WO2008088313A1 - Suppression of low frequency ripple in fuel cell output current - Google Patents

Suppression of low frequency ripple in fuel cell output current Download PDF

Info

Publication number
WO2008088313A1
WO2008088313A1 PCT/US2006/049550 US2006049550W WO2008088313A1 WO 2008088313 A1 WO2008088313 A1 WO 2008088313A1 US 2006049550 W US2006049550 W US 2006049550W WO 2008088313 A1 WO2008088313 A1 WO 2008088313A1
Authority
WO
WIPO (PCT)
Prior art keywords
fuel cell
frequency
link
inductor
output
Prior art date
Application number
PCT/US2006/049550
Other languages
French (fr)
Inventor
Sandeep Bala
Steven J. Fredette
Original Assignee
Utc Fuel Cells, Llc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Utc Fuel Cells, Llc filed Critical Utc Fuel Cells, Llc
Priority to PCT/US2006/049550 priority Critical patent/WO2008088313A1/en
Publication of WO2008088313A1 publication Critical patent/WO2008088313A1/en

Links

Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/14—Arrangements for reducing ripples from dc input or output
    • H02M1/15—Arrangements for reducing ripples from dc input or output using active elements
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L2270/00—Problem solutions or means not otherwise provided for
    • B60L2270/10—Emission reduction
    • B60L2270/14—Emission reduction of noise
    • B60L2270/147—Emission reduction of noise electro magnetic [EMI]
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L58/00—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles
    • B60L58/30—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles for monitoring or controlling fuel cells

Definitions

  • Fuel cell systems generally provide their output to an AC load through a DC/AC inverter, which typically also employs power conditioning to assure that the output power is at the prescribed voltage, frequency and phase. If the load is driven with a single phase current, or if the load is driven with a three- phase current and the currents are unbalanced, a low frequency ripple, at twice the fundamental frequency, is reflected back to the fuel cell.
  • a fuel cell system 11 provides power to a load 12 through a DC/AC inverter 13, which includes power conditioning to assure that the load is provided with power over lines 14 at the correct voltage, frequency and phase.
  • the inverter 13 is interconnected 17 with a controller 18 in the fuel cell system.
  • a large bank of low frequency DC filter capacitors 20 have conventionally been connected across the output 21 , 22 of the fuel cell system, which comprises a DC link between the fuel cell 11 and the DC/AC inverter 13.
  • the DC capacitors are both heavy and expensive. Furthermore, they have a limited useful life of on the order of five or six years, therefore requiring maintenance and additional expense.
  • An inductor is connected across the output of a fuel cell stack by means of a switchable H bridge.
  • the switches operate by reversing the polarity of the inductor across the fuel cell stack at a high frequency relative to the low frequency ripple current which is, typically, twice the load frequency, which normally is -50 or 60 hertz.
  • the inductor switching polarity introduces an inverse low frequency ripple current that cancels the ripple current on the DC link.
  • the high frequency switching will typically be generated using a PWM (pulse width modulated) control, strategy although other methods such as space vector modulation could be employed.
  • Fig. 1 is a simplified schematic block diagram of a prior art fuel cell system utilizing a large bank of bulk DC capacitors to reduce low frequency ripple in the fuel cell output current.
  • Fig. 2 is a simplified block diagram of a fuel cell system having a switchable inductor connected across its output so as to reduce low frequency ripple in the fuel cell output current.
  • Fig. 2 size or number of DC capacitors required to treat ripple is greatly reduced, saving weight and extending the life of the system, by means of an inductor 27 which is connected across the fuel cell output 21 , 22 by means of switches 30-33.
  • the controller 18 operates the switches in a fashion such that the switches 30, 31 are closed by a signal on a line 36 when the switches 32, 33 are opened as illustrated in Fig. 2. Then, the switches 32 and 33 will be closed by a signal on a line 37 while the switches 30 and 31 will be open.
  • the switching back and forth is accomplished at a high frequency, such as between 20 and 100 times the frequency of the ripple current on the DC link 21 , 22, typically twice the load frequency of 50 Hz or 60 Hz.
  • a small, high frequency filter capacitor 40 may be connected across the fuel cell system outputs 21 , 22.
  • the inductor 27 when switched will always be of a polarity suitable to compensate out the ripple current in the output 21 , 22 of the fuel cell. This substantially eliminates any ripple in the fuel cell output current.
  • the switches 30-33 are preferably solid state switches, such as insulated gate bipolar transistors (IGBTs).
  • IGBTs insulated gate bipolar transistors
  • the life of the inductor and switches is much longer than the life of bulk DC capacitors.
  • the weight is significantly less.
  • the cost, over time is more favorable as well.

Abstract

An inductor (27) is connected by switches (30-33) across the DC link output (21, 22) of a fuel cell system (18) in alternatively-reversed fashion at a frequency which is high compared to ripple current on the DC link which is typically twice the fundamental frequency (e.g., 50 Hz or 60 Hz) of a DC/ AC inverter and power conditioner (13). This substantially eliminates ripple in the fuel cell output current without the use of a large bank of low frequency filter capacitors (20). The DC/AC inverter may have a small, high frequency filter capacitor (40) across its input.

Description

Suppression of Low Frequency Ripple in Fuel Cell Output Current
Technical Field
Low frequency ripple reflected into the output current of a fuel cell from its DC/AC power inverter is suppressed by means of an inductor switched between the fuel cell outputs within an H bridge at a high frequency relative to the low frequency ripple current.
Background Art
Fuel cell systems generally provide their output to an AC load through a DC/AC inverter, which typically also employs power conditioning to assure that the output power is at the prescribed voltage, frequency and phase. If the load is driven with a single phase current, or if the load is driven with a three- phase current and the currents are unbalanced, a low frequency ripple, at twice the fundamental frequency, is reflected back to the fuel cell.
It is known that low frequency ripple in the DC current output of a fuel cell degrades the fuel cell structure and shortens the life of the fuel cell.
In Fig. 1, a fuel cell system 11 provides power to a load 12 through a DC/AC inverter 13, which includes power conditioning to assure that the load is provided with power over lines 14 at the correct voltage, frequency and phase. The inverter 13 is interconnected 17 with a controller 18 in the fuel cell system.
To greatly reduce or eliminate low frequency ripple, a large bank of low frequency DC filter capacitors 20 have conventionally been connected across the output 21 , 22 of the fuel cell system, which comprises a DC link between the fuel cell 11 and the DC/AC inverter 13. However, the DC capacitors are both heavy and expensive. Furthermore, they have a limited useful life of on the order of five or six years, therefore requiring maintenance and additional expense.
Summary
It has been determined that switching the polarity of an inductor across the output of a fuel cell stack at a high frequency relative to the low frequency ripple current on the DC link 21, 22 will substantially eliminate such ripple current. The inductor provides an inverse representation of the ripple current which cancels out the ripple current on the DC link 21, 22.
An inductor is connected across the output of a fuel cell stack by means of a switchable H bridge. The switches operate by reversing the polarity of the inductor across the fuel cell stack at a high frequency relative to the low frequency ripple current which is, typically, twice the load frequency, which normally is -50 or 60 hertz. The inductor switching polarity introduces an inverse low frequency ripple current that cancels the ripple current on the DC link. The high frequency switching will typically be generated using a PWM (pulse width modulated) control, strategy although other methods such as space vector modulation could be employed.
Other improvements, features and advantages will become more apparent in the light of the following detailed description of exemplary embodiments, as illustrated in the accompanying drawings.
Brief Description of the Drawings
Fig. 1 is a simplified schematic block diagram of a prior art fuel cell system utilizing a large bank of bulk DC capacitors to reduce low frequency ripple in the fuel cell output current.
Fig. 2 is a simplified block diagram of a fuel cell system having a switchable inductor connected across its output so as to reduce low frequency ripple in the fuel cell output current.
Mode(s) of Implementation
Referring to Fig. 2, size or number of DC capacitors required to treat ripple is greatly reduced, saving weight and extending the life of the system, by means of an inductor 27 which is connected across the fuel cell output 21 , 22 by means of switches 30-33. The controller 18 operates the switches in a fashion such that the switches 30, 31 are closed by a signal on a line 36 when the switches 32, 33 are opened as illustrated in Fig. 2. Then, the switches 32 and 33 will be closed by a signal on a line 37 while the switches 30 and 31 will be open. The switching back and forth is accomplished at a high frequency, such as between 20 and 100 times the frequency of the ripple current on the DC link 21 , 22, typically twice the load frequency of 50 Hz or 60 Hz. A small, high frequency filter capacitor 40 may be connected across the fuel cell system outputs 21 , 22.
The inductor 27 when switched will always be of a polarity suitable to compensate out the ripple current in the output 21 , 22 of the fuel cell. This substantially eliminates any ripple in the fuel cell output current.
The switches 30-33 are preferably solid state switches, such as insulated gate bipolar transistors (IGBTs).
The life of the inductor and switches is much longer than the life of bulk DC capacitors. The weight is significantly less. The cost, over time is more favorable as well.

Claims

Claims
1. Apparatus comprising: a fuel cell system (11 ) having a DC link including a first output connection (21) and a second output connection (22); a controller (18); a load (12); a DC/AC inverter (13) connecting the output of said fuel cell system on the DC link to said load; characterized by: an inductor (27) having first and second ends; and switches (30-33) configured to alternatively (a) connect said first end to said first output connection and said second end to said second output connection and then (b) connect said second end to said first output connection and said first end to said second output connection, repetitively, at a frequency which is high relative to the frequency of ripple current on the DC link.
2. Apparatus according to claim 1 further characterized by: said switches (30-33) comprising solid state switches.
3. Apparatus according to claim 1 further characterized by: said switches (30-33) comprising insulated gate bipolar transistors.
4. Apparatus according to claim 1 further characterized by: a small, high frequency filter capacitor (40) connected across the outputs (21 , 22) of said fuel cell system (18)
5. Apparatus according to claim 1 further characterized in that said high frequency is between 20 and 100 times the frequency of the ripple current on the DC link.
6. A method of reducing low frequency ripple current on a DC link (21 , 22) at the output of a fuel cell system (11 ) configured to provide power to a load (12) through a DC/AC inverter (13), characterized by: switching the ends of an inductor (27) repetitively, at a frequency which is high relative to frequency of ripple current on the DC link, between two output connections (21, 22) of the DC link.
7. A method according to claim 6 characterized in that said high frequency is between about 20 and 100 times the frequency of the ripple current.
8. A method of reducing low frequency ripple current on a DC link (21 , 22) output connecting a fuel cell system (11 ) through a DC/AC inverter (13) o a load (12), characterized by: alternatively connecting (18, 30-33), repetitively, at a frequency which is high compared to frequency of ripple current on the DC link (a) a first end of an inductor (27) to a first output connection (21 , 22) of said DC link and a second end of said inductor to a second output connection (22, 21 ) of said DC link, and (b) the second end of said inductor to said first output connection (21 ) and the first end of said inductor to said second output connection (22).
9. A method according to claim 8 characterized in that said high frequency is between about 20 and 100 times the frequency of the ripple current.
PCT/US2006/049550 2006-12-28 2006-12-28 Suppression of low frequency ripple in fuel cell output current WO2008088313A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/US2006/049550 WO2008088313A1 (en) 2006-12-28 2006-12-28 Suppression of low frequency ripple in fuel cell output current

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US2006/049550 WO2008088313A1 (en) 2006-12-28 2006-12-28 Suppression of low frequency ripple in fuel cell output current

Publications (1)

Publication Number Publication Date
WO2008088313A1 true WO2008088313A1 (en) 2008-07-24

Family

ID=39636221

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US2006/049550 WO2008088313A1 (en) 2006-12-28 2006-12-28 Suppression of low frequency ripple in fuel cell output current

Country Status (1)

Country Link
WO (1) WO2008088313A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101877549A (en) * 2010-06-08 2010-11-03 南京航空航天大学 Method for inhibiting two-stage type orthogonal inverter input current low-frequency impulse

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20040223348A1 (en) * 2003-05-09 2004-11-11 West Richard T. Power converter with ripple current cancellation using skewed switching techniques

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20040223348A1 (en) * 2003-05-09 2004-11-11 West Richard T. Power converter with ripple current cancellation using skewed switching techniques

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101877549A (en) * 2010-06-08 2010-11-03 南京航空航天大学 Method for inhibiting two-stage type orthogonal inverter input current low-frequency impulse

Similar Documents

Publication Publication Date Title
JP4258739B2 (en) Method of converting electrical AC voltage of DC voltage source, especially photovoltaic DC voltage source into AC voltage
US9112412B2 (en) Full-bridge power converter
CN102918759A (en) Multi-level DC/AC converter
JP2003102181A (en) System and method for electric power supply
US10855167B2 (en) Power converter apparatus and methods using adaptive node balancing
CN105703650B (en) A kind of more T-shaped three-level inverter control method for parallel using SHEPWM
JP2005057995A (en) Method and system for improved heat management of power supply inverter operated at low output frequency by utilizing zero vector modulation method
CN105207508A (en) Fault-tolerant modulation method for co-busbar double-end cascade type five-level inverters
CN101860249B (en) Three-level inverter and zero-crossing switching logic control method thereof
KR102537096B1 (en) Power conversion device and its control method
EP2963801B1 (en) Speed-sensorless motor control device and method for starting speed-sensorless motor
JPWO2002082627A1 (en) Power converter
Devi et al. Comparative study on different five level inverter topologies
Ryoo et al. Unit power factor operation of parallel operated AC to DC PWM converter for high power traction application
WO2008088313A1 (en) Suppression of low frequency ripple in fuel cell output current
Raj et al. A modified charge balancing scheme for cascaded H-bridge multilevel inverter
CN103296910A (en) Direct voltage capture device for energy storage device and method for generating direct voltage by energy storage device
JPH09215205A (en) Power conversion apparatus
WO2010046962A1 (en) Prime mover system
CN111315614A (en) Vehicle charger including DC/DC converter
Cruise et al. Evaluation of a reduced topology phase-converter operating a three-phase induction motor
CN103296900A (en) Direct voltage capture device for energy storage device and method for generating direct voltage by energy storage device
Wang et al. Neutral-point potential balancing method for switched-inductor Z-source three-level inverter
CN108880392A (en) A kind of dead-zone compensation method, apparatus and system, a kind of drive control device
Xia et al. No dead‐time modulation algorithm for an off‐grid inverter based on H6 topology

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 06848323

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 06848323

Country of ref document: EP

Kind code of ref document: A1