Excitation structure and alternating-current and direct-current excitation control method for frequency-variable alternating-current starting power generation system

Abstract

The invention discloses an excitation structure and an alternating-current and direct-current excitation control method for a frequency-variable alternating-current starting power generation system. The excitation structure consists of an open circuit-type stator three-phase winding and a three-phase bridge-type converter, wherein the two ends of the three-phase bridge-type converter are connected. The method comprises the following steps of: starting an initializing process; coordinately controlling the output vector of each converter; selecting a proper comprehensive voltage vector; generating a required three-phase alternating-current excitation voltage in the three-phase winding so that a magnetizing exciter works in a rated output state to provide enough excitation current for the starting and the operation of a main power generator; when the rotating speed of a motor reaches an excitation switching point, switching from a three-phase alternating-current excitation mode to direct-current excitation according to a rotating speed feedback signal, wherein the structure of the winding of the magnetizing exciter does not need to be changed by an external switch in the switching process; and making the three-phase alternating-current winding equivalent to a direct-current serial structure by directly controlling each phase of winding current respectively by utilizing the bridge arms of two converters. Therefore, a direct-current excitation function is realized.

Description

technical field [0001] The invention relates to a winding structure of an exciter in a variable frequency AC starter generator, a converter design and control technology, and belongs to the field of motor control. Background technique [0002] With the continuous development of aviation power supply technology, the power supply system of large civil aircraft is gradually transitioning from the existing constant speed and constant frequency, variable speed and constant speed to the variable frequency AC power supply system. Power supply can effectively improve the capacity and efficiency of the power generation system, and can directly use the power distribution components, auxiliary power supply, APU generator and emergency power supply in the constant frequency 400Hz power supply system, and can be compatible with various components in the existing constant frequency power supply system load, so the variable frequency power supply system is becoming the first choice for lar...

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Problems solved by technology

[0004] Due to the existence of the rotating rectifier in the three-stage brushless synchronous motor, when it is used as a starter in a variable frequency AC power supply system, that is, it is running in an electric state and needs to start from a standstill, but at this time the exciter rotor is in a static state and cannot provide The excitation current causes the main generator to be difficult to excite and there is a problem that it cannot be started

The US patent US7687928B2 protected by Smiths Aerospace in 2010 proposes to use two sets of field windings, one set of three-phase field windings is used for the initial operation of starting, and one set of DC field windings is used for the later stage of the starting stage and the stage of power generation and voltage regulation. The DC excitation windings are respectively set in the exciter. Usually, after the AC excitation is completed, the AC excitation windings are no longer used, which greatly reduces the utilization rate of the exciter windings.

In the process of connecting the three-phase AC excitation windings in series to DC windings in the above patent solution, due to the delay characteristics of the switching switches, the output of the stator winding of the exciter will be affected, so that the excitation current of the main generator will change. Affects the output torque, causing problems with starting

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