Power converter and method including noise suppression by controlling phase shifting of converter cells
The noise generated from a power converter is suppressed by increasing the noise frequency to a level not lower than the maximum frequency of the human audible range. To obtain the frequency of an output current harmonic component as a noise source which has exceeded the maximum frequency of the human audible range, it is adequate to determine that the frequency of a driving carrier wave for the individual converter cells in the power converter, in which the phases of the carrier wave for the converter cells are mutually shifted by a given value between the converter cells, meets the following equation.
1. A power converter provided with a plurality of arms which are each comprised of a plurality of converter cells and having a plural phase construction, wherein each phrase corresponds to an arm configured by connecting the plurality of converter cell in series, comprising a controller configured to:
conduct interrupt processing of carrier waves of the converter cells to synchronize control of corresponding converter cells of the different arms,
wherein each carrier wave is shifted by a predetermined shift value at each arm such that each phase is different from each other, and
wherein each converter cell is driven, at each converter cell, by comparing a common instructed value per each arm and the carrier wave;
operate frequencies of the carrier waves of the converter cells in a state larger than a value which is obtained by dividing a maximum frequency of a human audible frequency band by the number of the converter cells in the arms; and
shift the value of the carrier wave at any converter cell to the predetermined shift value when the shift value of the carrier wave at that converter cell is displaced from the predetermined shift valued.
2. The power converter according to claim 1 , further comprising:
interconnected reactors;
buffer reactors; and
wherein:
control of the different arms and converter cells is in accordance with a control device and a signal line coupled to transmit a control signal from the control device to the converter cells, and
the arms are arranged on positive and negative sides of each of three phases.
3. The power converter according to claim 1 , wherein the converter cell is provided with:
a capacitor for storing electric power;
fuses for cutting off electric current in case of overcurrent;
a cell configured with a plurality of switching elements connected in a half bridge state;
a converter cell control circuit for outputting a control signal for the switching elements;
a gate driver for applying a voltage to the switching elements according to the control signal outputted from the converter cell control circuit;
a gate power supply for supplying necessary electric power to the gate driver; and
a self-feeding supply for supplying necessary electric power to the gate power supply and the converter cell control circuit.
4. The power converter according to claim 1 , wherein control of the different arms and converter cells is provided by:
a synchronous signal generator for generating a synchronous signal at every given time;
a carrier wave generator for generating a carrier wave for the converter cell after having as an input the synchronous signal which is outputted from the synchronous signal generator; and
an individual-phase target voltage generator for generating a target voltage of each of three phases which are mutually shifted by ⅓ cycle.
5. The power converter according to claim 1 , wherein a converter cell control circuit is provided with a comparator which outputs to a gate driver an ON/OFF signal for switching elements of a converter cell according to a magnitude relation between a target voltage and a carrier wave for the converter cell.
6. The power converter according to claim 1 , wherein the converter cell is provided with:
a capacitor for storing electric power;
fuses for cutting off an electric current in case of overcurrent;
a cell configured with a first leg and a second leg, which are configured with a plurality of switching elements connected in series, connected in a full bridge state;
a converter cell control circuit for outputting a control signal for the switching elements;
a gate driver for applying a voltage to the switching elements according to the control signal outputted from the converter cell control circuit;
a gate power supply for supplying necessary electric power to the gate driver; and
a self-feeding supply for supplying necessary electric power to the gate power supply and the converter cell control circuit.
7. The power converter according to claim 1 , wherein control of the different arms and converter cells is provided by:
a synchronous signal generator for generating a synchronous signal at every given time;
a carrier wave generator for generating a carrier wave for the converter cell after having as an input the synchronous signal which is outputted from the synchronous signal generator;
a first individual-phase target voltage generator for generating a target voltage of each of three phases which are mutually shifted by ⅓ cycle; and
a second individual-phase target voltage generator for outputting a target voltage with the phase shifted by ½ cycle with respect to the target voltage which is outputted from the first individual-phase target voltage generator.
8. The power converter according to claim 1 , wherein a converter cell control circuit is provided with:
a first comparator for generating an ON/OFF signal for switching elements, configuring a first leg of each converter cell, according to the magnitude relation between a target voltage outputted from a the first individual-phase target voltage generator and a carrier wave for the converter cell outputted from a carrier wave generator; and
a second comparator for generating an ON/OFF signal for switching elements, configuring a second leg of each converter cell, according to the magnitude relation between a target voltage outputted from a second individual-phase target voltage generator and a carrier wave for the converter cell outputted from the carrier wave generator.
9. The power converter according to claim 1 , wherein control of the different arms and converter cells is provided by:
a synchronous signal generator for generating a synchronous signal at every given time; and
an individual-phase target voltage generator for generating a target voltage of each of three phases which are mutually shifted by ⅓ cycle.
10. The power converter according to claim 1 , wherein a converter cell control circuit is provided with:
a carrier wave generator for outputting a carrier wave for the converter cell after having as an input a synchronous signal which is outputted from a synchronous signal generator; and
a comparator for generating an ON/OFF signal for a switching element of a converter cell according to the magnitude relation between a carrier wave for the converter cell outputted from the carrier wave generator and a target voltage outputted from an individual-phase target voltage generator.
11. The power converter according to claim 1 , wherein control of the different arms and converter cells is in accordance with a control device comprising:
a synchronous signal generator for generating a synchronous signal at every given time;
a first individual-phase target voltage generator for generating a target voltage of each of three phases which are mutually shifted by ⅓ cycle; and
a second individual-phase target voltage generator for outputting a target voltage with the phase shifted by ½ cycle with respect to the target voltage which is outputted from the first individual-phase target voltage generator.
12. The power converter according to claim 1 , wherein a converter cell control circuit is provided with:
a carrier wave generator for outputting a carrier wave for the converter cell after having as an input a synchronous signal which is outputted from a synchronous signal generator;
a first comparator for generating an ON/OFF signal for a switching element configuring a first cell according to the magnitude relation between a target voltage outputted from a first individual-phase target voltage generator and a carrier wave for the converter cell outputted from the carrier wave generator; and
a second comparator for generating an ON/OFF signal for a switching element configuring a second cell according to the magnitude relation between a target voltage outputted from a second individual-phase target voltage generator and a carrier wave for the converter cell outputted from the carrier wave generator.
13. The power converter according to claim 1 , wherein control of the different arms and converter cells is in accordance with a control device comprising:
an individual-phase target voltage generator for generating a target voltage of each of three phases which are mutually shifted by ⅓ cycle;
a synchronous signal generator for generating a synchronous signal at every given time;
a carrier wave generator for generating a carrier wave for the converter cell after having as an input the synchronous signal which is outputted from the synchronous signal generator; and
a comparator which outputs to a converter cell control circuit an ON/OFF signal for a switching element of the converter cell according to a magnitude relation between the target voltage and the carrier wave for the converter cell.
14. The power converter according to claim 1 , wherein control of the different arms and converter cells is in accordance with a control device comprising:
a first individual-phase target voltage generator for generating a target voltage of each of three phases which are mutually shifted by ⅓ cycle;
a second individual-phase target voltage generator for outputting a target voltage with the phase shifted by ½ cycle with respect to the target voltage which is outputted from the first individual-phase target voltage generator;
a synchronous signal generator for generating a synchronous signal at every given time;
a carrier wave generator for generating a carrier wave for the converter cell after having as an input the synchronous signal which is outputted from the synchronous signal generator;
a first comparator for generating an ON/OFF signal for switching elements, configuring a first leg of each converter cell, according to the magnitude relation between the target voltage outputted from the first individual-phase target voltage generator and the carrier wave outputted from the carrier wave generator; and
a second comparator for generating an ON/OFF signal for switching elements, configuring a second leg of each converter cell, according to the magnitude relation between the target voltage outputted from the second individual-phase target voltage generator and the carrier wave outputted from the carrier wave generator.
15. The power converter according to claim 1 , further comprising:
a transformer;
a buffer reactor; and wherein:
control of the different arms and converter cells is in accordance with a control device and a signal line couple to transmit a control signal from the control device to the converter cells, and
the arms are arranged on each of three phases.
16. The power converter according to claim 1 , further comprising:
interconnected reactors;
buffer reactors; and wherein;
control of the different arms and converter cells is in accordance with a control device,
the arms are arranged on positive and negative sides of each of three phases, and
a control signal between the control device and a converter cell control circuit is transmitted wirelessly.
17. The power converter according to claim 1 , further comprising:
a transformer;
a buffer reactor; and
wherein:
control of the different arms and converter cells is in accordance with a control device,
the arms are arranged on each of three phases, and
a control signal between the control device and a converter cell control circuit is transmitted wirelessly.
18. A power converting method for a power converter provided with a plurality of arms which are each comprised of a plurality of converter cells and having a plural phase construction, wherein each phase corresponds to an arm configured by connecting the plurality of converter calls in series, comprising:
conducting interrupt processing of carrier waves of the converter cells to synchronize control of corresponding converter cells of the different arms,
wherein each carrier wave is shifted by a predetermined shift value at each arm such that each phase is different from each other, and
wherein each converter cell is driven, at each converter cell, by comparing a common instructed value per each arm and the carrier wave;
operating frequencies of the carrier waves of the converter cells in a state larger than a value which is obtained by dividing a maximum frequency of a human audible frequency band by the number of the converter cells in the arms; and
shifting the value of the carrier wave at any converter cell to the predetermined shift value when the shift value of the carrier wave at that converter cell is displaced from the predetermined shift valued.
19. The power converter according to claim 1 , wherein shifting the value of the carrier wave to the predetermined shift value results in a phase shift which will ensure that noise frequency of the converter cells is not lower than the maximum frequency of a human audible frequency band.
20. The power converting method according to claim 18 , wherein shifting the value of the carrier wave to the predetermined shift value results in a phase shift which will ensure that noise frequency of the converter cells is not lower than the maximum frequency of a human audible frequency band.