A Novel Space Vector modulation Scheme and Direct Torque Control for Four-switch BLDCM Using Flux Observer

Abstract

-The main purpose of this paper is to describe a DTC (direct torque control) method for four-switch brushless dc motor (BLDCM) drive. In the method, a novel voltage space vector modulation scheme, an optimal switching table, and a flux observation method are proposed. Eight voltage vectors are summarized, which are selected to control BLDCM in SVPWM pattern, and an optimal switching table is proposed to improve the torque distortion caused by midpoint current of the split capacitors. Unlike conventional flux observers, this observer does not require speed adaptation and is not susceptible to speed estimation errors, especially, at low speed. Global asymptotic stability of the flux observer is guaranteed by the Lyapunov stability analysis. DC-offset effects are mitigated by introducing a PI component in the observer gains. This method alleviates the undesired current and torque distortion which is caused by uncontrollable phase. The correctness and feasibility of the method are proved by simulation and experimental results.

Four-Switch Three-Phase PMSM Converter with Output Voltage Balance and DC-Link Voltage Offset Suppression

“…This strategy is of interest to the authors of [3][4][5][6][7][8][9][10][11]. The final power inverter structure is shown in Figure 1.…”

“…It was first proposed by [1] for the purpose of minimizing the components' cost; one motor terminal is connected to the centre tap of the DC-link capacitors so that it utilizes two less Insulated Gate Bipolar Transistors (IGBT) [2]. This converter was applied to many fields such as Brushless direct-current (BLDC) motor drives [3,4] and unified power quality conditioners [5]. In addition, the 4S3P power topology could be achieved from standard three-phase topology, which made it very attractive in fault-tolerant control to solve the open/short circuit fault of standard inverter IGBTs [6,7].…”