Search

A unified power quality controller based on a magnetic flux control tunable reactor is proposed. The magnetic flux control tunable reactor is composed of a voltage source inverter (VSI) and a transformer with an air gap. The power quality controller is divided into two parts: the harmonic open circuit part is connected in series in the system, and the harmonic short circuit part is connected in parallel in the system. Among them, the series part detects the fundamental wave component of the primary side current of the transformer, generates a reference signal, and controls the VSI to generate a fundamental wave controllable current, after the filter is applied to the secondary side of the transformer, the primary side of the transformer will show variable impedance and open circuit to the fundamental wave and harmonic current respectively; The parallel part detects the fundamental wave component of the primary side current, generates a reference signal, and controls the VSI to generate a fundamental controllable voltage, After the filter is applied to the secondary side of the transformer, the primary side of the transformer presents controllable impedance and short circuit to the fundamental wave and harmonic current respectively.By building a MATLAB simulation model, the effectiveness of the proposed unified power quality controller is verified.

With the emergence of digital grid concept, the current metering system using PTP (Precise Time Protocol) clock synchronization technology cannot provide a unified device clock system across entire network, which affects two-way real-time control of new energy. And it is difficult to meet the clock for new business transactions synchronization accuracy requirements. Under the original metering clock system, a multi-source clock weighted fusion technology was proposed that used 5G communication modules as reference clocks, and used Kalman filtering to complete step-by-step clock correction at all levels of network nodes to achieve coordinated correction of different external reference clocks. The highest clock synchronization accuracy ensure the consistency of real-time data collection clock. Based on field test data collected by the Shenzhen Power Supply Bureau, the results showed that the electricity bill settlement after clock synchronization optimization processing is closer to field settlement.

The paper describes a calibration for a differential phase measurement system frequency from 5 Hz to 1 MHz based on two dual-channel high-speed digitizers controlled by National Instrument multiple instruments synchronization technology. The measurements compared single-end sampling mode and differential mode, and extra phase calibration experimental for differential phase measurement system. Phase measurement jitters are observed on differential mode. The results indicate the differential phase measurement is accuracy enough for calibration.

A wideband power analyzer is a synthetic instrument measuring electrical parameters of power supply and applied widely in all fields of industry. Because it has characteristics of strong function, many parameters, wide wideband, large measurement range, large span of accuracy grade and so on, the daily calibration of the instrument is very complex, and all the calibration items cannot be finished by using one or more standard equipments. This article introduces the calibration method for routine calibration items of the wideband power analyzer in detail by using a standard source measurement method and a standard system measurement method.

Short-term wind speed forecasting is important for the accuracy of wind power prediction. Based on convenience to establish the Time series prediction model and high accuracy of Kalman filtering algorithm, this paper proposes a hybrid algorithm to forecast wind speed combining Time series analysis and Kalman filter algorithm. First using Time series analysis theory, set up the regression forecasting model of wind speed sequence and then establish the state equation and measurement equation of Kalman filter. Because the input noise covariance and measurement noise covariance of the Kalman filtering method take the fixed value, thus we use the Adaptive Kalman filtering method, to realize hybrid forecast of the wind speed sequence. Simulation results showed that the proposed hybrid algorithm can effectively improve the predictive accuracy of wind speed, and can also solve the time delay of Time series method to predict the wind speed and lack of adaptability of Kalman filtering method exists.

An ac resistive divider used in calibrating of wideband frequency power analyzer is developed in the paper. It also describes the design of the divider, and techniques to improve the performance of the divider, and reduce the ratio error and the phase shift. Testing results of the divider show that the long-term stability of ratio error is less than 10−5, ratio error is less than10−4, phase shift is less than 3mrad within 10 kHz.

Selective Catalytic Reduction (SCR) is a method of reducing oxides of nitrogen (NOx) emissions from diesel engines by catalytic reaction. Based on AMESim software, 1D and 2D SCR system models for diesel engines are established and simulated. The results show that both two models are available for the performance study of SCR system, and the 2D model matches the experiment results better, which is adopted in the study of NOx conversion ratio and NH3 leakage at different exhaust temperature. NOx conversion ratio continuously increases with the exhaust temperature, and the increase is slow at first, then rapid, and stable at last. Besides, the rising of the exhaust temperature will lead to decease of the NH3 leakage.

The fuel economy and pollutant emissions characters of diesel taxies in Shanghai were analyzed. In particular, the fuel consumption and fuel cost per 100 kilometers, turnover, traveled distance, service kilometers, empty-loaded rate, and CO, NO X , HC+NO X , PM emissions characteristics of diesel taxies were carried out. The analysis result shown that compared with gasoline taxies, the fuel consumption and fuel cost per 100 kilometers of diesel taxies were reduced by 29% and 26% respectively. Diesel taxies will get more traveled distance, further service kilometers, and added turnover, whereas lower empty-loaded rate and less fuel cost per 100 kilometers. Among the total 120,000 kilometers test distance, the CO emission of diesel taxies was lower than the limited value of China national emission standard IV, the NOX and HC+NOX emission is under the limited value of China national emission standard III, whereas, the PM emission was under the limited value of China national emission standard II. All of CO, NO X , HC+NO X , and PM emissions of diesel taxies were reduced obviously when fuel by Shanghai IV diesel after 1st November, 2009.

Experimental studies on global warming potential (GWP), photochemical ozone creation potential (POCP), acid potential (AP), health toxic potential (HTP), and air quality potential (AQP) of an common rail diesel engine fueled with wasted oil based biodiesel blends were carried out. The results shown that when the engine fueled with wasted oil based biodiesel blends, its POCP and AQP are lower than fossil diesel at all test speed and load cases, the AP is lower than that of fossil diesel at all test load cases on engine rated speed. Moreover, the GWP, AP, and HTP at engine rated speed are lower than fossil diesel when the test load was under 75%. And, the GWP, AP, and HTP at engine speed characteristic under full load are lower either than fossil diesel when the engine speed was higher than 1600 rpm.

In this study, LSD (Shanghai IV low sulfur diesel), HSD (China II diesel), Emulsified LSD (10% of water with 90% Shanghai IV diesel by volume) and Emulsified HSD (10% of water with 90% China II diesel by volume) were tested in a high-pressure common rail diesel engine to investigate the power performance, fuel economy and emission characteristics of the engine. The study shows that there is small impact on power performance of the diesel engine fueled with four tested fuels. The China III diesel engine fueled with LSD has better power performance, fuel economy and lower PM emissions than HSD. When the China III diesel engine was fueled with four tested fuels, CO, HC, NO X and PM emissions could meet China III emission standards, but could not fully meet China IV emission standards. It is more efficient to reduce CO, HC, NO X and PM emissions when engine is fueled with emulsified diesel than neat diesel. Compared Emulsified HSD with HSD, the decreases were, 3.92%, 7.14%, 2.22% and 21.02% respectively for PM, CO, HC and NO X emissions of the tested engine, while compared Emulsified LSD with LSD, the corresponding decreases were 17.31%, 10.71%, 7.22% and 15.82% respectively.

SCR technology is one of effective methods to reduce NOx emissions from diesel engines. In this paper, a SCR system model is established based on AMESim software and a mathematical model of SCR control system is established in the Matlab/Simulink environment, and a complete system is formed by setting communication modules between the two softwares. The SCR closed-loop control strategy is studied, and the PI control strategy is introduced to build a closed-loop SCR control system model and the simulation is performed. AdBlue dosing, NOx conversion ratio and NH 3 leakage at the different exhaust temperature are studied with different control parameters.

The emissions characteristics of a diesel car fueled by biodiesel volume ratio of 10% (called BD10), which is the mixture of conventional diesel and waste oil based biodiesel, was carried out. And the emission characteristics of HC, CO, NO X and CO 2 in different driving mode and different driving cycle in accordance with the “I” type test cycle of Chinese vehicle emission standard GB18352.3-2005 was analyzed. The results shown that compared with the idling, constant speed, and deceleration driving modes, the accelerated driving mode's HC, CO, NO X emissions of BD10 fueled diesel car is relatively high. The HC and CO emissions of the first urban operation cycle, and the CO 2 and NO X emissions of suburban operation cycle are higher than others operation cycles of the “I” type test cycle of GB18352.3-2005. Compared with conventional diesel, the HC, CO, NO X , CO 2 emissions of BD10 fueled diesel car are reduced by 6%, 1%, 10% and 2% respectively.