Design and Experimental Validation of a Battery/Supercapacitor Hybrid Energy Storage System Based on an Adaptive LQG Controller  
[PERSON]  
1 Escuela de Ingenieria Electrica y Electronica, Universidad del Valle, Cali 760042, Colombia; 1 [EMAIL_ADDRESS]  
[PERSON]  
2 Facultad de Minas, Universidad Nacional de Colombia, Medellin 050041, Colombia; [EMAIL_ADDRESS]  
[PERSON]  
2 Facultad de Minas, Universidad Nacional de Colombia, Medellin 050041, Colombia; [EMAIL_ADDRESS]  
[PERSON]  
1 Escuela de Ingenieria Electrica y Electronica, Universidad del Valle, Cali 760042, Colombia; 1 [EMAIL_ADDRESS]  
[PERSON]  
3 Departamento de Electronica y Telecomuniciones, Instituto Tecnologico Metropolitano, 3 Medellin 050013, Colombia; [EMAIL_ADDRESS]  
power and fast response are required; in this case, the HESS should include supercapacitors (SC) or flywheels, as discussed in [8]. Another application is the EV, where the HESS must have a high-energy capacity; therefore, batteries must be included [4,8,9]. Moreover, other applications could profit from HESSs: integration of sources based on renewable energy [7,10], power quality improvement [11, 12, 13, 14, 15], uninterrupted power supply (UPS), and public transport vehicles powered by electricity [16]. Some commercial products provide HESS systems encapsulated as a single device; for example, CRE New Energy Technology offers a battery-ultracapacitor hybrid energy storage unit with high peak currents [17], which is designed to be used as a battery replacement in buck-up units. The same company recently developed a new scalable hybrid supercapacitor-battery unit designed for industrial environments [18], in particular for driving motors. However, these units have a close architecture, hence it is not possible to analyze the performance in battery protection, peak current regulation, or system stability. Three major types of HESSs have been developed: passive, semi-active, and fully active [19,20]. Passive HESSs are highly efficient and cheap since they do not include power converters, but passive HESSs are uncontrolled systems whose behavior depends on the ESS parameters. In semi-active HESSs, an ESS is connected to the DC bus, while a DC/DC bidirectional converter interfaces the DC bus with other ESSs. This configuration offers a good trade-off between cost and performance. Finally, the fully active topology decouples all ESSs from the DC bus using power converters, thus achieving the maximum benefit from the ESSs but at the expense of complex controllers; moreover, this topology is expensive and has low efficiency in contrast with the other two HESS types. There are multiple works reported in the literature dealing with HESS controllers. For example, in [21] is reported a fully active HESS formed by a battery and an SC, which are interfaced with the DC bus using bidirectional boost converters. In that work, an equalization algorithm based on model predictive control (MPC) governs the converters, where the MPC considers the state of charge (SoC) of both battery and SC. Moreover, classical PI controllers regulate the voltage and current of the boost converters following a second-level droop control. Finally, that system is validated with simulation and experimental tests. Another fully active HESS is reported in [22], which is formed by a battery, an SC, and a fuel cell, connected to a DC bus. This HESS is regulated using a central super-twisting sliding mode control, where the current reference is given by an energy management unit based on fuzzy logic. The primary control is applied to an unidirectional boost converter and two bidirectional boost converters, and the controller performance is verified using Matlab/Simulink and hardware-in-the-loop (HIL) emulation on a C2000 Delfino. There is no experimental validation on a real power system. Similar to [22], the work reported in [23] proposes a fully active HESS formed by three power sources: a battery, an SC, and a PV panel array.