Abstract:The AC and DC power system structures need to be modernized to meet consumer demands. DC microgrids are suitably admired due to their high efficiency, consistency, reliability, and load sharing performance, when interconnected to DC renewable and storage sources. The main control objective for any DC microgrid is providing proper load-power balancing based on the Distributed Generator (DG) sources. Due to the intermittent nature of renewable energy sources, batteries play an important role in load-power balancing in a DC microgrid. The existing energy management strategy may be able to meet the load demand. However, that technique is not suitable forrural communities' power system structure. This research offers an energy management strategy (EMS) for a DC microgrid to supply power to rural communities with solar, wind, fuel cell, and batteries as input sources. The proposed EMS performs the load-power balancing between each source (renewable and storage) in a DC microgrid for dynamic load variation. Here, the EMS handles two battery sources (one is used to deliver power to the priority load, and the other is utilized in the common DC bus) to meet the required demand. The proposed EMS is capable of handling load-power balancing using renewable energy sources with less consumption of non-conventional energy sources (such as a diesel generator). The performance of the system is analyzed based on different operating conditions of the input sources. The MATLAB/Simulink simulation model for the proposed DC microgrid with their EMS control system is developed and investigated, and their results are tabulated under different input and load conditions. The proposed EMS is verified through a laboratory real-time DC microgrid experimental setup, and the results are discussed.

In this paper, an enhanced voltage sorting algorithm is proposed for balancing each sub module capacitor voltage in modular multilevel converter (MMC). However, the submodule (SM) voltage strategy becomes more complex when it increases to a number of levels, which eventually increases voltage ripples and circulating current. In order to overcome this problem, an enhanced voltage sorting algorithm is proposed, which implies an enhanced control logic function for capacitor voltage balancing of the converter. The switching pattern of each SM floating capacitor is determined based on the modulating signal methodology, which is then compared with the hybrid state condition using arm current direction in the MMC. Additionally, the generated hybrid signals are once again compared with the dynamic implicit number by conjoining the switching logic state variables. Due to this comparison of logic function, the capacitor voltage is balanced properly and reduces the capacitor ripple voltage to a permissible limit compared to the conventional method. Hence, compared to other balancing techniques, the circulating current is reduced by using conventional control techniques. The desired pulse signals for the power devices are obtained based on the multi carrier pulse width modulation techniques. The superior performance of the proposed algorithm is tested using MATLAB/Simulink software and real time laboratory hardware setup for different load conditions. Apart from this, the effective performance of the proposed method has been validated in the HVDC transmission system.

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Due to the modular structure and voltage scalable features, the Modular Multilevel Converter (MMC) has become an alternative converter for high and medium voltage-based transmission systems. Apart from this, MMC has edible features in controlling the real and reactive power for a high-voltage transmission system compared to the conventional converter. However, some of the technical challenges such as control complexity when subjected to more voltage levels, capacitor voltage balancing issues, increase in capacitor voltage ripples, DC fault handling, and circulating current affect the performance of MMC in various applications. In this paper, an adaptive balancing strategy is proposed for capacitor voltage balancing of each cell connected in the MMC. This approach balances the floating capacitor in a simplified manner and henceforth reduces the capacitor voltage ripples to the permissible limit. In addition, the circulating current present in the MMC circuit will be suppressed in comparison to the conventional method. The proposed strategy is investigated under various operating conditions to analyze the effective performance compared to the traditional technique. A comparative study of the proposed approach is presented with various parameters of MMC performed using MATLAB Simulink software.

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