

[0017] [Fig 3] Figure 3 shows a simplified diagram of a medium-voltage DC / AC converter system, and

[0018] [Fig 4] Figure 4 is a flowchart showing in a simplified way a process for operating the medium voltage DC / AC converter system of Figure 3.

[0019] In all figures, elements with identical functions bear the same reference numbers.

[0020] The following are examples. Although the description refers to one or more embodiments, this does not necessarily mean that each reference relates to the same embodiment, or that the features apply only to a single embodiment. Simple features from different embodiments can also be combined or interchanged to provide other embodiments.

[0021] By "upstream" or "downstream", we locate the elements in the direction of electrical power from an electrical energy source towards, for example, an energy distribution network.

[0022] The present invention may in particular relate to any low, medium or high voltage installation, alternating current or direct current.

[0023] The present invention finds a particularly interesting application in a medium voltage network for the transport of electrical energy.

[0024] Figure 1 shows a simplified diagram of a DC / DC conversion device 1.

[0025] This conversion device 1 includes a connection input 3 which is intended to be connected to one or more DC electrical power sources 5.

[0026] In the example illustrated in Figure 1, the DC electrical energy sources 5 are, for example, one or more photovoltaic panel arrays 7 which are, for example, connected via MPPT modules 9 (for "Maximum Power Point Tracking") which optimize the efficiency of the photovoltaic systems, to an LVDC power line connected to the input 3 of the conversion device 1. Of course, other electrical energy sources 5 are conceivable, including wind turbines or other renewable electrical energy sources.

[0027] The DC / DC conversion device 1 also includes a connection output 11 which is intended to be connected to a central DC power collection line 13.

[0028] The DC / DC conversion device 1 is a high voltage DC / DC converter whose purpose is to lower the input DC current and thus increase the output DC voltage.

[0029] For this purpose, as shown in Figure 1, the device includes a DC / DC converter 15 as well as a malfunction detector 17 and an associated control and monitoring unit 19.

[0030] To ensure the electrical isolation of the DC / DC converter 15 during operation, the DC / DC conversion device 1 has a tank 21 (shown in dashed lines) which is filled with a dielectric fluid, for example, oil. This fluid also contributes to cooling the converter.

[0031] This tank 21 is for example compartmentalized with a first compartment 23 housing the DC / DC converter 15 and a second compartment 25 separated from the first compartment 23 for example by a separating wall 27 like a partition.

[0032] Naturally, the second compartment 25 is also filled with a dielectric fluid, specifically the same as that in compartment 23. The separating wall 27 may, for example, have openings so that the first 23 and second 25 compartments are fluidically connected. The two compartments 23 and 25 may also be connected via a channel (not shown).

[0033] The DC / DC conversion device also includes a controllable disconnector 29 which is housed in the second compartment 25.

[0034] This controllable disconnector 29 is arranged in line with and downstream of the DC / DC converter 15.

[0035] This controllable disconnector 29 is configured to be able to take a closed position in which current can pass between the connection input 3 and the connection output 11, and an open position in which current is interrupted between the connection input 3 and the connection output 11.

[0036] The controllable disconnector 29 can be a pre-armed disconnector, meaning that in its operating state it is normally closed, but it includes, for example, an elastic element such as a spring that tends to tilt the disconnector towards the open position and a retaining element that prevents this opening. When the opening of the retaining element is commanded, for example by means of an actuator (not shown), the force of the elastic element will tilt the disconnector 29 towards its open position, thus the current is interrupted and the DC / DC converter 1 as well as the upstream power sources 5 are disconnected from the central DC power line 13.

[0037] The controllable disconnector 29 can for example be made in the form of a rotary load switch.

[0038] As shown in Figure 1, the control and monitoring unit 19 is connected via a control line 31 (arrow with a mixed solid and dashed line). Thus, when the control and monitoring unit 19 detects a fault, for example overheating, via the fault detector 17, the unit 19 can control the opening of the controllable disconnector 29, in particular autonomously, so that the DC / DC converter 1 and everything upstream of the converter (in particular the electrical power sources 5) are electrically isolated from the central DC power line 13.

[0039] Figure 2 shows another embodiment in which the first 23 and the second 25 compartments form a single compartment. In other words, the controllable disconnector 29 is housed in the tank 21 without a separating wall 27.

[0040] Figure 3 shows a medium voltage DC / AC converter system 100.

[0041] This system includes at least one DC / AC converter 102, in this case two DC / AC converters 102, as well as the central DC power line 13. As can be seen in Figure 3, the terminal(s) of the central DC power line 13 are connected to one or two electrical power distribution networks 104, 106 via said DC / AC converter(s) 102.

[0042] The medium-voltage DC / AC converter system 100 comprises, in this example, at least four DC / DC conversion devices such as as described above.

[0043] The DC / DC conversion devices 1 are connected by their connection outputs 11 in parallel to the central DC collection power line 13 and upstream of the DC / AC converter(s) 102.

[0044] The medium-voltage DC / AC converter system 100 has more than one central unit 108. This central unit 108 is configured to communicate, for example, with the control and monitoring units 19 and with the protection circuits of the DC / AC converters 102. If necessary, it can also be configured to shut down the said DC / AC converter device(s) 1 upon receiving a signal indicating a malfunction of one of the DC / DC conversion devices. In the figure, the communication links of unit 108 are schematically represented by incoming or outgoing dashed arrows.

[0045] In the case where the medium voltage DC / AC converter system 100 has only one DC / AC converter 102, the presence of a central unit 108 is not essential.

[0046] We will now describe the operation of the medium voltage DC / AC converter system 100 in Figure 3 using a method to make it work.

[0047] For this, we assume that one of the converter devices 1 is faulty. This fault can result from multiple reasons, for example a fault in the electrical energy sources 5 or for example an insulation fault or overheating in one of the converter devices 1.

[0048] According to a preliminary step shown in Figure 4, during a step 200, the control and monitoring unit 19 of the faulty DC / DC conversion device commands the opening of the controllable disconnector 29 so as to electrically isolate this faulty device 1 from the central power collection line. 13.

[0049] If necessary, during a step 202, the central control unit 108 can command the switching off of the entire DC / AC converter system 100 by commanding upon receipt of a signal of a malfunction of at least one of the DC / DC conversion devices 1.

[0050] This can for example be achieved by controlling the protection circuits at the DC / AC converter(s) 102 via the central unit 108. Thus, the central DC collection power line 13 is de-energized and cut off from the electrical power distribution network(s) 104, 106.

[0051] Thus, the malfunction has been isolated and the DC / AC converter system 100 is ready to operate or restart without the faulty DC / DC converter device 1.

[0052] Finally, during an optional step 204 and only if all the DC / AC converter systems 100 have been powered off, the central unit 108 delays for a predefined time, for example 150ms, and then controls the re-powering of the DC / AC converter system 100.

[0053] It is therefore understood that in this way, we can do without the RMU of the state of the art and thus greatly reduce the size, but also the cost of the DC / AC 100 converter system while maintaining on the one hand a significant safety and on the other hand guaranteeing selectivity when needed.

Claims

8 Demands

1. DC / DC conversion device (1) comprising: - a connection input (3) intended to be connected to one or more DC electrical power sources (5), - a connection output (11) intended to be connected to a central DC power collection line (13), - a first compartment (23) housing a DC / DC converter (15), - a second compartment (25) filled with a dielectric fluid and housing a controllable disconnector (29), the controllable disconnector (29) being arranged in line with the DC / DC converter (15) and downstream of it, the controllable disconnector (29) being configured to have a closed position in which current can pass between the connection input (3) and the connection output (11), and an open position in which current is interrupted between the connection input (3) and the connection output (11).

2. Device according to claim 1, wherein the controllable disconnector (29) is a pre-armed disconnector.

3. Device according to claim 1 or 2, wherein the controllable disconnector (29) is configured to be controlled by an actuator.

4. Device according to any one of the preceding claims, wherein the controllable disconnector (29) is a rotary load switch.

5. Device according to any one of the preceding claims, wherein the dielectric fluid is oil.

6. Device according to any one of the preceding claims wherein the first (23) and the second (25) compartments form a single compartment.

7. Device according to any one of claims 1 to 6 in which the first (23) and the second (25) compartments are distinct and separated by a separating wall (27).

8. Device according to claim 7, wherein the first (23) and the second (25) compartments are fluidically connected to each other.

9. Device according to any one of the preceding claims wherein it further comprises a malfunction detector (17). 9

10. Medium voltage DC / AC converter system (100) comprising - at least one DC / AC converter (1), - a central DC power collection line (13), the terminal(s) of the central power line (13) being intended to be connected to one or two electrical power distribution network(s) (104, 106) via said DC / AC converter(s) (102), - at least one DC / DC conversion device (1) according to claim 9, the DC / DC conversion device(s) (1) being connected by their connection outputs in parallel to the central DC power collection line (13) and upstream of the DC / AC converter(s) (102).

11. Medium voltage DC / AC converter system (100) comprising - at least two DC / AC converters (1), and - a central unit (108) configured to receive fault signals from the DC / DC conversion devices (1) and to shut down said DC / AC converter(s) (102) upon receiving a fault signal from at least one of the DC / DC conversion devices (1).

12. A method of operating a medium-voltage DC / AC converter system (100) according to claim 10 or 11, wherein - the controllable disconnector (29) of a DC / DC conversion device (1) is activated to isolate it from the central DC collection power line (13).

13. Method according to claim 12, according to which - the DC / AC converter system (100) is switched off - we delay for a predetermined amount of time, - the DC / AC converter system (100) is put back under power.

14. A method according to any one of claims 11, 12 or 13, wherein before actuating the controllable disconnector (29), the DC / AC converter system (100) is switched off.

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