Cascade H-bridge Multilevel Converter With Carrier Phase-shifted SPWM Technique And Its Application To Active Power Filter

Together with the continual develop of high power self-turn-off devices and intelligent high-speed microcontroller, high power electronic equipment is increasingly deeply studied and is more and more widely applied in large capacitance motor drive, power transmission and so on. On the realization of high power electronic equipment, an important problem is that the working frequency of high power devices is too low to apply excellent modulated technique such as PWM. In large-power equipment, the switching frequency of power electronics devices is such low that good control performance can't be obtained with a single converter. In order to overcome this problem, Carrier phase-shifted SPWM technique (CPS-SPWM) has been researched. On basis of it, its application to Active Power Filter in power system has been investigated in this paper.The operation principal of carrier phase-shifted SPWM (abbreviated as CPS-SPWM) has been analyzed in this paper. The key idea of this approach is the combination of multi-modular technique and SPWM technique. The high equivalent switching frequency can be obtained with low switching frequency devices. This technique improves the equivalent switching frequency through the counteract of lower order harmonics but not simply through processing the harmonic from lower order to higher order, so that it is with a perfect performance on harmonic feature.In reactive power compensation and active power filter, cascaded H-bridge multilevel converter with separated dc sources seems to be the most feasible topology for many reasons. The cascaded converter is constructed with a number of identical H-bridges inverters. This modular feature makes the cascaded converter very attractive. The cascaded converter topology not only simplifies hardware manufacturability, but also makes the entire system flexible in term of power capability. In addition, for the same power capability, the cascaded converter requires less number of main power components such as main valves and main diodes.In this paper, cascade H-bridge converter with CPS-SPWM technique has been proposed, which is the combination of cascade structure and CPS-SPWM technique. It is very promising not only in large power applications but also in medium or small power equipment.In applied system of shunt active power filter, the advantage of cascade multilevel converter is put forth sufficiently because of no need for active power on DC bus. Moreover, the excellent signal-transmitting feature of Carrier Phase Shifted PWM is also employed all right. In this paper, a shunt APF topology with cascade multilevel converter based on Carrier Phase Shifted PWM is presented. The systematic analysis of the harmonic and reactive power detection, AC side and DC side control, system parameter design and so on is done. The simulation study is carried out.imulation shows the APF system is of fast dynamic response and good compensation. Theory analysis and experimental system is feasible. .This paper presents a method of asymmetry sampling by TMS320LF2407 DSP. Harmonic of converter output wave is reduced greatly, but sampling data of asymmetry sampling is only twice than symmetry sampling. Experimentation on a Single-phase cascade H bridge five-level converter verifies the method, which is the combination of asymmetry sampling and CPS-SPWM technique. Experimental result shows the frequency spectrum of experimental wave and nature sample simulated wave are very close.For multi-modular converters and multilevel converters, the number of PWM generators provided by the IC is clearly not sufficient. In such occasion, a special purpose multiplex PWM generator is essential. Field programmable gate array (FPGA) along with its programming system is a new technique for VLSI. Under the support of FPGA development system software, designers can directly define and modify its logic function according to system demand. Special purpose multiplex PWM generator can be conveniently implemented by FPGA, which is very promising to multi-modular converters and multilevel converters.This pa...