Issue Regarding Solving ∆P Using ROCOF

[lin-1l1]

Dear Andes developers,

In the example of "Load Frequency Control," the method employed was ss.PV.as_df() to analyze the lost active power within the system (0.4pu). However,I want to utilize ROCOF to solve for ∆P, but I'm encountering some difficulties.

Firstly, I'm uncertain about how to choose an appropriate Tw value in ROCOF. Additionally, I'd like to inquire whether Andes provides a function to calculate the overall inertia H?

My calculation method is based on the ROCOF formula: ROCOF = (∆P * f) / (2 * H * S), but the ∆P value I'm obtaining is only 0.2, which is not consistent with my expectations. Could I have overlooked or made a mistake somewhere in my calculations?

Thank you very much for your assistance!

Attached is the result figure I've attempted.

[jinningwang]

Firstly, I'm uncertain about how to choose an appropriate Tw value in ROCOF.

Check this, #529

Additionally, I'd like to inquire whether Andes provides a function to calculate the overall inertia H?

Short answer, no.
For synchronous machine, H is a constant, and you can sum up M for all GENCLS and GENROU. However, to my knowledge, when it comes to IBR, there is no clear definition of inertia yet. You can define your own "inertia" and calculate it.

My calculation method is based on the ROCOF formula: ROCOF = (∆P * f) / (2 * H * S), but the ∆P value I'm obtaining is only 0.2, which is not consistent with my expectations. Could I have overlooked or made a mistake somewhere in my calculations?

In this equation, delta P can be impacted by how the ROCOF is obtained, and you can pay attention to the ROCOF values first.

[lin-1l1]

jinning, thank you for your response and assistance!

After carefully reading #529, I'm still a bit confused. I've attempted to compare the results of GENROU with different tw values of BusROCOF, and I'm wondering if I understand correctly: Is finding the tw value that best approximates the smooth curve the best answer?

[cuihantao]

You might want to install a BusFreq at a generator bus and then tune the parameters of BusFreq to make the estimated frequency close to the generator's omega. Then, you can reuse the parameter for BusROCOF.

[jinningwang]

As shown below, BusROCOF is derived from BusFreq, so the first step is to have appropriate parameters of the bus measurement part.

andes/andes/models/measurement/busrocof.py

Lines 9 to 26 in 5ab784b

	class BusROCOF(BusFreq):
	"""
	Bus frequency and ROCOF measurement.
	The ROCOF output variable is ``Wf_y``.
	"""
	def __init__(self, system, config):
	BusFreq.__init__(self, system, config)
	self.Tr = NumParam(default=0.1,
	info="frequency washout time constant",
	tex_name='T_r')
	self.Wf = Washout(u=self.f,
	K=1,
	T=self.Tr,
	info='frequency washout yielding ROCOF',
	)

[lin-1l1]

Thank you Professor Cui and Jinning for your replies and assistance! Your valuable suggestions and help are greatly appreciated. Thank you once again.