Patents by Inventor Ngai Man Ho

Ngai Man Ho has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 10728981
    Abstract: Low cost and low power LED lamps exhibit current harmonic contents due to their nonlinear characteristics. A large scale lighting network requires tens to hundreds LED lamp installations, the resultant harmonic currents pollute the grid seriously. Furthermore, light intensity fluctuations are becoming a concern nowadays to many users, as a safety and a health problems. This phenomenon is mainly caused by heavy loads as they lead to voltage fluctuations and deteriorating in PQ and hence visual flickering in LED lamps. A single phase transformer-less unified power quality conditioner (UPQC) topology is provided with its controls to mitigate all PQ problems in a network.
    Type: Grant
    Filed: November 9, 2018
    Date of Patent: July 28, 2020
    Assignee: University of Manitoba
    Inventors: Ngai Man Ho, Radwa Abdalaal, Henry Shu Hung Chung
  • Patent number: 10381953
    Abstract: A bidirectional bridgeless buck-boost power converter circuit is provided that can function as both a voltage source inverter (VSI) circuit to transform direct current (DC) voltage to alternating current (AC) voltage and as a power factor corrector (PFC) circuit to transform AC voltage to DC voltage. The disclosed converter fully utilizes inductors to form a CL filter and buck-boost converter energy storage element. Thus, low inductance chokes are used in the converter, which leads to a higher power density and is more cost-effective. Further, the bridgeless configuration minimizes conduction losses of semiconductors, and coupled with the use of low inductance chokes this improves system efficiency.
    Type: Grant
    Filed: October 26, 2017
    Date of Patent: August 13, 2019
    Assignee: The University of Manitoba
    Inventors: Ngai Man Ho, King Man Siu
  • Patent number: 10199859
    Abstract: An uninterruptable power supply system is disclosed with a precharge converter for connecting to a DC link of the uninterruptable power supply system to a DC power supply, whereby the DC link comprises a first and a second DC bus line, which are both coupled to a common reference point, whereby the common reference point can be an AC power supply neutral of the uninterruptable power supply system, comprising power connectors for connecting to the DC power supply, a first and second output connector for connecting to the first and the second DC bus line, respectively, a converter circuit for receiving DC power from the power connectors and providing DC power to the first and second output connector, and a control unit for controlling operation of the converter circuit.
    Type: Grant
    Filed: December 5, 2016
    Date of Patent: February 5, 2019
    Assignee: ABB Schweiz AG
    Inventors: Carl Ngai-Man Ho, Esa-Kai Paatero, Nicola Notari
  • Publication number: 20180115256
    Abstract: A bidirectional bridgeless buck-boost power converter circuit is provided that can function as both a voltage source inverter (VSI) circuit to transform direct current (DC) voltage to alternating current (AC) voltage and as a power factor corrector (PFC) circuit to transform AC voltage to DC voltage. The disclosed converter fully utilizes inductors to form a CL filter and buck-boost converter energy storage element. Thus, low inductance chokes are used in the converter, which leads to a higher power density and is more cost-effective. Further, the bridgeless configuration minimizes conduction losses of semiconductors, and coupled with the use of low inductance chokes this improves system efficiency.
    Type: Application
    Filed: October 26, 2017
    Publication date: April 26, 2018
    Inventors: Ngai Man Ho, King Man Siu
  • Publication number: 20170085124
    Abstract: An uninterruptable power supply system is disclosed with a precharge converter for connecting to a DC link of the uninterruptable power supply system to a DC power supply, whereby the DC link comprises a first and a second DC bus line, which are both coupled to a common reference point, whereby the common reference point can be an AC power supply neutral of the uninterruptable power supply system, comprising power connectors for connecting to the DC power supply, a first and second output connector for connecting to the first and the second DC bus line, respectively, a converter circuit for receiving DC power from the power connectors and providing DC power to the first and second output connector, and a control unit for controlling operation of the converter circuit.
    Type: Application
    Filed: December 5, 2016
    Publication date: March 23, 2017
    Inventors: Carl Ngai-Man Ho, Esa-Kai Paatero, Nicola Notari
  • Patent number: 9344005
    Abstract: Exemplary embodiments are directed to methods and systems for producing a three-phase current to a three-phase output. Switching converters are used to generate a positive current, a negative current, and an intermediate current. The system is configured such that the produced positive current follows a path of a highest phase of a sinusoidal three-phase signal at a given time, the produced negative current follows a path of a lowest phase of the three-phase signal at the given time, and the produced intermediate current follows a path of a phase of the three-phase signal between the highest and the lowest phase at the given time. The produced currents are switched to each phase conductor of the three-phase output in sequence so that phase currents of the three-phase current are formed in the output conductors.
    Type: Grant
    Filed: February 21, 2014
    Date of Patent: May 17, 2016
    Assignee: ABB RESEARCH LTD.
    Inventors: Ngai-Man Ho, Gerardo Escobar, Francisco Canales
  • Patent number: 9331563
    Abstract: Exemplary embodiments are directed to an snubber circuit and a power converter having an active circuit. The snubber circuit includes a series connection of a first diode and a first inductor connected between a first interfacing point and a first connection point, a second diode connected between a second connection point and a second interfacing point, a series connection of a third diode and a second inductor between a third interfacing point and the second connection point, a switching device connected between the first connection point and the third interfacing point, and a first capacitor connected between the first connection point and the second connection point. The first, the second, and the third diode are forward-biased along a path between the first interfacing point and the second interfacing point and through the third interfacing point.
    Type: Grant
    Filed: April 1, 2014
    Date of Patent: May 3, 2016
    Assignee: ABB RESEARCH LTD
    Inventors: Tin-Ho Li, Ngai-Man Ho, Gerardo Escobar, Jonathan Bradshaw
  • Patent number: 9331486
    Abstract: An exemplary method and apparatus for detecting islanding conditions of a distributed grid are disclosed, wherein transfer of power through a power electrical unit is controlled on the basis of a control reference. The apparatus includes a first stage and a second stage performing a respective portion of the method. The first stage injects a reactive component to the control reference, and, for at least one electrical quantity of the grid, determines a change in the quantity induced by the injected component, and determines, on the basis of the change in the electrical quantity, whether to move to the second stage of the method.
    Type: Grant
    Filed: November 5, 2012
    Date of Patent: May 3, 2016
    Assignee: ABB RESEARCH LTD
    Inventors: Gerardo Escobar, Sami Pettersson, Leonardo-Augusto Serpa, Ngai-Man Ho, Antonio Coccia, Alexandre Oudalov, Adrian Timbus
  • Patent number: 9093917
    Abstract: A bridgeless power factor correction circuit as disclosed can include first and second input inductors, a series connection of a first diode and a first controllable semiconductor switch, and a series connection of a second diode and a second controllable semiconductor switch, the series connections being connected in parallel between positive and negative output terminals of the power factor correction circuit. The power factor correction circuit can include a switching circuit adapted to connect a capacitor between the input terminal and the output terminal such that the capacitor is connected between the first input terminal and a potential of the output terminal when input voltage connectable to the input terminals is positive and the capacitor is connected between the second input terminal and a potential of the output terminal when the input voltage connectable to the input terminals is negative.
    Type: Grant
    Filed: December 4, 2014
    Date of Patent: July 28, 2015
    Assignee: ABB TECHNOLOGY AG
    Inventors: Ngai-Man Ho, Tin-Ho Li
  • Publication number: 20150162822
    Abstract: A bridgeless power factor correction circuit as disclosed can include first and second input inductors, a series connection of a first diode and a first controllable semiconductor switch, and a series connection of a second diode and a second controllable semiconductor switch, the series connections being connected in parallel between positive and negative output terminals of the power factor correction circuit. The power factor correction circuit can include a switching circuit adapted to connect a capacitor between the input terminal and the output terminal such that the capacitor is connected between the first input terminal and a potential of the output terminal when input voltage connectable to the input terminals is positive and the capacitor is connected between the second input terminal and a potential of the output terminal when the input voltage connectable to the input terminals is negative.
    Type: Application
    Filed: December 4, 2014
    Publication date: June 11, 2015
    Applicant: ABB Technology AG
    Inventors: Ngai-Man Ho, Tin-Ho Li
  • Patent number: 9030854
    Abstract: An exemplary method and an apparatus implementing the method for an arrangement having a three-phase, multi-level inverter, an output LCL-filter connecting the inverter to a grid, and a virtual-ground connection between the LCL-filter and the neutral point of the DC-link. The method includes determining a zero-sequence component of an LCL-filter inverter-side current, calculating a zero-sequence damping and balancing voltage term based on the LCL-filter inverter-side current zero-sequence component and voltages over the two halves of the DC-link, and adding the zero-sequence damping and voltage balancing term to the output voltage reference.
    Type: Grant
    Filed: June 7, 2013
    Date of Patent: May 12, 2015
    Assignee: ABB Research Ltd
    Inventors: Gerardo Escobar, Sami Pettersson, Ngai-Man Ho
  • Patent number: 8929108
    Abstract: A method and an apparatus for controlling a grid-connected converter which includes a boost converter, a buck converter, and a current source inverter having an output CL filter. An input of the buck converter input is connected to an output of the boost converter, and an input of the current source inverter is connected to an output of the buck converter. The method includes controlling a boost converter input voltage, controlling a boost converter output voltage through control of a buck converter output voltage, and controlling the current source inverter to produce an AC current from the buck converter output voltage. The apparatus implements the method.
    Type: Grant
    Filed: February 21, 2013
    Date of Patent: January 6, 2015
    Assignee: ABB Research Ltd
    Inventors: Gerardo Escobar, Ngai-Man Ho, Sami Pettersson
  • Publication number: 20140313627
    Abstract: Exemplary embodiments are directed to an snubber circuit and a power converter having an active circuit. The snubber circuit includes a series connection of a first diode and a first inductor connected between a first interfacing point and a first connection point, a second diode connected between a second connection point and a second interfacing point, a series connection of a third diode and a second inductor between a third interfacing point and the second connection point, a switching device connected between the first connection point and the third interfacing point, and a first capacitor connected between the first connection point and the second connection point. The first, the second, and the third diode are forward-biased along a path between the first interfacing point and the second interfacing point and through the third interfacing point.
    Type: Application
    Filed: April 1, 2014
    Publication date: October 23, 2014
    Applicant: ABB Research Ltd
    Inventors: Tin-Ho LI, Ngai-Man Ho, Gerardo Escobar, Jonathan Bradshaw
  • Publication number: 20140241016
    Abstract: Exemplary embodiments are directed to methods and systems for producing a three-phase current to a three-phase output. Switching converters are used to generate a positive current, a negative current, and an intermediate current. The system is configured such that the produced positive current follows a path of a highest phase of a sinusoidal three-phase signal at a given time, the produced negative current follows a path of a lowest phase of the three-phase signal at the given time, and the produced intermediate current follows a path of a phase of the three-phase signal between the highest and the lowest phase at the given time. The produced currents are switched to each phase conductor of the three-phase output in sequence so that phase currents of the three-phase current are formed in the output conductors.
    Type: Application
    Filed: February 21, 2014
    Publication date: August 28, 2014
    Applicant: ABB Research Ltd
    Inventors: Ngai-Man HO, Gerardo ESCOBAR, Francisco CANALES
  • Publication number: 20140043014
    Abstract: A phase-locked loop and method for estimating a phase angle of a three-phase reference signal is disclosed, which includes an adaptive quadrature signal generator configured to calculate an estimated first state and an estimated second state of a model of an unbalanced three-phase system at a fundamental frequency of the reference signal on a basis of the reference signal and an estimated fundamental frequency; a reference frame transformation block configured to calculate a direct component and a quadrature component in a rotating reference frame synchronous with an estimated phase angle on a basis of the fundamental positive sequence component and the estimated phase angle, and configured to determine an estimate of an amplitude of the fundamental positive sequence component on the basis of the direct component; and an estimator configured to determine estimates of the estimated fundamental frequency and the estimated phase angle on the basis of the quadrature component.
    Type: Application
    Filed: August 12, 2013
    Publication date: February 13, 2014
    Applicant: ABB Technology AG
    Inventors: Ngai-Man HO, Gerardo ESCOBAR, Sami PETTERSSON
  • Publication number: 20130329471
    Abstract: An exemplary method and an apparatus implementing the method for an arrangement having a three-phase, multi-level inverter, an output LCL-filter connecting the inverter to a grid, and a virtual-ground connection between the LCL-filter and the neutral point of the DC-link. The method includes determining a zero-sequence component of an LCL-filter inverter-side current, calculating a zero-sequence damping and balancing voltage term based on the LCL-filter inverter-side current zero-sequence component and voltages over the two halves of the DC-link, and adding the zero-sequence damping and voltage balancing term to the output voltage reference.
    Type: Application
    Filed: June 7, 2013
    Publication date: December 12, 2013
    Inventors: Gerardo ESCOBAR, Sami PETTERSSON, Ngai-Man HO
  • Publication number: 20130229839
    Abstract: A method and an apparatus for controlling a grid-connected converter which includes a boost converter, a buck converter, and a current source inverter having an output CL filter. An input of the buck converter input is connected to an output of the boost converter, and an input of the current source inverter is connected to an output of the buck converter. The method includes controlling a boost converter input voltage, controlling a boost converter output voltage through control of a buck converter output voltage, and controlling the current source inverter to produce an AC current from the buck converter output voltage. The apparatus implements the method.
    Type: Application
    Filed: February 21, 2013
    Publication date: September 5, 2013
    Applicant: ABB Research Ltd.
    Inventors: Gerardo ESCOBAR, Ngai-Man Ho, Sami Pettersson
  • Patent number: 8488351
    Abstract: An exemplary non-isolated DC-DC converter for a solar power plant, can be adapted to connect to a full-bridge inverter. The converter includes positive and negative input terminals, and positive and negative output terminals. A plurality of switches, diodes, inductors and capacitors are connected in a circuit configuration to the input and output terminals. A control means is connected to the circuit for controlling the switching of a first, second, and third switch between an open and closed state.
    Type: Grant
    Filed: March 17, 2011
    Date of Patent: July 16, 2013
    Assignee: ABB Research Ltd.
    Inventors: Leonardo-Augusto Serpa, Francisco Canales, Ngai-Man Ho, Antonio Coccia
  • Publication number: 20120242152
    Abstract: An exemplary method is disclosed for searching a global maximum power point in an arrangement comprising a series connection of photovoltaic power sources. The method can include determining a value of a reference by adding an increment to a previous value of the reference, wherein the value of the increment is determined on the basis of the power produced by the power sources.
    Type: Application
    Filed: March 22, 2012
    Publication date: September 27, 2012
    Applicant: ABB Research Ltd
    Inventors: Gerardo ESCOBAR, Ngai-Man Ho, Sami Pettersson, Leonardo-Augusto Serpa, Antonio Coccia
  • Publication number: 20110228578
    Abstract: An exemplary non-isolated DC-DC converter for a solar power plant, can be adapted to connect to a full-bridge inverter. The converter includes positive and negative input terminals, and positive and negative output terminals. A plurality of switches, diodes, inductors and capacitors are connected in a circuit configuration to the input and output terminals. A control means is connected to the circuit for controlling the switching of a first, second, and third switch between an open and closed state.
    Type: Application
    Filed: March 17, 2011
    Publication date: September 22, 2011
    Applicant: ABB Research Ltd.
    Inventors: Leonardo-Augusto Serpa, Francisco Canales, Ngai-Man Ho, Antonio Coccia