Small Voltage Vectors Research Articles

Direct power control for three-level PWM rectifier based on hysteresis strategy

This paper presents a mathematical model of three-level voltage PWM rectifier, and derives a power control model from the theory of instantaneous power. In the vector-space, the influences on instantaneous power exercised by all the switching vectors are studied and illustrated separately, then a direct power control (DPC) scheme for three-level PWM rectifier which uses multistage band hysteresis comparator is proposed, and a novel switching table is designed. Meanwhile, the neutral-point voltage unbalance is inhibited by selecting the redundancy switching states of small voltage vectors. Simulation and experimental results show that the proposed strategy can not only stabilize the DC bus voltage but also realize the unity power factor operation and the balance of neutral-point voltage. Moreover, the proposed method can improve the performance of the three-level rectifier.

Problems of Exact Generation of Inverter Output Voltage

In this work, a new voltage space vector PWM method is developed. The problem of exact generation of small voltage vectors is discussed. Two methods for generating small inverter output voltage vectors are proposed. The influence of dead time is explained and its effect on the motor current is compensated. A squirrel cage induction motor with reduced supply voltage is used for testing the developed algorithm. Simulation and experimental results are carried out using fixed-point (DSP) and (FPGA). In addition, the practical realization of the proposed algorithm is discussed.