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
In the present study, the influence of natural convection on the lamellar eutectic growth is determined by a phase-field-lattice Boltzmann study for Al-Cu eutectic alloy. The mass difference resulting from concentrati...In the present study, the influence of natural convection on the lamellar eutectic growth is determined by a phase-field-lattice Boltzmann study for Al-Cu eutectic alloy. The mass difference resulting from concentration difference led to the fluid flow, and a robust parallel and adaptive mesh refinement algorithm was employed to improve the computational efficiency without any compromising accuracy. Results show that the existence of natural convection would affect the growth undercooling and thus control the interface shape by adjusting the lamellar width. In particular, by alternating the magnitude of the solute expansion coefficient, the strength of the natural convection is changed. Corresponding microstructure patterns are discussed and compared with those under no-convection conditions.展开更多
Active power filter (APF) using novel virtual line-flux-linkage oriented control strategy can not only realizes no phase-locked-loop (PLL) control, but also achieves a good inhibitory effect to interfere. However, the...Active power filter (APF) using novel virtual line-flux-linkage oriented control strategy can not only realizes no phase-locked-loop (PLL) control, but also achieves a good inhibitory effect to interfere. However, there are some problems in the conventional method, such as the error of amplitude, the shift of phase angle and the non-determinacy of initial oriented angle. In this paper, two one-order low-pass filters are adopted instead of the pure integrator in the virtual line-flux-linkage observer, which can steady the phase and amplitude. Furthermore, an original scheme of harmonics detection under the rotating coordinate is advanced based on the simplified space vector pulse width modulation (SVPWM) strategy. Meanwhile, by using the new SVPWM algorithm, the voltage space vector diagram of the three-level inverter can be simplified and applied into that of two-level inverter, and this makes the control for Neutral Point potential easier.展开更多
The ρ(NH2) infrared(IR) frequencies and the corresponding full width at half maximum(FWHM) values for(CH3)2 NH2 FeⅢ M Ⅱ(HCOO)6(DMFe M, M = Ni, Zn, Cu, Fe, and Mg) are analyzed at various temperatures by using the e...The ρ(NH2) infrared(IR) frequencies and the corresponding full width at half maximum(FWHM) values for(CH3)2 NH2 FeⅢ M Ⅱ(HCOO)6(DMFe M, M = Ni, Zn, Cu, Fe, and Mg) are analyzed at various temperatures by using the experimental data from the literature. For the analysis of the IR frequencies of the ρ(NH2) mode which is associated with the structural phase transitions in those metal structures, the temperature dependence of the mode frequency is assumed as an order parameter and the IR frequencies are calculated by using the molecular field theory. Also, the temperature dependence of the IR frequencies and of the damping constant as calculated from the models of pseudospin(dynamic disorder of dimethylammonium(DMA+) cations)–phonon coupling(PS) and of the energy fluctuation(EF), is fitted to the observed data for the wavenumber and FWHM of the ρ(NH2) IR mode of the niccolites studied here. We find that the observed behavior of the IR frequencies and the FWHM of this mode can be described adequately by the models studied for the crystalline structures of interest. This method of calculating the frequencies(IR and Raman) and FWHM of modes which are responsible for the phase transitions can also be applied to some other metal organic frameworks.展开更多
This paper mainly concentrates on design of improved controller and its implementation based on single phase synchronous reference frame theory (SRFT) for Dynamic Voltage Restorer (DVR) compensating voltage sag partic...This paper mainly concentrates on design of improved controller and its implementation based on single phase synchronous reference frame theory (SRFT) for Dynamic Voltage Restorer (DVR) compensating voltage sag particularly for nonlinear load. In case of single phase distribution line with nonlinear load, the complexity of controller’s design becomes more serious issue. The present single phase and/or three phase theories applicable to DVR shows poor response to restore voltage sag in case of nonlinear load due to presence of harmonics. Hence restoration of voltage sag in single phase nonlinear load connected system has been a serious concern. Therefore, new controller for DVR has been proposed incorporating effective design concept for fundamental component extraction in case of nonlinear load. The single phase SRFT based main controller for DVR works on two separate closed path viz. feed forward path for quick transient response and feedback path for reducing the steady state error. Moreover, pre-sag mitigation strategy of DVR has been adapted through these two aforementioned paths. Complete design of proposed controller is based on phasor analysis. It also consist of proportional integral (PI) controller to reduce the error in the DC-link voltage during compensation time. The controller performance has been verified in MATLAB Simulink for both types (linear and nonlinear) of load. The results obtained indicates that the proposed controller is effective in its performance.展开更多
该文以三相电压型脉宽调制(pulse width modulation,PWM)整流器为研究对象,提出一种基于新型开关表的直接功率控制(direct power control,DPC)策略。首先,根据两相旋转dq坐标系下整流器数学模型计算开关矢量对有功功率和无功功率的控制...该文以三相电压型脉宽调制(pulse width modulation,PWM)整流器为研究对象,提出一种基于新型开关表的直接功率控制(direct power control,DPC)策略。首先,根据两相旋转dq坐标系下整流器数学模型计算开关矢量对有功功率和无功功率的控制幅度,并归一化处理进行定量分析,以此为基础将传统DPC的12扇区重新划分为24扇区。然后,设计有功功率差值区间判断器,根据其输出值Cp和有功功率与无功功率滞环比较器的输出值Sp、Sq,选择当前扇区最佳开关矢量构造新型开关表,实现对有功功率的精确控制。仿真对比表明,该新型开关表不仅克服传统开关表对无功功率控制能力差的缺点,而且改善网侧电流总谐波失真,降低输出直流电压波动和有功功率与无功功率脉动。最后,搭建一台800W三相电压型PWM整流器样机,通过对比实验验证所提控制策略的正确性和有效性。展开更多
In this paper, a three-phase inverter with renewable source input is integrated into a grid in synchronization for power sharing by load. In previous topologies, the DC source connected inverter is not synchronized to...In this paper, a three-phase inverter with renewable source input is integrated into a grid in synchronization for power sharing by load. In previous topologies, the DC source connected inverter is not synchronized to the grid which causes harmonics and voltage distortions damaging the load and the source. In order to ensure power sharing by the load from the inverter and the grid, the inverter needs to be operated in synchronization to the grid with the same voltage mag-nitude, frequency and phase as that of the grid voltage. In this paper, the com-plete power from the load is shared by the three-phase grid and the three-phase inverter module reducing the consumption from the conventional grid. This is achieved using the PLL for the reference angular frequency generation with feedback from grid voltage and is connected to the sinusoidal PWM generator. The PLL is used to generate unit vector template reference signals for the signal generator operating the six-switch inverter. The inverter and grid are inter-connected through LC filter for the reduction of harmonics. The power sharing, voltage, and current graphs with THD analysis are analyzed with the help of the MATLAB software.展开更多
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.
基金supported by the National Natural Science Foundation of China[grant number U1537202]the TsinghuaGeneral Motor International collaboration project[grant number 20153000354]+1 种基金the UK Royal Society through the Newton International Fellowship Schemethe National Laboratory for Information Science and Technology in Tsinghua University for access to supercomputing facilities
文摘In the present study, the influence of natural convection on the lamellar eutectic growth is determined by a phase-field-lattice Boltzmann study for Al-Cu eutectic alloy. The mass difference resulting from concentration difference led to the fluid flow, and a robust parallel and adaptive mesh refinement algorithm was employed to improve the computational efficiency without any compromising accuracy. Results show that the existence of natural convection would affect the growth undercooling and thus control the interface shape by adjusting the lamellar width. In particular, by alternating the magnitude of the solute expansion coefficient, the strength of the natural convection is changed. Corresponding microstructure patterns are discussed and compared with those under no-convection conditions.
文摘Active power filter (APF) using novel virtual line-flux-linkage oriented control strategy can not only realizes no phase-locked-loop (PLL) control, but also achieves a good inhibitory effect to interfere. However, there are some problems in the conventional method, such as the error of amplitude, the shift of phase angle and the non-determinacy of initial oriented angle. In this paper, two one-order low-pass filters are adopted instead of the pure integrator in the virtual line-flux-linkage observer, which can steady the phase and amplitude. Furthermore, an original scheme of harmonics detection under the rotating coordinate is advanced based on the simplified space vector pulse width modulation (SVPWM) strategy. Meanwhile, by using the new SVPWM algorithm, the voltage space vector diagram of the three-level inverter can be simplified and applied into that of two-level inverter, and this makes the control for Neutral Point potential easier.
文摘The ρ(NH2) infrared(IR) frequencies and the corresponding full width at half maximum(FWHM) values for(CH3)2 NH2 FeⅢ M Ⅱ(HCOO)6(DMFe M, M = Ni, Zn, Cu, Fe, and Mg) are analyzed at various temperatures by using the experimental data from the literature. For the analysis of the IR frequencies of the ρ(NH2) mode which is associated with the structural phase transitions in those metal structures, the temperature dependence of the mode frequency is assumed as an order parameter and the IR frequencies are calculated by using the molecular field theory. Also, the temperature dependence of the IR frequencies and of the damping constant as calculated from the models of pseudospin(dynamic disorder of dimethylammonium(DMA+) cations)–phonon coupling(PS) and of the energy fluctuation(EF), is fitted to the observed data for the wavenumber and FWHM of the ρ(NH2) IR mode of the niccolites studied here. We find that the observed behavior of the IR frequencies and the FWHM of this mode can be described adequately by the models studied for the crystalline structures of interest. This method of calculating the frequencies(IR and Raman) and FWHM of modes which are responsible for the phase transitions can also be applied to some other metal organic frameworks.
文摘This paper mainly concentrates on design of improved controller and its implementation based on single phase synchronous reference frame theory (SRFT) for Dynamic Voltage Restorer (DVR) compensating voltage sag particularly for nonlinear load. In case of single phase distribution line with nonlinear load, the complexity of controller’s design becomes more serious issue. The present single phase and/or three phase theories applicable to DVR shows poor response to restore voltage sag in case of nonlinear load due to presence of harmonics. Hence restoration of voltage sag in single phase nonlinear load connected system has been a serious concern. Therefore, new controller for DVR has been proposed incorporating effective design concept for fundamental component extraction in case of nonlinear load. The single phase SRFT based main controller for DVR works on two separate closed path viz. feed forward path for quick transient response and feedback path for reducing the steady state error. Moreover, pre-sag mitigation strategy of DVR has been adapted through these two aforementioned paths. Complete design of proposed controller is based on phasor analysis. It also consist of proportional integral (PI) controller to reduce the error in the DC-link voltage during compensation time. The controller performance has been verified in MATLAB Simulink for both types (linear and nonlinear) of load. The results obtained indicates that the proposed controller is effective in its performance.
文摘该文以三相电压型脉宽调制(pulse width modulation,PWM)整流器为研究对象,提出一种基于新型开关表的直接功率控制(direct power control,DPC)策略。首先,根据两相旋转dq坐标系下整流器数学模型计算开关矢量对有功功率和无功功率的控制幅度,并归一化处理进行定量分析,以此为基础将传统DPC的12扇区重新划分为24扇区。然后,设计有功功率差值区间判断器,根据其输出值Cp和有功功率与无功功率滞环比较器的输出值Sp、Sq,选择当前扇区最佳开关矢量构造新型开关表,实现对有功功率的精确控制。仿真对比表明,该新型开关表不仅克服传统开关表对无功功率控制能力差的缺点,而且改善网侧电流总谐波失真,降低输出直流电压波动和有功功率与无功功率脉动。最后,搭建一台800W三相电压型PWM整流器样机,通过对比实验验证所提控制策略的正确性和有效性。
文摘In this paper, a three-phase inverter with renewable source input is integrated into a grid in synchronization for power sharing by load. In previous topologies, the DC source connected inverter is not synchronized to the grid which causes harmonics and voltage distortions damaging the load and the source. In order to ensure power sharing by the load from the inverter and the grid, the inverter needs to be operated in synchronization to the grid with the same voltage mag-nitude, frequency and phase as that of the grid voltage. In this paper, the com-plete power from the load is shared by the three-phase grid and the three-phase inverter module reducing the consumption from the conventional grid. This is achieved using the PLL for the reference angular frequency generation with feedback from grid voltage and is connected to the sinusoidal PWM generator. The PLL is used to generate unit vector template reference signals for the signal generator operating the six-switch inverter. The inverter and grid are inter-connected through LC filter for the reduction of harmonics. The power sharing, voltage, and current graphs with THD analysis are analyzed with the help of the MATLAB software.
