Distributed State Estimation Using a Modified Partitioned Moving Horizon Strategy for Power Systems
Abstract
:1. Introduction
- Instead of all the states in the window estimated by PMHE, the mPMHE only estimates the state vector at the beginning of the window so it is faster than PMHE. The estimated precision of mPMHE is slightly lower than that of PMHE, but their difference is insignificant. The mPMHE achieves comparable state estimation accuracy but with a significant reduction in the overall computation load.
- It is a distributed algorithm and is suitable for large-scale PSSE. Each local area solves for its own local states by using the local measurements and the estimated results from neighboring areas, so the computation load is small. In addition, the communication load is also small because the information is exchanged among neighboring areas only.
- Constraints are taken into account during the optimization process and it is robust to outliers. Hence, good estimated results could be obtained.
2. Centralized State Estimation
2.1. Measurement Model and State Equation
2.2. Weighted Least Squares (WLS)
2.3. Moving Horizon Estimation (MHE)
2.4. Modified Moving Horizon Estimation (mMHE)
3. Modified Partitioned Moving Horizon Estimation (mPMHE)
3.1. mPMHE Problem Formulation
3.2. Update Matrices
4. Simulation Results
4.1. Simulations on the IEEE 14-Bus System
4.1.1. Redundant Observations
- The initial state vectors ; .
- The initial covariance matrices: , , .
- The noise covariances: , ; ;
- The horizon length: .
- State constraints: , , where .
4.1.2. Full Observation with Minimum Number of PMUs
4.2. The IEEE 118-Bus System with Non-Gaussian Noise
4.2.1. Redundant Observations
- The initial state vectors ; ; ; ; ; .
- The initial covariance matrices: , , , , , .
- The noise covariances: , , , , , . ;
- The horizon length: .
- State constraints: , , where .
4.2.2. Full Observation with Minimum Number of PMUs
5. Conclusions
Acknowledgments
Author Contributions
Conflicts of Interest
Abbreviations
m | Number of measurements at time step k |
Number of local measurements at area i | |
n | Number of states |
Number of local states at area i | |
x | True state vector, |
Estimated state vector | |
True local states at area i, | |
Local state vector estimated by the PMHE at time step t | |
Real part of the voltage phasor at bus i | |
Imaginary part of the voltage phasor at bus i | |
The real part of the current measurement | |
The imaginary part of the current measurement | |
Vector of process noise at time step k | |
Process noise at local area i in the PMHE algorithm, | |
z | Measurements from Phasor Measurement Units |
v | Measurement noise |
The i-th measurement residual at time step k | |
The normalized measurement residual i at time step k | |
Chosen function of | |
J | Cost function |
Probability density function of | |
H | Measurement matrix |
Weighting factor for i-th measurement at time step k | |
Derivative of J wrt | |
Horizon length of measurements | |
t, k | Time index |
Standard deviation of measurement noise | |
Q | Covariance matrix of process noise |
R | Covariance matrix of measurement noise |
P | State covariance matrix |
Constraint set for state x |
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Area | Number of Local Measurements | Measurements |
---|---|---|
1 | 10 | |
2 | 20 | |
3 | 20 | |
4 | 8 | |
Noise | Gaussian | Non-Gaussian | |||
---|---|---|---|---|---|
Estimator | Horizon Length | AMSE | Average Time | AMSE | Average Time |
(ms) | (ms) | ||||
WLS | 1 | 0.3 | 0.4 | ||
3 | 1.6 | 1.9 | |||
WLS with LNR | 3 | 7.7 | 14.0 | ||
LAV | 3 | 11.3 | 12.0 | ||
MHE | 3 | 11.8 | 15.9 | ||
mMHE | 3 | 6.6 | 7.3 | ||
PMHE in [24] (area 1) | 3 | 4.9 | 6.5 | ||
PMHE in [24] (area 2) | |||||
PMHE in [24] (area 3) | |||||
PMHE in [24] (area 4) | |||||
mPMHE (area 1) | 3 | 2.6 | 3.7 | ||
mPMHE (area 2) | |||||
mPMHE (area 3) | |||||
mPMHE (area 4) |
Noise | Gaussian | Non-Gaussian | |||
---|---|---|---|---|---|
Estimator | Horizon Length | AMSE | Average Time | AMSE | Average Time |
(ms) | (ms) | ||||
WLS | 1 | 3.2 | 0.2 | 5.1 | 0.2 |
3 | 2.0 | 0.6 | 4.1 | 0.7 | |
WLS with LNR | 3 | 2.0 | 2.3 | 2.4 | 3.9 |
LAV | 3 | 4.4 | 2.4 | 5.3 | |
MHE | 3 | 1.7 | 5.3 | 2.1 | 7.4 |
mMHE | 3 | 1.8 | 3.7 | 2.3 | 4.9 |
PMHE in [24] (area 1) | 3 | 3.3 | 3.3 | 2.1 | 4.3 |
PMHE in [24] (area 2) | |||||
PMHE in [24] (area 3) | |||||
PMHE in [24] (area 4) | |||||
mPMHE (area 1) | 3 | 1.8 | 2.3 | 2.3 | 2.8 |
mPMHE (area 2) | |||||
mPMHE (area 3) | |||||
mPMHE (area 4) |
Scenarios | Redundant Observations | Observation with Minimum Number of PMUs | |||
---|---|---|---|---|---|
Number of PMUs | 54 | 32 | |||
Estimator | Horizon Length | AMSE | Average Time | AMSE | Average Time |
(ms) | (ms) | ||||
WLS | 1 | 14 | 4.2 | 6.4 | |
3 | 182 | 2.6 | 59 | ||
WLS with LNR | 3 | 302 | 2.2 | 115 | |
LAV | 3 | 1.4 | 80 | 2.2 | 55 |
MHE | 3 | 882 | 2.1 | 330 | |
mMHE | 3 | 669 | 2.2 | 264 | |
PMHE in [24] (area 1) | 3 | 55 | 2.1 | 33 | |
PMHE in [24] (area 2) | |||||
PMHE in [24] (area 3) | |||||
PMHE in [24] (area 4) | |||||
mPMHE (area 1) | 3 | 32 | 2.2 | 21 | |
mPMHE (area 2) | |||||
mPMHE (area 3) | |||||
mPMHE (area 4) |
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Share and Cite
Chen, T.; Foo, Y.S.E.; Ling, K.V.; Chen, X. Distributed State Estimation Using a Modified Partitioned Moving Horizon Strategy for Power Systems. Sensors 2017, 17, 2310. https://doi.org/10.3390/s17102310
Chen T, Foo YSE, Ling KV, Chen X. Distributed State Estimation Using a Modified Partitioned Moving Horizon Strategy for Power Systems. Sensors. 2017; 17(10):2310. https://doi.org/10.3390/s17102310
Chicago/Turabian StyleChen, Tengpeng, Yi Shyh Eddy Foo, K.V. Ling, and Xuebing Chen. 2017. "Distributed State Estimation Using a Modified Partitioned Moving Horizon Strategy for Power Systems" Sensors 17, no. 10: 2310. https://doi.org/10.3390/s17102310
APA StyleChen, T., Foo, Y. S. E., Ling, K. V., & Chen, X. (2017). Distributed State Estimation Using a Modified Partitioned Moving Horizon Strategy for Power Systems. Sensors, 17(10), 2310. https://doi.org/10.3390/s17102310