The HIL accelerates the test cycle and avoids the problem of hardware damage when testing the controller with the real equipments.

 ——Professor Deng Xiangtian, Wuhan University of Technology

Requirements

Electrical Engineering Department of Wuhan University of Technology (WUT) aims to build a platform to do the research of active power filter control, but using nonlinear load built with the real resistor, inductor and rectifier bridge needs too much time and is easy to damage the hardware during the test process. So it's better to test the controller through a real-time digital simulation system, which is known as the Hardware-In-the-Loop Testing.

Challenges

The mian circuit topology of the APF presented in this case is shown as below:

The topology consists of the power grid, the uncontrolled rectifier load (the harmonic source) and the APF-based on the two-level bridge and LCL filter. A soft start circuit is also included in the APF system. The harmonic current of the load is compensated by the current of the two-level bridge of APF.

In order to simulate the real power electronics devices, the simulation system needs to compute the main circuit with the time step of less than 1 microsecond, which is really difficult to achieve. ModelingTech Energy Technology Co., Ltd leverage the latest FPGA techbology and modeling method  to build up the real-time simulation system. This simulator has two distinct features, it can simulate the arbitrary power electronics topology with the detailed switch model approach, it is also able to simulate the power electronics system with the step size around one microsecond. These features make ModelingTech simulator perfectly match requirements of this APF project. 

Notes: The detailed model of power electronics refers to modeling each power electronic switch independently (the big/small resister model or the L/C model). The state of each switch is only determined by its own voltage, current and control signal. The whole circuit model is formed according to the system topology. So the detail model approach can support the arbitrary topology without any pre-defined assumptions.

APF HIL system based on StarSim and PXI

The system design is shown as below, it contains two main parts: the real-time simulator based on NI hardware and StarSim software，the real APF controller developed by the end user.

The system photo is shown below. The left white box is the power electronic real-time simulator. The controller board in the blue rectangle of right figure is the APF controller developed by the end user.

Experimental Results

The waveforms are the power grid voltage, the nonlinear load current, the power grid current and the capacitor voltage of two-level bridge.

The waveforms without APF compensation are shown as below:

The waveforms with APF compensation are shown as below:

With the waveform comparison, it can be seen that the harmonic current is filtered and the power grid current approaches a sine wave after compensation. The real-time simulation experiment verifies that the APF controller works well.

Please email info@modeling-tech.comfor more information!