A new relative droop-gain based current sharing and voltage regulation method of DC side parallel connected rectifiers

In this paper, a new relative droop gain based current sharing and voltage regulation method of DC side parallel-connected power generation module (PGM) for Unmanned Underwater Vehicles (UUV) has been presented. Based on the concept of relative droop gain, relative lower droop gain can be achieved. To mitigate the load sharing error caused by inaccurate line impedance with lower droop gain, an adaptive impedance compensation strategy is deduced. An additional voltage control loop is also built to compensate the voltage drop of DC bus, with which the DC bus voltage can be restored to its nominal value under any load condition. Furthermore, a new zero-droop gain based current sharing and voltage control method has also been deduced in detail. With zero setting of the virtual impedance, this method can be easily implemented without the need for the prior knowledge of line impedance among the paralleled modules. The zero-droop gain based method has obvious advantages in voltage fluctuation suppression while still retaining the benefits of conventional droop-controlled PGMs such as reliability and modularity. Simulation and experimental studies are also presented to illustrate the feasibility of the proposed new droop method.