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The existing approach for solving control systems in the Electromagnetics Transients Program is to insert one-time-step delays for breaking feedback loops when one or more nonlinear functions is encountered. Although this approach may remain acceptable for several well-behaved cases, it provides a nonsimultaneous solution for a nonlinear system. Fast varying components may create instabilities in such a solution and/or simply end up in a wrong operating region. In some cases, it imposes severe limitations on the integration time step for minimizing delays. This paper presents a new Jacobian matrix-based formulation for eliminating numerical delays in the solution of control system equations. Index Terms--Control systems, electromagnetic transient analysis, nonlinear systems, user modeling.

This paper presents a methodology for the central-processing unit/field-programmable gate-array (FPGA)-based real-time simulation of a two-terminal MMC-HVDC of up to 501 levels using a detailed equivalent model. The proposed modeling approach is validated using case studies of 101-level and 501-level multilevel modular converter setups. FPGA-based models are designed using low-latency custom-made floating-point operators. The FPGA model is entirely reconfigurable in terms of the number of submodules per arm, as well as circuit parameters on an individual submodule basis. Real-time simulation performance is demonstrated in single-rate and multirate simulation environments and under various operating conditions. Limitations to the detailed equivalent model are identified and discussed. [ABSTRACT FROM PUBLISHER]

A modular multilevel converter control system, based on converter energy storage, is proposed in this paper for two different control modes: active power and dc voltage. The proposed control system decouples the submodule (SM) capacitor voltages from the dc bus voltage. One of the practical applications is the management of active redundant SMs. A practical HVDC system with 401-level MMCs, including 10% redundancy in MMC SMs, is used for validating and demonstrating the advantages of the proposed control system. This paper also presents a novel capacitor voltage balancing control based on \max–\min functions. It is used to drastically reduce the number of switchings for each SM and enhances computational efficiency. [ABSTRACT FROM AUTHOR]

Modular multilevel converters (MMCs) may contain numerous insulated-gate bipolar transistors. The modeling of such converters for electromagnetic transient-type (EMT-type) simulations is complex. Detailed models used in MMC-HVDC simulations may require very large computing times. Simplified and averaged models have been proposed in the past to overcome this problem. In this paper, existing averaged and simplified models are improved in order to increase their range of applications. The models are compared and analyzed for different transient events on an MMC-HVDC system. [ABSTRACT FROM AUTHOR]