Power oscillations damping using wide-area-based solar plant considering adaptive time-delay compensation

Abstract

The aim of this paper is to investigate the use of the ever increasing penetration of renewable energy into the power grid to solve challenging problems such as inter area power oscillations without the use of expensive power electronic devices and power system stabilizers. The increase in size of interconnected power systems, energy demand, and installation of remote renewable energies with relatively weak tie-lines has witnessed different stability problems such as low-frequency inter-area oscillations. Inter-area oscillation reduces system stability and transmission capacity. Without effective damping control mechanism, these oscillations could prolong and threaten the security of the system. This paper proposes a supplementary controller from a photovoltaic (PV) solar plant for damping inter-area oscillations. Due to its strong correlation to active power flow and monitoring system stress, area phase-angle difference is employed for the remote signal input of the controller. The signal can be obtained from phasor measurement unit (PMU) through wide-area measurements systems (WAMS). To deal with a wide range of variable delay in the signal input, an adaptive compensator is designed to reduce the impact of the communication latency using neuro-fuzzy inference system. A two-area four-machine test system is used and simulated with a Simulink-based package developed for the work of this study. The time-domain simulations, modal and frequency response analysis demonstrate the capability of the proposed controller to effectively damp inter-area oscillations, under a small- and large-scale disturbances and against a wide range of time delays.

Appendices

Appendix I: Nomenclature

$R_{s}$	Stator resistance in pu	$\varPsi_{2q}$	Damper winding 2q flux linkages in pu
$X_{d}$	d-axis reactance in pu	$\delta$	Rotor angle in rad
$X_{d}^{ '}$	Transient d-axis reactance in pu	$w$	Angular speed of generator in rad per second
$X_{d}^{"}$	Sub-transient d-axis reactance in pu	$\bar{V}_{i}$	Complex voltage phasor
$X_{q}$	q-axis reactance in pu	$V$	Magnitude of bus voltage in pu
$X_{q}^{ '}$	Transient q-axis reactance in pu	$\theta$	Angle of bus voltage in rad
$X_{q}^{"}$	Sub-transient q-axis reactance in pu	$\bar{I}_{Gi}$	Generator complex current phasor
$H$	Shaft inertia constant in second	$I_{Gi}$	Generator current magnitude in pu
$w_{s}$	Generator synchronous speed in rad per second	$\gamma_{i}$	Generator current angle in rad
$T_{do}^{ '}$	d-axis time constant associated with $E_{q}^{ '}$ in second	$I_{d}$	d-axis current in pu
$T_{do}^{"}$	d-axis time constant associated with ${{\varPsi }}_{1d}$ in second	$I_{q}$	q-axis current in pu
$T_{qo}^{'}$	q-axis time constant associated with $E_{d}^{ '}$ in second	$\alpha_{ik}$	Angle of admittance $Y_{ik}$ in rad
$T_{qo}^{"}$	q-axis time constant associated with ${{\varPsi }}_{2q}$ in second	$E_{fd}$	Field voltage in pu
$T_{A}$	Amplifier time constant in second	$V_{R}$	Exciter input in pu
$T_{CH}$	Incremental steam chest time constant in second	$R_{F}$	Rate feedback in pu
$T_{SV}$	Steam valve time constant in second	$T_{M}$	Mechanical input torque in pu
$K_{A}$	Amplifier gain	$P_{SV}$	Steam valve position in pu
$K_{E}$	Separate or self-excited constant	$P_{C}$	Control power input in pu
$E_{q}^{ '}$	q-axis transient internal voltages in pu	$R_{D}$	Speed regulation quantity in Hz/pu
$E_{d}^{ '}$	d-axis transient internal voltages in pu	$V_{ref}$	Reference voltage input in pu
$E$	Internal voltage in pu	$S_{E}$	Saturation function
$\varPsi_{1d}$	Damper winding 1d flux linkages in pu	$T_{FW}$	Frictional windage torques

Appendix II: controller optimized parameters

• $T_{p}$ and $T_{q}$  = 0.01 are obtained from [4]

• PI-1: P = 11.5793; I = 0.014.

• PI-2: P = 0.4272; I = 0.2951.

• k = 30.586043917533246.

• T₁ = 0.055092716680820, T₂ = 0.012935893916115.

• T₃ = 0.011403037122928, T₄ = 0.140082291517591.

Appendix III

See Tables 2 and 3 in appendix.