Operation control strategy of series-parallel hydraulic hybrid vehicle

A series-parallel hydraulic hybrid system applied to public buses is put torwaro, ano parameters of key components are analyzed and determined. Energy management strategy based on logic thresh- old is designed which is aimed at efficient operation of the overall system considering the operational characteristic of the components and taking the curves of engine, hydraulic pump/motor and hydrau- lic pump as the main design basis; regenerative control strategy which makes regenerative brake sys- tem and frictional brake system work harmoniously is designed to raise recovery rate of regenerative brake energy. System dynamic modeling and simulation results show that the energy control strategy designed here is able to adapt system to changes of working condition and switch the operating mode reasonably. The regenerative braking control strategy is effective in raising the utilization of energy and improving fuel economy.

A dual control strategy for power sharing improvement in islanded mode of AC microgrid

Parallel operation of inverter modules is the solution to increase the reliability,efficiency,and redundancy of inverters in microgrids.Load sharing among inverters in distributed generators(DGs)is a key issue.This study investigates the feasibility of power-sharing among parallel DGs using a dual control strategy in islanded mode of a microgrid.PQ control and droop control techniques are established to control the microgrid operation.P-f and Q-E droop control is used to attain real and reactive power sharing.The frequency variation caused by load change is an issue in droop control strategy whereas the tracking error of inverter power in PQ control is also a challenge.To address these issues,two DGs are interfaced with two parallel inverters in an islanded AC microgrid.PQ control is investigated for controlling the output real and reactive power of the DGs by assigning their references.The inverter under enhanced droop control implements power reallocation to restore the frequency among the distributed generators with predefined droop characteristics.A dual control strategy is proposed for the AC microgrid under islanded operation without communication link.Simulation studies are carried out using MATLAB/SIMULINK and the results show the validity and effective power-sharing performance of the system while maintaining a stable operation when the microgrid is in islanding mode.