Complex dynamical phenomenon was studied in the single phase H-bridge inverter which was controlled by either a peak current or a valley current. The state functions and the discrete iterative map equations were estab...Complex dynamical phenomenon was studied in the single phase H-bridge inverter which was controlled by either a peak current or a valley current. The state functions and the discrete iterative map equations were established to analyze the dynamical phenomenon in the single phase H-bridge inverter. The dynamical characteristics of the single phase H- bridge inverter, such as time domain waveform diagram, bifurcation diagram, and folding map, were obtained by using the numerical calculation when the circuit parameters varied in specific range. Moreover, the simulation results were obtained by using the OrCAD-PSpice software to validate the numerical calculation. Both the numerical calculation and the circuit simulation show that the symmetrical dynamical phenomenon occurs in the single phase H-bridge inverter controlled by the peak current or the valley current.展开更多
Biocatalysis with nicotinamide adenine dinucleotide phosphate(NADP)-dependent oxidoreductases faces a challenge in improving the efficiency of the costly cofactor utilization.Although enzyme fusion can offer cofactor ...Biocatalysis with nicotinamide adenine dinucleotide phosphate(NADP)-dependent oxidoreductases faces a challenge in improving the efficiency of the costly cofactor utilization.Although enzyme fusion can offer cofactor regeneration,the high-volume input and limited cofactor recyclability still make the enzymatic processes unsustainable.Therefore,it is of great significance to reduce cofactor input in a fusion enzyme(FuE)system,but no successful practice has been reported.Herein,we design a decapeptide bridge,RRRQRRRARR(R10),with high affinity for NADPH to construct fusion oxidoreductases(phenylacetone monooxygenase and phosphite dehydrogenase)for ester synthesis and NADP recycling.The peptide bridge enables electrostatic cofactor channeling that transports NADPH/NADP^(+)across the peptide between the enzymes’NADP-binding pockets,so the fusion enzyme(FuE-R10)presents 2.1-folds and 2.0-folds higher conversions than mixed free enzymes and a flexible linker(GGGGSGGGGS)-fused enzyme,respectively,at NADPH/FuE of 0.1.The fusion enzyme,FuE-R5,bridged by a half-shortened linker,is proved more effective in facilitating cofactor channeling;compared to the mixed free enzymes,FuE-R5 exhibits two orders of magnitude reduction of NADPH input in ester synthesis.The work has thus demonstrated the potential of the cofactor bridging strategy in the development of sustainable cofactor-dependent cascade biocatalysis.展开更多
The paper presents a new STATCOM system based on H-bridge inverter. It can be used in mine power network. It has been commonly verified for the positive effects of SVG on the reactive power compensation and voltage fl...The paper presents a new STATCOM system based on H-bridge inverter. It can be used in mine power network. It has been commonly verified for the positive effects of SVG on the reactive power compensation and voltage fluctuation suppression. This paper focuses on a generalized structure of multilevel power converter where individual voltage sources are not necessarily the same. The cascade H-bridge consists of two cells, high-voltage cell and low-voltage cell. The high-voltage cell is responsible for voltage lifting, while the low-voltage cell is responsible for PWM modulation. If two cells are cascaded with DC voltages in a ratio of 2:1, the single-phase output voltage can reach 7 levels. Increasing voltage levels of output waveform can bring up AC current quality, optimize harmonic spectrum and enhance converter efficiency. The hybrid multilevel is characterized by per-phase series connection of a high-voltage H-bridge converter and a low-voltage H-bridge converter. Due to the different capacitor voltage, it is a key problem as to how to maintain the capacitor’s voltage at a reference level. Independent DC source can effectively ensure the DC voltage. Through the reactive power compensation technology, the three-phase voltage and current can remain at the same phase.展开更多
In recent days, the multilevel inverter technology is widely applied to domestic and industrial applications for medium voltage conversion. But, the power quality issues of the multilevel inverter limit the usage of m...In recent days, the multilevel inverter technology is widely applied to domestic and industrial applications for medium voltage conversion. But, the power quality issues of the multilevel inverter limit the usage of much sensitive equipment like medical instruments. The lower distortion level of the output voltage and current can generate a quality sinusoidal output voltage in inverters and they can be used for many applications. The harmonics can cause major problems in equipments due to the nonlinear loads connected with the power system. So, it is necessary to minimize the losses to raise its overall efficiency. In this paper, a new topology of seven level asymmetrical cascaded H-bridge multilevel inverter with a Fuzzy logic controller had been implemented to reduce the Total Harmonic Distortion (THD) and to improve the overall performance of the inverter. The proposed model is well suited for use with a solar PV application. In this topology, only six IGBT switches are used with three different voltage ratings of PV modules (1:2:4). The lower number of semiconductor switches leads to minimizing overall di/dt ratings and voltage stress on each switches and switching losses. The gate pulses generated by Sinusoidal Pulse Width Modulation (SPWM) technique with a Fuzzy logic controller are also introduced. A buck-boost converter is used to maintain the constant PV voltage level integrated by an MPPT technique followed by Perturb and Observer algorithm is also implemented. The MPPT is used to harness the maximum power of solar radiations under its various climatic conditions. The new topology is evaluated by a Matlab/Simulink model and compared with a hardware model. The results proved that the THD achieved by this topology is 1.66% and realized that it meets the IEEE harmonic standards.展开更多
This work presents an implementation of an innovative single phase multilevel inverter using capacitors with reduced switches. The proposed Capacitor pattern H-bridge Multilevel Inverter (CPHMLI) topology consists of ...This work presents an implementation of an innovative single phase multilevel inverter using capacitors with reduced switches. The proposed Capacitor pattern H-bridge Multilevel Inverter (CPHMLI) topology consists of a proper number of Capacitor connected with switches and power sources. The advanced switching control supplied by Pulse Width Modulation (PDPWM) to attain mixed staircase switching state. The charging and discharging mode are achieved by calculating the voltage error at the load. Furthermore, to accomplish the higher voltage levels at the output with less number of semiconductors switches and simple commutation designed using CPHMLI topology. To prove the performance and effectiveness of the proposed approach, a set of experiments performed under various load conditions using MATLAB tool.展开更多
为进一步提高中点电压钳制(neutral point clamped,NPC)H桥级联五电平逆变器的动态响应、降低控制器计算负担的同时确保装置低损耗运行,文中在电压矢量矩形区域分类的基础上,提出一种以满足动态响应和降低开关损耗为目标的两级优化模型...为进一步提高中点电压钳制(neutral point clamped,NPC)H桥级联五电平逆变器的动态响应、降低控制器计算负担的同时确保装置低损耗运行,文中在电压矢量矩形区域分类的基础上,提出一种以满足动态响应和降低开关损耗为目标的两级优化模型预测电压控制策略。首先根据逆变器数学模型和期望电流进行目标电压矢量计算、修正,接着基于矩形区域分类对目标电压矢量进行定位;并以定位后的候选矢量为基础,设计了两级优化目标函数以输出满足要求的最优矢量。仿真和实验结果验证了该方法的有效性,与空间矢量脉宽调制以及传统模型预测电流、电压控制策略相比,该文所研究的两级优化模型预测电压控制策略,在确保逆变器动态响应的前提下既能降低控制器计算负担,还能有效减少器件开关损耗。展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.51107016)the National Basic Research Program of China(Grant No.2013CB035605)the Postdoctoral Science Research Developmental Foundation of Heilongjiang Province,China(Grant No.LHB-Q12086)
文摘Complex dynamical phenomenon was studied in the single phase H-bridge inverter which was controlled by either a peak current or a valley current. The state functions and the discrete iterative map equations were established to analyze the dynamical phenomenon in the single phase H-bridge inverter. The dynamical characteristics of the single phase H- bridge inverter, such as time domain waveform diagram, bifurcation diagram, and folding map, were obtained by using the numerical calculation when the circuit parameters varied in specific range. Moreover, the simulation results were obtained by using the OrCAD-PSpice software to validate the numerical calculation. Both the numerical calculation and the circuit simulation show that the symmetrical dynamical phenomenon occurs in the single phase H-bridge inverter controlled by the peak current or the valley current.
文摘Biocatalysis with nicotinamide adenine dinucleotide phosphate(NADP)-dependent oxidoreductases faces a challenge in improving the efficiency of the costly cofactor utilization.Although enzyme fusion can offer cofactor regeneration,the high-volume input and limited cofactor recyclability still make the enzymatic processes unsustainable.Therefore,it is of great significance to reduce cofactor input in a fusion enzyme(FuE)system,but no successful practice has been reported.Herein,we design a decapeptide bridge,RRRQRRRARR(R10),with high affinity for NADPH to construct fusion oxidoreductases(phenylacetone monooxygenase and phosphite dehydrogenase)for ester synthesis and NADP recycling.The peptide bridge enables electrostatic cofactor channeling that transports NADPH/NADP^(+)across the peptide between the enzymes’NADP-binding pockets,so the fusion enzyme(FuE-R10)presents 2.1-folds and 2.0-folds higher conversions than mixed free enzymes and a flexible linker(GGGGSGGGGS)-fused enzyme,respectively,at NADPH/FuE of 0.1.The fusion enzyme,FuE-R5,bridged by a half-shortened linker,is proved more effective in facilitating cofactor channeling;compared to the mixed free enzymes,FuE-R5 exhibits two orders of magnitude reduction of NADPH input in ester synthesis.The work has thus demonstrated the potential of the cofactor bridging strategy in the development of sustainable cofactor-dependent cascade biocatalysis.
文摘The paper presents a new STATCOM system based on H-bridge inverter. It can be used in mine power network. It has been commonly verified for the positive effects of SVG on the reactive power compensation and voltage fluctuation suppression. This paper focuses on a generalized structure of multilevel power converter where individual voltage sources are not necessarily the same. The cascade H-bridge consists of two cells, high-voltage cell and low-voltage cell. The high-voltage cell is responsible for voltage lifting, while the low-voltage cell is responsible for PWM modulation. If two cells are cascaded with DC voltages in a ratio of 2:1, the single-phase output voltage can reach 7 levels. Increasing voltage levels of output waveform can bring up AC current quality, optimize harmonic spectrum and enhance converter efficiency. The hybrid multilevel is characterized by per-phase series connection of a high-voltage H-bridge converter and a low-voltage H-bridge converter. Due to the different capacitor voltage, it is a key problem as to how to maintain the capacitor’s voltage at a reference level. Independent DC source can effectively ensure the DC voltage. Through the reactive power compensation technology, the three-phase voltage and current can remain at the same phase.
文摘In recent days, the multilevel inverter technology is widely applied to domestic and industrial applications for medium voltage conversion. But, the power quality issues of the multilevel inverter limit the usage of much sensitive equipment like medical instruments. The lower distortion level of the output voltage and current can generate a quality sinusoidal output voltage in inverters and they can be used for many applications. The harmonics can cause major problems in equipments due to the nonlinear loads connected with the power system. So, it is necessary to minimize the losses to raise its overall efficiency. In this paper, a new topology of seven level asymmetrical cascaded H-bridge multilevel inverter with a Fuzzy logic controller had been implemented to reduce the Total Harmonic Distortion (THD) and to improve the overall performance of the inverter. The proposed model is well suited for use with a solar PV application. In this topology, only six IGBT switches are used with three different voltage ratings of PV modules (1:2:4). The lower number of semiconductor switches leads to minimizing overall di/dt ratings and voltage stress on each switches and switching losses. The gate pulses generated by Sinusoidal Pulse Width Modulation (SPWM) technique with a Fuzzy logic controller are also introduced. A buck-boost converter is used to maintain the constant PV voltage level integrated by an MPPT technique followed by Perturb and Observer algorithm is also implemented. The MPPT is used to harness the maximum power of solar radiations under its various climatic conditions. The new topology is evaluated by a Matlab/Simulink model and compared with a hardware model. The results proved that the THD achieved by this topology is 1.66% and realized that it meets the IEEE harmonic standards.
文摘This work presents an implementation of an innovative single phase multilevel inverter using capacitors with reduced switches. The proposed Capacitor pattern H-bridge Multilevel Inverter (CPHMLI) topology consists of a proper number of Capacitor connected with switches and power sources. The advanced switching control supplied by Pulse Width Modulation (PDPWM) to attain mixed staircase switching state. The charging and discharging mode are achieved by calculating the voltage error at the load. Furthermore, to accomplish the higher voltage levels at the output with less number of semiconductors switches and simple commutation designed using CPHMLI topology. To prove the performance and effectiveness of the proposed approach, a set of experiments performed under various load conditions using MATLAB tool.
文摘为进一步提高中点电压钳制(neutral point clamped,NPC)H桥级联五电平逆变器的动态响应、降低控制器计算负担的同时确保装置低损耗运行,文中在电压矢量矩形区域分类的基础上,提出一种以满足动态响应和降低开关损耗为目标的两级优化模型预测电压控制策略。首先根据逆变器数学模型和期望电流进行目标电压矢量计算、修正,接着基于矩形区域分类对目标电压矢量进行定位;并以定位后的候选矢量为基础,设计了两级优化目标函数以输出满足要求的最优矢量。仿真和实验结果验证了该方法的有效性,与空间矢量脉宽调制以及传统模型预测电流、电压控制策略相比,该文所研究的两级优化模型预测电压控制策略,在确保逆变器动态响应的前提下既能降低控制器计算负担,还能有效减少器件开关损耗。
