WO2019025628A1

WO2019025628A1 - Controller system for and method of operating a multiphase switched reluctance machine, and a correction unit

Info

Publication number: WO2019025628A1
Application number: PCT/EP2018/071253
Authority: WO
Inventors: Qiong-zhong CHEN; Steven BERVOETS; Gianluca BARBIERATO
Original assignee: Punch Powertrain N.V.
Priority date: 2017-08-04
Filing date: 2018-08-06
Publication date: 2019-02-07
Also published as: DE112018003980T5; BE1025445B1; CN111108680A; BE1025445A1

Abstract

The present document relates to a controller system for operating a multiphase switched reluctance machine comprising a stator and a rotor, the rotor being rotatable relative to the stator. Each coil of the stator is associated with a phase stage, such that each phase stage is associated with a plurality of stator coils. The controller system is arranged for powering the phase stages by subsequently applying a phase current to each of the phase stages. For each phase stage the phase current is applied by switching on the phase current in a first position of a counter pole relative to a stator pole, and switching off the phase current in a second position of the counter pole. The controller comprises a torque distribution unit determining a desired torque output to be delivered by each phase stage for providing the desired torque output, and a correction unit for correcting the determined desired torque output, for enabling building up said phase current for enabling the phase stage to effectively deliver the desired torque output as determined by the torque distribution unit. The document also describes a method.

Description

Controller system for and method of operating a multiphase switched reluctance machine, and a correction unit. Field of the invention

The present invention is directed at a controller system for operating a multiphase switched reluctance machine, the multiphase switched reluctance machine comprising a stator including a plurality of coils and stator poles wherein the stator poles form the cores of the coils, and a rotor including a plurality of counter poles for interacting with the stator poles for applying a reluctance torque on the rotor, the rotor being rotatable relative to the stator, the coils being associated with a plurality of phase stages of the multiphase switched reluctance machine such that each coil of the stator is associated with one phase stage, each phase stage thereby being associated with one or more of the plurality of coils of the stator; wherein the controller system is arranged for powering the phase stages by subsequently applying a phase current to each of the phase stages respectively such as to apply the reluctance torque to the rotor, wherein for each phase stage the phase current is applied by: switching on the phase current in a first position of a counter pole relative to a stator pole of said phase stage, and switching off the phase current in a second position of the counter pole relative to the stator pole of said phase stage; wherein the controller system further comprises a torque distribution unit configured for determining for each phase stage a desired torque output to be delivered by said phase stage, wherein the torque distribution unit comprises an output for providing the determined desired torque output for the respective phase stage. The invention is further directed at a method of operating a multiphase switched reluctance machine.

Background

This disclosed invention relates to the control of switched reluctance (SR) motors, and more particularly to a predictive phase current buildup method to extend the torque-ripple-free applicable range of the pulse width modulation (PWM) based direct instantaneous torque control (DITC), i.e. PWM-DITC. The DITC strategy with hysteresis control for SR motors was originally published by Robert B. Inderka et al. in "DITC- direct instantaneous torque control of switched reluctance drives", IEEE Transactions on Industry Applications (Volume: 39, Issue: 4, July-Aug. 2003), and then it was further developed as PWM- based DITC strategy by Christoph R. Neuhaus et al. as published in "Predictive PWM-based direct instantaneous torque control of switched reluctance drives"; 37th IEEE Power Electronics Specialists Conference, 2006 (PESC Ό6), 18-22 June 2006. It is closed-loop control of the electromagnetic torque using the feedback of torque estimation calculated from look up tables (LUTs). There is a mechanism to distribute the requested torque over two adjacent phases in case that both of them come into effective. The phase that newly becomes active is called the incoming phase, while the phase that will be newly phasing out is called the outgoing phase. The incoming phase by default has higher priority over the outgoing phase, which means that the incoming phase will deliver the requested torque, unless one of the following two exceptions occurs: the requested torque is out of the estimated range of feasible torque that can be possibly delivered by the incoming phase; the estimated torque in the outgoing phase in the coming time step cannot diminish to zero. In one of the above two exceptions, the torque distribution strategy will recalculate torque request for these two adjacent phases accordingly.

The incoming phase is controlled such as to always deliver the torque in the same direction as the requested torque, such as to not counteract the torque delivered in the outgoing phase. For that reason the phase current is allowed to be built up as soon as the respective incoming phase is able to deliver torque in the requested direction. The DITC strategy has led to a considerable improvement in motor performance in terms of minimization of torque ripple, in particular at low and medium speeds. However, at higher speeds, torque ripple still occurs in PWM- DITC controlled SR motors. This is due to the fact that the back electromagnetic force (EMF) is proportional to the rotor speed, while the time for building up the phase current is inversely proportional to the rotor speed. Thus, at low speeds, the phase current can be easily built up to a targeted value with respect to the rotor position. However, at higher speeds, the targeted phase current cannot be easily followed anymore. Although the above has been described with reference to switched reluctance motors, the problem also occurs with SR generators. Summary of the invention

It is an object of the present invention to provide a solution to the above described disadvantages experienced in pulse width modulation based direct instantaneous torque control operated switched reluctance motors or generators, and to provide a control system and method that allows to further reduce torque ripple at higher rotor speeds.

To this end, there is provided herewith a controller system for operating a multiphase switched reluctance machine, the multiphase switched reluctance machine comprising a stator including a plurality of coils and stator poles wherein the stator poles form the cores of the coils, and a rotor including a plurality of counter poles for interacting with the stator poles for applying a reluctance torque on the rotor, the rotor being rotatable relative to the stator, the coils being associated with a plurality of phase stages of the multiphase switched reluctance machine such that each coil of the stator is associated with one phase stage, each phase stage thereby being associated with one or more of the plurality of coils of the stator; wherein the controller system is arranged for powering the phase stages by subsequently applying a phase current to each of the phase stages respectively such as to apply the reluctance torque to the rotor, wherein for each phase stage the phase current is applied by: switching on the phase current in a first position of a counter pole relative to a stator pole of said phase stage, and switching off the phase current in a second position of the counter pole relative to the stator pole of said phase stage; the controller system further comprising a torque distribution unit configured for determining for each phase stage a desired torque output to be delivered by said phase stage, wherein the torque distribution unit comprises an output for providing the determined desired torque output for the respective phase stage; wherein the controller system further comprises a correction unit

cooperating with the torque distribution unit for receiving the determined desired torque output for the respective phase stage, the correction unit comprising an input for receiving current position data indicative of a current position of the counter pole relative to the stator pole of the respective phase stage, and wherein the correction unit is configured for correcting the determined desired torque output for the respective phase stage such as to provide a corrected desired torque output associated with said current position of the counter pole relative to the stator pole, for enabling building up said phase current through said respective phase stage for enabling the phase stage to effectively deliver the desired torque output as determined by the torque distribution unit.

Underlying the present invention, there is the insight that a certain amount of counteracting of torque delivered by the outgoing phase, due to early building up of the phase current in the incoming phase, may be used to remove the occurrence of a torque dip upon commutation of the phases. In order to output a higher torque, phase current should be built up high enough before it goes to the effective torque generation region. If necessary, the phase will be energized even before it reaches the unaligned position. Thus a small amount of negative torque is allowed as a tradeoff for building up the phase current. The advantage is that when the rotor approaches the region with effective torque generation, more torque will be extracted due to a higher phase current. By early building up of the phase current in the incoming phase, i.e. prior to the current rotor position of 180°elec with respect to the incoming phase (i.e. 180°elec is the position in electrical scale wherein the stator pole of the said phase stage is located exactly in the middle between two consecutive counter poles of the rotor: i.e. the unaligned position), the phase current is able to build up early enough to enable providing sufficient torque output to prevent a torque dip upon commutation of phases. Prior to the rotor position 180°elec described above, the counteraction effect of the incoming phase is compensated by the outgoing phase; after the rotor position 180°elec, due to the early built-up phase current, the torque from the incoming phase is fast built-up and can thus compensate the torque dip from the outgoing phase. As a result, the torque dip during commutation is avoided in the total torque summarized from all phases. This allows to operate the SR motor to be operated free of torque ripple at much higher rotor speeds, because of the additional time available for phase current build up during commutation.

In accordance with some embodiments, the controller system is a closed- loop system, and wherein the controller system comprises a monitoring unit configured for receiving data indicative of one or more operational parameters of the switched reluctance machine. Based on the operational parameters, the controller is able to perform torque distribution and to provide the correction unit with input for correcting the determined desired torque output for the respective phase stage. In accordance with some of these embodiments, the one or more operational parameters include at least one element of a group comprising: an actual phase current applied to one or more of the phase stages, an angular rotor position of the rotor relative to the stator, a rotation velocity of the rotor; or a DC voltage level available for said powering.

Furthermore, in accordance with some embodiments, the controller system is arranged for providing the correction unit with data indicative of the first position (θοη) and the second position (0_Off) for the respective phase stage. The controller further provides the current position of the rotor (GphN), or at least provides data or a signal from which the current rotor position may be obtained. Such position information (θοη, Qos, GphN) may be provided for the respective phase in terms of an electrical phase angle, i.e. indicating the relative position of the counter pole of the rotor between two consecutive stator poles of a single phase. An electrical phase angle of 0°elec indicates an aligned position between a counter pole of the rotor and a stator pole of the respective phase. An electrical phase angle of 180°elec corresponds with the unaligned position, wherein the stator pole of a phase stage is exactly in the middle in between two counter poles of the rotor, as described earlier above. An electrical position of 360°elec indicates an aligned position with a following counter pole of the rotor aligned with the stator pole of the respective phase. The phase's first and second position, i.e. the switch-on and switch-off positions may dependent on at least one of the one or more operational parameters. Hence, based on the present conditions, an optimal first or second position of the rotor for respectively switching on or switching off the stator poles of a phase will be determined by the controller system. How the switch-on and switch- off angles may be determined depends on optimization. For example, the switch-on angle can be optimized taking into account e.g. torque ripple, efficiency and noise (reflection of radial force). The switch- off angle may for example be fixed as

360°elec for motoring and 180°elec for generating.

In accordance with some of these embodiments, the controller system includes or is communicatively connected to a data store, the data store including a lookup table for associating the at least one of the one or more operational parameters with one or more of the first and second position. The lookup table may be pre-stored in a memory or otherwise be accessible to the controller system. Such a lookup table may have been predetermined for motor (or generator) during an initialization process, associating the operational conditions that correspond with the operational parameters with optimal switch-on and switch-off angles for minimizing torque ripple.

In accordance with various embodiments of the invention, the torque distribution unit is configured for determining the desired torque outputs to be delivered by adjacent phase stages when the counter pole moves from a first one of the adjacent phase stages to a second one of the adjacent phase stages. The torque distribution unit in such embodiments is configured for providing a first desired torque output for the first one of the adjacent phase stages and a second desired torque output for the second one of the adjacent phase stages. The correction unit is configured for correcting at least one of the first or second desired torque output. In these embodiments, a desired torque output for any of the two or both of the adjacent phase stages may be corrected.

In accordance with some embodiments of the invention, the multiphase switched reluctance machine is at least one of a switched reluctance motor or a switched reluctance generator.

The invention, in accordance with a second aspect thereof, provides a correction unit for use in a controller system according to any of the preceding claims, the correction unit is configured for cooperating with a torque distribution unit for receiving a determined desired torque output for a phase stage, the correction unit comprising an input for receiving a current position data indicative of a current position of at least one counter pole relative to a stator pole of the phase stage, and wherein the correction unit is configured for correcting the determined desired torque output for the phase stage such as to provide a corrected desired torque output associated with said current position of the counter pole relative to the stator pole, for enabling building up said phase current through said phase stage for enabling the phase stage to effectively deliver the desired torque output as determined by the torque distribution unit.

The invention, in accordance with a second aspect thereof, provides a method of controlling operation of a multiphase switched reluctance machine, the multiphase switched reluctance machine comprising a stator including a plurality of coils and stator poles wherein the stator poles form the cores of the coils, and a rotor including a plurality of counter poles for interacting with the stator poles for applying a reluctance torque on the rotor, the rotor being rotatable relative to the stator, the coils being associated with a plurality of phase stages of the multiphase switched reluctance machine such that each coil of the stator is associated with one phase stage, each phase stage thereby being associated with one or more of the plurality of coils of the stator; the method comprising the steps of: powering, by a controller system, the phase stages by subsequently applying a phase current to each of the phase stages respectively such as to apply the reluctance torque to the rotor, wherein for each phase stage the phase current is applied by: switching on the phase current in a first position of a counter pole relative to a stator pole of said phase stage, and switching off the phase current in a second position of the counter pole relative to the stator pole of said phase stage; determining for at least one phase stage of the phase stages, using a torque distribution unit, a desired torque output to be delivered by said at least one phase stage, and providing the determined desired torque output for the respective phase stage to a correction unit; receiving, by the correction unit, the determined desired torque output for the respective phase stage and current position data indicative of a current position of the counter pole relative to the stator pole of the respective phase stage; and correcting, by the correction unit, the determined desired torque output for the respective phase stage such as to provide a corrected desired torque output associated with said current position of the counter pole relative to the stator pole, for enabling building up said phase current through said respective phase stage for enabling the phase stage to effectively deliver the desired torque output as determined by the torque distribution unit.

Brief description of the drawings

The invention will further be elucidated by description of some specific embodiments thereof, making reference to the attached drawings. The detailed description provides examples of possible implementations of the invention, but is not to be regarded as describing the only embodiments falling under the scope. The scope of the invention is defined in the claims, and the description is to be regarded as illustrative without being restrictive on the invention. In the drawings: Figure 1 schematically illustrates a closed loop controller system in accordance with an embodiment of the invention, for controlling a switched reluctance (SR) motor;

Figure 2 schematically illustrates a conventional torque distribution unit;

Figure 3 schematically illustrates a torque distribution unit in accordance with an embodiment of the present invention;

Figure 4 illustrates an angle convention for a forward and backward direction of a switched reluctance motor;

Figure 5 schematically illustrates for a switched reluctance generator, the current, phase torque and total torque waveforms versus electrical position with and without a predictive current buildup mechanism;

Figures 6 and 7 are graphs illustrating the applicable operational ranges for an SR motor with and without predictive phase current buildup.

Detailed description

A closed loop controller system 1 for controlling a switched reluctance (SR) motor 3 is schematically illustrated in figure 1. DC bus voltage and phase current voltages of each one of the respective phase stages of the switched reluctance (SR) motor 3 are measured and provided to measurement and estimation element 5. Measurement and estimation element 5 also receives the rotor position signal, which may for example be obtained using a position encoder (not shown) in the SR motor 3. From the obtained phase currents and the rotor position, the flux linkage of each phase stage of the motor 3 is estimated.

The estimated flux linkages 8-4, the position of the rotor 8-3, and the measured phase currents 8-1 and DC bus voltage 8-2 are passed on to the torque estimation unit 7. The torque estimation unit 7 is used to predict the range of the deliverable phase torque of the respective phase. Torque estimation unit 7 may apply an algorithm and/or a look-up table from a memory (not shown) or other data repository (not shown).

The estimated phase torque values 10 are provided to the torque distribution unit 15, which also receives the reference torque value 12. The torque distribution unit 15 will be explained in more detail further below. At the output of the torque distribution unit 15, reference phase torque values 27 and 29 for the respective phase stages are provided to a reference phase flux linkage control unit 17. The reference phase flux linkage control unit 17 calculates the reference phase flux linkage values 20 for the respective phase stages, and comparator 18 determines the difference Au/ph between the reference phase flux linkage u/phref and the estimated phase flux linkage 8-4. This difference AuJph, together with the DC bus voltage 8-2 and phase current 8- 1 is passed on to the pulse width modulator (PWM) 19 to determine a PWM duty cycle, which is passed on as an input signal Bsw to the power converter 4 for driving the SR motor 3. In fact, the difference signal AuJph is an output of the controller system 1 and is indicative of a difference between the desired amount of phase flux linkage u/phref and the actual present (i.e. estimated) phase flux linkage 8-4. Based on this difference, the PWM signal B_sw is set to control the power converter 4.

Figure 2 illustrates a conventional torque distribution unit 115. The conventional torque distribution unit 115 in a conventional controller system could be in the same position as torque distribution unit 15 (figure 1) in the present invention, i.e. following torque estimation unit 7 in the closed loop. The torque distribution unit 115 receives the estimated torque values 10- 1 and 10-2. As illustrated in figure 2, the estimated torque value 10- 1 is for the outgoing phase stage (i.e. phase N- l) and estimated torque value 10-2 is for the incoming phase stage (i.e. phase N). As described earlier in this document, the incoming phase N has always higher priority over the outgoing phase N- l, which means that the incoming phase N will deliver the requested torque, unless an exception occurs. There are two of such exceptions: firstly the requested torque is out of the estimated range of feasible torque that can be delivered by the incoming phase; and secondly the estimated torque in the outgoing phase in the coming time step cannot diminish to zero (i.e. the outgoing phase stage N- l still delivers an amount of torque and cannot cease to do that yet). In the above two exceptions, the torque distribution strategy will re-calculate torque request for these two adjacent phases accordingly.

The priority of the incoming phase N over the outgoing phase N- l is reflected in figure 2 by placing the phase torque controller 22 for the incoming phase N upstream of the phase torque controller 24 for the outgoing phase N- l. The phase torque controller 22 for the incoming phase N receives the reference torque value T_ref* from signal 12 as well as the estimated phase torque ranges Test min phN and Test max phN from signal 10-2, and based thereon determines the torque output T₀ut,N for incoming phase N. It then determines the residual reference torque preferred to be delivered by the outgoing phase N-1, by

subtracting T_out,N from T_rep, to yield T_ref**. This value T_ref** is passed on to the phase torque controller 24 for the outgoing phase N-1, which also receives the estimated phase torque ranges Test_min_phN-i and T est_max_phN-l from signal 10-1. Based thereon, the phase torque controller 24 determines the reference phase torque value T_ref,N-i for the outgoing phase N-1. The reference phase torque value T_ref,N for the incoming phase N is obtained by subtracting T_ref,N-i from T_ref* in comparator 25. These values Tref,N and Tref,N-i are passed on as signals 27 and 29 respectively to the reference phase flux linkage control unit 17 in figure 1.

As the torque is estimated and monitored online and the duty cycle for each phase is predicted accordingly, the torque ripple is generally small as a result. However, in order to deliver the requested constantly smooth torque, the following condition should be met:

Test min phN ^~t^~ Test_min_phN-l ^ Tref* ^ Test max phN ^~t^~ Test_max_phN-l (Eq.l)

The incoming phase will always deliver the torque in the same direction as the requested torque unless one of the following two situations occurs

0 < T^'nf — Tefl KrimjM-l

(Eq.2)

This means that the outgoing phase will have to deliver the torque more than requested and the incoming phase has to counter compensate it. In practice, neither of the above situations will occur. Therefore, the phase current in the incoming phase is allowed to build up only when it delivers the torque in the same direction as the requested torque. Consider for example a forward motoring configuration, wherein the phase current can only be built-up as of a rotor position GphN of 180°. This generally restrains the duration for building up the phase current before it goes to the effective torque generation region, especially with the increase of the rotor speed. The back EMF is proportional to the rotor speed, while the time for building up the phase current is inversely proportional to the rotor speed. Thus, at low speeds, the phase current can be easily built up to a targeted value with respect to the rotor position. However, at higher speeds, the targeted phase current cannot be easily tracked anymore. Thus, it can lead to the following situations:

There are two consequences coming out of this: firstly, torque ripple will occur in case that the incoming phase cannot build up an necessary amount of torque. This is usually detected as a torque dip at the commutations. Secondly, the maximum total torque of the motor will drop due to the torque dip at phase commutation.

The present invention solves the above disadvantage of the conventional torque distribution unit. It investigates on the switching strategy and predictively allows the incoming phase to build up its phase current beforehand so that the Eq.3 will not occur and Eq.l can be fulfilled with a substantially extended range of rotor speed, i.e., the PWM-DITC is applicable to a more extended range for non- torque-ripple operation.

In figure 3, a torque distribution unit 15 in accordance with an embodiment of the present invention is illustrated. The torque distribution unit 15 includes an additional element that performs the predictive phase current buildup correction on the reference phase torque values 27 and 29 provided at the output. This correction is performed by the predictive phase current buildup unit 30, located in the control circuit loop downstream of the phase torque controller 22 for the incoming phase N. The predictive phase current buildup unit 30 receives the determined torque output T_out,N for incoming phase N, as well as the switch-on angle θοη, the switch-off angle 0_Off and the present actual position of the rotor 0_PhN relative to the stator coils of the incoming phase N. The switch-on angle θοη and the switch-off angle 0_Off may be obtained in different manners, for example these may be set at preferred fixed values, calculated or controlled using an algorithm or certain rules via an additional controller (not shown) or may be pre- stored in a lookup table (not shown) and obtained therefrom (e.g. dependent on operation conditions, such as motor speed). How to choose switch-on and switch-off angles depends on optimization. The switch-on angle can be optimized taking into account of torque ripple, efficiency and noise (reflection of radial force). The switch-off angle can be fixed, such as 360°elec for an SR motor 3 or 180°elec for an SR generator system. The predictive phase current buildup unit 30, based on it's inputs discussed above, determines a corrected torque output T_out*,N for the incoming phase N.

In order to output a higher torque, phase current should be built up high enough before it goes to the most effective torque generation region. If necessary, the phase will be energized even before it reaches the unaligned position. Thus a small amount of negative torque is allowed as a tradeoff for building up the phase current. The advantage is that when the rotor approaches the region with effective torque generation, more torque will be extracted due to a higher phase current.

To further analyze the feasibility of this scheme, let us first define the following angle convention 38 in figure 4. In the aligned positions 39 and 40, the electrical position is either 0 [°elec] or 360 [°elec]. Consequently, the position at the unaligned position is 180 [°elec], in between 39 and 40. Figure 4 also illustrates the convention for a forward and backward direction of the motor 3. The torque distribution mechanism of the present invention, e.g. as illustrated in figure 3, is improved with a predictive phase current buildup unit 30. The saturation output Tout,N of the requested torque on the incoming phase N is fed into the predictive phase current buildup unit 30. The phase angular position 0_PhN, switch-on angle θ_οη and switch-off angle 0_Off are the inputs 32, 33 and 34 to determine whether the phase current needs to be built up early.

The preliminary torque output on the incoming phase, denoted as T_out*,N is thus recalculated as shown in the following tables for the motoring and generating states respectively. GphN [elec°] [θοη, 180°) [180°, Goff)

Tout* [Nm] Test_max_phN, if | Test_max_phN | ^ | Test_min_phN | Tout,N

or

Test_min_phN, if | Test_max_phN | ^ | Test_min_phN |

Table 1 - Motoring states

GphN [elec°] [θοη, 360°) [360°, Goff)

Tout* [Nm] Test_max_phN, if | Test_max_phN | ^ | Test_min_phN | Tout,N

or

Test_min_phN, if | Test_max_phN | ^ | Test_min_phN |

Table 2 - Generating states

In the above tables 1 and 2, Test_min _phN and Test_max _phN denote the lower and upper limits of estimated deliverable torque from the incoming phase N respectively. The polarity of T_est_min _phN and T_est_max _phN will change if the inflection point is estimated to be crossed over (180 [°elec] or 360 [°elec]). Therefore,

Test min _phN and Test_max _phN may range from negative to positive. In the phase current build-up region, which is [θοη, 180°) for motoring or [θοη, 360°) for

generating, the desired preliminary torque output will always take the value of the estimated limit that has the maximum absolute value. In this way, the phase current can be effectively built up at its utmost.

With this adaption, the phase current is then allowed to be built up before it starts to deliver effective phase torque. The switch-on angles however preferably are to be optimized and are preferably calculated offline according to the operating points and stored as lookup tables to be looked up during online calculation. The optimization takes into account objectives such as efficiency, torque ripple as well as the radial force change rate. The fitness function is composed of as below:

' Γ I D D I* pores

FiinessFunctian— ntim _ _¾g_

1 + H%

^sff _mcx I

With Here, E_eff is the motor efficiency; T_ri_PPie is the peak-peak torque ripple; AFforce is the gradient change of radial force; the subscript 'max' indicates the maximum physical components accordingly for all combinations of on/off angles for a specified operating point. The weighted factors for the efficiency, torque ripple and gradient change of radial force are denoted by WE, WT, and WF respectively.

Figure 5 illustrates for a switched reluctance generator, the current, phase torque and total torque waveforms in time scale with and without a predictive current buildup mechanism, such as element 30 in figure 3. The motor 3 operates at a speed of 3840rpm, providing a requested torque of -90Nm. Figure 5 shows the difference with and without a predictive current build-up mechanism for a generating operating point. Without the predictive current build-up, the switch- on behavior of the said phase occurs obligatorily on the falling slope of the L-curve. That is, the phase current can be built up only after 0°elec (i.e., 360°elec). In this considerable torque dip can be seen during commutation (continuous curve) which is absent in the curve (dashed curve) of the predictive current build-up mechanism of the invention. Note that in figure 5, waveforms from only one phase stage are shown. With three phase stages, the curves of the illustrated phase in figure 5 are to be overlapped by the other two phases with a phase difference of

120°elec for each phase. Also figure 5, with the predictive current build-up (dashed curve), the current starts to build up at 300°elec. This is at the cost of a small amount of opposite torque at start, but the gain is the smooth torque delivery over commutation as well as improved efficiency.

In figures 6 and 7, the applicable operational range with and without predictive phase current buildup is illustrated. Figure 6 shows the applicable operational range in forward motoring; Figure 7 shows the applicable operational range in forward generating. As can be seen, e.g. in figure 6, in the situation of profile curve 65 including the predictive phase current buildup of the invention, a more constant amount of torque can be delivered over an extended range of speed, without the torque fall-off shown in profile curve 62. As can be seen, e.g. in figure 7, in the situation of profile curve 74 including the predictive phase current buildup of the invention, a much wider range of torque versus speed can be delivered compared to the profile curve 70 that does not include the predictive phase current buildup. It should be noted that the profile curves can vary dependent on the acceptance criteria of the torque ripple bandwidth etc.

The present invention has been described in terms of some specific embodiments thereof. It will be appreciated that the embodiments shown in the drawings and described herein are intended for illustrated purposes only and are not by any manner or means intended to be restrictive on the invention. It is believed that the operation and construction of the present invention will be apparent from the foregoing description and drawings appended thereto. It will be clear to the skilled person that the invention is not limited to any embodiment herein described and that modifications are possible which should be considered within the scope of the appended claims. Also kinematic inversions are considered inherently disclosed and to be within the scope of the invention. Moreover, any of the components and elements of the various embodiments disclosed may be combined or may be incorporated in other embodiments where considered necessary, desired or preferred, without departing from the scope of the invention as defined in the claims.

In the claims, any reference signs shall not be construed as limiting the claim. The term 'comprising' and 'including' when used in this description or the appended claims should not be construed in an exclusive or exhaustive sense but rather in an inclusive sense. Thus the expression 'comprising' as used herein does not exclude the presence of other elements or steps in addition to those listed in any claim. Furthermore, the words 'a' and 'an' shall not be construed as limited to 'only one', but instead are used to mean 'at least one', and do not exclude a plurality. Features that are not specifically or explicitly described or claimed may be additionally included in the structure of the invention within its scope.

Expressions such as: "means for ..." should be read as: "component configured for ..." or "member constructed to ..." and should be construed to include equivalents for the structures disclosed. The use of expressions like: "critical", "preferred", "especially preferred" etc. is not intended to limit the invention. Additions, deletions, and modifications within the purview of the skilled person may generally be made without departing from the spirit and scope of the invention, as is determined by the claims. The invention may be practiced otherwise then as specifically described herein, and is only limited by the appended claims

Claims

1. Controller system for operating a multiphase switched reluctance machine,

the multiphase switched reluctance machine comprising a stator including a plurality of coils and stator poles wherein the stator poles form the cores of the coils, and a rotor including a plurality of counter poles for interacting with the stator poles for applying a reluctance torque on the rotor, the rotor being rotatable relative to the stator, the coils being associated with a plurality of phase stages of the multiphase switched reluctance machine such that each coil of the stator is associated with one phase stage, each phase stage thereby being associated with one or more of the plurality of coils of the stator;

wherein the controller system is arranged for powering the phase stages by subsequently applying a phase current to each of the phase stages respectively such as to apply the reluctance torque to the rotor, wherein for each phase stage the phase current is applied by:

switching on the phase current in a first position of a counter pole relative to a stator pole of said phase stage, and

switching off the phase current in a second position of the counter pole relative to the stator pole of said phase stage;

the controller system further comprising a torque distribution unit configured for determining for each phase stage a desired torque output to be delivered by said phase stage, wherein the torque distribution unit comprises an output for providing the determined desired torque output for the respective phase stage;

wherein the controller system further comprises a correction unit cooperating with the torque distribution unit for receiving the determined desired torque output for the respective phase stage, the correction unit comprising an input for receiving current position data indicative of a current position of the counter pole relative to the stator pole of the respective phase stage, and wherein the correction unit is configured for correcting the determined desired torque output for the respective phase stage such as to provide a corrected desired torque output associated with said current position of the counter pole relative to the stator pole, for enabling building up said phase current through said respective phase stage for enabling the phase stage to effectively deliver the desired torque output as determined by the torque distribution unit.

2. Controller system according to claim 1, wherein the controller system is a closed-loop system, and wherein the controller system comprises a monitoring unit configured for receiving data indicative of one or more operational parameters of the switched reluctance machine.

3. Controller system according to claim 2, wherein the one or more operational parameters include at least one element of a group comprising: an actual phase current applied to one or more of the phase stages, an angular rotor position of the rotor relative to the stator, a rotation velocity of the rotor; or a DC voltage level available for said powering.

4. Controller system according to claim 2 or 3, wherein the controller system is further arranged for providing the correction unit with data indicative of the first position and the second position of the respective phase stage, wherein the first and second position are dependent on at least one of the one or more operational parameters.

5. Controller system according to claim 4, wherein the controller system includes or is communicatively connected to a data store, the data store including a lookup table for associating the at least one of the one or more operational parameters with one or more of the first and second position.

6. Controller system according to any of the preceding claims, wherein the torque distribution unit is configured for determining the desired torque outputs to be delivered by adjacent phase stages when the counter poles move from a first one of the adjacent phase stages to a second one of the adjacent phase stages, the torque distribution unit being configured for providing a first desired torque output for the first one of the adjacent phase stages and a second desired torque output for the second one of the adjacent phase stages; wherein the correction unit is configured for correcting at least one of the first or second desired torque output.

7. Controller system according to any one or more of the preceding claims, wherein the multiphase switched reluctance machine is at least one of a switched reluctance motor or a switched reluctance generator.

8. Correction unit for use in a controller system according to any of the preceding claims, the correction unit is configured for cooperating with a torque distribution unit for receiving a determined desired torque output for a phase stage, the correction unit comprising an input for receiving a current position data indicative of a current position of at least one counter pole relative to a stator pole of the phase stage, and wherein the correction unit is configured for correcting the determined desired torque output for the phase stage such as to provide a corrected desired torque output associated with said current position of the counter pole relative to the stator pole, for enabling building up said phase current through said phase stage for enabling the phase stage to effectively deliver the desired torque output as determined by the torque distribution unit.

9. Method of controlling operation of a multiphase switched reluctance machine, the multiphase switched reluctance machine comprising a stator including a plurality of coils and stator poles wherein the stator poles form the cores of the coils, and a rotor including a plurality of counter poles for interacting with the stator poles for applying a reluctance torque on the rotor, the rotor being rotatable relative to the stator, the coils being associated with a plurality of phase stages of the multiphase switched reluctance machine such that each coil of the stator is associated with one phase stage, each phase stage thereby being associated with one or more of the plurality of coils of the stator;

the method comprising the steps of:

powering, by a controller system, the phase stages by subsequently applying a phase current to each of the phase stages respectively such as to apply the reluctance torque to the rotor, wherein for each phase stage the phase current is applied by: switching on the phase current in a first position of a counter pole relative to a stator pole of said phase stage, and

determining for at least one phase stage of the phase stages, using a torque distribution unit, a desired torque output to be delivered by said at least one phase stage, and providing the determined desired torque output for the respective phase stage to a correction unit;

receiving, by the correction unit, the determined desired torque output for the respective phase stage and current position data indicative of a current position of the counter pole relative to the stator pole of the respective phase stage; and

correcting, by the correction unit, the determined desired torque output for the respective phase stage such as to provide a corrected desired torque output associated with said current position of the counter pole relative to the stator pole, for enabling building up said phase current through said respective phase stage for enabling the phase stage to effectively deliver the desired torque output as determined by the torque distribution unit.

10. Method according to claim 9, wherein the method further comprises:

receiving, using a torque estimator, operational data of the multiphase switched reluctance machine; and

calculating, by the torque estimator, an estimated range of achievable phase torque amounts for the at least one phase stage, for providing the estimated range to at least one of the torque distribution unit or the correction unit.

11. Method according to claim 10, where the multiphase switched reluctance machine is a switched reluctance motor, and

wherein dependent on the current position of the counter pole relative to a first stator pole of a first phase stage and relative to a second stator pole of a second phase stage adjacent to the first phase stage, where the second phase stage is one of the at least one phase stage for which the desired torque output is determined by the torque distribution unit, correcting of the determined desired torque output includes at least one or more of the following steps: when the current position is located between the first position and an unaligned position where the second stator pole is located in the middle of two consecutive counter poles of the rotor, and when an absolute value of a maximum phase torque amount of the range of achievable phase torque amounts is larger than or equal to an absolute value of a minimum phase torque amount of the range of achievable phase torque amounts, the determined desired torque output is set to the maximum phase torque amount; or

when the current position is located between the first position and an unaligned position where the second stator pole is located in the middle of two consecutive counter poles of the rotor, and when an absolute value of a maximum phase torque amount of the range of achievable phase torque amounts is smaller than an absolute value of a minimum phase torque amount of the range of achievable phase torque amounts, the determined desired torque output is set to the minimum phase torque amount.

12. Method according to claim 10, where the multiphase switched reluctance machine is a switched reluctance generator, and

wherein dependent on the current position of the counter pole relative to the stator pole of the at least one phase stage for which the desired torque output is determined by the torque distribution unit, correcting of the determined desired torque output includes at least one or more of the following steps:

when, in a direction of moving of the counter pole, the current position is located between the first position and an aligned position where the counter pole is aligned with the stator pole, and when an absolute value of a maximum phase torque amount of the range of achievable phase torque amounts is larger than or equal to an absolute value of a minimum phase torque amount of the range of achievable phase torque amounts, the determined desired torque output is set to the maximum phase torque amount; or

when the current position is located between the first position and an aligned position where the counter pole is aligned with the stator pole, and when an absolute value of a maximum phase torque amount of the range of achievable phase torque amounts is smaller than an absolute value of a minimum phase torque amount of the range of achievable phase torque amounts, the determined desired torque output is set to the minimum phase torque amount.

13. Method according to any one or more of the claims 9-12, wherein the method is a closed-loop control method, and wherein the method further comprises receiving, by a monitoring unit, data indicative of one or more operational parameters of the switched reluctance machine, wherein optionally the one or more operational parameters include at least one element of a group comprising: an actual phase current applied to one or more of the phase stages, an angular rotor position of the rotor relative to the stator, a rotation velocity of the rotor; or a DC voltage level available for said powering.

14. Method according to claim 13, wherein the method further includes providing the correction unit with data indicative of the first position and the second position of the respective phase stage, wherein the first and second position are dependent on at least one of the one or more operational parameters.

15. Method according to claim 14, wherein the step of providing the correction unit with data indicative of the first position and the second position of the at least one phase stage further comprises:

associating, using a data store including a lookup table, the at least one of the one or more operational parameters with one or more of the first and second position.