There is an emerging application, which uses a mixture of batteries within an energy storage system. These hybrid battery solutions may contain different battery types. A dc-side cascaded boost converters along with a module-based distributed power sharing strategy has been proposed to cope with variations in battery parameters such as, state-of-charge (SOC) and/or capacity. This power sharing strategy distributes the total power among the different battery modules according to these battery parameters. Each module controller consists of an outer voltage-loop with an inner current-loop where the desired control reference for each control-loop needs to be dynamically varied according to battery parameters to undertake this sharing. As a result, the designed control bandwidth (BW) or stability margin of each module control-loop may vary in a wide range, which can cause a stability problem within the cascaded converter. This paper reports such a unique issue and thoroughly investigates the stability of the modular converter under the distributed sharing scheme. The paper shows that a cascaded PI control-loop approach cannot guarantee the system stability throughout the operating conditions. A detailed analysis of the stability issue and the limitations of the conventional approach are highlighted. Finally in-depth experimental results are presented to prove the stability issue using a modular hybrid battery energy storage system prototype under various operating conditions.

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Control of Cascaded DC–DC Converter-Based Hybrid Battery Energy Storage Systems—Part I: Stability Issue

A cascaded dc–dc boost converter is one of the ways to integrate hybrid battery types within a grid-tie inverter. Due to the presence of different battery parameters within the system such as, state-of-charge and/or capacity, a module-based distributed power sharing strategy may be used. To implement this sharing strategy, the desired control reference for each module voltage/current control loop needs to be dynamically varied according to these battery parameters. This can cause stability problem within the cascaded converters due to relative battery parameter–variations when using the conventional proportional–integral (PI) control approach. This paper proposes a new control method based on Lyapunov functions to eliminate this issue. The proposed solution provides a global asymptotic stability at a module level avoiding any instability issue due to parameter variations. A detailed analysis and design of the nonlinear control structure is presented under the distributed sharing control. At last thorough experimental investigations are shown to prove the effectiveness of the proposed control under grid-tie conditions.

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Control of Cascaded DC–DC Converter-Based Hybrid Battery Energy Storage Systems—Part II: Lyapunov Approach

This paper proposes a predictive control algorithm that includes conduction-mode detection for power factor correction (PFC) converter. In PFC converters, the line current is usually distorted because of the characteristics of the proportional-integral (PI) current controller. To improve the quality of the current, the PI current controller requires additional circuits or algorithms. However, because of the optimal duty cycle determined by estimating the next-state current in both the continuous-conduction mode and the discontinuous-conduction mode, the proposed predictive control method has a fast dynamic response and accuracy compared to the PI current-control method. Moreover, the proposed algorithm can detect the conduction mode without any additional circuitry or mode-detection algorithm using the characteristic of the optimal duty cycle calculated by the predictive control. These advantages of the proposed algorithm improve the quality of the line current for PFC converters. We verify the proposed method by performing experiment using a 1.5-kW PFC converter.

Predictive Control Algorithm Including Conduction-Mode Detection for PFC Converter

This paper proposes the design and simulation of a DC-DC Boost converter employing PID controller, enhancing overall performance of the system. The main objective of a DCDC converter is to maintain a constant output voltage despite variations in input/source voltage, components and load current. Designers aim to achieve better conversion efficiency, minimized harmonic distortion and improved power factor while keeping size and cost of converter within acceptable range. A simple PID (Proportional, Integral and Derivative) controller has been applied to a conventional Boost converter and tested in MATLAB-Simulink environment achieving improved voltage regulation. The proposed closed loop implementation of the converter maintains constant output voltage despite changes in input voltage and significantly reduces overshoot thereby improving the efficiency of the converter. The output of this investigation has the potential to contribute in a significant way in electric vehicles, industry, communication and renewable energy sectors. Keywords— DC-DC converter; voltage regulation; Boost converter; overshoot; PID; Block Diagram Reduction; stability

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Design and Simulation of a DC - DC Boost Converter with PID Controller for Enhanced Performance

Traditional slope compensation (SC) method is an effective way to control fast-scale instabilities present in peak current mode (PCM) controlled boost PFC converters. However, with the SC method, envelope of inductor current deviates from a desired sinusoid especially near the zero crossings, which causes the system power factor to reduce to values lower than what is possible without compensation. To tackle this problem we propose a hybrid dynamic compensation (HDC) scheme, which incorporates a combination of zero-perturbation dynamic compensation (ZPDC) and ripple compensation. The proposed HDC scheme can suppress the fast-scale instabilities and also ensure average inductor current tracks a desired sinusoidal reference which is not possible with the ZPDC scheme alone where only the peak inductor current can track a desired sinusoidal signal. Furthermore, with the proposed HDC scheme the total harmonic distortion (THD) and power factor (PF) are improved in comparison to the SC and ZPDC schemes as well as to the case without compensation. Moreover, operating range of a control parameter is determined analytically subject to some assumptions. Extensive simulation and experimental results are provided to validate the theoretical analysis and the feasibility of the proposed HDC scheme.

Improvement of Stability and Power Factor in PCM Controlled Boost PFC Converter With Hybrid Dynamic Compensation

Regarding the non-limit-cycle instabilities, which commonly exist in the feedback-controlled switching power converters, a new zero-perturbation dynamical compensation method is proposed based on a simplified self-stable dynamical compensation condition in this paper. With a current-mode Buck converter as the subject of investigation, the corresponding self-stable perturbation control equation is given. At the same time, the system stability boundary is obtained based on the investigation of the system eigenvalues, and hence, the working range of control parameters is determined. Finally, the presented simulation and experiment results reveal that the new zero-perturbation dynamical compensation controller is easily realized with an analog circuit and it will not sacrifice the working range of the original reference current compared with the traditional slope compensation. Copyright © 2013 John Wiley & Sons, Ltd.

Limit-cycle stable control of current-mode dc-dc converter with zero-perturbation dynamical compensation

Energy storage materials to modulate indoor microclimates are needed to improve energy efficiency and for human comfort. Of these, phase-change material (PCM) is considered a very useful material because of its excellent latent heat energy storage. For application, some synthetic porous materials for supporting PCM are usually not friendly enough for people and housing environments due to their non-degradation characteristics. Hence, to develop an eco-friendly porous material is needed in order to encapsulate PCM composites that are always expected in indoor applications. In this work, heat-treated bamboo bricks were delignified to provide a delignified bamboo (DB) matrix. A phase-change composite was then fabricated by impregnating DB with polyethylene glycol (PEG) polymer. Impregnation was carried out under wet conditions to ensure the regular arrangement of the DB structure so as to achieve dimensional stability. The final DB/PEG composite was investigated for dimensional stability, load rate, latent heat, and phase-change temperature. Results showed that the DB matrix could be easily impregnated with PEG polymer under wet conditions, and the DB/PEG composite was found to have high enthalpy and a large phase-change temperature interval. Moreover, the composite was found to be a good regulator of indoor temperature and a stable dimension with a snow-white appearance. In summary, this DB/PEG composite is an energy storage material with the potential to modulate ambient indoor temperature and reduce building energy consumption.

https://www.mdpi.com/2073-4360/15/7/1727/pdf?version=1680182708

Shuang Lang

Papers

Improvement of Stability and Power Factor in PCM Controlled Boost PFC Converter With Hybrid Dynamic Compensation

Limit-cycle stable control of current-mode dc-dc converter with zero-perturbation dynamical compensation

Dimensionally Stable Delignified Bamboo Matrix Phase-Change Composite under Ambient Temperature for Indoor Thermal Regulation