## 4 Case Study  
### Case Comparisons and Results  
To verify the effectiveness of the proposed transactive DR framework for high renewable penetrated multi-energy prosumer aggregators, a case study was conducted on a distribution network with five nodes. The network included three aggregators located at nodes 2, 4, and 5, whose parameters were taken from the literature [28; 29; 30; 31]. Node 1 released the DR demand. Comparative schemes were performed:  
(1) Scheme 1 was the proposed transactive DR framework based on the flexibility potential evaluation in Sections 2 and 3;  
(2) Scheme 2 was pre-dispatch without consideration of prosumer-operator interactions [16];  
(3) Scheme 3 is the transactive DR framework without the flexibility potential evaluation. Table 2 lists the system operating cost for the three prosumer aggregators of schemes 1-3. For every scheme, the operating cost of each prosumer aggregator is different based on their capacity for flexible resources. Compared with schemes 2 and 3, the proposed transactive DR framework based on the flexibility potential evaluation can cost-effectively explore resource flexibility in order to fulfil the DR requirements:  
Figure 3: Flowchart of the proposed transactive DR framework. Comparison with scheme 2 or previous literature without prosumer-operator interactions: prosumer-operator interactions when the distribution system is overloaded can reduce the requirements for building new energy plants. By coordinating various prosumer aggregators to manage and adjust the timing of flexible loads, the large daily fluctuations can be smoothed out. Since flexible multi-energy resources are fully utilized in scheme 1, the operating cost of scheme 1 is decreased by up to 7.6% compared with scheme 2. Comparison with scheme 3 or previous literature without a flexibility potential evaluation: when facing the DR tasks from the grid, the flexible loads of prosumer aggregators could be programmed to turn ON/OFF to meet the consumer's desire for comfort and cost-savings. The flexibility potential evaluation in scheme 1 can offer choices and information in order to give consumers greater control over personal energy use. As for scheme 3, the prosumer aggregators have to equally respond to the DR tasks, and the operating cost even increases. Figures 4-6 show the positive and negative flexibility of the energy storage system according to the proposed flexibility potential evaluation. The flexibility of BES is different from other prosumer aggregators because of different electricity storage capacities, while the positive flexibility of the gas tanks and heat tanks is the same during hour 2-20 and hour 13-16. Though energy storage system can technically provide both positive and negative flexibility, they tend to provide positive flexibility in the morning hours and negative flexibility in the night hours. Figures 7 and 8 show the positive and negative flexibility of CHP and P2G according to the proposed flexibility potential evaluation. The positive and negative flexibility of CHP and P2G are different with the energy storage systems. While the CHP tends to offer positive flexibility, P2G tends to offer positive and negative flexibility based on its pre-dispatch optimal operation. It can also be found that the negative flexibility of CHP is at a low level, which is subject to the energy storage system and the forced OFF state in Figure 7. Conversely, the positive flexibility of CHP is given when CHP is limited by the ON state. Figures 9-11 show the electrical, thermal, and gas DR results of the three prosumer aggregators. It can be seen that the proposed DR load can successfully accommodate the uncertainties of the RESs and loads. With the proposed flexibility potential evaluation to consider the flexibility difference of three aggregators as an important objective, the DR loads can provide more flexibility for each aggregator. Figures 12-14 show the battery SOC, gas storage SOC, and P2G of schemes 1-3.