lllllllilllllilllilIllillllllllllllllllllllllllllllllllllllllllllllll
`
`USOD7208895B2
`
`(12)
`
`United States Patent
`Mareinkiewicz et al.
`
`(10; Patent No.:
`
`(45) Date of Patent:
`
`US 7,208,895 B2
`Apr. 24, 2007
`
`CONTROL SYSTEMS AND METHODS FOR
`PERYIANENT MAGNET ROTATING
`MACHINES
`
`(56)
`
`References Cited
`U.S. PA'l'l:'N'l' l)OCUMl:£N'l'S
`
`(54)
`
`(75)
`
`inventors: Joseph G. Maminkiewiez, St. Peters,
`MO (US); Prakash B. Shahi. St. Louis,
`MO (US); Michael [. Henderson,
`North Yorkshire (GB)
`
`(731
`
`Assignce:
`
`Emerson Electric Cn., St. Louis, MO
`(US)
`
`t“)
`
`Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`lI.S.C. 154(1)] by 0 days.
`
`(211
`
`App]. No: 11/293,743
`
`(22)
`
`Filed:
`
`Dec. 2, 2005
`
`(65)
`
`(60)
`
`(51)
`
`(52)
`
`(53)
`
`Prior Publication Data
`
`US 2006/0290304 A1
`
`Dec. 23. 2006
`
`Related U.S. Application Data
`
`l-‘rovisional application No. 60/694,077, filed on Jun.
`24, 2005. provisional application No. 60/694,066,
`filed on Jun. 24, 2005.
`
`Int. Cl.
`(2006.01)
`H02K 21/00
`U.S. (:1.
`.................... __ 3131254; 318f138_; 313/439;
`3lBi'70l
`318/754,
`Field of Classification Search
`318!138, 439, 701. 717, 723, 798, 815, 432,
`3131433; 33s;907.5, 902, 815
`See application file for complete search history.
`
`5.759.893 A "'
`6,586,904 B2‘
`200590253540 Al‘
`
`$1993 Watkins
`7:17.003 McClella.nd et al.
`1132005 Kcbayashi et al.
`
`3181701
`318/701
`.
`
`....... .. 318E254
`
`* cited by examiner
`
`Primary Examim.>r—Karcn Masih
`
`(74) Attorney, Agent, or Fz'rm—Harness, Dickey & Pierce,
`P.l....C.
`
`(57)
`
`ABSTRACT
`
`Systems and methods for controlling a rotating electromag-
`netic machine. The rotating machine. such as a permanent
`magnet motor or hybrid switched reluctance motor. includes
`a stator having a plurality of phase windings and a rotor that
`rotatcs relative to the slato1'.A drive is connected to the phase
`windings for energizing the windings. A controller outputs a
`control signal to the drive in response to inputs ofdemanded
`torque, rotor position and/or speed. Control methods include
`calculating a scaled torque demand from the roccived torque
`demand to obtain substantially constant torque over a range
`of motor speeds, calculating an optimal dr-axis injection
`current using a cost function and a starting method that
`switches from speed control mode to torque control mode at
`a predetermined rotor speed or at predetermined start-up
`timing intervals.
`
`23 Claims, 8 Drawing Sheets
`
`Efilimnlud electrical angle
`«T1:
`
`Measured current and
`Appiied vutlagu
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`BOM Exhibit 1042
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`BOM Exhibit 1042
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`IPR2014-01121
`
`1
`
`

`
`U.S. Patent
`
`Apr. 24, 2007
`
`Sheetl of8
`
`US 7,208,895 B2
`
`199.
`
`102
`
`104
`
`
`
` Controller
`Torque
`Demand
`
`/ PM Motor
`
`Rotor Positionlspeed
`
`101
`
`FIG. 1
`
`2
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`U.S. Patent
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`Apr. 24,2007
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`U.S. Patent
`
`Apr. 24, 2007
`
`Sheet 5 of 3
`
`US 7,208,895 B2
`
`E0.
`
`§
`
`502
`
`Run command
`
`Start Open Loop
`Using Predeterrnined
`Speed Value
`
`Actual Speed
`>= Predefined
`
`Value?
`
`Run Closed Loop
`Using Demanded Torque
`
`FIG. 5
`
`Improved Open Loop Starting
`
`6
`
`

`
`U.S. Patent
`
`Apr. 24, 2007
`
`Sheet 6 of8
`
`US 7,208,895 B2
`
`Run command
`
`Start Open Loop WI-tz
`Run Estimator with
`
`Demanded Hz
`
`After 2 sec
`
`Transition to psuedo-closed loop mode
`— run Estimator with demanded Hz
`
`- run speed control mode
`
`Afte-r1 sec
`
`§_0.9.
`
`602
`
`4
`
`60
`
`606
`
`Transition to true sensorless
`
`— run estimator with filtered calouiated speed
`
`- transition to torque control mode
`
`608
`
`
`
`is estimator speed
`within range?
`
`
`Yes
`
`610
`
`No
`
`512
`
`Shutdown and restart
`
`Run Demanded
`Torque
`
`Lost Rotor detected
`
`FIG. 6
`
`7
`
`

`
`U. S. Patent
`
`Apr. 24, 2007
`
`Sheet 7 of 3
`
`US 7,208,895 B2
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`U.S. Patent
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`Apr. 24, 2007
`
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`US 7,208,895 B2
`
`1
`CONTROL SYSTEMS AND METHODS FOR
`PERMANENT MAGNET ROTATING
`MACHINES
`
`CROSS-REFERENCE TO RF.I.A'l'F,l)
`APPLICATIONS
`
`This application claims the benefit of U.S. Provisionai
`Applications No. 60r‘694,077 and No. 601694.066 filed Jun.
`24. 2005, the entire disclosures of which are incor'po1"ated
`herein by reference.
`
`FIELD OF THE INVENTION
`
`invention relates generally to control of
`The present
`rotating machines, including but not limited to torque con-
`trol of permanent magnet rotating machines.
`
`BACKGROUND OF THE INVENTION
`
`Various control systems and methods are known in the art
`for controlling the output
`torque of permanent magnet
`machines, such as brushless permanent magnet motors.
`Some of these machines are provided with position sensing
`devices to indicate, for motor control purposes, the rotor
`position with respect to the stator, while other machines
`detect the rotor position “sensorlessly.” As reeognizred by the
`present inventors. a need exists for improvements in sensor-
`based and sensorless control systems for rotating pennanent
`magnet machines, including those which control the output
`torque of a PM motor.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. I is a block diagram of a rotating permanent magnet
`machine system according to one embodiment of the present
`invention.
`
`10
`
`I5
`
`25
`
`30
`
`35
`
`FIG. 2 is a block diagram of a sensorlcss implementation
`of the system of FIG. 1 according to another embodiment of
`the invention.
`
`-1-0
`
`FIG. 3 is a block diagram ofan exemplary embodiment of
`the torque scaler shown in FIG. 2.
`FIG. 4 is abloclc diagram ofan exemplary embodiment of
`the ldr Injection block. the Torque to IQdr Map block and
`the vectorize block of FIG. 2.
`
`FIG. 5 is a [low diagram ofan open loop starting method
`according to another embodiment of the present invention.
`FIG. 6 is a flow diagram ofan alternative start-up method
`according to another embodiment of the invention.
`FIG. 7 is a graph illustrating how the optimized calculated
`value of ld.r injection mirrent varies with electrical speed.
`FIG. 8 is a graph validating the proposed solution for the
`optimized calculation of ldr.
`
`DETAILED DESCRIPTION OF EXEMPLARY
`EMBODIMENTS
`
`Illustrative embodiments of the invention are described
`below. In the interest ofclarity, not all features ofan actual
`implementation are described in this specification. It will be
`appreciated that in the development of any actual embodi-
`ment. numerous implementation-specific decisions must be
`made to achieve specific goals, such as performance objec-
`tives and compliance with system-related, business-related
`and/or environmental constraints. Moreover.
`it will be
`appreciated that such development efforts may be complex
`
`45
`
`50
`
`60
`
`65
`
`2
`and time-consuming, but would nevertheless be a routine
`undertaking for those of ordinary skill in the art having the
`benefit of this disclosure.
`FIG. 1 illustrates a rotating permanent magnet machine
`system 100 in accordance with one embodiment of the
`present invention. The machine system includes a rotating
`permanent magnet electric machine 101, such as a pem1a-
`nent magnet alternating current (PMAC ] motor or a perma-
`nent magnetfswitched reluctance (PM.-’SR} motor (i.e.. a
`hybrid PM machine). For simplicity. the term "motor” is
`ofien used in this specification. However. one skilled in the
`art having the benefit of this disclosure will understand that
`the present invention is applicable to other types of rotating
`electric machines, including generators. The PM machine
`101 shown in FIG.
`1
`includes a stationary component
`(stator) 102 and a rotating component (rotor) 104. The
`machine can have an inner rotor or an outer rotor construc-
`tion. In this exemplary embodiment, the PM machine 101 is
`a three phase machine having an inner rotor construction
`with energimble phase windings 106A, 106B, 106C wound
`about the stator which is energized through the application
`of electric power to the motor terminals.
`A drive 108 is coupled to provide electric power to the
`terminals of the machine. The drive 108 receives control
`inputs from a controller 110 that receives rotor position and
`rotor speed data 112 from one or more sensors coupled to the
`machine. or energization feedback from the machine (such
`as the currents and/or voltages at the motor terminals) from
`which the rotor position and rotor speed can be determined
`(i.e., sensorlessly}. As an alternative to sensing voltages at
`the motor terminals. the controller can assume the actual
`voltage supplied to the motor is that which was demanded.
`Sensorless control systems and methods suitable for use
`with the present invention are described in co-pending US.
`Application Ser. No.
`ll."293,'i'44, titled Sensorless Control
`Systems and Methods for Permanent Magnet Rotating
`Machines, filed [on even date herewith]. the entire disclo-
`sure of which is incorporated herein by reference.
`The controller 110 of FIG. 1 is configured to operate
`primarily in a torque control mode, and is therefore shown
`as receiving a torque demand 114 input.
`it should he
`understood, however.
`that certain aspects of the present
`invention apply to other modes of operation, including speed
`control modes, and are therefore not
`limited to torque
`control systems.
`With further reference to FIG. 1, the torque demand 114
`input may be received directly by the system as an cxtcmal
`command or alternatively, may be derived from an external
`command. For example, the torque demand input may be
`derived from a speed demand i.r1put or from an air {low
`demand input [e.g._. where the system of FIG. 1 is embodied
`in an air handler/blower for a climate control system).
`While the drive of FIG. 1 is illustrated in exemplary form
`as energizing three power
`temiinals of a
`three phase
`machine. it should be understood that more or fewer power
`terminals may he provided to accommodate machines with
`greater or less than three phases, or if various types of
`inverters (e.g., with neutral connections) are used. The drive
`may be of conventional design and configured to provide,
`e.g., sine wave excitation to the motor terminals or square
`wave excitation using pulse width modulation (PWM) exci-
`tation.
`
`FIG. 2 illustrates additional details of the system [and
`primarily the controller) of FIG. 1. As shown in FIG. 2. the
`input torque demand 114 is provided to a torque sealer 202
`(described further below with reference to FIG. 3) that
`produces a scaled torque demand 204. The scaled torque
`
`10
`
`10
`
`

`
`US 7,208,895 B2
`
`15
`
`25
`
`3
`demand is provided to 3 Torque to IQdr Map block 206 that
`calculates an lQr demand 208 using motor-specific torque-
`to-]Qr map data. 'IIie IQr demand is then concatenated with
`an Idr demand from an Idr Injection block 210 (described
`further below) into a vector quantity IQdr demand 214 by 5
`the vectorize block 212. AS shown in FIG. 2, the value ofthe
`Idr demand 209 (i.e., dr—axis injection current} is calculated
`using tl1e value of the DC link voltage, vdc, and the
`estimated electrical speed 216 received from a llux estimator
`228 (e.g., as described In U.S. Pat. No. 6.756.753). The 10
`resulting IQdr demand takes into account the torque contri-
`bution,
`if any, of the dr-aids current
`(c.g.. as may be
`encountered in hybrid PM/SR motors).
`With fitrther reference to FIG. 2, the lQdr demand 214
`l'rom the vectorize block 212 is input
`to an lQr Current
`Controller 218 and an Idr Current Controller 220. These
`contr-ollers convert
`the vector of motor currents in the
`electrical frame of reference to a vector of motor voltages in
`the electrical frame of reference. The vector of motor
`voltages is then transformed to alpha-beta-zero voltages 222 20
`and provided to the drive 108. The drive converts the
`rotating alpha-beta-zero voltages to three ABC stationary
`reference frame voltages 226 that are applied to the motor
`terminals to produce the demanded torque (e.g., a constant
`torque) output.
`The fiux estimator block 228 of FIG. 2 produces the
`estimated electrical speed 216, as noted above, which is also
`provided to an input filter block 230 for smoothing the
`estimated electrical speed. The output of the input filter
`block 230 is provided to a speed clamp 232 (which defines 30
`minimum speed limits for stability purposes) to produce a
`filtered speed demand. The filtered speed demand 234 is
`provided to an integrator 236, which produces a drive angle
`command 238 for the lluic estimator 228, and to a gain
`scheduler 240 (details of which are disclosed in the 00- 35
`pending application noted above) which selects or calculates
`a gain factor as a function of the filtered speed demand and
`provides this gain factor to the flux estimator 228. The use
`of a filtered speed demand to develop the drive angle
`command 238 to the flux estimator 228 improves the torque 4o
`stability of the machine. Using the gain factor from the gain
`scheduler 240, the drive angle command 238, and energi-
`zation feedback 242 from the PM machine, the flux estima-
`tor 228 calculates an estimated electrical angle 244 (which
`is provided to a vector controller which uses the estimated 45
`angle to execute transforms) and an estimated electrical
`speed 216.
`At start-up, when the rotor speed is zero. the controller of
`FIG. 2 operates in an open loop speed control mode using a
`prcdetcrrnined speed value (which takes into account char- 50
`acteristics of the PM machine). The controller operates in
`this open loop speed control mode until the rotor speed
`reaches a predefined threshold value (which may also be
`specific to the given PM machine), and then switches to a
`closed loop torque control mode of operation using the input 55
`torque dentand. This is further illustrated by the how dia-
`gram 500 of FIG. 5, where upon receipt of a run command.
`the PM machine system starts, at step 502,
`in open loop
`using a predefined speed value. As the actual speed is
`sampled by the system,
`it
`is compared in step 504 to a 60
`predefined value. If the actual speed is greater than the
`predefined value. the system switches. in step 506, to closed
`loop operation using the demanded torque. If the actual
`speed is below the predefined threshold. the system contin-
`ues open loop operation in step 502.
`An alternative start-up operation is illustrated by the flow
`diagram 600 of FIG. ti. As shown in step 602, the controller
`
`65
`
`4
`operates at start-up in an open loop mode using a demanded
`speed value. After a predetermined amount of time. e.g.. two
`seconds. the controller transitions to a pseudo-closed loop
`speed control mode in step 604. After a further predeter-
`mined amount of time,
`t:.g., one second,
`the controller
`transitions to a sensorless control mode in step 606, e.g., a
`torque control mode, and runs an estimator (such as the
`estimator 228 shown in FIG. 2) at a scheduled gain cone-
`sponding to the filtered estimated speed 234. In step 608. the
`controller determines Whether the estimated electrical speed
`produced by the estimator is wit.hin range. If so. the con-
`troller runs a demanded torque in step I510. Otherwise, the
`controller will shutdown the system and attempt a restart as
`indicated in step 612.
`FIG. 3 illustrates an exemplary embodiment 300 of the
`torque sealer block shown in FIG. 2. In this embodiment. the
`torque sealer 300 produces the scaled torque demand from
`input Values of the rotor estimated speed 302. the torque
`demand 304, a torque multiplier 306, and a torque offset
`308. The torque multiplier 306 and the torque offset value
`308 are preferably motor-specific parameters which com-
`pensate for individual motor characteristics. The toque
`offset 308 is preferably the niinimum torque value required
`to run the motor without a load (also referred to as free shaft
`operation) As shown in FIG. 3, the rotor speed is converted
`to a corresponding speed ofisct by a speed-torque depen-
`dence block 310 which may be. e.g., a look-up table con-
`taining specd-torquc table values for the particular motor
`being controlled.
`In this embodiment of the torque scaler, the scaled torque
`demand 312 is calculated as the sum of three components:
`Speed olliseh-(Tr:-rque rtemartd]*iTot'qLIe n'tul.tl.plit:rl+
`Torque. offset.
`
`A typical torque versus motor speed operating curve of a PM
`motor or hybrid PM./SR motor exhibits a negative slope at
`higher operating speeds after attaining a maximum torque.
`To achieve a constant motor torque output with increasing
`motor speed, the value of [he demanded torque is increased
`(i.e., compensated) by the control system as the motor
`operating speed increases, thereby making the torque lines
`flatter with speed. Motor-specific correction factors vary the
`torque gain factor as a function of IQr current and speed to
`achieve a substantially constant torque over the operating
`speed range of the motor. In some embodiments, estimated
`speed is used as the speed variable in the torque sealer.
`With further reference to FIG. 2, the Idr injection block
`210 ensures that optimal use of the DC link voltage is made
`in order to achieve the desired IQr current demand 208. This
`is achieved by defining an optimization problem using
`several costs. These costs may include terms such as:
`required voltage to support the demanded Qr and dr axis
`currents: a bulk current
`term; and power consumption.
`Solving this optimization problem for particular operation
`conditions, such as motor speed and the value of the dc-link,
`yields a desired value of ctr-axis current. In the context of the
`present discussion, the term phase advance is understood to
`be the action ofsetting this current value as a demand for the
`dr-axis current controller. As disclosed in the copending
`application referellced above, the value of IQ!‘ demand 208
`current is compensated for the torque contribution of the Idr
`injection current using motor-specific perfonnance Charac-
`teristics.
`
`FIG. 4 shows an exemplary embodiment of the Idr
`Injection block 210, the Torque to lQdr Map block 206, and
`the vectorize block 212 ofFIG. 2. In the embodiment ofFIG.
`
`11
`
`11
`
`

`
`US 7,208,895 B2
`
`5
`injection) is
`the dr-axis current
`the ldr demand [i.c..
`4,
`calculated from a look-up cable 402 (specific to the PM
`motor) that considers vdc 404. and the product ofthe current
`value Id and estimated speed 406. The calculated value of
`Idr demand 408 is provided to a vectorize block 412. as well
`as to an ldr compensation gain for ldr within the Torque to
`lQdr Map block 206. Although the Id.r injection current in
`this embodiment is determined solely as a function of vdc,
`lQr. and rotor speed. the ld.r injection current can alterna-
`tively be determined using a cost function having compo-
`nents relating to bulk current costs, power consumption
`andlor torque,
`in addition to or in lieu of components
`relating to vdc, lQr and rotor speed.
`Additional details of the method for calculating the
`amount of ldr injection current provided to the Torque to
`lQdI Map 206 and the vectorize 212 blocks in PK}. 2 will
`now be described. For machines controlled via a speed loop
`controller, the speed error is converted to a demanded torque
`114 by the speed loop controller and thc demanded torque
`114 is provided as an input to the Torque to lQdr Map block
`206. Thus, ldr injection current can be applied within either
`a speed controlled or torque controlled machine. ldr injec-
`tion cument, also described in the art as a phase advance
`current, may contribute 20% or more of the torque of a
`hybrid PM rnachine. when this torque component is present,
`the control system preferably compensates (i.e., adjusts) the
`magnitude of the lQr demand current to achieve the desired
`torque output.
`The general approach is to optimize the value of ldr
`demand using a cost function. The cost function incorporates
`values associated with utilization of the DC link; bulk
`current terms; power and torque. The goal of the optimiza-
`tion problem is to calculate the amount of injection currcnt
`necessary so that the total voltage required to drive the
`demanded currents does not exceed that available from the
`invener (i.e.. vdc].
`To optimize the value of ldr injection current, the appro-
`priate cost components are defined for use in the cost
`equation. With the cost expression defined, the closed form
`solution for the value of ldr becomes one of di lferentiating
`the cost expression with respect to ldr-current, setting the
`result equal to zero and solving for the roots (i.e., solutions)
`of the resulting equation {’i.e., a typical tnaxima/minirna
`calculus problem).
`The equation used for optimization can be derived in the
`following manner:
`I. Define cost component associated with volts;
`2. Define one or more secondary cost functions, associ-
`ated with power or bulk cunent;
`3. include a cost function assticialed with torque demand.
`particularly when dealing with a hybrid motor: and
`4. Optimize with respect to ldr current.
`The cost function associated with voltage is the nominal
`DC link value needed to support the ordered pair of Qr and
`dr currents. This is the primary component of the cost
`function. Secondary cost terms may include bulk current
`terms, indicative of cllicicncy, or torque or power consump-
`tron.
`
`6
`a way that may be more appropriate for a given PM machine.
`In others embodiments. greater emphasis may be placed on
`eificiency.
`The fundamental electriced equation in the electrical
`5 Frame of Reference is:
`
`ID
`
`vQ,,,=R-r,,,.+
`
`ulftu,
`ti
`0
`
`.
`,,
`+l.!.+M1-(E.rm,J+ro,.-(L+Ml—G—tQ,,,
`
`(ll
`
`Writing the single vector equation as two coupled scalar
`equations:
`
`(1
`P9,. = R-}Q,+.tJrm,.+(.L+ M)- E19, +1»,-('L+ M’)-Id,
`d
`V4,: tr-1,, +(.L+M)-E!“-,—w,-LL+M]-IQ,
`
`'1}
`
`I‘
`(3)
`
`Then, the condition so that the required voltages in the
`Qdr frames of reference do not exceed that which can be
`provided by the dc-link is given by‘.
`
`11,3.-R+2.,m. +w,-(L+ Mi-t.,,11 +tR~Id,.~tu.-(L+ M)- r;,,F s
`1
`2
`-_§'KpwnuI"5c
`
`:41!
`
`An exemplary voltage cost function becomes:
`
`[rQ,- R+.t,r.., +o,-(r.+ :m- r,.,]’ +
`is i r,.,- 5.), -(r.+ .14}. 1%.}:
`2
`"I
`§ 'l-'i'pm,4V3¢t‘
`
`- Km
`
`(5)
`
`lhis is the central component of the optimization cost
`function.
`
`in
`Torque can be used as part of the cost function.
`particular to drive the proposed solution such that a torque
`demand cart he met. The torque cost component can be
`expressed in a normalized form as:
`
`kyvzque
`
`(67
`
`15
`
`30
`
`35
`
`40
`
`45
`
`St]
`
`55
`
`Such an expression is normalized against maximal torque
`demand 'l‘,,,,,,, and scaled according to a defined weighting
`kFOFGMQ '
`
`ln each cost componetlt term, the standard approach is to
`normalize each individual teI1'n with respect to some nomi-
`nal maximal value (e.g., IQI. ldr, power). This produces a
`typical range of [-1.1] for the cost. A weighting index can
`also be applied to each term that allows for a certain degree
`of fine tuning.
`The central component of any defined cost function is the
`term defining the required voltage. The presence of second-
`ary cost components can he used to condition the solution in
`
`I50
`
`I55
`
`When the motor under consideration is a hybrid motor, the
`presence ofdr-axis current itself generates more torque. In
`such applications, less lQ,.—aitis current is needed and corre-
`spondingly less vdc voltage. In one exemplary embodiment,
`the expression for the torque related cost function is:
`
`t(u.37s4-1Q.—o.oo93-rQ,»s')— rm]?
`
`(7)
`
`Such an expression as that presented in Equation (7)
`above replaces Equation (6) in the aggregate cost function.
`A good indicator of efliciency is the bulk current term, or
`sum of the squares ofcurrent. Many of the loss mechanisms
`
`12
`
`12
`
`

`
`US 7,203,895 B2
`
`7
`present in a motor manifest themselves through expressions
`involving squared current terms. Hence, an appropriate bulk
`current cost term. riomlalized to Imx, is given by:
`
`rgd, - I95,
`1'...“
`
`"um
`
`18)
`
`where the 1,”, is the sum of squares of the maximal values
`of current expected in both axes.
`A variant upon the concept of bulk current as a component
`of the cost function is to use a cost function based upon
`m:2.1"
`power consumptiom again nonnalized to P
`'
`
`ItDown‘
`
`v§i_.(c_,,,,.‘
`‘Fin.-ax
`
`(9)
`
`Atypical cost fiinction is then expressed as the sum of the
`three cost components:
`voltage_cost cornponent+bulkAcn:rcnt_cost_cornpo-
`nent+requitcd_torque_cost _mrnponeuI
`
`This optimization problem can be solved by taking a
`derivative with respect to the variable sought to be mini-
`miaved. In one exemplary embodiment, the variable is the
`Idr-axis current.
`then becomes
`it
`With a proposed solution available.
`necessary to substitute hack into the original electrical
`equation the calculated optimized value tor Idr and deter-
`mine the margin between required voltage to drive the
`desired current and the value of Vdc. If such margin exists,
`then the proposed solution is use Ful. This checking process
`is illustrated in the example below.
`Fquation It) is one embodiment ofa cost function, A,
`where A includes the motor-specific cost components for
`voltage, bulk current and torque:
`
`5
`
`10
`
`15
`
`20
`
`la LA
`
`30
`
`35
`
`8
`K,,dL_=voltage weighting function, K_.M.,,=bulk current
`weighting
`KmM=torqne weighting function
`Wcightillg coefiicients are used with respect to the vdc
`usage as well as an aggregate IQ, current term. The minimum
`of the exemplary cost function in Equation 10 occurs for
`some value of dr-axis current such that:
`
`d ,
`E’;I,Ali'Q,.. ru,, side) = O)
`
`(11)
`
`The graph 700 of FIG. 7 illustrates how the magnitude of
`tile injection current varies with motor electrical speed and
`vdc for various weighting values (702,704.706_.708) of K_,,,,_.,
`Kpwm and Kwwe. This exemplary embodiment uses esti-
`mated electrical speed 2]6 i11 its calculation of Idr injection
`current.
`
`Note that in both motoring, and generating mode, the Sign
`of the Idr current is chosen as negative. Should it ever
`become positive then there arises the possibility that the
`motor could act as a good generator. a situation which may
`not be desirable unless actually required.
`Having arrived at an optimized solution tor injection
`current, it is desirable to check its validity. This can be done
`by substituting the value for ldr injection current into the
`electrical equation and checking that the dc link value is
`suflicient.
`
`.'Q,: = 19,
`
`[19,-R + A,-cu, + to, - (L + M 1 - I,,,(<a,., vdc)]2 +
`
`.
`2
`.
`4
`[R-Id,—w,-(L+ M]-Ia-,\nJ,. v,.c‘i]‘ = 3-Kdvgc
`
`Align Ln-~ iv‘:-a Vac. K;wmd- Knit». Km. Kmngmli =
`
`(103
`
`[Ip,.-R+,1_;.:u,+n2,-(L+M)-Ic,-r]:+
`pm —
`-'r_+.m-r
`‘
`Ii’ w’\
`
`W]
`
`-K“.,,,...+
`
`In such a test one may choose to deliberately round motor
`parameters and other variables or states associated with the
`problem so as to investigate the typical worst case scenario.
`The difference or residue between what voltage is needed
`and that which the DC 1in.l~: ofiers is given by:
`
`45
`
`_
`(:3, + 1:7,) — KM [m..17s3rQ, — 0.009311%; -712
`+ ~ve——-——r— - A
`‘mm.
`TI:-r.-rl
`
`mu
`
`.
`
`K,,m.,‘, Km, and Kmrwe are weighting eoeflieients for the
`bulk current, voltage and torque cost components, respec-
`tively.
`The exemplary cost function in Equation 10 includes the
`following motor variables:
`L=se1f inductance. M=rnutual inductance, Rzresistance
`
`lQ,=Qr axis current, l,,,:dr axis current
`1.1‘-BEMF. tu,.=electr-ical speed
`When Lhe Inaximuin current of each axes current is 18
`amperes:
`
`I,,,,,,,,:=l8’+183
`
`Define weighting coellicienls associated with the optimi-
`zation process:
`\v'd(=(1C-li.[1li value, Kpw,,,=l’WM duty cycle. typically 0.85
`to 0.95
`
`55
`
`til)
`
`65
`
`nexus. r..«.. we Var): = no R + no - (L + M1-tn? +
`[K'-fdr — cu,-tL+ M149.-l2 —
`1:
`
`2 V2
`3
`a1
`
`(121
`
`w,.: : ru,
`
`19,-! = IQ,
`D45: = Dd‘.
`
`The graph 300 ofFlG. 8 illustrates the value of the voltage
`residual with motor electrical speed about zero speed for two
`sets of values 802, 804 of IQ, and vdc (18 amps, 340 volts)
`and (22 amps. 300 volts) for unity values of Kvdc, KPW and
`KIM”. This plot indicates that the proposed solution is
`successful, even though one of the validation plots 802 fails
`at the extreme speed range when more than the specified
`current is used and there is a drop in bus voltage. Plot 8134
`
`13
`
`13
`
`

`
`Us 7,208,895 B2
`
`10
`11. The climate control system of claim 10 wherein the
`system includes an air handler and wherein the air handler
`includes said assembly.
`12. A method of controlling a permanent magnet rotating
`machine, the machine including a stator and a rotor situated
`to rotate relative to the stator, the stator having a plurality of
`energizable phase windings situated therein,
`the method
`comprising:
`calculating an lQr dim-rand from a speed or torque
`demand;
`calculating a dr-axis injection current demand as a func-
`tion of a speed of the rotor; and
`combining the ]Qr demand and the dr-axis injection
`current demand to produce an lQdr demand that
`is
`compensated tor any torque contribution cl‘ dr-axis-
`current.
`
`13. The method of claim 12 wherein calculating includes
`calculating the dr-axis injection current demand filrther as a
`function ofa maximum voltage available tor energizing the
`machine.
`14. The method of claim 12 wherein calculating includes
`calculating the tlr-axis injection current demand as a func-
`tion of estimated speed of the rotor, at q—nxis current. and a
`maximum voltage available for energizing the niachine.
`15. The method of claim 12 wherein calculating includes
`calculating the dr-axis injection current demand using a cost
`fimction.
`
`16. The method of claim 12 further comprising assuming
`a maximum value of a Qr-axis current.
`17. The method of claim 12 wherein calculating includes
`defining a cost function having one or more cost components
`associated with volts, power consumption, and-‘or hulk cur-
`rent, and optimizing with respect to the dr—axis injection
`current.
`
`18. The method of claim 17 wherein optimizing includes
`dillercntating the cost function with respect to the dr-axis
`injection current.
`19. The method of claim 12 further comprising determin-
`ing the speed of the rotor with or without sensors.
`20. The method of claim 12 further comprising operating
`the machine in a torque control mode or a speed control
`mode.
`
`9
`illustrates that the proposed solution is successfill through-
`out the expected speed of operation.
`The description of the invention above is merely exem-
`plary in nature and, thus, variations that do not depart from
`the gist of the invention are intended to be within the scope
`of the invention. Such variations are not to be regarded as a
`departure from the spirit and scope of the invention.
`What is claimed is:
`1. A method of controlling a permanent magnet rotating
`machine, the machine including a stator and a rotor situated
`to rotate relative to the stator. the stator having a plurality of
`encrgizablc phase windings situated therein.
`the mctl1od
`comprising:
`receiving a rotor torque demand; and
`calculating a scaled torque demand from the received
`torque demand as a filnction of a speed of me machine
`to obtain a substantially constant rotor torque over a
`range of rotor speeds.
`2. The method of claim 1 wherein said speed is an
`estimated speed of the machine.
`3. The method of claim 2 wherein calculating further
`includes calculating the scaled torque demand as a function
`of a torque olfset value.
`4. The method of claim 1 wherein calculating includes
`calculating the scaled torque demand as a function of a speed
`offset value.
`5. The method of claim 1 wherein calculating includes
`calculating the scaled torque demand as a Function of a
`torque olfset value.
`6. A method of controlling a permanent magnet rotating
`machine, the machine including a stator and a rotor situated
`to rotate relative to the stator. the