Three-level neutral point clamped(NPC)inverters have been widely applied in the high voltage and high power drive fields.The capacitance voltage balancing algorithm is a hot topic that many specialists and scholars ha...Three-level neutral point clamped(NPC)inverters have been widely applied in the high voltage and high power drive fields.The capacitance voltage balancing algorithm is a hot topic that many specialists and scholars have been working on.V arious capacitance voltage balancing strategies have been studied,in which the redundant short vectors are not fully utilized.In order to increase the capacitance voltage control effect of the short vectors,a new algorithm is proposed.展开更多
Capacitive voltage transformers (CVTs) are essential in high-voltage systems. An accurate error assessment is crucial for precise energy metering. However, tracking real-time quantitative changes in capacitive voltage...Capacitive voltage transformers (CVTs) are essential in high-voltage systems. An accurate error assessment is crucial for precise energy metering. However, tracking real-time quantitative changes in capacitive voltage transformer errors, particularly minor variations in multi-channel setups, remains challenging. This paper proposes a method for online error tracking of multi-channel capacitive voltage transformers using a Co-Prediction Matrix. The approach leverages the strong correlation between in-phase channels, particularly the invariance of the signal proportions among them. By establishing a co-prediction matrix based on these proportional relationships, The influence of voltage changes on the primary measurements is mitigated. Analyzing the relationships between the co-prediction matrices over time allows for inferring true measurement errors. Experimental validation with real-world data confirms the effectiveness of the method, demonstrating its capability to continuously track capacitive voltage transformer measurement errors online with precision over extended durations.展开更多
Based on current voltage（I-Vg） and capacitance voltage（C-Vg） measurements,a reliable procedure is proposed to determine the effective surface potential Vd（Vg） in Schottky diodes.In the framework of thermionic em...Based on current voltage（I-Vg） and capacitance voltage（C-Vg） measurements,a reliable procedure is proposed to determine the effective surface potential Vd（Vg） in Schottky diodes.In the framework of thermionic emission,our analysis includes both the effect of the series resistance and the ideality factor,even voltage dependent. This technique is applied to n-type indium phosphide（n-InP） Schottky diodes with and without an interfacial layer and allows us to provide an interpretation of the observed peak on the C-Vg measurements.The study clearly shows that the depletion width and the flat band barrier height deduced from C-Vg,which are important parameters directly related to the surface potential in the semiconductor,should be estimated within our approach to obtain more reliable information.展开更多
A high performance current and voltage measurement system has been developed in power system. The system is composed of two parts: one current measurement element and one voltage measurement element. A Rogowski coil ...A high performance current and voltage measurement system has been developed in power system. The system is composed of two parts: one current measurement element and one voltage measurement element. A Rogowski coil and a capacitive voltage divider are used respectively for the line current and voltage measurements. Active electronic components are used to modulate signal, and power supply for these components is drawn from power line via an auxiliary current transformer. Measurement signal is transmitted by optical fibers, which is resistant to electromagnetic induction and noise. With careful design and the use of digital signal processing technology, the whole system can meet 0.5% accuracy for metering and provides large dynamic range coupled with good accuracy for protective relaying use.展开更多
Voltage measuring equipment in power grids often requires capacitive voltage dividers to realize conversion of high voltage electrical quantities to low voltage signal quantities.The new floating-ground capacitive vol...Voltage measuring equipment in power grids often requires capacitive voltage dividers to realize conversion of high voltage electrical quantities to low voltage signal quantities.The new floating-ground capacitive voltage divider(FG-CVD)can eliminate original lumped capacitors and its supporting insulation structures by adopting precisely designed parasitic capacitance as a high voltage arm capacitor,which can greatly save cost and volume.However,the utilization of parasitic capacitance not only makes FG-CVD sensitive to external conductor interference,but also causes transient waveform distortion,especially when the connecting lead between the FG-CVD and high-voltage conductor is lengthy.On the basis of transfer characteristic analysis,this paper proposes a complete parameter design method for FG-CVD to improve stability of its transfer ratio under interference of the external conductor.Moreover,by establishing a wideband equivalent model with lead inductance,the transient waveform distortion problem of FG-CVD is well explained,and a resistance compensation scheme is also proposed to reduce ratio error.Finally,a 500:1 FG-CVD prototype with a measurement bandwidth of 2MHz is developed.Experimental results show the prototype has high accuracy in both power frequency and lightning pulse voltage measurement,and ratio error decreases from 20.33%to less than 1.3%.展开更多
We investigate the effects of （N,N’-diphenyl）-N,N’-bis（1-naphthyl）-1,1’-biphenyl-4,4’-diamine （NPB） buffer layers on charge collection in inverted ZnO/MEH-PPV hybrid devices. The insertion of a 3-nm NPB thin...We investigate the effects of （N,N’-diphenyl）-N,N’-bis（1-naphthyl）-1,1’-biphenyl-4,4’-diamine （NPB） buffer layers on charge collection in inverted ZnO/MEH-PPV hybrid devices. The insertion of a 3-nm NPB thin layer enhances the efficiency of charge collection by improving charge transport and reducing the interface energy barrier, resulting in better device performances. S-shaped light J–V curve appears when the thickness of the NPB layer reaches 25 nm, which is induced by the inefficient charge extraction from MEH-PPV to Ag. Capacitance–voltage measurements are performed to further investigate the influence of the NPB layer on charge collection from both simulations and experiments.展开更多
With the increase of the operating voltage and enlargement of the size of the capacitor voltage transformer(CVT),the additional measurement error caused by stray capacitance coupling and leakage current along the poll...With the increase of the operating voltage and enlargement of the size of the capacitor voltage transformer(CVT),the additional measurement error caused by stray capacitance coupling and leakage current along the polluted surface of the CVT becomes noticeable.The equipotential shielding CVT(EPSCVT)was proposed and designed by the authors to mitigate these effects.An improved conceptual design option of the EPS-CVT is presented in this paper with special references to this study to improve the shielding effect without the increase of shielding capacitance.A proposed method of non-uniform capacitance configuration can improve the shielding effect significantly without an increase of the external shielding capacitance.Based on this achievement,the potential difference and the capacitive current exchange between the internal measuring system and external shielding systems are significantly reduced.In the evaluation of the shielding effect for the influence of stray capacitance,compared with a conventional CVT with equal capacitance,EPS-CVT can reduce the measurement error by two orders of magnitude.In addition,the measurement error caused by the leakage current can also be greatly reduced,especially for the reduction of the phase angle error.Based on the improved design method,a design scheme for an engineering application is proposed which can achieve effective shielding while ensuring as good a technical performance as the existing CVT.展开更多
文摘Three-level neutral point clamped(NPC)inverters have been widely applied in the high voltage and high power drive fields.The capacitance voltage balancing algorithm is a hot topic that many specialists and scholars have been working on.V arious capacitance voltage balancing strategies have been studied,in which the redundant short vectors are not fully utilized.In order to increase the capacitance voltage control effect of the short vectors,a new algorithm is proposed.
文摘Capacitive voltage transformers (CVTs) are essential in high-voltage systems. An accurate error assessment is crucial for precise energy metering. However, tracking real-time quantitative changes in capacitive voltage transformer errors, particularly minor variations in multi-channel setups, remains challenging. This paper proposes a method for online error tracking of multi-channel capacitive voltage transformers using a Co-Prediction Matrix. The approach leverages the strong correlation between in-phase channels, particularly the invariance of the signal proportions among them. By establishing a co-prediction matrix based on these proportional relationships, The influence of voltage changes on the primary measurements is mitigated. Analyzing the relationships between the co-prediction matrices over time allows for inferring true measurement errors. Experimental validation with real-world data confirms the effectiveness of the method, demonstrating its capability to continuously track capacitive voltage transformer measurement errors online with precision over extended durations.
文摘Based on current voltage（I-Vg） and capacitance voltage（C-Vg） measurements,a reliable procedure is proposed to determine the effective surface potential Vd（Vg） in Schottky diodes.In the framework of thermionic emission,our analysis includes both the effect of the series resistance and the ideality factor,even voltage dependent. This technique is applied to n-type indium phosphide（n-InP） Schottky diodes with and without an interfacial layer and allows us to provide an interpretation of the observed peak on the C-Vg measurements.The study clearly shows that the depletion width and the flat band barrier height deduced from C-Vg,which are important parameters directly related to the surface potential in the semiconductor,should be estimated within our approach to obtain more reliable information.
文摘A high performance current and voltage measurement system has been developed in power system. The system is composed of two parts: one current measurement element and one voltage measurement element. A Rogowski coil and a capacitive voltage divider are used respectively for the line current and voltage measurements. Active electronic components are used to modulate signal, and power supply for these components is drawn from power line via an auxiliary current transformer. Measurement signal is transmitted by optical fibers, which is resistant to electromagnetic induction and noise. With careful design and the use of digital signal processing technology, the whole system can meet 0.5% accuracy for metering and provides large dynamic range coupled with good accuracy for protective relaying use.
基金supported by the Science and Technology Project of SGCC under Contract 5500-202140126A-0-0-00.
文摘Voltage measuring equipment in power grids often requires capacitive voltage dividers to realize conversion of high voltage electrical quantities to low voltage signal quantities.The new floating-ground capacitive voltage divider(FG-CVD)can eliminate original lumped capacitors and its supporting insulation structures by adopting precisely designed parasitic capacitance as a high voltage arm capacitor,which can greatly save cost and volume.However,the utilization of parasitic capacitance not only makes FG-CVD sensitive to external conductor interference,but also causes transient waveform distortion,especially when the connecting lead between the FG-CVD and high-voltage conductor is lengthy.On the basis of transfer characteristic analysis,this paper proposes a complete parameter design method for FG-CVD to improve stability of its transfer ratio under interference of the external conductor.Moreover,by establishing a wideband equivalent model with lead inductance,the transient waveform distortion problem of FG-CVD is well explained,and a resistance compensation scheme is also proposed to reduce ratio error.Finally,a 500:1 FG-CVD prototype with a measurement bandwidth of 2MHz is developed.Experimental results show the prototype has high accuracy in both power frequency and lightning pulse voltage measurement,and ratio error decreases from 20.33%to less than 1.3%.
基金Project supported by the National Basic Research Program of China(Grant No.2010CB327704)the National Natural Science Foundation of China(Grant No.51272022)+2 种基金the Program for New Century Excellent Talents in University of Ministry of Education of China(Grant No.NCET-10-0220)the Research Fund for the Doctoral Program of Higher Education,China(Grant No.20120009130005)the Fundamental Research Funds for the Central Universities,China(Grant No.2012JBZ001)
文摘We investigate the effects of （N,N’-diphenyl）-N,N’-bis（1-naphthyl）-1,1’-biphenyl-4,4’-diamine （NPB） buffer layers on charge collection in inverted ZnO/MEH-PPV hybrid devices. The insertion of a 3-nm NPB thin layer enhances the efficiency of charge collection by improving charge transport and reducing the interface energy barrier, resulting in better device performances. S-shaped light J–V curve appears when the thickness of the NPB layer reaches 25 nm, which is induced by the inefficient charge extraction from MEH-PPV to Ag. Capacitance–voltage measurements are performed to further investigate the influence of the NPB layer on charge collection from both simulations and experiments.
文摘With the increase of the operating voltage and enlargement of the size of the capacitor voltage transformer(CVT),the additional measurement error caused by stray capacitance coupling and leakage current along the polluted surface of the CVT becomes noticeable.The equipotential shielding CVT(EPSCVT)was proposed and designed by the authors to mitigate these effects.An improved conceptual design option of the EPS-CVT is presented in this paper with special references to this study to improve the shielding effect without the increase of shielding capacitance.A proposed method of non-uniform capacitance configuration can improve the shielding effect significantly without an increase of the external shielding capacitance.Based on this achievement,the potential difference and the capacitive current exchange between the internal measuring system and external shielding systems are significantly reduced.In the evaluation of the shielding effect for the influence of stray capacitance,compared with a conventional CVT with equal capacitance,EPS-CVT can reduce the measurement error by two orders of magnitude.In addition,the measurement error caused by the leakage current can also be greatly reduced,especially for the reduction of the phase angle error.Based on the improved design method,a design scheme for an engineering application is proposed which can achieve effective shielding while ensuring as good a technical performance as the existing CVT.
