A hybrid energy-storage system (HESS), which fully utilizes the durability of energy-oriented storage devices and the rapidity of power-oriented storage devices, is an efficient solution to managing energy and power legitimately and symmetrically. Hence, research into these systems is drawing more attention with substantial findings. A battery–supercapacitor hybrid energy-storage system (BS-HESS) is widely adopted in the fields of renewable energy integration, smart- and micro-grids, energy integration systems, etc. Focusing on the BS-HESS, in this work we present a comprehensive survey including technologies of the battery management system (BMS), power conversion system (PCS), energy management system (EMS), predictive control techniques of the underlying system, application and cost-effective feasibility aspects, etc. This work reflects strong symmetry on different aspects of designing an HESS, and provides guidelines and design references for the research and application of an HESS.

Hybrid active flux estimation technique takes advantage of both the voltage model for high-speed operation and the current model for low-speed, which considerably enlarges the system operating range. However, the accuracy of the motor parameters, particularly the stator resistance, severely impacts the robustness of this technique, especially at low speeds ( $\leq 5$ % per unit). In this work, we propose a new robust hybrid active flux observer-based technique, which is simple in structure and realization, but immune to stator resistance variations. It further broadens the operation region from standstill to full speed and has fast control dynamics. The proposed solution is verified via experimental data at a lab-constructed test bench. Results confirm that the proposal achieves good control performances at both low and high speed ranges, and is robust against parameter mismatches and load disturbances.

Model-predictive control is a constrained optimization control method with superior performance than linear methods for multivariable and multiobjective control of power converters. Nonetheless, its performance is limited by model uncertainties and measurement noise. This study tackles this challenge by proposing a new hybrid parallel-cascade extended state observer (PC-ESO) with two key advantages: 1) higher disturbance rejection than the conventional linear ESO and cascade ESO (CESO) at low bandwidth and 2) better noise suppression than the conventional ESO. PC-ESO's time-domain structure and comprehensive frequency-domain analysis are presented. Furthermore, PC-ESO is applied to improve the transient disturbance rejection of CESO through a novel structurally adaptive ESO (SAESO) algorithm. The proposed SAESO provides both high-frequency noise suppression and better disturbance rejection than CESO and cascade-parallel ESO. Finally, the proposed methods are experimentally validated by the model-free predictive control of a grid-connected power converter.

DC–DC boost converters find versatile application as power conversion interfaces to renewable energy sources including wind, solar photovoltaic, fuel cell, and energy storage systems. The model predictive control (MPC) of these power converters is characterized by multivariable, constrained, optimal control with higher performance than linear control methods. However, MPC is limited by sensor measurement noise and model uncertainties. Although model-free predictive control based on the ultralocal model and conventional extended state observer (MFPC-ESO) can mitigate model uncertainties, MFPC-ESO is limited in noise suppression. Noise suppression is an important control objective in order to keep the steady state ripples bounded and guarantee the stability and robust performance of power converters. Therefore, this study proposes the novel hybrid parallel-cascade ESO, which has better measurement noise suppression than the conventional linear ESO. New higher order hybrid ESO structures are also discussed along with their detailed theoretical analyses. The generalized selection and design guidelines for robust control with measurement noise suppression using hybrid ESOs (including cascade-parallel ESO) are presented. The proposed control schemes are experimentally demonstrated for the robust MFPC of a bidirectional dc–dc boost power converter, under conditions including load, input voltage, measurement noise, and model uncertainties.

Fast and accurate fault diagnosis is important to enhance the reliability of power converters. Since both open-circuit faults in insulated gate bipolar translator (IGBTs) and diodes deteriorate power quality, diagnosis methods only focusing on IGBT failures are easily disturbed by diode failures. In this work, we propose a unified effective residual-based open-circuit fault diagnosis method for all semiconductor devices including IGBTs, clamping diodes, and freewheeling diodes in three-level neutral-point-clamped power converters. The voltage and current residuals are calculated from the mismatches between the actual current path and the estimated one, requiring solely the already existing current measurement of the system. By analyzing the variation of the voltage and current residuals in all open-circuit failure cases, the proposed diagnosis method can locate the faulty switch within several sampling periods, i.e., less than 1 ms. Finally, the proposed diagnosis method is incorporated in the model predictive current control framework. Both experimental and hardware-in-the-loop results confirm the effectiveness and robustness of the proposed diagnosis method at various operation scenarios.

Single-inductor multiple-input multiple-output (SIMIMO) dc-dc converters can integrate different input sources and supply power to multiple output loads with fewer components. This paper proposed a current-source-mode (CSM) SIMIMO dc-dc converter. By virtue of the constant inductor current, the proposed CSM SIMIMO dc-dc converter can avoid cross regulation naturally and allow the use of much simpler control strategy. The proposed configuration has the advantage of all inputs and outputs sharing a common ground and ease of expansion. Moreover, the number of the main circuit components is reduced. A CSM single-inductor dual-input dual-output (SIDIDO) dc-dc converter is constructed for illlustration. The two input sources can work independently in the event of the two input sources being disconnected. A detailed comparison of the different SIDIDO dc-dc converters is provided.