## 5 Hybrid AC/DC Microgrid Control Strategies
### Power Generation Control
Error dynamics were used by the designed sliding mode surface to deliver more efficient progress for the state variables based on converters under the variations of parameters. The robustness effects of embedded sliding mode controller, the relationship among the sliding coefficients attained from the permutation of ultimate control strategy, and proposed error dynamics and the errors in the state variable of the converter were examined, and with the help of these relationships, numerous analytical curves were designed. The robustness abilities and dynamics of proposed systems were verified by hybrid microgrid parameter and load variations. Table 4 depicts different aspects and techniques utilized to control AC/DC microgrid power-sharing. A simple subgrid consists of AC and DC bus bars to interchange power from one bus to another. The system needs to utilize some converters called interconnecting converters to increase system reliability, stability, and increased power rating. Multiple interlinking converters are used, as different vendors may have different types of subgrids; some got only renewable resources; some may have some energy storage capabilities; some may allow only linear loads while others allow nonlinear loads. Therefore, their integration with one another is another key factor. Microgrids contain a high amount of power electronics converters that may inject unwanted high-frequency components called harmonics which not only change the shape of voltage and current but also have a severe effect on efficiency, equipment life, and overall system losses, thus creating power quality issues. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Reference** & **Problem** & **Proposed Solution Strategy** \\ \hline
[93] & Bad transient performance & A control strategy based on improved virtual synchronous generator (VSG) \\
[94] & Affected permeability of distributed generations (Distributed generators) & Architecture based on the controllability of the modular multilevel converter based solid-state transformer (MMC-SST) \\
[95] & Consuming and coordinating a huge quantity of distributed generators within the alone microgrid & A novel design of architecture for numerous microgrids and its coordinated control schemes \\
[96] & When interlinking converter participate in a reactive power of AC microgrid, it adds some more complexity to a hybrid microgrid control system & A droop based decentralized control strategy \\
[97] & Deregulation of output voltage & A model-based controller for a bi-directional interlink converter in DC sub-grid of a hybrid DC/AC microgrid based on PID and LTI model \\
[98] & Uncontrollability of a hybrid AC/DC microgrid under both parameters and load alteration & By a robust control technique working on the principle of sliding mode surface \\
[99] & System collapse and unsmooth transition due to a slower mode switch or an inaccuracy & A uniform control strategy for a bidirectional DC/AC interlinking converter in a hybrid DC/AC microgrid system and a steady-state model for a multi-port electric energy router \\
[100] & The challenge with regard to power flow procedure for a hybrid DC/AC microgrid systems & A coordinated control strategy is designed for a microgrid with DC/AC loads and hybrid energy resources \\
[101] & The challenge to integrate conventional power generators and renewable energy resources with distributed networks & A droop-controlled scheme was used among DC and AC microgrid for the hybrid DC/AC microgrid for energy management and managed a power and voltage regulation \\
[103] & Management issues and power flow control between different sources distributed over both DC and AC microgrid & A decentralized sharing of the power method \\
[104] & Operational reliability and the requirement of power-sharing and the appropriate power distribution between DC and AC subgrids to sustain DC and AC side voltage balanced & A control scheme for the interlinking of a converter with energy storage or DC-link capacitor \\ \hline \hline \end{tabular}
\end{table}