What actually are harmonics? Where do they come from? How do the impact the system, particularly the grid? What are the solutions for minimization of harmonics?
This and more in the “Network harmonics” category!
VFD compliance with voltage and current harmonic limits National and international standards provide guidelines and limits for individual harmonics and total harmonic distortion. But how to assess the situation when the VFD meets the limits for voltage harmonics while current harmonic limits are exceeded? This blog post is a short Read more…
Ratio between grid short-circuit power and VFD installed power Successful integration of a variable frequency drive (VFD) into the electric grid shall follow certain rules. Moreover, the VFD shall comply with standards related to power quality and harmonics. In case of 4-quadrant operation (regenerative type of VFD), additional requirements typically Read more…
How does skin effect impact the drive system? This short article provides a brief description of the skin effect and its impact on a drive system. As it will be explained, the skin effect influences the system in both negative and positive way. It always depends on the point of Read more…
Triplen harmonics – A devil in your network software tool? This blog post addresses potential “issues” with triplen harmonics when performing a network harmonic study. Positive, negative and zero sequence The theory of symmetrical components tells that a periodic signal can be decomposed into harmonics of positive, negative and zero Read more…
How do system parameters impact the grid harmonic distortion? VFD as a non-linear load produces harmonics that are injected into the grid and cause harmonic distortion. The level of harmonic distortion depends on the type of VFD, specifically the rectifier topology. However, it is also strongly affected by the parameters Read more…
What factors shall be considered when designing a harmonic filter? Most modern variable frequency drives (VFD) have so high power quality that they comply with the corresponding standards without the need for additional harmonic filtering. Nevertheless, there are cases where a filter is recommended or necessary. The consequent questions are: Read more…
How does a grid harmonic filter work? Recently we got a question in our chat group: How does a grid harmonic filter work? It sounds like a very basic question. However, since many people struggle to imagine the flow of harmonics in the system (it is fairly abstract thing) it Read more…
Types of harmonics How can we classify harmonics? What types of harmonics do we know? That is a subject of this short post. Different literature sources mention various classification. We just list here several categories based on our own practice. A) According the relation of the harmonic frequency to the Read more…
What does the X/R ratio tell us? In one of our previous posts we have talked about “purely inductive grid”. That is certainly a special case of oversimplification. Keeping it still very simple we may use “resistive-inductive grid”. The relationship between the resistive and reactive component is particularly interesting. What Read more…
Active filter or AFE drive – What is a better option? When taking care of grid harmonics there are several technical solutions to choose from. You might stand in front of a dilemma: active filter or AFE drive? What is a better choice? Nowadays there are multiple approaches how to Read more…