Reliability Modeling and Evaluation of MMCs Under Different Redundancy Schemes

Abstract

Due to the demand for high reliability, modular multilevel converters (MMCs) are designed with redundant submodules. Redundant submodules can be integrated into the converter by employing different redundancy schemes: the conventional active scheme, the load-sharing active scheme, and the passive scheme. Different schemes have different impacts on the improvement of converter reliability. The contributions of this paper include that an analytical method is proposed to evaluate the reliability of MMCs under different redundancy schemes and the factors' influence on the converter reliability is analyzed to determine the proper redundancy scheme. Reliability models of MMCs under different redundancy schemes are built using Markov chains and the iteration method. Based on the proposed models, the effects of redundant schemes are evaluated in terms of the converter reliability. A case study is conducted to validate the feasibility and robustness of proposed models and to specify the conditions in the favor of each redundancy scheme. The benefits of sharing redundancy among arms are also explored from the reliability point of view. If insulated-gate bipolar transistors (IGBTs) and capacitors are dominant components in a submodule in terms of failure rates, the load-sharing active scheme performs better; otherwise, setting the redundant submodules in an idle state is more effective. It is also found that the number of required redundant submodules is greatly reduced by sharing redundancy among arms.

Availability Analysis of HVDC-VSC Systems: A Review

“…The percent switching frequency reduction per SM, proportional to the number of active redundant SMs, is equal to (k/(k + m))•100. It is worth noting that the lower mean voltage stress imposed to SMs in load sharing mode versus conventional mode qualitatively implies a reduced failure rate, as explained in [38]; therefore, this configuration is the most widely used.…”

“…Parametric models requiring all this information, which is not supplied by statistical records, are impossible to implement. The Basic Parametric Model (BPM) [38] introduces simplifying assumptions (above all, the symmetry assumption) that significantly reduce the total number of required parameters.…”

Seleção Da Tensão De Bloqueio Ótima De Igbts Para Inversores De Frequência Baseados Em Conversor Modular Multinível

“…Neste trabalho, são considerados as taxas de falha dos IGBTs, do capacitor e do sistema de controle do SM. Essa última inclui as taxas de falha dos circuitos de acionamentos dos IGBTs, sistema de comunicação e controlador dos SMs [30]. Assumindo que a taxa de falha de cada componente é independente, então λ SM = 2λ IGBT + λ capacitor + λ controle .…”

“…As especificações do CMM para cada projeto são exibidas na Tabela III. As taxas de falha consideradas para o estudo de confiabilidade são baseadas em dados estatísticos, conforme descrito em [30].…”

The full-state reliability model and evaluation technology of mechatronic product based on meta-action unit

“…So it is a powerful approach in reliability analysis, prediction, and assement of mechanical product. For example, Guo et al 24 built the reliability model using Markov chains and the recursive method to evaluate modular multilevel converters under different redundancy schemes. Garrido et al 25 presented a semi-analytical model by exploiting an absorbing Markov process.…”