## 5 Future Research
### Industrial Implementation of VI-Based Inverters  
From industry aspect, the adoption of VI-based inverter is a promising technology to accelerate the RES grid integration, as compared with a conventional inverter. By 2020, 20% of the global electricity will be generated by RES and fed to the grid. As the RES continues to grow, the microgrid is the key component of the decentralized energy system to support the development of smarter communities. It is a game-changer in a modern power system by shifting to modular, feasible, and scalable alternatives. To ensure the compliance and compatibility of multi-vendor microgrid systems, there is a necessity to emphasize on the standardization of control and communication technologies. It implies that VI-based inverter is the grid enabler in the microgrid to interface RES into a unified power system without sacrificing the system stability.  
From the microgrid operator perspective, the high penetration of RES is a welcoming trend due to its cost-effectiveness and environmentally friendly nature. However, the grid stability will be adversely affected by these RES, and thus these concerns limit the utilization of renewable generation in traditional grids or microgrids. The operators do not want to risk instability issues. A blackout might occur in microgrid due to the lack of stabilizing functionality. To make matters worse, the intermittent nature of RES results in large fluctuations in power angle, grid voltage, and power flow. The VI-based inverter has been commercialized as a key project of European Commission Horizon 2020. In a microgrid, with high involvement of RES, alongside with ESS and loads, one of the most important considerations is the control of power converters. As an effort of standardization, most microgrid operators demand the VI emulation via VI-based inverters.  
The modularity of the VI-based controller is expected to be commercialized, enabling the easy conversion of the normal inverter via PWM control. Inverter manufacturers such as Schneider Electric, ABB, and FREQCON have included VI response as a key feature in their inverters model lineup, specifically for RES grid integration. For example, ABB microgrid integrates RES by providing VI, grid stabilization, and other ancillary power system services. Another product from ABB--grid stabilizer--is designed to provide VI as an ancillary power system service. It can connect to any point on the network as its versatile ancillary support. It responds to stabilize frequency disturbances, with load shedding minimization. Another product from ABB is the Renewable-to-Grid Connector solution. It reduces the limitations of weak grids from the connection of intermittent renewable generation by improving RES output via VI. This solution provides a standardized and compliant grid connection for any existing form of RES into a weak grid. From the power operator perspective, Hydro-Quebec Transenergie's (HQT) transmission connection VI requirements are the first power operator to ensure that wind powerplants must be equipped with an inertia emulation system. SYNDEM is another company which focuses on the research of VSM to provide synchronized and democratized power system. From all industrial development, it can be concluded that VI is a crucial element in a commercialized RES grid integration. Thus, more manufacturers, academia researchers and industrial players are involved in the design and advancement of VI application, not limited to RES integration only.