Shunt active power filters (SAPF) are employed to improve power quality by injecting compensating harmonic current. The modular SAPF offers many new capabilities that are otherwise unavailable by the conventional SAPF, such as high crest factor compensating current and fast dynamic response. However, there are still challenges that are needed to be addressed, such as resonance and stability issues associated with the modular SAPF. To investigate these issues, this work first presents a mathematical model for conventional modular SAPF system. Based on the mathematical analysis, a new hybrid three-level modular SAPF is presented that is composed of two types of modules, each with different current carrying capacities, LCL filter parameters, and switching frequencies. The proposed hybrid system provides a wider current tracking bandwidth and fast dynamic response as compared to the present modular SAPF. A novel self-adaptive, active damping strategy is proposed that effectively suppresses resonance and coupling between modules. Mathematical analysis and experimental results have been used to verify the proposed system.
- SAPF-Shunt Active Power Filter
- Power Quality
- LCL filter
Fig. 1 (a)50A module topology (b)100A module topology
EXPECTED SIMULATION RESULTS:
Fig. 2. Simulation results of output current increase with three SAPF in parallel operation
Fig. 3 Simulation results of parallel units increase with six SAPF in parallel operation
Fig. 4. Compensating current of hybrid modules with different damping methods
Fig. 5 Compensating current of hybrid modules with load change
Fig. 6. (a)Simulation results of three SAPF in parallel (b)THD of grid current
This paper improves upon the conventional modular SAPF mathematical models to investigate tradeoffs between dynamic response and stability control. According to the analysis results obtained from the model, a novel hybrid modular three level SAPF structure is proposed. In contrast to previous methods, the proposed system is composed of two modules, each with different current carrying capacities, LCL filter parameters, and switching frequencies. Finally, a novel self adaptive resonance suppression strategy is proposed to take into account the variations in the number of modules and load current. Theoretical analysis and experimental results confirm that the hybrid modular SAPF and its self-adaptive resonance suppression strategy can achieve a better tradeoff between dynamic response and stability control as compared with the conventional modular SAPF. The proposed system may be used in industrial applications, in particular for power quality improvement in weak power grids.
- Fang, G. Xiao, X. Yang, and Y. Tang, “Parameter design of a novel series-parallel-resonant lcl filter for single-phase half-bridge active power filters,” IEEE Transactions on Power Electronics, vol. 32, no. 1, pp. 200–217, Jan 2017.
- C. Alfonso-Gil, E. P´erez, C. Arino, and H. Beltran, “Optimization algorithm for selective compensation in a shunt active power filter,” IEEE Transactions on Industrial Electronics, vol. 62, no. 6, pp. 3351–3361, 2015.
- Angulo, D. A. Ruiz-Caballero, J. Lago, M. L. Heldwein, and S. A. Mussa, “Active power filter control strategy with implicit closed-loop current control and resonant controller,” IEEE Transactions on Industrial Electronics, vol. 60, no. 7, pp. 2721–2730, 2013.
- He, Y. W. Li, and F. Blaabjerg, “Flexible microgrid power quality enhancement using adaptive hybrid voltage and current controller,” IEEE Transactions on Industrial Electronics, vol. 61, no. 6, pp. 2784–2794, 2014.
- Acuna, L. Mor´an, M. Rivera, J. Dixon, and J. Rodriguez, “Improved active power filter performance for renewable power generation systems,” IEEE transactions on power electronics, vol. 29, no. 2, pp. 687–694, 2014.