Abstract
With the increase of renewable energy in power system, the usage of a large number of converters brings safety and stability issues to power system, including lack of reliable inertia response, insufficient abilities for supporting current, voltage and frequency and lack of reliable damping to restrain oscillation. To solve these instability issues, the synchronous motor-generator pair (MGP) is proposed as a new method of grid-connection. Firstly, the main structure and application scene of MGP are analyzed. Secondly, the classical model for the MGP small signal stability is derived. Theoretical deduction proves that the MGP can provide more damping than a single generator with the same mass block. Then, 5kW MGP experimental system is built. The calculation parameters of the small signal model for the experimental system are determined by fitting experimental data repeatedly. On the basis, the calculated and measured frequency responses are compared under the same disturbance. The agreements between calculations and measurements show that the MGP small signal model can reflect damping and inertia level of MGP system. Finally, same disturbance experiment is carried out on a single-generator experimental system with the same mass block. The frequency response curves of the two modes under the same disturbance show that the MGP is more conducive to system stability.
Highlights
In recent years, renewable energy has developed rapidly
The results prove that the motor-generator pair (MGP) small signal model can reflect inertia and damping level of MGP system
The key contributions and findings of this paper are as follows: 1) Considering the lack of inertia and damping in the power grid with high penetration of renewable energy, a new grid-connection scheme of MGP is proposed based on synchronous machine theory
Summary
Renewable energy has developed rapidly. As the end of 2018, the total installed capacity of global wind power and photovoltaic has reached 1044GW [1]. Referring to the theory of synchronous generator power system stabilizer (PSS), adding additional damping controller to the converter of the wind turbine can provide proportional damping [27]. On the premise of keeping the existing electronic converter grid-connected mode unchanged, the existing research seeks the ways to improve the stability of high proportion renewable energy grid by reference to the motion equation, inertia response and excitation control PSS of synchronous machines and so on. B. APPLICATION SCENE OF MGP SYSTEM Changing traditional electronic converter grid-connected mode, MGP is a new technical method to solve instability of high proportion renewable energy grid based on synchronous machine theory. 2) In the future super-high proportion of renewable energy grid, part of renewable energy is connected to the grid through MGP, which provides a voltage and frequency reference for power electronic converters. Fault and load disturbances can be set in power grid emulator
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