Research On The Technology Of Variable Speed Constant Frequency

The technology of Variable Speed Constant Frequency (VSCF) is commonly used on megawatt wind energy converters. VSCF realization is the basic function of wind energy converter's electrical control unit. However, many papers' discuss on this technology is not definite. What on earth is the relationship between VSCF and the machine control strategies of Vector Control or Direct Torque Control? That is the point concerned in this paper. This paper takes the ABB drive unit mounted on the 1.5MW wind energy converter of Shenyang University of Technology as the research object. Through practicality research, deduction and simulation model building, demonstrate the correctness of theory analysis.Two close loop control is adopted in rotor side converter in ABB drive unit: The outer loop is rotation speed loop; the inner loop is torque loop which adopts direct torque control strategy. This paper only talks about the VSCF realization, so overlook the section of the stator side converter control. Take the parameter of rotation speed as the input signal of doubly fed generator and build the simulation model, on account of which overlook the rotation speed loop in control scheme.Through research on ABB drive unit control scheme and the direct torque control principle of asynchronous motor, it deduces the principle of direct torque control of doubly fed generator to realize VSCF, draws the control scheme, and explains the realization of every function block in this paper. On basis of that, draw the essential of the direct torque control of doubly fed generator to realize VSCF: through putting voltage vector on the rotor flux, make the rotor flux rotates at the synchronous speed continuously, which realizes that the frequency of stator side output current is constant.On account of theory analysis, build the simulation model of the VSCF section in ABB drive unit using MATLAB7. Through the analysis of simulation wave, the frequency of the stator side output current of doubly fed generator is constant when the rotation speed varies. Therefore, validates the correctness of theory analysis on the VSCF section of ABB drive unit.At last, according to the research content in the paper, it puts forward the research shortage and new research direction in the conclusion.