Method of controlling a converter connected to an electric machine

Patent metadata

Field	Value
Publication number	US-10476355-B2
Application number	US-201916266918-A
Country	US
Kind code	B2
Filing date	Feb 4, 2019
Priority date	Feb 14, 2018
Publication date	Nov 12, 2019
Grant date	Nov 12, 2019

Abstract

The invention relates to a method for controlling a converter connected to an electric machine by a cable (Cx) via a filter (F), said method consisting in determining at least one sequence of a plurality of voltage pulses forming a square wave signal to be applied to each conductor so as to minimize an overvoltage level, said sequence comprising a number 2N of successive pulses, N being greater than or equal to 1, each pulse being defined by a distinct rank n, said sequence being generated such that each increasing voltage pulse of rank n exhibits a pulse width that is identical to that of a decreasing voltage pulse of rank equal to 2N+1−n, and the method includes the following steps in particular:
determining the number of successive pulses of said sequence; determining the width of each pulse of the sequence made suitable for minimizing the overvoltage level across the terminals of the electric machine (M).

First claim

The invention claimed is:

1. Method for controlling a converter connected to an electric machine by a cable (Cx) via a filter (F), said cable (Cx) comprising at least two conductors and exhibiting an impedance and said filter being an LC filter and comprising at least one inductor (Lf) and one capacitor (Cf) for each conductor of the cable, said converter comprising at least two switching arms each comprising at least two power switches that are switched so as to chop a DC voltage having a value E in order to deliver at least two voltage levels, the controlling of a switching arm making it possible to generate voltage pulses on the output phase that is connected thereto, a voltage pulse potentially being an increasing voltage pulse and including a rising vertical voltage edge or being a decreasing voltage pulse and including a falling vertical voltage edge, said method being characterized in that it consists in determining at least one sequence of a plurality of voltage pulses forming a square wave signal to be applied to each conductor on each switching, transition of the two power switches of one and the same switching arm so as to minimize an overvoltage level across the terminals of the electric machine (M), said sequence comprising a number 2N of successive pulses, N being greater than or equal to 1, each pulse being defined by a distinct rank n, said sequence being generated such that each increasing voltage pulse of rank n exhibits a pulse width that is identical to that of a decreasing voltage pulse of rank equal to 2N+1−n, and in that it includes the following steps:
determining the number of successive pulses of said sequence;
determining the width of each pulse of the sequence made suitable for minimizing the overvoltage level across the terminals of the electric machine (M) while satisfying the following relation:
t N =t p +t r /2

where:
t N corresponds to an instant in time of the end of the pulse of rank N;
t p corresponds to the propagation time of the cable;
t r corresponds to the rise time for the voltage (Vi) present at the input of the cable to reach 50% of said value E of the DC voltage.

2. Method according to claim 1 , characterized in that it includes a step of determining the overvoltage level on the basis of the following relation:

Int
Vo

=

lim

T
->
∞

⁢

1
T

⁢

∫
0
T

⁢

(

Vo
⁡

(

L
,
C
,
Zc
,

t
p

,

t
1

,

t
2

,

t
3

,

.

.

.

⁢

t

2
⁢
N

)

)

2

⁢
d
⁢

⁢
t

where:
Int Vo corresponds to said overvoltage level resulting from calculating the integral of the voltage Vo across the terminals of the electric machine;
L corresponds to the inductance of the inductor of the filter;
C corresponds to the capacitance of the capacitor of the filter;
Zc corresponds to the characteristic impedance of the cable.

3. Method according to claim 2 , characterized in that it includes at least one step of comparing the overvoltage level determined for said pulse sequence with a threshold value.

4. Method according to claim 3 , characterized in that it includes a step of increasing the number of pulses in the sequence for as long as the obtained overvoltage level exceeds said threshold value.

5. Method according to claim 1 , characterized in that it includes a step of determining the rise time for the voltage (Vi) at the input of the cable to reach 50% of said value E of the DC voltage on the basis of the following relation:
t r =f(L, C, Zc, d 1 , d 2 . . . d N )

where:
L corresponds to the inductance of the inductor of the filter;
C corresponds to the capacitance of the capacitor the filter;
Zc corresponds to the characteristic impedance of the cable;
d 1 , d 2 . . . d N correspond to the width of each pulse of rank n of said sequence of pulses.

6. Method according to claim 2 , characterized in that it includes a step of entering or of identifying the following parameters:
L, corresponding to the inductance of the inductor of the filter;
C, corresponding to the capacitance of the capacitor of the filter;
Zc, corresponding to the characteristic impedance of the cable;
tp, corresponding to the propagation time of the cable.

7. System for controlling a converter connected to an electric machine by a cable (Cx) via a filter (F), said cable (Cx) comprising at least two conductors and exhibiting an impedance and said filter being an LC filter and comprising at least one inductor (Lf) and one capacitor (Cf) for each conductor of the cable, said converter comprising at least two switching arms each comprising at least two power switches that are switched so as to chop a DC voltage having a value E in order to deliver at lea

Assignees

• Schneider Toshiba Inverter Europe Sas

Inventors

• Boulharts Hocine
• Fehringer Rudolf

Classifications

• H02P27/085

  wherein the PWM mode is adapted on the running conditions of the motor, e.g. the switching frequency · CPC title

• H02M1/126 Primary

  using passive filters · CPC title

• H02P2209/09

  PWM with fixed limited number of pulses per period · CPC title

• H02M1/44

  Circuits or arrangements for compensating for electromagnetic interference in converters or inverters · CPC title

• H02P27/08

  with pulse width modulation · CPC title