A Vector Control for Grid-connected Wind Power Generation with Doubly Fed Induction Generator

Abstract

Recently, doubly fed induction generator (DFIG) and synchronous generator are mostly applied for wind power generation due to high efficiently for wind energy capture. An inverter system is required to control wind turbine speed and power factor in those generators. The inverter rating of the synchronous generator equals to generator rating. However, DFIG has the advantage that the inverter rating is about 25% to the generator rating. The paper describes a vector control of DFIG inter-connected to power line.To enable independent control of the stator active power P 1 and the stator reactive power Q 1 of the DFIG, a vector control is used. The active power is determined by the rotor q-axis current and the reactive power is determined by the rotor d-axis current. By the control of those currents, the wind turbine speed and the power factor are controlled independently. A wind turbine speed varies according to the active power. Thus, the speed is controlled by the rotor q-axis current and the power factor is controlled by the rotor d-axis current. The rotor d-axis voltage and q-axis voltage are expressed by the generator parameters and slip of DFIG, power system voltage, the rotor d-axis current and the q-axis current. A voltage source inverter connected on the rotor winding carries out the control of the active power and the reactive power.The performance of proposed vector control is examined using power system simulation software PSCAD/EMTDC for the DFIG inter-connected to 6.6 kV distribution line. The system configuration of wind power generation is shown in Fig. 1. The DFIG parameters are shown in Table 1. Simulation result for step response to the stator active power reference value and turbine output is shown in Fig. 2. Also, it for step response to the stator reactive power reference value is shown in Fig. 3. The detailed simulation results by PSCAD/EMTDC show good dynamic responses and high accuracy to the stator active power control and the stator reactive power control.

Study of Low‐Voltage Ride‐Through Performance for Wind Power Generation with Doubly Fed Induction Generator

“…. Explanations of this control scheme were given in a previous paper and hence are omitted here. Below we explain only the control of the power charged to the capacitor during isolated operation.…”

“…In the grid‐connected state, inverter A performs active/reactive power control, while inverter B performs variable‐speed control and power factor control . During the period from detection of a grid fault until reconnection, inverter A performs isolated operation control and synchronization control, while inverter B performs variable‐speed control and zero reactive power control.…”

“…Inverter A is connected to the primary side and inverter B is connected to the secondary side via a slip ring . We have proposed a method for variable‐speed control and power factor control (maximum power point tracking control) based on the equation for the shaft voltage in d–q rotating coordinates for the steady state of an induction machine, ignoring the primary resistance, and on the fact that the active power on the secondary side can be approximated from that on the primary side multiplied by the slip . The proposed method has a strong smoothing effect on output fluctuations .…”

Study on the Gear Ratio for a Tidal Current Power Generation System Using the MPPT Control Method

“…The DFIG employed in this study is able to independently control the active and reactive powers by adjusting the voltage supplied to the generator rotor circuit from the inverter placed between the power grid and the rotor circuit (Kai et al, 2008). Characteristics of variable-speed operation employing DFIG have been examined in numerous studies, including investigations into generated output (Datta and Ranganathan, 2002;Uctug et al, 1994) and speed control systems (Pena et al, 1996;Luo et al, 2007;Mauricio et al, 2008).…”

Characteristic analysis of a wind power system with doubly fed induction generator in considering of the tower shadow effect

“…A feature of a multipolar synchronous generator is that the generator does not need a gear. On the other hand, DFIG is used for large-sized generator, and has many features such as reductions of size of system, cost of development, and total power loss [2].…”