Rapid assessment of maximum distributed generation output based on security distance for interconnected distribution networks

Security distance provides a quantitative approach to assess the N-1 security and its margin of distribution systems. In order to support system N-1 secure operation, distributed generations (DGs) should be used in terms of capacity credit (CC). Considering the conductor thermal constraints and voltage constraints after a substation transformer or feeder N-1 contingency, this paper proposes a rapid maximum output assessment method for DGs. With the proposed method, the system operators can better guarantee system security in the presence of active management. The concept of security distance for distribution networks is primarily decomposed into two parts: feeder security distance (FSD) and transformer security distance (TSD). Considering the correlation between the wind speed and illumination intensity, the combined output characteristics of DGs are achieved using the defined wind-photovoltaic conversion coefficient based on coordinate conversion. Then, the initial maximum DG output on each feeder section is approximately calculated by initial FSDs and TSDs. On these bases, the maximum output assessment method is proposed under uncertainties associated with DGs, loads and contingencies. Moreover, several related issues are further discussed: (a) discussion of the proposed use of DGs in terms of CC, (b) consideration of demand response in the proposed method, and (c) feasibility of the proposed method to N-2 contingency analysis. In the end, the proposed method is successfully applied to the expanded IEEE RBTS-Bus4 and a real urban distribution networks and the results verify its high performance when compared to the normal optimal method from static and dynamic views.