Network harmonics: Software tools
In order to analyze complex networks with multiple elements and various configurations of the grid a sophisticated software tool is unavoidable. Luckily, there are several good products available on the market. In this article we look closer at software tools for network analysis.
In our network harmonic series we have already been talking about where harmonics come from and what are the effects of harmonics on the grid and other consumers [1], how does a characteristic VFD harmonic spectrum look like [2], how to mitigate or minimize harmonics and associated distortion [3] and what types of harmonic filters can principally be used [4]. If you missed any of those articles we highly recommend to revisit them (links at the end). They are built up in a logical way to help understanding the phenomenon of harmonics.
Now it is time to perform a harmonic analysis or a network harmonic study! Let’s look at some of the software tools for network analysis and their features.
Disciplines in power quality and network studies
We start with an overview of disciplines associated with network studies. There is a number of them and at this place we just list the most common ones:
– Load flow analysis
– Short circuit analysis
– Motor starting
– RMS simulations
– Quasi dynamic simulations
– Power quality and harmonic analysis
– Arc flash calculation
– Voltage stability
Network harmonic analysis
In this paragraph we mention some considerations about performing a network harmonic analysis. At the same time we describe the fundamental steps in a network harmonic analysis.
1. Creating a network model
First step is to build a model according to the single line diagram (SLD) provided. In case of very extensive network certain simplifications can be made. However, simplified network model shall have the same main characteristic as the detailed model, particularly with regard to impedance characteristic and resonances. The engineer shall pay attention to modeling components that actually create a grid resonance, such as cables or overhead lines.
The software shall support frequency dependent components as that might be relevant in specific cases.
2. Performing a frequency sweep
A frequency scan or frequency sweep is very useful. It provides you with insights into the network and points out where the resonances are. Select relevant nodes in the system and check the impedance.
3. Adding a harmonic source
Next step is to add a source of harmonics representing the VFD. Crucial is to know whether the VFD has a current harmonic source or voltage harmonic source behavior. Refer to our previous article [2]. You shall also think of the frequency range that you want to analyze. Precondition is that you know the VFD and the harmonic performance at various load points. For example: Is nominal load point the worst case from harmonic perspective or not?
4. Performing harmonic analysis
Now you are ready to perform the actual harmonic analysis and check the harmonic distortion. The software typically allows you to plot the harmonics in frequency domain and eventually also add harmonics from a standard for direct comparison.
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Our experience with software tools for network analysis
We have a personal working experience with following two software tools:
1. NEPLAN
2. PowerFactory
Both tools are quite well-known and perfectly suitable for power system analysis and various studies. They come with a full set of documentation, tutorials and application examples. Also, both companies developing the software are offering trainings and seminars.
Goodies and potential for improvement
NEPLAN
Neplan is a very powerful tool. What we like is the relatively intuitive use that helps you to create your first project rather fast. You can purchase the software modules that you need. In fact, you probably won’t need all of them and you can also purchase an additional module in the future.
The elements in Neplan are nicely listed in the library with name and symbol. That makes the navigation in this toolbox easy and fast. You have multiple ways to visualize your results directly in Neplan, but it is also extremely easy to export the results from the software and process them externally (e.g. in Excel or Matlab).
Video on harmonic analysis in NEPLAN.
Pros and cons of NEPLAN
+ Modules supporting all kind of power analysis disciplines
+ Fairly intuitive structure and modeling
+ Easy processing of data
+ Many different purchase plans and licenses (single user license, cloud based, student version, demo version)
+ Responsive technical support (English, German, Spanish)
– Less documentation
PowerFactory
PowerFactory is another software for network analysis. The basic functionality is comparable with Neplan. With the software you receive a very detailed user manual. In addition, there are tutorials on YouTube. Despite of that we found it more difficult to start a project in PowerFactory. It is a good software and offers many features, but to get familiar with the tool takes quite some time.
One good thing about PowerFactory is the navigation pane. It is helpful in case of larger network models. A lowlight might be the toolbox with network elements. Until version 2020 you would only see an icon. Then you have to place your cursor on that particular icon to get a text box with element name. Of course, some icons are self-explanatory. However, other icons might not be so clear.
Pros and cons of PowerFactory
+ Modules supporting all kind of power analysis disciplines
+ Very detailed documentation (User manual and tutorial)
+ Many application examples
+ Navigation pane
– Less intuitive and time consuming to start with (user manual with 1250 pages)
– Elements/components just with icons (no labels) until 2019 version
Overall impression of the software tools for network analysis
Generally both mentioned software tools for network analysis offer the main functionality that will support you throughout your network analysis. Both of them are quality products with good after-sales support. They are used in academic area as well as in the industry. When benchmarking them you need to compare releases from the same year as the developers constantly improve the software (incl. bug fixing) and add new functionality.
We found Neplan somewhat more intuitive and easier to start with. However, this is our personal and subjective impression. Select the tool that you feel comfortable with. You may check for a demo version and get your experience before making the final decision.
Summary
Harmonics studies of complex grids with multiple configurations cannot be effectively analyzed without a dedicated software tool. Luckily, there is a wide choice of software tools for network analysis. However, it might not be so easy to select the one to use. We have introduced two of them. Both play the premier league in this field. It takes you some time to get into it. One tool might be a bit more intuitive than the other. Important is also decent technical support, availability of seminars, good level of documentation etc.
References
[1] Network harmonics: Introduction, https://mb-drive-services.com/net_harm-introduction/
[2] Network harmonics: VFD harmonic spectrum, https://mb-drive-services.com/network_harmonics_vfd_harmonic_spectrum/
[3] Network harmonics: Harmonic mitigation methods, https://mb-drive-services.com/harmonic_mitigation_methods/
[4] Network harmonics: Harmonic filters, https://mb-drive-services.com/network-harmonics-harmonic-filter/
[5] NEPLAN – Advanced network analysis software, https://www.neplan.ch/
[6] DIgSILENT Power system solutions, https://www.digsilent.de/en/
[7] Power system simulation software list, https://nkloc.wordpress.com/2011/11/11/power-system-simulation-software-list/
