Finite Control Set Model Predictive Control for Parallel Connected Online UPS System under Unbalanced and Nonlinear Loads
Abstract
:1. Introduction
- THD of inverter’s output voltage is less than 4% under all loading conditions.
- Voltage drop is not more than 5% under all loading conditions.
- The inverter provides constant output root mean square (RMS) voltage, irrespective to disturbance or variation in system parameters such as temperature, load current, etc. [1]
2. Description and Mathematical Modelling of System
2.1. LC Filter Modelling
2.2. Discrete Time Domain Modelling
3. Operating Principle of FCS–MPC
- In the start of each sampling time, and are measured through sensors.
- The information is sent to the algorithm, it is defined by the initial point from where the algorithm forecasts the future behavior of controlled variables using Equation (14), for all possible voltage vectors.
- These predicted values are used to find the predefined cost functions (CF) and a voltage vector that has a minimal value of CF as applied to VSI.
Switching Frequency Reduction Scheme
4. Droop Control
5. Results
5.1. Steady State Analysis
5.2. Load Transient Analysis
5.3. Multiple UPS Systems
6. Conclusions
Author Contributions
Funding
Conflicts of Interest
References
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Space Vector | Switching Vector | On-State Switch | Vector Placing | |
---|---|---|---|---|
Zero vector | ||||
Active vector | ||||
Output Impedance | ||
---|---|---|
Active Power | ||
Reactive Power | ||
Frequency Droop | ||
Amplitude Droop | ||
Droop coefficient | ||
Droop coefficient |
Parameter | Value |
---|---|
DC link Voltage | |
Sampling Time | |
LC-filter | |
Damping Resistance | |
Linear load | |
Non-linear load (diode rectifier) | |
Nominal Voltage | |
Average Switching Frequency | |
Rated Frequency | |
Droop coefficients | |
Proportional Gain | kp = 50 |
Proportional Integrator |
Load Types | Proposed MPC Voltage THD (%) | PI Voltage THD (%) |
---|---|---|
Balanced resistive load | 0.96 | 1.22 |
No Load | 0.96 | 1.22 |
Non-Linear Load | 1.23 | 4.31 |
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Khan, H.S.; Aamir, M.; Ali, M.; Waqar, A.; Ali, S.U.; Imtiaz, J. Finite Control Set Model Predictive Control for Parallel Connected Online UPS System under Unbalanced and Nonlinear Loads. Energies 2019, 12, 581. https://doi.org/10.3390/en12040581
Khan HS, Aamir M, Ali M, Waqar A, Ali SU, Imtiaz J. Finite Control Set Model Predictive Control for Parallel Connected Online UPS System under Unbalanced and Nonlinear Loads. Energies. 2019; 12(4):581. https://doi.org/10.3390/en12040581
Chicago/Turabian StyleKhan, Hussain Sarwar, Muhammad Aamir, Muhammad Ali, Asad Waqar, Syed Umaid Ali, and Junaid Imtiaz. 2019. "Finite Control Set Model Predictive Control for Parallel Connected Online UPS System under Unbalanced and Nonlinear Loads" Energies 12, no. 4: 581. https://doi.org/10.3390/en12040581