Patent Application
20250055285
The present invention relates to a polyphase and DC voltage supply system. The invention further relates to a corresponding supply method.
Energy optimization in battery-powered stand-alone systems is very important because on-board energy is limited by cost, weight and volume.
In a stand-alone system, the battery provides the power needed to supply a plurality of elements or peripherals of the system. For example, in electric transport systems such as electric bicycles, electric cars, electric scooters among others, the battery can power at the same time a three-phase electric motor, a lighting device or a human-machine interface.
Thereby, in the case of a system comprising a three-phase electric motor and one or a plurality of devices to be supplied continuously, a battery pack is used to supply both the motor and the other devices.
More precisely, for the supply of the electric motor, the energy of the three phases is taken from the same battery pack by an inverter. The inverter is used to convert the DC voltage leaving the battery pack into the three AC voltages, forming the three phases of the device to be supplied with power.
For other devices to be supplied, the output voltage of the battery is further used to generate the different supply voltages through at least one DC/DC converter.
The above means that in addition to the battery pack(s), an inverter and at least one DC/DC converter are used, which means losses in energy consumptions.
There is thus a need for a power supply system which can supply both a DC voltage and a polyphase voltage with reduced losses of energy consumptions.
To this end, the description describes a power supply system suitable for supplying a polyphase voltage and a direct voltage, the power supply system comprising at least three modules, each module including:
It should be understood here that the present invention proposes to use a battery with switched accumulators as a battery pack. A switched storage battery is a battery comprising a plurality of generally identical modules connected in series and/or in parallel, the number of which depends on the desired voltage across the battery. Each module comprises a plurality of electric accumulators. Switches connected in series and in parallel with the accumulators enable each accumulator or set of accumulators either to be or not to be connected in series and/or in parallel between output nodes of the module, so as to choose the output voltage from the different combinations of voltages supplied by the accumulators.
In fact, one advantage of a switching battery is to avoid the use of an inverter.
As a result, it is thereby possible to have reduced losses in energy consumption, compared with the prior art.
However, the present invention solves an additional problem.
Indeed, using a switching battery for a three-phase power supply, used e.g. to supply an electrical machine, presumes separating the battery into three subassemblies, each attached to a phase. Each subassembly has two output poles, one pole is connected to the three-phase machine to form a phase and the other pole is used to produce the neutral point of the power supply. More precisely, the so-called “neutral” poles of each subassembly are connected to each other to form the neutral point.
To supply additional DC devices from the switching battery, at least one switched-mode power supply could be used to draw a DC voltage from one of the subassemblies.
But the energy is to be drawn from the three subsets in a balanced way, so as not to unbalance the subassemblies with regard to each other. Indeed, if one of the subassemblies has discharged, the subassembly no longer supplies current for the three-phase motor. The three-phase motor is then no longer supplied whereas the other two subassemblies still have available energy. Switched-mode power supplies could then be used for all the subassemblies, but the system would be bulky and expensive.
By means of the proposed circuit, the present invention provides a solution to the technical balancing problem by permitting the generation of both a direct voltage and a polyphase voltage for all use cases.
Moreover, it may also be noted herein that the selection circuit is to be understood as a circuit for selecting cells participating in the supply of the polyphase voltage. As such, a selection of no cell (for the case of a passage to 0V for one phase), of one cell or of two cells are possible selection configurations, as well as a selection with more than two cells.
According to particular embodiments, the power supply system has one or a plurality of the following features, taken individually or according to all technically possible combinations:
To this end, the description describes a method of providing a power supply implemented by a power supply system as described hereinabove, wherein the method includes the control of the circuits of the power supply system so that the power supply system provides a desired DC voltage and a desired polyphase voltage, in particular a three-phase voltage.
According to particular embodiments, the supply method has one or a plurality of the following features, taken individually or according to all technically possible combinations:
The features and advantages of the invention will appear upon reading the following description, given only as an example, but not limited to, and making reference to the enclosed drawings, wherein:
A power supply system 10 is illustrated in
The power supply system 10 is a system ensuring the generation of a direct voltage at the output as well as a polyphase voltage operation, whether for the supply of a load with polyphase voltage or the recharging on a polyphase source and of a direct voltage at the output. The power supply system 10 is thus a DC and polyphase voltage supply system.
In the example described, the power supply system 10 is configured to generate three phases, but it is easy to adapt the power supply system 10 so that same can generate a number of phases greater than or equal to 3.
The power supply system 10 includes a “neutral” point PN, an output for each phase P1, P2 and P3, a positive pole corresponding to a positive DC voltage output DC+ and a negative pole corresponding to a negative DC voltage output DC−.
As can be seen in
Each subsystem M1, M2 and M3 corresponds to a module of a switching cell battery which is shown more precisely in
Each module M includes a plurality of cells C1 . . . . Cn where n is an integer strictly greater than 1.
In the schematic example shown in
As an illustration,
A cell C may comprise between the positive and negative poles thereof, one or a plurality of elementary energy sources placed in series and/or parallel. The voltage step of a cell C is often on the order of 3.6 V, 12 V, 24 V or 48 V but any other value is possible.
For example, the elementary energy source is an electrical charge storage element, such as an electrochemical element or an electrical capacitor.
According to another example, the elementary energy source is an electric generator, e.g. a fuel cell, a zinc-air cell, a photovoltaic cell.
In yet another example, the elementary energy source is an energy recovery system, such as a mini-wind turbine or mini-turbine.
The elementary energy sources of cell C may have a mixed nature, e.g. a combination of an electrical generator and a storage element.
Each module M further includes a selection circuit 12 and a polarity switchover circuit 14 for obtaining the desired voltage(s) at the output of the module.
The selection circuit 12 is a set of switches connected to the cells C for connecting in series/parallel or for bypassing certain cells, by changing the state (opening or closing) of the switches.
More precisely, the selection circuit 12 is configured to select cells C to obtain a set of selected cells, which will participate in the generation of the phase.
The set of cells C further comprises a first end cell C1 the negative pole of which is connected to the polarity switchover circuit 14, and a second end cell Cn, the positive pole of which is connected to the polarity switchover circuit 14. The first and second end cells C1 and Cn form part of the set of cells C, and as such may be a part of a set of cells selected, but this is not mandatory.
For the case of
In the case of
More particularly, the module M of
The switches SW are e.g. transistors having an on state and an off state. Typically, insulated-gate field-effect transistors may be used, more commonly called MOSFETs. MOSFET is an acronym for Metal Oxide Semiconductor Field-Effect Transistor.
The polarity switchover circuit 14 is used to switchover the polarity of the set of selected cells, i.e. the polarity switchover circuit 14 is used to either invert or not invert the polarity of the connected cells.
In the example proposed, the polarity switchover circuit 14 is an H-bridge.
The H-bridge includes four switches SWH1, SWH2, SW H3, and SWH4.
The H-bridge comprises two branches B1 and B2 in parallel, namely a first branch B1 including, in series, the first switch SWH1 and the third switch SWH3 and a second branch B2 including, in series, the second switch SWH2 and the fourth switch SWH4.
Each branch B1 and B2 has a respective midpoint for extracting a voltage, the midpoint of the first branch B1 corresponding to a negative output OUT− and the midpoint of the second branch B2 corresponding to a positive output OUT+. The output voltage of the H-bridge corresponds to the difference of potential difference the positive output OUT+ and the negative output OUT−.
In the example described, branches B1 and B2 are connected between the negative terminal of the first cell C1 and the positive terminal of the nth cell Cn. More precisely, the negative terminal of the first cell C1 is connected to the first switch SWH1 and to the second switch SWH2 whereas the positive terminal of the nth cell Cn is connected to the third switch SWH3 and to the fourth switch SWH4.
According to the representation chosen in
The H-bridge is used to generate positive and negative sign voltages, according to the configuration of the switches of the H-bridge, as will be described with reference to
In the example shown in
In the case of
In the case of
Each module M further includes two control circuits 16 and 18.
The first control circuit 16 is configured to connect the positive pole of the first cell C1 to the positive pole DC+ of the power supply system 10 whereas the second control circuit 18 is configured to connect the negative pole of the nth cell Cn to the negative pole DC− of the power system 10.
In the example described, each control circuit 16 or 18 corresponds to a switch, a first control switch SWDC1 for the first control circuit 16 and a second control switch SWDC2 for the second control circuit 18, respectively.
Thereby, the first cell C1 is connected between the bottom of the H-bridge and the first control switch SWDC1.
The nth cell Cn is connected between the top of the H-bridge and the second control switch SWDC2.
The closing of the control switches SWDC1 and SWDC2 connects the potential DCOUT1 and DCOUT2 to the positive pole of the first cell C1 and to the negative pole of the nth cell Cn, respectively.
From the point of view of the DC+ and DC− outputs of the power supply system 10, good synchronization should be provided between the switches SWH1, SWH2, SWH3 and SWH4 of the H-bridge and the control switches SWDC1 and SWDC2.
More particularly, when the H-bridge is in the positive configuration (with the switches SWH1 and SWH4 closed) thereof, it is recommended to close the first control switch SWDC1 at the same time and when the H-bridge is in the negative configuration (with the switches SWH2 and SWH3 closed) thereof, it is recommended to close at the same time the second control switch SWD2, as can be seen in
As an example, to provide good synchronization, it may be envisaged to simultaneously control a control switch SWDC1 and SWDC2 with one of the switches SWH1, SWH2, SWH3 and SWH4 of the H-bridge. Thereby, the control switches SWDC1 and SWH1 can be controlled by the same signal and similarly, the switches SWDC2 and SWH3 can be controlled by the same signal.
To this end, the modules M are equipped with a control unit which is suitable for sending control laws adapted to the selection circuit 12 and to the polarity switchover circuit 14 and thereby to control all the switches SW.
Each module M includes, in addition to the positive output OUT+ and to the negative output OUT−, two DC outputs, which will be referred to hereinafter as positive pole DCOUT_1 and negative pole DCOUT_2.
With reference to
In fact, the three negative outputs OUT− of the three modules M1, M2 and M3 are connected together to form the neutral point PN of the power supply system 10.
The three phases P1, P2 and P3 form the three-phase output of the power supply system 10.
The three positive poles DCOUT_1 of the three modules M1, M2 and M3 are connected together to form the positive pole DC+ of the power supply system 10.
The three negative poles DCOUT_2 of the three modules M1, M2 and M3 are also connected together to form the negative pole DC− of the power supply system 10.
A DC voltage is thereby obtained between the two poles DC+ and DC− of the DC output of the power supply system 10 from the three DC outputs DCOUT_1 and DCOUT_2 of the three modules M1, M2 and M3.
It will now be explained why such an arrangement makes it possible to guarantee that the power supply system 10 can supply both a direct voltage and a polyphase voltage in all cases of use.
It should be noted that, in a three-phase system, the output voltages are centered at 0 V and at each instant, at least 2 of the 3 phases are of opposite sign. When one phase changes sign (from positive to negative voltage, or vice versa), the other two phases have an opposite sign, so there will always be two phases of opposite sign, among the three.
The above remains true even with discretized signals and even if a harmonic (e.g. of order 3, i.e. a signal of the form A.Sin (ωt)+B.Sin (3ωt)) is added.
As a result, the H-bridge always sees two phases of opposite sign, in any configuration (positive and negative). The above makes it possible to generate a DC voltage at the output of the power supply system 10 (in addition to the three-phase voltage).
In the present example, the two modules M1 and M2 positioned at the top (first and second modules in the following sequence) generate a negative voltage at the output of the H-bridge (between P1 and PN and between P2 and PN) thereof and the module M3 positioned at the bottom (third module hereinafter) generates a positive voltage at the output of the H-bridge (between P3 and PN).
The negative poles of the two nth cells Cn,1 and Cn,2 of the first and second modules M1 and M2 are connected to the negative pole DC− of the power supply system 10, the control switches SWDC2,1 and SWDC2,2 being in the closed state.
The positive poles of the two n-th cells Cn,1 and Cn,2 of the first and second modules M1 and M2 are connected to the neutral point PN, the switches SWH3,1 and SWH3,2 being in the closed state.
Thereby, the two nth cells Cn,1 and Cn,2 of the first and second modules M1 and M2 are connected in parallel with each other.
The positive pole of the first cell C13 of the third module M3 is connected to the positive pole DC+ of the power supply system 10, the control switch SWDC1,3 being in the closed state.
The negative pole of the first cell C1,3 of the third module M3 is connected to the neutral point PN, the switch SWH1,3 being in the closed state.
Thereby, the first cell C13 of the third module M3 is connected in series to the two nth cells Cn,1 and Cn2 of the first and second modules M1 and M2 and to the two poles DC− and DC+ of the power supply system 10, a voltage equivalent to two cells connected in series (C1+Cn) is present.
Such a configuration serves to continually obtain a continuous voltage.
Indeed, even if the configuration of the three-phase signal changes, with e.g. a first module with a positive output voltage and the other two modules with a negative output voltage, there are always two modules with opposite output voltage and hence the first cell C1 of a module in series with the nth cell Cn of another module. The sum of the voltage thereof is thereby continually available on the two poles DC− and DC+ of the power supply system 10.
Furthermore, when the first cells C1 of the three modules M1, M2 and M3 have the same voltage and the n-th cells Cn of the three modules M1, M2 and M3 have the same voltage, the DC voltage at the output of the power supply system 10 has very small variations when the configuration of the three-phase signal is changed. It is thereby favorable that each of the three modules M1, M2 and M3 are identical, which is the case for
The power supply system 10 is also configured to deliver a DC voltage when the three-phase output of the power system is zero. The above point now be explained with reference to
It should first be noted that a discretized voltage, leaving an inverter, is often modulated in order to improve the performance and the quality of the current exchanged (e.g. with an electric motor).
When modulation is made between zero and the first (or the only) stage of the inverter (with modulation between zero and one cell, in the present case), the voltage can be at zero a plurality of times during the electrical period.
For the case shown in
In order to ensure the generation of the DC voltage even in such case, a specific H-bridge configuration is used, depending on whether the system is in the first or in the second half of the electrical period of the modulated voltage.
In order to ensure the generation of the DC voltage, the zeros of the first half of the voltage period will be generated by closing the bottom switches SWH1, SWH2 of the H-bridge and at the same time the first control switch SWDC1 (which was already closed during the generation of the positive plateau preceding the zero). Such configuration, called “zero plus”, allows the first cell C1 to be connected between the positive pole DC+ and the neutral point PN of the power supply system 10, as for the generation of a positive voltage.
Similarly, the zeros of the second half of the voltage period will be generated by closing the top switches SWH3, SWH4 of the H-bridge and at the same time the second control switch SWDC2 (which was already closed during the generation of the negative plateau preceding the zero). Such configuration, called “zero minus”, makes it possible to connect the n-th cell Cn between the negative pole DC− and the neutral point PN of the power supply system 10, as for the generation of a positive voltage.
In this way, at least a first cell C1 of a module M is always connected between the positive pole DC+ and the neutral point PN of the power supply system 10 (with the generation of a positive voltage or a “zero plus” at the output of the H-bridge of the corresponding module M), and an n-th cell Cn, connected between the negative pole of the DC+ output and the neutral point PN of the power supply system 10 (with the generation of a negative voltage or “zero minus” at the output of the H-bridge of the corresponding module). The two cells are in series and the sum of the voltage (C1+Cn) thereof is present on the DC output of the power supply system 10.
It is thereby possible to generate the DC voltage for the power supply system 10, even when the three-phase output of the power supply system 10 is zero (e.g. if the electric motor is stopped). Indeed, if each M module generates a periodic series of configurations (which can be stored in memory), where the first half of the period is composed of “zero plus” configurations and the second half of the period is composed of “zero minus” configurations, and the series generated by the 3 modules M1, M2 and M3 are phase shifted by one third of the period or by π/3 (as for the generation of a three-phase voltage), there will always be at least one module M that generates a “zero plus” and at least one module M that generates a “zero minus”.
It has thereby been shown that the power supply system 10 described can supply both a direct voltage and a polyphase voltage in all use cases.
More generally,
Thereby, the generation of a phase by modules M1, M2, M3 should be understood either as the supply of a phase or as a contribution to the supply of a phase. In other words, the modules M1, M2 and M3 allow the generation of a phase in the sense that each of the modules serves to generate a phase alone or in combination with other modules, e.g. in the context of a sub-pack SP as shown in
Furthermore, the power supply system 10 is easy to implement (smaller bulk and relatively low cost) compared to a system involving switched-mode power supplies.
The supply system 10 may correspond to any combination of the preceding embodiments, more particularly, each module may be the module shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| FR2114417 | Dec 2021 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/087331 | 12/21/2022 | WO |
