Differentiating between plant level and inverter level voltage control to bring about operation of 100% inverter based resource grids

Recent research has resulted in the emergence of so called grid forming inverter control architectures which behave as voltage sources. However, from a fundamental electric circuit theory perspective, there are no inherent limitations that restrict the continued operation of a network with pure current sources. In this paper, the ability of current sources to bring about stable operation of a zero inertia network will be shown. Such a stable operation will be brought about using appropriate auxiliary control loops and to the author's knowledge, has not been illustrated elsewhere in research literature. Small signal stability analysis will be carried out to validate stability of this novel concept while time domain simulations carried out in electromagnetic transient (EMT) domain will be used to extend the concept to larger realistic networks. It will be shown that as the percentage of inverters increase in the power system, fast local inverter level voltage control will be crucial in dictating the stability of the power system. This signifies a paradigm shift in the manner in which voltage control is implemented in many conventional large solar and wind farms wherein today, voltage control is usually implemented in a slow manner at the plant controller level while the inverter level control is purely a reactive power control loop. With this paradigm shift, and without any further changes in inverter control structure, it will be shown that it is possible to achieve a stable and continued operation of a 100% inverter based resource grid.

Automated summary

Recent research has developed grid forming inverter control architectures that behave as voltage sources. This paper demonstrates the ability of current sources to achieve stable operation in a zero inertia network using auxiliary control loops, which has not been shown in previous research. Analysis and simulations show that fast local inverter level voltage control is crucial in ensuring the stability of the power system, indicating a paradigm shift in voltage control implementation in large solar and wind farms.