State Of Charge Recovery Research Articles

A Decentralized Control Strategy for Autonomous Transient Power Sharing and State-of-Charge Recovery in Hybrid Energy Storage Systems

This paper proposes a decentralized power management strategy for hybrid energy storage systems to achieve transient power sharing and state-of-charge (SoC) recovery simultaneously. A virtual capacitance droop control strategy with an autonomous SoC recovery loop is proposed for energy storage (ES) with fast dynamic response, and the conventional virtual resistance droop control method is employed to regulate ES with slow dynamic response. The hybrid battery/supercapacitor (SC) system is taken as an application example. With the proposed method, load power is autonomously split into high-frequency and low-frequency parts to be compensated by SC and battery. Meanwhile, SC SoC is automatically recovered and this enables continuous operation of the SC as a power buffer without mode change or performance tradeoff. A design guideline is developed to ensure desired transient power sharing dynamics and SoC recovery with negligible interactions. Both simulations and experiments are conducted to validate the effectiveness of the proposed strategy and analytical results.

Hierarchical Control of Hybrid Energy Storage System in DC Microgrids

Hybridization of energy storages (ESs) with different characteristics takes advantages of all ESs. Centralized control with high-/low-pass filter (LPF) for system net power decomposition and ESs' power dispatch is usually implemented in hybrid ES system (HESS). In this paper, hierarchical control of HESS, composed of both centralized and distributed control, is proposed to enhance system reliability. The conventional HESS centralized control is refined with implementations of online iteration, secondary voltage regulation, and autonomous state-of-charge (SoC) recovery. ESs' power references are iteratively generated to maximize the utilization of ES ramp rates and power capacities. Secondary voltage regulation and autonomous SoC recovery are applied to minimize bus voltage deviation and limit slack terminal SoC variation, respectively. In case of communication failure, a novel algorithm for HESS distributed control is proposed to retain system operation. Bus voltage is regarded as the global indicator for system power balance, and droop relationships are imposed for ES control. System net power decomposition and ESs' power dispatch are realized with localized LPFs. SoC recovery in distributed control is implemented by tuning the threshold voltage of a slack terminal. A laboratory-scale dc microgrid is developed to verify the proposed hierarchical control of HESS.

An operation algorithm with state of charge recovery for a parallel-type hybrid vehicle

In this work, an algorithm for the operation of a hybrid powertrain is proposed for a parallel hybrid electric vehicle (HEV). The operation algorithm suggested in this work yields the operating points where the operational cost of the HEV is minimal at each state of charge (SOC). The operational cost of an HEV is calculated considering both the cost of fossil fuel consumed by the engine and the cost of electricity consumed by the electric motor. A weighting function of SOC, which is inversely proportional to the SOC, is applied to the estimation of electricity cost. By the effect of a weighting function of the SOC, it is expected that the algorithm has the property of SOC recovery. Computer simulations are carried out in order to test the suggested algorithm, and simulation results show that the final SOC is recovered to the middle band of the SOC as the operation of the HEV is continued, regardless of initial SOC values.

Modeling and simulation for hybrid electric vehicles. I. Modeling

For pt.I see ibid., vol.3, no.4, p.235-43 (2002). Hybrid electric vehicle (HEV) simulation is conducted based on the model developed for a parallel HEV built in the University of Tennessee, Knoxville (UT-HEV). The HEV simulation is a parametric analysis of the power control schemes and vehicle performance. Major parameters are evaluated for the vehicle driven under the standard urban and highway driving schedules. The results indicate that current configuration of the UT-HEV NEON has superb capability for battery state of charge (SOC) recovery while meeting the velocity request of the given driving schedules. Recommendations are given from the simulation for optimal performance in light of the HEV power control, capability for SOC recovery through regeneration and regenerative braking, as well as velocity, acceleration and range performance.