# Deep Learning Method for Fault Detection of Wind Turbine Converter
## 2 Generation of Radar Chart
### Radar Chart Drawing  
The SCADA system data of wind turbines were collected from two-year operation data of 27 wind turbines in a wind farm in Hebei Province, China, which was put into operation in 2012. Before proceeding to draw radar charts, the fault indicator variables  
Figure 1: The research workflow diagram. must be determined. The function of the converter in the operation control of a wind turbine is illustrated in Figure 2. The converter plays a role to make sure that the output power complies with the requirements of grid. It ensures that the output voltage is in a threshold range and the current frequency is in accordance with the grid. The output power of the generator is under control through adjusting the blade angle by a pitch control system. According to an investigation and analysis, the grid-side converter voltage, generator torque set-point, active and reactive power, wind speed, turbine rotor position and generator rotor speed are selected as the fault indicators of the converter. Wind speed is measured by wind sensor standing on the top and rear of wind turbine nacelle. Turbine rotor position and generator rotor speed are measured, and the other parameter values are recorded in wind turbine operation. With the SCADA system data, one can extract the data 30 min, 3 h, 24 h, 7 days or 15 days ahead of occurrence of failures and put the data into a design Excel table. Table 1 shows an example of the fault indicator variable data which are 24 h ahead of a converter failure. Each table, like Table 1, has 181 rows of data, and a total of 100 sets of data were extracted for study in this paper; the extracted normal operation data were in the same sample size as the failure data set. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Serial No.**} & **Wind** & **Turbine Rotor** & **Active** & **Reactive** & **Generator** & **Grid Side Converter** & **Generator Torque** \\  & **Speed** & **Position** & **Power** & **Rotor Speed** & **Voltage** & **Set-Point** \\  & **(m/s)** & **(\({}^{\circ}\))** & **(\({}^{\circ}\))** & **(\({}^{\circ}\))** & **(\({}^{\circ}\))** & **(\({}^{\circ}\))** & **(\({}^{\circ}\))** & **(\({}^{\circ}\))** \\ \hline \(1\) & 4.90 & 77.43 & 233.4 & \(-\)33.257 & 1176.1 & 0 & 22.881 \\ \(2\) & 4.70 & 38.41 & 259.2 & \(-\)36.933 & 1216.6 & 0 & 24.539 \\ \(3\) & 4.92 & 117.51 & 256.2 & \(-\)41.666 & 1213.4 & 0 & 24.362 \\ \(4\) & 6.49 & 98.96 & 288.6 & \(-\)27.281 & 1262.3 & 0 & 26.401 \\ \(5\) & 4.61 & 191.34 & 328.8 & \(-\)31.396 & 1319.5 & 0 & 28.632 \\ \(\cdots\) & \(\cdots\) & \(\cdots\) & \(\cdots\) & \(\cdots\) & \(\cdots\) & \(\cdots\) & \(\cdots\) \\ \(179\) & 5.44 & 30.76 & 271.8 & \(-\)44.461 & 1241.6 & 3.276 & 25.489 \\ \(180\) & 4.46 & 166.38 & 180.0 & \(-\)35.734 & 1079.2 & 0.536 & 19.261 \\ \(181\) & 4.42 & 74.27 & 224.4 & \(-\)25.718 & 1163.8 & 0.236 & 22.596 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Sample of fault indicator variable data of converter. Figure 2: Schematic of wind turbine control system diagram. (**1**) Rotor; (**2**) main shaft; (**3**) gearbox; (**4**) brake system; (**5**) pitch control system; (**6**) generator; (**7**) power control to the grid; (**8**) low voltage switchgear; (**9**) low voltage switchgear; (**10**) converter system; (**11**) generator side converter; (**12**) grid side converter; (**13**) on/off switch control; (**14**) transformer; (**15**) high voltage switchgear; (**16**) wind turbine controller. The specific steps for drawing a radar chart in this paper are as follows:  
The first step is to select the wind speed index as the drawing reference;  
The second step is to normalize the fault indicator variable values representing the converter operation condition status;  
Step 3 is to collect all fault indicator variable values with a determined wind speed, and draw the 7 indicator variable values on a radar chart;  
Step 4 is to draw a closed heptagon through the 7 points on the 7 axes representing the seven fault indicator variables.