# Zhenhuan Yuan, Shanghai CN

## Zhenhuan Yuan, Shanghai CN

Patent application number | Description | Published |
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20110102012 | PARAMETER ESTIMATION SYSTEM AND METHOD FOR AN INDUCTION MOTOR - A method of estimating stator resistance of an induction motor is provided. The method includes applying voltage pulses through two phase paths of the motor for a plurality of electrical cycles to inject current in the motor, wherein the voltage pulses are applied until rotor flux of the motor is substantially stabilized and measuring stator voltage and stator current in response to the applied voltage pulses for each of the plurality of electrical cycles. The method also includes calculating the stator resistance based upon the measured stator voltages and the stator currents. | 05-05-2011 |

20110295437 | WIND POWER CONVERTER SYSTEM WITH GRID SIDE REACTIVE POWER CONTROL - The present techniques include methods and systems for operating a wind power system to maintain a lifespan of the rotor side converter. In some embodiments, the current of the rotor side converter may be minimized to reduce the stress and/or junction temperature variation in the switching transistors and bond wires of the converter. More specifically, embodiments involve using a minimal current in the rotor side converter based on the rotor side and grid side reactive powers. If the grid side reactive power is greater than a maximum grid side reactive power, the grid side reactive power may be reduced. Further, if the total reactive power does not meet the grid reactive power requirements, the minimal current in the rotor side converter may be adjusted such that the system may sufficiently power the grid. | 12-01-2011 |

20110309875 | CONVERTER LIFETIME IMPROVEMENT METHOD FOR DOUBLY FED INDUCTION GENERATOR - The present techniques include methods and systems for operating converter to maintain a lifespan of the converter. In some embodiments, the operating frequency of the converter may be increased such that stress may be reduced on the bond wires of the converter. More specifically, embodiments involve calculating the aging parameters for certain operating conditions of the converter operating in a maximum power point tracking (MPPT) mode and determining whether the MPPT operation results in aging the converter to a point which reduces the converter lifespan below a desired lifespan. If the MPPT operation reduces the converter lifespan below the desired lifespan, the frequency of the converter may be increased such that the converter may be controlled to operate at a percentage of MPPT. Thus, in some embodiments, power output may be optimized with respect to maintaining a desired lifespan of the converter. | 12-22-2011 |

20120262129 | DOUBLE FED INDUCTION GENERATOR CONVERTER AND METHOD FOR SUPPRESSING TRANSIENT IN DEACTIVATION OF CROWBAR CIRCUIT FOR GRID FAULT RIDETHROUGH - A double fed induction generator (DFIG) system and controller are presented in which the rotor side converter is preloaded with one or more initial values for resuming regulated operation to counteract transients upon deactivation of the crowbar protection circuit to provide grid fault ride through. | 10-18-2012 |

20130249501 | DOUBLE FED INDUCTION GENERATOR (DFIG) CONVERTER AND METHOD FOR IMPROVED GRID FAULT RIDETHROUGH - A double fed induction generator (DFIG) converter method are presented in which rotor side current spikes are attenuated using series-connected damping resistance in response to grid fault occurrences or grid fault clearances. | 09-26-2013 |

20140253055 | CONVERTER LIFETIME IMPROVEMENT METHOD FOR DOUBLY FED INDUCTION GENERATOR - The present techniques include methods and systems for operating converter to maintain a lifespan of the converter. In some embodiments, the operating frequency of the converter may be increased such that stress may be reduced on the bond wires of the converter. More specifically, embodiments involve calculating the aging parameters for certain operating conditions of the converter operating in a maximum power point tracking (MPPT) mode and determining whether the MPPT operation results in aging the converter to a point which reduces the converter lifespan below a desired lifespan. If the MPPT operation reduces the converter lifespan below the desired lifespan, the frequency of the converter may be increased such that the converter may be controlled to operate at a percentage of MPPT. Thus, in some embodiments, power output may be optimized with respect to maintaining a desired lifespan of the converter. | 09-11-2014 |

20140265596 | METHOD AND APPARATUS FOR ISLANDING DETECTION FOR GRID TIE CONVERTERS - Methods and apparatus are presented for unintentional islanding detection for grid tie converters in which the phase angle disturbance is introduced by modification of grid side converter switching control signals and a mismatch of reactive power between generation and the grid load is formed upon the occurrence of unintentional islanding, where the applied phase disturbance is determined according to two pre-defined curves to form an equivalent positive feedback at different frequencies to prevent the converter from forming an island at a new stable frequency after the grid is disconnected. | 09-18-2014 |

20140285230 | PARAMETER ESTIMATION SYSTEM AND METHOD FOR AN INDUCTION MOTOR - A method of estimating stator resistance of an induction motor is provided. The method includes applying voltage pulses through two phase paths of the motor for a plurality of electrical cycles to inject current in the motor, wherein the voltage pulses are applied until rotor flux of the motor is substantially stabilized and measuring stator voltage and stator current in response to the applied voltage pulses for each of the plurality of electrical cycles. The method also includes calculating the stator resistance based upon the measured stator voltages and the stator currents. | 09-25-2014 |