Permanent zero on Fuzzy block output P&O mppt algorithm

Question

Mohamed ARRACH 2024-8-17，19:24

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2145999-permanent-zero-on-fuzzy-block-output-p-o-mppt-algorithm

评论： Mohamed ARRACH 2024-8-20，17:14

Dear Staff and members,

I have an issue on my Fuzzy block which display only zero value on Matlab R2017b in a P&O MPPT algorithm model. If anyone can help. Thanks in advance.

2 个评论
显示无隐藏无

Sam Chak 2024-8-17，19:51

Can't help without seeing the Simulink file and the FIS file. Can you put them in a zipped file and attach it by clicking that paperclip icon

?

Mohamed ARRACH 2024-8-17，23:10

Fuzzy logic issue.zip

Hi Dear Sam,

Please find in the attached the requested file. Looking forward your response. Thanks in advance.

Mohamed.

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Sam Chak 2024-8-18，8:50

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2145999-permanent-zero-on-fuzzy-block-output-p-o-mppt-algorithm#answer_1500234

Hi @Mohamed ARRACH

From Scope 1, you can observe that the "error" value is -25; however, this value lies outside the range of the "error" fuzzy set. Therefore, I suspect that the defuzzified "output1" value was set to its mean range value (−1 + 1)/2 = 0. To address this issue, ensure that the operating values lie within the ranges of the fuzzy sets {'error' and 'change_in_error'} by properly scaling them. This will resolve the problem.

Unfortunately, your MPPT model contains an algebraic loop that cannot be solved. If you examine the loop highlighted in yellow, you will see that the computation in the 'Division × ÷' block requires the input value of Vd. However, the computation of Vd in the 'Addition' block depends on values derived from the output of the 'Division × ÷' block. This complex 'static' mathematical operation creates the "Algebraic Loop" issue.

In normal circumstances, 'dynamic' math operations are supplied with initial state values to prevent the "Algebraic Loop" issue that use the input value for the current time step to calculate the output value for the current time step.

Figure 1: Comparing the actual input values to the FIS and the ranges of Fuzzy Sets {'error' and 'change_in_error'}

Figure 2: Test if the FIS returns a non-zero output value if the input value lies in the range of the fuzzy set.

Figure 3: The ranges of the fuzzy sets are rescaled.

Figure 4: The Fuzzy System issue is fixed, but the MPPT model contains an algebraic loop that cannot be solved.

5 个评论
显示 3更早的评论隐藏 3更早的评论

Sam Chak 2024-8-19，17:03

Hi @Mohamed ARRACH

My rhetorical question was intended to suggest that you insert a relatively fast dynamic first-order "Transfer Function" or "State-Space" block directly after the "Addition" block to break the unrealizable instantaneous algebraic loop.

With the "State-Space" block, you can specify the initial Vd freely. If you use the "Transfer Function" block, the solver assumes that the initial Vd is 0 by default.

Please test it and let me know if it works.

Mohamed ARRACH 2024-8-20，17:14