Reliability-oriented AC/DC hybrid distribution network planning: A risk-constrained approach

Abstract

The rising share of direct current (DC) loads and DC-based distributed generations (DGs) challenges the efficiency of alternating current (AC) distribution networks, thereby making hybrid AC/DC distribution networks a more flexible and economical solution. However, uncertainties in AC and DC load demands and renewable DG outputs can lead to violations in bus voltage and line loading limits, which introduces significant risks. The proposed plan includes modeling the security constraints of the problem as a combination of hard and soft constraints. Hard constraints represent strict technical requirements that must be satisfied, whereas soft con straints allow limited violations and are modeled as penalty costs associated with bus voltage deviation and line overload. These penalties are included in the objective function to internalize the cost of risk. The conditional value at risk (CVaR) criterion is employed to quantify and control risk under uncertainty. Ensuring network reliability is a critical aspect of distribution network planning, as it directly influence service continuity and overall operational resilience. Network reliability is modeled through the inclusion of outage-related costs. The overall objective function consists of investment costs, operation costs, and risk. Both risk-averse and risk-seeking strategies are examined by adjusting the weight of the CVaR component. The effectiveness of the proposed methodology is demonstrated using a test distribution network, and a sensitivity analysis is conducted on the planning problem considering both risk and reliability simultaneously under factors such as confidence level, load interruption cost, equipment cost, converter efficiency, and equipment failure rates.