HARMONIC CURRENT SUPPRESSION METHOD AND HARMONIC CURRENT SUPPRESSION DEVICE OF POWER CONVERSION DEVICE

• US 20130135907A1
• Filed: 08/05/2011
• Published: 05/30/2013
• Est. Priority Date: 08/06/2010
• Status: Active Grant

• Current Assignee: Meidensha Corporation
• Original Assignee: Meidensha Corporation
• Inventors: Tadano, Yugo, Oi, Kazunobu
• Granted Patent: US 8,971,066 B2
• Time in Patent Office: Days
• US Class Current: 363/40
• CPC Class Codes: H02J 3/01 Arrangements for reducing harmonics or ripples
• CPC Class Codes: H02M 1/126 using passive filters
• CPC Class Codes: H02M 7/797 using semiconductor devices only
• CPC Class Codes: Y02E 40/40 Arrangements for reducing harmonics

Abstract

A current control unit takes a deviation between a current command value and a current flowing through an inverter of a power conversion device, and controls the inverter based on the deviation. A harmonic sensing part receives input of an output current of an AC filter, and outputs a predetermined order harmonic of the input current in a direct current value form. A disturbance observer estimates the disturbance of the harmonic based on the output current and a coefficient defined as an inverse function of a transfer function from harmonic suppression current command value to filter output current detection value. A harmonic suppression control unit takes the deviation between the estimated harmonic disturbance and a disturbance command value that suppresses the disturbance, and calculates a harmonic suppression current command value. The harmonic suppression current command value is superimposed on the current command value of the current control unit.

Claims

1. A harmonic current suppression device for a power conversion device, wherein an AC filter has one end connected to a system bus bar of an alternating current power supply and another end connected to the power conversion device, the harmonic current suppression device comprising:

a current control means that acquires a deviation between a current flowing through the power conversion device and a current command value of power conversion device current, and controls the power conversion device based on an output of the deviation; and

a harmonic suppression control means including;

a harmonic sensing part that receives input of an output current of the AC filter, and outputs a predetermined order harmonic of the input current in a direct current value form; and

a disturbance observer that estimates a disturbance of the harmonic by applying an output signal of the harmonic sensing part with a multiplier employing a coefficient, wherein the coefficient is defined as an inverse function of a transfer function from harmonic suppression current command value to current value inputted to the harmonic sensing part, wherein the coefficient is determined with measurement of a transfer characteristic of a control system;

wherein the harmonic suppression control means calculates a harmonic suppression current command value by acquiring a deviation between the estimated disturbance and a disturbance command value for disturbance suppression;

wherein the harmonic suppression current command value calculated by the harmonic suppression control means is superimposed on a current command value of the current control means, for harmonic current suppression.

2. The harmonic current suppression device as claimed in claim 1, wherein:

the harmonic current suppression device is provided with a plurality of the harmonic suppression control means in parallel, wherein the plurality of harmonic suppression control means correspond to a plurality of orders of harmonics;

the harmonic suppression current command values calculated by the harmonic suppression control means are summed;

the sum of the current command values is superimposed on the current command value of the current control means.

3. The harmonic current suppression device as claimed in claim 1, wherein:

the harmonic sensing part receives input of a summed current of the output current of the AC filter and a load current flowing through a load connected to the system bus bar, instead of input of the output current of the AC filter, and outputs a predetermined order harmonic of the input current in a direct current value form; and

the coefficient of the disturbance observer is defined as an inverse function of a transfer function from the harmonic suppression current command value to the summed current.

4. The harmonic current suppression device as claimed in claim 1, wherein:

the harmonic sensing part receives input of a system current flowing through the system bus bar, instead of input of the output current of the AC filter, and outputs a predetermined order harmonic of the input current in a direct current value form; and

the coefficient of the disturbance observer is defined as an inverse function of a transfer function from the harmonic suppression current command value to the system current.

5. The harmonic current suppression device as claimed in claim 1, wherein the harmonic sensed by the harmonic sensing part in the direct current value form has an order n wherein n=−

1 so that the harmonic suppression current command value calculated by the harmonic suppression control means is an opposite phase component of a fundamental.

6. The harmonic current suppression device as claimed in claim 1, wherein:

the coefficient of the disturbance observer is determined with or without measurement of the transfer characteristic of the control system;

the harmonic current suppression device includes;

a coefficient correction amount calculation section that;

evaluates an amount of change between a harmonic measured value of an output signal of the harmonic sensing part and a harmonic measured value one cycle before the output signal;

calculates as a phase correction amount of the coefficient a difference in phase between the harmonic measured value one cycle before the output signal and the amount of change; and

calculates as an amplitude correction amount of the coefficient a difference in amplitude between the harmonic measured value one cycle before the output signal and the amount of change; and

a coefficient correction means that corrects the phase of the coefficient by the phase correction amount calculated by the coefficient correction amount calculation section, and corrects the amplitude of the coefficient by the amplitude correction amount calculated by the coefficient correction amount calculation section.

7. The harmonic current suppression device as claimed in claim 6, wherein the coefficient correction means presets a condition for correction, and adjusts the calculated phase correction amount and amplitude correction amount, depending on whether or not the sensed harmonic conforms to the condition for correction.

8. The harmonic current suppression device as claimed in claim 1, wherein:

the current control means acquires a deviation between a d-axis component of the current flowing through the power conversion device and a current command value of d-axis component of power conversion device current and a deviation between a q-axis component of the current flowing through the power conversion device and a current command value of q-axis component of power conversion device current, and controls the power conversion device based on an output of the deviations; and

the harmonic sensing part of the harmonic suppression control means includes;

a discrete Fourier transformation part that applies d, q-axis transformation to the input current, and outputs a predetermined order harmonic of the input current in a direct current value form; and

a disturbance observer that estimates a disturbance of a d-axis component of the harmonic and a disturbance of a q-axis component of the harmonic by applying an output signal of the discrete Fourier transformation part with a multiplier employing a coefficient, wherein the coefficient is defined as an inverse function of a transfer function from harmonic suppression current command value of each of d-axis and q-axis components to current value inputted to the harmonic sensing part, wherein the coefficient is determined with measurement of the transfer characteristic of the control system;

wherein d-axis and q-axis harmonic suppression current command values are calculated by acquiring a deviation between the estimated disturbance and a disturbance command value for disturbance suppression;

wherein the d-axis and q-axis harmonic suppression current command values calculated by the harmonic suppression control means is superimposed on d-axis and q-axis current command values of the current control means, for harmonic current suppression.

9. The harmonic current suppression device as claimed in claim 8, wherein:

the disturbance observer estimates the disturbances by calculating (Ioutd·

Qam−

Ioutq·

Qbm)+j(Ioutq·

Qam+Ioutd·

Qbm) by applying a multiplier to a n-th order harmonic measured value of a d-axis output signal of the discrete Fourier transformation section represented by Ioutd and a n-th order harmonic measured value of a q-axis output signal of the discrete Fourier transformation section represented by Ioutq, wherein the multiplier employs the coefficient, wherein n is an integer other than zero, wherein the coefficient is defined as an inverse characteristic Qam+j·

Qbm of a transfer characteristic Pam+j·

Pbm from current command value to AC filter output current measured value;

the transfer characteristic of the control system is expressed in a complex number form wherein the d-axis component of the output current of the discrete Fourier transformation section is defined as a real part, and the q-axis component of the output current of the discrete Fourier transformation section is defined as an imaginary part; and

Pam represents an output current of the discrete Fourier transformation section that is in phase with harmonic suppression current command values of d-axis and q-axis components, and Pbm represents an output current of the discrete Fourier transformation section that is advanced by 90 degrees in phase from the harmonic suppression current command values of d-axis and q-axis components.

10. The harmonic current suppression device as claimed in claim 1, wherein:

the current control means obtains a single-phase voltage command value by addition of a reference sine wave to the output of deviation between the current flowing through the power conversion device and the current command value, and controls the power conversion device based on the single-phase voltage command value, wherein the reference sine wave is in phase with a voltage of an interconnection point between the system bus bar and the AC filter;

the harmonic sensing part of the harmonic suppression control means obtains a first product of the input current and a sine wave signal that is identical in frequency to a harmonic for which suppression is targeted and identical in phase to n times the phase of the voltage of the interconnection point between system bus bar and the AC filter, wherein n represents the order of the harmonic for which suppression is targeted, and extracts a direct current component of the first product, and obtains a harmonic measured signal in phase with the n-th order harmonic;

the harmonic sensing part of the harmonic suppression control means obtains a second product of the input current and a cosine wave signal that is identical in frequency to the harmonic for which suppression is targeted and identical in phase to n times the phase of the voltage of the interconnection point between system bus bar and the AC filter, wherein n represents the order of the harmonic for which suppression is targeted, and extracts a direct current component of the second product, and obtains a harmonic measured signal advanced by 90 degrees in phase from the n-th order harmonic; and

the disturbance observer of the harmonic suppression control means estimates the disturbance of the harmonic by applying the output signal of the harmonic sensing part with a multiplier employing a coefficient, wherein the coefficient is defined as an inverse function of a transfer function from a harmonic suppression current command value of a component in phase to the n-th order harmonic and a harmonic suppression current command value of a component advanced by 90 degrees in phase from the n-th order harmonic to a current value inputted to the harmonic sensing part, wherein the coefficient is determined with measurement of the transfer characteristic of the control system.

11. A harmonic current suppression method for a power conversion device, wherein an AC filter has one end connected to a system bus bar of an alternating current power supply and another end connected to the power conversion device, the harmonic current suppression method comprising:

a harmonic sensing step of causing a harmonic sensing part of a harmonic suppression control means to receive input of an output current of the AC filter, and output a predetermined order harmonic of the input current in a direct current value form;

a disturbance estimation step of causing a disturbance observer of the harmonic suppression control means to estimate a disturbance of the harmonic by applying an output signal of the harmonic sensing part with a multiplier employing a coefficient, wherein the coefficient is defined as an inverse function of a transfer function from harmonic suppression current command value to current value inputted to the harmonic sensing part, wherein the coefficient is determined with measurement of a transfer characteristic of a control system;

a harmonic suppression current command value calculation step of causing the harmonic suppression control means to calculate a harmonic suppression current command value by acquiring a deviation between the estimated disturbance and a disturbance command value for disturbance suppression; and

a step of causing a current control means to acquire a deviation between a current flowing through the power conversion device and a current command value, and control the power conversion device based on an output of the deviation, wherein the current command value is produced by superimposing the harmonic suppression current command value calculated by the harmonic suppression control means on a set current command value.

12. The harmonic current suppression method as claimed in claim 11, wherein:

the harmonic current suppression method is provided with a plurality of the harmonic suppression control means in parallel, wherein the plurality of harmonic suppression control means correspond to a plurality of orders of harmonics; and

the harmonic current suppression method comprises a step of causing the current control means to sum the harmonic suppression current command values calculated by the harmonic suppression control means, and superimpose the sum of the current command values on the current command value of the current control means.

13. The harmonic current suppression method as claimed in claim 11, wherein:

the harmonic sensing step is a step of receiving input of a summed current of the output current of the AC filter and a load current flowing through a load connected to the system bus bar, instead of input of the output current of the AC filter, and outputting a predetermined order harmonic of the input current in a direct current value form; and

the coefficient of the disturbance observer is defined as an inverse function of a transfer function from the harmonic suppression current command value to the summed current.

14. The harmonic current suppression method as claimed in claim 11, wherein:

the harmonic sensing step is a step of receiving input of a system current flowing through the system bus bar, instead of input of the output current of the AC filter, and outputs a predetermined order harmonic of the input current in a direct current value form; and

the coefficient of the disturbance observer is defined as an inverse function of a transfer function from the harmonic suppression current command value to the system current.

15. The harmonic current suppression method as claimed in claim 11, wherein the harmonic sensed by the harmonic sensing step in the direct current value form has an order n wherein n=−

1 so that the harmonic suppression current command value calculated by the harmonic suppression control means is an opposite phase component of a fundamental.

16. The harmonic current suppression method as claimed in claim 11, wherein:

the coefficient of the disturbance observer is determined with or without measurement of the transfer characteristic of the control system;

the harmonic current suppression method includes;

a coefficient correction amount calculation step of causing a coefficient correction amount calculation section of a coefficient correction means to;

evaluate an amount of change between a harmonic measured value of an output signal of the harmonic sensing part and a harmonic measured value one cycle before the output signal;

calculate as a phase correction amount of the coefficient a difference in phase between the harmonic measured value one cycle before the output signal and the amount of change; and

calculate as an amplitude correction amount of the coefficient a difference in amplitude between the harmonic measured value one cycle before the output signal and the amount of change; and

a coefficient correction step of causing the coefficient correction means to correct the phase of the coefficient by the phase correction amount calculated by the coefficient correction amount calculation section, and correct the amplitude of the coefficient by the amplitude correction amount calculated by the coefficient correction amount calculation section.

17. The harmonic current suppression method as claimed in claim 16, wherein the coefficient correction step presets a condition for correction, and adjusts the calculated phase correction amount and amplitude correction amount, depending on whether or not the sensed harmonic conforms to the condition for correction.

18. The harmonic current suppression method as claimed in claim 11, wherein:

the harmonic sensing step is a step of causing a discrete Fourier transformation part to apply d, q-axis transformation to the input current, and output a predetermined order harmonic of the input current in a direct current value form;

the disturbance estimation step is a step of estimating a disturbance of a d-axis component of the harmonic and a disturbance of a q-axis component of the harmonic by applying an output signal of the discrete Fourier transformation part with a multiplier employing a coefficient, wherein the coefficient is defined as an inverse function of a transfer function from harmonic suppression current command value of each of d-axis and q-axis components to current value inputted to the harmonic sensing part, wherein the coefficient is determined with measurement of the transfer characteristic of the control system;

the harmonic suppression current command value calculation step is a step of calculating d-axis and q-axis harmonic suppression current command values by acquiring a deviation between the estimated disturbance and a disturbance command value for disturbance suppression; and

the step of controlling the power conversion device is a step of acquiring a deviation between a d-axis component of the current flowing through the power conversion device and a current command value obtained by superimposing the d-axis harmonic suppression current command value calculated by the harmonic suppression control means on a d-axis current command value of the current control means, and acquiring a deviation between a q-axis component of the current flowing through the power conversion device and a current command value obtained by superimposing the q-axis harmonic suppression current command value calculated by the harmonic suppression control means on a q-axis current command value of the current control means, and controlling the power conversion device based on an output of the deviations.

19. The harmonic current suppression method as claimed in claim 18, wherein:

the disturbance estimation step is a step of estimating the disturbances by calculating (Ioutd·

Qam−

Ioutq·

Qbm)+j(Ioutq·

Qam+Ioutd·

Qbm) by applying a multiplier to a n-th order harmonic measured value of a d-axis output signal of the discrete Fourier transformation section represented by Ioutd and a n-th order harmonic measured value of a q-axis output signal of the discrete Fourier transformation section represented by Ioutq, wherein the multiplier employs the coefficient, wherein n is an integer other than zero, wherein the coefficient is defined as an inverse characteristic Qam+j·

Qbm of a transfer characteristic Pam+j·

Pbm from current command value to AC filter output current measured value;

the transfer characteristic of the control system is expressed in a complex number form wherein the d-axis component of the output current of the discrete Fourier transformation section is defined as a real part, and the q-axis component of the output current of the discrete Fourier transformation section is defined as an imaginary part; and

Pam represents an output current of the discrete Fourier transformation section that is in phase with harmonic suppression current command values of d-axis and q-axis components, and Pbm represents an output current of the discrete Fourier transformation section that is advanced by 90 degrees in phase from the harmonic suppression current command values of d-axis and q-axis components.

20. The harmonic current suppression method as claimed in claim 11, wherein:

the step of controlling the power conversion device is a step of obtaining a single-phase voltage command value by addition of a reference sine wave to the output of deviation between the current flowing through the power conversion device and the current command value, and controlling the power conversion device based on the single-phase voltage command value, wherein the reference sine wave is in phase with a voltage of an interconnection point between the system bus bar and the AC filter;

the harmonic sensing step includes a step of obtaining a first product of the input current and a sine wave signal that is identical in frequency to a harmonic for which suppression is targeted and identical in phase to n times the phase of the voltage of the interconnection point between system bus bar and the AC filter, wherein n represents the order of the harmonic for which suppression is targeted, and extracting a direct current component of the first product, and obtaining a harmonic measured signal in phase with the n-th order harmonic; and

a step of obtaining a second product of the input current and a cosine wave signal that is identical in frequency to the harmonic for which suppression is targeted and identical in phase to n times the phase of the voltage of the interconnection point between system bus bar and the AC filter, wherein n represents the order of the harmonic for which suppression is targeted, and extracting a direct current component of the second product, and obtaining a harmonic measured signal advanced by 90 degrees in phase from the n-th order harmonic; and

the disturbance estimation step is a step of estimating the disturbance of the harmonic by applying the output signal of the harmonic sensing part with a multiplier employing a coefficient, wherein the coefficient is defined as an inverse function of a transfer function from a harmonic suppression current command value of a component in phase to the n-th order harmonic and a harmonic suppression current command value of a component advanced by 90 degrees in phase from the n-th order harmonic to a current value inputted to the harmonic sensing part, wherein the coefficient is determined with measurement of the transfer characteristic of the control system.