CONCLUSIONS AND FUTURE WORK
5 CONCLUSIONS AND FUTURE WORK
Controller lab tests
In the Chapter 3, some simulations were presented. The controller seems to be correct and stable. We suppose that some lab tests can now be achieved with a grid connected converter with simple resistive load. The Simulink file prepared for implementation may need to be slightly modified but the idea was presented in Chaper4 with some key point to run an experiment with dSpace. A tutorial is available at the reference  .
In this report, a simple stability analysis have been done. Nevertheless, this analysis is quite simplistic (with approximations) and have been realized in continuous time only. It should be also complete in discrete time because the controller is implemented in discrete time.
As we explain in the first part (2.4.3 Dead time effect), the performances of the converter are affected by injection of deadtime in the PWM signals to avoid short circuit of the DC link. We suppose that some simulations of this deadtime and some compensation should be done before testing the controller in the laboratory.
The modulation method could be improved. In our system, we decided to implement a sinusoidal Pulse Width Modulation mainly for its simplicity and acceptable performances. We advice to test it in the lab. Nevertheless, a simulation with Space Vector Modulation (SVM) should be also simulated and a deep comparison to sinusoidal PWM could be done. The SVM is known for its effectiveness, simplicity for implementation, harmonics reduction.
A last possible improvement could be done by implementing a Virtual Flux Oriented Control (VFOC). It could improve the performance under non ideal line voltage conditions. Furthermore, this method could be useful if a machine is added to the model (AC side) because machine models are generally done with flux oriented reference.
We also advice to implement a load current controller. Reading some papers, we saw some battery charger configuration with another stage after the rectifier (on more leg with two IGBTs for DC DC conversion). A load current controller was responsible of the switches for this stage ( ).