Current Decoupling Control for the Three-level PWM Rectifier with a Low Switching Frequency

Abstract

-Three-level PWM rectifiers applied in medium voltage applications usually operate at low switching frequency to keep the dynamic losses under permitted level. However, low switching frequency brings a heavy cross-coupling between the current components i d and i q with a poor dynamic system performance and a harmonic distortion in the grid-connecting current. To overcome these problems, a mathematical model based on complex variables of the three-level voltage source PWM rectifier is firstly established, and the reasons of above issues resulted from low switching frequency have been analyzed using modern control theory. Then, a novel control strategy suitable for the current decoupling control based on the complex variables for i d and i q is designed here. The comparisons between this kind of control strategy and the normal PI method have been carried out. MATLAB and experimental results are given in detail.

Stator current harmonic elimination control for the high‐power synchronous motors with online implementation

“…Lower loss operation has been one of the targets of the high‐power industrial areas, and in recent years, large numbers of research were carried out to reduce the switch losses and to improve the converter power capability, such as low switching frequency control [3, 4], multilevel control [5, 6], predictive current control [7, 8], and complex vector current control [9]. Among these aforementioned methods, the low switching frequency control was generally regarded as a practical method, however, it could result in a severe harmonic distortion in the stator current, also lead to a cross‐coupling and longer delay of the pulse width modulation (PWM), which deteriorate the current control performance.…”

The undamped control for PWM rectifier based on LCL filter

“…In PWM rectifier, current control with fixed switching frequency makes the carrier frequency of trigger signal to be fixed, and the deviation of current acts as PWM control method of modulated wave signal [12][13][14]. The frequency of switching devices is the carrier frequency, so the control strategy with fixed switching frequency can reduce the value of filter inductance.…”