Optimization And Application Study On Modulation Strategy Of Matrix Converter

Power electronics have become a key technology in flexible DC transmission, gird integration of renewable energy generation and power quality management. Development of power device has contributed to the further research of new topology of circuits and its corresponding control algorithm, among them, the AC-AC matrix converter without DC link has become an important research direction for its simple topology, high power density, adjustable input power factor and four quadrant operation. As a typical application of non-constant-amplitude PWM, this paper has conducted the following research:The indirect space vector modulation approach of matrix converters (MC) can be synthesized by the fictitious rectifier and fictitious inverter. In traditional fictitious rectifier and fictitious inverter, complex coordinate transformation is required to acquire relevant control variable, and sectors judgment and quantity of trigonometric operations are involved in the modulation process. In this paper, trigonometric function analysis is applied to detect the signal relations directly, moreover, a novel sector judging and duty cycle calculation method in fictitious rectifier and fictitious inverter is proposed. Comparing with the traditional ISVM, this method can omits the α-β coordinate and polar coordinate transformation, thus, greatly simplify the calculation process.Further research found that the combination algorithm of duty cycle in indirect space vector modulation is cumbersome and its operating conditions are complex. Based on the simplified SVPWM algorithm in the fictitious rectifier side, a no-sector space vector pulse width modulation was proposed in the fictitious inverter side, in which a non-orthogonal K-L120°coordinate system was established. In this way, the switch duty cycle of the three-phase bridge arm could be solved directly without judging sectors. By combining the novel duty cycle mode and traditional fictitious rectifier duty cycle section,36operation conditions in traditional algorithm are reduced to the number of18, therefore, greatly simplified the program of function S and enhanced the real-time performance.After analyzing the consistency of K-L120°coordinate system and traditional a-β90°coordinate system in sector partition and duty cycle calculation, it is found that in traditional algorithms, complex trigonometric function analysis exists in the transformation from α-β90°coordinates to60°sector coordinate, thus the sector partition and duty cycle calculation are complex and lack of physical meaning. Based on the K-L120°coordinate system and math derivation, a easy-complemented SVPWM algorithm with a clear physical meaning is put forward.In earlier stages, a non real-time simulation model of matrix converter is established in MATLAB, which verifies the novel modulation algorithm. Considering the complexity of Process and protection in matrix converter, RTDS (real time digital system) and physical controller are adopted to proceed a close-loop experiment in the middle of research. In the end, back-to-back experiment platform is established using dual DSP digital control system, which verifies the novel modulation strategy of matrix converter in fictitious inverter side. The feasibility and validity of the new approach is verified by both simulation and experimental results.