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This paper presents a new method to measure the voltage across the submodule (SM) capacitors in a modular multilevel converter (MMC). The proposed technique requires only one voltage sensor per arm. This reduces the number of sensors required compared with conventional sensor-based methods. Therefore, the cost and complexity of the system are reduced, which in turn improves the converter’s overall reliability. The proposed method employs an exponentially weighted recursive least square algorithm to estimate the SM capacitor voltages through the measured total arm voltage and the switching patterns of each SM. There is thus no need for extra sensors to measure these control signals as they are directly provided from the controller. The robustness of the proposed method is confirmed via introducing deviations for the capacitance values, dynamic load changes, dc voltage change, and startup transient condition. Simulation and experimentally validated results based on a single-phase MMC show the effectiveness of the proposed method in both, steady-state and dynamic operations.

This paper presents a new voltage estimation method for the submodule (SM) capacitor in a modular multilevel converter (MMC). The proposed method employs a Kalman filter algorithm to estimate the SM voltages of the converter. Compared with sensor-based methods, this scheme requires only one voltage sensor to achieve the voltage-balancing of the converter. This sensor is connected to the total arm voltage; the proposed algorithm also requires the switching patterns of each upper SM switch, which are provided by the controller used without the need for extra sensors. The substantial reduction in the number of voltage sensors improves the system reliability and decreases its cost and complexity. Extensive simulation and experimental analyses carried out to validate the proposed estimation scheme under different conditions include steady-state analyses, the effect of variations in capacitance and inductance, the impact of low carrier and effective switching frequency on the accuracy of the estimation, step changes to the load, and range changes in dc voltage. The results obtained are experimentally verified using a single-phase MMC.

Different schemes of modified conventional sorting algorithms with low complexity are proposed in order to balance the voltages of submodule (SM) capacitors for the modular multilevel converter (MMC). Two different procedures are investigated in this study. The main idea is to achieve voltage balance within the MMC arms with fewer current sensors. The two different methods are examined under different operating conditions; for instance, with a sudden change in the DC-source or when different load values are applied. The advantage of such sensor-less control methods is to simplify hardware communications in general. Moreover, the reliability of the MMC is also improved. Simulation analyses of a single-phase four-level MMC are conducted to show the effectiveness of the proposed methods.

This paper employs a Kalman filter (KF) algorithm to estimate the capacitance of submodule (SM) capacitors in modular multilevel converters (MMCs). The proposed method can be used in the health condition monitoring technique of the capacitors. This proposed scheme estimates the capacitance of each individual capacitor from data of arm current and the corresponding voltage across the targeted capacitor. The arm current is used to calculate the capacitor current from the upper state of the SM switch. The proposed method has shown very good performance under normal operating conditions. The effectiveness of the proposed technique is validated via a MATLAB simulation analysis of a single-phase four-level MMC.

This paper proposes an adaptive observer based on Kalman filter (KF) to estimate the capacitor voltages of Modular Multilevel Converters (MMC). The proposed method offers a considerable reduction in sensors count, hence the system cost and also increases the converter reliability. The paper also investigates several approaches linked to MMC; voltage balancing control issue, the effect of circulating current on the arm capacitors voltages in addition to sensors cost issues. The effectiveness of the proposed method is validated through simulation studies of a single-phase five-level MMC using MATLAB/SIMULINK.