I am working on the project 'Power quality improvement using D-STATCOM' using MATLAB SIMULINK and willing to learn more about it. I need little bit of guidance from your side. I am trying to reduce harmonic in the system using DSTATCOM and have already achieved power factor correction using DSTATCOM. kindly guide me that which factor exactly affects the reduction of harmonics in the electrical system using Synchronous reference frame theory. Kindly suggest me where am i going wrong in this model? PFA. Thanks.
Hi S. Ved
Try to use a phase locked loop (PLL) in the control loop. RMS neutral current, total harmonic distortion and Non fundamental apparent power can be used to check the degree of harmonic pollution.
I think you'll find the DSTATCOM controller is designed to produce fundamental frequency current (with minimal harmonics). Obviously you could re-design the controller, but is that what you want to use it for? There are many cheaper ways to filter out harmonics.
The harmonic components in AC system come from the nonlinear load. Therefore, you need to detect the harmonic level by a filter, FFT...(There are many methods out there) Then, D-STATCOM will inject the harmonic current component to compensate it depend on the level of harmonic level existing on your system.
The harmonic component can be 3rd, 5th, 7th, 11th... order of your fundamental component. If you use Synchronous Reference Frame theory, you can detect them by using 3,5,7... order frequencies to detect it. To regulate the injecting current, you can use PI controller if in dq frames, PR controller if in alpha-beta frames.
Regards!
Thanks for the response
I had used and tunned in PI controller to gain the power factor improvement. Also i had attached non linear load and has imposed harmonics in the system from programmable voltage source in order to check the working of DSTATCOM in case harmonic reduction.
Also I tried changing the values of selected bandwidth for the hysteresis control and got these results.
When I decreased the value of bandwidth between +0.1e-4 to -0.1e-4 (or less), the pf of the system remained somewhere same but it did not effect the THD of the system, whereas when I tried doing opposite i.e., kept the value of bandwidth between +1000 to -1000 (or above) the THD of system reduced to 4.3% from 6.9% but also reduced to 0.3. Kindly suggest what should I do for this. Sending you the FFT analysis along with it. PFA
Dear Sumeet Ved,
The factor contributes to effectiveness of SRF algorithm is the setting of low-pass filter (LPF) that is commonly applied in detecting the fundamental component in dq frame. For better filtering performance of LPF, its cutoff frequency should be set at lower value. Meanwhile, for better transient performance, the cutoff frequency should be set at higher value. Hence, a good compromise between filtering and transient performance of LPF is needed for optimum performance of the SRF algorithm.
If the setting of LPF is good, then focus on the behavior of the generated reference current signal. It is important to make sure that the generated reference current is correct as the STATCOM operates based on its characteristics.
If the reference current is correct, then focus on DC-link voltage regulation. The DC-link voltage must be maintained at suitable level and should contain least ripples. The ripples will affect the mitigation performance of STATCOM as well.
Lastly, the output filter (simple L filter is commonly applied) connected to the STATCOM. The value chosen for the output filter must be compatible with the reference DC-link voltage. Try using 5mH or 3mH L filter.
Hope the information is helpful to you.