Search

The trend toward higher switching frequency and larger scale of power electronic systems poses challenges for real-time simulation. This article presents an event-driven hardware-in-the-loop (ED-HIL) simulation framework that does not rely on the small fixed simulation step-size related to the switching frequency. ED-HIL framework can improve the calculation efficiency by positioning switch events and using variable simulation step-size. Further, a parallel acceleration and circuit partitioning (PACP) solver is proposed based on this framework. The PACP solver partitions the circuit with energy storage elements and ensures that the partitioning does not introduce simulation distortion by using the higher order derivatives of the energy storage elements. Meanwhile, it achieves a process-level paralleling through a shared memory architecture in order to accelerate the simulation. As a result, the proposed PACP solver based on the ED-HIL framework can achieve about three times the simulation scale of a commercial FPGA-based real-time simulator at 1/16 the hardware cost under the same conditions. An accurate real-time HIL example of a power electronic transformer with 32 switches at a switching frequency of 20 kHz has been implemented on a personal computer. The simulation results are analyzed by comparing with experiment, offline software, and commercial real-time simulator. [ABSTRACT FROM AUTHOR]

The multiactive-bridge (MAB) structure has obvious efficiency and cost advantages in multiport power electric transformer, but it brings the characteristics of strong current coupling of each transformer. To improve the dynamic response speed of MAB and reduce the coupling characteristics, a high-frequency current predictive control (CPC) method for MAB is proposed in this letter. The controller uses the enhanced single-phase shift modulation method to adjust the phase shift angle and duty cycle of four ports at the same time so that the high-frequency current can be adjusted in several switching cycles. In the proposed CPC method, the influence of control delay is analyzed and compensated, and the dc offset, which may occur in the dynamic process is analyzed and gives corresponding solutions. More importantly, the proposed CPC method can be extended to the power predictive control method to realize power decoupling of multiple ports of MAB. The parameter robustness of current and power predictive control is analyzed briefly in this letter. The proposed control method is validated on a hardware-in-loop simulation platform based on RT-lab. Experiment results show the superior dynamic performance and good robustness of the proposed method. [ABSTRACT FROM AUTHOR]

The wireless power supply solution has shown great advantages in rail transit applications, such as maglev trains and trams. However, research works on designing the magnetic coupler for wireless charging system in rail applications, which is a crucial problem, are not sufficient. Considering the high power and lightweight requirements, this article selects the coaxial M-shape magnetic coupler with LCL/S compensation for railway applications, which contains the transmitting rail and the receiving coil wound on an M-shape magnetic core. First, analysis was conducted on the requirements for inductance parameters of the magnetic coupler under the circuit constraints, including transmission power, input and output voltages, and component electrical stress, etc. Then, the influence of the geometric parameters of the coil structure and misalignment on its inductance parameters is analyzed. Based on these analysis results, the design method for the M-type magnetic coupler based on the lightweight principal is proposed. The geometric parameters are designed following a certain sequence to minimize the number of iterations and FEM simulation parameter sweeps, making the design procedure suitable for engineering practice. According to the proposed method, the magnetic coupler for a 360 kW wireless charging tram is designed and implemented. Through simulations and experiments, the magnetic coupler is verified to be feasible for the system with light weight. [ABSTRACT FROM AUTHOR]

Aiming for mutual isolation between ports, this article proposes a four-port high-frequency-bus-based power electronic transformer (HFB-PET), the core of which is the modular multiactive bridge (MMAB). In addition to port isolation, it also has the advantages of modularity, scalability, and reduced power conversion stages. First, the configuration of the proposed PET is introduced and compared with the existing solutions. Then, based on the mathematical model, a power coordinated control scheme is presented, including the power decoupling control for the cascaded H-bridge converter of the medium-voltage ac port to handle unbalanced grid voltages and active loads, the cell-power balance control for the medium-voltage dc port to achieve dc-link voltage equalization, and the power cross-coupling suppression control employed to improve the dynamic performance of the MMAB. On top of that, a hierarchical control framework with the global synchronous clock is constructed. Besides, a soft startup scheme considering the power balance between cells is introduced. Finally, the effectiveness of the proposed control scheme under the bidirectional power flow for the dc ports and the four-quadrant power flow for the ac ports is verified by experiments conducted on the laboratory scale-down prototype and the 10 kV/2 MVA industrial prototype. [ABSTRACT FROM AUTHOR]

The noninverting buck–boost (NIBB) converter is a step-up and step-down dc–dc converter suitable for applications with a wide input voltage range. However, this circuit will face the problem of operating mode switching when the input voltage is close to the output voltage. Considering this problem, the principles of the NIBB converter are analyzed in this article. The duty cycle combinations of an NIBB converter are analyzed, and an analysis method for the mode transition problem from a geometric perspective is proposed. Using the two-edge pulsewidth modulation method, a novel bumpless mode transition control method is proposed. A nonlinear feedforward controller with hysteresis is designed according to the state equation of the circuit. Moreover, the inductor current reference value is compensated when the mode is switched so that the mode transition problem of the NIBB circuit is effectively solved. In addition, a small-signal analysis of the proposed method is performed. The analysis shows that the proposed method has good stability and dynamic performance in various typical conditions. A 10-kW NIBB prototype is built in this article, and the corresponding experimental scenarios are designed. The experimental results show that compared with the results of unified PI control during the mode transition, the transient oscillation of the output voltage is smaller, and the duration of the transient process is shorter. [ABSTRACT FROM AUTHOR]

This letter proposes a deadbeat current controller for isolated bidirectional dual-active-bridge dc–dc converter. The controller uses an enhanced single phase shift modulation method by exploiting pulse width as an extra control variable besides phase shift ratio, the only control variable of the conventional single phase shift modulation. The current reference can be tracked within one switching cycle during the bidirectional power transmission and transition of the two directions. Deadtime effect is studied and the compensation method for the controller is proposed. Parameter robustness is analyzed by mathematical derivation and the online autotuning method for the inductance is presented. The proposed deadbeat current controller is simple and easy for implementation. Moreover, it shows superior dynamic performance, which is verified by experimental results during the transient processes of the converter. The effectiveness of the autotuning method is also validated by the prototype experiment. [ABSTRACT FROM AUTHOR]

An energy balance active disturbance rejection control (EB-ADRC) is proposed in this letter, which advances fast dynamics and enlarged stability region, suitable for the stability enhancement of converters cascaded with constant power loads. A unified converter energy control is employed to simplify the converter dynamic model to a first order, which is easy for dynamic design. Takagi-Sugeno (TS) fuzzy models are constructed and linear matrix inequalities (LMI) solving method is utilized to not only evaluate the upper limit of controller gain, but also make stability comparisons between EB-ADRC and classical proportional integral (PI) control. In the same main circuit inductor and capacitor values and approximate dynamic response precondition, the results illustrate that EB-ADRC enables a larger stability region. Experimental results are provided to validate the effectiveness and superiority of the proposed control scheme. [ABSTRACT FROM AUTHOR]

A comprehensive time-domain model of a CLLC class isolated bidirectional dc–dc converter (IBDC) is proposed in this article. Based on the circuit analysis and the solution of the state equations, analytical expressions of the state variables are provided. The model is a piecewise time-domain analytical model and can accurately describe the transformer currents and capacitor voltages under almost all basic types of control strategies, e.g., phase-shift control and frequency modulation control. With the model, the steady-state analysis of the IBDC can speed up evidently (up to 330 times faster compared to MATLAB/Simulink and more than 10 times compared to SIMPLIS and PLECS), which gives great support to parameter sweep and case comparison in the design procedure. By assigning specific parameters, the presented model can also be applied to the analysis of the LLC resonant IBDC or typical DAB IBDC since the LLC converter and DAB converter are similar to the CLLC converter in the circuit topology. The transformation of the model from CLLC to LLC/DAB is provided and several application examples are given. Finally, the simulation and experimental results are presented, verifying the effectiveness of the model. [ABSTRACT FROM AUTHOR]

A coordinated power balance control strategy independent of communication is proposed in this article, which includes autonomous modes transition control methods for photovoltaic converter, battery energy storage system and their cooperation with solid state transformer. The synthesized multiple power conversion systems contain an internal dc point-of-common coupling (PCC) and an external ac PCC, which form a dc microgrid and an ac microgrid, respectively. In grid-connected mode, the system is able to operate in power regulation pattern corresponding to grid-side response, or secondary dc bus voltage regulation pattern corresponding to local loads response, and switch between them on demand. Grid-connected and islanded/standalone modes can be transferred seamlessly, without the need of control structure reconfiguration through communication links. Moreover, control-related real-time communication is no longer necessary in this scheme, thus improving the reliability and reducing the total costs accordingly. Experimental results are provided to validate the effectiveness of the proposed control scheme. [ABSTRACT FROM AUTHOR]

For the bidirectional wireless power transfer (BWPT) technology, the phase synchronization between the transmitting and receiving converters is very essential and difficult to achieve by wireless communication between two sides because the delay and data transfer interval of wireless communication severely influence the control performance. This article proposes a novel control strategy for BWPT, which can achieve the phase synchronization and maximum efficiency point tracking independent of the real-time wireless communication. To solve the overshoot and oscillation problem incurred by the proposed control strategy and the nature of the system itself, the dynamics of a series–series compensated BWPT system is then analyzed and a small-signal model of this system is derived based on the generalized state space averaging and extended describing function methods. Using the small-signal model, a BWPT control system based on the proposed control strategy is designed and optimized. The validity of the proposed strategy and the performance of the control system are verified experimentally using a 3.3-kW prototype system. [ABSTRACT FROM AUTHOR]

DC microgrid, consisting of renewable energy sources, energy storage systems, and new types of loads like electric vehicles, has gained more and more attention nowadays. Energy storage systems in dc microgrid are required to regulate dc bus voltage as a backup power source at the islanding state while getting charged or discharged corresponding to energy management command at the grid-connected state. However, the dc bus voltage overshoot would occur with weak communication such as low-speed wireless communication and non-real-time network communication because of the large communication delay during the sudden state switching from grid-connected to islanding state. In this article, a novel coordinated control strategy for energy storage systems independent of real-time communication is proposed. With a novel sliding surface as the outer loop and an auto-tuning dead-beat current control as the inner loop, a smooth mode transition can be achieved even with a large communication delay, which means, real-time communication is unnecessary for the mode transitions. Therefore, the high reliance on the real-time communication is overcome with the system reliability enhanced as well. The proposed control strategy is verified by simulation and experimental results on a 450 V–3.5 kW prototype. [ABSTRACT FROM AUTHOR]