Method and device for controlling the transfer of electrical energy between a first three-phase electrical network without neutral and a second three-phase electrical network with neutral

Abstract

The first electrical network is a balanced three-phase load and, when the first electrical network transfers electrical energy to the second electrical network, the first electrical network is a voltage source that has to adapt to the requirements of the loads of the second electrical network R2AC. When the second electrical network receives electrical energy from the first electrical network, the electrical network may potentially be subject to a load imbalance but its voltages are balanced. When the second electrical network supplies electrical energy to the first electrical network, the second electrical network may be subject to a voltage imbalance and have a phase displacement, the two electrical networks being connected via a delta-Y transformer. The method comprises the following steps: - obtaining information representative of a transfer of electrical energy from the first electrical network to the second electrical network or of a transfer of electrical energy from the second electrical network to the first electrical network, - commanding a switch so as to connect a common point of the delta-Y transformer to a neutral of the second electrical network if the second electrical network is to supply electrical energy to the first electrical network, - commanding the switch so as not to connect the common point of the delta-Y transformer to the neutral of the second electrical network if the first electrical network is to supply electrical energy to the second electrical network. 6a

Description

[0001] METHOD AND DEVICE FOR CONTROLLING THE TRANSFER OF ELECTRICAL ENERGY BETWEEN A FIRST THREE-PHASE ELECTRICAL NETWORK WITHOUT A NEUTRAL AND A SECOND THREE-PHASE ELECTRICAL NETWORK WITH A NEUTRAL

[0002] TECHNICAL FIELD

[0003] The present invention relates to a method and device for controlling the transfer of electrical energy between a first three-phase electrical network without neutral and a second three-phase electrical network with neutral.

[0004] STATE OF PRIOR ART

[0005] In some equipment, different electrical power supply networks coexist, such as in aircraft.

[0006] These networks are, for example, three-phase networks without a neutral and three-phase networks with a neutral.

[0007] It is very interesting to be able to allow these different networks to transfer electrical energy, for example from a three-phase network without a neutral to a three-phase network with a neutral.

[0008] The three-phase network without neutral is, as a load, a balanced three-phase load and must, as a source of electrical energy supply, adapt to the needs of the loads of the three-phase network with neutral.

[0009] As a load, the three-phase network with neutral is a potentially unbalanced network in terms of load but whose voltages are necessarily balanced, the imbalance being carried by the current.

[0010] As a source of electrical power, a three-phase network with a neutral conductor can experience voltage imbalances and phase shifts. These imbalances are acceptable to a three-phase network without a neutral conductor as a load.

[0011] By using a delta transformer at the three-phase network without neutral and a star transformer with neutral at the three-phase network with neutral, it is possible to create a local neutral.

[0012] In this way, during the transfer of energy from the three-phase network without neutral to the three-phase network with neutral, the three-phase network without neutral as the source and the three-phase network with neutral as the load will be balanced in voltages and the imbalance of loads in the three-phase network with neutral will result in a current imbalance so that the zero-sequence component can flow in the neutral of the transformer.

[0013] Delta connection is justified for the primary side to reduce the current seen by the transformer in relation to the application's constraints. During energy transfer from a three-phase network with a neutral to a three-phase network without a neutral, if the three-phase network with a neutral has a slight voltage imbalance or a phase shift, a high neutral current results in a significant current imbalance in the three-phase network with a neutral, which is unacceptable.

[0014] It is therefore desirable to find a solution that avoids such imbalances during transfers of electrical energy between a three-phase network without a neutral and a three-phase network with a neutral and vice versa.

[0015] DESCRIPTION OF THE INVENTION

[0016] The present invention aims to ensure that electrical energy transfers between a three-phase network without a neutral and a three-phase network with a neutral are free from such imbalances.

[0017] According to a first aspect of the invention, the invention relates to a method for controlling the transfer of electrical energy between a first three-phase electrical network without a neutral and a second three-phase electrical network with a neutral, when the first electrical network receives electrical energy from the second electrical network, the first electrical network is a balanced three-phase load and when the first electrical network transfers electrical energy to the second electrical network, the first electrical network is a voltage source that must adapt to the needs of the loads of the second electrical network, when the second electrical network receives electrical energy from the first electrical network, the electrical network being potentially unbalanced in load and whose voltages are balanced, when the second electrical network supplies electrical energy to the first electrical network.the second electrical network may be unbalanced in voltage and have a phase shift, the two electrical networks being connected via a delta Y transformer, characterized in that the process comprises the steps of:,

[0018] - obtaining information representative of a transfer of electrical energy from the first electrical network to the second electrical network or of a transfer of electrical energy from the second electrical network to the first electrical network, - control of a switch to connect a common point of the delta Y transformer to a neutral of the second electrical network if the second electrical network is to supply electrical energy to the first electrical network,

[0019] - control of the switch so as not to connect the common point of the delta Y transformer to the neutral of the second electrical network if the first electrical network is to supply electrical energy to the second electrical network.

[0020] Correspondingly, the invention relates to a device for controlling the transfer of electrical energy between a first electrical network without a neutral and a second electrical network with a neutral. When the first electrical network receives electrical energy from the second electrical network, the first electrical network is a balanced three-phase load. When the first electrical network transfers electrical energy to the second electrical network, the first electrical network is a voltage source that must adapt to the needs of the loads of the second electrical network. When the second electrical network receives electrical energy from the first electrical network, the electrical network is potentially unbalanced in load and has balanced voltages. When the second electrical network supplies electrical energy to the first electrical network, the second electrical network may be unbalanced in voltage and have a phase shift.the two electrical networks being connected via a delta Y transformer, characterized in that the device comprises:

[0021] - means of obtaining information representative of a transfer of electrical energy from the first electrical network to the second electrical network or of a transfer of electrical energy from the second electrical network to the first electrical network,

[0022] - means for controlling a switch to connect a common point of the delta Y transformer to a neutral of the second electrical network if the second electrical network is to supply electrical energy to the first electrical network,

[0023] - means of controlling the switch so as not to connect the common point of the delta Y transformer to the neutral of the second electrical network if the first electrical network has to supply electrical energy to the second electrical network.

[0024] Thus, the present invention enables electrical energy transfers between a three-phase network without a neutral and a three-phase network with a neutral to be free of such imbalances. According to another aspect of the invention, representative information is obtained from the direction of a current flowing in the transformer (ΔY) or from voltage measurements.

[0025] According to another aspect of the invention, representative information is obtained by a controller upon request from a remote device.

[0026] According to another aspect of the invention, representative information is obtained from a remote device which indicates whether the transfer of electrical energy is from the first electrical network to the second electrical network or whether the transfer of electrical energy is from the second electrical network to the first electrical network.

[0027] A computer program is also proposed, which can be stored on a medium and / or downloaded from a communication network, for reading by a processor. This computer program includes instructions for implementing the process, as mentioned above, when said program is executed by the processor. The invention also relates to an information storage medium for storing such a computer program.

[0028] BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The features of the invention mentioned above, as well as others, will become clearer upon reading the following description of an exemplary embodiment, said description being made in relation to the accompanying drawings, among which:

[0030] [Fig. la] represents a first example of two electrical networks capable of transferring electrical energy bidirectionally;

[0031] [Fig. 1b] represents a second example of two electrical networks capable of transferring electrical energy bidirectionally;

[0032] [Fig. 2] represents an example of the architecture of a transformer used in the present invention;

[0033] [Fig. 3] represents a block diagram of a controller used in the present invention;

[0034] [Fig. 4] represents an equivalent diagram of the transformer when the three-phase network with neutral supplies electrical energy to the three-phase network without neutral when the star part of the transformer is connected to the neutral; [Fig. 5] represents an equivalent diagram of the transformer when the three-phase network with neutral supplies electrical energy to the three-phase network without neutral when the star part of the transformer is not connected to the neutral;

[0035] [Fig. 6a] represents a first example of an algorithm executed by the controller according to the present invention;

[0036] [Fig. 6b] represents a second example of an algorithm executed by the controller according to the present invention;

[0037] [Fig. 6c] represents a third example of an algorithm executed by the controller according to the present invention.

[0038] DETAILED DESCRIPTION OF IMPLEMENTATION METHODS

[0039] Fig. 1a represents a first example of two electrical networks capable of transferring electrical energy bidirectionally.

[0040] Here we mean by bidirectional transfer the transfer of electrical energy from the three-phase network without neutral to the three-phase network with neutral or the transfer of electrical energy from the three-phase network with neutral to the three-phase network without neutral.

[0041] Fig. 1a includes an electrical RIDC network, an electrical RIAC network and an electrical R2AC network.

[0042] The RIDC electrical network is a DC continuous electrical network, the RIAC electrical network is an AC alternating network and the R2AC electrical network is an AC alternating network.

[0043] The RIAC and R2AC electrical power networks are characterized as follows: As a load, the RIAC electrical network is a balanced three-phase load and as a source, the RIAC electrical network is a voltage source that must adapt to the needs of the loads of the R2AC electrical network.

[0044] As a load, the R2AC electrical network is potentially unbalanced in load but whose voltages are necessarily balanced (imbalance carried by the current), and as a source, the R2AC electrical network can be unbalanced in voltage and have a phase shift. These imbalances are acceptable from the perspective of the RIAC electrical network.

[0045] A set of 110A batteries, a DC voltage source 11La, and DC power-consuming elements 112A are connected to the RI DC electrical network. A 120A device for converting the DC energy from the RIDC network into AC energy for the RIAC network is associated with the RIDC electrical network.

[0046] The 120a device for transforming direct current energy into alternating current energy consists of power switches and filters.

[0047] According to the example in Fig. 1a, the device 120a for converting direct energy into alternating energy includes a controller which is capable of controlling a switch according to the present invention.

[0048] An AC voltage source 130a and AC energy-consuming elements 131a are connected to the R2 AC electrical network.

[0049] The RIAC and R2 AC power supply networks are interconnected by a delta-star transformer AY 150.

[0050] The AY 150 delta-star transformer consists of a part connected in delta and a part connected in star.

[0051] In a star connection, each phase winding of the 150 three-phase transformer is connected to a common point, which may or may not be connected to neutral. The other end is connected to the corresponding line terminal. The voltage across the coils is the phase-to-phase voltage divided by 3. The current flowing through the coils is the line current. The star connection is represented by the letter Y.

[0052] In a delta connection, the phase windings of a three-phase transformer are connected to form a closed circuit. The voltage across the coils is the phase-to-phase voltage. The current flowing through the coils is the line current divided by 3. The delta connection is represented by the letter D or A. It cannot be connected to neutral or ground.

[0053] According to another provision, the RIAC and R2 AC power supply networks can be interconnected by a delta Z transformer.

[0054] According to the invention, the common point of the star connection is connected to a switch 100 which is controlled to put or not put the common point to neutral.

[0055] Thus, when electrical energy is transferred from the RIAC network to the R2AC network, connecting the star-connected portion to the neutral ensures balanced voltages despite potential load imbalances. Connecting the star-connected portion to the neutral resolves the issue of energy transfer from the R2AC network to the RIAC network when R2AC is a network with a voltage or phase imbalance. Fig. 1b shows a second example of two electrical supply networks capable of bidirectional energy transfer. As mentioned previously, bidirectional transfer is the transfer of electrical energy from a three-phase network without a neutral to a three-phase network with a neutral, or vice versa. Fig. 1b shows an electrical network RlbAc ​​and a second electrical network R2bAc.The RlbAc ​​electrical network is an AC alternative electrical network and the R2bAc electrical network is an AC alternative electrical network.

[0056] An AC voltage source 111b and AC energy-consuming elements 112b (such as: a diode bridge, an asynchronous machine, etc.) are connected to the RlbAc ​​electrical network.

[0057] An AC voltage source 130b and AC energy-consuming elements 131b are connected to the R2bAc electrical network.

[0058] The RIAC and R2 AC power supply networks are interconnected by a delta-star transformer AY 150.

[0059] According to the invention, the common point of the star connection is connected to a switch 100 which is controlled by a Cont controller to either connect or disconnect the common point to neutral. The Cont controller is, for example, a dedicated device or is integrated into an aircraft control system.

[0060] Thus, when electrical energy is transferred from network R10AC to network R20AC, connecting the star-connected portion to the neutral ensures balanced voltages despite potential load imbalances. Connecting the star-connected portion to the neutral also resolves the issue of energy transfer from network R2bAc to network RlbAc ​​when R2bAc is a network with a voltage or phase imbalance.

[0061] Fig. 2 represents an example of the architecture of a transformer used in the present invention.

[0062] The AY 150 delta-star transformer consists of a part connected in delta TR and a part connected in star ET.

[0063] In a star connection, each phase winding S23, S24, and S25 of the 150 three-phase transformer is connected to a common point Co, which may or may not be connected to neutral. The other end is connected to the corresponding line terminal of the R2AC network. The voltage across the coils S23, S24, and S25 is the phase-to-phase voltage divided by 3. The current flowing through the coils is the line current.

[0064] In the delta TR connection, the phase windings S20, S21, and S22 of a three-phase transformer are connected to form a closed circuit. The voltage across the coils is the phase-to-phase voltage. The current flowing through the coils is the line current divided by 3.

[0065] According to the invention, the common point of the star connection is connected to a switch 100 which is controlled to put or not put the common point to neutral.

[0066] Windings S20, S21, S22, S23 and S25 are wound around an EM magnetic element.

[0067] Fig. 3 represents a block diagram of a Cont controller according to the present invention.

[0068] The Cont controller is adapted to perform, from one or more software modules, the steps of the algorithm as described with reference to Fig. 6a or 6b or 6c.

[0069] The Cont controller includes a communication bus 301 to which are connected a processor Proc 300, a non-volatile memory ROM 302, a random access memory RAM 303, a control interface 306 allowing control of the Cont switch.

[0070] The non-volatile memory 302 stores the software module(s) implementing the invention, as well as the data enabling the implementation of the algorithm as described with reference to Fig. 6a, 6b or 6c.

[0071] More generally, the programs according to the present invention are stored in a storage medium. This storage medium is readable by the microprocessor 300. This storage medium may or may not be integrated into the controller Cont, and may be removable.

[0072] When the Cont controller is powered on, the software module(s) according to the present invention is or are transferred into RAM 303 which then contains the executable code according to the present invention as well as the data necessary for the implementation of the invention.

[0073] Thus, all or part of the algorithm and steps described here can be implemented in software form by executing a set of instructions using a programmable machine, such as a DSP (Digital Signal Processor), a microcontroller, or a processor. All or part of the algorithm and steps described here can also be implemented in hardware form by a machine or component (a "chip"), such as an FPGA (Field-Programmable Gate Array) or an ASIC (Application-Specific Integrated Circuit). Therefore, the Cont controller includes electronic circuitry adapted and configured to implement the behaviors, algorithms, and steps described here.

[0074] Fig. 4 represents an equivalent diagram of the transformer when the three-phase network with neutral supplies electrical power to the three-phase network without neutral when the star part of the transformer is connected to the neutral N.

[0075] At the RIAC network level, the delta connection of the transformer imposes the following relationship on the voltages: V SA + F SB + V sc = 0

[0076] By construction: V PA + V PB + V PC = 0

[0077] By adding the equations for the 3 phases, we obtain the following relationship: V a + V b + V c = (R e + L e . s)(J a + I b + / c )

[0078] If we denote Vn as the sum of the three voltages and In as the sum of the three currents, we then obtain

[0079] With Re and Le being the leakage impedance in the star connection of the transformer. Thus, despite a small voltage imbalance or a small phase shift, the current in the neutral and the imbalance are higher when the leakage impedance of the transformer is low.

[0080] This current In is expressed on each phase as a zero-sequence current component. Specifically, when the current draw on the RIAC is zero, the current on each phase is:

[0081] The system therefore constantly consumes a high phase current.

[0082] Fig. 5 represents an equivalent diagram of the transformer when the three-phase network with neutral supplies electrical power to the three-phase network without neutral when the star part of the transformer is not connected to the neutral.

[0083] By adding the previous equations, we obtain:

[0084] V a + V b + V C = V N = 3.V E

[0085] Furthermore, and advantageously, since the sum of the three currents is zero, the current on each phase can only contain a symmetrical positive and negative component, but no zero-sequence component. Thus, the amplitude of the current on each phase depends only on the power consumption on the RIAC network.

[0086] Fig. 6a represents a first example of an algorithm executed by the controller according to the present invention.

[0087] At step E600, the Cont controller is in a wait-for-receipt mode for an E601 request from an external device, for example a device located in the aircraft cockpit, to trigger the execution of this algorithm.

[0088] Until a request to trigger the execution of this algorithm is received, the Cont controller remains at step E600.

[0089] Upon receiving the trigger request, the Cont controller checks at step E602 whether the electrical network RIAC OR RIÔAC should supply electrical energy to the network R2AC OR R2ÔAC and checks at step E606 whether the electrical network R2AC OR RZÔAC should supply electrical energy to the network RIAC OR RlbAc.

[0090] The verification is carried out for example by measuring the direction of the DC current or the power at the output of transformer 150, through a voltage and current measurement or other means.

[0091] If the RIAC or RlbAc ​​electrical network is to supply electrical energy to the R2AC or R2bAc network, the Cont controller commands E603 the opening of switch 100, notifies E604 the external device that switch 100 is closed, switches to mode E605 in which the RIAC or R2bAc network supplies electrical energy to the R2AC or R2bAc network and checks in step E606 whether the R2AC or R2bAc electrical network is to supply electrical energy to the RIAC or R2bAc network.

[0092] If the R2AC OR R20AC electrical network is to supply electrical energy to the RIAC or RIÔAC network, the Cont controller commands E607 the closing of switch 100, notifies E608 the external device that switch 100 is open, switches to mode E609 in which the RIAC OR RlbAc ​​network supplies electrical energy to the R2AC OR R2bAc network and checks at step E602 whether the R2AC OR R2bAc electrical network is to supply electrical energy to the RIAC OR RlbAc ​​network.

[0093] Fig. 6b represents a second example of an algorithm executed by the controller according to the present invention.

[0094] At step E620, the Cont controller initializes this algorithm and then proceeds to step E622 to check if the electrical network RIAC OR RIÔAC should supply electrical energy to the network R2AC OR R2ÔAC and to step E626 to check if the electrical network R2AC OR R2ÔAC should supply electrical energy to the network RIAC OR RIÔAC.

[0095] The verification is carried out for example by measuring the direction of the DC current or the power at the output of transformer 150, through a voltage and current measurement or other means.

[0096] If the RIAC or RIÔAC electrical network is to supply electrical energy to the R2AC or R2ÔAC network, the Cont controller commands E623 the opening of switch 100, notifies E624 the external device that switch 100 is closed, switches to mode E625 in which the RIAC or RIÔAC network supplies electrical energy to the R2AC or R2ÔAC network and proceeds to step E626.

[0097] If the R2AC or R2ÔAC electrical network supplies electrical energy to the RIAC or RIÔAC network, the Cont controller commands E627 the closing of switch 100, notifies E628 the external device that switch 100 is open, switches to mode E629 in which the RIAC or RIÔAC network supplies electrical energy to the R2AC or R2ÔAC network and proceeds to step E622.

[0098] Fig. 6c represents a third example of an algorithm executed by the controller according to the present invention.

[0099] At step E640, the Cont controller initializes this algorithm and then proceeds to step E642 to check if a request is received from an external device, for example from a device located in the aircraft cockpit, to switch to an operating mode in which the R2AC OR R2ÔAC electrical network must supply electrical energy to the RIAC OR RIÔAC network OR switch to an operating mode in which the RIAC OR RIÔAC electrical network must supply electrical energy to the R2AC OR R2bAc network.If a request is received to switch to an operating mode in the electrical network R2AC OR R2ÔAC is to supply electrical energy to the network RIAC OR R10AC, the controller Cont commands E643 the closing of switch 100, notifies E644 the external device that switch 100 is closed, switches to mode E645 in which the network RIAC OR RlbAc ​​supplies electrical energy to the network R2AC OR R2b\c and checks at step E646 if a request is received to switch to an operating mode in which the electrical network RIAC OR R10AC is to supply electrical energy to the network R2AC OR R2b\c.

[0100] If a request is received to switch to an operating mode in the electrical network RIAC OR RlbAc ​​must supply electrical energy to the electrical network R2AC OR R2bAc, the controller Cont commands E647 the opening of switch 100, notifies E648 the external device that switch 100 is open, switches to the mode E649 in which the RIAC OR RIÔAC network supplies electrical energy to the R2AC OR R2b\c network, checks E642 if a request is received to switch to an operating mode in the electrical network R2AC OR R2b\c must supply electrical energy to the RIAC OR RIÔAC network.

Claims

DEMANDS 1. A method for controlling the transfer of electrical energy between a first electrical network without a neutral and a second electrical network with a neutral, wherein, when the first electrical network receives electrical energy from the second electrical network, the first electrical network is a balanced three-phase load; and when the first electrical network transfers electrical energy to the second electrical network, the first electrical network is a voltage source that must adapt to the needs of the loads of the second electrical network. When the second electrical network receives electrical energy from the first electrical network, the electrical network is potentially unbalanced in load and has balanced voltages; when the second electrical network supplies electrical energy to the first electrical network, the second electrical network may be unbalanced in voltage and have a phase shift.the two electrical networks being connected via a delta Y transformer, characterized in that the process comprises the steps of: - obtaining information representative of a transfer of electrical energy from the first electrical network to the second electrical network or of a transfer of electrical energy from the second electrical network to the first electrical network, - control of a switch to connect a common point of the delta Y transformer to a neutral of the second electrical network if the second electrical network is to supply electrical energy to the first electrical network, - control of the switch so as not to connect the common point of the delta Y transformer to the neutral of the second electrical network if the first electrical network is to supply electrical energy to the second electrical network.

2. Method according to claim 1, characterized in that the representative information allows the direction of power to be calculated from the voltages and current flowing in the transformer delta Y.

3. A method according to claim 1 or 2, characterized in that representative information is obtained by a controller upon request from a remote device.

4. Method according to claim 1, characterized in that representative information is obtained from a remote device which indicates whether the transfer of electrical energy is from the first electrical network to the second electrical network or whether the transfer of electrical energy is from the second electrical network to the first electrical network.

5. Device for controlling the transfer of electrical energy between a first electrical network without a neutral and a second electrical network with a neutral, in which, when the first electrical network receives electrical energy from the second electrical network, the first electrical network is a balanced three-phase load, and when the first electrical network transfers electrical energy to the second electrical network, the first electrical network is a voltage source that must adapt to the needs of the loads of the second electrical network. When the second electrical network receives electrical energy from the first electrical network, the electrical network is potentially unbalanced in load and whose voltages are balanced. When the second electrical network supplies electrical energy to the first electrical network, the second electrical network may be unbalanced in voltage and have a phase shift.the two electrical networks being connected via a delta Y transformer, characterized in that the device comprises: - means of obtaining information representative of a transfer of electrical energy from the first electrical network to the second electrical network or of a transfer of electrical energy from the second electrical network to the first electrical network, - means for controlling a switch to connect a common point of the delta Y transformer to a neutral of the second electrical network if the second electrical network is to supply electrical energy to the first electrical network, - means of controlling the switch so as not to connect the common point of the delta Y transformer to the neutral of the second electrical network if the first electrical network has to supply electrical energy to the second electrical network.

6. A computer program comprising instructions for implementing, by a processor, the method according to any one of claims 1 to 4, when said program is executed by said processor.

7. An information storage medium storing a computer program comprising instructions for implementing, by a processor, the method according to any one of claims 1 to 4, when said program is read and executed by said processor.

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