Dynamic Modeling and Stability Analysis of Onboard DC Power System for Hybrid Electric Ships

This paper presents the dynamic modeling and stability analysis of the onboard DC power system, applicable to hybrid electric ships. The system topology is established with a special focus on the integration of the energy carriers with power electronic converters. The modeling of the AC/DC rectifier, DC/DC converter, filters and energy storage systems (ESS), such as battery and supercapacitor, is investigated. AC/DC rectifier is modeled with decoupling control through an LCL filter, and the DC/DC converter modeling is compared with the state-space averaging method and generalized averaging method. The performance of the integrated model is presented both in charging mode and in discharging mode of the energy storage system and the results show the effectiveness of the controllers and the power regulation of the ESSs. In the end, the limitation of the load is obtained by the stability analysis

An Intelligent Power and Energy Management System for Fuel Cell/Battery Hybrid Electric Vehicle Using Reinforcement Learning

Hybrid electric vehicles powered by fuel cells and batteries have attracted significant attention as they have the potential to eliminate emissions from the transport sector. However, fuel cells and batteries have several operational challenges, which require a power and energy management system (PEMS) to achieve optimal performance. Most of the existing PEMS methods are based on either predefined rules or prediction that are not adaptive to real-time driving conditions and may give solutions that are far from the actual optimal solution for a new drive cycle. Therefore, in this paper, an intelligent PEMS using reinforcement learning is presented, that can autonomously learn the optimal policy in real time through interaction with the onboard hybrid power system. This PEMS is implemented and tested on the simulation model of the onboard hybrid power system. The propulsion load is represented by the new European drive cycle. The results indicate that the PEMS algorithm is able to improve the lifetime of batteries and efficiency of the power system through minimizing the variation of the state of charge of battery

A discrete-time tool to analyze the stability of weakly filtered active front-end PWM converters

International audienceThis paper will discuss the stability of a system constituted by a DC/DC converter supplying a DC microgrid on which is connected a tightly controlled device behaving as a Constant Power Load with its low damped LC input filter. The input filter cutoff frequency can be high in transportation systems where small passive components are employed. The dynamic behavior of the entire system in high frequency range is often not studied with the classical tools based on average modeling. Here, the system is modeled by a discrete-time model of the converter including control variables. The impact of the LC filter on the stability of the system is investigated. Moreover, a stabilizer is designed to extend the stability domain. Experimental results, conducted on a laboratory test-bench are given in order to validate the proposed model and stabilizer

Stability analysis of hybrid AC/DC power systems for More Electric Aircraft

International audienceThis paper presents the stability analysis of a hybrid AC/DC power distribution system, for embedded applications, particularly for more electric aircraft. In the studied system, a balanced AC source supplies the hybrid system, and a DC distribution system feeds multi-converter controlled loads. The load converters are tightly controlled, behaving as constant power loads with low damped LC input filters. An analytical model, taking to account the AC and DC characteristics of the system, is developed to investigate the dynamic behavior of the system. The AC system is modeled in a d-q synchronous reference frame. The stable and unstable operating points are identified using the proposed method, and then, the stability pattern of the system is established. The impacts of the constant power loads and interactions between the source and the load converters on the system's stability are studied. Experimental tests, conducted on a laboratory scale microgrid, validate the analytical system analysis

Dynamic analysis of an on-board DC distribution system with active stabilizer

International audienceStability of onboard dc power systems is influenced by nonlinear behavior of converter-controlled loads with constant power characteristics. This nonlinear dynamics, in line with reduced size input filters used in transportation systems, has a degradation effect on the dynamic performance and stability of the system. This paper addresses stability study of a dc power system with an active stabilization system. Different load power dynamics are implemented to demonstrate the impacts of slow and fast load dynamics on the stability of the system. Performance of the stabilizer, in steady state and transient, is also investigated through a series of experimental tests

Discrete-time modelling, stability analysis, and active stabilization of dc distribution systems with constant power loads

International audienceThis paper presents the stability analysis of a dc distribution system supplying multi-converter loads. The load converters are tightly controlled, behaving as constant power load with low damped LC input filters. The dynamic behavior of the system in high frequency range is often not studied with the classical tools based on average linearization. Whereas, small LC filters with high cutoff frequency are common in transportation systems. Therefore, in this paper, the stability analysis of the system is established based on a discrete-time model of pulse width modulated converters considering the switching effect and intrinsic nonlinearities of the system. The impacts of the filter parameters and interactions among the loads are investigated with the discrete-time method. Moreover, an active stabilizer is included in the system model in order to extend the stability domain. Experimental results, conducted on a dc distribution system, are given in order to validate the analytical stability analysis and stabilizer

Energy management and stabilization of a hybrid DC microgrid for transportation applications

International audiencePower electronics-based AC/DC microgrids are attractive for clean energy applications, and are the enabling technology for hybrid energy systems in the more electric transportation. In such hybrid energy systems, storage units like battery and supercapacitor (SC) are used to store the surplus energy and to regulate the DC bus voltage. In on-board electric power systems, the converter controlled loads act as constant power loads (CPLs), imposing fast dynamics to the system. In this paper, a simple power control approach is proposed to provide the energy management and to ensure the stable operation of the system in the presence of CPLs. Furthermore, a laboratory prototype is built in order to validate the performance of the controller and the energy management strategy. The control system is implemented on dSPACE real-time cards. The simulated control scenarios are then experimented with the hardware prototype

Electromagnetic Oscillation Origin Location in Multiple-Inverter-Based Power Systems Using Components Impedance Frequency Responses

Existing impedance-based stability criterion (IBSC) for electromagnetic stability assessment of multiple-grid-connected-inverter (GCI)-based power systems suffers from several limitations. First, global stability feature is hard to be obtained if Nyquist-criterion-based IBSC is used. Second, heavy computational burdens caused by either right-half-plane (RHP) poles calculation of impedance ratios or nodal admittance matrix construction can be involved. Third, it's not easy to locate the oscillation origin. This article aims to overcome the aforementioned three limitations of the existing IBSC. First, frequency responses of the load impedance and source admittance defined at each node in a selected components aggregation path are obtained by aggregating individual components, from which imaginary parts of RHP poles of these load impedances and source admittances are directly identified without knowing analytical expressions of these load impedances and source admittances. Then, based on the Nyquist plots of minor loop gains, stability features of these selected nodes are obtained. Finally, if some nodes are unstable, the oscillation origin is located based on numbers of the RHP poles of these load impedances and source admittances. Compared to the existing IBSC, the presented method can assess global stability apublishedVersio