Zhejiang University

Chushan Li

Wuhua Li

Xiangning He

Huan Yang

Wenxi Yao

Youtong Fang

Min Chen

Jing Sheng

Yuxiang Wang

Ye Yan

Chengmin Li

Qinghui Huang

Huiqiang Yan

Xin Xiang

Xiaowei Gu

Saizhen Chen

Heya Yang

Lin Zhu

Haoze Luo

Shengdao Ren

A method for a direct current (DC) islanding detection based on positive feedback of a bus voltage at a specific frequency, essentially including three steps: extraction of a specific frequency component of the bus voltage, injection of a disturbance component of the specific frequency, and determination of DC islanding. The extraction of the specific frequency component of the bus voltage and the injection of the disturbance component of the specific frequency constitute a positive feedback mechanism in a power management unit control loop. In a grid-connected mode of a DC grid, the positive feedback mechanism fails due to a control action of a voltage management unit on a bus, and the bus voltage remains stable. In an islanding mode of the DC grid, under an action of the positive feedback mechanism, the power management unit allows the bus voltage to generate a self-excited oscillation at the specific frequency.

Method for DC islanding detection based on positive feedback of bus voltage at specific frequency

A resonance control method for differentiated phase correction under asymmetric positive and negative bilateral frequency domains includes a differentiated phase correction resonance control link with an independent phase correction angle at each resonance point, a decoupling link and a delay compensation link. As a high power converter has the characteristic of asymmetric positive and negative bilateral frequency domains under resonance control with decoupling, stability margin of a control link is enhanced while a negative-sequence current suppression capability is realized by means of differentiated phase correction at positive and negative resonance poles.

Resonance control method for differentiated phase correction

The present invention discloses a high step-down modular DC power supply, belonging to the field of power electronics technology, and the high step-down modular DC power supply includes an upper modular cascade circuit string, a lower modular cascade circuit string, a load, and an input source, where the upper modular cascade circuit string includes i upper sub-module circuits, and the lower modular cascade circuit string includes j lower sub-module circuits. A combination manner of module circuits includes: upper module string cascading, lower module string cascading, and hybrid cascading of the upper module string and the lower module string. The power supply is formed to be a high voltage step-down ratio power supply with high voltage direct current input and low voltage direct current output through modular cascading. No synchronous control signal is needed between sub-modules of the power supply, voltage equalization of power supply input series capacitors may be realized without a central controller, and therefore, a control strategy of each sub-module is very simple. The power supply may be flexibly expanded in voltage and power classes, and is suitable for auxiliary power supply applications in medium voltage or high voltage DC input occasions.

High step-down modular DC power supply

A gate voltage magnitude compensation equalization method and circuit for series operation of power switch transistors are provided. A dynamic voltage equalization of series-connected power switch transistors is implemented by using sampling principles where voltages of the power switch transistors are controlled by gate voltage magnitude and unbalanced voltage differentials are converted into unbalanced current differentials of buffer currents. The gate voltage magnitude compensation equalization method and circuit relates to differential control and works in a dynamic voltage change process of the series-connected power switch transistors, without having a negative effect on operation of the power switch transistors under normal operating conditions. Only adopting passive devices, the gate voltage magnitude compensation equalization circuit has a simple structure, is easy to integrate on a device drive board, implements response tracking of unbalanced voltage and voltage equalization of the series-connected power switch transistors, and improve speedability and stability of voltage equalization control.

Gate voltage magnitude compensation equalization method and circuit for series operation of power switch transistors

Growing community of inventors

Hangzhou, China

Chushan Li