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
The method and device using a delta-Y transformer with a controlled switch address voltage and phase shift issues in three-phase networks, ensuring balanced energy transfer and minimizing current imbalances.
Patent Information
- Authority / Receiving Office
- FR · FR
- Patent Type
- Applications
- Current Assignee / Owner
- SAFRAN ELECTRICAL & POWER CHATOU SAS
- Filing Date
- 2024-12-20
- Publication Date
- 2026-06-26
Abstract
Description
Title of the invention: 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. Technical field
[0001] 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. STATE OF PRIOR ART
[0002] In some equipment, different electrical power supply networks coexist, as for example in aircraft.
[0003] These networks are, for example, three-phase networks without neutral and three-phase networks with neutral.
[0004] 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.
[0005] 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.
[0006] 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.
[0007] As a source of electrical power supply, the three-phase network with a neutral can be voltage unbalanced and have a phase shift. These imbalances are acceptable to the three-phase network without a neutral as a load.
[0008] 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.
[0009] 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 the loads of 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.
[0010] Delta connection is justified for the primary side in order to reduce the current seen by the transformer with respect to the application constraints. During energy transfer from the three-phase network with neutral to the three-phase network without neutral, if the three-phase network with neutral has a slight voltage imbalance or a phase shift, a strong neutral current results in a strong current imbalance which appears at the level of the three-phase network with neutral which is not acceptable.
[0011] It is therefore desirable to find a solution which avoids such imbalances during transfers of electrical energy between a three-phase network without neutral and a three-phase network with neutral and vice versa. Description of the invention
[0012] 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.
[0013] 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: ,
[0014] - obtaining information representative of an electrical energy transfer from first electrical network to the second electrical network or a transfer of electrical energy from the second electrical network to the first electrical network,
[0015] - control of a switch to connect a common point of the delta transformer There is a neutral connection for the second electrical network if the second electrical network is to supply electrical energy to the first electrical network.
[0016] - control of the switch so as not to connect the common point of the transformer delta Y at the neutral of the second electrical network if the first electrical network is to supply electrical energy to the second electrical network.
[0017] 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 In 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 acts as a voltage source that must adapt to the needs of the loads in the second electrical network. When the second electrical network receives electrical energy from the first electrical network, the second 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 are connected via a delta Y transformer, characterized in that the device comprises:
[0018] - means of obtaining information representative of an energy transfer electrical energy from the first electrical network to the second electrical network, or a transfer of electrical energy from the second electrical network to the first electrical network,
[0019] - means for controlling a switch to connect a common point of the A delta Y transformer is connected to a neutral point of the second electrical network if the second electrical network is to supply electrical energy to the first electrical network.
[0020] - means for controlling the switch so as not to connect the common point from 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.
[0021] Thus, the present invention makes it possible for 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.
[0022] According to another aspect of the invention, representative information is obtained from the direction of a current flowing in the transformer delta Y or from voltage measurements.
[0023] According to another aspect of the invention, representative information is obtained by a controller on request from a remote device.
[0024] 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.
[0025] A computer program is also proposed, which can be stored on a medium and / or downloaded from a communication network, in order to be read 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 storing such a computer program. Brief description of the drawings
[0026] 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:
[0027] [Fig. la] represents a first example of two electrical networks capable of transferring electrical energy bidirectionally;
[0028] [Fig. 1b] represents a second example of two electrical networks capable of transferring electrical energy bidirectionally;
[0029] [Fig.2] represents an example of the architecture of a transformer used in the present invention;
[0030] [Fig.3] represents a block diagram of a controller used in the present invention;
[0031] [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;
[0032] [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;
[0033] [Fig.6a] represents a first example of an algorithm executed by the controller according to the present invention;
[0034] [Fig.6b] represents a second example of an algorithm executed by the controller according to the present invention;
[0035] [Fig.6c] represents a third example of an algorithm executed by the controller according to the present invention.
[0036] DETAILED DESCRIPTION OF IMPROVEMENTS
[0037] Fig. 1a represents a first example of two electrical networks capable of to transfer electrical energy bidirectionally.
[0038] 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.
[0039] The [Fig. 1a] comprises an electrical network RlDc, an electrical network RlAc and a R2AC electrical network.
[0040] The electrical network RlDc is a DC electrical network, the electrical network R1ac is an AC electrical network and the electrical network R2AC is an AC electrical network.
[0041] The electrical power networks R1AC and R2AC are characterized as follows:
[0042] As a load, the R1AC electrical network is a balanced three-phase load and as a source, the R1AC electrical network is a voltage source that must adapt to the needs of the loads of the R2AC electrical network.
[0043] 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 point of view of the R1AC electrical network.
[0044] A set of batteries 110a, a DC voltage source 11 la and DC energy-consuming elements 112a are connected to the electrical network R1DC.
[0045] Associated with the electrical network RlDc is a device 120a for transforming the direct energy of the network RlDc into alternating energy in the network R1AC.
[0046] The device 120a for transforming direct energy into alternating energy consists of power switches and filters.
[0047] According to the example in [Fig.la], the device 120a for transforming direct energy into alternating energy comprises a controller which is capable of controlling a switch according to the present invention.
[0048] An alternating voltage source 130a and alternating energy consuming elements 131a are connected to the electrical network R2AC.
[0049] The electrical power supply networks R1AC and R2AC 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 the star connection, each phase winding of the three-phase transformer 150 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 . 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 in such a way as 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 ■. The delta connection is represented by the letter D or A. It cannot be connected to neutral or earth.
[0053] According to another provision, the electrical power supply networks RlAc and R2Ac 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 network R1AC to network R2AC, 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 problem of energy transfer from network R2AC to network R1AC when R2AC is a network with a voltage or phase imbalance.
[0056] Fig. 1b represents a second example of two electrical power supply networks capable of transferring electrical energy bidirectionally.
[0057] As mentioned previously, a bidirectional transfer is a transfer of electrical energy from the three-phase network without neutral to the three-phase network with neutral or a transfer of electrical energy from the three-phase network with neutral to the three-phase network without neutral.
[0058] Fig. 1b comprises an electrical network R1bAC and a second electrical network R2b AC-
[0059] The RlbAC electrical network is an AC alternating electrical network and the R2bAC electrical network is an AC alternating electrical network.
[0060] An alternating voltage source 111b and alternating energy-consuming elements 112b (such as: a diode bridge, an asynchronous machine, etc.) are connected to the RlbAC electrical network.
[0061] An alternating voltage source 130b and alternating energy-consuming elements 131b are connected to the electrical network R2bAC.
[0062] The electrical power supply networks R1AC and R2AC are interconnected by a delta-star transformer AY 150.
[0063] 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 put or not the common point to neutral.
[0064] The Cont controller is for example a dedicated device or is integrated into an aircraft control system.
[0065] Thus, when electrical energy is transferred from the RlbAC network to the R2bAC network, the connection to neutral of the star-connected portion ensures balanced voltages despite the potential load imbalance. The connection to neutral of the star-connected portion resolves the problem of energy transfer from the R2bAC network to the RlbAC network in the case where R2bAC is a network with a voltage or phase imbalance.
[0066] Fig. 2 represents an example of the architecture of a transformer used in the present invention.
[0067] The delta-star transformer AY 150 consists of a part connected in delta TR and a part connected in star ET.
[0068] In the star connection, each phase winding S23, S24, and S25 of the three-phase transformer 150 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 . The current flowing through the coils is the line current.
[0069] 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 .
[0070] 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.
[0071] The windings S20, S21, S22, S23 and S25 are wound around an EM magnetic element.
[0072] Fig. 3 represents a block diagram of a Cont controller according to the present invention.
[0073] 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.
[0074] 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.
[0075] 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.
[0076] More generally, the programs according to the present invention are stored in a storage means. This storage means is readable by the microprocessor 300. This storage means is integrated or not into the Cont controller, and may be removable.
[0077] When the Cont controller is powered on, the software module(s) according to the present invention is / are transferred into the RAM 303 which contains then the executable code according to the present invention as well as the data necessary for the implementation of the invention.
[0078] Thus, all or part of the algorithm and steps described herein can be implemented in software form by executing a set of instructions by a programmable machine, such as a DSP (Digital Signal Processor), a microcontroller, or a processor. All or part of the algorithm and steps described herein can also be implemented in hardware form by a machine or a component (a "chip"), such as an FPGA (Field-Programmable Gate Array) or an ASIC (Application-Specific Integrated Circuit). Thus, the Cont controller includes electronic circuitry adapted and configured to implement the behaviors, algorithms, and steps described herein.
[0079] 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 N.
[0080] At the RlAc network level, the delta connection of the transformer imposes the following relationship on the voltages: VSA + VSB + Vsc = 0
[0081] By construction: PA + PB + VPC ~
[0082] If we rewrite the equations at the level of the R2Ac network: v ni . rv + pA Vb = RJb + Le^ + VPB dlr Vc = ReIc + Le-^ + VPC
[0083] By adding the equations for the 3 phases, we obtain the following relationship:
[0084] Va + Vh + Ve = (1° + Ib + zj
[0085] If we denote Vn as the sum of the three voltages and In as the sum of the three currents, we then obtain r _ v» ln~ R^L^s
[0086] With Re and Le being the leakage impedance in the star of the transformer. Thus, despite a small voltage imbalance or a small phase shift, the current in the neutral and the imbalance are all the greater when the leakage impedance of the transformer is low.
[0087] This current In is expressed on each phase as a zero-sequence current component. In particular, when the consumption on R1AC is zero, the current on each phase is:
[0088] i _ j la~ lb~ ic~ 3
[0089] The system therefore constantly consumes a high phase current.
[0090] 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.
[0091] We can write: = + VpA+VE Vb = ReIb + L^ + VPB + VE V € = Rc I^L^ + V pc + V e
[0092] By adding the previous equations, we then obtain:
[0093] Va+Vb+VC=VN = 3.VE
[0094] Also, 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 in each phase depends only on the power consumption on the R1AC network.
[0095] Fig. 6a represents a first example of an algorithm executed by the controller according to the present invention.
[0096] At step E600, the Cont controller is in a waiting mode for a request E601 from an external device, for example from a device located in the aircraft cockpit to trigger the execution of the present algorithm.
[0097] As long as a request to trigger the execution of this algorithm is not received, the Cont controller remains at step E600.
[0098] Upon receiving the trigger request, the Cont controller checks in step E602 whether the electrical network RlAc or RlbAC should supply electrical energy to the network R2AC or R2bAC and checks in step E606 whether the electrical network R2AC or R2bAC should supply electrical energy to the network R1AC or RlbAC.
[0099] The verification is carried out for example by measuring the direction of the DC current or the power at the output of the transformer 150, through a voltage and current measurement or other.
[0100] If the electrical network R1AC or RlbAC is to supply electrical energy to the network R2ac or R2bAC, the controller Cont commands E603 the closing of switch 100, notifies E604 the external device that switch 100 is closed, goes into mode E605 in which the network R1AC or RlbAC supplies electrical energy to the network R2ac or R2bAC and checks in step E606 whether the electrical network R2AC or R2bAC is to supply electrical energy to the network R1AC or RlbAC.
[0101] If the electrical network R2AC or R2bAC is to supply electrical energy to the network R1ac or RlbAC, the controller Cont commands E607 to open switch 100, notifies E608 the external device that switch 100 is open, and switches to mode E609 in which the network R1AC or RlbAC supplies electrical energy to the network R2ac or R2bAC and checks in step E602 whether the R2AC or R2bAC electrical network should supply electrical energy to the R1AC or RlbAC network.
[0102] Fig. 6b represents a second example of an algorithm executed by the controller according to the present invention.
[0103] At step E620, the Cont controller initializes the present algorithm and then proceeds to step E622 to check whether the electrical network R1AC or RlbAC should supply electrical energy to the network R2AC or R2bAC and to step E626 to check whether the electrical network R2AC or R2bAC should supply electrical energy to the network R1AC or RlbAC.
[0104] The verification is carried out for example by measuring the direction of the DC current or the power at the output of the transformer 150, through a voltage and current measurement or other.
[0105] If the electrical network R1AC or RlbAC is to supply electrical energy to the network R2ac or R2bAC, the controller Cont commands E623 the closing of switch 100, notifies E624 the external device that switch 100 is closed, goes into mode E625 in which the network R1AC or RlbAC supplies electrical energy to the network R2AC or R2bAC and goes to step E626.
[0106] If the electrical network R2AC or R2bAC supplies electrical energy to the network R1AC or RlbAC, the controller Cont commands E627 to open switch 100, notifies E628 the external device that switch 100 is open, switches to mode E629 in which the network R1AC or RlbAC supplies electrical energy to the network R2ac or R2bAC and proceeds to step E622.
[0107] Figure 6c represents a third example of an algorithm executed by the controller according to the present invention.
[0108] At step E640, the Cont controller initializes the present 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 electrical network R2AC or R2bAC must supply electrical energy to the network R1AC or RlbAC or to switch to an operating mode in which the electrical network R1AC or RlbAC must supply electrical energy to the network R2AC or R2bAC.
[0109] If a request is received to switch to an operating mode in the R2AC or R2bAC electrical network that supplies electrical power to the R1AC or RlbAC network, the Cont controller commands E643 to close switch 100, notifies E644 the external device that switch 100 is closed, switches to mode E645 in which the R1AC or RlbAC network supplies electrical power to the R2AC or R2bAC network, and checks in step E646 whether a request is received to switch to a mode of operation in which the electrical network RlAc or RlbAC must supply electrical energy to the network R2AC or R2bAC.
[0110] If a request is received to switch to an operating mode in the electrical network R1AC or RlbAC which must supply electrical energy to the electrical network R2AC or R2bAC, the controller Cont commands E647 to open switch 100, notifies E648 to the external device that switch 100 is open, switches to the mode E649 in which the network R1AC or RlbAC supplies electrical energy to the network R2AC or R2bAC, checks E642 if a request is received to switch to an operating mode in the electrical network R2AC or R2bAC which must supply electrical energy to the network R1AC or RlbAC.
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. R2AC, 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 method 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, - 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, - 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 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 any one of claims 1 or 2, characterized in that representative information is obtained by a controller upon request from a remote device.
4. A 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, 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. R2AC, 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 of controlling a switch to connect a common point of the transformer delta Y 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 transformer delta Y to the neutral of the second electrical network if the first electrical network is to supply electrical energy to the second electrical network.
6. Product computer program comprising instructions for implementing, by a processor, the process according to any of claims 1 to 4, when said program is executed by said processor.
7. Information storage medium storing a computer program comprising instructions for implementing, by a processor, the method according to any one of claims 1 4, when said program is read and executed by said processor.