Abstract
In recent years, modular multilevel converters (MMC) are becoming popular in the distribution and transmission of electrical systems. The multilevel converter suffers from circulating current within the converter that increases the conduction loss of switches and increases the thermal stress on the capacitors and switches’ IGBTs. One of the main solutions to control the circulating current is to keep the capacitor voltage balanced in the MMC. In this paper, a new hybrid control algorithm for the cascaded modular multilevel converter is presented. The Harris hawk’s optimization (HHO) and Atom search optimization (ASO) are used to optimally design the controller of the hybrid MMC. The proposed structure of modular multilevel inverters allows effective operation, a low level of harmonic distortion in the absence of output voltage filters, a low switching frequency, and excellent flexibility to achieve the requirements of any voltage level. The effectiveness of the proposed controller and the multilevel converter has been verified through testing with the application of the MMC-static synchronous compensator (STATCOM). The stability of the voltage capacitors was monitored with balanced and unbalanced loads on the studied network.
Highlights
With the increased popularity and application of power electronic devices in modern industries, some large electrical loads such as from an AC traction system, electric furnaces and modern technologies based on high-tech microprocessors in renewable energy applications cause increasing power quality (PQ) problems [1,2]
The simulation results have been obtained to validate the effectiveness of the proposed optimization techniques in determining the optimal values of the capacitance and the parameters of the DC voltage regulator
To validate the accuracy of the those obtained from the results, these values have been applied to the system under study under the integration of nonlinear loads and the condition of three-phase imbalance
Summary
With the increased popularity and application of power electronic devices in modern industries, some large electrical loads such as from an AC traction system (single-phase), electric furnaces and modern technologies based on high-tech microprocessors in renewable energy applications cause increasing power quality (PQ) problems [1,2]. Power quality problems appear in electric utility as increased harmonic distortions, phase imbalances and low power factors. Electric devices based on power electronics present themselves as non-linear loads, which are characterized as sources of harmonics in the power system. The harmonic currents cause an increase in the RMS value of the current and let the neutral current make circulations in the electric distribution system. The capacity of the distribution system and power losses are affected by the presence of harmonics [2,3].
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