Fast and accurate optimization of the dynamic response is very important for an LCC resonant converter. The trajectory control is an effective way to achieve these goals. However, the model of the LCC resonant converter is generally too complex to get the target steady-state operation frequency and trajectory online and in real time with the common controllers. In this article, a fast solution can be obtained by adopting the proposed two-point solution method. A simplified steady-state trajectory model is also established, which is the solution object of the two-point solution method. When the necessary parameters are acquired, the target state trajectory and operation parameters, e.g., frequency, can be obtained quickly and accurately. Furthermore, the fast and accurate control strategy based on the simplified state trajectory and the two-point solution method is proposed to realize control of the LCC converter. The experiments are performed to verify the proposed control strategy. During the load transient, compared with the conventional proportional–integral control, the voltage variation and the response time are improved by more than 80%, respectively, and the two-point solution method can be finished within 2.3 μs by the controller. The fast response with a very small voltage variation is realized by the proposed control strategy.

To effectively assess retired batteries from electric vehicles, it is indispensable to estimate the battery state of charge (SoC), as many aging characteristic parameters are sensitive to it. This study aims to develop a rapid SoC estimation approach based on the simplified electrochemical model and genetic algorithms without restricting the initial equilibrium state of batteries. Specifically, the full-order pseudo-two-dimensional (P2D) model is simplified with Padé approximation and further improved by introducing the initial state parameters from the perspective of overpotentials. Next, a novel fast SoC estimation scheme is proposed using the constrained optimization method with a current pulse of 60 s instead of recursive estimation with a time-consuming relaxation procedure from 1 to 3 hours in conventional methods. The parameter sensitivity analysis is conducted to determine the key variables to be optimized. In addition, the genetic algorithm is improved by applying a repair operator to handle the constraints caused by battery operating conditions. Finally, three test cycles are designed to diversify the battery initial states for experimental verification. The results indicate that the mean absolute deviations among the entire SoC range are no more than 4% with different battery initial states, which are reduced by 3.5% compared to the adaptive extended Kalman filter algorithm with an equivalent circuit model.

Based on the First Harmonic Approximation (FHA) model of LCC resonant converter (CCM mode PFM control), this paper analyses and elaborates the mutual restriction relationship between LCC parameters. Subsequently, an intuitive design method is proposed to realize the gain capability of LCC resonant converter over wide load range with wide-range input and output. And a light load optimization using double inductors is presented to reduce the high switching frequency and reactive current under the light-load mode. Key parameters are given according to the specific requirements in this paper. Finally, the gain capability and the effect of the light load optimization are validated by the experimental results of a prototype with input 483-591V, output 40-150kV, output 1A(max) and output 80kW(max). The gain requirement can be satisfied remarkably, the frequency range of the system is optimized from 59.7-130.3kHz to 52.2-94.1kHz, and the resonant current is greatly reduced under the light-load mode.

This article introduces an optimal zero-sequence voltage injection strategy (OZVIS) for the three-phase dynamic voltage restorer (DVR), which can effectively reduce the output voltage magnitude of DVR in case of asymmetric sags in a three-phase, three-wire power system, so as to improve the compensation capacity of the device. The conventional compensation strategy improves the active power or reduces the voltage amplitude of the DVR through phase rotation, but the two functions are difficult to achieve together. In this article, the operation principle of OZVIS is first introduced. Then, the optimality and effectiveness of the strategy are theoretically demonstrated by means of a plane geometric modeling approach. In addition, the reduction extent using OZVIS in different voltage sag types is quantified, which is based on the minimum energy compensation strategy. Furthermore, a digital “plug-in” algorithm implementation for the proposed strategy is elaborated. Finally, the experimental results will be shown to verify the feasibility and effectiveness of OZVIS under an asymmetric situation. Moreover, the adaptability under a symmetric situation will also be illustrated.

The unified power quality conditioner (UPQC) is an effective solution for addressing power quality issues in modern power systems, with its ability to regulate both voltage and current. However, existing UPQC operational strategies lack sufficient adaptability and flexibility in managing load-side phase, especially when dealing with complex grid disturbances. This article proposes a unified framework for adaptive and flexible phase angle regulation, primarily based on two novel algorithms: the practical optimized-VA-loading operational strategy (POOS) and the universal flexible control method (UFCM). First, the proposed POOS method, utilizing phase angle control, enables online VA loading optimization within the UPQC's safe operating range according to real-time grid conditions. A comprehensive discussion of the method is presented, including the working principles, operational boundaries, and iterative computation process. Second, the proposed UFCM ensures smooth phase control of the load voltage throughout complex grid events. A dual-speed phase-locked loop is introduced to decouple the target and real-time phase, with parameter design guidelines and a discretization process provided. Furthermore, the unified framework is thoroughly explained, which balances the steady-state optimization requirements of the UPQC with the dynamic load-side power quality. Finally, experimental results validate the effectiveness of the unified framework under complex grid disturbance scenarios.