Adaptive PI Control of STATCOM for Voltage Regulation

ABSTRACT:

STATCOM can provide fast and efficient reactive power support to maintain power system voltage stability. In the literature, various STATCOM control methods have been discussed including many applications of proportional-integral (PI) controllers. However, these previous works obtain the PI gains via a trial-and-error approach or extensive studies with a tradeoff of performance and applicability. Hence, control parameters for the optimal performance at a given operating point may not be effective at a different operating point. This paper proposes a new control model based on adaptive PI control, which can self-adjust the control gains during a disturbance such that the performance always matches a desired response, regardless of the change of operating condition. Since the adjustment is autonomous, this gives the plug-and-play capability for STATCOM operation. In the simulation test, the adaptive PI control shows consistent excellence under various operating conditions, such as different initial control gains, different load levels, change of transmission network, consecutive disturbances, and a severe disturbance. In contrast, the conventional STATCOM control with tuned, fixed PI gains usually perform fine in the original system, but may not perform as efficient as the proposed control method when there is a change of system conditions.

KEYWORDS:
1. Adaptive control
2. Plug and play
3. Proportional-integral (PI) control
4. Reactive power compensation
5. STATCOM
6. Voltage stability.

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:
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Figure 1 Studied system

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Fig.2 Results of (a) voltages and (b) output reactive power using the same network and loads as in the original system.
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Fig.3 Results of using the same network and loads as in the original system.
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Fig. 4. Results of (a) voltages and (b) output reactive power with changed PI control gains
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Fig. 5. Results of (a) voltages and (b) output reactive power with a change of load
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Fig. 6. Results of with changed PI control gains.
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Fig. 7. Results of α with a change of load.
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Fig. 8. Results of α(a) voltages and (b) output reactive power with a change of transmission network.
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Fig. 9. Results of α with a change of transmission network.
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Fig. 10. Results of α (a) voltages and (b) output reactive power with two consecutive disturbances.
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Fig. 11. Results of α with two consecutive disturbances.

CONCLUSION:
In the literature, various STATCOM control methods have been discussed including many applications of PI controllers. However, these previous works obtain the PI gains via a trialand- error approach or extensive studies with a tradeoff of performance and applicability. Hence, control parameters for the optimal performance at a given operating point may not always be effective at a different operating point. To address the challenge, this paper proposes a new control model based on adaptive PI control, which can self-adjust the control gains dynamically during disturbances so that the performance always matches a desired response, regardless of the change of operating condition. Since the adjustment is autonomous, this gives the “plug-and-play” capability for STATCOM operation.
In the simulation study, the proposed adaptive PI control for STATCOMis compared with the conventional STATCOM control with pretuned fixed PI gains to verify the advantages of the proposed method. The results show that the adaptive PI control gives consistently excellent performance under various operating conditions, such as different initial control gains, different load levels, change of the transmission network, consecutive disturbances, and a severe disturbance. In contrast, the conventional STATCOM control with fixed PI gains has acceptable performance in the original system, but may not perform as efficient as the proposed control method when there is a change of system conditions.
Future work may lie in the investigation of multiple STATCOMs since the interaction among different STATCOMs may affect each other. Also, the extension to other power system control problems can be explored.

REFERENCES:
[1] F. Li, J. D. Kueck, D. T. Rizy, and T. King, “A preliminary analysis of the economics of using distributed energy as a source of reactive power supply,” Oak Ridge, TN, USA, First Quart. Rep. Fiscal Year, Apr. 2006, Oak Ridge Nat. Lab.
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