Optimal Six Vector Switching Pattern in Matrix Converters for Reducing Harmonics and Switching Loss

This paper analyses harmonic distortion caused by the narrow pulse problem in matrix converters,and presents an improved switching pattern that is based on the basic five vector switching pattern.With limited switching frequencies,the improved pattern solves the narrow pulse problem by applying an additional zero vector and adjusting the sequence of the four active vectors at the same time to minimize the switching times.Simulation results show that in the six vector switching pattern,a)the low-frequency harmonics caused by the narrow pulse problem are greatly reduced;b)the average switching frequency is reduced compared with the five vector pattern;c)the sampling frequency harmonics are apparently attenuated though a little 1/2 and 3/2 sampling frequency harmonics are produced;d)the THD of the output current is improved to the same level of the three zero vector switching pattern(TZVSP);e)the proposed switching pattern has benefits in both normal and unbalance input voltage conditions.Experimental results on a matrix converter platform,verify the benefits of the six vector switching pattern.Faster dynamic,lower harmonics and lower losses can be achieved by using the proposed six vector switching pattern.

In-plane Uniaxial Anisotropy and Magnetization Reversal Mechanism of FeCo Films by Strip Pattern

Strip-like Fe Co films were patterned by a traditional lithograph process from intrinsically isotropic continuous Fe Co films. The strip-patterned Fe Co film shows a strong in-plane uniaxial magnetic anisotropy with easy axis along the length direction of the strip. The angular dependences of remanence ratio, switching field, and coercivity indicate that the magnetization reversal mechanism of the strip-patterned Fe Co film is coherent rotation and domain wall depinning when the applied field is near the hard axis and easy axis, respectively. The consistency of the experimental hysteresis loops of the strip-patterned Fe Co film and calculated hysteresis loops with a simple in-plane uniaxial anisotropy model indicates that the strip-patterned Fe Co film behaves as a single domain. The absence of the domain wall and the strong in-plane anisotropy field make the strip-patterned Fe Co films have much potential for high-frequency application.