In order to control inverters more effectively and coordinate and reduce dependence on the reference voltage of the systems, a unified control method based on voltage phase angle control for the inverter of sources is presented. The inverter is controlled to work as the voltage source, in which the output voltage amplitude of the inverter is controlled so that the output power of the inverter is no greater than its maximum power. At the same time, the phase angle of the inverter voltage is also controlled to control the work mode of the inverter. The inverter works as the reference-voltage source when the fixed phase angle of the inverter voltage is controlled. The phase angle of the inverter voltage may be controlled to follow the output power requirement, in which the work mode of the inverter is the power tracking mode. Furthermore, the two working modes of the inverter can be switched with each other smoothly. The result is that the impact from changing the working mode of the inverter on the power system can be avoided. The simulation model for the proposed control is built in Matlab/Simulink and the effectiveness is verified. This work is supported by National Natural Science Foundation of China (No. 50777066).