An Algorithm for Default Detection of Wind Turbine Generators

*Jigneshkumar P. Desai*

### **Abstract**

The protection of the wind turbine generator (WTG) required discrimination between internal and parallel WTG faults. Furthermore, it must discriminate the fault of its feeder line and parallel feeder line. This chapter describes the protection of wind turbine generators based on fault current and voltage analysis, which can identify the instantaneous operation, delay operation, or immune operation. A proposed Algorithm based digital relay is presented to provide all the different fault detection in a single unit suitable for internal and external fault protection of wind turbine generator. The main challenge to this scheme is that fault resistance may wrongly operate the scheme in some rare conditions. The phase angle of negative sequence current components determines the type of fault. The algorithm used negative sequence current and voltage to positive sequence current and voltage ratio, which is less than the set value in case of external fault. The fault seniors have been explained using simulation results on the wind turbine generator system modeled in a software environment.

**Keywords:** internal fault, feeder, positive sequence current, relay, wind turbine generator

### **1. Introduction**

The parts of the wind turbine generator are shown in **Figure 1**. Blades are connected to this rotor hub. By rotating the motor shaft angle, one can turn the blade's direction, resulting in a change in mechanical power. This rotational mechanical energy rotates the rotor, and by using a gearbox, speed can be changed. By changing the speed, torque will be changed. The frequency of the generated voltage depends on the speed and number of poles. The variable frequency is converted into the constant frequency using a power converter. At this stage, two converters are used. One is an AC-DC converter, and the second is a DC-AC converter called a back-to-back converter. This is often called a gear-less wind turbine generator [2]. As electrical technology is very advanced, mechanical energy to electrical energy can be converted with different machines. Based on this machine used, the wind turbine generators are classified. The most common challenges for the wind turbine are as follows: (1) highly variable wind power injection into the grid, (2) increased penetration of wind energy, (3) Electrically weak distribution network, and (4) heavy reactive power burden by Induction generator (IG).

The classification of wind energy conversion system (WECS) is shown in **Figure 2**. Squirrel cage induction generators (SCIG) are a traditional method, but one cannot

**Figure 1.** *Parts of wind turbine generator adapted from [1].*

get maximum power at different wind speeds. The SCIG is generally known as a fixed-speed wind turbine. At variable rates, wind turbine generators are two types which are gear-less and with gear. Gear-less wind turbine generators may be running at a slower speed, but one can change the number of poles. The wound rotor synchronous generator (WRSG) and permanent magnet synchronous generator (PMSG) is the gear-less wind turbine. The wound rotor synchronous generator (WRSG) and permanent magnet synchronous generator (PMSG) maybe with gear also [3]. Doubly fed induction generator (DFIG), SCIG, wound rotor induction generator (WRIG) with variable rotor resistance also come under the gear category.
