Abstract : This paper analyzes the power and current characteristics of a parallel inverter system, concluding that the generation of circulating current and the power distribution of the power supply are related to the output voltage frequency and amplitude of each module. This paper adopts the external characteristic droop method and applies it to the parallel inverter system, enabling wireless parallel operation. Keywords : External characteristic droop; circulating current; inverter; wireless parallel connection 1. Introduction Parallel inverter technology is an important technical means to improve the reliability of inverter operation and expand the power supply capacity. Parallel technology can improve the versatility and flexibility of inverters, meeting the needs of practical applications. When multiple power supplies are connected in parallel, the output frequency, phase, and amplitude of each power supply must be consistent; otherwise, it will cause distortion of the system output waveform, amplitude instability, and the generation of circulating current. Therefore, parallel technology measures are needed to prevent this situation. This paper will explain the principle of the external characteristic droop method and its application in power supply parallel connection. 2. 2.1 Active and Reactive Power Analysis Using the External Characteristic Droop Method Taking two inverters connected in parallel as an example, their equivalent circuit is shown in Figure 2-1, where X1 and X2 are line impedances, U1∠φ1 and U2∠φ2 are the no-load output voltages of the inverters, and R is the load. (Full text download available for "Application of External Characteristic Droop Method in Parallel Inverter Connections ")