Method of operating electric machine coupled to mechanical load

Abstract

The present disclosure relates to a method 300 of operating an electric machine 230 having a rotating assembly 234 coupled to a mechanical load 240. The method 300 comprises: determining 310 a fluctuating speed demand corresponding to a time-varying component of the speed of the rotating component 234; determining 330 a rotating assembly speed reference value based on the fluctuating speed demand; and controlling 340 the motor 230 according to the rotating assembly speed reference value. The fluctuating speed demand is determined to reduce variations in the total power drawn or provided by the electric machine 230 in use.

Description

Technical Field

[0001] The present disclosure relates to a method of operating an electric motor coupled to a mechanical load. The present disclosure also relates to an electric drive device comprising an electric motor coupled to a mechanical load and a controller adapted to perform such a method and a transport refrigeration system comprising such an electric drive device. Background Art

[0002] It is known to provide an electric drive device comprising a DC bus, an inverter and an electric motor having a rotor coupled to a mechanical load. The electric drive device may generally be configured to drive the mechanical load. The mechanical load may be, for example, a compressor or a fan associated with a refrigeration circuit of a transport refrigeration system. The DC bus may be configured to receive power from an external power source.

[0003] In use, the power drawn from the DC bus by the motor may vary (eg due to variations in the mechanical load driven by the motor). As a result, the voltage of the DC bus may be subject to undesirable fluctuations.

[0004] It is therefore desirable to provide a method of controlling a motor and / or to provide an electric drive device that can effectively and efficiently prevent a DC bus voltage from fluctuating greatly. Summary of the invention

[0005] According to a first aspect, there is provided a method of operating an electric machine having a rotating assembly coupled to a mechanical load, the method comprising:

[0006] determining a fluctuating speed demand corresponding to a time varying component of a speed of a rotating component;

[0007] determining a rotating component speed reference value based on the fluctuating speed demand; and

[0008] The electric machine is controlled according to a rotating component speed reference, wherein a fluctuating speed demand is determined to reduce variations in total power drawn or provided by the electric machine in use.

[0009] The fluctuating speed demand may be determined to reduce variations in the total power drawn by the electric machine in use.

[0010] The fluctuating speed demand may correspond to a cyclically varying component of the speed of the rotating component.The speed of the rotating component may be monitored using a rotating component sensing device.

[0011] Controlling the electric machine according to the rotating component speed reference may include controlling the electric machine to maintain the speed of the rotating component at the rotating component speed reference.

[0012] The rotating component speed reference may vary with respect to time based on fluctuating speed demands.

[0013] The method may include:

[0014] calculating a torque associated with driving of the mechanical load based on a predetermined inertia value, a speed of the rotating component, and a total torque applied to the rotating component; and

[0015] The fluctuating speed demand is determined based on a predetermined inertia value and a torque associated with the driving of the mechanical load.

[0016] The predetermined inertia value may correspond to a combination of the inertia of the rotating component and the inertia of the mechanical load.

[0017] The method may include calculating a torque associated with driving of the mechanical load based on a predetermined inertia value, a rate of change of a speed of the rotating component, and a total torque applied to the rotating component.

[0018] The method may include:

[0019] calculating the inertia torque by multiplying a predetermined inertia value by a rate of change of speed of the rotating component; and

[0020] The torque associated with the drive of the mechanical load is calculated by subtracting the inertia torque from the total torque applied to the rotating component.

[0021] Calculating the torque associated with the driving of the mechanical load (240) may include setting the torque associated with the driving of the mechanical load equal to subtracting the inertia torque from the total torque applied to the rotating component.

[0022] The method may include determining the fluctuating speed demand by dividing a time integral of a fluctuating component of torque associated with driving of the mechanical load by a predetermined inertia value.

[0023] The method may include:

[0024] determining or receiving an average speed demand corresponding to a constant component of the speed of the rotating component; and

[0025] A rotating component speed reference is determined based on the average speed demand and the fluctuating speed demand.

[0026] According to a second aspect, there is provided an electric drive device, comprising:

[0027] a controller adapted to perform the method according to the first aspect; and

[0028] An electric machine has a rotating component coupled to a mechanical load.

[0029] The electric drive device may further comprise a power converter, wherein the electric machine is configured to draw AC power or DC power from the power converter in use.

[0030] The electric drive device may further include a DC bus.The power converter may be configured to receive an input DC input voltage from a power source via the DC bus.

[0031] According to a third aspect, there is provided a transport refrigeration system comprising an electric drive device according to the second aspect and a vapour compression refrigeration circuit comprising a compressor. The mechanical load may comprise a compressor.

[0032] According to a fourth aspect, there is provided a computer program comprising instructions which, when executed by a controller of an electric drive device according to the second aspect, cause the controller to perform a method according to the first aspect.

[0033] According to a fifth aspect, there is provided a machine readable medium storing a computer program according to the fourth aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A vehicle including a transport refrigeration system is shown;

[0035] Figure 2 Is suitable for Figure 1 A schematic diagram of an example transport refrigeration unit for use with a vehicle of the type shown in FIG. 1 , the example transport refrigeration unit including a vapor compression refrigeration circuit having a compressor;

[0036] Figure 3 Is suitable for Figure 2 A schematic diagram of an example electric drive apparatus for use with a transport refrigeration unit;

[0037] Figure 4 It shows the operation Figure 3 A flowchart of an example method of electrically driving an electric motor of an electric device;

[0038] Figure 5 It is shown in detail Figure 4 a block diagram of a portion of an example method of;

[0039] Figure 6 is a highly schematic diagram of a machine-readable medium having a computer program stored thereon which, when executed by a controller, causes the controller to perform Figure 4 Example method of . DETAILED DESCRIPTION

[0040] Figure 1 A vehicle 10 is shown including a transport refrigeration system 20. Figure 1In an example of a transport refrigeration system 20, a transport refrigeration system 20 forms part of a long-haul refrigerated semi-trailer having a structure 22 that supports (or forms) at least one climate-controlled compartment 24, which is configured to be cooled and / or heated by a TRU 110. The climate-controlled compartment 24 may take the form of a plurality of compartments or have a plurality of zones. The structure 22 includes a chassis. The vehicle 10 includes an electrical device 100, which includes various components disposed within a chassis underbody 105. In some examples, one or more components of the electrical device 100 may be integrated into or incorporated into the TRU 110. The structure 22 supports the TRU 110 and the chassis underbody 105. The vehicle 10 also includes a tractor unit 14 that is removably coupled to the trailer.

[0041] Figure 2 Schematically showing suitable Figure 1 1 and 12. A diagram of an example TRU 110 for use within a vehicle 10 and a transport refrigeration system 20 of the transport refrigeration system 20. The TRU 110 includes a vapor compression refrigeration circuit 400. The vapor compression refrigeration circuit 400 includes an evaporator 408 configured to receive heat from a climate control compartment 24 of the transport refrigeration system 20, and a condenser 404 configured to discharge heat to a heat sink 44 (e.g., ambient air outside the climate control compartment 24). For these purposes, the vapor compression refrigeration circuit 400 also includes a compressor 402 and an expansion valve 406. Thus, the vapor compression refrigeration circuit 400 can be controlled so that heat is removed from the climate control compartment 24. The TRU 110 also includes a plurality of fans 462, 464. Figure 2 In the example, a first fan 462 is associated with (e.g., located near) the condenser 404 for improving heat transfer at one or more surfaces of the condenser 404, and a second fan 464 is associated with (e.g., located near) the evaporator 408 for improving heat transfer at one or more surfaces of the evaporator 408.

[0042] The compressor 402 is mechanically coupled to the electric drive device 200, and thus the compressor 402 is configured to be driven by the electric drive device 200. The electric drive device 200 can be operated to drive the compressor 402, thereby controlling the vapor compression refrigeration circuit 400. It will be apparent to those skilled in the art that the compressor 402 can be any suitable type of compressor. However, in a specific example, the compressor 402 can be a reciprocating compressor (e.g., a piston compressor) or a scroll compressor.

[0043] Figure 3 is a schematic diagram of an example electric drive device 200, which is particularly, but not exclusively, suitable for use with Figure 2 The vapor compression refrigeration circuit 400 and Figure 1The example electric drive device 200 includes a DC bus 210, an inverter system 220, a motor 230 (eg, an AC motor 230), a plurality of current sensors 282A-282C, a rotor sensing device 283, and a controller 290.

[0044] The motor 230 includes a rotor 234, a stator 232, and a plurality of phase windings 221-223. Figure 3 In the example of , the plurality of phase windings include a first phase winding 221, a second phase winding 222 and a third phase winding 223. Therefore, Figure 3 The motor 230 shown can be described as a three-phase AC motor 230. Figure 3 In the example of , each of the plurality of phase windings 221-223 is associated with the stator 232 (e.g., disposed on or within the stator 232). However, it will be understood that in other examples according to the present disclosure, the plurality of phase windings may include any suitable number of phase windings, and / or each of the plurality of phase windings may be associated with the rotor 234 (e.g., disposed on or within the rotor 234). In addition, in Figure 3 In the example of FIG. 2 , the phase windings 221 - 223 are shown as being connected in a delta configuration. However, it will be understood that the phase windings 221 - 223 may be connected in other ways (e.g., in a star configuration). Each phase winding 221 - 223 may include one or more coils. The rotor 234 may be referred to as a rotating assembly 234.

[0045] The rotor 234 is mechanically coupled to a load 240 (e.g., a mechanical load 240), and thus the rotor 234 is configured to drive the load 240. The load 240 is driven directly or indirectly by the rotation of the rotor 234. As an example, the load 240 may be directly mechanically coupled to the load 240 via a drive shaft. As another example, the load 240 may be indirectly coupled to the load 240 via a transmission including a gearbox. Figure 3 In the example electric drive device 200, the load 240 is (eg, includes) a compressor 402 (eg, Figure 2 compressor 402 of the vapor compression refrigeration circuit 400).

[0046] The inverter system 220 is generally configured to receive an input DC voltage from the DC bus 210 and provide a plurality of output AC voltages to a plurality of phase windings 221-223. The input DC voltage corresponds to the operating voltage of the DC bus 210. Therefore, the motor 230 draws AC power from the inverter system 220 in use. As known to those skilled in the art, the inverter system 220 may include a plurality of switching devices, at least one inductive element, and / or at least one capacitive element arranged in a suitable inverter system topology. The inverter system 220 may also be referred to as a power converter 220. In other examples according to the present disclosure, the motor 230 may be configured to draw DC power from a DC-DC converter (e.g., a buck converter, a boost converter, a buck-boost converter, etc.) connected to the DC bus 210.

[0047] The DC bus 210 is configured to receive a DC power supply voltage from a DC power source 205. The DC power source 205 may be or be derived from an internal power source (e.g., a fuel cell stack, a battery, or a rectifier coupled to a generator). If so, the DC power source 205 may be located at Figure 1 The DC power source 205 is located within the electrical device 100 of the vehicle 10 shown (e.g., within the chassis lower box 105). Otherwise, the DC power source 205 can be or originate from an external power source (e.g., shore power source) that can be connected to the electrical device 100 via an external connection port and appropriate cables. In particular, the DC power source 205 can be a rectifier configured to receive an AC voltage received from a shore power source. Such a rectifier can be referred to as a grid converter.

[0048] The controller 290 is generally configured to control the operation of the electric drive device 200. More specifically, the controller 290 is configured according to the following reference Figure 4 and Figure 5 An example method is described for operating the motor 230 .

[0049] Although the example electric drive device 200 is described as including the AC motor 230 and / or the inverter system 220, this is not necessarily the case. As an example, the motor 230 can be a DC motor including one or more windings, and the motor 230 can be configured to receive an input DC voltage directly from the DC bus 210 to supply the windings of the motor 230. As another example, the motor 230 can be a DC motor including one or more windings, and the electric drive device 200 can also include a DC-DC converter. The DC-DC converter can be configured to receive an input DC voltage from the DC bus 210 and provide one or more output DC voltages to the windings of the motor 230.

[0050] Figure 42 is a flow chart illustrating a method 300 of operating an electric machine 230 having a rotor 234 coupled to a mechanical load 240. The electric machine 230 may be the one described above with reference to Figure 3 The method 300 includes determining a fluctuating speed demand ω at block 310 . d,f (t) and determining or receiving the average speed demand ω at block 320 d,a Action. Fluctuation speed requirement ω d,f (t) corresponds to the time (eg, cyclic) variation component of the speed of the rotor 234, while the average speed demand ω d,a corresponds to the time constant component of the speed of the rotor 234. Therefore, the fluctuating speed demand ω d,f (t) varies with time, while the average speed requirement ω d,a Does not change with respect to time.

[0051] Refer to the following Figure 5 Describing in more detail the determination of the fluctuating speed demand ω at block 310 d,f (t) action.

[0052] At block 320, an average speed demand ω may be determined or received. d,a as the steady speed set point for the rotor 234. If the mechanical load 240 is or includes Figure 3 The compressor 402 shown may determine or receive an average speed demand ω d,a As a steady speed set point for rotor 234 for use with a vapor compression circuit 400 (e.g., Figure 2 The speed of the controlled operation of the vapor compression circuit 400) drives the compressor 402. In the example, the controller 290 can determine the average speed demand ω based on the signal received from the dedicated controller of the TRU 110 d,a In another example, the controller 290 may receive the average speed demand ω based on a signal received from a dedicated controller of the TRU 110. d,a .

[0053] The method 300 also includes, at block 330, based on the fluctuating speed demand ω determined or received at blocks 310 and 320, respectively. d,f (t) and the average speed demand ω d,a To determine (eg, calculate) a rotor speed reference value ω d,r (t) action. Rotor speed reference value ω d,r (t) can also be called the rotating component speed reference value ω d,r (t). In particular, the rotor speed reference value ω d.r (t) can be determined as the fluctuating speed demand ω d,f (t) and the average speed demand ωd,a The sum of the rotor speed reference value ω is shown in equation (1). d.r (t) According to the fluctuation speed demand ω d,f (t) changes with respect to time.

[0054] ω d,r (t) = ω d,f (t)+ω d,a (1)

[0055] The method 300 further includes, at block 340, determining a rotor speed reference value ω according to the determined rotor speed reference value ω. d,r (t) Control the action of the motor 230. At block 340, according to the rotor speed reference value ω d,r (t) Controlling the motor 230 may generally include controlling the motor 230 to maintain the speed of the rotor 234 at a rotor speed reference value ω d,r (t). Controlling the motor 230 to maintain the speed of the rotor 234 at the rotor speed reference value may be accomplished, for example, by proportional integral (PI) logic, proportional integral derivative (PID) logic, or feedforward logic. If so, the rotor speed reference value ω d,r (t) may be used as a demand signal for such logic, as will be appreciated by those skilled in the art.

[0056] Figure 5 It is shown in detail Figure 4 The determination of the fluctuating speed demand ω represented by block 310 in d,f (t) is a block diagram of the action. Figure 5 The processing shown is represented in the time domain, but those skilled in the art will understand that Figure 5 The various processing shown may generally be performed in the Laplace domain (ie, s-domain).

[0057] for Figure 5 For the purpose of illustrating the process in detail, it is assumed that the total torque T applied to the rotor 234 m (t) is essentially only the torque T associated with the drive of the mechanical load 240 (eg, provided for the drive of the mechanical load 240) l (t) and inertia torque T J (t) is a function of (e.g., composed of).

[0058] The total torque T applied to the rotor 234 m (t) is related to the torque applied to the rotor 234 by the magnetic field induced by the current supplied to the windings 221-223 of the motor 230. Therefore, the total torque T can be controlled by, for example, controlling the current supplied to the windings 221-223 of the motor 230. mFor the same reason, the total torque T may be determined based on the current supplied to the windings 221 - 223 of the motor 230 and an appropriate motor torque coefficient (eg, motor torque constant). m (t). A suitable current transducer may be used (e.g., see above for reference Figure 3 The current sensors 282A-282C) described above are used to monitor the current supplied to the windings 221-223 of the motor 230.

[0059] Inertia torque T J (t) is related to the angular acceleration of the rotor 234. If the inertial torque has a positive sign, the rotor 234 is accelerating and, therefore, energy is being stored in the form of rotational kinetic energy of both the rotor 234 and the mechanical load 240. Otherwise, if the inertial torque has a negative sign, the rotor 234 is decelerating and energy is being converted from the form of rotational kinetic energy of both the rotor 234 and the mechanical load 240 into the form of mechanical work (e.g., for driving the mechanical load 240).

[0060] Inertia torque T J (t) can be calculated using equation (2), where J m+l is the predetermined inertia value, and ω(t) is the actual angular velocity of the rotor 234. The actual angular velocity of the rotor 234 may be monitored using a suitable rotor speed transducer, such as that described above with respect to Figure 3 The rotor sensing device 283 described. The rotor sensing device 283 can be configured to directly monitor the angular position of the rotor 234 and calculate the angular velocity of the rotor as the rate of change of the angular position of the rotor 234 relative to time t. The predetermined inertia value J m+l Corresponding to the inertia J of the motor 230 m (ie, the inertia of the rotor 234) and the inertia J of the mechanical load 240 l A combination of (for example, and).

[0061]

[0062] Based on this assumption, the torque T associated with driving the mechanical load 240 can be calculated using equation (3): l (t), where the torque T associated with the drive of the mechanical load 240 l (t) is set equal to the total torque T applied to the rotor 234 l (t) and inertia torque T J The torque T associated with the drive of the mechanical load 240 is l (t) can be called the total load torque T l (t).

[0063]

[0064] Equations (2) and (3) can be used separately Figure 5 That is, at block 512 the actual angular velocity ω(t) of the rotor 234 is accepted as a first input, and at block 514 the predetermined inertia value J is accepted. m+l As a second input, the total torque T applied to the rotor 234 is received at block 516 m (t) is used as the third input. The actual angular velocity ω(t) is differentiated at block 522 to give the rate of change dω(t) / dt of the actual angular velocity of the rotor 234. The rate of change dω(t) / dt of the actual angular velocity of the rotor 234 is multiplied by the predetermined inertia value J at block 524. m+l , to give the inertia torque T defined by equation (2) J (t). Then at box 526 the total torque T applied to the rotor 234 is m (t) minus the inertia torque T J (t), to give the total load torque T given by equation (3) l (t). Total load torque T l The calculation of (t) represents Figure 4 and Figure 5 The determination of the fluctuating speed demand ω represented by block 310 in d,f The first part of the motion (t). The total load torque T is calculated l (t) may be provided as an output at block 544 for use in other portions of method 300 according to the present disclosure and / or for other monitoring and / or control purposes with respect to motor 230 and / or electric drive device 200 .

[0065] Now refer to Figure 5 Each of the blocks 532-538 in FIG. 3 describes the determination of the fluctuating speed demand ω represented by block 310. d,f The second part of the action of (t). Determine the fluctuating speed demand ω d,f The underlying assumption of the second part of the action of (t) is that at any given point in time, the total power P drawn by the motor 230 is m Given by equation (4), where P J (t) is the inertial power, P l (t) is the power associated with (e.g., provided for) driving the mechanical load 240. The total power P drawn by the motor 230 m is substantially equal to the total mechanical power provided by the motor 230 (ignoring electrical losses in the motor 230), and the two may be referred to interchangeably herein. The power associated with the drive of the mechanical load 240 (e.g., provided for the drive of the mechanical load 240) may be referred to as the load power P l (t), and the total power P drawn or provided by the motor 230m Can be called motor power P m .

[0066] P m =P J (t)+P l (t) (4)

[0067] In equation (4), the load power P l (t) is expressed as a function of time t. In particular, due to the nature of the mechanical load 240, the load power P l (t) may be highly variable with respect to time. For example, if the mechanical load 240 is or includes Figure 3 , the power associated with the drive of the compressor 402 (i.e., the load power P) is changed due to the change in the rate of change of the mechanical work done on the working fluid provided to the compression during the compression cycle. l (t)) may vary throughout the compression cycle of the compressor 402. If the compressor 402 is a reciprocating compressor, the power associated with the drive of the compressor 402 may vary significantly throughout the compression cycle of the compressor 402. Those skilled in the art will appreciate that other types of mechanical loads may also result in a load power P that varies with respect to time. l (t).

[0068] In addition, in order to determine the fluctuation speed requirement ω d,f (t) in the second part, according to equation (5), the load power P l (t) is considered to be composed of the fluctuating power component P l,f (t) and an average (eg, constant) power component P l,a Of these two components, only the fluctuating power component P l,f (t) is a function of time t.

[0069] P l (t) = P l,f (t)+P l,a (5)

[0070] Similarly, according to equation (6), the total load torque T l The fluctuating load torque component T l,f (t) and the average (eg, constant) load torque component T l,a Similarly, among these components, only the fluctuating load torque component T l,f (t) is a function of time t.

[0071] T l (t) = T l,f (t)+T l,a (6)

[0072] In order to be able to determine the total power P drawn by the motor 230, at least partially eliminating (eg, reducing) m The fluctuation speed of the change in demand ω d,f (t) is the rotor speed reference value ω d,r (t), according to equation (7a), the inertial power P J (t) is set equal to the fluctuating power component P l,f (t). That is, the fluctuating power component P l,f (t) is considered to be completely determined by the inertial power P J (t) provides. This means that the total power P drawn by the motor 230 m The combined inertia of the rotor 234 and the mechanical load 240 is used as energy storage.

[0073] P J (t) = P l,f (t) (7a)

[0074] Noting that rotational power is by definition equal to the product of torque and rotational speed, equation (7a) can be written in the form of equation (7b).

[0075] T J (t)×ω(t)=T l,f (t)×ω(t)∴T J (t) = T l,f (t) (7b)

[0076] Furthermore, substituting equation (2) into equation (7b) yields equation (7c), where ω d,r (t) is the fluctuating speed demand appropriately determined as discussed above. Then, equation (7c) is rearranged to give the fluctuating speed component ω f The expression of (t) is shown in equation (7d).

[0077]

[0078] Due to the fluctuating load torque component T l,f (t) is equal to the total load torque T l (T) and the constant load torque component T l,a The difference is , so rearrangement and reconstruction of equation (5) gives equation (8), which in turn can be substituted into equation (7d) to give equation (9).

[0079]

[0080] Equations (7d) and (8) are respectively expressed by Figure 5 That is, at box 532, the total load torque T l(T) is averaged to give a constant load torque component T l,a At block 532 the total load torque T l The average of (t) can be calculated by calculating the total load torque T received during the appropriate time period before the current time l The total load torque T at block 532 is used to calculate the arithmetic mean of the bounded time series of values ​​of (t). l Other techniques for averaging (T) will be apparent to those skilled in the art and may be used in accordance with method 300. Then at box 534, the total load torque T l (T) minus the constant load torque component T l,a , to give the fluctuating load torque component T defined by equation (8) l,f (T). Then, at box 536, the fluctuating load torque component T l,f (t) is integrated to give the fluctuating load torque component T l,f The time integral of (t)∫(T l,f At block 538, the fluctuating load torque component T l,f The time integral of (t)∫(T l,f (t))dt divided by the predetermined inertia value J m+l To generate fluctuating speed demand ω d,f (t) for at least partially reducing the motor power P m (i.e., the total power drawn or supplied by the motor 230, as the case may be). Then at box 542, the fluctuating speed demand ω is provided d,f (t) as an output for use in the subsequent steps of method 300 (ie, block 330).

[0081] According to method 300 , energy is selectively converted between the rotational kinetic energy of rotor 234 and mechanical load 24 to allow motor power P m remains essentially constant, while the load power P l (t) varies with respect to time. The rate at which energy is converted between the rotational kinetic energy of the rotor 234 and the mechanical load 240 therefore corresponds to the inertial power P J (t). In the previously considered electric drive device, due to the motor power P m Due to the changes in the motor power P and the lack of ability of the power source (e.g., the grid converter) to provide a corresponding variable amount of power to the DC bus, the operating voltage of the DC bus 210 is prone to significant changes with respect to time. To address this problem, a relatively large energy storage device (i.e., a large capacitor) is functionally provided for the DC bus 210 to smooth the changes in the operating voltage of the DC bus 210. The electric drive device 200 controlled according to the example method 300 described herein does not exhibit a motor power Pm , so the operating voltage of DC bus 210 will generally be stable without providing a relatively large electrical energy storage device for DC bus 210. Therefore, compared with previously considered electric drive devices, electric drive device 200 according to the present disclosure can be lighter, less expensive, and / or have a lower parts count.

[0082] Figure 6 A machine-readable medium 600 is shown highly schematically, on which is stored a computer program 60 comprising instructions which, when arranged to be transmitted to an electric drive device (according to the above referenced Figure 3 When the controller 290 of the example electric drive device 200 described above executes, the controller 290 executes the above reference Figure 4 and Figure 5 Method 300 is described.

[0083] Features described with respect to any of the above aspects may be applied mutatis mutandis to any other aspect, except where mutually exclusive. Furthermore, any feature described herein may be applied to any aspect and / or combined with any other feature described herein, except where mutually exclusive. Furthermore, while the present disclosure is made in the context of transport refrigeration systems and / or vapor compression circuits, it will be appreciated that the present disclosure has other possible applications in other technical fields.

[0084] Furthermore, although the method 300 is described herein with reference to the motor 230 forming part of the electric drive device 200, it should be understood that the principles described herein have applications beyond this technical application. As an example, many of the principles described herein may be used to control an electric motor in the form of a heat engine, such as a spark ignition (e.g., Otto cycle engine) engine or a compression ignition (e.g., diesel cycle) engine, with any necessary adjustments, which will be apparent to those skilled in the art. If so, the rotor 234 may form part of or be a rotating assembly 234 of the engine (i.e., crankshaft), and the mechanical load 240 may form part of or be a piston 240 of the engine. If so, a fluctuating speed requirement as described herein may be determined to reduce the variation in the total mechanical power (e.g., brake power or shaft power) provided by the motor 230 (i.e., engine) via the crankshaft during use. The motor 230 may be controlled by various actuators (e.g., valves and / or crankshaft drive devices) disposed on the engine 230 according to a rotating assembly speed reference value ω r,d Implementing method 300 in this manner can reduce or eliminate the need to couple a large and / or heavy flywheel to the crankshaft to reduce variations in mechanical power (e.g., brake power or shaft power) provided by motor 230 (i.e., engine) during use.

Claims

1. A method of operating an electric machine having a rotating assembly coupled to a mechanical load, the method comprising: Determine the fluctuating speed demand ω corresponding to the time-varying component of the speed ω(t) of the rotating component f,d (t); Determine a rotating component speed reference value ω based on the fluctuating speed demand r,d (t); as well as The motor is controlled according to the rotating component speed reference, where The fluctuating speed demand is determined to reduce variations in total power drawn or provided by the electric machine in use.

2. The method according to claim 1, wherein: Rotating component speed reference value ω r,d (t) According to the fluctuation speed demand ω f,d (t) varies with respect to time.

3. The method according to claim 1, comprising: Based on the predetermined inertia value J m+l , the speed of the rotating component ω(t) and the total torque T applied to the rotating component m (t) to calculate the torque (T l (t)); and The fluctuating speed demand ω is determined based on a predetermined inertia value and a torque associated with the drive of the mechanical load. f,d (t).

4. The method according to claim 3, wherein: The predetermined inertia value J m+l Corresponds to the combination of the inertia of the rotating components and the inertia of the mechanical load.

5. The method according to claim 3, comprising: Based on the predetermined inertia value J m+l , the rate of change of the speed of the rotating component dω(t) / dt and the total torque T applied to the rotating component m (t) Calculate the torque T associated with the drive of the mechanical load l (t).

6. The method according to claim 5, comprising: By setting the predetermined inertia value J m+l Multiply by the rate of change of the speed of the rotating component dω(t) / dt to calculate the inertia torque T J (t); as well as The torque T associated with the drive of the mechanical load is calculated by subtracting the inertia torque from the total torque applied to the rotating component. l (t).

7. The method according to claim 6, wherein: Calculate the torque T associated with the drive of a mechanical load l (t) includes setting the torque associated with the drive of the mechanical load equal to the total torque T applied to the rotating component m (t) minus the inertia torque T J (t).

8. The method according to claim 3, comprising: By associating the torque T associated with the drive of the mechanical load l The fluctuation component T of (t) l,f The time integral of (t) is divided by the predetermined inertia value J m+l To determine the fluctuation speed requirement.

9. The method according to claim 1, comprising: Determine or receive an average speed demand ω corresponding to a constant component of the speed ω(t) of the rotating component a,d (t); as well as Based on average speed demand and fluctuating speed demand ω f,d (t) to determine (330) the rotating component speed reference value ω r,d (t).

10. An electric drive device comprising: a controller adapted to perform a method according to any preceding claim; as well as An electric machine has a rotating assembly coupled to a mechanical load.

11. The electric drive device according to claim 10, further comprising a power converter, wherein: The electric machine is configured to draw AC power or DC power from the power converter in use.

12. The electric drive device according to claim 11, further comprising a DC bus, wherein: The power converter is configured to receive an input DC input voltage from a power source via a DC bus.

13. A transport refrigeration system comprising an electric drive device according to claim 10 and a vapor compression refrigeration circuit comprising a compressor, wherein: Mechanical loads include compressors.

14. A computer program comprising instructions which, when executed by a controller of an electric drive device according to claim 10, cause the controller to perform the method according to claim 1.

15. A machine-readable medium having stored thereon a computer program according to claim 14.

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