Abstract
Virtual synchronous generator (VSG) control is a promising control method for grid-tied inverters, as it can provide inertia support for the grid. However, VSG-controlled grid-tied inverters are subjected to intrinsic low-frequency oscillation, because the emulation of swing equation of a conventional synchronous generator (SG) also introduces an oscillatory mode. In this paper, a damping term produced from state feedback control is added to VSG control to solve this issue. This method is then further developed by applying a low pass filter to the measured active power, to improve its ripple attenuation ability, at the cost of increased design complexity. Both the proposed state feedback damping method without and with low pass filter have one more design degree of freedom than previous methods, which is used to improve dynamic response to active power reference change. The small-signal analyses and experimental results show that both methods can well damp the intrinsic low-frequency oscillation with better dynamic responses than previous fixed-parameter damping methods, whereas the method with a low pass filter has the best overall performance thanks to its improved ripple attenuation ability.
Highlights
Along with the rapid growth of the penetration rate of renewable energy sources (RESs) in the power grid, more and more conventional power plants using synchronous generators (SGs) are replaced by RESs which are connected to the power grid via grid-tied inverters
As both DGs are supposed to be dispatchable with large energy storage connected the DC-link, the input of the inverters can be modeled as a DC source
In this paper, to develop the dedicated damping technology of fixed-parameter virtual synchronous generator (VSG) control, two damping methods of VSG control using state feedback were proposed, and their design procedures to realize a given virtual inertia and damping ratio were discussed in detail
Summary
Along with the rapid growth of the penetration rate of renewable energy sources (RESs) in the power grid, more and more conventional power plants using synchronous generators (SGs) are replaced by RESs which are connected to the power grid via grid-tied inverters. To stabilize the frequency of the future power grid, which is expected to be highly penetrated by grid-tied inverters, it is proposed to emulate the swing equation of SGs in the control scheme of grid-tied inverters. Called virtual synchronous generator (VSG) [1], [2], or virtual synchronous machine (VSM) [3], or synchronverter [4], [5] As these solutions share the same main concept, all these control methods are classified into the category of VSG control in this paper. As most VSG control methods are developed from the droop control concept, the advantages of droop control, such as power sharing between multiple inverters, and seamless transitions between grid-connected and islanded modes, are inherited by VSG control [8]
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