Total load energy supply capability and security level classification of integrated power and natural gas systems considering N‐1 contingency of power system

Summary The coupling between the power system and natural gas system becomes more and more intensive, so it is necessary to study the security of integrated power and natural gas systems. This paper proposes the concept of total load energy supply capability (TLESC) for integrated power and natural gas systems. Then, a nonlinear optimization model is presented to calculate this TLESC. Normal operation of the power system and natural gas system, and the N‐1 contingency of the power system are considered. Piecewise linearization is used to linearize nonlinear models to obtain a uniquely effective solution. Then, the impact of contingencies on the TLESC is measured by the load change rate and the contingency load rate. A method for dividing the security level of the integrated power and natural gas systems is proposed. The N‐1 check is used to judge whether the integrated power and natural gas systems are secure to operate. If the N‐1 check is not satisfied, load loss rate, threshold crossing, hazard index, and so on are used to measure the insecure operation state; If the N‐1 check is satisfied, security margin index, power flow‐gas flow index, comprehensive margin index are used to measure the secure operation state of the system. An integrated 6‐bus power system and 7‐node natural gas system, an integrated 39‐bus power system and 20‐bus natural gas system and the modified IEEE 118‐bus power system and a 40‐node natural gas system are carried out to validate the effectiveness of the proposed model and security level classification method are verified by simulation examples. The modified 6‐bus power system and 7‐node natural gas system are shown in Figure 1; and Figures 2–6 shows part of the calculation results in modified IEEE 39‐bus power system and the Belgian 20‐bus natural gas system.