Power Quality Services Provided by Virtually Synchronous FACTS

Abstract

The variable and unpredictable behavior of renewable energies impacts the performance of power systems negatively, threatening their stability and hindering their efficient operation. Flexible ac transmission systems (FACTS) devices are able to emulate the connection of parallel and series impedances in the transmission system, which improves the regulation of power systems with a high share of renewables, avoiding congestions, enhancing their response in front of contingencies and, in summary, increasing their utilization and reliability. Proper control of voltage and current under distorted and unbalanced transient grid conditions is one of the most critical issues in the control of FACTS devices to emulate such apparent impedances. This paper describes how the synchronous power controller (SPC) can be used to implement virtually synchronous FACTS. It presents the SPC functionalities, emphasizing in particular the importance of virtual admittance emulation by FACTS devices in order to control transient unbalanced currents during faults and attenuate harmonics. Finally, the results demonstrate the effectiveness of SPC-based FACTS devices in improving power quality of electrical networks. This is a result of their contribution to voltage balancing at point of connection during asymmetrical faults and the improvement of grid voltage quality by controlling harmonics flow.

Grid-Forming Power Converters Tuned Through Artificial Intelligence to Damp Subsynchronous Interactions in Electrical Grids

“…Finally, the Bootstrap implies feature and pattern sampling selection is done with replacement. The RF is evaluated using a 10-fold cross validation, recording both the R2 score, in (14) and Mean Absolute Error (MAE), in (15). The former measures how well the features explain the target variable with values ranging from 0 (worse) to 1 (best).…”

“…Among the various VSM strategies, reported in the literature, the Synchronous Power Controller (SPC) has been widely used mainly due its simple yet effective control structure [12]. By employing the SPC, power converters can provide virtual damping and synthetic inertia to the grid, increasing its dynamic flexibility to improve local and inter-area stability [13], [14]. In fact, the SPC with multiple power loop controllers (PLC) has been presented in [15].…”

Stability Assessment of Current Controller with Harmonic Compensator for LCL-Filtered Grid-Connected Inverter under Distorted Weak Grid

“…To determine a gain matrix which minimizes the quadratic cost function, the symmetric weighting matrices are chosen with the relative importance of the state variables and expenditure of energy by control input signals. Since the augmentation of the control terms into the inverter systems causes the increase of the number of feedback gains, the LQR approach produces a systematical method to find the optimal gains of the current controller and to avoid laborious process for proper gain selections [33,34]. The numerical calculation to determine the gain matrix is accomplished offline with MATLAB.…”

“…Figure34. Experimental result of grid-side currents for integral-resonant state feedback controller with L1 = 1.7 mH, L2 = 1.0 mH, and Cf = 4.5 µF under distorted grid voltages and Lg = 21 mH in Case 1.…”

A Power Angle Limiting Method for Improving Stability of Grid-Forming Inverter Under Overcurrent Condition

“…Based on existing studies [8], [9], it is known that the smallsignal stability of the virtual-admittance-based GFM inverter is already acceptable under normal conditions. Specifically, when the value of virtual admittance is designed properly, the system is always stable within a wide range of short-circuit ratios (SCRs) [8].…”