For the future development of an integrated energy system (IES) with ultra-high penetration of renewable energy, a planning model for an electricity-hydrogen integrated energy system (EH-IES) is proposed with the considerations of hydrogen production and storage technologies. In this EH-IES, a reasonable power to heat and hydrogen (P2HH) model with startup/shutdown constraints and a novel model of seasonal hydrogen storage (SHS) are proposed for the first time. To cope with the challenges faced by EH-IES, we use a combination of stochastic and robust optimization approaches to address the generation-load uncertainties, making the planning results robust. The N-1 contingency of crucial devices is further considered to make the system reliable. Additionally, the effects of the annual ratios of different seasons on the optimal allocation and operation of SHS are investigated. The min-max-min model with binary variables is solved by a nested column-and-constraint generation algorithm. Finally, case studies verified the advantages and effectiveness of the proposed model and planning method.

In the future integrated energy market, the traditional centralized planning method cannot solve the planning problem for mul-ti-stakeholder integrated energy systems (MSIESs). To cope with this problem, this paper proposes a synchronously decentralized adaptive robust programming (SDARP) model for MSIESs based on the analytical target cascading (ATC) algorithm. In this model, different stakeholders are planned in parallel under the source-load uncertainties, aiming at minimizing the annual investment and op-eration costs, and fully taking into account the interactive heat-ing/cooling power transmitted by the district heating/cooling net-work. In each stakeholder, the column-and-constraint generation (C&CG) algorithm is used to address the robustness problems in the three-layer adaptive robust programming (ARP) model. In addi-tion, a tractable alternating optimization procedure (AOP) is used to solve the non-convex SDARP model with finite convergence. Case studies verify the superiority and effectiveness of the SDARP meth-od in dealing with the planning problem of MSIESs.

When a fault occurred in a distribution system, the load center located with distributed generation (DG) will have a significant impact upon protection. And the impact depends on the number, location and size of injected DG. This paper focuses on studying the effect of DG upon conventional protection. Starting with the analysis of the coordination relationship between relays to obtain the capacity requirement for single DG connected to radial distribution system, the calculation is extended to several DGs being interconnected. Examples will be used to demonstrate various issues and solutions.

With high sensitivity and strong tolerance capability for the fault resistance, the fault component-based directional relay (FCBDR) has drawn considerable attention from industry and academia. However, the best application environment for FCBDR no longer exists when considering the large-scale connection of the doubly fed induction generator (DFIG)-based wind farms. Through a detailed analysis of the superimposed impedance of DFIG, this paper reveals that the performances of FCBDRs may be shown negatively impacted by the fault behaviors of DFIG when the crowbar protection inputs. In addition, this paper proposes a mitigation countermeasure to deal with those issues. The proposed countermeasure takes advantage of the different superimposed impedance features of DFIG compared with that of the synchronous generator (SG) to enhance the adaptability of the conventional FCBDRs. Extensive simulation results show that the proposed countermeasure can differentiate the fault direction clearly under different fault conditions.

This paper proposes a novel geometry-based spatial branching strategy for conic non-convex equations in integrated electricity-gas systems. The proposed strategy is embedded in a spatial branch-and-bound algorithm to solve optimal electricity-gas flow problems for their exact solutions. Numerical results on multiple test cases verify the effectiveness and superiority of the proposed method.

The fast frequency response (FFR) function in renewable energy source (RES)-based power stations has proved to be able to improve the frequency stability of power systems with high RES penetration significantly. However, most current FFR functions in photovoltaic (PV) power stations typically show power response deviations and unnecessary power loss issues that are caused by inadequate station power distribution strategies. This is particularly important in cases where the power must be increased when the system frequency shows a downward disturbance. This paper proposes a new distribution strategy for FFR in PV power stations and studies related distribution strategies, system structures, calculation algorithms, function execution effect, and active power regulation technology. The proposed approach uses a proportional distribution strategy based on an evaluation of the real-time potential maximum power capability values of the subarrays or generation regions, which are evaluated using a few reference inverters located in every subarray or region. Real-site deployments and tests have been completed in PV power stations to verify the effectiveness of this new distribution strategy, and the proposed FFR solution using this distribution strategy has demonstrated strong performance and potential for wider application scenarios.