Yu U Liu

US Patent:

20120194005, Aug 2, 2012

Filed:

Jan 27, 2011

Appl. No.:

13/014768

Inventors:

YU LIU - Milwaukee WI, US
Christopher S. Thompson - Kingston RI, US
Vijay Bhavaraju - Germantown WI, US

International Classification:

H02J 1/10

US Classification:

307151

Abstract:

A power flow regulator includes a plurality of bi-directional DC-DC converters, each of said converters comprising a first input, a second input, a first output and a second output; and a capacitor electrically connected between the first and second inputs of each of said converters. Either the first output of each of said converters is electrically connected to a corresponding DC source and the second output of each of said converters is electrically connected to a common DC load, or the first output of each of said converters is electrically connected to a corresponding DC load and the second output of each of said converters is electrically connected to a common DC source.

US Patent:

20130027077, Jan 31, 2013

Filed:

Jul 28, 2011

Appl. No.:

13/193026

Inventors:

Yu Liu - Milwaukee WI, US
Debrup Das - Atlanta GA, US
Pasi S. Taimela - Wake Forest NC, US
Bobby L. Compton - Raleigh NC, US

International Classification:

G01R 31/40

US Classification:

32476401

Abstract:

A fault in a DC power source, such as a battery string or a string of photovoltaic cells, is identified by detecting a change in an AC component of a residual current of the DC power source. In some embodiments, the DC power source is coupled to at least one DC bus and he methods further include generating an AC voltage on the at least one DC bus. For example, the DC power source may be coupled to a modulated DC bus of an uninterruptible power supply (UPS) system comprising an inverter having an input coupled to the DC bus. The inverter may be configured to generate an AC output voltage and the AC component has a frequency that is a harmonic of a fundamental frequency of the AC output voltage, such as a third harmonic of the fundamental frequency of the AC output voltage.

US Patent:

20130069438, Mar 21, 2013

Filed:

Sep 21, 2011

Appl. No.:

13/238103

Inventors:

Yu Liu - Milwaukee WI, US
George W. Oughton - Raleigh NC, US
Christopher Scott Thompson - Kingston RI, US

International Classification:

H02J 1/00

US Classification:

307 82

Abstract:

A PV system includes a plurality of PV strings each having an optimal string voltage at which a string output power is maximized. The PV strings are connected to a DC link in a parallel arrangement such that each PV strings operates at a variable DC link voltage. A PV inverter is connected to the DC link to receive a DC output, with the PV inverter controlling the DC link voltage. Delta DC/DC converters are connected to the PV strings, with each DC/DC converter receiving the DC link voltage from the DC link and providing a tuning voltage to the DC link voltage at which its respective PV string operates in order to bring the string voltage for that PV string to its optimal string voltage. The tuning voltage of each delta DC/DC converter is the difference between the DC link voltage and a respective optimal string voltage.

US Patent:

20140070815, Mar 13, 2014

Filed:

Sep 10, 2012

Appl. No.:

13/607932

Inventors:

Yu Liu - Milwaukee WI, US
Charles John Luebke - Hartland WI, US
Christopher Scott Thompson - Kingston RI, US

International Classification:

G01R 31/14

US Classification:

324510

Abstract:

A PV system includes a plurality of PV strings configured to generate a string output power responsive to received solar irradiation, with a source conductor and a return conductor being provided from the PV strings. One or more DC voltage regulators are electrically connected to the PV strings on at least one of the source or return conductors, with the DC voltage regulator being configured to regulate the voltage of a respective PV string or group of strings. A controller selectively controls a voltage output by the DC voltage regulator and is programmed to periodically cause the DC voltage regulator to alter the voltage of a PV string or group of strings, detect a change in current in the respective PV string(s) responsive to the altering of the voltage, and perform at least one of a PV string degradation detection and causal diagnosis and a grounded conductor fault detection.

US Patent:

20200006978, Jan 2, 2020

Filed:

Feb 4, 2019

Appl. No.:

16/266190

Inventors:

- Dublin 4, IE
Yu Liu - Milwaukee WI, US
Bobby L. Compton - Raleigh NC, US
Pasi S. Taimela - Wake Forest NC, US
Robert C. Sebald - Raleigh NC, US

International Classification:

H02J 9/06
H02J 3/38
H02J 7/00

Abstract:

An uninterruptible power supply (UPS) system includes a first port configured to be coupled to an AC power source and a second port configured to be coupled to a load. The system also includes a UPS circuit including a first converter circuit coupled to the first port, a second converter circuit coupled to the second port and a DC bus coupling the first converter circuit to the second converter circuit and configured to be coupled to an auxiliary power source and a third converter circuit coupled to the second port and configured to receive power from a variably available power source. The system further includes a control circuit operatively associated with the UPS circuit and the third converter circuit and configured to cooperatively control the UPS circuit and the third converter circuit to selectively transfer power to the load from the AC power source and the variably available power source and from the variably available power source to the AC power source.

US Patent:

20190215518, Jul 11, 2019

Filed:

Jan 10, 2018

Appl. No.:

15/866582

Inventors:

- San Diego CA, US
Marc Bosch Ruiz - Rockville MD, US
Yu Liu - Menlo Park CA, US
Shyamprasad Chikkerur - San Diego CA, US
Yunqing Chen - Los Altos CA, US
Tushar Singhal - San Diego CA, US
Shu Lin - San Diego CA, US
Kai Wang - San Diego CA, US
Harikrishna Reddy - San Jose CA, US

International Classification:

H04N 19/139
G06T 7/269
H04N 19/53
G06T 7/207

Abstract:

Methods, systems, and devices for motion analysis are described. Generally, the described techniques provide for computationally efficient and accurate motion analysis. A device may identify frames of a video frame sequence having a defined resolution. The device may downscale the frames to generate a plurality of downsampled images each having a resolution lower than the defined resolution. The device may generate a respective histogram vector for each pixel of each downsampled image and each pixel of the original frames. The device may determine a motion vector candidate based at least in part on the histogram vectors. The device may apply a filter to the motion vector candidates to determine a final motion vector and output an indication of motion between the frames of the video frame sequence based at least in part on the final motion vector for each pixel of the second frame.

US Patent:

20170077748, Mar 16, 2017

Filed:

Sep 21, 2016

Appl. No.:

15/271709

Inventors:

- Cleveland OH, US
Yu Liu - Milwaukee WI, US
Bobby L. Compton - Raleigh NC, US
Pasi S. Taimela - Wake Forest NC, US
Robert C. Sebald - Raleigh NC, US

International Classification:

H02J 9/06
H02J 7/00

Abstract:

An uninterruptible power supply (UPS) system includes a first port configured to be coupled to an AC power source and a second port configured to be coupled to a load. The system also includes a UPS circuit including a first converter circuit coupled to the first port, a second converter circuit coupled to the second port and a DC bus coupling the first converter circuit to the second converter circuit and configured to be coupled to an auxiliary power source and a third converter circuit coupled to the second port and configured to receive power from a variably available power source. The system further includes a control circuit operatively associated with the UPS circuit and the third converter circuit and configured to cooperatively control the UPS circuit and the third converter circuit to selectively transfer power to the load from the AC power source and the variably available power source and from the variably available power source to the AC power source.