Using Sampled-data Modeling Method to Derive Equivalent Circuit and Linearized Control Method for Dual-Active-Bridge Converter

Currently, high-performance power conversion requirements are of increasing interest in microgrid applications. In fact, isolated bidirectional dc-dc converters are widely used in modern dc distribution systems. The dual active bridge (DAB) dc-dc converter is identified as one of the most promising converter topology for the mentioned applications, due to its benefits of high power density, electrical isolation, bidirectional power flow, zero-voltage switching, and symmetrical structure. This study presents a power management control scheme in order to ensure the power balance of a dc microgrid in stand-alone operation, where the renewable energy source (RES) and the battery energy storage (BES) unit are interfaced by DAB converters. The power management algorithm, as introduced in this work, selects the proper operation of the RES system and BES system, based on load/generation power and state-of-charge of the battery conditions. Moreover, a nonlinear robust control strategy is proposed when the DAB converters are in voltage-mode-control in order to enhance the dynamic performance and robustness of the common dc-bus voltage, in addition to overcoming the instability problems that are caused by constant power loads and the dynamic interactions of power electronic converters. The simulation platform is developed in MATLAB/Simulink, where a photovoltaic system and battery system are selected as the typical RES and BES, respectively. Assessments on the performance of the proposed control scheme are conducted. Comparisons with the other control method are also provided.

Download Full-text

Synchronous Machine Winding Modeling Method Based on Broadband Characteristics

Applied Sciences ◽

10.3390/app11104631 ◽

2021 ◽

Vol 11 (10) ◽

pp. 4631

Author(s):

Yu Chen ◽

Xiaoqing Ji ◽

Zhongyong Zhao

Keyword(s):

Equivalent Circuit ◽

High Frequency ◽

Equivalent Circuit Model ◽

Black Box ◽

Synchronous Machine ◽

Circuit Model ◽

Modeling Method ◽

Experimental Results ◽

Box Model ◽

Impedance Curve

The accurate establishment of the equivalent circuit model of the synchronous machine windings’ broadband characteristics is the basis for the study of high-frequency machine problems, such as winding fault diagnosis and electromagnetic interference prediction. Therefore, this paper proposes a modeling method for synchronous machine winding based on broadband characteristics. Firstly, the single-phase high-frequency lumped parameter circuit model of synchronous machine winding is introduced, then the broadband characteristics of the port are analyzed by using the state space model, and then the equivalent circuit parameters are identified by using an optimization algorithm combined with the measured broadband impedance characteristics of port. Finally, experimental verification and comparison experiments are carried out on a 5-kW synchronous machine. The experimental results show that the proposed modeling method identifies the impedance curve of the circuit parameters with a high degree of agreement with the measured impedance curve, which indicates that the modeling method is feasible. In addition, the comparative experimental results show that, compared with the engineering exploratory calculation method, the proposed parameter identification method has stronger adaptability to the measured data and a certain robustness. Compared with the black box model, the parameters of the proposed model have a certain physical meaning, and the agreement with the actual impedance characteristic curve is higher than that of the black box model.

Download Full-text

Continuous control of sampled data systems with robustness against bounded measurement errors

Transactions of the Institute of Measurement and Control ◽

10.1177/0142331217716982 ◽

2017 ◽

Vol 40 (10) ◽

pp. 3125-3133

Author(s):

Milad Ghanbari ◽

Masoud Bahraini ◽

Mohammad Javad Yazdanpanah

Keyword(s):

Measurement Errors ◽

Control Method ◽

Linear Time ◽

Continuous Control ◽

Data Systems ◽

Sampled Data ◽

Linear Time Invariant ◽

Experimental Implementation ◽

Time Invariant ◽

Ultimate Bound

This paper considers the design of a generalized hold function to be used for the control of sampled-data systems. The proposed method suggests a continuous controller for sampled data systems. Ultimate boundedness of the proposed method in the presence of bounded measurement errors is also shown for linear and nonlinear systems. In linear time invariant cases, a cost function is suggested for the sake of ultimate bound minimization. In addition, this can answer how we choose a sensor for a real system to get a desired control outcome. Eventually, the effectiveness of the proposed control method is investigated through simulation and experimental implementation.

Download Full-text