  Maintaining power system stability is becoming more and more challenging due
to the ever-increasing inverter-interfaced renewable penetration in power
systems. To ensure system stability during system operation and to provide
appropriate incentives in the future market-based stability maintenance
framework, it is essential to develop a comprehensive set of power system
stability constraints which can be incorporated into system operation, market
design and planning problems. In this paper, different system stability issues,
including synchronization, voltage and frequency stability, are investigated
and the corresponding stability conditions are analytically formulated as
system operation constraints. A unified framework is further proposed to
represent the stability constraints in a general form and enables effective
reformulation of the impedance-based stability metrics. All the constraints are
converted into linear or Second-Order-Cone (SOC) form, which can be readily
implemented in any optimisation-based applications, such as system scheduling,
planning and market design, thus providing significant value for multiple
system stability enhancement and studies.
