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US 11,777,321 B1Granted
Online estimation of POI-level aggregated inertia considering frequency spatial correlation
AssigneeNorth China Electric Power University
InventorsTianshu Bi, Cheng Wang, Jiahao Liu, Guoyi Xu
Life of this patent
Estimating the term…
Abstract
An exemplary two-step method for power system inertia online estimation is described. The first step is to accurately estimate the POI-level aggregated inertia. The second step is to calculate the system-level inertia constant by weighting all the POI-level aggregated inertia and to monitor the inertia spatial distribution. In one example embodiment, the PMU is installed at POI, the frequency spatial difference is considered, and the mechanical power is carefully treated.
Claims1
A method for maintaining power system stability comprising:
- collecting system topology data, reactance values and resistance values of transmission lines from an SCADA/EMS system;
- collecting frequency and active power samples from phaser measurement units (PMU) installed at point of interconnection (POI) buses;
- calculating active power {circumflex over (P)}T at an POI-level aggregated generator terminal and the rotor speed {circumflex over (f)}G of the POI-level aggregated generator according to the following:
- Δ
-
- f
- ˆ
- G
- =
- diag
-
- (
- b
- G
-
- B
- )
- -
- 1
-
- B
- D
-
- B
- [
- E
- B
- D
-
- L
- ]
- +
- [
- Λ
- L
- 0
- N
- ×
- L
- ]
-
- Δ
-
- f
- D
- ,
- m
-
- e
- =
- A
-
- Δ
-
- f
- D
- ,
- m
-
- e
- (
- 19
- )
- where A∈M×M is a linear correlation between rotor speeds and POI bus frequencies;
- and
- {circumflex over (P)}T=PB,me+diag(r)IB,me2, (22)
- where IB,me∈M×1 and PB,me∈M×1 are the current and active power of the incoming line measured by the POI-bus PMU, respectively, and diag(r)∈M×M is a diagonal matrix;
- if the frequency of POI PMU is not available, adopting (19) under an adjusted PMU combination;
- if the non-POI PMUs data are available, calculating the following and obtaining the weighted-least-squares solution {circumflex over (f)}G,W:
- Δ
-
- f
- ˆ
- G
- ,
- W
- =
- diag
-
- (
- b
- G
-
- B
- )
- -
- 1
-
- B
- D
-
- B
- [
- E
- B
- D
-
- L
- ]
- W
- +
- [
- Λ
- L
- 0
- N
- ×
- L
- ]
-
- Δ
-
- f
- D
- ,
- m
-
- e
- =
- A
- W
-
- Δ
-
- f
- D
- ,
- me
- ,
- (
- 21
- )
- estimating POI-level aggregated inertia by solving the following for each POI bus:
- 2Ĥagpy(t)=Δ{circumflex over (P)}mu1(t)+u2(t), (23a)
- y={0,{circumflex over (f)}G(t2)−{circumflex over (f)}G(t1),{circumflex over (f)}G(t3)−{circumflex over (f)}G(t1), . . . ,{circumflex over (f)}G(tK)−{circumflex over (f)}G(t1)}, (23b)
- ū1={1,1,1, . . . ,1}, (23c)
- ū2={0,−{circumflex over (P)}T(t2)+{circumflex over (P)}T(t1),−{circumflex over (P)}T(t3)+{circumflex over (P)}T(t1), . . . ,−{circumflex over (P)}T(tK)+{circumflex over (P)}T(t1)}. (23d)
- in which {Ĥag, Δ{circumflex over (P)}m} is the parameter vector to be identified;
- y(t) and u2(t) are the values of rotor speed and active power deviation from the operating point,
- respectively;
- and u1(t) represents the mechanical power and remains constant;
- estimating the system-level inertia by:
- H
- ^
- s
-
- y
-
- s
- ,
- t
- =
- ∑
- i
- H
- ^
- ag
- ,
- i
- ,
- S
- ag
- ,
- i
- ∑
- i
- S
- ag
- ,
- i
- ,
- ∀
- t
- ,
- (
- 24
- )
- where Ĥag,i and Sag,i are the POI-level aggregated inertia constant and rated capacity of generator i, respectively;
- estimating frequency stability indexes including post-disturbance rate of change of frequency (RoCoF) and frequency nadir based on the system-level inertia;
- determine whether the frequency stability indexes reach a predetermined limitation;
- when the predetermined limitation is reached, activate at least one generator to increase system inertia.
178 more elements
Dependencies are inferred from the claim text.