Dual Active Bridge with Pulse Width Modulation based on Signal Processing

Demonstration of the functionality and normal operation of the Dual Active Bridge with Signal Processing based PWM example

Introduction

The Dual-Active Bridge (DAB) Converter is an attractive topology because of its high-power density, efficiency, reliability, and galvanic isolation. DAB is a bidirectional DC/DC converter based on two single-phase inverters interlaced through a high-frequency transformer and an energy transfer inductance. In a real DAB application, this inductance is often regarded as leakage inductances of the transformer. Because of its qualities it is widely used, from uninterrupted power supplies (UPS), power converters for the energy storage management system, to electric vehicles.

Figure 1: DAB topology

The typical control principle, which is implemented in this model, is based on changing the phase difference between carrier signals for two inverters while keeping the same duty cycle. By changing the phase shift, we obtain a wide range of output voltages, as well as control over the power flow direction.

Model description

The DAB converter consists of two Single Phase Inverters placed in opposition. Between them is an Ideal Transformer with a 1:1 turns ratio. There are inductances and the resistance of the transformer on both sides, while on the source side there is also a series capacitor. The purpose of this capacitor is to remove DC currents at the primary winding of the transformer. At the output of the converter, there is a capacitor to reduce the output voltage ripple.

Figure 2: DAB converter

While the DAB converter is simulated on FPGA, its control is simulated on User CPU. The control of the DAB converter is conducted with the Signal Processing Library using a default execution rate of 5µs. This control can be separated in three logical parts – the modulation signal generator, and the carrier signals generator and the gate signals generator.

The modulation signal generator is a simple constant block with a predefined value which does not change during simulation.

Figure 3: DAB control

The second large part of the control is the carrier signals generator, which provides the carrier signals necessary for control of both inverters. This part takes inputs in the form of a SCADA Input component. The SCADA input allows for changing the Control mode in HIL SCADA while the simulation is running, between open-loop control and closed-loop control. If open-loop control is chosen, an Angle value is needed as an input. If closed-loop control is chosen, then the desired reference voltage output is needed. This voltage reference is then compared to the measured output voltage, and any deviations are controlled by the PI regulator. The PI regulator then provides an Angle value as an output. Regardless of the Control mode, carrier signal generation will take an Angle value as an input.

The main part of the carrier signals generator is the C function block. This block generates two carrier signals which are shifted for the value of the scaled angle value. These carrier signals are triangular and their frequency is the same – 1000Hz.

Third part of the control is gate signal generation. In this part, carrier and modulation signals are compared and gate signals are generated. The transport delay component in this part introduces dead-time.

Table 1. HIL device resource utilization
No. of processing cores 1
Max. matrix memory utilization 38.33 [%]
Max. time slot utilization 42.5 [%]
Simulation step, circuit solver 1 [µs]
Signal processing execution rate 5 [µs]

Simulation

This application comes with a pre-built SCADA panel (Figure 4). The panel offers most essential user interface elements (widgets) to monitor and interact with the simulation in runtime. You can customize it freely to fit your needs. Additionally, you can use the panel to modify the input voltage of the converter, or change the type of control to affect the output voltage.

Figure 4: SCADA panel during simulation

As already mentioned, the control mode determines which angle value is taken into consideration during carrier signals generation. If you choose the Closed-loop control mode, then you can set a reference for the output voltage (which is also an input of the PI regulator). On the other hand, you can pick the Open-loop control mode to directly set the Phase-shift angle. When the Open-loop control mode is chosen, then reference output voltage value does not affect carrier signals generation and vice versa.

When you change the angle value to a larger value in an open-loop, the phase shift between carrier signals increase. This can be observed in Figure 4. The same process will happen if you change the reference output voltage, while the control mode is closed-loop. This can be observed in Figure 5.

Figure 5: DAB Converter in open-loop response on Phase-shift angle change

Figure 6: DAB Converter in closed-loop response on output voltage reference change

Table 2. Minimum requirements
Files
Typhoon HIL files

examples\models\general power electronics\dab with sp based pwm

dab with sp based pwm.tse

dab with sp based pwm.cus

Externals*
Min. HW requirements
No. of HIL devices 1
HIL device HIL402

Test automation

We don’t have a test automation for this example yet. Let us know if you wish to contribute and we will gladly have you signed on the application note!

Authors

[1] ‪Prof. André Luís Kirsten, Dr. Eng.

[2] Prof. Roberto Francisco Coelho, Dr. Eng.

[3] Thiago Antônio Pereira, Msc. Eng.

[4] Felipe Jung, Msc. Eng.

[5] Dimitrije Jelić