Power Flow Optimization and Economic Analysis Based on High Voltage Phase Shifting Transformer
Abstract
:1. Background
2. Theoretical Research and Selection of PST
2.1. Working Principle of PST
2.2. Topology Selection of PST
2.2.1. Selection of Transformer Structure
2.2.2. Electrical Characteristic Selection
2.3. Equivalent Model of Double Core Symmetric PST
2.3.1. Double Core Symmetric PST Topology
2.3.2. Load Equivalent Model
3. Multi-Node Network Power Flow Optimization Simulation
4. Loop Network Power Flow Optimization Simulation
4.1. Design of 220 kV Phase Shifting Transformer Parameters
4.1.1. Loop Power Flow
4.1.2. Parameters Design and Verification
4.2. 220 kV Loop Network Power Flow Optimization Simulation
4.2.1. Steady Power Flow
4.2.2. N-1 Power Flow
4.3. Simulation Analysis under Short Circuit Fault
5. Economic Analysis of Engineering Application
5.1. Cost of PST Analysis
5.2. Comparative Analysis of UPFC and PST Costs
6. Experimental Verification
- (1)
- When the PST is switched to +4 gear, the maximum leading phase shift angle is output, and the angle is −25.5°. When the PST is switched to −4, the maximum lag phase shift angle is output, and the angle is 26.17°. The error between the measured value and the theoretical value of each gear is small, and the reason for the error is the leakage reactance of transformer winding.
- (2)
- With the change of phase shift angle, the adjustment range of line transmission power is −224.12 W~240.17 W. When the on-load voltage regulating switch of the PST is turned to different gears, the active power of the line can be adjusted without changing the voltage amplitude before and after the phase shift, and thus, we can realize the independent control of the active power of the line.
7. Conclusions
- (1)
- Comparing the characteristics of various types of PST, a high voltage of 220 kV and above was more suitable for the selection of double core symmetrical PST. The influence of winding leakage reactance and saturation effect should be considered in the design of PST parameters; the iron core area and winding turns should be reasonably selected, and a certain phase shifting angle margin should be reserved.
- (2)
- For the actual 220 kV ring network of the Guangdong Power Grid, when PST was installed in the Huizhou–Sandong line and Huizhou–Yongyuan line, the transmission limit of the two lines sections could be increased to 1645 MW under normal working conditions, and the load rate of the four transmission channels was close to 100%. The transmission limit of both lines and planes could be increased to 1219 MW under N−1 condition. However, the phase shift angle required to adjust the power flow was smaller (θ = 8°), and the cost was lower when it was installed on the Huizhou–Third line. Therefore, the installation site chosen was the Huizhou–Sandong line.
- (3)
- As FACTS elements, UPFC had faster response speed and stronger power flow regulation ability than PST and could provide reactive power compensation for the system, with certain low−voltage ride through capability. However, PST had simple structure and better economy and reliability. In the 220 kV ring network scheme, the total cost of a single PST was reduced by about 49.86%. On the premise of ensuring the effect of power flow regulation, the investment cost was significantly reduced, and the economic benefit was remarkable.
- (4)
- Through the prototype experiment, the regulation ability of dual core symmetrical PST to line power flow was verified, and the controllable regulation of line power flow was realized on the premise of constant voltage amplitude. However, due to the influence of measurement error and background harmonic, there were some errors in the experimental results. This paper did not consider the switching process and transient regulation performance of PST, so it was only suitable for steady−state power flow analysis. If the transient performance needed to be analyzed, it would be necessary to do further research in combination with power electronic devices.
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
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Performance | Single Core PST | Double Core PST |
---|---|---|
Structure | Simple | Complex |
On-load tap switch | High insulation requirements | Low insulation requirements |
Short circuit impedance | <10% | 12~19% |
Applicable voltage class | Low | High |
Cost | Low | High |
The phase shift range | Narrow | Wide |
Technical Parameters | Value |
---|---|
Rated voltage/kV | 230 |
Rated current/kA | 1.3 |
Rated capacity/MVA | 450 |
Adjustment class | ±13 |
No-load phase shift Angle/° | 25 |
Full-load phase shift Angle/° | 20 |
Short circuit impedance of series transformer/% | 7 |
Short circuit impedance of excitation transformer/% | 4.5 |
Cost of Each Unit | Total Cost | |
---|---|---|
UPFC | 10.312 million yuan | 206 million yuan |
PST | 5.170 million yuan | 129 million yuan |
PST compared with UPFC | Reduced by 49.86% | Reduced by 49.86% |
Gear | Us (V) | UL (V) | θ (°) | θPST (°) | P (W) | ||
---|---|---|---|---|---|---|---|
Theoretical | Measured | Theoretical | Measured | ||||
1 | 224 | 223 | 6.2 | 7.2 | 93.1 | 93.6 | 17.43 |
2 | 224 | 223 | 12.4 | 13.9 | 96.2 | 97.2 | 64.99 |
3 | 223 | 223 | 18.7 | 20.6 | 99.4 | 100.3 | 141.39 |
4 | 223 | 222 | 25.0 | 25.5 | 102.5 | 102.6 | 240.71 |
0 | 223 | 223 | 0 | 0 | / | / | 0 |
−1 | 223 | 223 | −6.2 | −7.4 | −93.1 | −93.6 | −13.74 |
−2 | 223 | 223 | −12.4 | −14.6 | −96.2 | −96.4 | −57.48 |
−3 | 223 | 223 | −18.7 | −20.6 | −99.4 | −100.8 | −127.72 |
−4 | 223 | 223 | −25.0 | −26.1 | −102.5 | −103.5 | −224.12 |
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Yu, M.; Yuan, J.; Li, Z.; Li, F.; Yang, X.; Zhang, W.; Xu, S.; Mei, J. Power Flow Optimization and Economic Analysis Based on High Voltage Phase Shifting Transformer. Energies 2022, 15, 2363. https://doi.org/10.3390/en15072363
Yu M, Yuan J, Li Z, Li F, Yang X, Zhang W, Xu S, Mei J. Power Flow Optimization and Economic Analysis Based on High Voltage Phase Shifting Transformer. Energies. 2022; 15(7):2363. https://doi.org/10.3390/en15072363
Chicago/Turabian StyleYu, Mengze, Jiaxin Yuan, Zuohong Li, Feng Li, Xinyi Yang, Weizhe Zhang, Shunkai Xu, and Jiajun Mei. 2022. "Power Flow Optimization and Economic Analysis Based on High Voltage Phase Shifting Transformer" Energies 15, no. 7: 2363. https://doi.org/10.3390/en15072363