Xin Dai

/spl mu/-Synthesis for Frequency Uncertainty of the ICPT System

A μ-controller is designed based on the structured singular value with regard to the frequency uncertainty of a real inductively coupled power transfer (ICPT) system. Due to system-parameter variations (such as system load) and nonlinear features of ICPT systems, the operating frequency will be perturbed accordingly. Uncertainty in the operating frequency will contribute to electromagnetic interference and power losses, and even instability of ICPT systems. To fulfill a robust stability and robust performance (RSRP) design, a generalized state-space averaging model for a nominal ICPT system is established by developing the equivalent circuit equations and expanding the related circuit variables as the Fourier series. A linear fractional transformation of this nominal model and its uncertainty is discussed to generate a standard configuration for μ-synthesis. The D-K iteration method is proposed for the “optimal” RSRP design. Computer simulation and a practical experiment are conducted to verify the RSRP of the μ-synthesis control system to ensure that the μ-synthesis algorithm is effective for ICPT systems.

An Accurate Frequency Tracking Method Based on Short Current Detection for Inductive Power Transfer System

Frequency drifting is a common problem in an inductive power transfer (IPT) system. Conventional autonomous oscillation method for maintaining soft switching is challenged due to the drawbacks of feedback delay and disturbance, resonant failure, and requirements of additional start-up circuit. A novel frequency tracking method based on short current detection is proposed for IPT applications. In addition, an instantaneous short current detection method utilizing cheap comparator is proposed. Furthermore, a fast and accurate tracking method is proposed to calculate the frequency mismatch and make a correction. The method can realize accurate frequency correction in several oscillation periods. Furthermore, the method is simple and economic for hardware implementation. Finally, the results of the experiment and comparison results verified the frequency tracking method.

Dynamic parameters identification method for inductively coupled power transfer system

In inductively coupled power transfer (ICPT) system, due to load and coupling parameters dynamic variation, primary resonant system parameters often drift from inherent operating point and lead to drastic decrease of power transfer capability and efficiency. In order to identify dynamically variation of system parameters, this paper put forwards system dynamics parameters identification method based on energy analysis. The method sets up energy supply, storage and dissipation function and energy equilibrium equations in primary resonant tank. And system reflection impedance solving function is given in analytic form as well. Furthermore, with the reflection impedance identification, this paper presents load parameters identification method. The identification methods are derived from energy perspective to avoid complex system modeling and requirements of high speed sampling system. Only zero crossing points sample data of resonant variables are required in system identification process. The identification is beneficial for system controller design. The identification methods are verified by experiments results.

Extended stroboscopic mapping (ESM) method: A soft-switching operating points determining approach of resonant inverters

This paper proposes an extended stroboscopic mapping (ESM) method for analyzing soft-switching operating points of resonant inverters. The essential idea of the proposed method is treating the operating period of traditional stroboscopic mapping model as a variable and employing fixed-point theory to find the soft-switching operating points. The method consists of four simple and easy-to-implement steps and can accurately determine the periods and steady-state responses of all possible steady-state soft-switching operating points of resonant inverters. A series tuned inductively coupled power transfer (ICPT) system is taken as an example to test the proposed method. Both simulation and experimental results have proved the validation of the proposed ESM method.

Study on multiple resonant points control strategy of contactless power transfer system using neural network

This paper presents a power control strategy based on multi-resonant operating points, which is realized by multilayer feedforward neural network applying back-propagation algorithm. The full-bridge contactless power transfer system and magnetizing current of the transmitter on primary side are respectively used as research object and control variable. After batch-learning and training, the converged network determines alternating operating duty cycle of each resonant operating point in one cycle. By controlling magnetizing current, it can fulfill the dynamic regulation of transmission power, and increase the energy transfer efficiency. Simulation results show that in the control strategy, magnetizing current on the primary side can be stabilized at any set value for given range, and system has some disturbance restraint performance, satisfied with contactless power transfer system control demands.

Study on robust controller design for inductively coupled power transfer system

In an Inductively Coupled Power Transfer (ICPT) system, there are two approaches, namely terminal control and source control, to obtain constant voltage output. The source control is beneficial to reduce unnecessary power losses and realize optimal operation. However, due to nonlinear characteristic of ICPT system, it is difficult to set up a nonlinear robust controller. This paper presents an extended Generalized State Space Averaging (GSSA) model with detachment of real part and imaginary part to avoid appearance of complex coefficient matrices in the modeling. Because the GSSA model is an approximation model, the paper defines the condition to guarantee stability equivalence between the GSSA approximation model and actual ICPT system and provides proof. Furthermore, the robust controller design method on the basis of the GSSA model is proposed and proven as well. The modeling and controller design method were verified by simulation results.

Analysis and optimization on power transfer capability of contactless power transfer systems with multi-load

In order to optimize the power transfer capability of a contactless power transfer (CPT) system with multi-load, this paper has analyzed the existence condition of the maximum power transfer capability of a CPT system with a certain topology and parameters based on impedance analysis. In addition, a procedure of optimized design is given according to the need of the power and efficiency requirement of a CPT system factually. This method has realized the optimized control of power transfer capability and efficiency by optimizing the input voltage and mutual inductance. Finally, this criterion is justified via an experiment.

Study on modeling and simulation of Inductively Coupled Power Transfer system with bi-directional energy transfer mode

In Inductively Coupled Power Transfer (ICPT) system, attribute to unidirectional energy transfer, there are many problems such as energy feedback difficultly and low efficiency brought by system open-loop running. This paper put forwards a novel contactless energy bi-directional transfer mode to realize energy exchange between transmitter and receiver. The paper presents a bi-directional energy conversion topology and set up its equivalent circuit and piece-wise state space model. The simulation results show that system resonant state have low harmonic components. Its benefit to improve system efficiency and minimize EMI interference. The bi-directional energy transfer mode can be used in energy exchange between mobile devices and energy feedback from mobile device to power grid to improve system efficiency.

Load and Mutual Inductance Identification From the Primary Side of Inductive Power Transfer System With Parallel-Tuned Secondary Power Pickup

An important feature of an inductive power transfer (IPT) system is its power transfer efficiency and capability can be significantly affected by the load and the magnetic coupling variations. Therefore, identifying the load and the mutual inductance is essential to improve the system performance. This paper proposes a load and mutual inductance identification method for IPT systems with parallel-compensated power pickups based only on the information detected from the primary side. The proposed method can be implemented for primary resonant circuits whether they are series or parallel tuned, or with a hybrid compensation, such as an LCL configuration. An identification model is established according to the steady-state characteristics of the system. Identification results are obtained based on mathematical derivations and analyses. The proposed identification method is realized without any extra communication or control, and both the simulation and experimental results have verified its feasibility.

An Interference Isolation Method for Wireless Power and Signal Parallel Transmissions on CPT Systems

A novel interference isolation method is proposed by using several designed coils in capacitive power transfer systems as isolation impedances. For each designed coil, its stray parameters such as the inter-turn capacitance, coil resistance and capacitance between the coil and the core, etc. are taken into account. An equivalent circuit model of the designed coil is established. According to this equivalent circuit, the impedance characteristic of the coil is calculated. In addition, the maximum impedance point and the corresponding excitation frequency of the coil are obtained. Based on this analysis, six designed coils are adopted to isolate the interference from power delivery. The proposed method is verified through experiments with a power carrier frequency of 1MHz and a data carrier frequency of 8.7MHz. The power and data are transferred parrallelly with a data carrier attenuation lower than -5dB and a power attenuation on the sensing resistor higher than -45dB.