Method for managing power transitions between a generation mode and an assistance mode

Abstract

The invention relates to a method for managing power transitions between a generation mode and an assistance mode in a turbine engine having a high-pressure shaft which drives a high-pressure electric machine and from which high-pressure power (PHP) is drawn and a low-pressure shaft which drives a low-pressure electric machine and from which low-pressure power (PBP) is drawn, the generation mode corresponding to determined power sharing between the high-pressure power and the low-pressure power and the assistance mode corresponding to a request for injection of an additional power on the high-pressure shaft or the low-pressure shaft, in which method, in order to achieve the requested additional power, when the drawing of high- or low-pressure power is interrupted and the high- or low-pressure electric machine driving the high- or low-pressure shaft, respectively, the drawing of high- or low-pressure from which is interrupted, is put into motor mode, the remaining power drawn from the high- or low-pressure shaft in generator mode is adjusted from the high- or low-pressure injected power output by the high- or low-pressure electric machine that has passed into motor mode.

Description

[0001] Description

[0002] Title of the invention: Method for managing power transitions between a generation mode and an assistance mode

[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 but also the controlled power draw from the turbomachine shafts when the turbomachine is operating in assistance mode. 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] More precisely, when the turbomachine requests assistance, a source which participates in the regulation of the generation voltage stops its participation in the generation and goes into motor mode. This switching of operating mode causes a strong fluctuation of the voltage which then deviates from the predefined voltage gauges (figure 5) defining the limits not to be exceeded both in transient and in steady state for both normal 500 and abnormal operation (with a problem on the network, i.e. short circuit) 502 of the turbomachine.

[0012] To control this voltage and keep it within these limits, it is known to resort either to load shedding (for example non-priority loads) by temporarily reconfiguring the electrical system, or to an external source (associated or not with temporary load shedding) having a greater dynamic than that of the turbomachine sources to provide the high frequency (HF) part of the power to be generated, or even to oversizing certain passive components of the electrical system such as the capacitors of the power electronics.

[0013] However, these solutions are not without drawbacks. Load shedding does not involve any anticipation of consumption or the behavior of the electrical network, and the addition of an external source is based solely on a frequency sharing of the power generated between the turbomachine and this external source, the turbomachine still only providing average power. Finally, the oversizing of the systems is penalizing in terms of mass and is therefore hardly desirable for an aeronautical application.

[0014] Statement of the invention

[0015] To this end, the invention is the result of technological research aimed at very significantly improving the performance of aircraft and, in this sense, contributes to reducing the environmental impact of these aircraft. For this purpose, the present invention therefore has the main aim of limiting the strong voltage fluctuations when the turbomachine switches to an assistance mode, by anticipating the sudden variation in the available power and without penalizing the on-board mass, while respecting the quality constraints of the electrical network.

[0016] These aims are achieved by a method for managing power transitions between a generation mode and an assistance mode in a turbomachine having a high-pressure shaft driving a high-pressure electric machine and from which high-pressure power is taken and a low-pressure shaft driving a low-pressure electric machine and from which low-pressure power is taken, the generation mode corresponding to a determined sharing of power between the high-pressure power and the low-pressure power and the assistance mode corresponding to a request for injection of additional power on the high-pressure shaft or the low-pressure shaft, characterized in that to achieve the requested additional power,when the high or low pressure power draw is interrupted and the high or low pressure electrical machine driving respectively the high or low pressure shaft whose draw is interrupted goes into motor mode, the remaining drawn power from the high or low pressure shaft in generator mode is adjusted from the high or low pressure injected power from the high or low pressure electrical machine switched to motor mode.,

[0017] Thus, by sending to the source which is in generation mode, the power requested by the source which switches to assistance mode, we anticipate this request, we limit the voltage variation and we control the transient while containing the voltage within the defined limits.

[0018] Preferably, if the high or low pressure electrical machines have different dynamics, the injection of the additional power requested is done by adapting the dynamics of the withdrawal of the remaining high or low pressure power taken.

[0019] The invention also relates to 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, a control module receiving power setpoints from an ECU and power converters associated with high and low pressure electrical machines mounted respectively on the high and low pressure shafts, a generation mode corresponding to a determined sharing of power between the high pressure power and the low pressure power and an assistance mode corresponding to the injection of additional power on the high pressure shaft or the low pressure shaft, characterized in that to achieve the requested additional power, the control module is configured so that,when the high or low pressure power draw is interrupted and the high or low pressure electrical machine driving respectively the high or low pressure shaft whose draw is interrupted goes into motor mode, the remaining drawn power of the high or low pressure shaft in generator mode is adjusted from the high or low pressure injected power from the high or low pressure electrical machine switched to motor mode. Preferably, the control module further comprises assistance modules configured to add the high or low pressure injected power to the remaining high or low pressure drawn power and a selection module configured to select the drawn powers from the assistance modules.,

[0020] Advantageously, each of the assistance modules comprises an adder and an adaptation module having a transfer function Fl, F2 to adapt the dynamics of the remaining high or low pressure power taken according to the respective dynamics of the high and low pressure electrical machines.

[0021] According to the dynamics of electric machines, the transfer functions are equal to 1 if the high and low pressure electric machines have the same dynamics, are phase lags if the dynamics of the electric machine that switches to motor mode is slower than that which remains in generator mode, or are phase advance functions if the dynamics of the electric machine that switches to motor mode is faster than that which remains in generator mode.

[0022] Brief description of the drawings

[0023] 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:

[0024] [Fig. 1] Figure 1 illustrates an architecture of an internal hybridization system of a turbomachine according to the invention,

[0025] [Fig. 2] Figure 2 details the innovative control module of the internal hybridization system of Figure 1,

[0026] [Fig. 3] Figure 3 illustrates the instructions for drawing power associated with a request for assistance,

[0027] [Fig. 4] Figure 4 shows the different steps of the process implemented in the internal hybridization system of Figure 1, and [Fig. 5] Figure 5 shows an example of voltage templates applicable to the internal hybridization system of Figure 1.

[0028] Description of the embodiments

[0029] When assistance is requested, an electrical source of the turbomachine that participates in the regulation of the generation voltage stops doing so and switches to engine mode to inject the necessary power and ensure the assistance function for the turbomachine. Since the remaining sources have a certain response time, by the time they reconfigure to provide the missing power, the generation voltage decreases sharply and goes beyond the limits of the imposed templates, especially since the balance between generated power and consumed power is no longer satisfied.

[0030] To overcome this problem, the invention proposes to act on the control module of the remaining sources to modify its behavior after the request for assistance from the turbomachine, so that the transient of the generation voltage remains contained within the predefined templates.

[0031] Figure 1 illustrates an example of architecture of the internal hybridization systems of a turbomachine 100 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 operated 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 busbar 114 connected to the loads 116 to be powered (propulsive 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) which controls the thermal engine and therefore has the particular function of adapting the percentages of participation of the electrical machines in the generation of power to optimize the operating point of the turbomachine.

[0032] To do this, the ECU 120 will ask the control module 118 to share the draw power between the HP and LP shafts to supply the loads 116 which consume a power L from the network which generally have dynamic behaviors which can be variable, in particular the so-called active loads.

[0033] As shown in Figure 2, this determined sharing of the power draws between the HP and LP shafts requested by the ECU which, for example, is initially in a generation mode in which 60% of the power L is drawn from the HP shaft and 40% of the power L is drawn from the LP shaft, can, to achieve the additional power required by the assistance request, switch to an assistance mode in which the high-pressure power draw from the HP shaft is interrupted, the high-pressure electric machine switching to motor mode to inject high-pressure power, and 100% of the power L then being supplied by the LP shaft plus the load requested by the HP shaft, as illustrated in this figure.

[0034] However, when switching to assistance mode, due to this instantaneous change in the power ratio, the transient power supplied 130 and the desired power 140 diverge. It is therefore necessary to find a way to compensate for the difference between the transient power supplied by the remaining sources and the desired power in order to contain the generation voltage within the predefined limits until reaching steady state without adding an external source.

[0035] More explicitly, this transient power difference is translated by the following equation (1):

[0036] With C: value of the power capacitors on the DC bus

[0037] ■ Ps: power of the sources

[0038] ■ PI: power of the loads

[0039] ■ Wc: energy in power capacitors

[0040] Since it is not possible to consider increasing the size of the capacitors of the power electronics, which would lead to oversizing the system, nor to accelerate the voltage and current control loops, which would involve constraints on the control chain (computer cycle time, command delays, speeds of the power electronics, etc.), the invention proposes adding functions in the control module 118 ensuring the regulation of the generation voltage in order to limit its variation during requests for assistance from the turbomachine and to maintain it within the variation ranges defined by the templates. The mass is thus optimized because there is no addition of an external source or oversizing of the capacitors of the power electronics responsible for storing the electrical energy.

[0041] Figure 3 details the components forming the control module 118 thus modified which comprises, in addition to a voltage regulation module 200 delivering the predefined voltage templates or the power P necessary to guarantee them, a mode generation module 202 to which it is connected and which receives the power instructions from the ECU 120 and develops the sharing of the powers of the load L between the HP and LP shafts, two assistance modules associated, one 204 with the high pressure shaft and the other 206 with the low pressure shaft and configured to add the low injected power P B P OR high P H P pressure respectively at the remaining high P p or low pressure P taken power B P respectively, and a selection module 208 configured to select the taken powers P BP and P HP from the mode generation module or the assistance modules from the power MODE from the ECU 120. Each of the assistance modules comprises an adder 300, 302 to quantify the powers to be generated in addition on one side and to be taken from the other side and an adaptation module 304, 306 having a transfer function Fl, F2 which depends on the dynamics of the associated electrical machine. For example, if the ECU requests a negative power (PBP in motor mode) from the BP shaft then, for the calculation of P H P, the adder subtracts this negative power P B p to the input power P to the assistance module 204, i.e. at 100% of the load power because P B P has switched to motor mode. At output P H P is equal to P + P BP .

[0042] The transfer functions Fl and F2 are used to adapt the dynamics of the power taken from the remaining machine to the dynamics of the machine that has switched to motor mode in order to anticipate its power requirements. Depending on the case, Fl and F2 can be equal to:

[0043] - the unit if the two machines installed on the HP shaft and the LP shaft have the same dynamics,

[0044] - a phase delay, or any function allowing the response of the remaining machine to be slowed down, for example a first-order transfer function, if the dynamics of the machine which switches to motor mode is slower than the machine which remains in generator mode,

[0045] - a phase advance function, if the dynamics of the machine switching to motor mode is faster than the remaining machine.

[0046] Figure 4 illustrates the different stages of the process implemented in the control module.

[0047] In a first step 400, the system is in a normal operating regime in generation mode with a sharing of the powers taken between the high pressure shaft and the low pressure shaft. In the following step 402, a request for operation in assistance mode is made and, for example, the high pressure electrical machine (i.e. the one driving the high pressure shaft) which was in generator mode in the normal operating mode (which is interrupted) switches to motor mode. In a new step 404, the assistance module associated with the high pressure shaft comes into action to communicate the high pressure power to the low pressure shaft before in a final step 406 the power taken by the low pressure shaft is adjusted from this high pressure power to reach the additional power requested by the assistance mode.

[0048] 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 generation mode and an assistance mode in a turbomachine (100) having a high pressure shaft (102) driving a high pressure electric machine (106) and from which high pressure (HP) power is taken and a low pressure shaft (104) driving a low pressure electric machine (108) and from which low pressure (LP) power is taken, the generation mode corresponding to a determined sharing of power between the high pressure power and the low pressure power and the assistance mode corresponding to a request for injection of additional power on the high pressure shaft or the low pressure shaft, characterized in that to achieve the requested additional power,when the high or low pressure power draw is interrupted and the high or low pressure electrical machine driving respectively the high or low pressure shaft whose draw is interrupted goes into motor mode, the remaining drawn power from the high or low pressure shaft in generator mode is adjusted from the high or low pressure injected power from the high or low pressure electrical machine switched to motor mode.,

2. Method for managing power transitions according to claim 1, in which if the high or low pressure electrical machines have different dynamics, the injection of the additional power requested is done by adapting the dynamics of the withdrawal of the remaining high or low pressure power taken.

3. 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, a control module (118) receiving power instructions from an ECU (120) and power converters (110, 112) associated with high (106) and low (108) pressure electrical machines mounted respectively on the high and low pressure shafts, a generation mode corresponding to a determined sharing of power between the high pressure power and the low pressure power and an assistance mode corresponding to the injection of additional power on the high pressure shaft or the low pressure shaft, characterized in that to achieve the requested additional power, the control module (118) is configured so that, when the high or low pressure power draw is interrupted and the high or low pressure electrical machine driving respectively the high or low pressure shaft whose draw is interrupted goes into motor mode, the remaining power drawn from the high or low pressure shaft in generator mode is adjusted from the high or low pressure injected power from the high or low pressure electrical machine switched to motor mode.

4. A turbomachine according to claim 3, wherein the control module further comprises assistance modules (204, 206) configured to add the high or low pressure injected power to the remaining high or low pressure drawn power and a selection module (208) configured to select the drawn powers from the assistance modules.

5. Turbomachine according to claim 4, in which each of the assistance modules comprises an adder (300, 302) and an adaptation module (304, 306) having a transfer function F1, F2 for adapting the dynamics of the remaining high or low pressure power taken according to the respective dynamics of the high and low pressure electrical machines.

6. Turbomachine according to claim 5, in which the transfer functions are equal to 1 if the high and low pressure electric machines have the same dynamics.

7. A turbomachine according to claim 5, wherein the transfer functions are phase delays if the dynamics of the electric machine which switches to motor mode is slower than that which remains in generator mode.

8. A turbomachine according to claim 5, wherein the transfer functions are phase advance functions if the dynamics of the electric machine which switches to motor mode is faster than that which remains in generator mode.

9. A turbomachine according to any one of claims 3 to 8, constituted as an aeronautical turbomachine such as a hybrid turbofan, a hybrid turboprop or a hybrid helicopter turbomachine.

Images