IT201800004702A1 - SYSTEM AND METHOD OF CHARGING A DIRECT CURRENT ELECTRIC VEHICLE - Google Patents

Description

DESCRIPTION

Attached to a patent application for INDUSTRIAL INVENTION having the title

“SYSTEM AND METHOD OF CHARGING AN ELECTRIC VEHICLE IN

DIRECT CURRENT"

The present invention relates to a system and a method of recharging a direct current electric vehicle.

In particular, the invention proposed here is used in the domestic / residential environment, or in the industrial sector, both private and public.

The accumulation of electrochemical energy in emergency applications, for example in static uninterruptible power supplies or UPS (acronym of the English term "Uninterruptible Power Supply"), has been known for some time.

More recently, the spread of energy production plants from renewable sources, such as photovoltaic and wind power, has laid the foundations for the development of an "intelligent" electricity distribution network - commonly known as a "smart grid" - which , in addition to the centralized generation of electricity, it supports a distributed generation thanks to a plurality of peripheral nodes, even small ones, from which the energy flows are bidirectional (from the center to the nodes and from the nodes to the center).

Since, by their very nature, renewable sources are not programmable, distributed generation requires a more complex control system, capable of dynamically managing (i.e. in real time) the excess energy of some nodes, accumulating energy in suitable devices and / or redistributing it to other deficient nodes, and able to regulate centralized generation at the same time.

Subsequently, the saturation of the energy market and the consequent cut in incentives for the use of renewable sources, has increasingly directed towards self-consumption, so that each peripheral node maintains itself by accumulating surplus energy to reuse them during periods of scarce or nothing.

This approach makes it possible to increase the independence of the nodes from the central network and to adopt so-called "peak shaving" solutions, that is, which avoid resorting to the network during periods of maximum demand.

Figure 1 illustrates the block diagram of a known energy storage management system 1 (typically but not limited to electrochemical), in which the division between a DC current / voltage domain and a current / voltage domain is schematised. in alternating AC.

The fundamental element of system 1 is a bidirectional inverter 2, that is a DC / AC static converter from DC domain to AC domain, and vice versa.

The alternating current coming from the public electricity grid R and / or from local electricity generation devices G (e.g. renewable sources and / or motogenerators) feeds one or more AC users U and, in case of excess, is sent to the bidirectional inverter 2 to be transformed into direct current and stored in an accumulator 3, for example a battery.

System 1 also includes a disconnecting device 7 interposed between the bidirectional inverter 2 and the public electricity grid R.

During periods of low availability of power from the G grid, the flow is reversed: the direct current is supplied by the battery 3, which powers the bidirectional inverter 2, which then feeds the different users U with alternating current.

Common electric vehicle charging devices are connected to the AC domain (i.e. they appear as AC user U).

For example, document US 2012/206104 proposes an AC vehicle charging system, through connector 23, which directly draws energy from the AC distribution unit. The DC / DC converter 213, on the other hand, is not used to power the vehicle but only to draw energy from the vehicle.

It should be noted that one of the main obstacles to the spread of electric vehicles - in addition to cost - is linked to long waiting times for recharging: a few hours against a few minutes for normal endothermic motor vehicles. This is also due to the fact that the AC charger has a limited power, just as the power available in a residential environment is limited.

In the state of the art, there are also electric vehicles with a direct current charging system.

Figure 2 shows the block diagram of a direct current charging system 10 of an electric vehicle V, according to the state of the art.

Here too the division between the DC current / voltage domain and the AC current / voltage domain has been schematized.

Beyond the elements present in the system 1 of figure 1, the recharging system 10 of figure 2 also comprises a static AC / DC converter 4, which receives alternating current from the public electricity network R and / or from local generation devices G of electricity (e.g. renewable sources and / or motor generators) or from the electrochemical accumulator 3 through the bidirectional inverter 2 and transforms it into direct current to be stored directly in the battery installed on board the vehicle V.

On board the electric vehicle V there is a connector that allows you to connect directly to your battery for continuous recharging.

Therefore, in this case the limit of the power flow towards the electric vehicle V is defined by the lower power between the battery 3, the AC / DC static converter 4, the bidirectional inverter 2 and the power available from the grid R or from the local generation G.

In this way, the charging times of an electric vehicle are lowered from a few hours to 15-20 minutes, thus becoming comparable with the charging times of endothermic motor vehicles.

The main disadvantage of this solution is linked to the need to have high power from the local and / or public grid and to the need to oversize the bidirectional inverter (which is the main cost item of the system together with the battery) to satisfy power requests. high for medium-long periods (e.g. over 5 minutes), making the system not usable in a domestic / residential environment.

For example, document WO 2011/078397 proposes a power supply system for an electric vehicle comprising a plurality of DC / DC converters, in which the attention here is focused on the DC / DC converter indicated with the number 15. This converter, which it is unidirectional and has the sole purpose of converting the voltage supplied by the battery 52 into a predetermined output voltage value.

The only AC / DC converter 16 is unidirectional, in fact it is configured to convert the AC input (from power supply 100) to DC output.

The vehicle recharging system always includes a double conversion stage, with relative loss of efficiency to date. For example, to recharge the battery 52 from the 100 network, the AC / DC 16 and the DC / DC 15 are used. To recharge the vehicle, the DC / DC 21 (which is unidirectional) is then used. in WO 2011/078397 it was obtained using two DC / DC converters: number 21 precisely, which takes energy from line L2 and pours it into the vehicle, and number 22 which takes energy from the vehicle and pours it back onto line L1.

In this context, the technical task underlying the present invention is to propose a system and a method of recharging an electric vehicle in direct current, which overcome the drawbacks of the prior art mentioned above.

In particular, the object of the present invention is to propose a system and a method of recharging a direct current electric vehicle, which allow rapid recharging even in situations of limited power availability.

A further object of the present invention is to propose a system and a method of recharging an electric vehicle in direct current, which simplify the management of recharging from the user side, reducing waiting times and increasing the availability of recharging sites, for example in the field domestic / residential or in public / private parking areas. Another object of the present invention is to propose a system and a method of recharging a direct current electric vehicle, which are as autonomous as possible from the network, thus avoiding an increase in the price of energy.

The specified technical task and the specified purposes are substantially achieved by a direct current electric vehicle recharging system, comprising:

- energy storage means, for example one or more electrochemical batteries or one or more capacitive accumulators or one or more kinetic accumulators;

- a bidirectional DC / AC converter having a DC section connected to the energy storage means and an AC section that can be connected to a local power source or to a public electricity network;

- a DC / DC converter having a first DC section connected to the energy storage means and a second DC section connectable to the electric vehicle to power it.

Preferably, the DC / DC converter is of the bidirectional type. The first DC section of the DC / DC converter is also connected to the DC section of the DC / AC converter.

Preferably, the recharging system comprises a disconnecting device connected to the AC section of the DC / AC converter and connectable to the public electricity network.

Further characteristics and advantages of the present invention will become clearer from the indicative, and therefore non-limiting, description of a preferred but not exclusive embodiment of a system and method of charging a direct current electric vehicle, as illustrated in the accompanying drawings. in which:

- Figures 1 and 2 respectively illustrate block diagrams of an energy storage system and a charging system for an electric vehicle, according to the known art;

- figure 3 the block diagram of a recharging system for a direct current electric vehicle, according to the present invention.

With reference to Figure 3, the number 100 indicates a recharging system for an electric vehicle V in direct current, in particular for use in a domestic / residential environment, or in an industrial environment, both public and private.

The recharging system 100 comprises a main recharging device 200 and an auxiliary device 110 electrically connected to each other.

The main recharging device 200 comprises a primary bidirectional DC / AC converter 2 (or bidirectional inverter) having a DC section 2a and an AC section 2b.

Figure 3 schematizes the division between a DC current / voltage domain and an AC current / voltage domain.

Primary DC / AC converter 2 is configured for:

- transforming the DC electrical signal acquired by the DC section 2a into an AC electrical signal supplied through the AC section 2b;

- transforming the AC electrical signal acquired by the AC section 2b into a DC electrical signal supplied through the DC section 2a.

In this context, an electrical signal means a signal representative of an electrical quantity, such as current or voltage. The main recharging device 200 comprises main energy storage means 3.

Preferably, the energy storage means 3 comprise one or more electrochemical batteries, for example connected in parallel.

For example, the batteries 3 are lead-acid or lithium-ion or nickel-metal hydride batteries.

Alternatively, the main energy storage means 3 comprise one or more capacitive accumulators or one or more kinetic accumulators.

The DC section 2a of the primary DC / AC converter 2 is connected to the main energy storage means 3.

The AC section 2b can be connected to a local power source G, such as a renewable source of electricity (photovoltaic, wind, etc.), or a motor generator.

The main recharging device 200 comprises a main control unit 14 connected at least to the main energy storage means 3 to control the state of charge thereof.

The main control unit 14 is advantageously connected to all the components of the main charging device 200.

The recharging system 100 also comprises an auxiliary device 110 connected to the DC section 2a of the primary DC / AC converter 2. Advantageously, the auxiliary device 110 is arranged in a residential or industrial room other than that where the main recharging device 200 is located. and is connected to the same by normal electrical wiring.

The auxiliary device 110 comprises secondary energy storage means 30 and a connection to a public electricity network R.

The secondary accumulation means 30 can comprise one or more batteries 31, 32, 33 preferably having the same characteristics as those of the main accumulation means 3.

The auxiliary device 110 further comprises a secondary DC / AC converter 20 having a DC section 20a connected to the secondary energy storage means 30 and an AC section 20b which can be connected to a public electricity network R.

The auxiliary device 110 further comprises a secondary control unit 40 connected to the main control unit 14 of the main recharging device 200 and to the secondary energy storage means 30. The main recharging device 200 further comprises a disconnecting device 7 ( per se known) connected to the AC section 2b of the primary DC / AC converter 2 and to the public electricity grid R.

The main recharging device 200 further comprises a DC / DC converter 6 having a first DC section 6a and a second DC section 6b, the purpose of which is to convert the DC voltage of the energy storage means 3 into a suitable DC voltage. to the vehicle battery V.

The second DC section 6b is preferably of the variable voltage type in order to adapt to the battery voltage of the vehicle V.

The first DC section 6a is connected to the energy storage means 3, while the second DC section 6b can be connected to the electric vehicle V to power it.

Preferably, the DC / DC converter 6 is also of the bidirectional type. In addition to the main energy storage means 3, the first DC section 6a of the bidirectional DC / DC converter 6 is also connected to the DC section 2a of the DC / AC converter 2 and to the auxiliary device 110.

Advantageously, moreover, the main control unit 14 of the main device 200 is configured to monitor the state of charge of the main energy storage means 3 and send a related signal to the secondary control unit 40 of the auxiliary device 110.

Furthermore, the secondary control unit 40 is preferably configured to electrically connect at least a first 31 secondary energy storage means with the DC section 2a of the primary DC \ AC converter 2 of the main recharging device 200.

Advantageously, moreover, the secondary control unit 40 carries out the electrical connection between at least the first 31 secondary energy storage means with the DC section 2a of the primary DC / AC converter 2 when it receives a signal from the main control unit 14 relating to the exhaustion of the charge of the main energy storage means 3.

The secondary control unit 40 also monitors the state of charge of the first 31 secondary energy storage means 30 (and advantageously also of the subsequent means 32, 33 ..) and is configured to disconnect it from the DC section 2a of the DC converter. Primary AC 2 when the same first secondary storage medium 31 runs out of charge.

Advantageously, moreover, the secondary control unit 40 of the auxiliary device 110, following the occurrence of the condition of exhaustion of the charge of the first secondary storage means 31, is configured to make the electrical connection between at least a second 32 secondary energy storage means with the direct current section 2a of the primary DC / AC converter 2 of the main recharging device 200. The method of recharging a direct current electric vehicle, according to the present invention, is described below.

In periods of excess energy from the local power source G or from the public electricity grid R, the primary DC / AC converter 2 of the main charging device 200 converts the AC electrical signal acquired by its AC section 2b into an electrical signal in continuous, which is accumulated in the main batteries 3 (or, more generally, in the main accumulation means).

In the same periods of excess energy from the public electricity network R, the secondary DC / AC converter 20 of the auxiliary device 110 converts the AC electrical signal acquired by its AC section 20b into a DC electrical signal, which is accumulated in the batteries 30 (or, more generally, in secondary storage means). The energy stored in the main 3 and secondary batteries 30 is used to recharge, if necessary, the electric vehicle V through the DC / DC converter 6, with a power flow that goes from the first DC section 6a to the second DC section 6b .

The DC / DC converter 6 is, in the present invention, the only component sized to make a high power flow towards the vehicle V.

In particular, once the control unit 14 of the main device 200 verifies the exhaustion of the main battery 3, it is configured to communicate and command the secondary control unit 40 so that the latter enables the electrical connection between the batteries 30 and vehicle V being recharged.

In practice, by means of this connection, a plurality of batteries (3 and 30) are obtained, connected in sequence to the vehicle V.

Furthermore, in periods of low energy production, it is the main battery 3 or the secondary ones 30 that supplies a direct electrical signal to the direct current section 2a of the DC / AC converter 2, which converts it into an alternating electrical signal, made available to one or more users U through the alternating section 2b.

If a bidirectional DC / DC converter 6 is used, the energy can also be drawn from the electric vehicle V (in particular from its battery) through the second DC section 6b and made available to the local network G or to the users U through the DC / AC converter 2 (with power flow from its DC section 2a to the AC section 2b).

The disconnecting device 7 is able to communicate to the other elements of the recharging system 100 (e.g. to the DC / AC converter 2, to the energy storage means 3, to the DC / DC converter 6, to the energy generator if present, etc. .) a signal representative of the presence / absence of the network.

This communication can take place with known radio technologies, such as bluetooth, ZigBee, Wi-Fi or through the transmission of data on power networks (eg the so-called “power line communication”).

In response to this signal representative of the presence / absence of the network, each element of the recharging system 100 sets predefined parameters for that state.

Even in the event of a power failure (black-out) it is therefore possible to continue to power the U users.

For example, in the event of a power failure, it is possible to limit and / or postpone the activities of particularly expensive AC users (e.g. ovens, dishwashers, washing machines, etc.) or limitations can be set on the drawing of power from the batteries 3 from part of DC / AC converter 2 or DC / DC converter 6.

From the above description the characteristics of a direct current electric vehicle recharging system and method according to the present invention are clear, as are the advantages. In particular, the proposed recharging system allows rapid recharging of the electric vehicle continuously even in situations of limited availability of power both from local generation and from the public network.

The system is substantially autonomous from the network and works even in the event of a blackout.

The proposed charging system can also be used in the home / residential area, thus helping to increase the user's confidence in electric vehicles.

Claims (10)

CLAIMS 1. Recharging system (100) of an electric vehicle (V) in direct current, comprising a main recharging device (200), said main recharging device (200) comprising: main energy storage means (3); a primary bidirectional DC / AC converter (2) having a DC section (2a) connected to said main energy storage means (3) and an AC section (2b) connectable to a local power source (G) or to a public electricity network (R); a single bidirectional DC / DC converter (6) having a first DC section (6a) which is connected both to the main energy storage means (3) and to the DC section (2a) of the primary DC / AC converter (2 ), and a second continuous section (6b) connectable to said electric vehicle (V) to power it, at least one main control unit (14) connected at least to said main energy storage means (3), said recharging system ( 100) being characterized in that it further comprises an auxiliary device (110) connected to said DC section (2a) of said primary DC / AC converter (2) of said main recharging device (200), said auxiliary device (110) comprising secondary energy storage means (30), a connection to a public electricity network (R), a secondary DC / AC converter (20) having a DC section (20a) connected to said secondary energy storage means (30 ) and a section in alternating current (20b) connectable to a public electricity network (R) and a secondary control unit (40) connected to said main control unit (14) and to said secondary energy storage means (30). Charging system (100) according to claim 1, wherein said main control unit (14) is configured to monitor the state of charge of said main energy storage means (3) and send a relative signal to said unit secondary control (40) of said auxiliary device (110). Recharging system (100) according to any one of the preceding claims wherein said secondary control unit (40) is configured to electrically connect at least one first (31) of said secondary energy storage means (30) with said section in continuous (2a) of said primary DC / AC converter (2) of said main recharging device (200). Recharging system (100) according to claim 3 wherein said secondary control unit (40) carries out the electrical connection between at least said first (31) secondary energy storage means (30) with said DC section (2a) of said primary DC / AC converter (2) when it receives a signal from said main control unit (14) relating to the exhaustion of the charge of said main energy storage means (3). Charging system (100) according to claim 4 wherein said secondary control unit (40) monitors the state of charge of said first (31) secondary energy storage means (30) and is configured to disconnect it from said section in direct current (2a) of said primary DC / AC converter (2) when the charge exhaustion of the same first secondary storage medium (31) occurs. Recharging system (100) according to claim 5 wherein said secondary control unit (40) of said auxiliary device (110), after the occurrence of the condition of exhaustion of the charge of said first secondary storage means (31), it is configured to make the electrical connection between at least one second (32) secondary energy storage means with said DC section (2a) of said primary DC / AC converter (2) of said main recharging device (200). Recharging system (100) according to any one of the preceding claims, wherein said primary DC / AC converter (2) of said main recharging device (200) is configured for: - transforming a DC electrical signal acquired by the DC section (2a) into an AC electrical signal supplied through the AC section (2b); - transforming an AC electrical signal acquired by the AC section (2b) into a DC electrical signal supplied through the DC section (2a). Charging system (100) according to any one of the preceding claims, wherein said main charging device (200) further comprises a disconnecting device (7) connected to the AC section (2b) of said DC / AC converter (2 ) and can be connected to the public electricity network (R). Recharging system (100) according to any one of the preceding claims, wherein the second continuous section (6b) of the DC / DC converter (6) is of the variable voltage type in order to adapt to the battery voltage of the electric vehicle (V). Method for recharging an electric vehicle (V) in direct current by means of the recharging system (100) according to one or more of the preceding claims, comprising the steps of: - converting an AC electrical signal into a DC electrical signal through the primary DC / AC converter (2) of said main recharging device (200) and accumulating said DC electrical signal in the main energy storage means (3); - converting an AC electrical signal into a DC electrical signal through the secondary DC / AC converter (20) of the auxiliary device (110) and accumulating said DC electrical signal in the secondary energy storage means (30), - converting the DC electrical signal accumulated in the main energy storage means (3) into another DC electrical signal through the DC / DC converter (6) and making said other DC electrical signal available to the electric vehicle (100) through the second DC section (6b) of the DC / DC converter (6), - upon reaching the exhaustion of charge of said main energy storage means (3) of said main recharging device (200) converting the continuous electrical signal stored in the secondary energy storage means (30) into another electrical signal through the DC / DC converter (6) and making said other DC electrical signal available to the electric vehicle (100) through the second DC section (6b) of the DC / DC converter (6).