Electrically powered agricultural machine with power management system

Abstract

A power management system (300) for an electrically powered agricultural machine (100) equipped with an electric energy storage (304), a power distribution unit (302), a first electric motor (310) and a first electric consumer (310) can determine an energy excess (812) if net electric energy (800) exceeds a maximum charge power of the electric energy storage (304). The net electric energy (800) is a difference between supplied electric energy and consumed electric energy of the power management system (300).

Description

ELECTRICALLY POWERED AGRICULTURAL MACHINE WITH POWER MANAGEMENT SYSTEMFIELD

[0001] The present disclosure relates generally to an electrically powered agricultural machine.BACKGROUND

[0002] Electrically powered agricultural machines may be configured as a battery electric vehicle (BEV) or hybrid electric vehicle (HEV). They comprise one or more electric energy sources such as a battery, a generator or a fuel cell. The electric energy sources provide electric energy to at least one electric motor to propel the agricultural machine and to operate other electric consumers such as a fan or an electric heater. The electric components are electrically connected by a common link. The at least one electric motor may be operated in a generator mode for recuperative braking of the agricultural machine. One of the electric energy sources is configured to be operable as a buffer and can be charged by electric energy, as for example a battery or a capacitor. This buffer can be charged if more electric energy is supplied than consumed. Under certain circumstances, for example in case of an emergency braking of the agricultural machine, the supplied electric energy may exceed a maximum charge power of the buffer. Under other circumstances, the electric energy consumed may exceed a maximum discharge power of the buffer. Anyway, if the maximum charge power or the maximum discharge power of the buffer is exceeded by a certain amount, the buffer may disconnect from the common link for protection reasons. All other electric components that remain connected may possibly be damaged.BRIEF SUMMARY

[0003] Hence, it is an objective to provide an electrically powered agricultural machine that is configured to avoid a buffer to be disconnected or other electric components to be damaged due to an exceedance of a maximum charge power or maximum discharge power of the buffer.

[0004] According to an aspect of the invention there is provided an electrically powered agricultural machine comprising a power management system. The power management system comprises a power distribution unit electrically connected with an electric motor and a first electric consumer. The electric motor is configured to be operated in a motor mode to convert electric energy into a torque (rotational mechanical energy), and in a generator mode to convert a torque (rotational mechanical energy) into electric energy. The electrically powered agricultural machine further comprises an electric energy storage electrically connected with the power distribution unit and configured to supply electric energy to the electric motor, and to be charged by electric energy received from the electric motor. A maximum charge power of the electric energy storage is smaller than a maximum energy supply of the power management system. A maximum discharge power of the electric energy storage is smaller than a maximum energy consumption of the power management system. The power distribution unit is configured to determine an energy excess if net electric energy exceeds the maximum charge power of the electric energy storage. The net electric energy is a difference between supplied electric energy and consumed electric energy of the power management system.

[0005] The agricultural machine may be an agricultural vehicle such as a tractor, a harvester, a combine, a sprayer, etc., optionally connected with an implement. The vehicle may be configured as a battery electric vehicle (BEV) or hybrid electric vehicle (HEV) having an additional prime mover such as an internal combustion engine. The electric motor may be operated in generator mode during recuperative braking of the agricultural machine. The electric energy storage may be a passive energy storage such as a battery or a capacitor without any active control of the (de-)charge power. The electric energy storage may supply the electric motor, the first electric consumer and any other electric consumer of the agricultural machine with electric energy. The power distribution unit may comprise a control unit to control any electric components of the agricultural machine such as the electric motor (e. g. the inverter) or any electric consumer. For example, the power distribution unit may automatically switch on or off any electric consumer or may control any parameter of an electric consumer such as speed, torque or consumption of electric energy. Any component of the agricultural machine configured to provide or consume electric energy except the electric energystorage may be part of the power management system. So, the maximum energy supply of the power management system may depend on the electric energy supplied by the electric motor (when operated in generator mode) and any other component of the power management system configured to supply electric energy. Analogously, the maximum energy consumption of the power management system depends on the electric energy consumed by the electric motor (when operated in motor mode) and any other component of the power management system configured to consume electric energy. The electric energy storage may be used as a buffer to compensate electric imbalances within the power management system. Under specific circumstances, as for example recuperative braking, electric imbalances may exceed the maximum charge power of the electric energy storage and thus cause an energy excess. To avoid that the energy excess may cause an unintended disconnection of the electric energy storage or damage of any one of the electric components of the agricultural machine, the power distribution unit may detect an energy excess and initiate a protective action in response to the detected energy excess.

[0006] The power distribution unit may be configured to determine an energy shortage if net electric energy exceeds the maximum discharge power of the electric energy storage.

[0007] Under specific circumstances, as for example excessive acceleration of the agricultural machine, electric imbalances may exceed the maximum discharge power of the electric energy storage and thus cause an energy shortage. To avoid that the energy shortage may cause an unintended disconnection of the electric energy storage or damage of any one of the electric components of the agricultural machine, the power distribution unit may detect an energy shortage and initiate a protective action in response to the detected energy shortage. Consequently, the power distribution unit is configured to initiate actions in case of an energy shortage as well as energy excess to keep the electric energy drawn from or supplied to the electric energy storage between the maximum discharge power and the maximum charge power of the electric energy storage.

[0008] The power distribution unit may be configured to increase the net electric energy in case of an energy shortage.

[0009] The increase of net electric energy may provide more electric energy for compensating the energy shortage. The power distribution unit may control the components of the power management system to increase the net electric energy by increasing the supply of electric energy or by reducing the consumption of the electric energy.

[0010] The power distribution unit may be configured to decrease consumption of electric energy of the electric motor or the first electric consumer to increase net electric energy.

[0011] For example, the power distribution unit may control the electric motorto reduce the speed and / or the torque or control the first electric consumer to operate with less power.

[0012] The power management system may comprise an electric energy source. The power distribution unit may be configured to increase supply of electric energy by the electric energy source to increase net electric energy.

[0013] The electric energy source may be an energy source in addition to the electric energy storage. The electric energy source may be a fuel cell or any other type of (nonpassive) electric energy source controllable by the power distribution unit. The power distribution unit may control the electric energy source to produce more electric energy to increase supply of electric energy.

[0014] The power distribution unit may be configured to decrease net electric energy in case of an energy excess.

[0015] The decrease of net electric energy may increase the consumption of electric energy for compensating the energy excess. The power distribution unit may control the components of the power management system to decrease the net electric energy by decreasing the supply of electric energy or by increasing the consumption of the electric energy.

[0016] The power distribution unit may be configured to increase consumption of electric energy of the first electric consumer to decrease net electric energy.

[0017] For example, the power distribution unit may control the first electric consumer to operate with more power or to increase lost energy.

[0018] The electrically powered agricultural machine may comprise an electric energy source. The power distribution unit may be configured to decrease supply of electric energy by the electric energy source to decrease the net electric energy.

[0019] The electric energy source may be the same electric energy source as mentioned above or an additional energy source. The power distribution unit may control the electric energy source to produce less electric energy to decrease supply of electric energy.

[0020] The electrically powered agricultural machine may comprise another electric consumer. A short-time maximum energy consumption of the first electric consumer may be greater than a short-time maximum energy consumption of the other electric consumer and a long-time maximum energy consumption of the other electric consumer may be greater than a long-time maximum energy consumption of the first electric consumer.

[0021] Hence, the power distribution unit may control the first electric consumer to compensate a short-time energy excess and may control the other electric consumer, optionally in addition to the first electric consumer, to compensate a long-time energy excess.

[0022] The power distribution unit may be configured to determine a short-time energy excess if net electric energy is greater than the maximum charge power of the electric energy storage for a predefined time period, and a long-time energy excess if net electric energy is greater than the maximum charge power of the electric energy storage for a time period longer than the predefined time period.

[0023] When an energy excess has been detected by the power distribution unit, the power distribution unit may initiate a protective action in response to the detected energy excess. But the protective action may not be sufficient to compensate the energy excess completely after the predefined time period has been elapsed. Hence, the power distribution unit may initiate other or additional protective actions for compensating an energy excess lasting longer than the predefined time period. So, the power distribution unit can initiate different protective actions in dependence of the duration of the energy excess.

[0024] The power distribution unit may be configured to increase consumption of electric energy of the first electric consumer in case of a short-time energy excess, andincrease consumption of electric energy of the other electric consumer in case of a long-time energy excess.

[0025] The first electric consumer may have better dynamics compared to the other electric consumer so that the energy excess can be reduced or compensated more quickly by initiating the first electric consumer first. Since the maximum energy consumption of the first electric consumer may not be sufficient to completely compensate the energy excess for a longer period of time, the power distribution unit initiates the other electric consumer to support the first electric consumer for compensating the energy excess. When the consumption rate of the other electric consumer has reached a value sufficient to compensate the long-time energy excess, the power distribution unit may control the first electric consumer to reduce the energy consumption so that not more energy than required is consumed.

[0026] The power distribution unit may be configured to increase consumption of electric energy of the other electric consumer in case of a long-time energy excess before the predefined time period elapses.

[0027] The other electric consumer may have poor dynamics. Thus, the earlier the other electric consumer is initiated by the power distribution unit the earlier the maximum consumption rate of the other electric consumer is reached. For example, the power distribution unit may initiate both the first electric consumer and the other electric consumer simultaneously when an energy excess has been detected. The power distribution unit may switch off the other electric consumer again if the energy excess is a short-time energy excess only or keep the other electric consumer activated if the energy excess lasts longer than the predefined time period.

[0028] The power distribution unit may be configured to increase consumption of electric energy of the other electric consumer to a maximum value before the predefined time period elapses.

[0029] For example, the power distribution unit may initiate the other electric consumer early enough so that (irrespective of poor dynamics of the other electric consumer) the consumption rate of the other electric consumer has already reached a maximum value when the predefined time period elapses. Hence, poor dynamics of the other electric consumer may not have a negative impact for compensating a long-time energy excess.

[0030] The predefined time period may be a time period of equal or less than 1 second.

[0031] The predefined time period may be stored in the memory of the power distribution unit (control unit). The predefined time period may be adjustable by the power distribution unit. The power distribution unit may set any value between 0 and 1 seconds to define the predefined time period, for example 0.75 seconds.

[0032] The predefined time period may depend on a ramp down rate of the electric motor and / or of the electric energy source.

[0033] The ramp down rate of the electric motor may depend on vehicle kinematics and / or a configured deceleration rate of the vehicle. The ramp down rate of the electric energy source, for example the fuel cell, may depend on the duration needed to reduce the energy supply from a maximum value to zero. I. e., the ramp down rate depends on the dynamics of the corresponding component. The better the dynamics of the electric motor or the electric energy source is, the shorter may be the predefined time period. The ramp down rate may be stored in the memory of the power distribution unit (control unit).

[0034] The other electric consumer may be a fan, a PTC resistance or a retarder.

[0035] The fan may blow air for cooling any electric component. Alternatively, the fan may blow air tempered by an air conditioner into a cabin of the agricultural machine. The PTC resistance may be used as a heater to heat up the cabin or liquid that is used for thermal management of any electric component of the agricultural machine. The retarder may be an electronically controllable hydraulic retarder in mechanical connection with the electric motor to decelerate the speed of the agricultural machine. The power distribution unit may control the fan, the PTC resistance and / or the retarder to increase or decrease the electric energy consumed by the corresponding electric consumer. For example, the power distribution unit may control a speed of the fan, a heating power of the PTC resistance and / or a braking power of the retarder to control the energy consumption. The hydraulic retarder may be considered as an indirect electric consumer since the electric energy consumption caused by the retarder is effected by the electric motor.

[0036] The first electric consumer may be a brake resistor.

[0037] The dynamics of the brake resistor may be very high so that the consumption rate of the resistor may raise very quickly from zero to a maximum value. The first electric consumer may be an alternative consumer having dynamics similar to a brake resistor. The power distribution unit may control the first electric consumer to adjust the dynamics and / or the maximum consumption rate of the first electric consumer.

[0038] A sum of the maximum charge power of the electric energy storage and the maximum energy consumption of the first electric consumer may be smaller than a maximum energy supply of each electric energy source of the power management system.

[0039] To reduce weight and / or production cost of the agricultural machine, the agricultural machine may be equipped with smaller, downsized and therefore cheaper components. For example, the usage of a downsized battery may save much money. Due to downsizing, the electric energy storage and the first electric consumer may consume in combination less electric energy than the fuel cell as electric energy source of the power management system may be configured to provide. Hence, another electric consumer in addition to the first electric consumer may be required for compensation of an energy excess as described above.

[0040] Another aspect includes a method of controlling a power management system of an electrically powered agricultural machine comprising an electric energy storage, a power distribution unit, a first electric motor and a first electric consumer. The method comprises determining an energy excess if net electric energy exceeds the maximum charge power of the electric energy storage. The net electric energy may be a difference between supplied electric energy and consumed electric energy of the power management system.

[0041] The method may be carried out by the power distribution unit (control unit) to initiate at least one protective action in response to the detected energy excess. Hence, an unintended disconnection of the electric energy storage or damage of any one of the electric components of the agricultural machine due to an energy excess can be prevented by the power distribution unit. Each action may be implemented as one or more method steps of the method executable by the control unit. Hence, each action for which the control unit is configured to execute may be defined as a method step.

[0042] Within the scope of this application it should be understood that the various aspects, embodiments, examples and alternatives set out herein, and individual features thereof may be taken independently or in any possible and compatible combination. Where features are described with reference to a single aspect or embodiment, it should be understood that such features are applicable to all aspects and embodiments unless otherwise stated or where such features are incompatible.BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Several aspects of the invention will now be described, byway of example only, with reference to the accompanying drawings, in which:

[0044] FIG. 1 illustrates an agricultural machine.

[0045] FIG. 2 illustrates a simplified view of a control unit.

[0046] FIG. 3 illustrates a schematic block diagram of the agricultural machine.

[0047] FIG. 4 illustrates a schematic block diagram of a power management system.

[0048] FIG. 5 illustrates a diagram with consumption rates of different consumers.

[0049] FIG. 6 illustrates a diagram with consumption rates of different consumers.

[0050] FIG. 7 illustrates a diagram with a supply rate of a fuel cell and a consumption rate / supply rate of an electric motor.

[0051] FIG. 8 illustrates a diagram indicating an imbalance between consumed electric energy by the electric motor and supplied electric energy by the fuel cell.

[0052] FIG. 9 illustrates a diagram of an electric energy demand violating an energy corridor.

[0053] FIG. 10 illustrates diagrams defining upper energy limits.

[0054] FIG. 11 illustrates diagrams defining lower energy limits.

[0055] FIG. 12 illustrates a flow chart of a method executable by the control unit of FIG. 2.

[0056] FIG. 13 illustrates a diagram of an electric energy demand within an energy corridor.

[0057] FIG. 14 illustrates a diagram with consumption rates of different consumers.

[0058] FIG. 15 illustrates a diagram of an electric energy demand within an energy corridor.

[0059] FIG. 16 illustrates a diagram with consumption rates of different consumers.DETAILED DESCRIPTION

[0060] FIG. 1 shows an electrically powered agricultural machine 100 comprising front wheels 102 and rear wheels 104. An electric motor 318 (see FIG. 3) installed in the agricultural machine 100 may generate a tractive force to propel the front and / or rear wheels 102, 104. The agricultural machine 100 may be a vehicle or a vehicle-implement combination. The implement may be fixed to the vehicle or detachably connected with the vehicle. The vehicle may be an agricultural vehicle such as a tractor, a harvester, a combine, a sprayer or of any other type such as a truck. The implement may be used for an operation in an agricultural field and may be of the type of a plough, a rake, a planter, a sprayer, a mower, a trailer, etc. Depending on the type of the implement, the implement may comprise one or more tools such as a rake rotor, a mower knife, a seeding unit, a spray nozzle, a shovel, a dumper, etc.

[0061] The agricultural machine 100 comprises a cabin 108 for an operator to sit in the agricultural machine 100 and to manually control the agricultural machine 100. On top of the cabin 108, there are attached five tanks 110 arranged in an enclosure 112. The tanks 110 may store a fuel such as hydrogen or methane. The fuel may be delivered to a fuel cell 306 (see FIG. 3) to generate electric energy for the electric motor 318 to provide the tractive force. The fuel cell 306 and the electric motor 318 are covered by a hood 106 of the agricultural machine 100.

[0062] The agricultural machine 100 comprises also a control unit 114. The control unit 114 as shown in FIG. 2 in more detail may be installed anywhere in the agricultural machine 100, for example under the hood 106.

[0063] FIG. 2 shows the control unit 114 comprising an I / O interface 202, a controller 204 and a memory 206. The I / O interface 202, the controller 204 and the memory 206 may be attached to a printed circuit board (PCB). The control unit 114 may receive and send signals or data via the I / O interface 202. The I / O interface 202 may be a wireless interface or a connector. The controller 204 may store the data or signals received by the control unit 114 in the memory 206. The memory 206 may contain additional data orexecutable computer program products, for example in terms of a computer- implemented method, that may be retrieved, processed or executed by the controller 204. Data or signals resulting from the processing of data or signals or from the execution of a computer program product may be stored to the memory 206 or sent to the I / O interface 202 by the controller 204.

[0064] FIG. 3 shows a simplified block diagram of the agricultural machine 100 shown in FIG. 1 . Additionally to the components shown in FIG. 1 , the agricultural machine 100 comprises several components that are electrically connected with each other such as a power distribution unit 302 (PDU), an electric energy storage 304 (e. g. a battery), the fuel cell 306, a DC / DC converter 308 arranged between the fuel cell 306 and the power distribution unit 302, a first electric consumer 310, a second electric consumer 312, an inverter 314, the electric motor 318, a third electric consumer 316, a fourth electric consumer 322, another DC / DC converter 326 connected with a first on-board power supply 328, another DC / DC converter 330 connected with a second on-board power supply 332, an on-board charging device 334, and additional consumers such as an AC compressor 340, and an air compressor 342. As schematically illustrated in FIG. 4, the fuel cell 306, the electric motor 318, the power distribution unit 302 and the first to fourth electric consumers 310, 312, 316, 322 are part of a power management system 300 configured to control these components and to balance the electric energy distributed between these components.

[0065] The control unit 114 is integrated in the power distribution unit 302 and can send and / or receive electrical signals via the I / O interface 202 to / from the components connected with the power distribution unit 302 (see FIG. 3). Alternatively, the control unit 114 can be arranged external to the power distribution unit 302.

[0066] The inverter 314 is electrically connected with the electric motor 318 and controls the modes of operation of the electric motor 318. When the electric motor 318 is operated in a motor mode, the electric motor 318 converts electric energy into mechanical energy for providing a torque to drive a transmission 320 mechanically coupled to the electric motor 318. The transmission 320 may be an automatic gearbox such as a continuous variable transmission (CVT). From the transmission 320, the torque is transferred to the front and / or rear wheels 102, 104 to drive the agricultural machine 100. When the electric motor 318 is operated in a generator mode, the electricmotor 318 converts a torque transferred from the transmission 320 into electric energy. The electric motor 318 may be operated in generator mode for recuperative braking of the agricultural machine 100. The electric energy generated by the electric motor 318 operated in generator mode may be used to supply any electric component of the agricultural machine 100 and / or to charge the electric energy storage 304. 1, e., the electric motor 318 as well as the electric energy storage 304 or the fuel cell 306 may be used as an electric energy source.

[0067] The first electric consumer 310 is a brake resistor to consume excessive electric energy generated by the electric motor 318 operated in generator mode that cannot be saved by the electric energy storage 304. The first electric consumer 310 may protect the power management system 300 from damage in error cases, for example in a load drop scenario. The second electric consumer 312 is a fan for cooling electric components and protect them against overheating. The third electric consumer is a positive temperature coefficient (PTC) resistance installed in the cabin 108 and used for climatization of the cabin 108 (heating) togetherwith the AC compressor 340. The fourth electric consumer 322 is an indirect electric consumer in terms of a retarder mechanically coupled to the electric motor 318 via the transmission 320 for decelerating the agricultural machine 100 by providing a brake torque for brakingthe wheels. The brake torque induced by the fourth electric consumer 322 has effect on the electric motor 318 to consume electric energy.

[0068] The additional DC / DC converters 326 and 332 connected with the power distribution unit 302 may provide different voltage values for the first on-board power supply 328 and the second on-board power supply 332. For example, the first on-board power supply 328 may provide 12 V and the second on-board power supply 332 may provide 24 V. Additionally, a charging receptacle 336 is connected via a 3-phase onboard charging device 334 (OBC) with the power distribution unit 302. The charging receptacle 336 may be connected with an external electric energy source, e. g. a wallbox, to supply the power distribution unit 302 with electric energy and to charge the electric energy storage 304.

[0069] The tanks 110 are fluidly connected with the fuel cell 306 and a refilling receptacle 338 by means of a hydraulic line. Via the refilling receptacles 338, the tanks 110 can be refilled with fuel at a gas station. From the tanks 110, the fuel can bedelivered via the hydraulic line to the fuel cell 306. A pressure reduction valve 324 arranged in the hydraulic line between the fuel cell 306 and the tanks 110 can be used to adjust the pressure level of the fuel delivered to the fuel cell 306. For example, a pressure of 700 bar within the tanks 110 may be reduced to 12 bar when hydrogen is provided to the fuel cell 306. The fuel cell 306 can convert the chemical energy of the fuel into electric energy to supply any electric component of the agricultural machine 100 and / or to charge the electric energy storage 304. The DC / DC converter 308 arranged between the fuel cell 306 and the power distribution unit 302 converts the voltage of the electric current provided by the fuel cell 306 to a voltage value of the electric energy storage 304, as for example any value between 550 V to 750 V. The fuel cell 306 may be a proton exchange membrane (PEM) fuel cell.

[0070] FIG. 4 schematically illustrates by way of example the electrical design of the electric energy storage 304 and some of the components of the power management system 300. The electric energy storage 304 may have a capacity of 25 kWh, can provide a maximum discharge power of 70 kW and can be charged with a maximum charge power of 40 kW. The fuel cell 306 can provide a maximum of 100 kW and may deliver a minimum power of 15 kW. The electric motor 318 can provide 15 kW in generator mode and consume 100 kW in motor mode. The first electric consumer 310 can consume a maximum of 70 kW. The second electric consumer 312 can consume a maximum of 10 kW, the third electric consumer 316 can consume a maximum of 6 kW and the fourth electric consumer 322 can consume a maximum of 30 kW. The power distribution unit 302 distributes the electric energy provided or consumed by the different components (including the electric energy storage 304) so that the sum of the consumed electric energy is equal to the sum of provided electric energy within the power management system 300.

[0071] The electric components of the power management system 300 have also different dynamics in terms of rates of consuming electric energy (consumption rates) and / or rates of providing electric energy (supply rates). The dynamics of the electric energy storage 304 is similar to the dynamics of a battery, capacitor or resistor which is nearly infinitely fast. The diagrams of FIG. 5 and FIG. 6 illustrate exemplarily consumption rates of the first to fourth electric consumers 310, 312, 316, 322. Consumption rate 502 shows the dynamics of the first electric consumer 310representative for a brake resistor. Consumption rate 504 shows the dynamics of the second electric consumer 312 representative for a fan. Consumption rate 506 shows the dynamics of the third electric consumer 316 representative for a PTC resistor. Consumption rate 508 shows the dynamics of the fourth electric consumer 322 representative for a retarder. The diagram of FIG. 7 refers to the dynamics of the fuel cell 306 and the electric motor 318.

[0072] Next to the electric energy required by a component, the specific consumption rate of the component depends on its dynamics, i. e. the increase (or decrease) of the consumption rate after the corresponding component has been controlled to change its operating state. For example, a component may change its operating state when it has been switched on (at a time point t = 0) or when an operating parameter of the component has been changed, for example to change an operating speed of a consumer such as a speed of the fan. As exemplarily shown in FIG. 5 accordingto consumption rate 502 of the first electric consumer 310, the maximum consumption of electric energy (70 kW) of the first electric consumer 310 has been reached immediately after the first electric consumer 310 has been switched on at time point t = 0. Compared to the other electric consumers, the first electric consumer 310 has the highest maximum consumption of electric energy at least for a short time of about 1 second. In addition, the first electric consumer 310 has the highest dynamics. But the first electric consumer 310 is not configured to burn so much electric energy for a longer time. Thus, after a short period of time, the consumption rate 502 of the first electric consumer 310 drops down from the maximum consumption of 70 kW to an electric energy consumption of 3 kW only. This rather low consumption rate 502 of 3 kW can be maintained by the first electric consumer 310 for a long-time operation which is the lowest consumption rate of all consumers illustrated in FIG. 5.

[0073] According to a consumption rate 504 of the second electric consumer 312, the electric energy consumption of the second electric consumer 312 raises up very slowly to the maximum electric energy consumption of 10 kW. Thus, for a short period of time, the electric energy consumption of the second electric consumer 312 is the lowest of all consumers shown in FIG. 5 due to very poor dynamics of the second electric consumer 312. But when operated for a longer period of time, the second electric consumer 312 has a permanent maximum electric energy consumption of 10 kW beinghigher than the permanent electric energy consumption of 3 kW of the first electric consumer 310.

[0074] Hence, a comparison of the consumption rates 502, 504 of the first electric consumer 310 and the second electric consumer 312 shows that a short-time maximum energy consumption of the first electric consumers 310 is greater than a short-time maximum energy consumption of the second electric consumer 312 and that a long-time maximum energy consumption of the second electric consumer 312 is greater than a long-time maximum energy consumption of the first electric consumer 310.

[0075] According to a consumption rate 506 of the third electric consumer 316, the consumption of electric energy of the third electric consumer 316 raises quickly over 30 kW and drops down quickly to a permanent maximum electric energy consumption of 6 kW. Hence, on the one hand, a short-time maximum energy consumption of the third electric consumer 316 is higher than the short-time maximum energy consumption of the second electric consumer 312 due to the better dynamics of the third electric consumer 316 but not as high as the short-time maximum energy consumption of the first electric consumer 310. On the other hand, a long-time maximum energy consumption of the third electric consumer 316 is higher than the long-time maximum energy consumption of the first electric consumer 310 but not as high as the long-time maximum energy consumption of the second electric consumer 312.

[0076] According to a consumption rate 508 of the fourth electric consumer 322, the consumption of electric energy may be delayed due to a latency of the fourth electric consumer 322 when activated at time point t = 0. Hence, for a very short time, the energy consumption of the fourth electric consumer 322 is very low. Then, the consumption rate 508 of the fourth electric consumer 322 raises with very high dynamics up to the maximum consumption of electric energy of 30 kW. Instead of dropping down to a lower value, the fourth electric consumer 322 has a constant electric energy consumption of 30 kW for a longer time period.

[0077] As can be seen in the diagram of FIG. 6, the power distribution unit 302 may control each of the first to fourth electric consumers to adjust the (maximum) electric energy consumption and / or to adjust the dynamics. For example, according to consumption rate 602 of the first electric consumer 310, the dynamics may be reducedso that the maximum consumption of electric energy will be reached shortly later compared to the consumption rate 502 of FIG. 5. In addition, the maximum consumption of electric energy may be reduced from 70 kW to 50 kW compared to the consumption rate 502 of FIG. 5. Analogously, the maximum consumption of electric energy of the third electric consumer 316 may be reduced accordingto consumption rate 606 so that the long-time maximum energy consumption of 6 kW is maintained when this level of electric energy consumption has been reached within a short period of time after the third electric consumer 316 has been switched on at the time point t = 0. If the consumption rate of a consumer has not been adjusted by the power distribution unit 302, the consumption rate may remain unchanged as for example the consumption rate 604 of the second electric consumer and the consumption rate 608 of the fourth electric consumer 322.

[0078] It is exemplarily assumed now, that the agricultural machine 100 is in standstill while the fuel cell 306 is already running at its minimum power of 15 kW. Then, an operator of the agricultural machine 100 accelerates the agricultural machine 100 from standstill with maximum power. In response, the power distribution unit 302 controls the fuel cell 306 to raise up its supply rate 702 to its maximum of 100 kW. A few seconds later, a sudden load drop occurs which may be caused by an emergency braking of the operator for example.

[0079] According to this exemplary scenario, the diagram of FIG. 7 illustrates correspondingly a supply rate 702 of the fuel cell 306, a consumption rate 704 of the electric motor 318 while operating in motor mode and a supply rate 706 of the electric motor 318 while operating in generator mode. As can be seen, the dynamics of the fuel cell 306 is rather low compared to the dynamics of the first or fourth electric consumers 310 (see consumption rate 502) or 322 (see consumption rate 508) (see FIG. 5) because of its electrochemical reactions. The dynamics of the electric motor 318 is also lower than the dynamics of the first or fourth electric consumers 310, 322 but higher than the dynamics of the fuel cell 306.

[0080] At a time point t = 0, the agricultural machine 100 is at standstill so that the electric motor 318 does not consume electric energy (0 kW) as indicated by the consumption rate 704. But the fuel cell 306 already produces electric energy of 15 kW accordingto the supply rate 702. Hence, there is a first imbalance between consumedelectric energy by the electric motor 318 and supplied electric energy by the fuel cell 306 within the power management system 300.

[0081] This (and any other) imbalance can be seen in the diagram of FIG. 8 showing net electric energy 800 as difference between the consumed electric energy and the supplied electric energy within the power management system 300. If an imbalance is present, the net electric energy 800 deviates from 0 kW. Depending on whether more electric energy is consumed than supplied or vice versa, the net electric energy 800 gets positive or negative. The net electric energy 800 is illustrated as a consumption rate if more electric energy is consumed than supplied or as a supply rate if more electric energy is supplied than consumed. According to the first imbalance, more electric energy is supplied than consumed. Thus, the first imbalance is indicated in FIG. 8 as supply rate 802 of 15 kW according to the provided minimum power of the fuel cell 306. The power distribution unit 302 detects the first imbalance. But the supply rate 802 of 15 kW does not exceed the maximum charge power 810 of 40 kW of the electric energy storage 304. Hence, the electric energy storage 304 is slightly charged by the supply rate 802 of 15 kW to compensate the imbalance.

[0082] At about a time point t = 1 s, the agricultural machine 100 is demanded to accelerate quickly. In response thereof, the power distribution unit 302 controls the electric motor 318 in motor mode by means of the inverter 314 to provide a corresponding torque. The electric motor 318 speeds up accordingly so that the electric energy consumption of the electric motor 318 raises up with high dynamics to a maximum of 100 kW according to the consumption rate 704 (see FIG. 7). Since the required electric energy of the electric motor 318 is higher than the energy provided by the fuel cell 306, the power distribution unit 302 controls the fuel cell 306 to produce more electric energy. But the dynamics of the fuel cell 306 is not as high as the dynamics of the electric motor 318. As indicated by the supply rate 702, the fuel cell 306 needs more time to provide the electric energy of 100 kW required by the electric motor 318. 1, e., more electric energy is consumed than simultaneously supplied. Hence, there is a second imbalance between consumed electric energy by the electric motor 318 and supplied electric energy by the fuel cell 306 within the power management system 300 as long as the supply rate 702 of the fuel cell 306 has not been raised up to 100 kW required by the electric motor 318. This imbalance, indicatedin FIG. 8 as consumption rate 804, is detected by the power distribution unit 302. In response thereof, the power distribution unit 302 draws electric energy from the electric energy storage 304 to provide electric energy to the power management system 300 as indicated by the consumption rate 804. Due to very high dynamics of the electric energy storage 304, the imbalance can be compensated immediately by electric energy drawn from the electric energy storage 304.

[0083] Between a time period from about 6.5 s to 9.5 s, the electric energy consumed by the electric motor 318 and the electric energy provided by the fuel cell 306 are in equilibrium as can be seen in FIG. 8 based on the net electric energy 800 of 0 kW. Hence, the electric energy storage 304 may neither be charged nor may electric energy drawn from the electric energy storage 304. Since no imbalance is present, no compensation is necessary.

[0084] At about a time point t = 9.5 s, the agricultural machine 100 is demanded to decelerate quickly, e. g. for emergency braking. In response thereof, the power distribution unit 302 controls the electric motor 318 by means of the inverter 314 to change the operating mode from motor mode to generator mode for recuperative braking. Hence, a load drop occurs. While recuperative braking is active, the kinetic energy of the agricultural machine 100 provided by the front and / or rear wheels 102, 104 via the transmission 320 to the electric motor 318 is converted by the electric motor 318 to electric energy as indicated by the supply rate 706 in FIG. 7. Instead of consuming electric energy, the electric motor 318 provides now electric energy to the power management system 300. Due to the high dynamics of the electric motor 318, the consumption rate 704 of 100 kW changes very fast to the supply rate 706 of 15 kW. Since no electric energy is required to drive the electric motor 318, the power distribution unit 302 controls the fuel cell 306 to reduce the generation of electric energy. But the dynamics of the fuel cell 306 is not as high as the dynamics of the electric motor 318. As indicated by the supply rate 702, the fuel cell 306 needs more time to reduce the generation of electric energy from 100 kW to a lower level. I. e., more electric energy is supplied than simultaneously consumed. Hence, there is a third imbalance between consumed electric energy by the electric motor 318 and supplied electric energy by the fuel cell 306 within the power management system 300 deteriorated by the circumstance that the electric motor 318 provides electric energyinstead of consuming it. This imbalance, indicated in the diagram of FIG. 8 as supply rate 806, is detected by the power distribution unit 302. As consequence thereof, the electric energy storage 304 is charged by the supply rate 806.

[0085] But as can be seen in FIG. 8, the supply rate 806 resulting from the sum of the electric energy provided by the fuel cell 306 and the electric motor 318 raises rather quickly over the maximum charge power 810 of 40 kW of the electric energy storage 304 approximately at a time point t = 9.5 s. The supply rate 806 exceeds the maximum charge power 810 for a rather long time period up to approximately a time point t = 14.5 s. Hence, there is an energy excess 812 approximately between time points t = 9.5 s and t = 14.5 s that cannot be compensated by the electric energy storage 304. In addition, approximately at a time point t = 1 .5 s, there is a very short energy shortage 814 caused by the consumption rate 804 exceeding the maximum discharge power 808 of 70 kW of the electric energy storage 304 due to the second imbalance between the electric energy provided by the fuel cell 306 and the electric energy consumed by the electric motor 318 as described above. This energy shortage 814 can also not be compensated by the electric energy storage 304.

[0086] Consequently, the amount of electric energy compensable by the electric energy storage 304 is restricted by the dynamics of the fuel cell 306 and the electric energy currently provided by the fuel cell 306, as also exemplarily illustrated in the diagram of FIG. 9. In accordance with the consumption rate 704 and the supply rate 706 of the electric motor 318 (see FIG. 7) an electric energy demand 902 of the electric motor 318 is shown in FIG. 9. An energy corridor 904 represents a bandwidth of the electric energy compensable by electric energy storage 304 based on the dynamics and amount of electric energy currently provided by the fuel cell 306. The energy corridor 904 is limited by an upper energy limit 906 and a lower energy limit 908. 1, e., as long as the electric energy demand 902 is within the energy corridor 904 so that neither the upper nor the lower energy limit 906, 908 of the energy corridor 904 is violated, any imbalance between the electric energy provided by the fuel cell 306 and the electric energy consumed (or provided) by the electric motor 318 can be compensated by the electric energy storage 304.

[0087] The upper energy limit 906 depends on the supply rate 702 (see FIG. 7) of the fuel cell 306 and the maximum discharge power 808 of the electric energy storage 304.At a time point t = 0 for example, the upper energy limit 906 may correspond to 85 kW based on the electric energy of 15 kW supplied by the fuel cell 306 (see FIG. 7) and the maximum discharge power 808 of 70 kW of the electric energy storage 304. For the case that the fuel cell 306 does not provide electric energy (0 kW), the upper energy limit 906 may be 70 kW corresponding to the maximum discharge power 808 of 70 kW of the electric energy storage 304. The upper energy limit 906 can raise up to a maximum of 170 kW based on the maximum provided electric energy of 100 kW of the fuel cell 306 (see FIG. 7) and the maximum discharge power 808 of 70 kW of the electric energy storage 304. Hence, the upper energy limit 906 may vary between 70 kW and 170 kW. The dependency of the supply rate 702 of the fuel cell 306 and the maximum discharge power 808 of the electric energy storage 304 is also illustrated in FIG. 10. At a time point t = t1 , the supply rate 702 of the fuel cell 306 is 0 kW. Accordingly, the power distribution unit 302 calculates an upper energy limit 906 of 70 kW for this time point t1 based on the sum of the supply rate 702 and the maximum discharge power 808 of 70 kW of the electric energy storage 304. At a different time point t = t2, the supply rate 702 of the fuel cell 306 is 40 kW. Accordingly, the power distribution unit 302 calculates an upper energy limit 906 of 110 kW for this time point t1 based on the sum of the supply rate 702 and the maximum discharge power 808 of 70 kW. At another time point t = t3, the supply rate 702 of the fuel cell 306 is 70 kW. Accordingly, the power distribution unit 302 calculates an upper energy limit 906 of 140 kW for this time point t3 based on the sum of the supply rate 702 and the maximum discharge power 808 of 70 kW.

[0088] The lower energy limit 908 depends on the supply rate 702 (see FIG. 7) of the fuel cell 306 and the maximum charge power 810 of the electric energy storage 304. At a time point t = 0 for example, the lower energy limit 908 may correspond to -25 kW based on the electric energy of 15 kW supplied by the fuel cell 306 (see FIG. 7) and the maximum charge power 810 of 40 kW of the electric energy storage 304. The lower energy limit 908 can raise up to a maximum of 60 kW based on the maximum provided electric energy of 100 kW of the fuel cell 306 (see FIG. 7) and the maximum charge power 810 of 40 kW of the electric energy storage 304. For the case that the fuel cell 306 does not provide electric energy (0 kW), the lower energy limit 908 may fall down to a minimum of -40 kW corresponding to the maximum charge power 810 of 40 kW of the electric energy storage 304. Hence, the lower energy limit 908 may vary between -40 kWand 60 kW. The dependency of the supply rate 702 of the fuel cell 306 and the maximum charge power 810 of the electric energy storage 304 is also illustrated in FIG.11 . At a time point t = t4, the supply rate 702 of the fuel cell 306 is 70 kW. Accordingly, the power distribution unit 302 calculates a lower energy limit 908 of 30 kW for this time point t4 based on the sum of the supply rate 702 and the maximum charge power 810 of 40 kW of the electric energy storage 304. At a different time point t = t5, the supply rate 702 of the fuel cell 306 is 40 kW. Accordingly, the power distribution unit 302 calculates a lower energy limit 908 of 0 kW for this time point t5 based on the sum of the supply rate 702 and the maximum charge power 810 of 40 kW of the electric energy storage 304. At another time point t = t6, the supply rate of the fuel cell 306 is 0 kW. Accordingly, the power distribution unit 302 calculates a lower energy limit 908 of -40 kW for this time point t6 based on the sum of the supply rate 702 and the maximum charge power 810 of 40 kW of the electric energy storage 304.

[0089] The power distribution unit 302 is configured to control the electric components of the power management system 300 (see FIG. 4) to counteract an energy excess 812 or an energy shortage 814 as described above. As long as the upper or lower energy limit 906, 908 has not been violated, the power distribution unit 302 acts proactively to avoid that the electric energy demand 902 leaves the energy corridor 904. For example, it may calculate the gradient of the actual gap of electric energy demand 902 to the upper or lower energy limit 906, 908 and may observe any control inputs of the operator of the agricultural machine 100 such as a depression of an accelerator pedal (feed forward). But if the electric energy demand 902 leaves the energy corridor 904, the power distribution unit 302 has to react to get the electric energy demand 902 back into the energy corridor 904 as fast as possible.

[0090] To avoid that an energy shortage 814 or an energy excess 812 causes any issues for the power management system 300, the power distribution unit 302 can execute a method for controlling the power management system 300 of the electrically powered agricultural machine 100 as depicted in the flow chart of FIG. 12. The method may be at least partly a computer-implemented method stored as a computer program product in the memory 206 of the control unit 114 of the power distribution unit 302 (see FIG. 2). The control unit 114 is configured to carry out the method. Computer- implemented parts of the method may be executed by the controller 204 of the controlunit 114. Non-computer-implemented parts of the method may be executed manually or by other components of the system. The method is described by way of example of several steps without any restriction in respect of these steps. I. e. the number or the order of steps may be adapted, for example single steps may be excluded and / or added and executed earlier or later than described. The method starts with step S100 and proceeds to step S101 .

[0091] At step S101 , the power distribution unit 302 receives the actual energy values of all electric components (see FIG. 4) for calculating the electric energy supplied by the fuel cell 306 and / or the electric motor 318 (when operated in generator mode) and the electric energy consumed by the first to fourth electric consumers 310, 312, 316322 and the electric motor 318 (when operated in motor mode). The value of consumed electric energy corresponds to electric energy demand 902. The energy values are measured by sensors and transmitted to the power distribution unit 302 with high frequency and advantageously unfiltered.

[0092] The method proceeds to step S102 and the power distribution unit 302 determines the net electric energy 800 based on a difference between supplied electric energy and consumed electric energy of the power management system 300.

[0093] The method proceeds to step S103 and the power distribution unit 302 determines the upper energy limit 906 based on the sum of the maximum discharge power 808 of the electric energy storage 304 and the current supply rate 702 of the fuel cell 306 as explained above.

[0094] The method proceeds to step S104 and the power distribution unit 302 determines the lower energy limit 908 based on the sum of the maximum charge power 810 of the electric energy storage 304 and the current supply rate 702 of the fuel cell 306 as explained above. The values of the upper and lower energy limits 906, 908, the electric energy demand 902 and / or the net electric energy 800 can theoretically be lagged up to one cycle time of the control unit 114.

[0095] The method proceeds to step S105 and the power distribution unit 302 checks whether an energy excess 812 is present because the net electric energy 800 exceeds the maximum charge power 810 of the electric energy storage 304. The maximum charge power 810 may be measured or may be stored as a parameter in the memory 206. The power distribution unit 302 compares the determined electric energy demand902 with the determined lower energy limit 908. If the electric energy demand 902 violates the lower energy limit 908, an energy excess 812 is detected by the power distribution unit 302 as for example shown in FIG. 9 approximately from time point t = 9.5 s to t = 14.5 s. Then, the method proceeds with step S108. Otherwise, the method proceeds to step S106.

[0096] At step S106, the power distribution unit 302 checks whether an energy shortage 814 is present because the net electric energy 800 exceeds the maximum discharge power 808 of the electric energy storage 304. The maximum discharge power 808 may be measured or stored as parameter in the memory 206. The power distribution unit 302 compares the determined electric energy demand 902 with the determined upper energy limit 906 to anticipate a violation of the upper energy limit 906. If a violation has been anticipated, an energy shortage 814 is detected by the power distribution unit 302 as for example shown in FIG. 9 approximately at time point t = 1 .5 s. Then, the method proceeds with step S107. Otherwise, the method proceeds to step S112.

[0097] At step S107, the power distribution unit 302 takes action to increase net electric energy 800 so that a violation of the upper energy limit 906 by the electric energy demand 902 is avoided. For example, the power distribution unit 302 controls the inverter 314 to use not more electric energy than available in the power management system 300 to counteract the energy shortage 814, for example by setting a torque limit in speed mode and vice versa. Accordingto this, the inverter 314 can use only the electric energy that remains from the subtraction of the amount of the electric energy supplied by the electric energy storage 304 and the fuel cell 306 and the amount of electric energy consumed by the first to fourth consumers 310, 312, 316 and 322. So, the consumption of electric energy of the electric motor 318 may be decreased.Moreover, the power distribution unit 302 may also reduce the amount of consumed electric energy of any one of the first to fourth consumers 310, 312, 316 and 322 if possible. As a result, the electric energy demand 902 may maximally raise up to a maximum demand 910 very close to the upper energy limit 906 as exemplarily illustrated in FIG. 13. So, the power distribution unit 302 prevents an energy shortage 814 as shown in FIG. 9. If the fuel cell 306 operates below is maximum supply rate 702 of 100 kW, the power distribution unit 302 can control the fuel cell 306 to increasesupply of electric energy to increase net electric energy 800. Then, the method proceeds to step S112.

[0098] At step S108, the power distribution unit 302 takes action to decrease net electric energy 800 so that the violation of the lower energy limit 908 by the electric energy demand 902 is avoided. A first action is to control the fuel cell 306 to reduce the provided power (supply rate 702). But the dynamics of the fuel cell 306 is not sufficient to reduce the energy excess 812 in due time. Hence, the power distribution unit 302 takes additional actions to decrease the net electric energy 800. For example, the power distribution unit 302 may control any one of the first to fourth electric consumers 310, 312, 316 and 322 to consume more electric energy to compensate the energy excess 812. The first to fourth electric consumers 310, 312, 316 and 322 are controlled to consume the energy excess 812 until the supplied power of the fuel cell 306 has been reduced enough so that the net electric energy 800 does not violate the maximum charge power 810 of the electric energy storage 304 any more to stay between the maximum charge power 810 and the maximum discharge power 808. The controlling of the first to fourth electric consumers 310, 312, 316 and 322 is individually prioritized by the power management systems 300 for dynamical and efficiency aspects. For example, the prioritization depends on the duration of the energy excess 812.

[0099] So, the method proceeds to step S109 and the power distribution unit 302 checks whether a short-time energy excess is present because net electric energy 800 is greater than the maximum charge power 810 of the electric energy storage 304 for a predefined time period or whether a long-time energy excess is present because net electric energy 800 is greater than the maximum charge power 810 of the electric energy storage 304 longerthan the predefined time period. The predefined time period is stored as a parameter in the memory 206 of the control unit 114 and may be less or equal one second. The predefined time period may also be adjustable by the operator or may be adaptively controlled by the power distribution unit 302. The predefined time period may depend on a control reserve of first electric consumer 310. The first electric consumer 310 will recover after the control reserve has been exhausted to provide a maximum energy consumption of 70 kW again. Alternatively, the predefined time period may depend on a ramp down rate of the electric motor 318 and / or of the fuel cell 306. The power distribution unit 302 may determine or anticipate a short-time or long-timeenergy excess based on operator inputs such as a depression of a brake pedal or a calculated time period to reduce the supply rate 702 of the fuel cell 306 to a predefined energy value (e. g. 0 kW).

[0100] In case of a short-time energy excess, the method proceeds to step S110 and the power distribution unit 302 may control any one of the electric consumers having high dynamics such as the first electric consumer 310 to consume more electric energy to compensate the energy excess. Electric consumers having poor dynamics may be ignored since they would not be applicable to compensate the energy excess in due time. Then, the method proceeds to step S112.

[0101] In case of a long-time energy excess, the method proceeds to step S111 and the power distribution unit 302 may control both electric consumers having high dynamics and electric consumers having poor dynamics. The electric consumers having high dynamics may reduce and compensate the energy excess very quickly. But the electric consumers having high dynamics may not be configured for a long-term compensation of the energy excess such as the first electric consumer 310. Instead, the electric consumers having poor dynamics may be better for a long-term compensation as can be seen in FIG. 5. Hence, the power distribution unit 302 may additionally control the electric consumers having good long-time consumption rates such as the second electric consumer 312 to consume more electric energy in case of a long-time energy excess. The power distribution unit 302 may control the electric consumer(s) having a good long-time consumption rate to start increasing the consumption of electric energy before the predefined time period has been elapsed. Depending on the dynamics of the electric consumers having a good long-time consumption rate, the electric consumers having good long-time consumption rates may be controlled by the power distribution unit 302 to increase their consumption rates each to a maximum value before the predefined time period elapses. When the consumption rates of the electric consumers having good long-time consumption rates have been raised enough so that the long-time energy excess can solely be compensated by them, the power distribution unit 302 may control the electric consumers having high dynamics to reduce their energy consumption rates again.

[0102] As can be seen in FIG. 8 and FIG. 9, the duration of the energy excess 812 (detected at step S105) starting approximately at time point t = 9.5 s is longer than thepredefined time period of one second. Hence, the power distribution unit 302 detects a long-time energy excess at step S109. Consequently, the power distribution unit 302 controls both the electric consumers having high dynamics such as the first and fourth electric consumer 310 and 322 and the electric consumers having medium or poor dynamics such as the second and third electric consumer 312 and 316 to increase their consumption rates in response to the detected energy excess 812.

[0103] FIG. 14 illustrates the consumption rate 1402 of the first electric consumer 310, the consumption rate 1404 of the second electric consumer 312, the consumption rate 1406 of the third electric consumer 316, the consumption rate 1408 of the fourth electric consumer 322 and a cumulated consumption rate 1410 of all four electric consumers 310, 312, 316 and 322. The first electric consumer 310 reacts immediately after the detected energy excess 812. Its consumption rate 1402 increases very fast due to the high dynamics of the first electric consumer 310. The power distribution unit 302 controls the first electric consumer 310 to increase its consumption rate 1402 up to a maximum energy value. Correspondingly, the cumulated consumption rate 1410 increases. But the maximum value of the consumption rate 1402 can be maintained for a short period of time (about one second) only as illustrated by the consumption rate 502 in FIG. 5. Then, the power distribution unit 302 needs to reduce the consumption rate 1402 of the first electric consumer 310 to avoid a failure of the first electric consumer 310. Correspondingly, the cumulated consumption rate 1410 drops afterthe short period of time to a consumption rate of approximately 63 kW.

[0104] The power distribution unit 302 controls the second electric consumer 312 to consume more electric energy. The second electric consumer 312 reacts immediately after the detected energy excess 812. But due to the poor dynamics of the second electric consumer 312 as also shown by consumption rate 504 in FIG. 5, the consumption rate 1404 increases very slowly. Nevertheless, the second electric consumer 312 contributes to increase the cumulated consumption rate 1410 up to a time point of approximately t = 12 s.

[0105] The power distribution unit 302 also engages the third electric consumer 316. The consumption rate 1406 of the third electric consumer 316 varies overtime as already illustrated by the consumption rate 506 in FIG. 5. As shown in FIG. 14, the third electric consumer 316 also reacts immediately after the detected energy excess 812.Hence, the consumption rate 1406 of the third electric consumer 316 contributes to increase the cumulated consumption rate 1410 above the consumption rate 1402 of the first electric consumer 310 up to more than 100 kW within the short period of time. Then, the consumption rate 1406 falls analogously to the consumption rate 506 shown in FIG. 5. For the case that the third electric consumer 316 had been activated before the detection of the energy excess 812, e. g. for heating of the cabin 108, the compensational effect due to the peak at the beginning of the consumption rate 1406 may not be achievable any more. Due to the medium dynamics, the third electric consumer 316 has to be activated even when the first electric consumer 310 is active to provide a compensation of the energy excess 812 without a lack when the consumption rate 1402 of the first electric consumer 310 has to be reduced as described above.

[0106] After a short delay for activating the fourth electric consumer 322 as illustrated by the consumption rate 508 in FIG. 5, the power distribution unit 302 can control the fourth electric consumer 322 to consume electric energy in accordance with consumption rate 1408. Due to the latency of the fourth electric consumer 322 after activation, the consumption rate 1408 can contribute to increase the cumulated consumption rate 1410 after a short delay. But after the delay, the consumption rate 1408 increases with high dynamics up to its maximum value. Then, the maximum value of the consumption rate 1408 can be provided constantly for a long period of time as can be seen in FIG. 14, too. Hence, the cumulated consumption rate 1410 can be maintained at a minimum energy value of at least the energy value of the consumption rate 1408 of the fourth electric consumer 322.

[0107] Moreover, the power distribution unit 302 controls the fuel cell 306 to reduce its supply rate 702 (see FIG. 7) after the detection of the energy excess 812. As consequence, the lower energy limit 908 (as well as the upper energy limit 906) falls after the detection of the energy excess 812 approximately at time point t = 9.5 s as shown in FIG. 13. Hence, the difference between the electric energy demand 902 and the lower energy limit 908 during the period of the energy excess 812 as shown in FIG. 9 can be reduced.

[0108] As a result of the actions to decrease the net electric energy 800, the electric energy demand 902 can be controlled by the power distribution unit 302 to be kept nearly completely within the energy corridor 904 between the upper energy limit 906and the lower energy limit 908 (see FIG. 13 in comparison with FIG. 9). Only a minor energy excess 812 may arise. Hence, neither the maximum discharge power 808 nor the maximum charge power 810 may be exceeded by the net electric energy 800.

[0109] The power distribution unit 302 may stop the actions to decrease the net electric energy 800 as described above when the net electric energy 800 (supply rate 806) has been reduced below the maximum charge power 810 of the electric energy storage 304, here at a time point 816 (approximately t = 14.5 s), so that the net electric energy 800 (supply rate 806) can be compensated by the electric energy storage 304 alone (see FIG. 8).

[0110] As the supply rate 702 of the fuel cell 306 falls, the first to fourth electric consumers 310, 312, 316 and 322 can be switched off successively by the power distribution unit 302, so that electric energy is wasted as less as possible while trying to control the electric energy demand 902 close to the lower energy limit 908 (see FIG. 13). The power distribution unit 302 switches off the second electric consumer 312 approximately at time point t = 12.2 s, the third electric consumer 316 approximately at time point t = 12.5 s. Then, only the fourth electric consumer 322 is still active. Instantly after switching off the third electric consumer 316, the fuel cell 306 is still delivering 55 kW while the motor is still recuperating with 15 kW (see FIG. 7). In sum, 70 kW are produced at this time. The fourth electric consumer 322 consumes 30 kW. Thus, the remaining 40 kW can be compensated completely by the electric energy storage 304 with its maximum charge power 810 of 40 kW. The power distribution unit 302 switches off the fourth electric consumer 322 as soon as the supply rate 702 of the fuel cell 306 has been reduced to 25 kW approximate at time point t = 14.7 s. Then, the sum of supplied electric energy (25 kW from the fuel cell 306 and 15 kW from the electric motor 318) within the power management systems 300 would not any longer exceed the maximum charge power 810 of the electric energy storage 304. When none of the first to fourth electric consumers 310, 312, 316 and 322 is required any more to compensate the energy excess 812, the method proceeds to step S112.

[0111] When any one of the first to fourth electric consumers 310, 312, 316 and 322 has been activated by the power distribution unit 302 to compensate the energy excess 812, the power distribution unit 302 may additionally adjust the (maximum) electric energy consumption and / or the dynamics of the corresponding electric energyconsumer as shown in FIG. 6. For example, the power distribution unit 302 may adjust the electric energy consumption and / orthe dynamics as illustrated by consumption rate 1602 of the first electric consumer 310, consumption rate 1604 of the second electric consumer 312, consumption rate 1606 of the third electric consumer 316 and consumption rate 1608 of the fourth electric consumer 322 in FIG. 16. Accordingly, an adjusted cumulated consumption rate 1610 of all four electric consumers 310, 312, 316 and 322 can be achieved.

[0112] The power distribution unit 302 may control the third electric consumer 316 similar to the first electric consumers 310 to provide a consumption rate with a high peak. Hence, the operating time of the first electric consumer 310 can be reduced since the cumulated consumption rate of the second to fourth electric consumers 312, 316 and 322 reaches very quickly an energy value sufficient to compensate the energy excess 812. A permanent consumption rate can also be provided by the second electric consumer 312. As the dynamics of the second electric consumer 312 is comparatively slow, the second electric consumer 312 can be activated after the first electric consumer 310, the third electric consumer 316 and the fourth electric consumer 322 have been activated.

[0113] As a result of controlling the (maximum) electric energy consumption and / or the dynamics of the first to fourth electric consumers 310, 312, 316 and 322, the electric energy demand 902 can be controlled much closer to the lower energy limit 908 (see FIG. 15 in comparison with FIG. 13). Only a minor energy excess 812 may arise. Hence, neither the maximum discharge power 808 nor the maximum charge power 810 may be exceeded by the net electric energy 800.

[0114] Again, when none of the first to fourth electric consumers 310, 312, 316 and 322 is required any more to compensate the energy excess 812, the method proceeds to step S112.

[0115] At step S112, the method ends. The power distribution unit 302 may restart the method with step S100 again.

[0116] All references cited herein are incorporated herein in their entireties. If there is a conflict between definitions herein and in an incorporated reference, the definition herein shall control.LISTING OF DRAWING ELEMENTS agricultural machine 320 transmission front wheel 322 fourth electric consumer rear wheel 324 pressure reduction valve hood 326 DC / DC converter cabin 328 on-board power supplytank 330 DC / DC converter enclosure 332 on-board power supply control unit 334 on-board charging device I / O interface 336 charging receptacle controller 338 refilling receptacle memory 340 AC compressor power management system 342 air compressor power distribution unit 502 consumption rate electric energy storage 504 consumption rate fuel cell 506 consumption rate DC / DC converter 508 consumption rate first electric consumer 602 consumption rate second electric consumer 604 consumption rate inverter 606 consumption rate third electric consumer 608 consumption rate electric motor 702 supply rate04 consumption rate 1604 consumption rate 06 supply rate 1606 consumption rate 00 net electric energy 1608 consumption rate 02 supply rate 1610 cumulated consumption rate 04 consumption rate 06 supply rate 08 maximum discharge power 10 maximum charge power 12 energy excess 14 energy shortage816 time point902 electric energy demand904 energy corridor906 upper energy limit908 lower energy limit910 maximum demand1402 consumption rate1404 consumption rate1406 consumption rate1408 consumption rate1410 cumulated consumption rate1502 electric energy demand1602 consumption rate

Claims

CLAIMSWhat is claimed is:1 . An electrically powered agricultural machine (100) comprising a power management system (300), comprising: a power distribution unit (302) electrically connected with an electric motor (318) and a first electric consumer (310); wherein the electric motor (318) is configured to be operated in a motor mode to convert electric energy into a torque; and in a generator mode to convert a torque into electric energy; the electrically powered agricultural machine (100) further comprising an electric energy storage (304) electrically connected with the power distribution unit (302) and configured to supply electric energy to the electric motor (318); and be charged by electric energy received from the electric motor (318); wherein a maximum charge power of the electric energy storage (304) is smaller than a maximum energy supply of the power management system (300); and a maximum discharge power of the electric energy storage (304) is smaller than a maximum energy consumption of the power management system (300); and wherein the power distribution unit (302) is configured to determine an energy excess (812) if net electric energy (800) exceeds the maximum charge power (810) of the electric energy storage (304); wherein the net electric energy (800) is a difference between supplied electric energy and consumed electric energy of the power management system (300).

2. The electrically powered agricultural machine (100) of claim 1 , wherein the power distribution unit (302) is configured to determine an energy shortage if net electric energy (800) exceeds the maximum discharge power (808) of the electric energy storage (304).

3. The electrically powered agricultural machine (100) of claim 2, whereinthe power distribution unit (302) is configured to increase the net electric energy (800) in case of an energy shortage (814).

4. The electrically powered agricultural machine (100) of claim 3, wherein the power distribution unit (302) is configured to decrease consumption of electric energy of the electric motor (318) or the first electric consumer (310) to increase net electric energy (800).

5. The power management system (300) of claim 3 or 4, comprising an electric energy source; wherein the power distribution unit (302) is configured to increase supply of electric energy by the electric energy source to increase net electric energy (800).

6. The electrically powered agricultural machine (100) of any one of the preceding claims, wherein the power distribution unit (302) is configured to decrease net electric energy (800) in case of an energy excess.

7. The electrically powered agricultural machine (100) of claim 6, wherein the power distribution unit (302) is configured to increase consumption of electric energy of the first electric consumer (310) to decrease net electric energy (800).

8. The electrically powered agricultural machine (100) of claim 6 or 7, comprising an electric energy source; wherein the power distribution unit (302) is configured to decrease supply of electric energy by the electric energy source to decrease the net electric energy (800).

9. The electrically powered agricultural machine (100) of any one of claims 6 to8, comprising: another electric consumer (312, 316, 322); whereina short-time maximum energy consumption of the first electric consumer (310) is greater than a short-time maximum energy consumption of the other electric consumer (312, 316, 322); and a long-time maximum energy consumption of the other electric consumer (312, 316, 322) is greater than a long-time maximum energy consumption of the first electric consumer (310).

10. The electrically powered agricultural machine (100) of claim 9, wherein the power distribution unit (302) is configured to determine a short-time energy excess if net electric energy is greater than the maximum charge power of the electric energy storage (304) for a predefined time period; and a long-time energy excess if net electric energy is greater than the maximum charge power of the electric energy storage (304) for a time period longer than the predefined time period.11 . The electrically powered agricultural machine (100) of claim 10, wherein the power distribution unit (302) is configured to increase consumption of electric energy of the first electric consumer (310) in case of a short-time energy excess; and increase consumption of electric energy of the other electric consumer (312, 316, 322) in case of a long-time energy excess.

12. The electrically powered agricultural machine (100) of claim 11 , wherein the power distribution unit (302) is configured to increase consumption of electric energy of the other electric consumer (312, 316, 322) in case of a long-time energy excess before the predefined time period elapses.

13. The electrically powered agricultural machine (100) of claim 12, wherein the power distribution unit (302) is configured to increase consumption of electric energy of the other electric consumer (312, 316, 322) to a maximum value before the predefined time period elapses.

14. The electrically powered agricultural machine (100) of any one of claims 10 to 13, wherein the predefined time period is a time period of equal or less than 1 second.

15. The electrically powered agricultural machine (100) of any one of claims 10 to 14, wherein the predefined time period depends on a ramp down rate of the electric motor (318) and / or of the electric energy source.

16. The electrically powered agricultural machine (100) of any one of claims 9 to 14, wherein the other electric consumer (312, 316, 322) is a fan, a PTC resistance or a retarder.

17. The electrically powered agricultural machine (100) of any one of the preceding claims, wherein the first electric consumer (310) is a brake resistor.

18. The electrically powered agricultural machine (100) of any one of the preceding claims, wherein a sum of the maximum charge power of the electric energy storage (304) and the maximum energy consumption of the first electric consumer (310) is smaller than a maximum energy supply of each electric energy source of the power management system (300).

19. A method of controlling a power management system (300) of an electrically powered agricultural machine (100) comprising an electric energy storage (304), a power distribution unit (302), a first electric motor (310) and a first electric consumer (310), the method comprising: determining an energy excess (812) if net electric energy (800) exceeds the maximum charge power of the electric energy storage (304); wherein the net electric energy (800) is a difference between supplied electric energy and consumed electric energy of the power management system (300).

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