LOW VOLTAGE APPARATUS

Research Status and Trends of Key Technologies for Large Scale Wind/PV Hybrid Hydrogen Production and Storage System

XING Xiaowen, MU Shujun, FAN Yujian, SUN Xun, ZHOU Yipeng

2024, 0(4): 1-12. doi:10.16628/j.cnki.2095-8188.2024.04.001

Asbtract ( 136 )

HTML ( 5)

PDF (1406KB) ( 67 )

Figures and Tables | References | Related Articles | Metrics

The development of large-scale wind/PV hybrid hydrogen production and storage systems is of great and far-reaching significance for promoting China's energy strategic transformation, achieving energy conservation and emission reduction and developing high-quality new energy. However, the current research review on wind/PV hydrogen production is mainly focused on hydrogen production technology itself. There is still a lack of systematic review from multiple perspectives, including core equipment, operational control, safety protection and so on. Firstly,the development status of large-scale wind/PV hybrid hydrogen production technology at home and abroad was summarized. Then, from the perspective of key technological development, including the structure, core equipment, operation control, protection methods and safety monitoring of the wind/PV hybrid hydrogen production and storage system were analyzed and summarized. Finally, the future development trends and prospects of large-scale wind/PV hybrid hydrogen production and storage systems were predicted.

Economic Dispatch of Regional Integrated Energy System Based on Collaborative Optimization of Multi-Source Heat Pumps

JIANG Tao, ZHOU Huijuan, ZHANG Qimeng, ZHOU Weiran, XU Zhen

2024, 0(4): 13-21. doi:10.16628/j.cnki.2095-8188.2024.04.002

Asbtract ( 121 )

HTML ( 2)

PDF (2024KB) ( 41 )

Figures and Tables | References | Related Articles | Metrics

To explore the synergistic optimization effect of electric heat pump and gas heat pump, a regional comprehensive energy system(RIES) economic dispatch method for the coordinated operation of multi-source heat pump systems is proposed. Firstly, a comparative exposition of the technical characteristics of electric heat pump and gas heat pump is conducted. Based on the energy hub, various energy flows of the system under the multi energy complementary operating conditions of electric heat pump and gas heat pump are analyzed. Secondly, based on the price advantages of electricity and gas energy, electric heat pump is used for electric cold energy coupling during peak electricity periods, and gas cooling is replaced by gas heat pump during peak electricity prices to improve the peak valley characteristics and operating costs of the system's electricity load. Finally, a collaborative optimization dispatch model for electric heat pump and gas heat pump is established with the optimal system cost,and solved by using CPLEX software. The calculation example shows that the coordinated operation of electric heat pump and gas heat pump can fully leverage the advantages to reduce the operating cost of the system and optimize the interaction power fluctuation of the interconnection line. Moreover, the proposed method has good environmental benefits.

Research on an Improved VOT Control Strategy of Boost PFC Circuit

GUAN Zhen, LIN Weiming

2024, 0(4): 22-29. doi:10.16628/j.cnki.2095-8188.2024.04.003

Asbtract ( 106 )

HTML ( 1)

PDF (3229KB) ( 24 )

Figures and Tables | References | Related Articles | Metrics

In order to solve the problem of poor performance of PF and THD caused by negative resonant current and input filter capacitor under constant on time(COT) control strategy, an improved variable on time (VOT) control strategy is proposed. The operating principle and operating process of making the average inductance current approach to the sine wave in the power frequency cycle by adaptively increasing the conduction time to offset the negative resonant current and reducing the phase difference are analyzed in detail. The main circuit is combined for key parameter design, a prototype with rated power of 320 W is developed. The comparative experiment of COT control strategy and improved VOT control strategy is carried out. The computer simulation and experimental results show that the PF of the improved VOT control strategy is increased from 0.726 to 0.801, and the THD is reduced from 27.92% to 18.4% when the 265 V high voltage input 20% load is working. At 40%~100% load, the requirements of PF>0.9 and THD<15% are met, which verifies the effectiveness of the proposed control strategy.

Research on Arc Root Stagnation of Contact Edge Phenomenon and Influencing Factors in DC Interruption

BAO Yuliang, LI Jing, DUAN Wei, PENG Shidong, LIU Shuxin

2024, 0(4): 30-37. doi:10.16628/j.cnki.2095-8188.2024.04.004

Asbtract ( 129 )

HTML ( 6)

PDF (1929KB) ( 83 )

Figures and Tables | References | Related Articles | Metrics

The evolution of arc root has an important effect on the switching efficiency of DC air circuit breaker. Based on the magneto-hydro-dynamics (MHD) model, the essential cause for the arc root stagnation of the contact edge was simulated and analyzed. The effects of the external magnetic field and breaking speed for the arc root stagnation of the contact edge were obtained. The results show that the transfer of the arc root from the contact to the arc runner is completed through breakdown. The arc root stagnation of the contact edge is formed because the arc runner has not reached the breakdown condition before the arc root transfers. With the increase of magnetic field intensity, the arc root stagnation time of the contact edge decreases, and the ability to shorten the arc root stagnation of the contact edge becomes weak, eventually tends to be saturated. At the initial stage of arcing, increasing the contacts breaking speed within a certain rang is conducive to reduce the arc root stagnation time. However, excessively increasing the contacts breaking speed has a weak effect on reducing the arc root stagnation time under the influence of Lorentz force and airflow field.

Design of Type I Three-Level Energy Storage Converter

LI Jinwei, LI Tang, MAO Xingkui, ZHANG Zhe

2024, 0(4): 38-44. doi:10.16628/j.cnki.2095-8188.2024.04.005

Asbtract ( 122 )

HTML ( 1)

PDF (2836KB) ( 34 )

Figures and Tables | References | Related Articles | Metrics

With the rapid development of new energy generation, the issue of intermittency and uncertainty in the output power of new energy generation is becoming increasingly prominent. In order to enhance the grid's ability to absorb new energy, a type I three level energy storage converter has been designed. On the basis of in-depth analysis of its working principle, a mathematical model was constructed and a constant current charging and discharging control strategy was provided. In response to the problem of midpoint potential imbalance in the three level energy storage converter, a space vector pulse width modulation (SVPWM) algorithm with variable distribution factor was proposed to achieve rapid response to midpoint potential fluctuations. The experimental results of prototype show that under constant current charging and discharging control strategy, the designed prototype has good steady-state and transient performance under grid connection conditions. The used SVPWM algorithm with variable allocation factor can quickly suppress midpoint potential fluctuations and has a significant inhibitory effect.

Magnetic Modulation Current Sensor Based on Single Magnetic Ring and Three Windings

GUO Zhenzhen, CHEN Wei, CHEN Chong, ZHOU Anyue, LIN Zhenquan

2024, 0(4): 45-52. doi:10.16628/j.cnki.2095-8188.2024.04.006

Asbtract ( 100 )

HTML ( 3)

PDF (2233KB) ( 34 )

Figures and Tables | References | Related Articles | Metrics

The existing high-precision closed-loop magnetic modulation current sensors mostly use double or even triple magnetic ring structures, which usually have disadvantages such as large volume, complex modulation and demodulation circuits, and inconsistent magnetic ring characteristics. A closed-loop magnetic modulation current sensor based on a single magnetic ring and three winding structure is proposed. Based on the average excitation current method, the further research is conducted to simplify the understanding of the modulation circuit. By adding an induction winding and corresponding computing circuit, the signal noise caused by transformer effect is eliminated. And using genetic algorithm to optimize the values of some sensor parameters, the sensor performance is improved. The proposed design has a simple structure, small size, large range, high accuracy, and meets the measurement needs of large DC currents.

Effect of Chamfer and Center Magnetic Induction on Electrical Life of DC Contactors

CAI Ming, MA Wei, WANG Jianxiong, LI Chao

2024, 0(4): 53-56. doi:10.16628/j.cnki.2095-8188.2024.04.007

Asbtract ( 113 )

HTML ( 3)

PDF (1096KB) ( 53 )

Figures and Tables | References | Related Articles | Metrics

When the sealed DC contactor breaks the load, the splashing of contacts in the arc extinguishing chamber is inevitable. The influence of contact chamfering and center magnetic induction on electrical life is verified by grouping test. The results show that with the increasing of contact center magnetic induction, the total number of breaking load will be increased, but the spattering will also be increased, which will lead to the decrease of dielectric voltage resistance and insulation resistance. The spattering will be decreased with the increasing of contact chamfer, the dielectric voltage and insulation resistance will be increased, but the total number of breaking load will be reduced.

Prediction of Ultra-Short-Term Wind Speed Based on VMD-FE-SSA-SVR Model

WANG shengyan, WANG juanjuan

2024, 0(4): 57-64. doi:10.16628/j.cnki.2095-8188.2024.04.008

Asbtract ( 102 )

HTML ( 4)

PDF (1749KB) ( 21 )

Figures and Tables | References | Related Articles | Metrics

In order to effectively reduce the difficulty of wind speed prediction caused by nonlinear and disordered wind speed and improve the prediction accuracy, a combined forecasting model combining variational mode decomposition (VMD), fuzzy entropy (FE), sparrow search algorithm (SSA) and support vector regression (SVR) is proposed to predict ultra-short-term wind speed. Firstly, the wind speed data is decomposed into several modal components by VMD technology, and then each component is screened by FE, and the components with similar FE values are superimposed to form several new series. Then the new series are trained and predicted by the SVR model optimized by SSA. Finally, the prediction results of the new series are superimposed to form the final prediction results. Through the verification and comparison of different models, the prediction effect of the VMD-FE-SSA-SVR model is better, which shows that the proposed model has better prediction accuracy and stability, and can effectively predict ultra-short-term wind speed.

Wind Turbine Operation Status Monitoring Based on SSA-GPR Model

ZHANG Jie, REN Kang, MA Tian, WANG Weilu, XING Zuoxia, HAN Guangming

2024, 0(4): 65-73. doi:10.16628/j.cnki.2095-8188.2024.04.009

Asbtract ( 97 )

HTML ( 3)

PDF (2009KB) ( 28 )

Figures and Tables | References | Related Articles | Metrics

In order to improve the power generation efficiency and economic benefits of wind turbines, the online monitoring of the operating status of wind turbines is particularly important. A new method for monitoring the status of wind turbines based on sparrow search algorithm optimized Gaussian process(SSA-GPR) model is proposed. Firstly, the data collected from data collection and monitoring is preprocessed and analyzed. The correlation analysis is used to select the input of the model. A normal regression model using the parameters of the unit under normal operating conditions is established to calculate the reconstruction error in real-time. The unit status is determined by monitoring whether the predicted power residual exceeds the dynamic fault threshold in real-time. Through examples, it is shown that the proposed SSA-GPR model smaller prediction error and can achieve abnormal operation status warning of the unit 120 minutes in advance.

DC Impedance Modeling and Characteristic Analysis of Bidirectional AC/DC Converter for V2G System

ZHANG Ying, FU Rui, TANG Linquan, RONG Gaosheng, SHEN Yabo

2024, 0(4): 74-81. doi:10.16628/j.cnki.2095-8188.2024.04.010

Asbtract ( 108 )

HTML ( 3)

PDF (2924KB) ( 31 )

Figures and Tables | References | Related Articles | Metrics

The control of bidirectional AC/DC converters and the DC output impedance are crucial for the grid connected operation and stability analysis of electric vehicle charging stations. First, the virtual synchronous motor(VSM) control strategy with DC droop link is proposed, and the upper-level power command is used to realize the non-differential regulation for DC voltage of the bidirectional AC/DC converter. Then, a small signal model of the VSM power loop is established to analyze the interaction and influence between active power transmission, active power command and DC voltage. Furthermore, the DC output impedance model of the bidirectional AC/DC converter controlled by the DC droop VSM is established, and the influence of key parameters such as damping and inertia coefficient, DC side capacitance, transmission power, and DC droop coefficient on the DC output impedance is further analyzed in detail. Finally, the simulation result and impedance measurement verify the effectiveness and correctness of DC droop VSM control strategy and the proposed impedance model.

Exploration and Practice of Comprehensive Uninterrupted Operation Technology for 10 kV Distribution Network Based on Power Supply Reliability

WANG Qingze, AI Maomin, AN Junwei, ZHANG Shuo, WANG Jia, ZHANG Jiaming

2024, 0(4): 82-89. doi:10.16628/j.cnki.2095-8188.2024.04.011

Asbtract ( 96 )

HTML ( 1)

PDF (2976KB) ( 37 )

Figures and Tables | References | Related Articles | Metrics

Based on the 10 kV distribution network non-stop operation technology system, the application principles and typical scenarios of conventional live working technologies such as insulated pole and insulated glove operation method, as well as comprehensive uninterrupted power operation technologies such as bypass operation method and "micrgrid"power generation operation method are elaborated. The application of comprehensive uninterrupted power operation method is discussed in response to the problem of long-term and large-scale power outage maintenance. Finally, taking the replacement of the ring main unit and the comprehensive maintenance of the line as example, the comprehensive implementation plan and operation process for the integration of shutdown and electrification are developed to verify the feasibility and effectiveness of the comprehensive uninterrupted power operation method, which can provide strong support for continuously improving the reliability of power supply in the distribution network.

Table of Content