Power Conversion Device and Control Device

Patent metadata

Field	Value
Publication number	US-2024297597-A1
Application number	US-202118697911-A
Country	US
Kind code	A1
Filing date	Oct 7, 2021
Priority date	Oct 7, 2021
Publication date	Sep 5, 2024
Grant date	—

Abstract

A current suppression control unit calculates correction terms of reference voltage command values for operating a power converter as a voltage source. The correction terms are calculated to compensate for respective current deviations of output currents transformed on two axes, with respect to current command values on a two-axis rotating coordinate system for suppressing an output current of the power converter to less than or equal to a control upper limit value. A proportional control unit has proportional elements to reflect the current deviations in the correction terms within the same axes of the two axes. A decoupling control unit has integral elements to reflect the current deviations in the correction terms between the different two axes.

First claim

1 . A power conversion device comprising:
at least one power converter configured to include switching elements, for converting DC power from a DC power source into AC power and outputting the AC power to a power system; and a control device to control power conversion in the power converter, the control device including
a voltage control unit to generate a reference voltage command value for operating the power converter as a voltage source that outputs an AC voltage having a frequency and a phase which are different from those in the power system,
a current suppression control unit to calculate a correction term for a current suppression control to suppress an output current from the power converter to less than or equal to a predefined control upper limit value base on a detected value of the output current, and to generate a voltage command value of the power converter by reflecting the correction term in the reference voltage command value, and
a switching control unit to control turning on/off of the switching elements of the power converter according to the voltage command value in which the correction term is reflected,
the current suppression control unit having
a current command value generation unit to generate current command values of a first axis and a second axis on a two-axis rotating coordinate system,
a control computation unit to calculate respective current deviations of the first axis and the second axis of the output current obtained by transforming the detected value to the rotation coodinate system, with respect to the current command values of the first axis and the second axis, and to calculate, on the rotating coordinate system, the correction term of the first axis and the second axis for compensating for the calculated respective current deviations of the output current of the first axis and the second axis, and
a voltage command value correction unit to calculate the voltage command value using the correction term and the reference voltage command value,

the current command value generation unit setting the current command values of the first axis and the second axis at output currents of the first axis and the second axis corresponding to the control upper limit value, when the output current is more than the control upper limit value, and setting the current command values of the first axis and the second axis substantially equal to the output current of the first axis and the second axis, when the output current is less than the control upper limit value, and
the control computation unit having
a first proportional element configured to output a value obtained by multiplying the current deviation of the first axis by a proportional gain,
a second proportional element configured to output a value obtained by multipling the current deviation of the second axis by a proportional gain, and
a decoupling control unit to calculate the correction term,
the decoupling control unit having
a first integral element configured to output a value obtained by multiplying an integral value of the current deviation of the first axis by an integral gain, and

a second integral element configured to output a value obtained by multiplying an integral value of the current deviation of the second axis by an integral gain, wherein
the decoupling control unit is configured to calculate the correction term of the first axis using the output values of the first proportional element and the second integral element, and to calculate the correction term of the second axis using the output values of the second proportional element and the first integral element, and the voltage command value correction unit is configured to calculate the voltage command value of the first axis using the reference voltage command value of the first axis transformed on the rotating coordinate system and the correction term of the first axis by the decoupling control unit, and to calculate the voltage command value of the secon axis using the reference voltage command value of the second axis transformed on the rotating coordinate system and the correction term of the second axis by the decoupling control unit.

2 . The power conversion device according to claim 1 , wherein, when the output current is less than the control upper limit value, each of calculated values of the current deviations of the first axis and the second axis is set to zero in the control computation unit.

3 . (canceled)

4 . The power conversion device according to claim 1 , wherein the decoupling control unit further has an integration reset unit to clear an output value of each of the first and second integral elements to zero when the output current is equal to the control upper limit value.

5 . The power conversion device according to claim 1 , wherein
a plurality of the power converters are arranged, the plurality of power converters are connected to the power system in parallel via a multiple voltage transformer, and the control device operates the plurality of power converters in parallel, according to the voltage command value that is common in which the correction term is reflected.

6 . A control device for a power converter configured to include switching elements, for converting DC power from a DC power source into AC power and outputting the AC power to a power system, the control device comprising:
a voltage control unit to generate a reference voltage command value for operating the power converter as a voltage source that outputs an AC voltage having a frequency and a phase which are different from those in the power system, a current suppression control unit to calculate a correction term for a current suppression control to suppress an output current from the power converter to less than or equal to a predefined control upper limit value base on a detected value of the output current, and to generate a voltage command value of the power converter by reflecting the correction term in the reference voltage command value, and a switching control unit to control turning on/off of the switching elements of the power converter according to the voltage command value in which the correction term is reflected, the current suppression control unit including
a control computation unit to calculate respective current command values of a first axis and a second axis on a two-axis rotating coordinate system,
a control comoutation unit to calculate respective current deviations of the first axis and the second axis of the output current obtained by transforming the detected value to the rotating coordinate system, with respect to the current command values of the first axis and the second axis, and to calculate, on the rotating coordinate system, the correction term of the first axis and the second axis for compensating for the calculated respective current deviations of the output current of the first axis and the second axis, and
a voltage command value correction unit to calculate the voltage command value using the correction term and the reference voltage command value,
the current command value generation unit setting the current command values of the first axis and the second axis at outut currents of the first axis and the second axis corresponding to the control upper limit value, when the output currentis more than the control upper limit value, and setting the current command values of the first axis and the second axis substantially equal to the output current of the first axis and the second axis, when the control current is less than the control upper limit value, and
the control computation unit having
a first proportional element configured to output a value obtained by multiplying the current deviation of the first axis by a proportional gain
a second proportional element configured to output a va

Assignees

• Mitsubishi Electric Corp

Inventors

• MUKUNOKI Kaho
• Fujii Toshiyuki
• Uda Ryosuke
• Hamanaka Kota
• Fujiwara Shuhei

Classifications

• H02M1/0025

  Arrangements for modifying reference values, feedback values or error values in the control loop of a converter · CPC title

• Y02E10/56

  Power conversion systems, e.g. maximum power point trackers · CPC title

• H02M7/53871 Primary

  with automatic control of output voltage or current · CPC title

• H02M7/48 Primary

  using discharge tubes with control electrode or semiconductor devices with control electrode · CPC title