An Active Equalization Method for Lithium-ion Batteries Based on Flyback Transformer and Variable Step Size Generalized Predictive Control

Abstract

The inconsistency in large-scale battery pack significantly degrades the performance of electric vehicles. In order to diminish the inconsistency, the study designs an active equalization method comprising of equalizer and equalization strategy for lithium-ion batteries. A bidirectional flyback transformer equalizer (BFTE) is designed and analyzed. The BFTE is controlled by a pulse width modulation (PWM) controller to output designated balancing currents. Under the purpose of shortening equalization time and reducing energy consumption during the equalization process, this paper proposes an equalization strategy based on variable step size generalized predictive control (VSSGPC). The VSSGPC is improved on the generalized predictive control (GPC) by introducing the Step Size Factor. The VSSGPC surmounts the local limitation of GPC by expanding the control and output horizons to the global equalization process without increasing computation owing to the Step Size Factor. The experiment results in static operating condition indicate that the equalization time and energy consumption are reduced by 8.3% and 16.5%, respectively. Further validation in CC-CV and EUDC operating conditions verifies the performance of the equalizer and rationality of the VSSGPC strategy.

A Battery Cell Equalisation System Based on a Supercapacitors Tank and DC–DC Converters for Automotive Applications

“…Conductive/switching/total power loss 2.12 W/4.1 W/6.2 W ( 40), ( 41), ( 42), (43) Primary side demagnetisation peak/average current 1 A/0.4 A ( 45), (47) Selected primary side diodes (D1, D2, Figure 9) STTH812…”

“…Flyback converters have a significant application for battery cell equalisation [43][44][45], giving simple and robust topology with galvanic primary-to-secondary isolation. In addition to this, the secondary side active rectification has the potential to improve efficiency [43]. The topology could be based on the primary side current control, avoiding the feedback circuit [44].…”

A Comprehensive Review of Various Topologies and Control Techniques for DC-DC Converter-Based Lithium-Ion Battery Charge Equalization

“…A single switch is used for energy transfer in a unidirectional type, while two switches are used in a bidirectional type. An integrated fyback converter having a switching array is used to distinguish between overcharged and undercharged cells [67,68].…”

A Compensated Peak Current Mode Control PWM for Primary-Side Controlled Flyback Converters

“…Because the flyback converter has a simple structure and does not require a secondary side output inductor, it has considerable advantages in size and cost. Based on the above advantages, the flyback converter is widely used in low power applications [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]-especially in LED lighting [8][9][10] and battery balancing control [11][12][13][14][15][16] to show its many advantages. With the advancement of digital technology and the cost of microcontrollers has dropped significantly.…”