Protecting DFIG‐based multi‐machine power system under transient‐state by nonlinear adaptive backstepping controller‐based capacitive BFCL

Abstract

The invention of doubly‐fed induction generator (DFIG) brings the wind energy one step ahead as renewable power generation. But the performance of the grid‐connected DFIGs are greatly affected by grid disturbances as their stator windings are interfaced to the grid directly. Different fault current limiters are capable of improving fault ride through capability during short circuit faults. Nonlinear controller based fault current limiters (FCLs) are superior to deal with the nonlinearity of the power systems. This paper proposes a nonlinear adaptive backstepping controller (ABSC) based capacitive bridge‐type FCL (CBFCL) to enhance the fault ride through capability of a DFIG‐based wind farm connected to a multi‐machine power system. At first, a complete modelling of the CBFCL is derived to understand its behaviour during the normal and fault period more accurately. Then, the ABSC is designed based on that dynamic model, along with the backstepping controller (BSC) and sliding mode controller (SMC) for comparison purpose. Finally, the performance of the ABSC to control the CBFCL has been analysed and verified by comparing with that of the BSC and the sliding mode controller. All the graphical and mathematical analyses favour the ABSC based CBFCL under symmetrical and asymmetrical fault (both temporary and permanent) scenarios.

Improved Transient Performance of a DFIG-Based Wind-Power System Using the Combined Control of Active Crowbars

“…Considering the worst-case scenario when s = −0.3, the initial amplitude of the rotor EMF can be approximated by Equation (24).…”

“…Obviously, the rotor EMF's initial amplitude is high under asymmetrical grid faults, owing to its negative-sequence component. Based on the above analysis and Equations ( 16) and (24), it is simple to realize that the deepest asymmetrical fault (phase-to-phase) is far more pronounced than the symmetrical fault of the same voltage dip level.…”

“…Modern WTs mostly include assisting hardware, such as crowbar protection [8,21,22], to mitigate DC-link voltage variations. Presently, the application of fault-current limiters (FCLs), such as an inductive bridge-type FCL [23] and a capacitive bridge-type FCL [5,[24][25][26], has attracted special attention as a potential solution for LVRT enhancement. Other hardware applications, such as a STATCOM [27], an energy storage device (ESD) [22,28], and a dynamic voltage restorer [29], have also been recommended.…”

Improved Transient Performance of DFIG-Based Wind-Power System Using Combined Control of Active Crowbars

“…Considering the worst scenario when s = -0.3, the initial amplitude of the rotor EMF can be approximated by using (24)…”

“…Modern WTs most frequently include assisting hardware, like crowbar protection [8,21,22], to mitigate DC-link voltage variations. Presently, the application of fault-current limiters (FCLs) such as an inductive bridge-type FCL [23] and a capacitive bridge-type FCL [5,[24][25][26], has attracted special attention as a prospective solution for LVRT enhancement. Other hardware applications, such as a STATCOM [27], an energy storage device (ESD) [22,28], and a dynamic voltage restorer [29], have also been recommended.…”