Method and system for detecting open phase

Abstract

The invention discloses a method and a system for detecting open phase. The method comprises the following steps: 1, according to acquired three phases of voltage values or current values Sa, Sb and Sc, the average three-phase value Savg and the maximum value Smax are calculated in real time; 2, filtering processing is carried out on the Smax and the Savg respectively, and an Smaxf1 and an Savgf1 are obtained; 3, conversion values Smaxf and Savgf for the Smaxf1 and the Savgf1 are calculated; 4, a voltage open phase detection judgment coefficient Kx is calculated; and 5, open phase judgment is carried out based on the Kx, if the Kx is larger than an open phase fault threshold Ks, happening of the open phase is judged, or otherwise, no open phase fault exists, and Ks is between 10% to 20%. The method is easy to implement, the calculation amount is small, and the method of the invention is a general defect detection method and is particularly applied to real-time open phase protection on a brushless doubly-fed machine.

Description

technical field [0001] The invention relates to a phase loss detection method and system, belonging to the technical field of power electronics and motor control. . Background technique [0002] There are many types of existing phase loss detection methods, which are generally implemented by hardware circuits, but it is not suitable to modify some mature circuits and add hardware circuits. [0003] In addition, when the brushless doubly-fed motor starts and runs, it also needs to perform phase loss detection; [0004] The brushless double-fed motor has a special structure, which is different from ordinary motors. There are two sets of stator windings at the stator end. Designed as low voltage, the low voltage winding is connected to the low voltage power grid through the controller, and the speed regulation of the motor can be realized by using the controller. Compared with ordinary AC motors, this motor has no carbon brushes and commutators, and can realize high-power hi...

AI Technical Summary

Problems solved by technology

[0008] In the brushless doubly-fed motor control system, the power side of the motor is connected to the high-voltage power grid through a power switch, and the voltage is generally above 6KV or 10KV. Due to the high voltage level, it is impossible to divide the voltage directly through the voltage dividing resistor, and the power does not pass through the rectification circuit. , so the existing phase loss detection and protection methods commonly used in general-purpose inverters are no longer effective, such as the phase loss detection method based on DC bus described in patent CN201010294959

In addition, due to the special structure of the two sets of windings of the brushless doubly-fed motor, its motor control algorithm is more complicated than that of conventional motors, and consumes a lot of DSP resources. CN200810135263 and patent CN201510438932 used multiple coordinate transformations) to occupy a large amount of DSP resources thereby affecting the normal execution of the control algorithm

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