A coordinated control strategy using supercapacitor energy storage and series dynamic resistor for enhancement of fault ride-through of doubly fed induction generator

ABSTRACT

Power fluctuation and fault-related complication are the two major issues for doubly fed induction generator (DFIG)-based wind energy conversion system (WECS). The occurrence of fault leads to the rotor over current, stator over current, and DC-link overvoltage as well. These uncertainties may damage the rotor circuit, converter circuit and force the disconnection of wind system from the grid. To get rid of these issues, a supercapacitor energy storage element along with a passive series dynamic resistor (SDR) is suggested in this paper. Supercapacitor energy storage system (SCESS) is located across the DC-link, which able to handle the power fluctuation and the SDR is placed in rotor circuit, which will reduce the overcurrent possibility. Simulation is carried for a DFIG-based WECS for three phase to ground fault and two phase to ground fault. During symmetrical fault  as well as asymmetrical fault, various operational disorders appeared such as rotor overcurrent, stator overcurrent and  DC-Link overvoltage are found to be within  their permissible limits. The results reveal the effectiveness of the proposed strategy over the conventional vector control scheme and SCESS as well.

KEYWORDS:

• Doubly fed induction generator (DFIG)
• supercapacitor energy storage system (SCESS)
• series dynamic resistor (SDR)
• vector control (VC) scheme
• wind energy conversion system (WECS)

Nomenclature

BESS	=	Battery energy storage system
DFIG	=	Doubly fed induction generator
FRT	=	Fault ride-through
LVRT	=	Low-voltage ride-through
PCC	=	Point of common coupling
RSC, GSC	=	Rotor side converter and grid side converter
SCESS	=	Supercapacitor energy storage system
SDR	=	Series dynamic resistor
SFCL	=	Superconducting fault current limiter
VC	=	Vector control
WECS	=	Wind energy conversion system
WT	=	Wind turbine

Symbols

V	=	Wind speed
A	=	Blade swept area
ρ	=	Air density
β	=	Blade pitch angle
λ	=	Tip speed ratio
$\phi$	=	Flux linkage
${\phi }_f$,${\phi }_n$	=	Forced flux and natural flux
R	=	Resistance per phase
${\omega }_{\mathrm{s}}$	=	Synchronous angular speed
$V_s$	=	Stator voltage
Ks	=	Stator coupling coefficient
E,$V_{r0}$	=	Induced back EMF in the rotor circuit
$P_g$,$P_r$	=	Power from GSC and RSC
$i_{th}$	=	Threshold current
ir	=	Rotor current
${\tau }_{\mathrm{s}}$,${\tau }_{\mathrm{r}}$	=	Stator and rotor time constant
P	=	Percentage of voltage dip

Subscripts

r and s	=	Rotor and stator quantities
a, b, c	=	Three-phase variable
1, 2, 0	=	Positive, negative and zero sequence

Additional information

Funding

The work was supported by Council of Scientific & Industrial Research (CSIR), Grant/Award Number:22(0713) /16/EMR‐II.