A Variable Speed Wind Turbine Control Strategy to Meet Wind Farm Grid Code Requirements

Abstract

This paper presents a new operational strategy for a small scale wind farm which is composed of both fixed and variable speed wind turbine generator systems (WTGS). Fixed speed wind generators suffer greatly from meeting the requirements of new wind farm grid code, because they are largely dependent on reactive power. Integration of flexible ac transmission systems (FACTS) devices is a solution to overcome that problem, though it definitely increases the overall cost. Therefore, in this paper, we focuses on a new wind farm topology, where series or parallel connected fixed speed WTGSs are installed with variable speed wind turbine (VSWT) driven permanent magnet synchronous generators (PMSG). VSWT-PMSG uses a fully controlled frequency converter for grid interfacing and it has abilities to control its reactive power as well as to provide maximum power to the grid. Suitable control strategy is developed in this paper for the multilevel frequency converter of VSWT-PMSG. A real grid code defined in the power system is considered to analyze the low voltage ride through (LVRT) characteristic of both fixed and variable speed WTGSs. Moreover, dynamic performance of the system is also evaluated using real wind speed data. Simulation results clearly show that the proposed topology can be a cost effective solution to augment the LVRT requirement as well as to minimize voltage fluctuation of both fixed and variable speed WTGSs.Index Terms-Frequency converter, low voltage ride through (LVRT), multilevel converter/inverter, permanent magnet synchronous generator (PMSG), voltage source converter (VSC), wind generator.

Frequency Regulation Strategies in Grid Integrated Offshore Wind Turbines via VSC-HVDC Technology: A Review

“…The relation is: VDC > 1.633 Vg-LL, as stated in [34]. In order to realize a transfer of active power generated by the PMSG to the grid, the capacitor voltage is varied during wind turbine operations [35]. The dynamic model of the grid connection, in the reference frame rotating synchronously with the grid voltage, is given as follows [29]:…”

“…Also in order to transfer all the active power generated by the wind turbine the dc-link voltage must remain constant [35], as per in the following constraint [36]:…”

Power system transient stability enhancement using direct drive wind generators

“…However, when a short circuit fault occurs in the power system, the electromagnetic torque of the machine reduces proportional to the square of the remnant voltages causing the rotor to accelerate beyond its safety limits. Also, as the fault occurs, the induction machine absorbs large reactive power in order to recover the air gap flux [9]. Otherwise, large difference between electromagnetic and mechanical torques can lead to the instability of the machine.…”

“…It has been demonstrated in [6,17] that direct drive wind turbine can improve transient and voltage stability of its adjacent grid. In [9], it is also shown that the capability of fixed speed wind generators to ride through the fault can be improved by installing direct drive wind turbine in parallel and series. The control strategies are designed considering the grid codes set by the Federal Energy Regulatory Commission (FERC) but the effect of overloading the converter current is not shown.…”

Emulador de Lazo Abierto para Turbinas Eólicas de Paso Fijo

“…En las turbinas de velocidad variable, la velocidad de giro se controla mediante un convertidor electrónico de potencia (Muyeen et al, 2010). Éste tiene una doble misión, además de controlar la velocidad, se encarga de convertir la tensión alterna producida por el generador en corriente continua.…”