How circulating current flows between inverters?

The circulating current flows between the inverters when the reference voltages difer according to the dead time, imperfect symmetry in hardware, and dependent control of parallel inverters. Diferent zero-sequence voltages Vzsv1 and Vzsv2 are injected into each module based on the discrepancy of the reference voltages from Eq. (10).

What causes circulating current in a parallel inverter?

The cir-culating current is generated by diferences in each inverter, such as hardware parameters and control process. The circulating current deteriorates the output current quality and degrades the reliability of the parallel system [12–15].

What are circulating current reduction methods for modular inverters?

The reduction methods for modular inverters are compared in terms of eficiency, performance, and reliability. The possible approaches for circulating current reduction are categorized into three groups–hardware, control, and modulation. Each reduction method is discussed according to the category.

What are the types of circulating current in parallel inverters?

There are two types of circulating current in parallel inverters: low-frequency and high-frequency circulating current. The low-frequency cir-culating current is parameter related, such as imperfect sym-metry in hardware and dependent control of parallel inverter dead time [18, 19].

Do parallel inverters suppress circulating currents?

It can be clearly seen that the circulating currents among different inverters are well suppressed, and the stable operation of the parallel system are guaranteed with equal and unequal reference currents. When comparing with Fig. 12, Fig. 18, the magnitudes of circulating currents become slightly larger.

How does circulating current affect the power rating of a parallel inverter?

The circulating current deteriorates the output current quality and degrades the reliability of the parallel system [12–15]. Harmonic components of circulating current can influence the inverter life cycle, limiting the power rating of the total parallel-connected inverter [16, 17].