Inverter and method for operating an inverter with angle-independent variation of pulse duty factor of switching elements
A method operates an inverter, wherein the inverter includes a number of bridge arms with respective bridge terminals, wherein a respective bridge arm is electrically connected on a first side to a first intermediate circuit pole of the inverter, and wherein a respective bridge arm is electrically connected on a second side to a second intermediate circuit pole of the inverter. A respective bridge arm has at least two switching elements, wherein a respective bridge terminal, depending upon a circuit state of the switching elements in the bridge arm, is electrically connected either to the first intermediate circuit pole or to the second intermediate circuit pole. A shunt resistor is arranged in a respective bridge arm. The method actuates the respective switching elements of the bridge arms via pulse width modulation with a temporally variable pulse duty factor, such that voltages between the bridge terminals show a temporally defined characteristic. The respective switching elements of the bridge arms are actuated with flat-top modulation for specific angular ranges of a respective fundamental wave, and a respective pulse duty factor for the switching elements of the bridge arms, immediately ahead of and/or immediately after the angular ranges, varies within a predefined time interval in an angularly-independent manner.
1. A method for operating an inverter, wherein the inverter comprises:
a plurality of bridge arms, each of which has a bridge terminal,
wherein each of the bridge arms is electrically connected on a first side to a first intermediate circuit pole of the inverter and electrically connected on a second side to a second intermediate circuit pole of the inverter,
wherein each of the bridge arms comprises at least two switching elements, wherein the bridge terminal, depending upon a circuit state of the switching elements, is electrically connected either to the first intermediate circuit pole or to the second intermediate circuit pole, and
wherein a shunt resistor is arranged in each of the bridge arms,
wherein the inverter is configured to generate a rotating field frequency having multiple values including at least two non-zero frequencies;
the method comprising the steps of:
actuating the switching elements of the bridge arms via pulse width modulation with a temporally variable pulse duty factor, such that voltages between the bridge terminals show a temporally defined characteristic,
wherein the switching elements of the bridge arms are actuated with flat-top modulation for specific angular ranges of a fundamental wave,
wherein the temporally variable pulse duty factor for the switching elements of the bridge arms, immediately ahead of or immediately after the angular ranges, varies within a predefined time interval in an angularly-independent manner.
2. The method according to claim 1 , wherein
the temporally variable pulse duty factor for the switching elements of the bridge arms, immediately ahead of and/or immediately after the angular ranges, varies within the predefined time interval in a time-dependent manner.
3. The method according to claim 1 , wherein
a duration of the predefined time interval, below a threshold rotating field frequency, is independent of the rotating field frequency generated by the inverter.
4. The method according to claim 1 , wherein
a characteristic of the temporally variable pulse duty factor remains constant within the predefined time interval.
5. The method according to claim 1 , wherein
a characteristic of the temporally variable pulse duty factor, within the predefined time interval, is represented by a straight line with a predefined gradient.
6. The method according to claim 1 , wherein
the predefined time interval extends over a number of pulse width modulation periods.
7. The method according to claim 6 , wherein
the number of pulse width modulation periods lies between 1 and 8.
8. The method according to claim 1 , wherein
the predefined time interval has a time duration in the range of 125 μs to 2 ms.
9. An inverter, comprising:
a plurality of bridge arms, each of which has a bridge terminal,
wherein each of the bridge arms is electrically connected on a first side to a first intermediate circuit pole of the inverter and electrically connected on a second side to a second intermediate circuit pole of the inverter,
wherein each of the bridge arms comprises at least two switching elements, wherein the bridge terminal, depending upon a circuit state of the switching elements, is electrically connected either to the first intermediate circuit pole or to the second intermediate circuit pole, and
wherein a shunt resistor is arranged in each of the bridge arms, and
a control unit which is configured to:
actuate the switching elements of the bridge arms via pulse width modulation with a temporally variable pulse duty factor, such that voltages between the bridge terminals show a temporally defined characteristic,
wherein the switching elements of the bridge arms are actuated with flat-top modulation for specific angular ranges of a fundamental wave, and
wherein the temporally variable pulse duty factor for the switching elements of the bridge arms, immediately ahead of or immediately after the angular ranges, varies within a predefined time interval in an angularly-independent manner; and
wherein the inverter is configured to generate a rotating field frequency having multiple values including at least two non-zero frequencies.
10. The inverter according to claim 9 , wherein
the temporally variable pulse duty factor for the switching elements of the bridge arms, immediately ahead of and/or immediately after the angular ranges, varies within the predefined time interval in a time-dependent manner.
11. The inverter according to claim 9 , wherein
a duration of the predefined time interval, below a threshold rotating field frequency, is independent of the rotating field frequency generated by the inverter.
12. The inverter according to claim 9 , wherein
a characteristic of the temporally variable pulse duty factor remains constant within the predefined time interval.
13. The inverter according to claim 9 , wherein
a characteristic of the temporally variable pulse duty factor, within the predefined time interval, is represented by a straight line with a predefined gradient.
14. The inverter according to claim 9 , wherein
the predefined time interval extends over a number of pulse width modulation periods.
15. The inverter according to claim 14 , wherein
the number of pulse width modulation periods lies between 1 and 8.
16. The inverter according to claim 9 , wherein
the predefined time interval has a time duration in the range of 125 μs to 2 ms.