Sliding Mode Control of Three-Phase Two-Level Converters

Abstract

AbstractAccording to the number of modulation levels, power converters can be divided into two-level and multi-level converters. Power converters with AC side include single-phase and three-phase converters, and grid-connected power converters are three-phase converters. Although there are various circuit topologies for converters, the three-phase two-level topology is most common in the industrial field due to its topological simplicity and full power ranage controllablity, as well as high reliability, high efficiency and high power capacity [1]. This chapter investigates the grid-connected three-phase two-level power converter, and adopts the disturbance observer based sliding mode control strategy to carry out the current tracking and voltage regulation of the converter. The voltage regulation loop adopts a super twisting sliding mode controller, which is compensated by a disturbance observer. The current control loop is controlled in synchronous reference frame (SRF), and two super twisting sliding mode controllers are used to track the d-axis and q-axis currents. Four different disturbance observers are designed for comparison, including linear observer, second-order sliding mode observer, linear extended state observer and nonlinear extended observer. Then through simulation, the performance of the observers is compared according to the transient response of the DC-link voltage. In order to ensure a fair comparison, the parameters of the observers are adjusted to make the converter have almost the same current distortion level and DC-link voltage steady-state error.