**4.4 Reduction of switching power losses**

The right choice of zero vectors V0 and V7 implies that there is reduction in switching power loss of the converter. Two different switching sequences exist for each pair of required active vectors, which allows the commutations of the converter to be reduced. **Table 3** shows the correct sequence of vectors, which allows only four commutations per switching period ts. The candidate sequences are such


#### **Figure 2.**

*Block diagram of proposed predictive direct torque control strategy of DFIM.*


#### **Table 2.**

*Selection of active vectors under steady-state [13].*


#### **Table 3.**

*Sequence of vector selection for reduction of switching power losses under steady-state [13].*

that it reduces the switching power losses by transmitting the smallest current values, which is the main task of the proposed control strategy.

conditions of steady state, transient, tracking behavior, and performance near syn-

Number of blades 3 Rotor diameter 70 m Hub height 84.3 m Turbine total Inertia 4.4532 e5Kgm<sup>2</sup> Stiffness constant (B) 2 pu Mutual damping 1.5 pu Cut-in wind speed 3 ms<sup>1</sup> Cut-out wind speed 25 ms<sup>1</sup> Rated wind speed 15 ms<sup>1</sup>

**Specifications Ratings** Rated power 2.6 MW Rated voltage 690 V Synchronous speed 1500 rpm Frequency 50 Hz Number of pairs of poles 2 Stator to rotor turns ratio 0.34 Base voltage 398.4 V Base current 2175 A Base angular frequency 157 rads<sup>1</sup> Base power 2.6 MW Stator resistance 0.0108 pu Stator leakage inductance 0.102 pu Magnetizing inductance 3.362 pu Rotor resistance referred to stator 0.0121 pu Rotor leakage inductance referred to stator 0.11 pu Inertia constant(H) 0.5 s Friction coefficient(F) 0.05479 pu DC-link capacitance 5e–3F DC-link voltage 1200 V

*Predictive Direct Torque Control Strategy for Doubly Fed Induction Machine for Torque…*

The performance of proposed control strategy of DFIM is analyzed for steady state and transient conditions. For the transient conditions, the step change in electromagnetic torque i.e., from 0.4 pu to +0.4 pu at 0.6 s is considered. That means, from generator mode (negative torque) to motoring mode (positive torque), with constant switching frequency of 1 kHz, with speed reference of 1350 rev/min, and DC-link voltage of 1200 V. The DFIM is under steady state

chronism of DFIM are examined, which are given in three subsections.

**5.1 Transient and steady state analysis of DFIM**

*Specifications of DFIM and wind turbine.*

**Doubly fed induction machine**

*DOI: http://dx.doi.org/10.5772/intechopen.89979*

**Wind turbine**

**Table 4.**

**109**
