calculate_BODF error - ValueError: need at least one array to concatenate

[Jesse Farmer]

I'm calling the calculate_BODF() method and getting this error.  What populates the passive_branch_components member?  I notice it is empty in my model but yet I have lines and transformers present.

Can someone help?

subnet = psanet.determine_network_topology()

psanet.sub_networks.iloc[1,2].calculate_BODF()

Error:

SubNetwork 1

---------------------------------------------------------------------------

ValueError 

 Traceback (most recent call last) 

<ipython-input-80-d59a9ddc4db2> in <module> 

7 

8 #print(psanet.passive_branch_components) 

----> 9 psanet.sub_networks.iloc[1,2].calculate_BODF() 

10 #psanet.export_to_csv_folder('c:\\test\\psanet_output\\') 

~\anaconda3\lib\site-packages\pypsa\contingency.py in calculate_BODF(sub_network, skip_pre) 

68 

69 if not skip_pre:

---> 70 calculate_PTDF(sub_network) 

71 

72 num_branches = sub_network.PTDF.shape[0] 

~\anaconda3\lib\site-packages\pypsa\pf.py in calculate_PTDF(sub_network, skip_pre) 

890 

891 if not skip_pre: 

--> 892 calculate_B_H(sub_network) 

893

894 #calculate inverse of B with slack removed 

~\anaconda3\lib\site-packages\pypsa\pf.py in calculate_B_H(sub_network, skip_pre) 

850 

851 #susceptances 

--> 852 b = 1./np.concatenate([(c.df.loc[c.ind, attribute]).values \ 

853 for c in sub_network.iterate_components(network.passive_branch_components)]) 

854

<__array_function__ internals> in concatenate(*args, **kwargs) 

  ValueError: need at least one array to concatenate

[Fabian Hofmann]

Did you check whether there exist branches in your sub(!)network? If psanet.sub_networks.iloc[1,2].branches() is empty, this should be the problem.

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[Jesse Farmer]

Yes, it is an empty DataFrame.  Only my first subnetwork (0) contains branches.  I do not understand this because I did a .consistency_check() and ran .lpf() on the network.  During the lfp, the following was displayed:

INFO:pypsa.pf:Performing linear load-flow on AC sub-network SubNetwork 0 for snapshot(s) Index(['now'], dtype='object') 

INFO:pypsa.pf:Performing linear load-flow on AC sub-network SubNetwork 1 for snapshot(s) Index(['now'], dtype='object')

 INFO:pypsa.pf:Performing linear load-flow on AC sub-network SubNetwork 2 for snapshot(s) Index(['now'], dtype='object')

 INFO:pypsa.pf:Performing linear load-flow on AC sub-network SubNetwork 3 for snapshot(s) Index(['now'], dtype='object')

 INFO:pypsa.pf:Performing linear load-flow on AC sub-network SubNetwork 4 for snapshot(s) Index(['now'], dtype='object')

 INFO:pypsa.pf:Performing linear load-flow on AC sub-network SubNetwork 5 for snapshot(s) Index(['now'], dtype='object')

 INFO:pypsa.pf:Performing linear load-flow on AC sub-network SubNetwork 6 for snapshot(s) Index(['now'], dtype='object')

According to the documentation, the sub-networks are created automatically, is this correct?  Why is the lfp generating multiple empty subnetworks?

I want to stress that my network case I am using is a real-world grid.

[Fabian Hofmann]

Yes that's correct. Idk how your network looks like, but if the subnetworks has no passive branches (and probably just one bus), then you just skip it in your BODF analysis.

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[Jesse Farmer]

OK, so I ran the BODF on only the first subnetwork which has all the branches.  I am still getting two warnings:

\anaconda3\lib\site-packages\scipy\sparse\linalg\dsolve\linsolve.py:318: SparseEfficiencyWarning: splu requires CSC matrix format 

\anaconda3\lib\site-packages\pypsa\contingency.py:77: RuntimeWarning: divide by zero encountered in true_divide

I am able to print the BODF so it would seem the procedure is finishing.