It explicitly shows that the

grid current is sinusoidal and in phase with the grid voltage, which implies that only real power is fed to the grid.

SAPF has been used extensively for harmonic suppression, reactive power compensation and

grid current equilibrium in the distribution system [3], [4].

where i(h),[i.sub.m](h) is the current harmonic of inverter side and the

grid current harmonic of switch frequency respectively.

However, many of them are based on THD of

grid current [2], [5], [6], which is impossible to calculate for predictive control with variable switching frequency or design is very simplified [3], [4].

11 shows the AC/DC Converter switching signals generation, where [V.sub.s,RMS] is the RMS Grid voltage value (V), and [i.sub.s,meas] is the measured

Grid current (A).

The research of the inverter shows that angle [[phi].sub.i1] is equal approximately to the phase angle of the modulation voltage of inverter [[phi].sub.m.] The

grid current for fundamental frequency is expressed as follows

The THD of the

grid current is over 10%, compared to only 2.30 % obtained in Case 1.

its advantages over the single H-bridge inverter are lower THDi of the

grid current and THDu of the output voltage, requirements of smaller filters, ability to transfer more power and smaller du/dt stresses.

Fig.11 shows the simulation results of load current, APF current and

grid current and voltage, corresponding to reactive power compensation mode, when the switch denoted by [sw.sub.2] is turned off (Fig.3).

In [10], a distribution static compensator was designed with neural fuzzy network to reduce the harmonics of

grid current and improve the voltage of DC-link.

[I.sub.a] is the output current of the qZS inverter, [I.sub.g] is

grid current; in which case it is Voltage Source Generator (VSG) current.

Figure 6 shows the harmonic components of the injected

grid current in correspondence to the number of charging cycles; frequency domain data are obtained performing a Fast Fourier Transform (FFT).