Impedance measuring device and control method for impedance measuring device

• US 9,450,259 B2
• Filed: 01/23/2014
• Issued: 09/20/2016
• Est. Priority Date: 03/12/2013
• Status: Active Grant

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Sakai, Masanobu
• Primary Examiner(s): Pelton, Nathaniel
• Application Number:
  US14/774,474
• Publication Number:
  US 20160028095A1
• Time in Patent Office: 971 Days
• Field of Search: 429/430, 324/430
• US Class Current: 1/1
• CPC Class Codes: G01R 31/3648 comprising digital calculation means, e.g. for performing an algorithm
• CPC Class Codes: G01R 31/367 Software therefor, e.g. for battery testing using modelling or look-up tables
• CPC Class Codes: G01R 31/382 Arrangements for monitoring battery or accumulator variables, e.g. SoC
• CPC Class Codes: G01R 31/389 Measuring internal impedance, internal conductance or related variables
• CPC Class Codes: H01M 2008/1095 Fuel cells with polymeric electrolytes
• CPC Class Codes: H01M 8/04649 of fuel cell stacks
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

An impedance measuring device outputs an AC signal having a predetermined frequency to each of a positive electrode terminal and a negative electrode terminal of the fuel cell. The impedance measuring device includes a detection unit that detects an AC potential difference between the positive electrode terminal and a midpoint of the fuel cell, and an adjustment unit that adjusts an amplitude of the AC signal to adjust a detection signal to a predetermined value. The impedance measuring device includes an in-phase component extraction unit that multiplies the detection signal by an in-phase signal and extracts a resistance component of the detection signal, and a calculation unit that calculates a positive real axis impedance on the basis of the resistance component and the output signal. The impedance measuring device includes an orthogonal component extraction unit that multiplies the detection signal by an orthogonal signal and extracts a capacitance component of the detection signal, and a reproduction unit reproduces a vector value of the detection signal on the basis of the extracted capacitance component and resistance component. The adjustment unit adjusts the amplitude of the AC signal so that the reproduced vector value equals the predetermined value.

Claims

1. An impedance measuring device, comprising:

a fuel cell having a plurality of stacked battery cells, a capacitance component, and a resistance component, the capacitance component and the resistance component changing in accordance with a state of the battery cells;

a positive output unit configured to be connected to a positive electrode terminal of the fuel cell, the positive output unit outputting an AC signal having a predetermined frequency for measuring an internal impedance of the fuel cell;

a negative output unit configured to be connected to a negative electrode terminal of the fuel cell, the negative output unit outputting the AC signal having the predetermined frequency;

a detection unit configured to detect an AC potential difference between the positive electrode terminal and a midpoint of the fuel cell;

an adjustment unit configured to adjust an amplitude of the AC signal at the positive output unit so as to converge a detection signal indicating the AC potential difference on a predetermined value, the predetermined value bringing about a match between the detection signal indicating the AC potential difference and an AC potential difference between the negative electrode terminal and the midpoint;

an in-phase component extraction unit configured to multiply the detection signal indicating the AC potential difference by an in-phase signal, and extract a resistance component of the detection signal indicating the AC potential difference, the in-phase signal being in phase with the AC signal having the predetermined frequency;

a calculation unit configured to calculate a positive real axis impedance on the basis of the resistance component and the output signal;

an orthogonal component extraction unit configured to multiply the detection signal indicating the AC potential difference by an orthogonal signal, and extract a capacitance component of the detection signal indicating the AC potential difference, a phase of the orthogonal signal being orthogonal to a phase of the AC signal having the predetermined frequency; and

a reproduction unit configured to reproduce a vector value of the detection signal indicating the AC potential difference on the basis of the extracted capacitance component and resistance component, wherein

the adjustment unit configured to adjust the amplitude of the AC signal at the positive output unit so that the reproduced vector value equals the predetermined value.

2. The impedance measuring device according to claim 1, wherein

the in-phase component extraction unit includes:

an in-phase multiplication unit configured to output an in-phase AC signal by multiplying the detection signal indicating the AC potential difference by the in-phase signal; and

an in-phase low-pass filter configured to remove a high-frequency domain of the in-phase AC signal while allowing the resistance component of the detection signal indicating the AC potential difference to pass therethrough,

the orthogonal component extraction unit includes;

an orthogonal multiplication unit configured to output an orthogonal AC signal by multiplying the detection signal indicating the AC potential difference by the orthogonal signal; and

an orthogonal low-pass filter configured to remove a high-frequency domain of the orthogonal AC signal while allowing the capacitance component of the detection signal indicating the AC potential difference to pass therethrough, and

the reproduction unit outputs, as the vector value, a square root of a sum of a square of the resistance component and a square of the capacitance component.

3. The impedance measuring device according to claim 2, wherein

the in-phase multiplication unit includes:

an operational amplifier including an inverting input terminal, a non-inverting input terminal, and an output terminal, the inverting input terminal receiving, as input, the detection signal indicating the AC potential difference, the non-inverting input terminal receiving, as input, the same detection signal indicating the AC potential difference as the inverting input terminal, and the output terminal being connected to the in-phase low-pass filter; and

an in-phase switch configured to switch between an earthed state and a non-earthed state of the non-inverting input terminal in accordance with a rectangular pulse signal having the predetermined frequency, and cause the output terminal of the operational amplifier to output a rectified version of the in-phase AC signal, and

the orthogonal multiplication unit includes;

an operational amplifier including an inverting input terminal, a non-inverting input terminal, and an output terminal, the inverting input terminal receiving, as input, the detection signal indicating the AC potential difference, the non-inverting input terminal receiving, as input, the same detection signal indicating the AC potential difference as the inverting input terminal, and the output terminal being connected to the orthogonal low-pass filter; and

an orthogonal switch configured to switch between an earthed state and a non-earthed state of the non-inverting input terminal in accordance with an orthogonal pulse signal, and cause the output terminal of the operational amplifier to output a rectified version of the orthogonal AC signal, a phase of the orthogonal pulse signal being orthogonal to a phase of the rectangular pulse signal.

4. The impedance measuring device according to claim 2, wherein

the in-phase multiplication unit includes:

a first multiplier configured to output a positive AC signal by multiplying the detection signal indicating the AC potential difference by a positive constant;

a second multiplier configured to output a negative AC signal by multiplying the detection signal indicating the AC potential difference by a negative constant; and

an in-phase switch configured to switch between output from the first multiplier and output from the second multiplier in accordance with a rectangular pulse signal having the predetermined frequency, and output the in-phase AC signal rectified by the positive AC signal and the negative AC signal, and

the orthogonal multiplication unit includes;

a third multiplier configured to output a positive AC signal by multiplying the detection signal indicating the AC potential difference by a positive constant;

a fourth multiplier configured to output a negative AC signal by multiplying the detection signal indicating the AC potential difference by a negative constant; and

an orthogonal switch configured to switch between output from the third multiplier and output from the fourth multiplier in accordance with an orthogonal pulse signal, and output the orthogonal AC signal rectified by the positive AC signal and the negative AC signal, a phase of the orthogonal pulse signal being orthogonal to a phase of the rectangular pulse signal.

5. A control method for an impedance measuring device including:

a fuel cell having a plurality of stacked battery cells, a capacitance component, and a resistance component, the capacitance component and the resistance component changing in accordance with a state of the battery cells;

a positive output unit configured to be connected to a positive electrode terminal of the fuel cell, the positive output unit outputting an AC signal having a predetermined frequency for measuring an internal impedance of the fuel cell;

a negative output unit configured to be connected to a negative electrode terminal of the fuel cell, the negative output unit outputting the AC signal having the predetermined frequency; and

a detection unit configured to detect an AC potential difference between the positive electrode terminal and a midpoint of the fuel cell, the control method comprising;

adjusting an amplitude of the AC signal at the positive output unit so as to converge a detection signal indicating the AC potential difference detected by the detection unit on a predetermined value, the predetermined value bringing about a match between the detection signal indicating the AC potential difference and an AC potential difference between the negative electrode terminal and the midpoint;

multiplying the detection signal indicating the AC potential difference by an in-phase signal and extracting a resistance component of the detection signal indicating the AC potential difference, the in-phase signal being in phase with the AC signal having the predetermined frequency;

calculating a positive real axis impedance on the basis of the resistance component of the detection signal indicating the AC potential difference and the output signal output from the positive output unit;

multiplying the detection signal indicating the AC potential difference by an orthogonal signal and extracting a capacitance component of the detection signal indicating the AC potential difference, a phase of the orthogonal signal being orthogonal to a phase of the AC signal having the predetermined frequency; and

reproducing a vector value of the detection signal indicating the AC potential difference on the basis of the extracted resistance component and the extracted capacitance component, wherein

the amplitude of the AC signal at the positive output unit is adjusted so that the reproduced vector value equals the predetermined value.