Control device for power conversion device, power conversion device, electric motor drive system using said devices, compressor drive system, and gas turbine power generation system

1. A control device for power conversion that controls a power conversion device in a system driven by the power conversion device to which an electric motor outputs AC power,

the control device for power conversion device comprising:

a control pulse generation unit configured to generate a control pulse of the power conversion device;

a negative phase creation unit configured to invert a pulse signal output by the control pulse generation unit and rotational speed information of the electric motor, and to generate an inverted pulse signal;

a signal synthesizing unit configured to synthesize the pulse signal of the control pulse generation unit and the inverted pulse signal of the negative phase creation unit; and

wherein the negative phase creation unit includes a half cycle pulse signal of a half cycle during one cycle of voltage, the pulse signal being generated by the control pulse generation unit, and a second pulse signal of a next half cycle during the one cycle of voltage, the inverted pulse signal being generated by the negative phase creation unit, are symmetrical in positive and negative relationship of voltage.

2. The control device for power conversion device according to claim 1 , wherein

the control pulse generation unit includes:

an output command generation unit configured to generate command information of an output of the power conversion device;

a voltage command calculation unit configured to calculate a voltage command value based on a current value of the output of the power conversion device, the rotational speed information of the electric motor, and the command information of the output command generation unit;

a carrier wave generation unit configured to generate a carrier wave; and

a comparison unit configured to compare the voltage command value and a voltage value of the carrier wave and to generate the pulse signal.

3. The control device for power conversion device according to claim 2 , wherein

the carrier wave generation unit includes a counter unit that is involved in determination of a cycle of the carrier wave, and

the counter unit is reset when the voltage command value is changed in an up direction and a down direction and passes through a predetermined value.

4. The control device for power conversion device according to claim 1 , wherein

the control pulse generation unit includes:

an output command generation unit configured to generate command information of an output of the power conversion device;

a voltage command calculation unit configured to calculate a voltage command value on the basis of a current value of the output of the power conversion device, the rotational speed information of the electric motor, and the command information of the output command generation unit;

a carrier wave generation unit configured to generate a carrier wave;

a comparison unit configured to compare the voltage command value and a voltage value of the carrier wave and to generate a positive-phase pulse signal;

a phase inverting unit configured to store the positive-phase pulse signal of the comparison unit, to generate, on the basis of phase information of the positive-phase pulse signal, a phase-inverted pulse signal with an inverted phase with respect to a time axis of every π/2, and to output the phase-inverted pulse signal; and

an output switch unit configured to switch and output the positive-phase pulse signal of the comparison unit and the phase-inverted pulse output by the phase inverting unit in every quarter cycle of π/2,

the half cycle pulse signal of the half cycle during one cycle of voltage, the pulse signal being generated by the control pulse generation unit, and the second half cycle pulse signal of the next half cycle during the one cycle of voltage, the inverted pulse signal being generated by the negative phase creation unit, are symmetrical in positive and negative relationship of voltage, and

a first half of the half cycle pulse signal and a second half of the half cycle pulse signal during the half cycle, the pulse signal being generated by the control pulse generation unit, are symmetrical with respect to a time axis of every π/2.

5. The control device for power conversion device according to claim 1 , wherein

the signal synthesizing unit is an adding unit that adds the pulse signal of the control pulse generation unit and the inverted pulse signal of the negative phase creation unit.

6. The control device for power conversion device according to claim 1 , wherein

the signal synthesizing unit is an output switch unit that switches and outputs the pulse signal of the control pulse generation unit and the inverted pulse signal of the negative phase creation unit.

7. A power conversion device comprising:

the control device for power conversion device according to claim 1 .

8. An electric motor drive system using the control device for power conversion according to claim 1 ,

the power conversion device being a neutral point grounding three-level power conversion device.

9. A compressor drive system using the control device for power conversion according to claim 1 , the compressor drive system further comprising:

a compressor using the electric motor as a power source.

10. A gas turbine power generation system using the control device for power conversion according to claim 1 , the gas turbine power generation system further comprising:

a compressor using the electric motor as a power source; and

a gas turbine having a rotating shaft to which the electric motor is connected, wherein

the electric motor is driven by the power conversion device, or regenerates power to the power conversion device.