Power Electronics Development Center
hi ,need some help with grid tied inverter+grid
Agreed. There are 3-phase inverter + line reactor filter models included in the Power Electronics Design Guide.
Also see the new NI Power Electronics Control Design V Training Workshop for the latest 3-phase inverter control code and Multisim models (including switching/conduction losses and temperature in the case of the 3-phase induction motor co-simulation).
For the older Power Electronics Design Guide examples, keep in mind that they were written before the release of the LabVIEW FPGA Desktop Execution Node. Now you simply right-click on the FPGA target, set it to simulation mode, and you can run the FPGA control application in simulated time that's automatically step-by-step synchronized in closed loop with the Multisim power electronics simulation, as shown below.
To enable high fidelity co-simulation, the LabVIEW FPGA Desktop Execution Node interfaces to the LabVIEW FPGA Application while the Multisim Co-Simulation Interface connects to the power electronics circuit model. A desktop testbench application is shown above.
The Multisim power electronics circuit (top image below) and LabVIEW FPGA control application (bottom image below) are co-simulated with a common sense of simulated time.
Regarding your #3 question on grid source and transformer models, in Multisim right-click on the schematic, go to Place Component, and then browse to Sources where you will find 3-Phase Wye and 3-Phase Delta Sources. For transformers, go to Basic>TRANSFORMER, as shown below.
For transmission lines, go to Misc components, as shown.
I've attached a few examples that demonstrate these components.
1. Transmission line with recloser circuit breaker. The recloser vacuum breaker switch closes at 7 milliseconds, reconnecting power to the 30 km transmission line. Study the transient effects at each end of the transmission line. The grid source is 20 kV rms.
2. The three-phase delta and wye grid sources are demonstrated by this 3-phase squirrel cage induction motor simulation. Notice that the simulation results are a reasonably good match to the BlackMax Y535 motor datasheet parameters (power factor, phase current, speed/slip) when the motor is operated at the rated torque (3 lb*ft) and under no load. (The motor datasheet parameters are normally a bit pessimistic, meaning more current and slip, than a simulation so the vendor can account for manufacturing tolerances.) To change the load torque, move the slider or use the A key.
To change the grid from a 3-Phase Wye source to a 3-Phase Delta source for the grid, change the circuit Variant (see bottom left corner of screenshot or go to Tools>Variant Manager). Note that the motor response does not match the datasheet when using a Delta-connected grid source, as we would expect.
3. Two types of 3-phase inverter models are demonstrated with the circuit below. This circuit topology matches the mini-scale power converter training/research board (an open source circuit design you can modify to meet your R&D needs), assuming the DC link contactor is closed.
On the left (inverter A) we have a MotorSolver 3-phase induction motor connected. For this 3-phase inverter, we are modeling the switching/conduction losses and transient temperature of the STGIPS10K60A six-pack IGBT intelligent power module. On the right (inverter A) we have a 3-phase line reactor filter connected, as is common for grid tied power converters. For this 3-phase inverter, we are using basic IGBT/Diode model that includes turn on voltages, forward voltage drop and conduction resistance but no loss/thermal modeling. For a co-simulation example, see the NI Power Electronics Control Design V Training Workshop code.
All three of these Multisim simulation models are attached. BTW, if you are looking for a 3-phase transformer let me know.
