Renewable energy hydrogen production technology is an effective way to improve the utilization of renewable energy and alleviate the problem of wind and light abandonment. However, there are many challenges in the system structure design and "Source-Load-Storage" coordination control strategy for large-scale, megawatt-scale renewable energy hydrogen production. In this paper, a hybrid wind-solar-energy storage hydrogen production system based on Medium Voltage Direct Current (MVDC) structure is proposed. HOMER software is used to plan and study the storage capacity to achieve longterm power balance and matching of the system. In addition, A decentralized coordinated control energy management system with active power following and state of charge (SOC) recovery capability is proposed and implemented for transient power regulation. An electromagnetic transient simulation was established in PSCAD/EMTDC, and semi-physical experiments were designed using StarSim to verify the effectiveness of the control strategy. Theoretical analysis and experiments show that the island MVDC network with decentralized coordinated control has technical feasibility in realizing hydrogen production from renewable energy in the 20MW level class. In addition, the power consumed by the load can realize the seconds level tracking of the output power of renewable energy.

The pulse load of an integrated power system (IPS) ship can produce very high power intermittently in a short period of time. Owing to the limited DC bus capacitance, the periodic pulse load charging and discharging process can make the IPS system state variables have a periodic alternating process during electromagnetic transients, especially at the bus voltage. In order to alleviate this problem, it is necessary to find a suitable control strategy. At first, this article establishes a mathematical model of DC bus voltage dynamics and propulsion motor load. Then, a flexible energy scheduling algorithm is proposed to coordinate the propulsion motor load and the pulse load based on the flexibility of IPS energy scheduling and the concept of virtual inertia. This algorithm can adaptively change the virtual inertia of the DC bus according to the pulse load power level and the propulsion motor load level to mitigate the impact of the pulse load on the IPS system. At the same time, the algorithm is also distributed and has little impact on the propulsion system. Finally, the effectiveness of the algorithm is verified through the mixed simulation of PSCAD and MATLAB and the hardware in the loop test.

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In the medium voltage direct current (MVDC) shipboard grid, the inherent inertial support from the DC capacitors is too small to resist step changes or fluctuations from the high power pulse load and propulsion load, which results in lower DC voltage quality. This study proposes a decentralised control algorithm for the MVDC shipboard hybrid energy storage system (HESS) to enhance the onboard survivability. This algorithm adjusts the droop control coefficient based on the bus voltage change rate adaptively, meanwhile the voltage differential signal processing and filtering are implemented by the trace differentiator. In addition, the proposed algorithm also has state-of-charge (SOC) balancing and SOC recovery abilities between multiple groups of energy storage devices. The parameter selection principle are analysed, and a variety of working conditions are simulated and verified in PSCAD. Theoretical analysis and simulation show that, HESS can achieve good power distribution and SOC management performance without communication compared to fixed droop coefficient control strategies, and the dynamic characteristics of bus voltage have been significantly improved.

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