Merge branch 'restructure/classes' into dev

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# especially if it merges an updated upstream into a topic branch.
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Author: SabineHaas

windpowerlib/wind_farm.py

@@ -219,6 +219,15 @@ def assign_power_curve(self, wake_losses_model='power_efficiency_curve',
                     power_curve['wind_speed'], power_curve['power'],
                     standard_deviation_method=standard_deviation_method,
                     block_width=block_width, **kwargs)
+            else:
+                # Add value zero to start and end of curve as otherwise there can
+                # occure problems at the aggregation.
+                if power_curve.iloc[0]['wind_speed'] != 0:
+                    power_curve.loc[power_curve.index[0] - 0.5] = [
+                        power_curve.index[0] - 0.5, 0.0]
+                if power_curve.iloc[-1]['power'] != 0.0:
+                    power_curve.loc[power_curve.index[-1] + 0.5] = [
+                        power_curve.index[-1] + 0.5, 0.0]
             # Add power curves of all turbine types to data frame
             # (multiplied by turbine amount)
             df = pd.concat(
@@ -239,7 +248,7 @@ def assign_power_curve(self, wake_losses_model='power_efficiency_curve',
                 standard_deviation_method=standard_deviation_method,
                 block_width=block_width, **kwargs)
         if (wake_losses_model == 'constant_efficiency' or
-                wake_losses_model == 'wind_efficiency_curve'):
+                wake_losses_model == 'power_efficiency_curve'):
             wind_farm_power_curve = (
                 power_curves.wake_losses_to_power_curve(
                     wind_farm_power_curve['wind_speed'].values,