Reza Haghniaz - Department of Electrical Engineering, Langarud Branch, Islamic Azad University, Langarud, Iran
Mohammad Khoshhal Rudposhti - Department of Electrical Engineering, Langarud Branch, Islamic Azad University, Langarud, Iran

The purpose of this paper is to design a new improved hierarchical control method for optimal hybrid microgrid performance. The issue of microgrids is one of the newest challenges in the field of power engineering and control. In microgrid control, the main purpose is to control the voltage / frequency using reactive / active power. This means that the frequency and voltage in the microgrid are controlled using active and reactive power inputs, respectively. The control methods are primary, secondary and tertiary microgrid control. In the initial microgrid control, the initial microgrid stability is considered. This stability is based on the frequency angle and the microgrid frequency. Initial control is always associated with error. Especially when the load changes or a source goes out and all the islanding (disconnection from the upstream network) occurs. In this case, secondary control is used. In tertiary control, which is specific to widely distributed microgrids, a section called the master controller is used. The task of this controller is to create coordination between the different control sections of the microgrid. In this research, a coordinated and multilevel control scheme is proposed to improve the performance of the hybrid microgrid. This structure ensures the stability of the microgrid in different operating conditions due to the correct operation of the control system and the interaction of distributed generation sources, energy storage resources. The proposed control scheme consists of three control levels that are effectively coordinated in order to solve all the challenges of stability and maintain voltage and frequency values at nominal values. The first level of the control system is responsible for the stability of the DC part of the microgrid by regulating the DC bus voltage and managing the power exchanged between the AC and DC sections. The second and third levels are responsible for regulating the voltage and frequency of the AC part of the microgrid by managing reactive and active power. According to the results, the proposed control structure has a very good performance against various types of disturbances in different conditions of microgrid operation and its optimal performance is confirmed. The results obtained from the validation simulation confirm the proposed control system.

Hierarchical Control; Distributed Generation; Hybrid microgrid; Stability