Location

The wind power example model can be found in the Artemis installation folder:

C:\OPAL-RT\ARTEMIS\[ARTEMIS version]\common\Examples\SmartInverterLib_wind

Description

Model

In this example model, a three-phase two-level inverter is used to inject active and reactive power to an AC voltage source that symbolizes a weak grid. The figure given below depicts the high-level block diagram of the example model: 

The DC side of the inverter contains a 13.2 kW SG which is the primary energy source, followed by a three-phase diode driven full-bridge rectifier and a boost converter. The SG generates AC power according to the wind speed, which is subsequently transformed into DC, using the rectifier. The control of the boost converter and the pitch angle controller are synchronized so that the speed remains at 1 pu and maximum power can be extracted. Details of the boost converter and the pitch angle controller can be found here [1]. The primary active power control method at the Primary Control block is set to “DC link” so that the DC link voltage is maintained to the reference value by extracting necessary active power from the DC link capacitance.

Based on the functionality, the controller is divided into four subsystems. The first subsystem corresponds to the Signal Conditioning unit, which measures the signals of interest, filters and conditions them to per-unit values as required by the subsequent controllers. Afterwards, the Secondary Control block generates the active and reactive power references, necessary to implement the grid support functions presented in the IEEE std. 1547-2018 [2]. Next, the Primary Control block generates the reference signals corresponding to active and reactive components of the output current. At last, the Wave Reference block is used to generate the reference signal to drive the two-level converter. In this example, an average converter model is used, and therefore, the reference signal is the duty ratio.

At the output of the two-level converter, an LCL filter is used to reduce high-order harmonics generated by the switching dynamics of the conversion process. The output of the filter is then connected to the main grid. The grid supply is emulated using a programmable voltage source whose voltage reference is altered to represent changing dynamics.  

Scenarios

The example model is intended to introduce different dynamic changes to the system presented in the previous section to show the effectiveness of the Smart Inverter toolbox and its associated control blocks. The Secondary Control block is configured to maintain the grid voltage at the nominal value by injecting necessary reactive power and have priority for reactive power over active power injection. The controller is not supposed to take any corrective action as long as the grid voltage deviation is within pu around its nominal value. For voltage deviation beyond the acceptable range, the controller adjusts its reactive power dispatch to compensate the voltage deviation. Refer to the supplementary MATLAB code to obtain the control parameters and nominal values used in the example model. The following dynamic changes are introduced to the example model to observe the effectiveness of the controller under varying grid conditions:

1. At t= 5 seconds, a 0.1 pu voltage sag on the grid voltage.
2. At t= 7 seconds, the grid voltage came back to the nominal value.
3. At t= 9 seconds, a 0.1 pu voltage swell on the grid voltage.
4. At t= 11 seconds, the grid voltage came back to the nominal value.
5. At t= 13 seconds, a 0.02 pu voltage sag on the grid voltage.
6. At t= 15 seconds, the grid voltage came back to the nominal value.
7. At t= 17 seconds, a 0.02 pu voltage swell on the grid voltage.
8. At t= 19 seconds, the grid voltage came back to the nominal value.
9. At t= 21 seconds, the wind speed increased from 9 to 11.5 m/s.

Simulation and Results

The following figure shows the simulation results of the example model:

At t=5s, the big sag in the grid voltage drives the controller to adjusts its reactive power injection. Immediately, following the disturbance, the controller follows the reference and compensate voltage deviation. At t=7s, the grid voltage goes back to nominal and the controller stops exporting reactive power. At t=9s, the voltage swell forces the controller to start consuming reactive power and it keeps continuing until t=11s when grid voltage comes back to the nominal, again. At t=13s and t=17s, there is 0.02pu voltage sag and swell, respectively, but as voltage remains withing the normal operating conditions, the controller does not initiate any corrective measures and reactive power dispatch remains unchanged. At t=21s, a wind speed increase from 9 m/s to 11.5 m/s, subsequently increases the active power dispatch, however, due to the decoupled control of active and reactive power, reactive power dispatch from the inverter remains unchanged.

References

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