Optimal Frequency Control for Virtual Synchronous Generator Based AC Microgrids via Adaptive Dynamic Programming

Abstract

This paper proposes a novel virtual synchronous generator (VSG) controller for converters in AC microgrids (MGs). Such controller improves the control cost and DC-side energy requirements, while considering the system non-linearity for frequency support. First, the frequency dynamics of the MG, which are analytically studied based on the VSG with a secondary frequency controller, are formulated as a nonlinear state space representation. In this later, the reciprocal of the inertia is modeled as the control input. Correspondingly, a cost function is defined by comprehensively considering the angular deviation, frequency deviation, rate of change of the frequency (RoCoF), and a discount factor, which can retain a tradeoff between the critical frequency bounds and the required control energy. Following, the optimal frequency regulation problem is solved by using an online adaptive dynamic programming (ADP) method, where a single echo state network (ESN) is constructed to approximate the optimal cost function and the optimal control input to significantly reduce the computational burden and improve the real-time computation. Finally, simulation results demonstrate that the frequency response of the system is significantly improved, while also retaining more DCside energy.

Driving the Energy Transition: Large-Scale Electric Vehicle Use for Renewable Power Integration

“…Most importantly, the proposition of this technology comes as a solution to the widespread problem that renewable energy production is often most abundant during hours which are very different from the peak load hours of the power grid they supply energy to [6][7][8][9][10][11][12].…”

Pre Synchronization Control Strategy of Virtual Synchronous Generator (VSG) in Micro-Grid

“…The integral coefficient corresponding to the damping ratio 0.707 ξ = of the typical second-order system can be taken as the value of p K . This can ensure stable system response in frequency recovery stage 2 and avoid excessive frequency deviation [29]. The specific expression is equation (17).…”

Optimization of a Virtual Synchronous Control Parameter for a Wind Turbine Generator Considering the Physical Constraint Boundary of Primary Frequency Regulation

“…By substituting (10) into (8), the deviation of rotor speed for the WTG can be obtained during the PFR process:…”

“…The fluctuation of the output frequency and power can be suppressed. In addition, the system's stability can be improved by using VSG control, which has a broad prospect of application [10,11]. On the other hand, the WTGs participate in frequency regulation mainly through load reduction control [12,13] and rotor kinetic energy control [14,15].…”