**ABSTRACT:**

** **An active power filter implemented with a four-leg voltage-source inverter using a predictive control scheme is presented. The use of a four-leg voltage-source inverter allows the compensation of current harmonic components, as well as unbalanced current generated by single-phase nonlinear loads. A detailed yet simple mathematical model of the active power filter, including the effect of the equivalent power system impedance, is derived and used to design the predictive control algorithm. The compensation performance of the proposed active power filter and the associated control scheme under steady state and transient operating conditions is demonstrated through simulations and experimental results.

** ****KEYWORDS:**

- Active power filter
- Current control
- Four-leg converters
- Predictive control.

**SOFTWARE:** MATLAB/SIMULINK

**BLOCK DIAGRAM:**

Fig. 1. Three-phase equivalent circuit of the proposed shunt active power filter.

Fig. 2. *dq*-based current reference generator block diagram.

** EXPECTED SIMULATION RESULTS:**

Fig. 3. Simulated waveforms of the proposed control scheme. (a) Phase to neutral source voltage. (b) Load Current. (c) Active power filter output current. (d) Load neutral current. (e) System neutral current. (f) System currents. (g) DC voltage converter.

Fig. 4. Experimental transient response after APF connection. (a) Load Current *i*_{Lu} , active power filter current *i*_{ou} , dc-voltage converter *v*_{dc} , and system current *i*_{su} . Associated frequency spectrum. (c) Voltage and system waveforms, *v*_{su} and *i*_{su} , i_{sv} , i_{sw} . (d) Current reference signals *i*^{*}_{ou} , and active power filter current *i*_{ou} (tracking characteristic).

Fig. 5. Experimental results for step load change (0.6 to 1.0 p.u.). Load Current *i*_{Lu} , active power filter current *i*_{ou} , system current *i*_{su} , and dc-voltage converter *v*_{dc} .

Fig. 6. Experimental results for step unbalanced phase u load change (1.0 to 1.3 p.u.). (a) Load Current *i*_{Lu} , load neutral current *i*_{Ln} , active power filter neutral current *i*_{on} , and system neutral current *i*_{sn} . (b) System currents *i*_{su} , i_{sv} , i_{sw} , and *i*_{sn} .

**CONCLUSION:**

Improved dynamic current harmonics and a reactive power compensation scheme for power distribution systems with generation from renewable sources has been proposed to improve the current quality of the distribution system. Advantages of the proposed scheme are related to its simplicity, modeling, and implementation. The use of a predictive control algorithm for the converter current loop proved to be an effective solution for active power filter applications, improving current tracking capability, and transient response. Simulated and experimental results have proved that the proposed predictive control algorithm is a good alternative to classical linear control methods. The predictive current control algorithm is a stable and robust solution. Simulated and experimental results have shown the compensation effectiveness of the proposed active power filter.

**REFERENCES:**

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