Control of Hybrid AC/DC Microgrid Involving Energy Storage, Renewable Energy and Pulsed Loads
Abstract
This paper proposes the coordinated control of a hybrid AC/DC power system with renewable energy source, energy storages and critical loads. The hybrid microgrid consists of both AC and DC sides. A synchronous generator and a PV farm supply power to the system’s AC and DC sides, respectively. A bidirectional fully controlled AC/DC converter with active and reactive power decoupling technique is used to link the AC bus with the DC bus while regulating the system voltage and frequency. A DC/DC boost converter with a maximum power point tracking (MPPT) function is implemented to maximize the energy generation from the PV farm. Current controlled bidirectional DC/DC converters are applied to connect each lithium-ion battery bank to the DC bus. Lithium-ion battery banks act as energy storage devices that serve to increase the system stability by absorbing or injecting power to the grid as ancillary services. The proposed system can function in both grid-connected mode and islanding mode. Power electronic converters with different control strategies are analyzed in both modes in detail. Simulation results in MATLAB Simulink verify that the proposed topology is coordinated for power management in both AC and DC sides under critical loads with high efficiency, reliability, and robustness under both grid-connected and islanding modes.
EXISTING SYSTEM:
At the same time, various utility grids and some hybrid microgrids are increasing the penetration of renewable energy resources. This growth in renewable sources increased the challenge these systems will meet due to the intermittent nature of wind and solar power. This can quickly add up to system-wide instability that can force generators to ramp up and down wildly, push grid protection gear into states it’s not meant to handle, or force the wind and solar generator to shut off altogethe. Hybrid power systems face far more challenges when operating in islanding mode than they do in grid connected mode. During islanding mode, the AC side can no longer be viewed as an infinite bus, which results in load variations adversely affecting the frequency and voltage of the system. If the system has a high penetration of renewable power, the situation can be even worse. At any time, power flow should be balanced between the AC and DC sides to maintain stability on both sides of the grid. Also, both reactive and active power in the AC side of the system should be balanced to keep the frequency and voltage stable.
PROPOSED SYSTEM:
In this paper, a hybrid AC/DC micro grid with solar energy, energy storage, and pulse load is proposed. This micro grid can be viewed as a PEV parking garage power system or a ship power system that utilizes sustainable energy and is influenced by pulse load. The system operation and power converters coordination control are studied in both grid-connected and islanding model. The power flow control of these devices serves to increase the system’s efficiency, stability, and robustness.
CONCLUSION
In this paper, a coordination power flow control method of multi power electronic devices is proposed for a hybrid AC/DC microgrid operated in both grid-connected and islanding modes. The microgrid has a PV farm and a synchronous generator that supply energy to its DC and AC side. Battery banks are connected to the DC bus through bi-directional DC/DC converter. The AC side and DC side are linked by the bi-directional AC/DC inverter. The system topology together with the control algorithms under both modes are tested with the influence of pulse loads and renewable energy farm output power variances. The simulation results show that the proposed microgrid with the control algorithm can greatly increase the system stability and robustness.
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