Three-phase Direct Matrix Converter Research Articles

Direct matrix converter based on improved quasi‐Z source network

This study proposes a three-phase direct matrix converter (DMC) topology based on an improved quasi-Z source (QZS) network. The proposed topology shows the following features: (i) Improve the voltage transmission ratio of traditional DMC. (ii) The voltage and current on the output side can be affected by the input side to the minimum, which minimises the harmonic content of the output current. (iii) Due to the existence of the improved QZS network, the three bidirectional switches of each output phase bridge arm are turned-on at the same time, which improves the reliability of the system. (iv) The improved QZS network has an input LC filter function, and no additional filter circuit is required on the input side. This study analyses the topological structure of the improved QZS-DMC and elaborates its boost working principle. On this basis, an improved dual space vector modulation strategy with shoot-through zero vector is proposed, which can effectively reduce the loss of the switch tube and improve the output waveform quality of the converter. Simulation and experimental results verify the proposed topology and strategy.

Modified PI controller with improved steady-state performance and comparison with PR controller on direct matrix converters

This paper proposes a modified proportional-integral (PI) controller and compares it with a proportional-resonant (PR) controller. These controllers are tested on a three-phase direct matrix converter (MC). The modified PI controller involves current feedforward together with space vector modulation (SVM) to control the MC output currents. This controller provides extra control flexibility in terms of the current error reduction, and it gives improved steady-state tracking performance. When the coefficient of current feedforward is equal to the load resistor (K = R), the steady-state error is effectively minimized even when regulating sinusoidal variables. The total harmonic distortion is also reduced. In order to comparatively evaluate the modified PI controller, a PR controller is designed and tested. Both the modified PI and PR controllers are implemented in the natural frame (abc) in a straightforward manner. This removes the coordinate transformations that are required in the stationary (αβ) and synchronous (dq) reference frame based control strategies. In addition, both controllers can handle the unbalanced conditions. The experimental and simulation results verify the feasibility and effectiveness of the proposed controllers.

Phase Current Reconstruction Using a Single Current Sensor of Three-Phase AC Motors Fed by SVM-Controlled Direct Matrix Converters

This paper presents a novel method for phase ac motor current reconstructing with a single current sensor in three-phase direct matrix converter (DMC) drive system using space vector modulation control technique. The main goal is to reduce the cost and to improve the reliability of drive systems that involve closed-loop control strategy. For this purpose, new structure and algorithm are developed which divide the zero-vector application time in two intervals and measure the phase currents using a new placement of the single Hall current sensor in DMC. These proposals constitute a good solution in the low-power-range DMC (below 15 kW), where reducing size and cost is the key objective. The simulation of the three-phase to three-phase DMC feeding an induction motor was done to demonstrate the advantages of the proposed system. Experiments were carried out owing to a DS1104 control board to check the validity of the proposed method.