GB2440559A - Voltage source inverter output voltage error compensation - Google Patents

Voltage source inverter output voltage error compensation Download PDF

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Publication number
GB2440559A
GB2440559A GB0619440A GB0619440A GB2440559A GB 2440559 A GB2440559 A GB 2440559A GB 0619440 A GB0619440 A GB 0619440A GB 0619440 A GB0619440 A GB 0619440A GB 2440559 A GB2440559 A GB 2440559A
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United Kingdom
Prior art keywords
voltage
output
inverter
pwm
error
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Granted
Application number
GB0619440A
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GB0619440D0 (en
GB2440559B (en
Inventor
Robert Carter
Richard Kenney
Kenneth Thompson
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Siemens PLC
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Siemens PLC
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Publication of GB0619440D0 publication Critical patent/GB0619440D0/en
Publication of GB2440559A publication Critical patent/GB2440559A/en
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Publication of GB2440559B publication Critical patent/GB2440559B/en
Expired - Fee Related legal-status Critical Current
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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/505—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means
    • H02M7/515—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only
    • H02M7/525—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only with automatic control of output waveform or frequency
    • H02M7/527—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only with automatic control of output waveform or frequency by pulse width modulation
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P23/00—Arrangements or methods for the control of AC motors characterised by a control method other than vector control
    • H02P23/03—Arrangements or methods for the control of AC motors characterised by a control method other than vector control specially adapted for very low speeds
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P27/00—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage
    • H02P27/04—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage
    • H02P27/06—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters
    • H02P27/08—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters with pulse width modulation
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/38—Means for preventing simultaneous conduction of switches
    • H02M1/385—Means for preventing simultaneous conduction of switches with means for correcting output voltage deviations introduced by the dead time

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Inverter Devices (AREA)

Abstract

An electrical device such as a motor is controlled by means of a pulse width modulator (PWM) inverter. Errors in output voltage due to switching dead time and conduction losses are compensated by measuring the inverter voltage output over a full pulse period; comparing it with a demand voltage to determine an error and applying compensation to the voltage output of the inverter dependent on said error. Compensation may be applied to the inverter by lengthening or shortening the periods of the voltage pulse from the inverter. The output may be integrated over, and synchronised with, one or more PWM periods. The output may be measured using a counter, a DC link voltage and sigma delta analogue to digital conversion. The demand voltage may similarly be determined by counting the logic level of the PWM output stage, over the same time period as the output voltage is measured.

Description

<p>Voltage Source Inverter Output Voltage Error Compensation This
invention relates to an improved control of electric drives which use Pulse Width Modulation (PWM).</p>
<p>Where PWM is used to control a drive such as an electric motor, such arrangements typically include an inverter. The output from a pulse-width modulated voltage source inverter is subject to errors due to component voltage conduction loss and uncontrolled voltage during dead time' (time when both switches on a phase are in the off state to guard against DC link short circuits) and switching transients. Large drives operating at low motor frequencies typically need good control of very low output voltage levels.</p>
<p>This is therefore difficult to achieve. The conversion from a numerical voltage demand to a logic level PWM control signal is (relatively) error free -it's when that logic signal is amplified by a power stack to produce the output PWM that the errors come in. The counter is looking at (counting) the logic level PWM control signal for it's "set-point".</p>
<p>Previously the problem has been solved by predictive software control algorithms and other hardware based error prediction schemes (e.g. as a function of phase current). These solutions have significant problems.</p>
<p>It is an object of the invention to overcome the problems and provide accurate output voltage control at low output voltage in the presence of high dead time or high switching frequency enables high quality open loop motor control of large motors at low speeds.</p>
<p>The invention comprises a method of controlling an electrical device by means of a pulse width modulator inverter connected to said device including the steps of: measuring the voltage output over a full pulse period; determining the demand voltage; determining the error, and applying compensation to the voltage output of the inverter dependent on said error.</p>
<p>The voltage output is the output from the inverter or the voltage at the device terminals.</p>
<p>Preferably an integrating system and compensation comprises lengthening or shortening the periods of the voltage pulse from the inverter.</p>
<p>According to an embodiment of the invention, the inverter output voltage at the motor terminals is measured during a full PWM period: the voltage error compared with the "demand" voltage can be computed and used to compensate the next PWM period. The demand voltage is the control input from the controller of the drive. If, for example, the controller asks for 47V (averaged over time) but the feedback indicates the drive is outputting 44V (averaged over time) then the system knows there is a 3V error & the 47V requested will be increased in the next cycle to 50V in the expectation of getting the 47V actually wanted.</p>
<p>The output voltage measurement preferably uses an integrating measurement system, e.g. dual slope integrating or delta sigma, to properly detennine dead-time errors.</p>
<p>The integration time is synchronjsed to the PWM period; that is to say the integration time must be one or more full PWM periods as current dependent dead-time errors are different in the positive and negative going output voltage PWM transitions.</p>
<p>Figure 1 shows a schematic circuit diagram of the PWM and where the error compensation is applied.</p>
<p>The inverter is controlled by a voltage vector demand; this is the voltage that should (under ideal Circumstances) appear on the motor terminals but does not due to errors.</p>
<p>In the invention and in the embodiment of the figures; by separately measuring the voltage on the motor terminals (time averaged over a flit I period) we can subtract this from the demand voltage (again averaged) to give us the error.</p>
<p>Normally the controller simply expects the power module to deliver the voltage it asks for via a combination of the switching duty cycle and the measured DC link voltage.</p>
<p>The error compensation is applied by widening or narrowing the subsequent PWM pulses i.e. by delaying either the rising or falling edges. The output voltage is measured over n PWM pulses (where n is an integer). Thus an "integrating" voltage measurement is required -these are simple and cheap to construct as "delta sigma" ADCs.</p>
<p>As an alternative embodiment to using the demand voltage vector, a counter on the PWM voltage output is included. Figure 3 shows the pulsed waveform that is output from the PWM inverter on a terminal line.</p>
<p>The voltage is positive for a portion of the period and zero for the remainder of the period. The counter simply counts at fine intervals (represented by the up strokes) to determine the (portion) of time at the output voltage. This as well as the measured DC link voltage can be used to determine effectively the i'MW output voltage from the inverter. The counter is looking at (counting) the logic level PWM control signal for it's "selpoint".</p>
<p>Feedback is thus provided by the PWM inverter output. This again is preferably measured with the sigma delta ADC. This ADC reading, divided by the DC link voltage, gives a feedback signal which again is scaled to time. The count is performed over the same time period (integration time) as the output is measured, in the same way as the logic level PWM control signal count' is scaled to time (and the correction must be scaled to time) -so it's all rather convenient. Counting the duration of an internal logic signal is a cheaper, easier and less bug-prone operation than wading through the sums necessary to use the demand voltage prior to pulsewidtli modulation.</p>
<p>The advantage of this embodiment is that it is the (time averaged) voltage directly on the output of the PWM inverter is determined i.e. that before any it gets messed about with doing dead times, minimum pulse-widths etc. Thus compound braking can be supported and also the error is already scaled exactly as a correction time to go into the compensator.</p>

Claims (1)

  1. <p>Claims 1. A method of controlling an electrical device by means of a
    pulse width modulator inverter connected to said device including the steps of: a) measuring the voltage output over a full pulse period; b) determining the demand voltage; c) from steps a) and b) determining the error, and, d) applying compensation to the voltage output of the inverter dependent on said error.</p>
    <p>2. A method as claimed in claim 1 wherein said voltage output in step a) is the output from the inverter.</p>
    <p>3. A method as claimed in claims I wherein said voltage output in step a) is the voltage at the device terminals.</p>
    <p>4. A method as claimed in any preceding claim wherein steps a) or b) includes integrating the output.</p>
    <p>5. A method as claimed in integration time is over one or more full PWM periods 6. A method as claimed in any preceding claim wherein in step a) a counter is used at the output of the PWM inverter with DC link voltage, 7. A method as claimed in any previous claims wherein step d) comprises lengthening or shortening the periods of the voltage pulse from the inverter.</p>
    <p>8. A method as claimed in any previous claim wherein said device is an electric motor.</p>
    <p>9. A system for controlling an electrical device by means of a pulse width modulator inverter connected to said device having means to measure the voltage output over a full pulse period, a) means to determining the demand voltage; b) means to determine there error between them; and c) means to apply compensation to the voltage output of the inverter dependent on said error.</p>
    <p>10. A system as claimed in claim 9 wherein said voltage output is the output from the inverter.</p>
    <p>1. A system as claimed in claim 9 wherein said voltage output is the voltage at the device terminals.</p>
    <p>12. A system as claimed as claimed in claims 9, 10 or 11 including an integration system.</p>
    <p>13. A system as claimed in any preceding claim wherein in step b) a counter is used at the 14. A system as claimej in any of claims 9 wherein c) includes means to lengthening or shortening the periods of the voltage pulse from the inverter.</p>
GB0619440A 2006-08-04 2006-10-03 Voltage source inverter output voltage error compensation Expired - Fee Related GB2440559B (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GBGB0615488.4A GB0615488D0 (en) 2006-08-04 2006-08-04 Voltage source inverter output voltage error compensation

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GB0619440D0 GB0619440D0 (en) 2006-11-08
GB2440559A true GB2440559A (en) 2008-02-06
GB2440559B GB2440559B (en) 2009-02-25

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102008022928A1 (en) 2008-05-09 2009-11-19 Siemens Aktiengesellschaft Drive has intermediate voltage circuit converter and electric motor which is attached at terminals with outputs of load-side pulse power converter, where converter output-side measuring current is provided with signal input
US20130175965A1 (en) * 2011-07-08 2013-07-11 Siemens Aktiengesellschaft Method for estimating a torque of a three-phase drive motor for a vehicle
DE102013201253A1 (en) 2013-01-26 2014-07-31 Lenze Automation Gmbh Method and device for generating a digital signal
EP3109651A1 (en) * 2015-06-25 2016-12-28 Lenze Automation Gmbh Method for determining at least one parameter of an electric machine and frequency converter
US11316459B2 (en) 2015-12-16 2022-04-26 ZF Automotive UK Limited Motor control system

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6481665A (en) * 1987-09-21 1989-03-27 Nissin Electric Co Ltd Voltage type pwm inverter device
JPH0213270A (en) * 1988-06-28 1990-01-17 Fuji Electric Co Ltd Control circuit for three-phase inverter
EP0439642A1 (en) * 1990-01-29 1991-08-07 Kabushiki Kaisha Toshiba Control apparatus for inverter
JPH10243662A (en) * 1997-02-25 1998-09-11 Meidensha Corp Output voltage detecting apparatus of 3-level inverter

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6481665A (en) * 1987-09-21 1989-03-27 Nissin Electric Co Ltd Voltage type pwm inverter device
JPH0213270A (en) * 1988-06-28 1990-01-17 Fuji Electric Co Ltd Control circuit for three-phase inverter
EP0439642A1 (en) * 1990-01-29 1991-08-07 Kabushiki Kaisha Toshiba Control apparatus for inverter
JPH10243662A (en) * 1997-02-25 1998-09-11 Meidensha Corp Output voltage detecting apparatus of 3-level inverter

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102008022928A1 (en) 2008-05-09 2009-11-19 Siemens Aktiengesellschaft Drive has intermediate voltage circuit converter and electric motor which is attached at terminals with outputs of load-side pulse power converter, where converter output-side measuring current is provided with signal input
DE102008022928B4 (en) * 2008-05-09 2012-04-19 Siemens Aktiengesellschaft Drive and method for correcting a voltage error of the drive
US20130175965A1 (en) * 2011-07-08 2013-07-11 Siemens Aktiengesellschaft Method for estimating a torque of a three-phase drive motor for a vehicle
US8947037B2 (en) 2011-07-08 2015-02-03 Siemens Aktiengesellschaft Method for estimating a torque of a three-phase drive motor for a vehicle
DE102013201253A1 (en) 2013-01-26 2014-07-31 Lenze Automation Gmbh Method and device for generating a digital signal
WO2014114755A2 (en) 2013-01-26 2014-07-31 Lenze Automation Gmbh Method and device for producing a digital signal
WO2014114755A3 (en) * 2013-01-26 2015-02-19 Lenze Automation Gmbh Method and device for producing a digital signal
US9270294B2 (en) 2013-01-26 2016-02-23 Lenze Automation Gmbh Method and device for producing a digital signal
EP3109651A1 (en) * 2015-06-25 2016-12-28 Lenze Automation Gmbh Method for determining at least one parameter of an electric machine and frequency converter
US11316459B2 (en) 2015-12-16 2022-04-26 ZF Automotive UK Limited Motor control system

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Publication number Publication date
GB0615488D0 (en) 2006-09-13
GB0619440D0 (en) 2006-11-08
GB2440559B (en) 2009-02-25

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PCNP Patent ceased through non-payment of renewal fee

Effective date: 20131003