US 9,026,347 B2Granted

Smart electric vehicle (EV) charging and grid integration apparatus and methods

AssigneeThe Regents of the University of California

InventorsRajit Gadh, Siddhartha Mal, Shivanand Prabhu, Chi-Cheng Chu, Omar Sheikh, Ching-Yen Chung, Lei He, Bingjun Xiao, Yiyu Shi

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Abstract

An expert system manages a power grid wherein charging stations are connected to the power grid, with electric vehicles connected to the charging stations, whereby the expert system selectively backfills power from connected electric vehicles to the power grid through a grid tie inverter (if present) within the charging stations. In more traditional usage, the expert system allows for electric vehicle charging, coupled with user preferences as to charge time, charge cost, and charging station capabilities, without exceeding the power grid capacity at any point. A robust yet accurate state of charge (SOC) calculation method is also presented, whereby initially an open circuit voltage (OCV) based on sampled battery voltages and currents is calculated, and then the SOC is obtained based on a mapping between a previously measured reference OCV (ROCV) and SOC. The OCV-SOC calculation method accommodates likely any battery type with any current profile.

Claims20

Dependent claims

An apparatus for determining instantaneous state of charge (SOC) for managing a battery in an electric vehicle, the apparatus comprising:

(a) a battery management circuit having a computer processor and memory configured for controlling battery charging in an electric vehicle;
(b) a voltage sensor connected to said battery management circuit and configured for measuring battery voltage;
(c) a current sensor connected to said battery management circuit configured for measuring battery current;
and
(d) programming executable from said computer processor of said battery management circuit for performing steps comprising:
(i) mapping a reference open circuit voltage (ROCV) to a reference state of charge (RSOC) of the battery through a discharge cycle to produce an ROCV-RSOC mapping;
(ii) measuring a current and a voltage over a period of time from the battery;
(iii) determining an open circuit voltage (OCV) of the battery under a load in response to:
(iii)(A) performing a time window based OCV extraction process in which over a plurality of short time windows OCV is extracted at multiple sample points in each of said short time windows;
(iii)(B) estimating battery terminal voltage at time t from a combination of zero-input response corresponding to a terminal voltage with no discharge current, plus a zero state response corresponding to battery terminal voltage with a discharge current i as input and voltage source shorted as determined from convolving an impulse response of the linear system with discharge current i;
(iii)(C) wherein zero-input response in a first of said short time windows as being actual open circuit battery terminal voltage;
(iii)(D) wherein in each short time window, after said first of said short time windows, impulse response is determined and a voltage removed which corresponds to voltage caused by current flow in previous windows;
(iv) determining an instantaneous state of charge (SOC) for the corresponding estimated open circuit voltage (OCV) in response to using said ROCV-RSOC mapping, without relying on a synthesizing circuit model of the battery which mimics specific battery behavior;
and
(v) outputting SOC on a display device.

12 more elements

An apparatus for determining instantaneous state of charge (SOC) for managing a battery in an electric vehicle, the apparatus comprising:

(a) a battery management circuit having a computer processor and memory configured for controlling battery charging in an electric vehicle;
(b) a voltage sensor connected to said battery management circuit and configured for measuring battery voltage;
(c) a current sensor connected to said battery management circuit configured for measuring battery current;
and
(d) programming executable from said computer processor of said battery management circuit determining state of charge (SOC), as a percentage value of energy available in the battery of the electric vehicle (EV), by performing steps comprising:
(i) mapping a reference open circuit voltage (ROCV) to a reference state of charge (RSOC) of the battery through a discharge cycle to produce an ROCV-RSOC mapping;
wherein said mapping of ROCV-RSOC includes determining a maximum capacity of the battery in response to a relation between measured current and voltage over a period of time from the battery, and tracking maximum capacity of the battery over time as a state of health of the battery;
(ii) measuring a current and a voltage over a period of time from the battery;
(iii) determining an open circuit voltage (OCV) of the battery under a load in response to:
(iii)(A) performing a time window based OCV extraction process in which over a plurality of short time windows OCV is extracted at multiple sample points in each of said short time windows;
(iii)(B) determining battery terminal voltage at time t from a combination of zero-input response corresponding to a terminal voltage with no discharge current, plus a zero state response corresponding to battery terminal voltage with a discharge current i as input and voltage source shorted as determined from convolving an impulse response of the linear system with discharge current i;
(iii)(C) wherein zero-input response in a first of said short time windows as being actual open circuit battery terminal voltage;
(iii)(D) wherein in each short time window, after said first of said short time windows, impulse response is determined and a voltage removed which corresponds to voltage caused by current flow in previous windows;
(iv) determining an instantaneous state of charge (SOC) for the corresponding determined open circuit voltage (OCV) in response to using said ROCV-RSOC mapping, without relying on a synthesizing circuit model of the battery which mimics specific battery behavior;
and
(v) outputting SOC on a display device.

13 more elements

Dependencies are inferred from the claim text.

Facts

Application: 13/693,747Filed 4 Dec 2012 · continuation
Priority: 10 Jun 2010
Published: US 2013/0179061 A111 Jul 2013
Granted: 5 May 2015
Term ends: Not estimatedThe source records don’t support an estimate.

Classification29 codes

B60L 53/67
Monitoring or controlling charging stations: controlling two or more charging stations
B60L 53/30
Methods of charging batteries, specially adapted for electric vehicles; Charging stations or on-board charging equipment therefor; Exchange of…:…
B60L 53/305
Constructional details of charging stations: communication interfaces
B60L 53/51
Charging stations characterised by energy-storage or power-generation means: photovoltaic means

Family

Application61/353,627Us provisional application · filed 10 Jun 2010
Application61/353,685Us provisional application · filed 11 Jun 2010
Application61/354,116Us provisional application · filed 11 Jun 2010
Application61/478,357Us provisional application · filed 22 Apr 2011
PCT/US2011/040077Parent of this continuation · filed 10 Jun 2011
US 2013/0179061 A1Pre-grant publication · published 11 Jul 2013
US 9,026,347 B2This patent

From the US filing history. Foreign family members aren’t listed.