Abstract
As a novel topology of microgrid, the output voltage control of MMC half bridge series microgrid (MMC-MG) is rarely studied. In this paper, on the basis of fully analyzing the mechanism of output voltage fluctuation of MMC-MG under the condition of islanded mode, a control strategy of a hybrid energy storage system is proposed to reduce the generating module (GM) DC-link voltage fluctuation caused by the randomness of renewable energy microsource output power. Moreover, in order to further improve the stabilization of the MMC-MG output voltage and meet the requirements of fast voltage recovery and antijamming, a sliding mode controller is designed. Then, a voltage fluctuation compensation controller is designed to suppress the DC component and fundamental frequency deviation of system output voltage caused by GM DC-link voltage fluctuation. The proposed control approach is validated against simulations using MMC-MG models with 4-GM per arm. The results show that the proposed hybrid energy storage control strategy can suppress the GM DC-link voltage fluctuation, the sliding mode controller can stabilize the system output voltage when the load drastic changes, and the fluctuation compensation strategy can suppress the DC component and the fundamental frequency deviation of system output voltage.
Highlights
Microgrid (MG) is an autonomous system that can achieve self-control, protection, and management, which includes distributed generation (DG), load, energy storage devices, and monitoring and protection devices [1,2,3]
In order to ensure the stable operation of MMC half bridge series microgrid (MMC-MG) in the islanded mode, the double-closed-loop control of voltage and current is adopted on the inverter to provide voltage and frequency support. e outer voltage loop determines the reference value of the instruction current and stabilizes the AC side voltage of the inverter. e inner current loop controls the current according to the instruction current to realize the fast tracking
E hybrid energy storage system (HESS) is connected to the generating module (GM) DC link to suppress the DC voltage fluctuation caused by the change of solar radiation intensity. en, design the energy storage converter controller according to Figure 4
Summary
Microgrid (MG) is an autonomous system that can achieve self-control, protection, and management, which includes distributed generation (DG), load, energy storage devices, and monitoring and protection devices [1,2,3]. For the isolated ac MG, the system output voltage loses the power grid support, and effective control methods are needed to maintain the frequency and amplitude of the system output voltage within the standard range [4,5,6]. E hybrid energy storage system (HESS) composed of the supercapacitor (SC) and battery can be used in MG. It plays an important role in stability control, power quality improvement, and uninterrupted power supply of MG [10]. A supervisory power management system for a hybrid MG is proposed in [13]; when MG in the islanded mode, the HESS can effectively
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