Set sort=False in power curve smoothing

Author: SabineHaas

windpowerlib/wind_farm.py

@@ -263,13 +263,14 @@ def assign_power_curve(self, wake_losses_model='power_efficiency_curve',
                     power_curve = pd.concat(
                         [pd.DataFrame(data={
                             'power': [0.0], 'wind_speed': [0.0]}),
-                         power_curve], sort=True)
+                         power_curve], sort=False)
                 if power_curve.iloc[-1]['power'] != 0.0:
                     power_curve = pd.concat(
                         [power_curve, pd.DataFrame(data={
-                            'power': [0.0],
-                            'wind_speed': [power_curve['wind_speed'].loc[
-                                               power_curve.index[-1]] + 0.5]})])
+                            'power': [0.0], 'wind_speed': [
+                                power_curve['wind_speed'].loc[
+                                    power_curve.index[-1]] + 0.5]})],
+                        sort=False)
             # Add power curves of all turbine types to data frame
             # (multiplied by turbine amount)
             df = pd.concat(