Abstract: In a microgrid system with a series structure of micro-source half-bridge converters in a Y-connection configuration (HCSY-MG), the output power of wind and photovoltaic micro-sources varies significantly due to environmental influences. This variation can cause over-modulation in some half-bridge converter modules, leading to a decline in grid-connected current quality and compromising the system's stable operation. In this paper, a power balance control method combining trapezoidal wave compensation and power adaptive algorithm is studied. The trapezoidal wave compensation control can expand the linear modulation range of the system, and the power adaptive algorithm can ensure that when the maximum modulation range of the trapezoidal wave compensation is exceeded, the power of the preceding micro source can be adjusted adaptive, so that the difference of the output power between the micro source is reduced, and the system can avoid overmodulation. This method can ensure the safe and stable operation of the system under the condition of serious unbalance of micro-source output power and the grid-connected current total harmonic distortion (THD) meets the requirements of grid-connected. Finally, the proposed control strategy is validated through simulation and experiments to determine its feasibility and effectiveness.