BuckOpen
Inverter1phOpen
Inverter1phOpenSynch
Inverter1phClosed
Inverter1phClosedSynch
PVInverter1ph
PVInverter1phSynch
USBBatteryConverter
More complete application examples
Extends from Modelica.Icons.ExamplesPackage (Icon for packages containing runnable examples).
| Name | Description |
|---|---|
| BuckOpen
|
Ideal open-loop buck converter |
| Inverter1phOpen
|
Stand-alone 1-phase open-loop inverter with constant DC source |
| Inverter1phOpenSynch
|
Grid-tied 1-phase open-loop inverter with constant DC source |
| Inverter1phClosed
|
Stand-alone 1-phase closed-loop inverter with constant DC source |
| Inverter1phClosedSynch
|
Grid-tied 1-phase closed-loop inverter with constant DC source |
| PVInverter1ph
|
Stand-alone 1-phase closed-loop inverter with PV source |
| PVInverter1phSynch
|
Grid-tied 1-phase closed-loop inverter with PV source |
| USBBatteryConverter
|
Bidirectional converter for USB battery interface |
PVSystems.Examples.Application.BuckOpen
Ideal open-loop buck converter
This example compares two implementations of a buck DC-DC converter. The switched version is built using mostly blocks from Modelica's electrical library but also includes the SwitchingPWM model. The averaged version is built around a replaceable instance of the average switch model for CCM (continuous conduction mode) and DCM (discontinuous conduction mode) considering no losses.
This example showcases how components from PVSystems can be mixed with components from the Modelica Standard Library to build systems that might be of interest. Additionally, it aims validating the average switch model performance by comparison with the more accurate/detailed switched model.
This is still an open-loop system. A duty cycle value is fed to the SwitchingPWM block to drive the ideal closing switch or to the averaged switch network model. The duty cycle value begins at 0.1 and changes to 0.6 in the middle of the simulation. The effect of this change can be observed by plotting the output voltages:
The output voltage for both implementations is not exactly the same but it can be seen that the averaged model provides a very decent approximation. This is the case because both the switching and the averaged implementations are neglecting losses and because they are both correctly modelling CCM and DCM modes. The converter is operating in DCM in the first interval and in CCM in the second:
An interesting exercise to complete this example would be to build a controller to close the loop and study the system's behaviour.
Extends from Modelica.Icons.Example (Icon for runnable examples).
| Type | Name | Default | Description |
|---|---|---|---|
| CCM_DCM1 | sn | redeclare Electrical.CCM_DCM... |
PVSystems.Examples.Application.Inverter1phOpen
Stand-alone 1-phase open-loop inverter with constant DC source
This example presents two implementations of an open loop 1-phase inverter. The function of the inverter is to convert DC voltage and current into AC voltage and current. To keep things simple, a constant DC source is included on the DC side and an RL load is included on the AC side. Typically, inverters are placed inside a more complicated setup, which might require MPPT (Maximum Power Point Tracking) on the DC side when connected to a PV array and AC synchronization when connected to a grid on the AC side instead of just a simple passive load.
Nevertheless, the example still showcases an interesting application. Upon running the simulation with the provided values, plotting the resistor voltages yields the following figure:
The AC is achieved with the inverter topology (called an H-bridge) as well as with the duty cycle sinusoidal modulation. Have a look at the duty cycle driving the SwitchingPWM block and compare it with the voltage drop in the resistor.
Compare it with the voltage drop in the inductor. The voltage coming out of the inverter is actually a square wave and the inductor is providing some crude (but enough for some applications) filtering. Play around with the value of the inductor to see how it provides a better or worse filtering performance (decreasing or increasing the voltage and current ripple in the resistor, which in this example is assumed to be the load being fed). Since this is an open loop configuration, it will also change the peak value of the voltage drop in the resistor, as well as its phase.
Importantly, see how the the average model provides a very good approximation for low frequencies. This kind of model won't be useful to study ripples and to evaluate the performance of different PWM modulations (sinusoidal modulation is being used in this example) or of different filter configurations, since those are concerned with the high frequencies in the system. On the other hand, the average models will be very useful to study controllers and to perform longer simulations since the simulation step doesn't need to be so small as to accurately represent the switching dynamics.
Extends from Modelica.Icons.Example (Icon for runnable examples).
PVSystems.Examples.Application.Inverter1phOpenSynch
Grid-tied 1-phase open-loop inverter with constant DC source
This example goes a step further than Inverter1phOpen and includes grid synchronization. Typically this is the condition for inverters in real-life situations. Both switched and averaged implementations are presented for comparison purposes and it can be seen that they both provide very similar results (excluding the fact that high frequencies are left out in the averaged model).
Since this is still open-loop and there's no in-quadrature separation, the value of the current can't comfortably be specified to be of a certain value. Since the RL load has almost equal real and imaginary parts, the current that is drawn from the inverter has a power factor different than one.
A key value to pay attention to in this example is the gain that is placed in the Add block.
It's initially set at 0.5. The value is expressed as 580/580/2 to highlight the fact that this gain should be normalized to the DC voltage value. Above that, over-modulation will occur and the output current of the inverter will become quite ugly. Play around with this value (using values between 0 and 0.5) to see how the output current of the inverter changes.
Extends from Modelica.Icons.Example (Icon for runnable examples).
PVSystems.Examples.Application.Inverter1phClosed
Stand-alone 1-phase closed-loop inverter with constant DC source
This example explores a closed-loop inverter. No grid is present, which simplifies things. But, since the controller is implemented in the synchronous (dq) reference frame, a synchronization source needs to exist. This is implemented with the saw tooth generator, which emulates the output of the PLL.
As can be seen in the following figure, one can now comfortably specify the setpoint for the output current of the inverter:
Having the posibility to separately control the current in each dq axis enables one to control the power factor (i.e. the phase lag between the voltage and the current) as well as the amplitude of the current.
In this example, the equivalent synchronization signal is plotted to see this phase shift as the setpoints change. Notice how, when the q component of the current is 0, the d component is equal to the peak current.
Extends from Modelica.Icons.Example (Icon for runnable examples).
PVSystems.Examples.Application.Inverter1phClosedSynch
Grid-tied 1-phase closed-loop inverter with constant DC source
This example includes a voltage source on the AC side. This will add the synchronization challenge for the controller: in order to provide adequate control of the output current, the duty cycle needs to be carefully in synch with the AC grid voltage.
Plotting the current through the load, the dq setpoints, the grid voltage and the actual computed d value of the current yields the following graph:
After an initial period where the signals are reaching their steady-state values, the current successfully reaches the setpoint value. Since the q setpoint is equal to zero, the output current stays in phase with the grid voltage and the d setpoint value equals the peak current value.
Extends from Modelica.Icons.Example (Icon for runnable examples).
PVSystems.Examples.Application.PVInverter1ph
Stand-alone 1-phase closed-loop inverter with PV source
This example adds a PV array to the DC side. To start as simple as possible, the AC side is just a passive RL load. A general controller for this kind of setup is devised and packaged as Inverter1phCompleteController. This block accepts no input because it's assumed that the controller will try to extract the maximum active power from the PV array. Internally, the q current setpoint is set to zero.
Plotting the DC bus voltage and the output current confirms shows that this is in fact how the controller is behaving:
The maximum power point is achieved by indirectly balancing the difference between the power delivered by the PV array and the power dumped on to the grid. As the maximum power point is being reached, the difference tends to zero:
Extends from Modelica.Icons.Example (Icon for runnable examples).
PVSystems.Examples.Application.PVInverter1phSynch
Grid-tied 1-phase closed-loop inverter with PV source
This example represents a simple yet complete grid-tied PV inverter system. A long simulation is performed so as to visualize the time evolution of the MPPT control, which is necessarily much slower than the output current control. This long simulation time is manageable because an averaged switch model is being used, which means that the simulation can have longer time steps.
This evolution can be observed by plotting the DC bus voltage as well as the input and output power to the inverter:
As expected, the power factor of the output power is 1 (all active power), having the output current in synch with the grid voltage:
Extends from Modelica.Icons.Example (Icon for runnable examples).
PVSystems.Examples.Application.USBBatteryConverter
Bidirectional converter for USB battery interface
A battery, simulated with a controlled voltage source in series with a small resistance, is interfaced with a USB device, simulated with a resistive load. The converter is a component included in the Electrical.Assemblies package.
This example is borrowed from EMA16. The application is not that related with photovoltaics, but provides a good showcase of the power electronics models in this library. The converter is specified to have three operating modes:
An efficient solution to these step-down and bidirectional step-up requirements is a non-inverting buck-boost converter with bi-directional switches operated in a buck/boost modal fashion (i.e. the boost switches are disabled while in buck mode and vice versa). A possible solution to these requirements using this topology is expressed through the parametrization of CPMBidirectionalBuckBoost:
This converter model includes both the electrical and control components of a Current-Peak Mode controlled modal non-inverting buck-boost. The default stop time is set at 20 seconds. Running the simulation and plotting the output voltage and current produces the following result:
Extends from Modelica.Icons.Example (Icon for runnable examples).