This paper proposes the circuit structure, topological family and energy management control strategy (EMCS) of a Buck type multi-input distributed generation system (DGS) with parallel-timesharing ...power supply. Also, the power supply modes (PSMs) and their smooth transition, as well as the control loops and multiple duty cycles expression are studied. The circuit structure is composed of a Buck type single-stage multi-input inverter and a single-stage isolated battery charging/discharging converter, with their outputs parallel-connected on the AC side. The topological family includes full-bridge etc. 3 types of circuit. By comparing the load power and the total generated multi-input sources power, the proposed EMCS achieves real-time control of charging/discharging converter's power flow and the system's smooth transition among different PSMs. The proposed "variable inductances equivalent method" regards the output filter inductor as the parallel connection of two virtual inductances, based on which the small signal model of multi-input inverter is established and the corresponding control loops are designed. Experimental results of a 3kVA laboratory prototype have shown that the proposed circuit topology has a good performance of high conversion efficiency, low distortion of output voltage, and galvanic isolation among load, multi-input sources and battery, etc.
Affected by dead time, the asymmetric action of power switches and the offset sampling of current sensor, there is a certain DC component in output waveforms of photovoltaic inverter, which leads to ...a magnetic core saturation of the output line-frequency (LF) transformer. This paper proposes a magnetic saturation suppression scheme for the output LF transformer, and deeply analyzes its suppression principle and the regulator design in detail. The proposed suppression scheme detects the primary current of the output LF transformer as the feedback signal of the core's working state and adds a DC bias correction loop outside the output voltage loop (the grid current loop) to correct the DC bias for each LF output cycle, thus avoiding the magnetic saturation of the output LF transformer. In addition, this scheme also eliminates the influence of the current sensor's offset sampling. Experimental results verify the correctness and feasibility of the theoretical analysis.
Photovoltaic, wind and other single new energy power generation usually has the disadvantages of unstable and discontinuous power supply, changing with climatic conditions and day and night, so it is ...necessary to use multiple new energy combined power generation systems. This paper proposes a novel voltage-type dual input sources independent generation system(IGS) with single-stage power conversion, analyzes the circuit topology , energy management control strategy(EMCS) and steady-state principle characteristics of this type of generation system. The IGS is composed of a parallel-timesharing voltage-type dual input inverter with single-stage power conversion and a battery single-stage bidirectional charge-discharge converter, with their outputs parallel-connected on the AC side. Its EMCS controls the power flow of the charge-discharge converter in real time and realizes the smooth and seamless switching of the three power supply modes by comparing the load power and the total power of multiple input sources. The designed 3kVA IGS prototype has excellent performances such as high conversion efficiency, high output waveform quality, and electrical isolation between multiple input sources-battery-loads.
Large grid impedance is the main characteristic of weak grid, and its accurate detection can improve the inverter control performance. However, traditional impedance detection method based on current ...harmonic injection usually causes a large increase in harmonics, which weakens the power quality. In order to solve this problem, an improved multiple harmonic injection method based on QPR (Quasi Proportional Resonance) parameter-adaptive control strategy is proposed in this paper. By analyzing the impedance detection results and the power quality of the inverter output, the impedance detection results are sent to the adaptive control system, which is used to correct the quality of the grid-connected current waveform after calculating each parameter of the QPR controller. The final simulation results show that the proposed improved control strategy can improve the inverter output waveform quality and enhance the anti-interference capability of the weak grid without changing the impedance detection accuracy of the wind power grid-connected inverter under weak power conditions.
In this paper, the circuit topology of single-stage isolated charging/discharging DC-AC converter with second harmonic current suppression is proposed. Based on which an analogous-rectifying unipolar ...phase-shifted control strategy with constant charging/discharging current is also proposed, which rectifies the Sinusoidal Pulse Width and Position Modulation(SPWPM) wave of high-frequency(HF) transformer to positive/negative half line cycle Sinusoidal Pulse Width Modulation(SPWM) wave through the bi-directional rectification circuit, and realizes constant charging/discharging current of the battery at the same time. Aiming to suppress the input second harmonic current, an L r -C r parallel-resonant circuit which is connected in series between the battery and input filter capacitor is introduced. Experimental results of the designed prototype show that the proposed converter has excellent performances such as HF galvanic isolation, single-stage bi-directional charge/discharge, high conversion efficiency and small ripple of input current, which provides a new methodology for battery charge/discharge in distributed generation systems.
In view of the instability and discontinuity caused by the uncertainty of new energy power generation sources, a low frequency isolated single-stage two-input grid-connected inverter for combined ...wind and photovoltaic (PV) power supply is proposed. In this paper, deep research is done on the control topology and circuit topology. The small signal mathematical model is established by using the state space averaging method, and the design method of the current regulator under the coupling of control variables is given. By decomposing the filtering inductor current, the quality of the grid-connected current waveform and the maximum power output of each input source are ensured by the control maximum power output SPWM strategy. Simulation results verify the effectiveness of circuit topology and its control strategy.
The paper develops an adaptive particle swarm optimization(PSO) based on its simplification. With the hope to prompt its global optimization performance, the improved menthod introduces a PD ...controller into the architecture of the standard PSO(SPSO-PD). The PD controller can control the particle dynamics, and prompt the particles to respond to the change of their exemplars correctly and rapidly, further to surpass the limit of their exemplars with more chances, which greatly contributes to a successful global search. The proposed SPSO-PD was applied to some well-known benchmarks and compared with the standard PSO. The relative experimental results show SPSO-PD performs better than SPSO on the complex optimization functions.
The stochastic dependent-chance programming belongs to a class of stochastic programming problems, which has wide application backgrounds, in order to search an algorithm which can more effectively ...solve this problem, in the paper, stochastic simulation is used to produce training samples for BP neural networks, and a hybrid intelligent algorithm for stochastic dependent-chance programming combined PSO algorithm with BP neural networks for approximation of the chance function is presented. Finally, the simulation results of two examples are given to show the correctness and effectiveness of the algorithm.
The objective of positive education is not only to improve students' well-being but also their academic performance. As an important concept in positive education, growth mindset refers to core ...assumptions about the malleability of a person's intellectual abilities. The present study investigates the relation of growth mindsets to psychological well-being and school engagement. The study also explores the mediating function of resilience in this relation. We recruited a total of 1260 (658 males and 602 females) Chinese students from five diversified primary and middle schools. Results from the structural equation model show that the development of high levels of growth mindsets in students predicts higher psychological well-being and school engagement through the enhancement of resilience. The current study contributes to our understanding of the potential mechanisms by which positive education (e.g., altering the mindset of students) can impact psychological well-being and school engagement.
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