## 6 Case Study
### Configuration of Storage Devices  
The microgrid system described in this study operates in electric-isolated mode and in a self-sufficient manner. The overall time cycle of the scheme is planned to be 10 years, i.e., \(Y=10a\). The 10 th year is considered the target year. It is also assumed that installation occurs in the first year of the planning horizon [30]. The penalty coefficient of the relevant algorithms is 0.03, the population scale is 80, the inertia factor is 0.5, the self factor is 2, the global factor is 2, the mutation probability is 0.05, the iteration number \(N\) is 1000, and the error precision \(\sigma\) is 0.01. Four different cases were employed to analyze the impacts of different configurations on the selection and reliability of different microgrid planning schemes. In Case 1, the system lacks the backup of energy storage devices and meets energy demands through the cooperation of relevant equipment units within the microgrid system. The distributed PV power with high volatility cannot be stabilized effectively. Accordingly, energy supply reliability is poor under random fault due to the lower degree of coupling among energy sources. A reasonable configuration of energy storage devices in the microgrid can effectively stabilize the output randomness of renewable energy sources, reduce the capacity redundancy of the energy production devices, improve the energy supply reliability, and ensure an economical system performance. The HS device is a backup resource that is critical for heat supply reliability. The ES device not only improves the reliability of the power supply, it also converts energy sources through CAC when necessary. Power storage devices improve the coupling among energy sources in the microgrid system and indirectly enhance the energy supply reliability of other energy sources in the system. Typical optimal configuration schemes under Case 4 were selected for further analysis in accordance with their favorable annual reliability. Preconceived CCHP faults were simulated to explore the impacts on all of the power, heating, and cooling resources with multi-energy coupling on energy supply reliability under different energy demands. This study selected the peak and valley periods of power loads, heat loads, and cold loads in a typical year, simulated CCHP outage and failure, and then evaluated the LOEE and outage impact time expectation (\(r_{\text{e}}\)) of the multi-energy microgrid under different energy demands. A pre-arranged outage time according to the reference value of failure repair, 24 h, was employed to ensure that the expected failure time did not affect the results. The evaluations are listed in Table 8, where e-peak, h-peak, and c-peak denote the peak periods of power loads, heat loads, and cold loads, respectively; likewise, the valley periods of loads are represented. When performing pre-arranged outage maintenance of a traditional single energy network, the goal is typically to avoid load peaks. However, the comparison of reliability indexes at different typical periods under the same operation mode suggests that although the pre-arranged valley outage value does partially ensure sufficient energy supply, it significantly impacts other energy supplies under multi-energy coupling and energy supply cycle circumstances. The valley value of power loads may actually have a greater impact on cold loads than the simulated peak failure value. On this basis, the energy supply reliability economic indicator was further analyzed to determine the optimal maintenance time for major equipment in the microgrid system. Through the calculation, the preconceived accident simulation is conducted at the moment \(t=3500\), and can get \(I_{\text{min}}=1332.631\) CNY. On account of the high PV output in the simulation period, ES can effectively reduce the loss of energy supply. Extra power can be employed for cold loads through CAC, and heat loads can be transferred completely through GHP. Hence, the influence on the microgrid system at this moment is lower than that of other moments.