DFIG Power Generation Capability and Feasibility Regions Under Unbalanced Grid Voltage Conditions

Abstract

Several strategies have been proposed for operating doubly-fed induction generator (DFIG)-based wind turbine under unbalanced grid voltage conditions. This study focuses on those strategies in which the rotor-side power converter aims at eliminating the oscillations affecting the electromagnetic torque and the stator reactive power. Given the limited size of the DFIG's power converters, and hence their tolerable current and voltage boundaries, this study analyzes which DFIG power generation capability is under unbalanced grid voltage, and therefrom derives rotor current and stator power controllable ranges. Besides, the feasibility regions of the DFIG are also deduced for different types of imbalance. Furthermore, and based on the outcome of previous analysis, a modified rotor current limiter, as also its equivalent stator power limiter, is proposed. In contrast to the conventional ones, the limiters proposed here take into account that imbalances may arise in the grid voltage. As a consequence, system's overall performance is considerably enhanced under unbalanced grid voltage conditions. Finally, simulation results establish the validity of the treated issues.Index Terms-Doubly-fed induction generators, feasibility region, industrial power system control, unbalanced voltage, vector control, wind power generation. NOMENCLATUREi r , i s Rotor and stator current space-vectors. I r peak Maximum permissible rotor current. L m Magnetizing inductance. L r , L s Rotor and stator inductances. L r Rotor transient inductance. P Number of pole pairs. P s , Q s Stator-side active and reactive powers. R r , R s Rotor and stator resistances. s Slip of the generator. T e Electromagnetic torque. v c Space-vector of the voltage induced in rotor windings.

Sliding-Mode Control for DFIG Rotor- and Grid-Side Converters Under Unbalanced and Harmonically Distorted Grid Voltage

“…Although the suitability of SMC for handling unbalanced and harmonically distorted scenarios has been proved in Section IV, the capability to generate power under deteriorated grid voltage conditions decreases [26], [27]. As a consequence, it may happen that, during adverse conditions-i.e., from a certain imbalance or disturbed factor, and with a slip close to its limit value-it becomes impossible to generate the exact amount of reactive power that several countries' grid codes demand nowadays.…”

DTC-SVPWM of an Energy Storage Flywheel Associated with a Wind Turbine Based on the DFIM

“…(6) Currents and voltages in the  system are determined from the three-phase variables using the transformation of Concordia. Being very difficult to measure the voltages at the terminals of a three-phase inverter voltage supply voltages are estimated based on the DC bus voltage and switching states of the inverter arm.…”

“…The storage of electricity often goes through an intermediate form (gravity, compression, chemical kinetics, mechanics ....). [5,6,7,8] We will focus in this work to storage modes that can be associated with a wind turbine. The purpose is twofold: to store electrical energy during periods of high wind to be able to return in periods of low wind and smooth maximum power generated by wind more storage together.…”

Coordinated Control of a Doubly-Fed Induction Generator-Based Wind Farm and a Static Synchronous Compensator for Low Voltage Ride-through Grid Code Compliance during Asymmetrical Grid Faults

“…The controllable regions associated with each case is the area below its corresponding line in Figure 4, and the tolerated δ max is given in Table 3. Though the controllable regions of DFIG-based WECS with limited RSC rating considered have been explored by means of various approaches and represented in different forms [30,37], it is worth pointing out that, with regard to the proposed control scheme for DFIG-based WECS in Section 2, the limited GSC rating is the primary factor, as shown in Figure 4.…”