Method and system for regulating instantaneous electromagnetic torque and storage medium for implementing the method

• US 7,095,197 B2
• Filed: 05/28/2004
• Issued: 08/22/2006
• Est. Priority Date: 06/02/2003
• Status: Active Grant

• Current Assignee: Alston UK Limited
• Original Assignee: Alstom SA
• Inventors: Alacoque, Jean-Claude, Benchaib, Abdelkrim, Poullain, Serge, Thomas, Jean-Luc
• Primary Examiner(s): IP, SHIK LUEN PAUL
• Application Number:
  US10/855,890
• Publication Number:
  US 20050001571A1
• Time in Patent Office: 816 Days
• Field of Search: 318430-433, 318/443, 318/722, 318/811, 363/40, 363/41
• US Class Current: 318/432
• CPC Class Codes: H02P 29/50 Reduction of harmonics

Abstract

A method is described of regulating the instantaneous electromagnetic torque of a polyphase rotating electrical machine equipped with stator and/or rotor windings supplied by a voltage and a current generated by an inverter formed of switches whose switching is controllable. The method comprises a step of commanding the switching of the switches of the inverter using the fundamental frequency of the voltage generated by the inverter and a form of synchronous pulse width modulation configured as a function of an input set point, and a step of calculating the input set point from an instantaneous torque set point at each regulation time. The method further comprises a step of determining the time interval between two successive regulation times so that the time interval corresponds to an integer multiple of the period of oscillation of the instantaneous torque of the machine.

Claims

1. A method of regulating the instantaneous electromagnetic torque of a polyphase rotating electrical machine equipped with stator and/or rotor windings supplied by a voltage and a current generated by an inverter formed of switches whose switching is controllable, said method comprising:

a step of commanding the switching of said switches of said inverter using a pulse width modulation synchronous with the fundamental frequency of said voltage generated by said inverter, wherein the pulse width modulation is configured as a function of an input set point, and

a step of calculating said input set point from an instantaneous torque set point at each regulation time, and

a step of determining the time interval (T) between two successive regulation times so that, as long as said instantaneous torque set point is constant, that time interval corresponds to an integer multiple of the period of oscillation of said instantaneous torque of said machine caused by second order or higher harmonics of said voltage and/or said current generated by said inverter.

2. A method claimed in claim 1, wherein said calculation step uses an exact response control method such that said instantaneous torque set point is reached at said first regulation time.

3. A method claimed in claim 1, for a machine equipped with a rotor, wherein said interval is further determined as a function of said instantaneous torque set point (Γ

_CS), the position (ρ

₀), and the angular speed (ω

) of said rotor of said machine.

4. A method claimed in claim 3, wherein said time interval (T) is determined for a synchronous machine with smooth poles using the following equations:

$\begin{array}{c}\sin <br><br>\left[<br><br>k·<br><br>\frac{\mathrm{\pi <br><br>}}{3}-\left({\mathrm{\rho <br><br>}}_0+\mathrm{\omega <br><br>}·<br><br>T+{\mathrm{\phi <br><br>}}_D\right)\right]={\mathrm{e<br><br>}}^{-\frac{T}{\mathrm{\tau <br><br>}}}·<br><br>\frac{<br><br>{\stackrel{\to <br><br>}{I}}_{\mathrm{dq}}^D\left(0\right)<br><br>}{<br><br>{\stackrel{\to <br><br>}{I}}_{\mathrm{dq}}^D\left(T\right)<br><br>}·<br><br>\sin <br><br>\left(k·<br><br>\frac{\mathrm{\pi <br><br>}}{3}-\left({\mathrm{\rho <br><br>}}_0+{\mathrm{\phi <br><br>}}_0\right)\right)\\ \begin{array}{ccc}\cos <br><br>\left({\mathrm{\phi <br><br>}}_D\right)=\frac{I_d^D<br><br>\left(T\right)}{<br><br>{\stackrel{\to <br><br>}{I}}_{\mathrm{dq}}^D\left(T\right)<br><br>}& & \cos <br><br>\left({\mathrm{\phi <br><br>}}_0\right)=\frac{I_d^D<br><br>\left(0\right)}{<br><br>{\stackrel{\to <br><br>}{I}}_{\mathrm{dq}}^D\left(0\right)<br><br>}\end{array}\\ \begin{array}{ccc}\sin <br><br>\left({\mathrm{\phi <br><br>}}_D\right)=\frac{I_q^D<br><br>\left(T\right)}{<br><br>{\stackrel{\to <br><br>}{I}}_{\mathrm{dq}}^D\left(T\right)<br><br>}& & \sin <br><br>\left({\mathrm{\phi <br><br>}}_0\right)=\frac{I_q^D<br><br>\left(0\right)}{<br><br>{\stackrel{\to <br><br>}{I}}_{\mathrm{dq}}^D\left(0\right)<br><br>}\end{array}\\ {\stackrel{\to <br><br>}{I}}_{\mathrm{dq}}^D\left(T\right)=<br><br>\begin{array}{c}{I}_d^D<br><br>\left(T\right)\\ I_q^D<br><br>\left(T\right)\end{array}<br><br>=<br><br>\begin{array}{c}{I}_d<br><br>\left(T\right)+\frac{X^2}{L·<br><br>Z^2}·<br><br>{\mathrm{\Phi <br><br>}}_a\\ I_q<br><br>\left(T\right)+\frac{R·<br><br>X}{L·<br><br>Z^2}·<br><br>{\mathrm{\Phi <br><br>}}_a\end{array}<br><br>\\ {\stackrel{\to <br><br>}{I}}_{\mathrm{dq}}^D\left(0\right)=<br><br>\begin{array}{c}{I}_d^D<br><br>\left(0\right)\\ I_q^D<br><br>\left(0\right)\end{array}<br><br>=<br><br>\begin{array}{c}{I}_d<br><br>\left(0\right)+\frac{X^2}{L·<br><br>Z^2}·<br><br>{\mathrm{\Phi <br><br>}}_a\\ I_q<br><br>\left(0\right)+\frac{R·<br><br>X}{L·<br><br>Z^2}·<br><br>{\mathrm{\Phi <br><br>}}_a\end{array}<br><br>\end{array}$

in which;

Φ

_a is the rotor flux of the magnets,

L is the stator inductance of the motor,

X is defined by the equation X=L.ω

, where ω

is the angular speed of the rotor,

Z is defined by the equation Z=√

{square root over (R²+L²ω

²)}, where R is the stator resistance of the machine,

I_d(O) and I_q(O) are the components of the instantaneous current vector measured at the regulation time in a rotating system of axes d,q fixed with respect to the rotor flux, the d axis being aligned with the rotor flux,

I_d(T) and I_q(T) are the components of the current vector set point corresponding to the instantaneous torque set point in the system of axes d, q, and

ρ

₀ is the angle between the system of axes d, q and a fixed system of axes α

, β

that is fixed with respect to the stator windings.

5. A method claimed in claim 1, wherein said regulation times are spaced by a time interval equal to T′

/2p where p is the number of phases of said machine and T′

is the period of said fundamental frequency of said voltage generated by said inverter.

6. A method claimed in claim 5, wherein said regulation times are chosen to correspond exactly to times at which the phase of said fundamental frequency of said voltage generated by said inverter is equal to kΠ

/p, where k is an integer.

7. A method claimed in claim 1, including a step of correcting said instantaneous torque set point if the interval (T) determined crosses a predefined time threshold, this correction step comprising:

a) an operation of taking the value of the threshold that has been crossed as the value of said interval, and

b) an operation of establishing a temporary instantaneous torque set point that can be reached using the time interval value established during the operation a).

8. A method claimed in claim 1, including a step of correcting said instantaneous torque set point if the input set point to be used during the control step crosses a predefined set point limit, this second correction step comprising:

an operation of establishing a new temporary instantaneous torque set point that complies with the predefined set point limit.

9. A method claimed in claim 8, wherein said predefined set point limit is measured at each current regulation time.

10. An information storage medium comprising instructions for executing a regulation method conforming to claim 1, when said instructions are executed by an electronic computer.

11. A system for regulating the instantaneous electromagnetic torque of a polyphase rotating electrical machine equipped with stator and/or rotor windings supplied by a voltage and a current generated by an inverter formed of switches whose switching is commandable, said system comprising:

a unit to command the switching of said switches of said inverter using a pulse width modulation synchronous with the fundamental frequency of the voltage generated by said inverter wherein the pulse width modulation is configured as a function of an input set point, and

a unit to calculate said input set point from an instantaneous torque set point, and

a unit to determine the time interval (T) between two successive regulation times so that, as long as said instantaneous torque set point is constant, that time interval corresponds to an integer multiple of the period of oscillation of the instantaneous torque of said machine caused by second order or higher harmonics of said voltage and/or said current generated by said inverter.