WO2020053758A1

WO2020053758A1 - Low- voltage backup energy system, particularly for railway signaling

Info

Publication number: WO2020053758A1
Application number: PCT/IB2019/057617
Authority: WO
Inventors: Adriano Zanfei; Ernesto MIORANDO
Original assignee: C.R.D. Centro Ricerche Ducati Trento S.R.L.
Priority date: 2018-09-11
Filing date: 2019-09-10
Publication date: 2020-03-19
Also published as: EP3850724A1

Abstract

The present invention concerns a low- voltage backup energy system (1), particularly for railway signaling, provided with a plurality of supercapacitors (C1 -C18) inserted in an electric circuit (2) and connected to each other and provided with a protection device (3) connected to the plurality of supercapacitors (C1-C18) for opening/closing the electric circuit (2).

Description

LOW- VOLTAGE BACKUP ENERGY SYSTEM, PARTICULARLY FOR RAILWAY SIGNALING

Technical Field

The present invention relates to a low-voltage backup energy system, and more precisely to a backup system for railway signaling which is able both to store and deliver power.

Background Art

In the remainder of the present description and in the subsequent claims, the term“railway signaling” is used to refer to all those fixed, movable, luminous or non-luminous devices located along the railway line and adapted to provide information to train drivers in order to ensure the correct and safe movement of trains on railway lines.

In rail-type transport systems, e.g., of the overhead line or third rail type, the power supply of railway signaling is provided by conventional power supply systems connected to the power distribution network and by auxiliary backup systems designed in particular to store energy and make it immediately available in the event of a temporary interruption of the power supply from the power distribution network. These are located along the railway network lines in specific intermediate substations.

The Applicant has established that a medium- sized railway signaling system consumes about 20 kW of power and that in the event of a power disconnection from the power distribution network, a few minutes of auxiliary power would be sufficient to ensure the start of the motor- generator of the auxiliary backup systems. It follows that a typical backup system for railway signaling must provide stored energy of about 12 MJ in order to supply 20 kW in a time frame of, e.g., 10 minutes.

To date, auxiliary backup systems usually comprise storage systems having electrochemical technology batteries, such as, e.g., lithium, lead or nickel- cadmium batteries, controlled by appropriate control electronics which adapt the voltage and current at output from the batteries to make it available according to the architecture of the railway network. However, electrochemical technology storage systems have a number of drawbacks.

First of all, such systems have very short life cycles. It is well known that a battery pack, e.g. a lead-acid pack, has to be replaced every approx. 300 cycles. Furthermore, due to their chemical conformation, one of the defects of the electrochemical storage systems is that they are very sensitive to temperatures and therefore need to be located in environments with controlled temperature which, if not complied with during operation, drastically reduces the overall working life of the battery.

The Applicant has observed that in conditions of energy demand lower than those required for railway signaling systems, e.g. around a few kilowatts, the use is known of supercapacitor storage systems instead of electrochemical storage systems.

Supercapacitors are in fact known for their very high power densities and Farad capacities: this makes it possible to accumulate and release energy in a very short time.

However, one of the problems in the use of supercapacitors is that the release of this energy in such a short time exposes the component to dangerous electrical discharges of high intensity, especially during any maintenance operations.

To overcome such drawback, it is usual, according to the prior art, to completely discharge the capacitor before carrying out any type of maintenance, e.g., when a replacement is necessary.

The Applicant has discovered that through the use of a backup energy system wherein a plurality of supercapacitors are connected according to a particular architecture, it is possible to accumulate a high amount of energy while at the same time making it possible to make any replacements or service the system in complete safety.

The Applicant has further realized that, in relation to the power current supplied and the state of charge, the voltage variation in conventional electrochemical storage systems has an extremely flat profile. As a result, the control electronics are adapted to manage these energy profiles, typical of backup technologies using electrolytic systems, wherein the difference in potential has an almost constant profile.

Description of the Invention

The Applicant has therefore observed that by creating a suitably programmed electronic circuitry it is possible to adapt the output voltage profile of the supercapacitors so as not to have to make substantial changes to the auxiliary backup system of the railway signaling network.

The Applicant has thus developed a low-voltage backup energy system for railway signaling with functional characteristics such as to satisfy the above requirements and at the same time to overcome the drawbacks mentioned with respect to prior art.

The present invention therefore relates to a low-voltage backup energy system, particularly for railway signaling according to claim 1.

Brief Description of the Drawings

Other characteristics and advantages of the low- voltage backup energy system, according to the present invention will become more evident from the description of several preferred embodiments thereof, illustrated by way of an indication yet not limited thereto, in the accompanying tables of drawings in which:

Figure 1 shows a perspective view of the low-voltage backup energy system contained in a cabinet in accordance with the present invention, Figure 2 shows a perspective view of the interior of the cabinet of Figure 1,

Figure 3 shows an example of a circuit diagram of the backup energy system according to a preferred embodiment of the present invention, Figure 4 shows a further embodiment of the circuit diagram of Figure 3, Figure 5 shows a diagram of a supercapacitor module present in the circuit diagram of Figure 3,

Figure 6 shows a diagram of the module of Figure 5 when it is associated with a control network,

Figure 7 shows a perspective view of a variant of the cabinet of Figure 1. Embodiments of the Invention

In the remainder of the present description and in the subsequent claims, the term“low voltage” is used to refer to voltages generally lower than 1 kV.

With particular reference to the annexed illustrations, reference numeral 1 globally designates a low-voltage backup energy system in accordance with the present invention.

The backup energy system 1 is made starting from an electric circuit 2 preferably housed inside a cabinet 7. The cabinet 7 comprises a frame structure 8 resting or fixed to the ground, substantially parallelepiped, and accessible from the outside by means of one or more doors 9 hinged to the frame 8, the latter being openable and closable depending on the requirements by qualified technical staff.

The cabinet 7 can also have one or more openings 7a for housing displaying devices, such as displays or screens, for the interface with the energy system 1 , as will be explained in detail later on in the present description.

With reference to the example shown in Figure 2, the cabinet 7 is preferably divided into compartments 10 for housing a plurality of supercapacitors C connected together.

Each compartment 10 comprises a plurality of shelves 11 which are extractable towards the doors 9 and intended to support the supercapacitors C. The supercapacitors C are preferably organized in modules M.

As shown in the example of Figure 2, the cabinet 7 preferably has six compartments 10 arranged upstream and downstream of the central compartment bearing the display.

In this specific case, each of the four central compartments contains 18 modules, while each of the outermost compartments contains 12 modules for a total of 96 modules connected in six series and sixteen parallels.

With reference to the example shown in Figure 3, the backup energy system 1 comprises a plurality of strings S arranged in parallel to each other between two positive and negative transmission lines 12, 13. Each transmission line 12,13 connects respective upstream terminals 14,15 and downstream terminals 16,17. The backup system 1 also comprises an AC/DC converter 6 having a DC section connected to the upstream terminals 14,15 of the backup system 1 and an AC section connected to the electricity distribution network. The backup system 1 is therefore intended to receive power from the electricity distribution network to accumulate it in the supercapacitors C and make it immediately available in the event of a temporary power delivery failure on the part of the electricity distribution network.

Preferably, the backup system 1 is intended to deliver energy for railway signaling. However, in other application examples, this system can be used in any other area where it is necessary to deliver large amounts of energy in a short time.

Still with reference to the example shown in Figure 3, each string S preferably comprises a plurality of supercapacitor modules M connected in series with each other. It should be noted that, although in the example of Figure 3 only six modules and three strings are illustrated for illustrative simplicity, the backup system 1 can preferably comprise up to sixteen strings S for a total of ninety-six supercapacitor modules M.

According to the embodiment shown in the example of Figure 5, each supercapacitor module M comprises a plurality of supercapacitors C connected in series with each other. It should be noted that, although in the example of Figure 4 three supercapacitors Cl, C2, Cl 8 are shown, each supercapacitor module M can preferably comprise up to eighteen supercapacitors C. Obviously, for a person skilled in the art, it will be evident that the number and the type of elements (strings, modules, supercapacitors, etc.) of the backup system can be varied according to the needs and the amount of energy to be delivered.

Conveniently, the backup system 1 can operate under different conditions:

a) pick-up/charge condition, wherein the system receives energy from the distribution network for the storage of same in the supercapacitors C; b) delivery condition, wherein the system delivers energy to the railway line through the supercapacitors C; c) detachment condition, wherein one or more supercapacitors C have to be replaced.

Advantageously, as shown in Figure 5, each supercapacitor module M comprises a protection device 3 and an interfacing device 4 arranged upstream and downstream of the supercapacitors Cl -Cl 8 respectively between the positive module terminals 19 and negative module terminals 20.

The protection device 3 is connected in series to the Cl -Cl 8 supercapacitors and is designed to open/close the electric circuit 2 and to protect against possible electric arcs during the detachment of the supercapacitors. For this purpose, the protection device 3 comprises a first branch 3a provided with a switch SW1 and a second branch 3b provided with a resistor Rl and a switch SW2. Conveniently, the branches 3a, 3b are connected in parallel with each other.

It should be noted that in the pick-up/charge and delivery conditions, the switch SW1 is normally closed while the switch SW2 is normally open. In the detachment condition, the switch SW 1 is advantageously opened and the switch SW2 is closed so that the resistance Rl limits the current on the power connections of the module M, thus avoiding the occurrence of possible electric arcs which are dangerous for the staff in charge of maintenance and/or the replacement of one or more supercapacitors.

The interfacing device 4 is connected on one side to the ends of the supercapacitors C1-C18 and on the other to the positive interfacing terminal 21 and negative interfacing terminal 22. The interfacing device 4 is designed to charge or discharge the supercapacitors C1-C18. For this purpose, it comprises a first branch 4a and a second branch 4b each provided with a respective switch SW3, SW4. Conveniently, the branches 4a, 4b are connected in parallel to each other.

Preferably, each supercapacitor C is characterized by an electrical capacity having a value between 1000 F and 10000 F, preferably corresponding to 3000 F, and by an operating voltage substantially corresponding to 2.75 V, but usable between 2.2 and 3 V. It follows that, for each supercapacitor module M, the voltage to the module terminals 19,20 is substantially equal to 49.5 V.

In accordance with the preferred embodiment shown in the example of Figure 4, the backup system 1 comprises sixteen strings S (for illustrative convenience only three strings are visible), each comprising six modules M, the strings being connected in parallel with each other for a total of ninety- six supercapacitor modules M. It follows that the electric circuit 2 can comprise up to 1728 supercapacitors C the potential difference of which at the downstream terminals 16, 17 is substantially corresponding to 297 V in direct current.

Considering the formula,

E - -CV²

2

the quantity of energy dispensable for each supercapacitor C is , 75²

equal therefore to about 11.3 kJ. Multiplying the energy E by the total number of supercapacitors C present in the backup system we obtain a total energy value of about 19.6 MJ. However, considering that the minimum voltage at which it is preferable to discharge each supercapacitor is one third of the initial voltage, the energy extractable from the system is therefore equal to about 17.4 MJ. Assuming a system efficiency of h = 0.85, we obtain an operating autonomy of 24 kW, deliverable in 10 minutes, therefore with a margin of 20% compared to the 20 kW assumed at the start.

According to the embodiment shown in Figure 5, the backup system 1 further comprises a step-up device 23 designed to stabilize the output voltage during the discharge cycle of the supercapacitors C. Preferably, the step-up device 23 is connected in parallel to the last string S of the supercapacitors C.

In accordance with a further embodiment, the backup system 1 comprises an additional string S’ of supercapacitors C downstream of the step-up device 23. This additional string S’ permits, advantageously, maintaining a delivery as appropriate as possible to the charge to be supplied without particular variations in current. In this embodiment as well, the additional string S’ comprises six supercapacitor modules M connected to one another in series for a total of 108 supercapacitors M.

Advantageously, the backup energy system 1 also comprises a CAN-BUS or MOD-BUS control network 5 managed by a CPU 25. As shown in the example in Figure 5, the CAN-BUS or MOD-BUS control network 5 and the CPU 25 make it possible to control the operation of all the supercapacitor modules M, the AC/DC converter 6 and the step-up device 23, as well as the interfacing of the various elements present in the system and the monitoring thereof.

In detail, with reference to the example in Figure 6, the supercapacitors Cl -Cl 8 of each module M can be monitored from the CAN-BUS or MOD-BUS network 5 by interfacing with a linear optocoupler 23 in signal communication with a microcontroller 24. Each microcontroller 24 of the modules M is in turn communicating with the CPU 25 provided in the electrical circuit and designed to operate the backup system 1 in the different pick-up/charge, delivery, and/or detachment conditions. For this purpose, the CPU 25 is in signal communication with the supercapacitor modules M, the AC/DC converter 6 and the step-up device 23 through the CAN-BUS or MOD-BUS control network 5. The CPU 25 can also be connected to a display and to a processing system (not shown), e.g. a PLC, to monitor the backup system 1 in real-time.

Preferably, each supercapacitor module M comprises a DC/DC converter 26 intended to supply the microcontroller 24, preferably starting from a voltage of 24 V.

As shown in the example in Figure 6, each supercapacitor module M comprises a switch SW5 controlled by the microcontroller 24 for the release of the module M when the latter is completely discharged (e.g., for removal during maintenance) and an additional switch SW6 adapted to close when the module M is reinserted in the system following, for example, maintenance.

Conveniently, each supercapacitor module M can also comprise signaling means 29 (e.g. led) piloted by the microcontroller 24 to signal the status of the module M (charge, discharge, error, etc.) and a CAN or MODBUS interface module 30 for the communication of the modules M with the CPU 25. In accordance with a preferred embodiment, the backup system 1 is equipped with recharging means 27 connected to the electricity distribution network upstream of the AC/DC converter 6, as well as of a power resistor 28 for discharge (Figures 3 and 4). The recharging means 27 and the power resistor 28 make it possible, advantageously, to charge and discharge the supercapacitors C, for example, in the detachment condition. As described above, in this condition it is necessary to replace one or more supercapacitors C which, before being disengaged from the system, can be discharged thanks to the presence of the power resistor 28; the new supercapacitors C can instead be recharged thanks to the presence of the recharging means 27.

In accordance with the embodiment shown in Figure 7, each compartment 10 of the cabinet 7 can house a number of supercapacitors C with a preferably polygonal shape, e.g., prismatic. Advantageously, the prismatic shape permits a simplified construction with a more scalable shape factor compared to the typical cylindrical- shaped supercapacitors.

Preferably, the supercapacitors C are assembled one on top of the other in a vertical configuration so that a single module M represents the equivalent of six modules M (with respect to the embodiment of Figure 2). It follows that all the modules M can be connected to each other exclusively in parallel and each module M can be detached from the backup system using a single connector. Still with reference to the embodiment of Figure 7, each compartment can comprise up to 8 modules M of supercapacitors C. Advantageously, the modules M can be extracted towards the outside by means of a slide l la constrained to the frame 8 so that each module M is easily replaceable depending on the needs of qualified personnel.

As it has been possible to determine from the present description, it has been ascertained that the described invention achieves the intended objects and in particular the fact is underlined that by means of the low-voltage backup energy system for railway signaling it is possible to avoid the onset of possible unintended electrical discharges during the replacement of the supercapacitors or system maintenance. The presence of the protection device controlled by the CAN-BUS or MOD-BUS control network according to predefined programming permits the detachment of the supercapacitors in a safe manner. Moreover, thanks to the special interface of the supercapacitor modules, of the converter and of the step-up device to each other, the electrical performance of the backup system can be effectively optimized. The presence of appropriate computerized means, e.g. PLC and related sensors, makes it possible to monitor the system during all operating conditions.

The described embodiments of the system are potentially endless and an expert in the field, in order to meet contingent needs, can make numerous changes and variations, all contained within the scope of protection of the invention, as defined by the following claims.

Claims

1) Low-voltage backup energy system (1), characterized by the fact that it comprises:

a plurality of supercapacitors (Cl -Cl 8) inserted in an electric circuit (2) and connected to each other, and

a protection device (3) connected to said plurality of supercapacitors (Cl -Cl 8) for opening/closing said electric circuit (2).

2) System (1) according to claim 1, comprising a plurality of supercapacitor modules (M1-M96) connected in series with each other and wherein each supercapacitor module (M1-M96) comprises said plurality of supercapacitors (C1-C18) and said protection device (3).

3) System (1) according to claim 1 or 2, comprising an interfacing device (4) for connecting said plurality of supercapacitors (Cl -Cl 8) to an external interface.

4) System (1) according to any one of claims from 1 to 3, wherein said protection device (3) comprises:

a first branch (3a) comprising a switch (SW1),

a second branch (3b) comprising a resistor (Rl) and a switch (SW2), and wherein said branches (3a, 3b) are connected in parallel with each other.

5) System (1) according to any one of claims from 1 to 4, wherein said interfacing device (4) comprises:

a first branch (4a) and a second branch (4b) each comprising a respective switch (SW3, SW4),

and wherein said branches (4a, 4b) are connected in parallel with each other.

6) System (1) according to any one of claims from 2 to 5, comprising a plurality of strings (S1-S18) connected in parallel with each other and wherein each string (S1-S18) comprises six of said supercapacitor modules (Ml- M96).

7) System (1) according to any one of claims from 1 to 6, comprising a CAN- BUS control network (5) and a CPU (25) for controlling the operation of said supercapacitor modules (M1-M96) and said AC/DC converter (6) so that, in case of detachment of one of said supercapacitors (Cl -Cl 8), said protection device (3) is activated for opening/closing said electric circuit (2). 8) System (1) according to any one of claims from 1 to 7, comprising an AC/DC converter (6) for connecting said electric circuit (2) to the electric power distribution network.

9) System (1) according to any one of claims from 1 to 8, wherein said supercapacitors (Cl -Cl 8) have a preferably cylindrical or prismatic shape and are housed in a cabinet (10) accessible from the outside by means of one or more doors (9) openable and reclosable according to requirements.

10) System (1) according to any one of claims from 1 to 9, suitable to be connected to a railway supply network.