An Optimization Algorithm of Capacitor Voltage Balancing in Modular Multilevel Converter

Zhang, Xinyue; Kang, Xiaoning; Guo, Mei; Zhang, Yagang; Xu, Yini

doi:10.1109/powercon.2018.8602343

Cited by 2 publications

(2 citation statements)

References 13 publications

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“…The quality of MMC output voltage waveform in literature [15][16][17] is closely related to the selection of retention factor, Modulation index and MPC input value, but the selection rules of optimal value are not described. The literature 18,19 introduced improved quick sort algorithm and improved bucket sort algorithm for capacitance voltage equalization control, meanwhile the sub-module capacitance voltage sequence is sorted respectively in blocks and buckets, which reduces the amount of sorting to improve the computational efficiency, but the system still has excessive switching frequency.…”

Section: Introductionmentioning

confidence: 99%

A enhanced control strategy for capacitance voltage equalization in modular multilevel converter

Ding,

Zhang,

Cheng

et al. 2023

Measurement and Control

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In searching for the optimal control strategy of sub-module capacitance voltage equalization of Modular Multilevel Converter (MMC), the most important issue is how to address the significant increase in computing time of the controller, switching frequency of the sub-module, device switching loss and MMC fault rate led by the increase in the number of sub-modules of the upper/lower bridge arm of the MMC. Therefore, this paper proposes a control strategy based on the retaining factor method + improved quick sort, namely, an improved quick sort algorithm is used to sort the sub-module capacitance voltages to reduce the amount of computation of the MMC controller; at the same time, a retaining factor is introduced to participate in the improved quick sort to significantly reduce the switching frequency of the sub-module. MMC of large ship grid-connected photovoltaic power system is taken as a research object in this paper, a 31-level MMC model is built in Matlab/Simulink. Simulation results verify that the improved quick sort has a good rapidity compared to the algorithms of bubble sort, quick sort, bidirectional bubble sort, and improved merge sort, that the retention factor method has a good frequency reduction effect, and that the proposed retention factor + improved quick sort can provide a good performance compared to improved quick sort and retention factor + improved merge sort under conditions of the normal operation and introducing disturbance.

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Section: Introductionmentioning

confidence: 99%

A enhanced control strategy for capacitance voltage equalization in modular multilevel converter

Ding,

Zhang,

Cheng

et al. 2023

Measurement and Control

View full text Add to dashboard Cite

show abstract

“…The proposed voltage actual value approximation modulation strategy can effectively suppress the circulation, but this method is not suitable for the case of a small number of sub-modules. In [16], the frequency division and equalization control is proposed, so that the sorting frequency is much smaller than the control frequency, and the sorting frequency calculation process is derived, which can reduce the switching frequency and the computational burden. Literature [17] analyzes the necessary and sufficient conditions for the stability of the MMC system under open-loop control, and achieves voltage equalization by detecting the voltage of each bridge arm and injecting zero-sequence voltage.…”

Section: Introductionmentioning

confidence: 99%

Archives of Electrical Engineering

Jin¹,

Luo²,

Yang³

et al. 2019

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In order to solve the problem of traditional carrier phase-shift modulation with multiple ratios or PI controllers and cumbersome tuning parameters, this paper uses improved carrier phase-shift modulation. The total turn-on number of sub-modules each bridge arm is determined by comparing the sinusoidal modulated wave with the triangular carrier, and then the control signal is generated according to the capacitance voltage sorting result and the bridge arm current polarity. However, this modulation method uses a sorting method that causes the insulated gate bipolar transistor (IGBT) have an excessively high switching frequency. Therefore, a sorting trigger condition that can effectively reduce the switching frequency is used. The method determines whether to reorder based on the error between the voltage average and the actual value. For the circulation problem, the double-frequency negative sequence component is extracted by rotating coordinate transformation, and it is suppressed by PI control. A 21-level MMC model was built in MATLAB/simulink to analyze the sub-module capacitor voltage fluctuation, output current, voltage distortion rate and bridge arm circulation. It is verified that the modulation method can combine the sorting algorithm and circulation suppression method at the same time, and has better voltage equalization and circulation suppression effects.

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An Optimization Algorithm of Capacitor Voltage Balancing in Modular Multilevel Converter

Cited by 2 publications

References 13 publications

A enhanced control strategy for capacitance voltage equalization in modular multilevel converter

A enhanced control strategy for capacitance voltage equalization in modular multilevel converter

Archives of Electrical Engineering

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