Motor-Generator Pair for Improving the Transient Stability of Grid-Connected Renewable Energy

The renewable energy grid-connection has a negative influence on the transient stability of the power grid for the lack of voltage support and damping control capability. This paper aims to study the functions of the novel MGP system on improving the stability of renewable energy power grid with its advantages of synchronous machines. First of all, the structure and motion equation of grid-connected renewable energy via MGP is given. Then the mechanism of improving voltage stability is analyzed through the phase diagram of two synchronous machines. It turns out that the output reactive power of the generator can respond to voltage disturbance spontaneously. Afterwards, the function of excitation voltage on damping frequency disturbance is studied. In order to test the real characteristics of MGP, the grid voltage drop and load increase are conducted on the experimental platform, respectively. According to the results, grid-connected PV via MGP can perform well on providing reactive power support spontaneously and the effects of damping the frequency oscillation can be improved through the optimization of excitation voltage.