Patent Application
20250175074
This specification is based upon and claims the benefit of priority from UK Patent Application Number 2317962.5 filed on 24 Nov. 2023, the entire contents of which are incorporated herein by reference.
This disclosure relates to an electrical power system comprising a DC electrical network and to a method of controlling such an electrical power system.
In aerospace, DC electrical networks are increasingly used to distribute electrical power between power sources and loads. For example, AC electrical power generated by one or more engine shaft-coupled electrical generators and rectified by AC:DC converters, or DC electrical power supplied by an energy storage system (ESS), may be distributed to propulsive and/or non-propulsive electrical loads through one or more DC networks.
A DC:DC power electronic converter may be used to interface between two DC parts of an electrical power system. For example, an electrical power system may have two DC electrical networks with different operating voltages, and a DC:DC converter may provide an interface between the two networks so that power can be exchanged between them. In another example, an electrical power system may include a DC electrical network that is supplied with power by an energy storage system (e.g., a battery). The terminal voltage of a battery typically decreases with its state of charge, so a DC:DC converter may be provided between the terminals of the energy storage system and the DC electrical network to stabilise the voltage supplied to the DC electrical network as the battery discharges.
In the event of a fault in a DC network connected to one side of a DC:DC converter, a zero or near-zero impedance is presented across the DC terminals facing the fault. This very low impedance may result in a very large current—referred to herein as the fault current—being fed from the healthy side of the converter to the fault site. It is therefore desirable to isolate the fault, to stop the fault current and to allow remaining healthy parts of the DC network to continue operating.
According to a first aspect, there is an electrical power system comprising: a DC:DC power converter connected between a DC power source and a DC electrical network, the DC electrical network comprising at least a first zone for powering a first group of one or more electrical loads, a second zone for powering a second group of one or more electrical loads, a first controllable circuit breaker, and a second controllable circuit breaker. The electrical power system further comprises a control system configured to:
In an embodiment, the control system is further configured to, if the gradually increasing amount of current supplied to the DC electrical network reaches a level defined by the first or second trip profile, control the plurality of transistors of the DC:DC power converter to reduce the amount of current supplied to the DC electrical network before opening the first or second controllable circuit breaker.
In an embodiment, the control system is configured to block (i.e., reduce to zero) the supply of current from the DC power source to the DC electrical network before opening the first or second controllable circuit breaker.
In an embodiment, at least one of the first and second controllable circuit breakers is located between the first zone and the second zone.
In an embodiment, the first controllable circuit breaker is located between the first zone and the DC:DC power converter; and the second controllable circuit breaker is located between the first zone and the second zone.
In an embodiment, the control system is further configured to, after opening the second controllable circuit breaker: determine, based on the one or more operating parameters of the electrical power system, whether the fault in the DC electrical network has been isolated.
In an embodiment, the control system is further configured to, in response to determining the fault in the DC electrical network has been isolated: control the switching operation of the plurality of transistors of the DC:DC power converter to supply a controlled amount of current from the DC power source to the DC electrical network to charge one or more capacitors of the DC electrical network.
In an embodiment, the control system is further configured to, before supplying the controlled amount of current from the DC power source to the DC electrical network to charge the one or more capacitors, control the plurality of transistors of the DC:DC power converter to block the supply of current from the DC power source to the DC electrical network.
In an embodiment, the control system is further configured to, in response to determining the fault in the DC electrical network has not been isolated: control the switching operation of the plurality of transistors of the DC:DC power converter to supply a gradually increasing amount of current from the DC power source to the DC electrical network; and open the first controllable circuit breaker if the gradually increasing amount of current supplied by the DC power source reaches a level defined by the first trip profile.
In an embodiment, controlling the plurality of transistors to supply a controlled amount of current from the DC power source to the DC electrical network comprises: repeatedly switching the DC:DC power converter between two or more different switching configurations of the DC:DC power converter to control an average amount of current transferred from the DC power source to the DC electrical network.
In an embodiment, the control system is configured to control an amount of time the DC:DC power converter is in each of the two or more different switching configurations to control the average amount of current transferred from the DC power source to the DC electrical network.
In an embodiment, the DC electrical network further comprises a third zone for powering a third group of one or more electrical loads, and a third controllable circuit breaker. The control system is further configured to: open the third controllable circuit breaker if the gradually increasing amount of current supplied to the DC electrical network reaches a level defined by a third trip profile, the third trip profile defining a gradually decreasing current level, the gradually decreasing current level defined by the second trip profile being higher than the gradually decreasing current level defined by the third trip profile.
In an embodiment, the DC:DC power converter is a Dual Active Bridge (DAB) DC:DC power converter or an H-bridge DC:DC power converter.
In an embodiment, the DC:DC power converter is a DAB DC:DC power converter comprising: a DC:AC converter circuit having a DC and an AC side; an AC:DC converter circuit having a DC side and an AC side; and an AC link connecting the AC side of the DC:AC circuit and the AC side of the AC:DC converter circuit, the AC link including a transformer having a first winding connected to the AC side of the DC:AC converter circuit and a second winding connected to the AC side of the AC:DC converter. The DC side of the DC:AC converter circuit is connected to the DC power source. The DC side of the AC:DC converter circuit is connected to the DC electrical network. In an embodiment, controlling the plurality of transistors to supply a controlled amount of current from the DC power source to the DC electrical network comprises one or more of: modifying a switching operation of a plurality of transistors of the DC:AC converter circuit so that a waveform of a voltage applied to the first winding of the transformer changes from a square wave to a quasi-square wave; and modifying the switching operation of the first plurality of transistors so that a duty cycle of a waveform of a voltage applied to the first winding of the transformer changes.
In embodiment, the plurality of transistors of the DC:DC power converter are MOSFETs, for example Silicon Carbide (SiC) or Gallium Nitride (GaN) MOSFETs.
In an embodiment, the one or more operating parameters of the electrical power system includes a voltage of the DC electrical network, and the control system is configured to determine there is a fault in the DC electrical network in response to a drop in the voltage.
In an embodiment, the first and second controllable circuit breakers comprise mechanical contactors or semiconductor switches, for example hybrid circuit breakers, solid state power controllers or solid-state circuit breakers.
In an embodiment, the DC power source comprises an energy storage system (e.g., one or more batteries) or a second DC electrical network.
The control system can take any suitable form. For example, the control system may be a single controller, or multiple distributed controllers. It may be implemented in hardware and/or software.
The electrical power system may be or form part of an aircraft power and propulsion system. The power and propulsion system may be a purely electric power and propulsion system, a hybrid propulsion (e.g., gas turbine and battery/fuel cell hybrid, or battery and fuel cell hybrid system), or a ‘more electric’ propulsion system having propulsive gas turbine engines that interface with an electrical power system through spool-coupled electrical machines.
According to a second aspect, there is an aircraft comprising an electrical power system according to the first aspect.
According to a third aspect, there is a method of operating an electrical power system. The electrical power system comprises: a DC:DC power converter connected between a DC power source and a DC electrical network, the DC electrical network comprising at least a first zone for powering a first group of one or more electrical loads, a second zone for powering a second group of one or more electrical loads, a first controllable circuit breaker and a second controllable circuit breaker. The method comprises:
The control system opens the first controllable circuit breaker if the gradually increasing amount of current supplied to the DC electrical network reaches a level defined by the first trip profile. The control system opens the second controllable circuit breaker if the gradually increasing amount of current supplied to the DC electrical network reaches a level defined by the second trip profile. The first and second trip profiles define gradually decreasing current levels. The gradually decreasing current level defined by the first trip profile is higher than the gradually decreasing current level defined by the second trip profile.
In an embodiment, the method further comprises: in response to the gradually increasing amount of current supplied to the DC electrical network reaching the level defined by the second trip profile, before opening the second controllable circuit breaker, controlling the switching operation of the plurality of transistors of the DC:DC power converter to block the supply of current from the DC power source to the DC electrical network.
In an embodiment, the method further comprises, after opening the first or second controllable circuit breaker: controlling the switching operation of the plurality of transistors of the DC:DC power converter to supply a controlled amount of current from the DC power source to the DC electrical network to charge one or more capacitors of the DC electrical network.
In an embodiment, the method further comprises, after opening the first or second controllable circuit breaker and before controlling the switching operation of the plurality of transistors of the DC:DC power converter to supply a controlled amount of current from the DC power source to the DC electrical network to charge one or more capacitors of the DC electrical network: controlling the switching operation of the plurality of transistors of the DC:DC power converter to block the supply of current from the DC power source to the DC electrical network.
The skilled person will appreciate that except where mutually exclusive, a feature described in relation to any one of the above aspects may be applied mutatis mutandis to any other aspect. Furthermore, except where mutually exclusive, any feature described herein may be applied to any aspect and/or combined with any other feature described herein.
Embodiments will now be described by way of example only with reference to the accompanying drawings, which are purely schematic and not to scale, and in which:
In the event of a fault in the DC electrical network 12, a low impedance (in the limit, zero) will be presented across the terminals of the DC:DC power converter 100 facing the DC network 12. This will cause a large fault current to flow from the DC power source 11 to the DC network 12 via the DC:DC converter 100. To protect loads and other components (e.g., cables and connectors) from the fault current and to allow continued operation of the remaining healthy portions of the DC network 12, it is desirable to isolate the fault.
To this end, the DC electrical network 12 is divided into multiple (i.e., at least two) zones connected via controllable circuit breakers. In this non-limiting example, there are three zones Z1, Z2, Z3 and three circuit breakers X1, X2, X3. The first zone Z1 includes a first group of one or more loads 12L-a, 12L-b, the second zone Z2 includes a second first group of one or more loads 12L-c, 12L-d and the third zone Z3 includes a third first group of one or more loads 12L-e, 12L-f. The first circuit breaker X1 is located between the DC:DC converter 100 and the first zone Z1. The second circuit breaker X2 is located between the first zone Z1 and the second zone Z2. The third circuit breaker X3 is located between the second zone Z2 and the third zone Z3. If there is a fault in, e.g., one of the loads 12L-f in the third zone Z3, the control system 150 can open the third circuit breaker X3 to isolate the third zone Z3 from the remaining, healthy zones Z1, Z2 which can then return to normal operation.
To identify which circuit breaker(s) should be opened to isolate the fault, the control system 150 implements a fault discrimination procedure. An example fault discrimination procedure is illustrated in
When the fault occurs, a fault current IF, the value of which may depend on the voltage of the DC power source 11 and the impedance of the fault current path, is supplied to the DC network 12. As illustrated in
While the fault discrimination procedure of
An example fault discrimination procedure in accordance with the present disclosure is illustrated in
The amount of fault current supplied to the network 12 can be controlled by controlling a switching operation of the transistors of the DC:DC converter 100, as explained in detail in UK Patent Application Nos. 2315701.9 (filed 13 Oct. 2023), 2315703.5 (filed 13 Oct. 2023) and 2316708.3 (1 Nov. 2023), the entire contents of which are incorporated herein by reference. By way of example, some of these DC:DC converter control techniques are described below with reference to
Returning to
As indicated in
Another example fault discrimination procedure is illustrated in
Another example fault discrimination procedure is illustrated in
In more detail, when, at time t1, the current reaches the level defined by the third trip profile 203, the control system 150 instructs the DC:DC converter 100 to block the supply of current to the network 12. After blocking the current (e.g., after a short time delay of δ, perhaps of the order of a few μs), the control system 150 instructs the third circuit breaker X3 to open. If the control system 150 detects the fault has been isolated (e.g., a sudden rise in the network voltage), the fault discrimination and isolation procedure can stop. If not, the control system 150 again increases the amount of fault current allowed to reach the network 12, in this example starting from the current level which had previously been reached. When, at time t2, the current level reaches the gradually decreasing current level defined by the second trip profile 202, the control system 150 instructs the DC:DC converter 100 to block the supply of current to network 12. After blocking the current, the control system 150 instructs the second circuit breaker X2 to open. If the control system 150 detects the fault has been isolated, the fault discrimination and isolation procedure can stop. If not, the control system 150 again increases the amount of fault current allowed to reach the network 12, in this example starting from the current level which had previously been reached. When, at time t3, the current level reaches the gradually decreasing current level defined by the first trip profile 201, the control system 150 instructs the DC:DC converter 100 to block the supply of current to network 12. After blocking the current, the control system 150 instructs the first circuit breaker X1 to open.
In each of the examples described above, the trip profiles 201-203 define linearly decreasing current levels with equal gradients but different starting values. This is not intended to be limiting. For example, the trip profiles may be curves and/or may have different gradients. The trip profiles and the combination of trip profiles may be selected according to the design and requirements of the electrical power system.
Further, in each of the examples described above, the controlled and gradually increasing amount of current supplied to the DC network 12 increases in a linear fashion from zero. This is not intended to be limiting. The current could instead be increased in a non-linear fashion and/or from a low but non-zero initial value. Generally, if the current is increased more aggressively (e.g., in a quadratic fashion) or from a higher starting current, the fault will be isolated faster. Conversely, if the current is increased less aggressively (e.g., logarithmically or with a reduced linear gradient), the fault will take longer to be isolated. By taking account of the trip profiles 201-203, the manner (e.g., linear or quadratic), rate (e.g., gradient) and zero-time current offset of the controlled current increase may be selected to minimize the integrated value of I*t or I2*t.
Further, in each of the examples described above there are three zones Z1-3 and three circuit breakers X1-3. This is a simple example selected for each of explanation and is not intended to be limiting. For example:
Turning now to
The process is illustrated in
Supplying a controlled current through control of the DC:DC converter 100 to pre-charge the capacitor(s) may provide further advantages, including the optional omission of pre-insertion resistors (PIRs) in some or all of the power system. PIRs are conventionally fitted to converters to protect the capacitors and converter diodes against high inrush currents at converter start-up, which can degrade the capacitors and semiconductors and limit their lifetime. However, by controlling the current as described herein, the inrush current can be controlled and the PIRs omitted.
In each of the embodiments described above with reference to
Each of the DC:AC converter circuit 110 and the AC:DC converter circuit 120 can take any form suitable for the desired system functionality, and for this reason no circuit structure is shown in
The converter circuits 110, 120 could, however, take other forms, for example:
The normal operation of a DAB DC:DC converter 100 under the control of a control system 150 is illustrated in
When the fault occurs, the voltage V2 collapses to zero or near-zero. The transformer 135 now supports the whole of the alternating voltage V1 produced by the healthy converter circuit 110. If the transistors 121-L, 121-H, 122-L, 122-of the AC:DC converter circuit 120 continue to be switched to produce a 50:50 duty cycle square wave voltage waveform, a fully rectified version of the transformer current is transferred to the faulted network. In other words, the amount of current supplied to the faulted DC network will depend on the AC link current. It is noted that a similar transfer of current can occur if its transistors are turned off, leaving the anti-parallel diodes to conduct instead.
According to the first example, to control the AC link current, the control system 150 responds to the fault by modifying the switching signals supplied to the transistors 111-L,111-H, 112-L, 112-H so that the voltage V1 applied to the first side of the transformer 135 is a quasi-square wave. Those skilled in the art will appreciate this to mean that the voltage waveform V1 has zero-voltage notches, or portions, between positive and negative voltage portions of waveform, reducing the volt-time area applied to the transformer leakage inductance. In the case of an H-bridge circuit 110, this may be achieved by switching on the two upper transistors or the two lower transistors of the H-bridge 110. By changing the converter switching pattern in this way, the magnitude of the AC link current, and consequently the amount of fault current supplied to the DC network, can be controlled.
While a DAB DC:DC converter 100 with H-bridge circuits is illustrated other converter circuits (e.g., two-level, three-phase circuits) could be used instead. For example, in the case of a two-level, three-phase converter, the fault-feeding configuration would have either two high-side and one low-side transistor switched on or one high-side and two low-side transistors switched on. The crowbar configuration would have only high-side or only low-side transistors switched on.
In another example in accordance with the present disclosure,
The H-bridge DC:DC power converter 100′ comprises a first half-bridge circuit 110′ and a second half-bridge circuit 120′. Each of the first and second half-bridge circuits 110′, 120′ includes a low-side transistor 111-L, 121-L and a high-side transistor 111-H, 121-H. Nodes at the mid-points of the two half-bridge circuits 110′, 120′ (i.e., between the low- and high-side transistors) are connected by an AC link comprising an inductor 125. The high- and low-DC sides of the first half-bridge 110′ are connected to the positive and negative terminals of the battery 15. The high- and low-DC sides of the second half-bridge 120′ are connected to the positive and negative rails of the DC electrical network 11.
During normal operation of the H-bridge converter 100′, the low-side transistor 111-L of the first half-bridge 110′ is switched off and the high-side transistor 111-H of the half-bridge 110′ is switched on. The low- and high-side transistors 121-L, 121-H of the second half-bridge are switched between a configuration in which the low-side transistor 121-L is switched on and the high-side transistor 121-H is switched off, and a configuration in which the low-side transistor 121-L is switched off and the high-side transistor 121-H is switched on so that the inductor 125 is alternately charged by the battery 15 and discharged to the DC network 12.
In order to supply a controlled amount (e.g., a gradually increasing amount) of fault current in the presence of a fault in the DC network, the control system 150 repeatedly switches the H-bridge converter 100′ between a plurality of different switching configurations for which a different amount of current is supplied from the DC power source (e.g., the battery 15) to the faulted network 12. By controlling the fraction of time that the H-bridge converter 100′ is in each configuration, the average amount of current supplied to the DC network is controlled.
Referring to
In the second configuration, the low-side transistor 111-L of the first half-bridge circuit 110′ is switched on, the high-side transistor 111-H of the first half-bridge circuit 110′ is switched off, the low-side transistor 121-L of the second half-bridge circuit 120′ is switched off, and the high-side transistor 121-H of the second half-bridge circuit 120 is switched on. In the second configuration, fault current is supplied to the faulted DC network and, since the high-side transistor 111-H of the first half-bridge 110′ is switched off, the current through the inductor 125 decreases (i.e., while in the second configuration, current decays with time constant L/R, L and R being the inductance and resistance of the current path).
In the third configuration, the low-side transistor 111-L of the first half-bridge circuit 110′ is switched off, the high-side transistor 111-H of the first half-bridge circuit 110′ is switched on, the low-side transistor 121-L of the second half-bridge circuit 120′ is switched on, and the high-side transistor 121-H of the second half-bridge circuit 120′ is switched off. In the third configuration, fault current is contained within the converter 100′ and cannot reach the faulted DC network. Thus, time spent in the third configuration reduces the average current supplied to the DC network. Current through the inductor 125 increases in the third configuration, as the high-side transistor 111-H of the first half-bridge circuit 110′ is switched on.
In the fourth configuration, the low-side transistor 111-L of the first half-bridge circuit 110′ is switched on, the high-side transistor 111-H of the first half-bridge circuit 110′ is switched off, the low-side transistor 121-L of the second half-bridge circuit 120′ is switched on, and the high-side transistor 121-H of the second half-bridge circuit 120′ is switched off. In the third configuration, fault current is contained within the converter 100′ and cannot reach the faulted DC network. Thus, time spent in the third configuration reduces the average current supplied to the DC network. Current through the inductor 125 decreases in the third configuration, as the high-side transistor 111-H of the first half-bridge circuit 110′ is switched off.
Turning to
In the fifth configuration, the low-side transistor 111-L of the first half-bridge circuit 110′ is switched off, the high-side transistor 111-H of the first half-bridge circuit 110′ is switched on, the low-side transistor 121-L of the second half-bridge circuit 120′ is switched on, and the high-side transistor 121-H of the second half-bridge circuit 120′ is switched on. A fraction of the fault current from the battery 15 is contained via the illustrated freewheeling path (solid lines with arrows) and a remaining fraction of the fault current spills to the DC network (dashed lines with arrows). Since the high-side transistor 111-H of the first half-bridge circuit 110′ is switched on in the fifth configuration, the current through the inductor 125 is increasing.
In the sixth configuration, the low-side transistor 111-L of the first half-bridge circuit 110′ is switched on, the high-side transistor 111-H of the first half-bridge circuit 110′ is switched off, the low-side transistor 121-L of the second half-bridge circuit 120′ is switched on, and the high-side transistor 121-H of the second half-bridge circuit 120′ is switched on. A fraction of the fault current from the battery 15 is contained via the illustrated freewheeling path (solid lines with arrows) and a remaining fraction of the fault current spills to the DC network (dashed lines with arrows). Since the high-side transistor 111-H of the first half-bridge circuit 110′ is switched off in the sixth configuration, the current through the inductor 125 is decreasing.
To access the spill configurations (i.e., the fifth and sixth configurations), it is necessary that the parallel-connected diode associated with the high-side transistor 121-H of the second half-bridge circuit 120′ becomes forward biased. This happens if the voltage developed across the low-side transistor 121-L exceeds the forward voltage drop of the diode, which is typically only about 2-3 V. Whether or not this condition is met depends on the level of current and the gate driver. For SiC MOSFETs, the selection of the device and its drain-source resistance, RDS-on, combined with a higher than rated current (e.g., 1.5 per-unit) should enable the condition to be met in all relevant circumstances. However, an additional or alternative approach—shown in the right-hand side of
In the first example, fault current is supplied from the left-hand side of the converter 100′ (e.g., from a battery 15) to the DC network in both the first and second configurations. However, the amount of current increases when the converter 100′ is in the first configuration but decreases when the converter 100′ is in the second configuration. The average amount of current will therefore depend on the fraction of time spent in the second configuration: the greater the fraction of time the converter 100′ is the second configuration, the lower the average current will be. In this example, the control system 150 controls the converter 100′ so that it spends approximately twice as long in the second configuration as the first configuration (i.e., the converter 100′ is in the first configuration for one third of the time and in the second configuration for two thirds of the time). If more time was spent in the second configuration, the average current would be lower and vice versa.
In the second example, current is supplied to the DC network in the second configuration but contained within the converter 100′ in the third configuration. The average amount of current supplied to the DC network will therefore be greater than zero but less than the current supplied to the converter in the second configuration. This is shown by the line labelled “Average”. The actual value will depend on the fraction of time spent in the third configuration: the greater the fraction of time the converter 100′ is the third configuration, the lower the average current will be. In this example, the control system 150 controls the converter 100′ so that it spends approximately twice as long in the third configuration as the second configuration (i.e., the converter 100′ is in the second configuration for one third of the time and in the third configuration for two thirds of the time). If more time was spent in the third configuration, the average current would be lower and vice versa.
In the third example, the converter 100′ starts in the fifth configuration, where only a fraction of the fault current spills to the network and the current through the inductor 125 is increasing. The converter 100′ is then switched to the second configuration, where the full (or substantially full) fault current is supplied to the DC network and the current through the inductor 125 is decreasing. The average amount of current, shown by the line labelled “Average”, is therefore greater than the fraction of current that spills to network in the fifth configuration but lower than the amount of fault current supplied to the fault site in the second configuration. The average amount of current may be adjusted by controlling a respective fraction of time the converter 100′ is in the second and fifth configurations. The greater the fraction of time the converter 100′ is in the fifth configuration, the lower the average current and vice versa.
In each of the above examples, the converter 100 is repeatedly switched between two of the six described configurations. These examples are not intended to be limiting: two or more than two of the six configurations may be used, and different combinations of configurations may be used. Any one or more of the following may be considered:
As explained above, the present disclosure may be implemented in an aircraft electrical power system. Exemplary power and propulsion systems are shown in
At the start of the method 300, the electrical power system is operating in a normal condition. In other words, it is functioning as intended with no faults. The control system 150 controls a switching state of the transistors of the DC:DC converter to, for example, match the terminal voltage of the DC power source (e.g., ESS 15 or DC network 11) to the terminal voltage of the DC network (e.g., DC network 12).
At 310, the control system 150 monitors one or more operating parameters of the electrical power system. For example, the control system 150 may monitor the voltage across the output terminals of the DC:DC converter that face the DC electrical network, or it may monitor one or more other voltages or currents in the DC electrical network.
At 320, the control system 150 determines, based on the one or more operating parameters, whether there is a fault in the DC electrical network. For example, the control system 150 may monitor the one or more operating parameters for changes indicative of a fault. In one example, the control system determines whether there is a fault based on whether there is a sudden drop in the voltage across the output terminals of the DC:DC converter. If no fault is detected (“N”), the method proceeds back to 310 and the control system continues to monitor the one or more operating parameters. If the control system 150 determines there is a fault (“Y”), the method proceeds to 330.
At 330, the control system 150 controls a switching operation of a plurality of transistors of the DC:DC power converter to supply a controlled and gradually increasing amount of current from the DC power source to the DC electrical network. For example, where the DC:DC converter is a DAB DC:DC converter 100 as shown in
At 340, the control system 150 controls the opening of controllable circuit breakers in the DC network 12 based on pre-defined circuit breaker trip profiles and the gradually increasing amount of current supplied to the DC electrical network. In particular, when the increasing amount of current from step 330 reaches a level defined by a trip profile, the control system 150 opens the corresponding circuit breaker. In some examples, the control system 150 may effectively ignore a high initial current caused by capacitor discharge, as described above with reference to
At 350, the control system 150 determines whether the opening of the contactor 340 has isolated the fault. For example, the control system 150 may continue to monitor one or more operating parameters as in step 310. If, for example, the network voltage rises after opening the contactor at 340, the control system determines the fault is isolated (“Y”) and the method 300 either ends or proceeds to optional step 360. If, e.g., the network voltage does not change, the control system 150 determines the fault has not been isolated (“N”), the method returns to step 330.
At step 330, the control system 150 continues to increase the current supplied to the DC network 12 via the DC:DC converter. The method proceeds to step 340. At 340, when the increasing amount of current from step 330 reaches a level defined by another trip profile, the control system 150 opens the corresponding circuit breaker. The method proceeds to 350, where again the control system 150 determines whether the opening of the circuit breaker at step 340 has isolated the fault. The loop is repeated until the fault is isolated and method either ends or proceeds to optional step 360.
At optional step 360, having isolated the fault, the control system 150 blocks all current from being supplied from the cleared DC network, for example by turning of all of the transistors of the DC:DC converter. In some examples, step 360 may be omitted and proceed straight to step 370, for example where an already low or zero current was being supplied to the DC network.
At 370, the control system 150 prepares the electrical power system for a restart by recharging one or more capacitors that have discharged a consequence of the fault. To do so, the control system 150 controls the DC:DC converter to supply a controlled, low current to the DC network to charge the capacitor(s).
Having charged the capacitor(s), the electrical power system restarts and begins normal operation. The method 300 therefore proceeds back to 310 where the control system 150 monitors and provides normal control of the system.
Various examples have been described, each of which feature various combinations of features. It will be appreciated by those skilled in the art that, except where clearly mutually exclusive, any of the features may be employed separately or in combination with any other features and the invention extends to and includes all combinations and sub-combinations of one or more features described herein.
It will also be appreciated that whilst the invention has been described with reference to aircraft and aircraft propulsion systems, the techniques described herein could be used for many other applications. These include, but are not limited to, automotive, marine and land-based applications.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2317962.5 | Nov 2023 | GB | national |
