On Grid-Interactive Smart Inverters: Features and Advancements

Abstract

Traditionally, a grid-interactive inverter providing ancillary services is called a smart inverter. However, broader features will be required for the next generation of inverters that can be categorized as self-governing, selfadapting, self-security, and self-healing. For grid-interactive inverters, the self-governing feature can be identified as the capability of inverters to operate in grid-following and grid-forming control modes, where the self-adapting is referred to as more flexibility realized by adaptive controllers for stable dynamics of inverters under various grid conditions. Moreover, for supervisory control and economic dispatch in a grid with high-penetration of inverter-based power generators, a minimum communication might be necessary, but it can place grid-interactive inverters in danger of being hacked when self-security becomes essential to identify malicious setpoints. Furthermore, the self-healing is defined as fault-tolerance and stress reduction under abnormal conditions. It suggests that after realizing these features, an inverter is called a smart inverter. In this paper, the advancements toward achieving these features for grid-interactive inverters are reviewed. INDEX TERMS Smart inverters, self-security, self-adapting, self-governing, self-healing, cyberattacks.

A Grid-Tied Fuel Cell Multilevel Inverter with Low Harmonic Distortions

“…10f g < f res < 0.5f SW (19) It is necessary to check that the resonant frequency satisfies Equation (19). On the contrary, the parameters should be recalculated.…”

“…This investigation's primary concern is to assess whether such topology is reliable and efficient enough for a large-scale grid-tied PEMFC. The assessment's motivation is that this topology, especially without an interfacing power transformer, is reported as a significant unit of modern and smart grids [19], because it offers control freedom while providing lower cost, higher efficiency, smaller size, and lower weight [20].…”

Grid Forming Inverter Modeling, Control, and Applications

“…However, depending on the interaction with the grid, controller implementation and response to the changes in the grid, they can be classified into two main groups, namely: GFLIs and GFMIs, as shown in Fig. 1 (a) [12]. More information, including further subdivisions of the two categories, are given in the following subsections.…”

“…An example Q response requirement is illustrated in Fig. 1 (b), where the reactive power response kicks in to support the grid voltage when there is a deviation [12]. When the grid voltage decreases, the IBR should supply positive reactive power at a predefined droop setting.…”

“…Contrary to GFLIs, GFMIs do not measure the v P CC for synchronization purposes and rather form the v P CC to regulate their power output. Another major difference between the GFLI and GFMI control is that a GFMI can operate/supply the local loads in the absence of grid connection by establishing its own reference voltage and frequency [8], [9], [12]- [14]. This also leads to the difference in synchronization mechanism.…”