A Novel 7-Level Cascaded Inverter for Series Active Power Filter


Harmonic voltage compensation of the load connected to the point of common coupling (PCC) by using a series of active power filter (SAPF) based on a single phase cascaded multilevel inverter is proposed. The proposed multilevel inverter are presented in detail. The inverter has the ability of acting as a harmonic source when the reference is a non-sinusoidal signal. To achieve this, a simple control technique is performed with the proposed inverter. A prototype of 7-level inverter based SAPF is manufactured without using a parallel passive filter (PPF) because it is designed to show SAPF own compensation capacity alone. Filtering ability of the SAPF is shown both in simulation and experimental studies. The validity of the proposed inverter based SAPF is verified by simulation as well as experimental study. The results show that the proposed multi-level inverter is suitable for SAPF applications.


  1. Active power filter
  2. Multilevel inverter
  3. Harmonic compensation
  4. Half-bridge cascaded
  5. Power quality



Fig. 1. The scheme of the proposed system.



 (a) Simulation result (50 V/div), (5 ms/div)

Fig. 2. The waveform of VPCC before compensation

(a) Simulation result (50 V/div), (5 ms/div)

Fig. 3. The waveforms of the load voltage and the proposed inverter voltage after compensation.


This paper proposes a single phase cascaded inverter based SAPF. The 7-level inverter topology and operation principle is introduced. With the proposed topology, the number of output levels can easily be increased. Switching signals of the semiconductor devices used in the inverter are also obtained by a simple method. A SAPF with the proposed inverter topology is simulated.The aim of the simulation is to compensate the load voltage harmonics connected to PCC. In addition to the simulation, the proposed SAPF prototype is designed. Using this prototype, experimental study is performed. Simulation and experimental results similar each other proves the accuracy of the analysis. The load waveform that is highly distorted with a THD value of 24.12% is compensated with the proposed inverter based SAPF and the THD value is reduced to 3.80% in experimental study. This shows that the proposed inverter is suitable for SAPF applications.


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[2] F. Z. Peng, H. Akagi, and A. Nabae, “A new approach to harmonic compensation in power systems—A combined system of shunt passive and series active filters,” IEEE Trans. Ind. Appl., vol. 26, no. 6, pp. 983– 990, Nov./Dec. 1990.

[3] Z. Wang, Q. Wang, W. Yao, and J. Liu, “A series active power filter adopting hybrid control approach,” IEEE Trans. Power Electron., vol. 16, no. 3, pp. 301–310, May 2001.

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[5] M. El-Habrouk, M. K. Darwish, and P. Mehta, “Active power filters: A review,” IEE Electr. Power Appl., vol. 147, no. 5, pp. 403–413, Sep. 2000.

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