Artificial Intelligence based Control Design for Reliable Virtual Synchronous Generators

Abstract : Virtual synchronous generator (VSG) is a promising solution for inertia support of the future electricity grid to deal with the frequency stability issues caused by the high penetration of renewable generations. However, the power variation in power electronic interface converters caused by VSG emulation increases the stress on power semiconductor devices and hence has a negative impact on their reliability. Unlike existing works that only consider stability for VSG control design, this article proposes a double-artificial neural network (ANN)-based method for designing VSG inertia parameter considering simultaneously the reliability and stability. First, a representative frequency profile is generated to extract various VSG power injection profiles under different inertia values through detailed simulations. Next, a functional relationship between inertia parameter ( [Math Processing Error] ) and lifetime consumption (LC) of VSG is established by the proposed double-ANN reliability model: [Math Processing Error] provides fast and accurate modeling of thermal stress in the semiconductor devices from a given operating profile; with the aid of [Math Processing Error] , [Math Processing Error] is built for fast and accurate estimation of LC for different inertia parameters in the next step. The proposed approach not only provides a guideline for parameter design given a certain LC requirement, but can also be used for optimal design of VSG parameter considering reliability and other factors (e.g., inertia support in this article). The proposed technique is applied to a grid-connected VSG system as a demonstration example.
 ? The main portion of DGs are renewable energy sources (RESs) such as wind turbines and photovoltaics. ? Most of these RESs are connected to the grid through a three-phase inverter. The grid current control is the traditional method for controlling the power penetration of the inverter-based DGs. ? To synchronize the inverter with the grid, this method typically uses a phaselocked loop (PLL). ? To overcome the traditional controller drawbacks, numerous solutions have been proposed. To present the ‘sync’ and ‘inertia’ mechanism of SGs to inverters, a novel control named the virtual synchronous generator (VSG) has been proposed by some scholars.
 ? To solve this problem, virtual synchronous generator (VSG) concept was proposed to emulate some of the features of conventional SG through converter control strategy in order to provide additional inertia virtually. ? Some researchers proffer solution to this problem through the evolution of droop-based control systems for microgrids operation dominated by PECs and converters in a stand-alone operation. ? Different design process focused on transfer function and Bode plots was presented in to reduce the computation problem in the previous model. ? Nevertheless, the disadvantage of the method is large computations requirement and some parameters or states may not be feasible.
 • In, different virtual synchronous generator control strategies have been proposed to improve the frequency, voltage, transient stability and damping characteristic of power system with renewable power generators. • Since synchronous generators have good capacity to regulate the frequency of power system, the concept that converters are controlled to express as a synchronous generator has been proposed which is called VSG. • Hence the TEF descent method can be proposed to design an inertia controller to dissipate the unbalanced energy and suppress the power oscillation. • It could be found that the VSG’s virtual moment of inertia is controlled by the proposed bang-bang control strategy.
 ? In, some simplification was employed by tuning control parameters online, in order to realize better performance and efficient damping effect. ? More real-time experiments need to be conducted to see the influence and performance of VSG controller. ? The main concern of these DG technologies is maximization of power supply to the grid while delivering efficient and operability in case of system faults and disturbances. ? VSG can be developed and implemented for DG systems by employing short-term ESS and PECs with efficient control technique which then operates like conventional SG by exhibiting some amount of inertia and damping characteristics for short period of time.

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