*3.2. Advanced Burst Control*

When solar power generation and load are very small, micro-inverters operate only intermittently to supply the desired power to the grid on an average power basis. This intermittent operation is called "burst control". For the burst control, the micro-inverter supplies *ig* to the grid only during the ON state, and stops running during the OFF state. The burst control improves power-conversion efficiency by reducing the ripple of *ig* and switching loss when the load is small.

In the conventional burst control scheme, positive and negative grid currents are consecutively supplied to the grid during one ON-state period (Figure 10). Then OFF-state periods follow the ON-state period. During the OFF state, no power is output, so output occurs only during the ON state, and the energy flowing out of *CIN* is also concentrated. Therefore, the input ripple voltage Δ*VIN* is increased, the MPPT efficiency is reduced, and additional time is required to charge the input capacitor *CIN* for the next operation.

**Figure 10.** Conventional and advanced burst control schemes.

To further improve the performance of burst control, this paper proposes AB control, which supplies positive grid current during the first ON-state (Figure 10). The negative grid current is supplied during the ON-state that immediately follows the first ON-state period. Then, OFF-state periods follow the ON-state periods. This scheme has the effect of distributing the output current temporally compared with the conventional burst control scheme. Therefore, in the proposed micro-inverter with the advanced burst control scheme, the MPPT efficiency can be improved, and the input capacitance *CIN* can be reduced due to the reduced Δ*VIN*.
