Grid-Forming Control Suitable for Large Power Transmission System Applications

Abstract

The inner cascaded structure-based grid-forming control is a typical solution used to impose an AC voltage magnitude across the output filters of the power inverters. Yet, because of the limited inverter’s bandwidth resulting from the low-switching frequencies in transmission systems, the interaction (i.e., coupling) between control loops is highly likely making the understanding of the system behavior complex and its simplification unaffordable and may also lead to instabilities. The novelty of this paper consists in proposing a simple open-loop direct voltage control to reduce the number of the inner control regulators, and thereby guaranteeing a decoupling between the inner and outer control layers as well as increasing the system stability margin. This statement is well supported with a small-signal analysis and progressive order model reduction of the system. The overall concept is validated in a 10-bus grid case while comparing the EMT and Phasor-based simulations. The practical feasibility of the control itself is experimentally proved with different test cases.

Operating Grid-Forming Control on Automotive Reversible Battery Charger

“…This inductance dominates Z c . Consequently, R c can be neglected in (8) and (9). The expression of P P CC and Q P CC becomes the ones of ( 10) and ( 11):…”

“…The active power control adopted is the conventional droopbased grid-forming control (without PLL) ( [10], [12]). The control system is structured in Fig.…”

“…4. By considering V g = 1, and V m = 1, the gain m p is calculated as illustrated in (12), where t r95 is the time response requested. As far as reactive power control is concerned, it is chosen to keep V m = 1 p.u.. For the tests showed in this papers, it permits the converter to furnish the reactive power requested without restrictions.…”

“…This resistance does not impact the steady-state of the system. More detailed information about this phenomenon can be found in [12] and [14].…”

“…More recently, they have been taken up in a mode of high-voltage transmission networks, where RES become the majority against the conventional means of energy production. The "Power System Team" at the L2EP has mastered the knowledge of grid-forming at the transmission networks ( [8], [9], [10]). Compared to the literature available on grid-forming, this paper focuses on the specific case of the automotive charger.…”