Abstract
Digital control has been widely used in dual active bridge (DAB) converters, which are pivotal parts of electric vehicles and distributed generation systems. However, the time delays introduced by the digital control could affect the performance or even lead to the instability of the digitally controlled DAB converter. In order to reduce the effect of time delay on the dynamics and stability of the system, the model predictive control (MPC) of the DAB converter is proposed based on the discrete-time iteration in this paper to compensate for the digital control delay. According to the obtained discrete-time model, the instability mechanism of the MPC DAB converters with different parameters is revealed. The simulation and theoretical analysis indicate that this method could reduce the influence of the digital control delay and increase the stable range of the system compared with the conventional control strategy. The proposed method is also revealed to have a strong compatibility and portability. In addition, the accurately predicted stability boundaries can be applied to the practical parameter design and guarantee the stable operation of the system. The experimental results are consistent with the theoretical analysis and verify the proposed method.
Highlights
In recent years, bidirectional dc–dc converters are widely utilized in renewable energy storage systems [1,2,3], the distribution grid [4,5] and power electronic transformers [6]
The dynamic phasor model-based model predictive control dual active bridge (DAB) converter is obtained in Reference [27]
It is remarkable that all the Floquet multipliers remain inside the unit cycle, which indicates the stable operation of the DAB converter
Summary
Bidirectional dc–dc converters are widely utilized in renewable energy storage systems [1,2,3], the distribution grid [4,5] and power electronic transformers [6]. The dynamic phasor model-based model predictive control DAB converter is obtained in Reference [27]. Energies 2019, 12, 3103 first order coefficient of the inductor current were utilized because of the calculation limit of the digital controller, which is not conducive to the dynamic performance of the DAB converter. The model predictive control of the DAB converter is derived based on the discrete-time iteration of the state variables to eliminate the one-step delay effect. The discrete-time model of the MPC DAB converter was obtained to analyze the complex dynamics of the system. The parameter spaces and the stability margins of the model predictive control compared with the original control method were obtained, which can provide good guidance for the practical design and analysis.
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