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Sensorless Predictive Current Controlled DC–DC Converter With a Self-Correction Differential Current Observer

For a sensorless predictive current controlled boost dc-dc converter, its small-signal model that contains a number of parasitic parameters, is derived in this paper. This model indicates that the type of system becomes type 0 even with the correction of voltage loop proportional-integral controller, leading to the existence of output voltage steady-state error. Then a self-correction differential current observer (SDCO) is proposed to eliminate this steady-state error and gain high transient response speed. The self-correction part of the SDCO makes the system become type 1 to achieve no steady-state error for output voltage, whereas the differential part can guarantee that the intermediate calculation results do not overflow. By carrying out a series of simulation verifications, further investigation proves that the proposed algorithm has good robustness. Finally, the effectiveness of the proposed algorithm is verified by experimental results.

Sensorless Predictive Peak Current Control for Boost Converter Using Comprehensive Compensation Strategy

For a sensorless predictive-peak-current-controlled boost converter, the output voltage steady-state error cannot be eliminated by voltage loop PI controller. The basic cause for this is investigated through analysis and theoretical approaches. To eliminate the voltage steady-state error and achieve high-accuracy current estimation, a comprehensive compensation strategy is proposed. First, a compensation algorithm for output voltage sampling is introduced. It can not only effectively eliminate the output voltage steady-state error but also guarantee current observer convergence. The compensation schemes for component parasitic parameter effects and switching delay are also investigated. With this comprehensive compensation strategy, both the system transient response and current estimation accuracy are greatly improved. Finally, the effectiveness of the proposed algorithm is verified by experimental results.

Digital Sensorless Current Mode Control Based on Charge Balance Principle and Dual Current Error Compensation for DC–DC Converters in DCM

For discontinuous conduction mode (DCM) dc–dc converters with digital sensorless current mode (DSCM) control, an observed current error occurs, owing to a low-accuracy current observer. Moreover, a reference current error occurs due to a low-accuracy current controller or a finite dc gain of current loop. Conventionally, the observed current is compensated to increase current regulation accuracy, whereas the reference current error is neglected. However, for charge balance principle (CBP)-based DSCM (CBP-DSCM) control, this paper proves that the reference current should be compensated in a same quantity to that of observed current. Otherwise, single or unequal compensation leads to output voltage steady-state error. For this reason, a dual current error compensation strategy for CBP-DSCM control is proposed. It compensates the errors in a same quantity through a current error observer, which considers parasitics and calculates the current errors without approximation. To verify the proposed strategy, small-signal models with parasitics for both the converter and the controller are constructed by differential functions of key variables. Furthermore, converter stability is analyzed at typical operation condition, while the stability at various operation conditions is verified through robustness analysis. Finally, simulations and experimental results verify the analysis and the improved transient response of the converter.

Multiloop Minimum Switching Cycle Control Based on Nonaveraged Current Discrete-Time Model for Buck Converter

Exploring high-performance controller for buck converter is challenging since it can be easily affected by converter model accuracy. In this paper, a novel nonaveraged current discrete-time (NCD) model is proposed, in which inductor current is expressed as time-varying equations during switch-on and switch-off states. It achieves higher accuracy than the conventional averaged model at high-frequency range, thus can be used to optimize high-speed controller design. Based on the NCD model, a multiloop minimum switching cycle (MMSC) control strategy, composed of output feedback (OF), line feed forward (LFF), and reference feed forward (RFF) loops, is proposed and tuned for buck converter operating in continuous conduction mode. Mutual influences among three loops are considered and eliminated by specifically designed LFF and RFF compensations, which adapt the OF compensation. With consideration of sampling and calculation delays, relationship between transient switching cycles and geometric center of controller poles is discovered from a calculated output voltage error series. Furthermore, theoretical minimum switching cycles are calculated by moving the center inside the unit cycle of complex plane, which ensures system stability. Moreover, load/line transient response and reference tracking time are simultaneously optimized to the minimum switching cycles. Effectiveness of the controller is proved by converter closed-loop pole/zero plots, transient response simulations, and experiments.

Online Inductor Parameters Identification by Small-Signal Injection for Sensorless Predictive Current Controlled Boost Converter

In a sensorless predictive current controlled boost converter, parameterizing the inductor plays an important role in controller performance. In this paper, a solution for inductor parameters online identification is investigated. A small-signal injection strategy is proposed to create a transient state, and convergence problem of inductance identification in steady state can be avoided. Then, a charge balance current observer (CBCO), derived from capacitor current charging balance concept, is adopted to estimate the inductor current for inductance identification. Since inductance is not used in CBCO, current estimation is not affected by inductance identification error. Because of rank-deficient problem, instead of identifying inductor parasitic resistance solely, the inductor equivalent parasitic resistance is derived. By applying it into the conventional current observer for current control loop, the accuracy of current estimation can still be guaranteed since more parasitic effects are included. To improve the accuracy of inductance identification, a load identification method is investigated. Furthermore, the effect of the equivalent series resistance of output capacitor on the proposed algorithm is analyzed. Finally, its effectiveness is verified by experimental results.

Bayesian estimation in dynamic framed slotted ALOHA algorithm for RFID system

This paper develops a novel dynamic framed slotted ALOHA (DFSA) algorithm based on Bayesian estimation to improve the throughput of the radio frequency identification (RFID) system. At first, four types of anti-collision algorithms for tag identification are analyzed. Then, the proposed DFSA based on Bayesian estimation is deduced and introduced. Compared with the conventional DFSA algorithms, this algorithm takes advantage of the evidence in previous frames as the a priori information of the current frame which can end up with more precise estimation of tag number and rational frame length adjustment. Finally, the common simulation tool from Matlab is used to demonstrate the effectiveness of the proposed new algorithm for the average throughput improvements of the RFID system.

An optimal current observer for predictive current controlled buck DC-DC converters.

In digital current mode controlled DC-DC converter, the conventional current sensor is either costly or has low accuracy. Thus, current observer, which could be realized based on digital circuit itself, is an ideal substitute for conventional current sensors. However, the observed current may diverge because of parasitic parameters. In this paper, an optimal current observer is proposed to solve the problem. Employing the optimal current observer based predictive current control, a buck converter, which shows preferable transient response than PID controlled converter is implemented. The effectiveness of the optimal current observer is experimentally demonstrated.