Development of optimal speed trajectory control strategy for electric vehicles to suppress battery aging

In order to suppress the battery aging of electric vehicles(EVs),a multi-objective optimization function is established to describe the battery aging behavior based on a high-precision battery aging model,and the state–space equation is then constructed to reveal the intrinsic relationship between vehicle speed,acceleration,and battery state-of-charge(SOC).The constructed optimization model is solved by using a sequential quadratic programming(SQP)algorithm,and based on the model predictive control(MPC)theory,the efficient real-time control of vehicle speed is achieved.Simulation results show that the developed strategy extends the battery life by 10.33%compared to the baseline strategy when the traffic flow is not involved.In the case of involving the traffic flow,the optimization results of battery aging improves as the look-ahead time period increases,while the computational burden increases.The results show that the developed strategy reduces the battery aging of the target vehicle by 33.02%compared to the preceding vehicle while meeting the real-time requirement.

Energy modeling and optimization of building condenser water systems with all-variable speed pumps and tower fans:A case study

The emergence of building condenser water systems with all-variable speed pumps and tower fans allows for increased efficiency and flexibility of chiller plants in partial load operation but also increases the control complexity of condenser water systems.This study aims to develop an integrated modeling technique for evaluating and optimizing the energy performance of such a condenser water system.The proposed system model is based on the semi-physical semi-empirical chiller,pump,and cooling tower models,with capabilities of fully considering the hydraulic and thermal interactions in the condenser water loop,being solved analytically and much faster than iterative solvers and supporting the explicit optimization of the pump and tower fan frequency.A mathematical approach,based on the system model and constrained optimization technique,is subsequently established to evaluate the energy performance of a typical dual setpoint-based variable speed strategy and find its energy-saving potential and most efficient operation by jointly optimizing pumps and tower fans.An all-variable speed chiller plant from Wuhan,China,is used for a case study to validate the system model’s accuracy and explore its applicability.The results showed that the system model can accurately simulate the condenser water system’s performance under various operating conditions.By optimizing the frequencies of pumps and tower fans,the total system energy consumption can be reduced by 12%–13%compared to the fixed dual setpoint-based strategy with range and approach setpoints of 4℃and 2℃.In contrast,the energy-saving potential of optimizing the cooling tower sequencing is insignificant.A simple joint speed control method for optimizing the pumps and tower fans emerged,i.e.,the optimal pump and fan frequency are linearly correlated(if both are non-extremes)and depend on the chiller part load ratio only,irrespective of the ambient wet-bulb temperature and chilled water supply temperature.It was also found that the oversizing issue has further limited the energy-saving space of the studied system and results in the range and approach setpoints being inaccessible.The study’s findings can serve as references to the operation optimization of all-variable speed condenser water systems in the future.