Location

This example model can be found in the software under the FACTS & HVDC > FPGA-BASED_Active_Power_Filter.ecf.

Description

Active Power Filter (APF) is a static power converter used to filter the harmonics present in the grid. APF achieves this by supplying harmonic current to the load hence eliminating the supply of harmonics by the grid. A typical APF consumes very little active power from the grid (only an amount equal to the resistive losses) and generates the harmonic current of the tuned frequency. 

Here, in this example, a standard two-level shunt active power filter using an IGBT switch parallel with the diode is represented. The load consists of two diode rectifiers which are phase-shifted by 30 degrees. The rectifier load connected to the circuit followed by the Delta-Y transformer is plugged in via circuit breaker only after 10 cycles to change the load from 6-pulse to 12-pulse.

The model runs only in real-time with an active power filter simulating at the FPGA time step and the controller with the rest of the network at the CPU time step which is 14micro-sec. The active power filter circuit implemented in FPGA is presented here.

Controller

The Hysteresis current control is used here to supply the harmonic currents as required by the load. The controller uses a three-phase PLL to generate a reference sinusoidal source current which is in-phase and has the same RMS gain as the load current.  The error between these two which is the required load harmonic current is provided by the APF by using hysteresis switching at the point of common coupling. Ultimately, the APF injects harmonic current and eliminates the source from the supply of harmonics.

Simulation and Results

This example model is built on OP5707 real-time simulator which has Virtex 7 FPGA.  Start the model by choosing the target which fits the mentioned configuration and in real-time mode.  While running the model in real-time, open the scope view window, Goto File – Open Template – and choose the template which is available in the model folder location( For example:  ....\HYPERSIM\FPGA-Based_Active_Power_Filter\FPGA-Based_Active_Power_Filter.svt) and click on play to see the results.

The results displayed here present the load and source currents and their THD for a fundamental frequency of 60Hz. Load current has a THD of 21% whereas the source has ~10% only. Here the load is a single diode bridge rectifier (acting like a 6 pulse converter). 

The results displayed here present the load and source currents and their THD for a fundamental frequency of 60Hz. Load current has a THD of 5.2% whereas the source has 4.8% only. Here the load current THD looks smaller in value as the load is a dual rectifier (acting like a 12 pulse converter). 

References

Three-Phase Active Harmonic Filter - MATLAB & Simulink - MathWorks India

See Also

Examples | FPGA-Based PMSM Drive