Parallel restoration is a way to accelerate the black-start procedure of power systems following a blackout. An efficient sectionalizing scheme can reduce the restoration time of a system, taking into account the black-start ability, generation-load balance of subsystems, restoration time of branches, start-up time of generating units, and effects of dispatchable loads and faulted devices. Solving the sectionalizing problem is challenging since it needs to handle a large number of Boolean variables corresponding to the branches and nonlinear constraints associated with system topology. This paper investigates power system sectionalizing problem for parallel restoration to minimize the system restoration time (SRT). A novel sectionalizing method considering the restoration of generating units and network branches is proposed. Firstly, the minimum spanning tree (MST) algorithm is used to determine the skeleton network of a power system. Secondly, the number of subsystems is determined according to the number of black-start units. Based on the skeleton network, candidate boundary lines among subsystems are identified. Then, constraints are evaluated to identify feasible sectionalizing schemes. Except commonly used constraints on power balancing and black-start units, this paper also considers using dispatchable loads to meet the minimum output requirements of generating units. Finally, the sectionalizing scheme with the minimum SRT is selected as the final solution. The effectiveness of the proposed method is validated by the IEEE 39-bus and 118-bus test systems. The simulation results indicate that the proposed method can balance the restoration time of subsystems and minimize the SRT.

High voltage direct current (HVDC) transmission systems have been used for interconnection among multiple power grids. As a result, the conventional AC power systems are transforming into AC-DC hybrid power systems. In this paper, a parallel restoration method for AC-DC hybrid power systems is proposed. First, the effects of line-commutated-converter-based (LCC) and voltage-source-converter-based (VSC) HVDC systems on service restoration are explored. The startup characteristics of HVDC systems are analyzed. Second, an optimization model for service restoration of AC-DC hybrid power systems is developed, aiming at maximizing the generating power and minimizing the restoration time. The startup constraints of HVDC systems are incorporated into the proposed model. Third, a graph-theoretic algorithm is proposed to obtain a near-optimal parallel restoration scheme, verified by power flow calculations. An 11-bus test system is used to illustrate the effects of using HVDC systems for system restoration and a modified IEEE 39-bus test system is used to verify the effectiveness of the proposed parallel restoration method. The simulation results indicate that the proposed method can make full use of the benefits of HVDC systems, allocate cranking power flexibly during the parallel restoration, and reduce the restoration time.

Hydrogen energy is now a crucial technological option for decarbonizing energy systems. Comprehensive utilization is a typical mode of hydrogen energy deployment, leveraging its excellent conversion capabilities. Hydrogen is often used in combination with electrical and thermal energy. However, current hydrogen utilization modes are relatively singular, resulting in low energy utilization efficiency and high wind curtailment rates. To improve energy utilization efficiency and promote the development of hydrogen energy, we discuss three utilization modes of hydrogen energy, including hydrogen storage, integration into a fuel cell and gas turbine hybrid power generation system, and hydrogen methanation. We propose a hydrogen energy system with multimodal utilization and integrate it into an electrolytic hydrogen–thermal integrated energy system (EHT-IES). A mixed-integer linear programming (MILP) optimization scheduling model for the EHT-IES is developed and solved using the Cplex solver to improve the operational feasibility of the EHT-IES, focusing on minimizing economic costs and reducing wind curtailment rates. Case studies in northwest China verify the effectiveness of the proposed model. By comparing various utilization modes, energy storage methods, and scenarios, this study demonstrated that integrating a hydrogen energy system with multimodal utilization into the EHT-IES offers significant technical benefits. It enhances energy utilization efficiency and promotes the absorption of wind energy, thereby increasing the flexibility of the EHT-IES.

The first task of parallel power system restoration is to sectionalize the blackout system into multiple subsystems. This paper applies the complex network community discovery theory into this sectionalizing problem and proposes an improved label propagation algorithm-based sectionalizing method considering the system topology and operation before blackouts. Firstly, each blackstart (BS) unit bus is marked with a different subsystem label. A label propagation matrix is calculated based on the active power of branches before the blackout. Then, to avoid the label oscillation, a novel label impact strategy considering the influence of the bus label itself is developed to improve the label propagation matrix. The buses’ labels propagate to neighboring buses as the improved label propagation matrix until they do not change. The initial sectionalizing strategy is obtained through classifying the buses with the same label in the same subsystem. Finally, the sectionalizing constraints are used to evaluate the feasibility of the initial strategy. For the initial strategy that does not satisfy the constraints, a refining method to minimize the absolute value of active power exchange among subsystems is proposed to determine the final sectionalizing strategy based on it. Case studies on IEEE 39-bus and IEEE 118-bus test systems verify the effectiveness of the proposed method. The results indicate that the proposed method has advantages in creating strongly connected subsystems.