Wangxin Huang

An Online Battery Impedance Measurement Method Using DC–DC Power Converter Control

This paper presents a simple online impedance measurement method for electrochemical batteries, including lithium-ion, lead-acid, and nickel-metal-hydride chemistries. By using the proposed online impedance measurement method, there is no need to disconnect the battery from the system or to interrupt system operation, and there is no need to add ac signal injection circuits, costly response measurement, and analysis circuits/devices. In practical battery-powered systems, a power converter is usually used to interface the battery with the load for voltage/current regulation purposes. In this paper, through the control of the power converter and duty-cycle perturbation, the ac impedance of the battery can be determined. The proposed method provides a low-cost and practical solution for the online measurement of the ac impedance of batteries. Moreover, the proposed method can be either continuously or periodically performed without interrupting the normal operation of the battery system and the power converter. In addition, this paper provides an example where the obtained impedance data are utilized for online state-of-charge estimation of lithium-ion batteries. The proposed online impedance measurement method is validated by experiments conducted on a 2.6-Ah 18650-size lithium-ion battery interfaced to the load via a bidirectional dc-dc boost/buck converter.

Distributed battery energy storage system architecture with energy sharing control for charge balancing

This paper presents a distributed battery energy storage architecture where the cells in the battery pack are decoupled from each other by connecting each cell with a lower power (smaller) DC-DC power converter. In addition to providing voltage regulation for the DC bus, these small DC-DC power converters are utilized to achieve state of charge (SOC) balancing among the cells by employing a proposed charge balancing controller that is based on energy sharing concept. As a result, no additional charge balancing circuits and controllers are needed in order to transfer charges between the cells of the battery pack. A system simulation model based on the proposed energy storage system architecture is developed in Matlab®/Simulink® in order to verify the feasibility and functionality of the proposed charge balancing controller.

Automatic calibration method for DC-DC power converter with sensorless adaptive voltage positioning controller

An automatic calibration method for a previously proposed sensorless adaptive voltage positioning (SLAVP) controller is presented in this article. The SLAVP scheme achieves AVP control without the need for current sensing and sampling required by conventional AVP schemes. However, the accuracy of the SLAVP control scheme is sensitive to the power path equivalent DC resistance value, Req. An automatic calibration method is developed in this article in order to calibrate the SLAVP control law when Req varies as a result of components aging or component replacement after initial design, for examples. The theoretical basis of the automatic calibration method is presented along with proof-of-concept experimental results for verification.

Tuning of a digital proportional-integral compensator for DC-DC power converter

This paper presents a scheme to manually tune a digital Proportional-Integral (PI) controller (TunePI scheme) to achieve optimized dynamic performance of a DC-DC power converter. Based on a previously proposed compensated-error-signal-based auto-tuning of compensator gain to achieve optimized gain for a given set of other compensator parameters, i.e. zero(s) and pole(s), the paper presents a new scheme that will tune the complete set of a PI compensator parameters to result in a design with an optimum set of parameters for improved dynamic performance. This paper focuses on discussing the TunePI scheme and presenting theoretical and experimental results that employ the TunePI scheme to manually tune a digital PI compensator. This will be used as the base for a future work to develop a controller that is able to auto-tune the PI compensator during the power converter operation (online auto-tuning).

CCM–DCM Power-Multiplexed Control Scheme for Single-Inductor Multiple-Output DC–DC Power Converter With No Cross Regulation

Single-inductor multiple-output (SIMO) switching dc–dc power converter architecture is a cost-effective alternative to multiple individual switching power converters solution in many power distribution system applications where multiple voltage rails are required at reduced cost. However, with multiple output voltage rails coupled to the same switching node, the SIMO power converters suffer from cross regulation between the multiple outputs, which complicates the closed-loop controller design of the SIMO converter and degrades regulation performance. In this paper, a power-multiplexed (PM) control scheme is proposed aiming to completely decouple the operations of multiple outputs from one another. The proposed PM control scheme results in eliminating the cross regulation among the multiple outputs while maintaining desired voltage regulation performance for each output under both steady-state and dynamic operations. Low-cost microcontroller or analog circuitries can be used to implement the proposed controller. Experimental proof of concept prototype results verify the feasibility and advantages of the proposed controller.

Load-voltage-based single-sensor MPPT controller for multi-channel PV systems

The paper presents a Maximum Power Point Tracking (MPPT) controller for a multi-channel (N-Channel) Photovoltaic (PV) solar system which requires only one voltage sensor and no current sensors. The N-channel Load Voltage Single-Sensor MPPT (LV-SS-MPPT) controller is able to track the MPP of each solar panel using only one output voltage value in the N-channels and is able to provide a very good tradeoff between size, cost, and tracking speed. Compared to a conventional N-channel MPPT system which requires N voltage sensors, N current sensors, 2N ADCs (or an ADC with 2N channels) and N MPPT controllers along with the associated conditioning circuitries, the proposed method only requires one voltage sensor, one ADC and one MPPT controller and is able to converge closer to the maximum lower power point of the load when the channels of the system are subject to non-uniform and/or mismatching conditions.

Linearized sensorless adaptive voltage positioning controller for DC-DC boost power converter

Adaptive voltage positioning (AVP) has been used in DC-DC switching power converters for powering integrated circuits due to its advantages of utilizing allowable output voltage tolerance while decreasing the output filter capacitance requirement, and achieving faster transient response. Most of the AVP control schemes in the published literature require current sensing and sampling circuits which increase cost, size, complexity and can cause inaccuracies of AVP operation. A SLAVP controller of DC-DC buck converter is recently proposed in the literature which can achieve AVP control based on the linear relationship between the output current value and the duty cycle value while using the duty cycle value as an indicator of current value. However, this SLAVP control scheme cannot be directly applied to DC-DC boost converter topology because of two reasons. One is the RHP (Right Half Plane) zero of boost converter which might yield system stability issues and ringing effects during light to heavy load transients. Second, the relationship between the output current value and the duty cycle value of the DC-DC boost converter is nonlinear. This paper proposes a linearized sensorless AVP (L-SLAVP) control scheme which successfully addresses the second issue. The theoretical basis of the proposed scheme is given and a simulation model of boost converter with L-SLAVP controller is developed in MATLAB®/SIMULINK® environment for verification and evaluation.

DCM control scheme for single-inductor multiple-output DC-DC converter with no cross-regulation

Single-inductor multiple-output (SIMO) switching DC-DC power converter architecture is a cost-effective alternative to multiple individual switching power converters solution in many power distribution system applications where multiple voltage rails are required. However, with multiple output voltage rails coupled to the same switching node, the SIMO power converters suffer from cross regulation among the multiple outputs, which complicates the closed-loop controller design of the SIMO converter and degrades performance. In this paper, an inductor continues conduction mode (DCM) power-multiplexed control (PM-DCM control) scheme is proposed aiming to completely decouple the multiple outputs from one another. The proposed PM-DCM control scheme results in eliminating the cross regulation among the multiple outputs while maintaining desired voltage regulation performance for each output under both steady-state and dynamic operations. Moreover, low-cost microcontroller or analog circuitries can be used to implement the proposed controller. Simulation and preliminary experimental results are given to verify the feasibility and advantages of the proposed concept.

DC-DC power converter with a modified control scheme to improve load transient response

A modified control scheme is presented in this paper to improve the load transient response of DC-DC power converter by utilizing a previously proposed auxiliary circuit which is capable of operating in both boost mode to discharge the output capacitor during load step down transient, and in buck mode to charge the output capacitor during load step up transient. The proposed modified control scheme for the auxiliary circuit is based on the output voltage peak detection, preset thresholds and zero crossing time information. This scheme achieves significant improvement in load transient response while eliminating the controller performance sensitivity to component values tolerances and complex calculations that could result in undesired transient response. A simulation model is built in MATLAB®/SIMULINK® software package to validate the functionalities and advantages of the proposed control scheme.

Small-signal modeling and controller design of energy sharing controlled distributed battery system

Abstract This paper presents small-signal modeling, analysis and closed-loop controller design guidelines for a distributed battery energy storage system with energy sharing controller which has recently been presented in the literature in order to achieve cell balancing with high cell balancing speed and energy efficiency. The derived small signal models provide deeper insight into the dynamics of the energy sharing controlled battery system under different operating modes, including discharge mode, constant current charging mode and constant voltage charging mode. Based on the derived small signal models, closed-loop controller design guidelines are provided based on rule-of-thumb frequency-domain design criteria. The small signal models and designed controllers are validated by MATLAB®/SIMULINK simulation and experimental prototype results.