Investigation of the Harmonic Optimization Approaches in the New Modular Multilevel Converters

Modular multilevel converter (MMC) is a new type of multilevel converter. Similar to cascaded multilevel converters, each arm consists of several submodules and each submodule includes one separate DC source in parallel. Based on the analysis of its structure and working mechanism, this paper presents two harmonic optimization techniques, known as optimized harmonic stepped-waveform (OHSW) technique and optimal minimization of THD (OMTHD) technique. Then, principles and algorithms of the two methods are discussed in detail. According to a conclusion of the sampling PWM control theory 'the same impulse and different pulse shapes added to the links with the inertia, the effect is basically the same', a new approach to accessing the initial values of Newton-Raphson is developed to solve the relevant nonlinear transcendental equations, which accelerates convergence of the roots. Finally, their advantages and disadvantages are clarified and compared via simulation experiment, verifying their effectiveness in MMC.

[1]  H. Akagi,et al.  PWM control and experiment of modular multilevel converters , 2008, 2008 IEEE Power Electronics Specialists Conference.

[2]  Zhong Du,et al.  Elimination of harmonics in a multilevel converter with nonequal DC sources , 2005, IEEE Transactions on Industry Applications.

[3]  Z. Du,et al.  Harmonic elimination for multilevel converter with programmed PWM method , 2004, Conference Record of the 2004 IEEE Industry Applications Conference, 2004. 39th IAS Annual Meeting..

[4]  L.M. Tolbert,et al.  Harmonic optimization of multilevel converters using genetic algorithms , 2004, IEEE Power Electronics Letters.

[5]  M. Glinka,et al.  Prototype of multiphase modular-multilevel-converter with 2 MW power rating and 17-level-output-voltage , 2004, 2004 IEEE 35th Annual Power Electronics Specialists Conference (IEEE Cat. No.04CH37551).

[6]  J. Chiasson,et al.  Elimination of harmonics in a multilevel converter using the theory of symmetric polynomials and resultants , 2003, 42nd IEEE International Conference on Decision and Control (IEEE Cat. No.03CH37475).

[7]  Leon M. Tolbert,et al.  Modulation index regulation of a multilevel inverter for static var compensation , 2003, 2003 IEEE Power Engineering Society General Meeting (IEEE Cat. No.03CH37491).

[8]  Fang Zheng Peng,et al.  Multilevel inverters: a survey of topologies, controls, and applications , 2002, IEEE Trans. Ind. Electron..

[9]  Leon M. Tolbert,et al.  Charge balance control schemes for cascade multilevel converter in hybrid electric vehicles , 2002, IEEE Trans. Ind. Electron..

[10]  P. Pillay,et al.  Multilevel selective harmonic elimination PWM technique in series-connected voltage inverters , 1998, Conference Record of 1998 IEEE Industry Applications Conference. Thirty-Third IAS Annual Meeting (Cat. No.98CH36242).

[11]  D. Retzmann,et al.  A new Multilevel Voltage-Sourced Converter Topology for HVDC Applications , 2008 .

[12]  Gevork B. Gharehpetian,et al.  Comparison of OMTHD and OHSW Harmonic Optimization Techniques in Multi-Level Inverter with Non-Equal DC Sources , 2008 .

[13]  Gevork B. Gharehpetian,et al.  A Complete Solution of Harmonics Elimination Problem in a Multi- Level Inverter with Unequal DC Sources , 2007 .

[14]  Neville R. Watson,et al.  Flexible power transmission--the HVDC options , 2007 .

[15]  R. Marquardt.  A new modular voltage source inverter topology , 2003 .