Method for managing power transitions between generation modes

Abstract

The invention relates to a method for managing power transitions between a first generation mode and a second generation mode in a turbomachine that has a high-pressure shaft from which high-pressure power is drawn and a low-pressure shaft from which low-pressure power is drawn, the first generation mode corresponding to a first power sharing between the high-pressure power and the low-pressure power and the second generation mode corresponding to a second power sharing between the high-pressure power and the low-pressure power, the sum of the high- and low-pressure powers drawn in each generation mode defining the same total power, the transition between the first generation mode and the second generation mode taking place over a predetermined duration (t2-t1) while applying the same smoothing function f(t) both to the high-pressure power and to the low-pressure power without changing the total power.

Description

[0001] Description

[0002] Title of the invention: Method for managing power transitions between generation modes

[0003] Technical Field

[0004] The present invention relates to the field of internal hybridization of more electric or even highly electrified aircraft turbomachines.

[0005] Prior art

[0006] Climate change is a major concern for many legislative and regulatory bodies around the world. Indeed, various carbon emission restrictions have been, are being, or will be adopted by various states. In particular, an ambitious standard applies to both new aircraft types and those currently in operation, requiring the implementation of technological solutions to ensure their compliance with current regulations. Civil aviation has been mobilizing for several years now to contribute to the fight against climate change.

[0007] Technological research efforts have already led to very significant improvements in the environmental performance of aircraft. The Applicant takes into consideration the impact factors in all phases of design and development to obtain less energy-intensive, more environmentally friendly aeronautical components and products whose integration and use in civil aviation have moderate environmental impacts with the aim of improving the energy efficiency of these aircraft.

[0008] Consequently, the Applicant is constantly working to reduce its climate impact by using methods and operating virtuous development and manufacturing processes that minimize greenhouse gas emissions to the minimum possible in order to reduce the environmental footprint of its activity. This sustained research and development work covers new generations of aircraft turbomachines, the weight reduction of aircraft, in particular through the materials used and lighter onboard equipment, the development of the use of electric technologies to provide propulsion, and, as essential complements to technological progress, aeronautical biofuels.

[0009] Turbomachine hybridization is achieved by an electrical system interfacing between the mechanical shafts of the turbomachine and the aircraft's electrical network.

[0010] This system must ensure the starting functions of the turbomachine (HP and / or LP), the generation of controlled electrical power to supply the propulsive and non-propulsive loads and the injection or extraction of controlled power from the turbomachine shafts to assist it if necessary. The balance between the power consumed by the loads and the power generated by the available sources is ensured by controlling the bus voltage (in frequency and maximum amplitude for the AC voltage and in amplitude for the DC voltage), while respecting the system constraints.

[0011] Conventionally, and as illustrated in Figure 9, the architectures of the internal hybridization systems of a turbomachine 100 are based on DC channels connected in parallel, typically an HP channel (corresponding to the high pressure shaft 102 of the turbomachine) and an LP channel (corresponding to its low pressure shaft 104). These two DC channels are each produced by an electrical machine 106, 108, typically a permanent magnet synchronous machine, associated with an AC / DC controlled reversible power converter 110, 112 delivering a DC voltage to a DC bar 114 connected to the loads 116 to be powered (propulsive and / or non-propulsive). The control of the reversible power converters is conventionally provided by a control module 118 which receives its orders from the turbomachine controller ECU 120 (for “Electronic Control Unit” in English).

[0012] An external source, typically a set of batteries or supercapacitors, associated with a reversible DC / DC converter (the set not being illustrated) can also be connected in parallel with these HP and LP channels to provide power to the HP and / or LP shafts, for example when starting the turbomachine.

[0013] The generation of power from the HP and LP shafts of the turbomachine has a different impact on its performance (operability) or on the thrust it generates depending on the requested take-off shaft. The turbomachine controller therefore has the particular function during the mission of adapting the percentages of participation of the electrical machines in this power generation to optimize its operating point. For this, the ECU 120 will ask the control module 118 to share the take-off powers between the HP and LP shafts to supply the loads 116 of the network which generally have dynamic behaviors which can be variable, in particular the so-called active loads.

[0014] As shown in Figure 10, this sharing of the power draws between the HP and LP shafts requested by the ECU can, over the duration of a mission, vary according to several successive modes, such as a first generation mode in which 60% of the power is drawn from the HP shaft and 40% of the power is drawn from the LP shaft and a second generation mode in which 100% of the power is drawn from the LP shaft, as illustrated. However, when changing generation mode (at t0), due to the instantaneous modification of the power ratio, draw impacts are created on each shaft of the turbomachine, the transients of which induce disturbances on the regulation of the turbomachine such as to lead to a rejection of slow disturbances (typically <lHz). L'impact sur l'arbre mécanique peut également exciter des modes mécaniques non désirés.

[0015] Document US 20220371532 proposes an electrical system comprising a first electrical machine coupled to a first gas turbine and a second electrical machine coupled to a second gas turbine.

[0016] Statement of the invention

[0017] To this end, the invention is the result of technological research aimed at significantly improving aircraft performance and, in this sense, contributes to reducing the environmental impact of these aircraft. To this end, the main purpose of the present invention is to limit the impacts of power drawdowns when there is a change in generation mode, while respecting the quality constraints of the electrical network. Another purpose is to make it possible to manage a possible load impact during this change in generation mode.

[0018] These aims are achieved by a method for managing power transitions between a first generation mode and a second generation mode in a turbomachine having a high pressure shaft from which high pressure power is taken and a low pressure shaft from which low pressure power is taken, the first generation mode corresponding to a first power sharing between the high pressure power and the low pressure power and the second generation mode corresponding to a second power sharing, different from the first, between the high pressure power and the low pressure power, the sum of the high and low pressure powers taken in each generation mode defining the same total power,characterized in that the transition between the first generation mode and the second generation mode takes place over a predetermined duration (t2-tl) without modification of the total power and by applying the same smoothing function f(t) to the sampling of both the high pressure power and the low pressure power.,

[0019] Thus, by ensuring smoothing of the power draw setpoints during generation, the regulation of the turbomachine is not disturbed and there is no unwanted excitation of mechanical modes. Compliance with the quality of the electrical network is ensured because there is no change in the total power.

[0020] Preferably, the smoothing function f(t) is a continuous or discrete bounded monotone function [0; 1] with f(tl)=O and f(t2) = 1, typically a linear function f(t) = Kt, K being a proportionality factor, or a first-order function of type f(t) = 1-exp (-t / tau), tau being a time constant.

[0021] Advantageously, the predetermined duration is between 1 and 10 seconds. Preferably, when a load impact corresponding to an additional power draw occurs during the transition, this additional draw is carried out at the time of the impact according to the first power sharing or according to the second power sharing, the smoothing function f(t) remaining applied upstream of this moment from a start of the transition and downstream of this moment until an end of the transition.

[0022] According to the embodiment envisaged, the additional power draw is carried out on each of the high or low pressure shafts according to the first power sharing and responds to the following equation:

[0023] P = (1 - (t)) * P0(t) + (t) * ?i(t), or is carried out on each of the high or low pressure shafts according to the second power split and responds to the following equation: power requested in the first generation mode, PI the power requested in the second generation mode and tl the instant of the mode change.

[0024] The invention also relates to a turbomachine (typically an aeronautical turbomachine such as a hybrid turbofan, a hybrid turboprop or a hybrid helicopter turbomachine) implementing the aforementioned method.

[0025] More particularly, the turbomachine may further comprise an adaptation module configured to generate the smoothing function and arranged between a control module receiving power instructions from an ECU and power converters associated with the electrical machines mounted on the high and low pressure shafts.

[0026] Brief description of the drawings

[0027] Other characteristics and advantages of the present invention will emerge from the description given below, with reference to the appended drawings which illustrate an exemplary embodiment thereof without any limiting character and in which:

[0028] [Fig. 1] Figure 1 illustrates an architecture of an internal hybridization system of a turbomachine according to the invention, [Fig. 2] Figure 2 shows the impact of the invention on the setpoints of the extraction powers,

[0029] [Fig. 3] Figure 3 shows a first example of the shape of the setpoints for the extraction powers following an additional extraction in the transition phase,

[0030] [Fig. 4] Figure 4 illustrates a first example of the implementation of the control logic making it possible to obtain the appearance of the instructions in Figure 3,

[0031] [Fig. 5] Figure 5 shows the different stages of a first example of a process for obtaining the shape of the instructions in Figure 3,

[0032] [Fig. 6] Figure 6 shows a second example of the shape of the setpoints for the extraction powers following an additional extraction in the transition phase,

[0033] [Fig. 7] Figure 7 illustrates a second example of the implementation of the control logic making it possible to obtain the appearance of the instructions in Figure 6,

[0034] [Fig. 8] Figure 8 shows the different stages of a second example of a process for obtaining the shape of the instructions in Figure 6,

[0035] [Fig. 9] Figure 9 shows an architecture of an internal hybridization system of a turbomachine according to the prior art, and

[0036] [Fig. 10] Figure 10 illustrates the power sampling instructions associated with the prior art architecture.

[0037] Description of the embodiments

[0038] The principle of the invention is based on limiting the impacts of power extraction on the high pressure (HP) and / or low pressure (LP) shafts in the event of a change in generation mode, by introducing a smoothing function for the extraction power setpoints while ensuring that the total extraction power allows the power supply of the electrical network of the turbomachine and the aircraft. As illustrated in FIG. 1 (modules identical to those of the prior art are assigned the same references and are not described again), this smoothing function f(t) allowing a smooth transition between two generation modes is obtained by adding an adaptation module 200 for the setpoints received from the ECU and intended for the electrical machines. This module is arranged between the control module 118 and the power converters 110, 112 associated with the electrical machines 106, 108 mounted on the high and low pressure shafts 102, 104.

[0039] Figure 2 illustrates the setpoints of the drawdown powers during the transition phase (smoothing) reflecting the change in generation mode, after integration of the smoothing function performed by the adaptation module 200. It can be noted that the transition from the first generation mode in which 60% of the power is drawn from the HP shaft and 40% of the power is drawn from the LP shaft, to the second generation mode in which 100% of the power is drawn from the LP shaft, is no longer immediate, at a given time t0 as in the prior art, but is spread over a longer period (typically between 1 and 10 seconds) between a time t1 and a time t2 during which the power drawn from each shaft will gradually (and not abruptly) pass from its current level in the first generation mode to its future level in the second generation mode, without modification of the total power consumed by the electrical network.

[0040] The smoothing function f(t) which ensures this progressive rise is typically a linear function f(t)=Kt, K being a proportionality factor, or a first-order function of the type f(t)=l-exp (-t / tau), tau being a time constant. These two preferred types of function should not, however, be considered as limiting, a second-order function corresponding to the transfer function f(p) = l / (p 2 / w 2+ 2mp / w + 1) in the Laplace domain, m being a damping coefficient >= 1, is also possible, as is an application of these first and second order functions to the aforementioned linear function. More generally, any bounded monotone function [0; 1] continuous or discrete with f(tl)=O and f(t2) = 1 can be suitable. As mentioned previously, since this transition phase is no longer immediate, the case where a power extraction request arrives during this transient phase where the steady state has not yet been reached must be considered.

[0041] According to the invention, two sharing solutions are examined. The first illustrated in Figures 3 to 5 in which the difference in power demand is treated in the same way as the initial power demand, i.e. in proportion to the two modes according to the sharing function, while the second illustrated in Figures 6 to 8, the difference in power demand uses the second generation mode. It will be noted that if there is no change in demand during the transition, the two alternatives are equivalent.

[0042] In the first solution, it is therefore a question, when there is a load impact which occurs during the transition, of continuing to apply the sharing of the power draw which was defined.

[0043] Figure 3 shows the shape of the power setpoints obtained with this initial sharing. For example, if to deliver a total power PO, the initial power sharing is 60% on the HP shaft and 40% on the LP shaft and we want to go to 0% on the HP shaft and 100% on the LP shaft and if during the transition phase between time t1 and time t2, there is at a time ti a modification of the power demands of the consumers, for example an additional demand of 50% to arrive at a total power PI as illustrated, then in this case, the new power demand of the consumers will be taken at 60% on the HP shaft and 40% on the LP shaft at the point of application of the change in withdrawal.

[0044] This solution translates mathematically into the following equations:

[0045] With PO the power requested in the first generation mode (respectively on the HP shaft or the BP shaft) and PI the power requested in the second generation mode (respectively on the HP shaft or the BP shaft). Figure 4 illustrates the control logic implemented in the adaptation module to respond to this equation. It is conventionally organized around different functional blocks which will develop the current setpoint from the selected generation mode (Mode) and the evolution of the setpoint (setpoint vector): a mode change detection block 300, a transition inhibition block 302, a block for storing the old and new modes 304, a block for generating the old power setpoint 306, a block for generating the new power setpoint 308, a transition generation block 310 and a block for merging the old and new power setpoints 312.

[0046] The different steps allowing the transition from the first to the second generation mode are now illustrated in Figure 5. In a first step 400, the power setpoint on the HP shaft is at Xi% (for example 60%) of the consumed power and that on the LP shaft at yi% (for example 40%) of this consumed power, defining a requested power in the first generation mode PO. In a following step 402, at time tl, a request to change the generation mode in the power ratio is detected and the transition is then initiated by applying the smoothing function f(t) in a new step 404. In a following step 406, at time ti, a load impact AP (PI-PO) is observed due to an additional request to bring the power to the requested power in the second generation mode PI and this load impact is immediately passed on to the high and low pressure powers according to the initial power sharing.In the next step 408, the dynamics of the transition is resumed on the basis of the smoothing function until the end of the transition at time t2 and the steady state at power PI is obtained in a power ratio of x2% for high pressure and y2% for low pressure in a final step 410.

[0047] In the second solution, when there is a load impact that occurs during the transition (i.e. a change in the withdrawal setpoint), it is a matter of applying the sharing of the withdrawal powers that we want to achieve following the desired change in generation mode. Figure 6 shows the shape of the power setpoints obtained with this final sharing.For example, if to deliver a total power PO, the initial power sharing is 60% on the HP shaft and 40% on the LP shaft and we want to go to 0% on the HP shaft and 100% on the LP shaft and if during the transition phase, between time tl and time t2, there is at a time ti a modification of the power demands of the consumers, for example an additional demand of 50% to arrive at a total power PI as illustrated, then in this case, the new power demand of the consumers will be taken at 0% on the HP shaft and 100% on the LP shaft until reaching the steady state.

[0048] This solution translates mathematically into the following equations:

[0049] With PO the power requested in the first generation mode (respectively on the HP shaft or the BP shaft), PI the power requested in the second generation mode (respectively on the HP shaft or the BP shaft) and tl the instant of the mode change.

[0050] Figure 7 illustrates the control logic implemented in the adaptation module to respond to this equation. It is conventionally organized around different functional blocks which will develop the current setpoint from the selected generation mode (Mode) and the evolution of the setpoint (setpoint vector): the mode change detection block 300, the transition inhibition block 302, the old power setpoint generation block 306, the new power setpoint generation block 308, the transition generation block 310 and the old and new power setpoint merging block 312.

[0051] The different steps allowing the transition from the first to the second generation mode are now illustrated in Figure 8. In the first step 400, the power setpoint on the HP shaft is at Xi% (for example 60%) of the consumed power and that on the LP shaft at yi% (for example 40%) of this consumed power, defining a requested power PO. In the following step 402, at time tl, a request to change the generation mode in the power ratio is detected and the transition phase is then initiated by applying the smoothing function f(t), in the following step 404. In step 406, at time ti, a load impact AP (P1-P0) is observed due to an additional demand to bring the total power to the requested power in the second generation mode PI and this load impact is immediately passed on to the high and low pressure powers according to the final power sharing.In the next step 412, the dynamics of the transition is resumed on the basis of the smoothing function until the end of the transition at time t2 and the steady state is obtained at the requested power PI in a power ratio of x2% for high pressure and y2% for low pressure in the final step 410.

[0052] It will be noted that the invention finds application to the internal hybridization of turbomachines regardless of the number of electric machines mounted on the propulsion system and the type of turbomachine, such as a hybrid turbofan, a hybrid turboprop or a hybrid helicopter turbomachine.

Claims

Claims

1. Method for managing power transitions between a first generation mode and a second generation mode in a turbomachine (100) having a high pressure shaft (102) from which high pressure (HP) power is taken and a low pressure shaft (104) from which low pressure (LP) power is taken, the first generation mode corresponding to a first power sharing between the high pressure power and the low pressure power and the second generation mode corresponding to a second power sharing, different from the first, between the high pressure power and the low pressure power, the sum of the high and low pressure powers taken in each generation mode defining the same total power,characterized in that the transition between the first generation mode and the second generation mode takes place over a predetermined duration (t2-tl) without modification of the total power and by applying the same smoothing function f(t) to the sampling of both the high pressure power and the low pressure power.,

2. A method for managing power transitions according to claim 1, wherein the smoothing function f(t) is a continuous or discrete bounded monotonic function [0; 1] with f(tl)=0 and f(t2) = 1.

3. A method for managing power transitions according to claim 2, wherein the smoothing function f(t) is a linear function f(t) = Kt, K being a proportionality factor, or a first-order function of type f(t) = 1-exp (-t / tau), tau being a time constant.

4. A method for managing power transitions according to claim 1, wherein the predetermined duration (t2-tl) is between 1 and 10 seconds.

5. A method of managing power transitions according to any one of claims 1 to 4, wherein when an impact of load corresponding to an additional power draw (P) occurs during the transition, this additional draw is carried out at the moment of impact (ti) according to the first power sharing or according to the second power sharing, the smoothing function f(t) remaining applied upstream of this moment from a start (tl) of the transition and downstream of this moment until an end (t2) of the transition.

6. Method for managing power transitions according to claim 5, in which the additional power draw P carried out on each of the high or low pressure shafts according to the first power sharing satisfies the following equation: P = (1 - (t)) * P0(t) + (t) * P (t) with PO the power required in the first generation mode and PI the power required in the second generation mode.

7. Method for managing power transitions according to claim 5, in which the additional power draw P carried out on each of the high and low pressure shafts according to the second power sharing satisfies the following equation: power requested in the first generation mode, PI the power requested in the second generation mode and tl the instant of the mode change.

8. Turbomachine (100) having a high pressure shaft (102) from which a high pressure (HP) power is taken and a low pressure shaft (104) from which a low pressure (LP) power is taken, a first generation mode corresponding to a first power sharing between the high pressure power and the low pressure power and a second generation mode corresponding to a second power sharing, different from the first, between the high pressure power and the low pressure power, the sum of the high and low pressure powers taken in each generation mode defining the same total power, characterized in that the transition between the first generation mode and the second generation mode takes place during a predetermined duration (t2-tl) without modification of the total power and in applying the same smoothing function f(t) to the sampling of both high pressure power and low pressure power.

9. Turbomachine according to claim 8, further comprising an adaptation module (200) configured to generate the smoothing function f(t) and arranged between a control module (118) receiving power instructions from an ECU (120) and power converters (110, 112) associated with the electrical machines (106, 108) mounted on the high and low pressure shafts.

10. Turbomachine according to claim 9, constituted as an aeronautical turbomachine such as a hybrid turbofan, a hybrid turboprop or a hybrid helicopter turbomachine.

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