This paper focuses on the design of the inverter power stage connected with PV-grid which supports the contrived PV system. The increased number of grid connected photovoltaic (PV) inverters gave rise to problems conc...This paper focuses on the design of the inverter power stage connected with PV-grid which supports the contrived PV system. The increased number of grid connected photovoltaic (PV) inverters gave rise to problems concerning the stability and safety of the utility grid, as well as power quality issues. The proposed systems can overcome these issues and improve standard regulation methods for gird connected PV inverter. The maximum available voltage in the PV string is tracked by the power stage which has been planned and designed in such a way. The tracked voltage is boosted then. The important components to voltage source inverter (VSI) are boost inductor and input capacitor which are calculated. To get a clear sinusoidal output phase voltage of 230 V from a DC capacitance bus projected to deal with 400 V, the important inverter stage parameters have been planned and modeled in Mat lab. Each block stage of the converter is easily understandable by the Simlink of the dual stage DC-AC converter explanation. The control schemes which have been proposed would compromise with the inverter power stage which forms the neat grid system. The existing renewable energy sources in the laboratory are integrated by the proposed control.展开更多
In this paper, period-doubling bifurcation in a two-stage power factor correction converter is analyzed by using the method of incremental harmonic balance （IHB） and Floquet theory. A two-stage power factor correcti...In this paper, period-doubling bifurcation in a two-stage power factor correction converter is analyzed by using the method of incremental harmonic balance （IHB） and Floquet theory. A two-stage power factor correction converter typically employs a cascade configuration of a pre-regulator boost power factor correction converter with average current mode control to achieve a near unity power factor and a tightly regulated post-regulator DC-DC Buck converter with voltage feedback control to regulate the output voltage. Based on the assumption that the tightly regulated postregulator DC-DC Buck converter is represented as a constant power sink and some other assumptions, the simplified model of the two-stage power factor correction converter is derived and its approximate periodic solution is calculated by the method of IHB. And then, the stability of the system is investigated by using Floquet theory and the stable boundaries are presented on the selected parameter spaces. Finally, some experimental results are given to confirm the effectiveness of the theoretical analysis.展开更多
This paper constructs the index system of the regional division of the development stage of China's wind power resources,including the index of energy,the index of wind energy endowments and other indices.Based on...This paper constructs the index system of the regional division of the development stage of China's wind power resources,including the index of energy,the index of wind energy endowments and other indices.Based on principal component analysis and layered clustering analysis of these indices,and combined with the conceptual function of the development and utilization stage of the wind power,this paper divides the development and utilization stage of the wind power into four stages taking province as the basic yardstick:optimization growth stage,the rapid growth stage,the slow growth stage and the initial growth stage.In addition,this paper briefly discusses the basic strategy that should be adopted in each development stage of wind power resources.展开更多
The use of an electrical network as close as possible to its limits can lead to its instability in the event of a high amplitude disturbance. The damping of system oscillations can be achieved by conventional means of...The use of an electrical network as close as possible to its limits can lead to its instability in the event of a high amplitude disturbance. The damping of system oscillations can be achieved by conventional means of voltage and speed regulation but also by FACTS (Flexible AC Transmission Systems) devices, which are increasingly used in power networks. In this work, optimal control coordination between a hybrid power flow controller and a three-level inverter was used to improve the transient stability of a transmission line. The UPFC is a combination of a serial compensator (SSSC) and a parallel compensator (STATCOM) both connected to a DC-LINK DC bus. The SSSC acts as a voltage source for the network and injects a voltage that can be adjusted in phase and amplitude in addition to the network voltage;the STATCOM acts as a current source. The approach used is tested in the Matlab Simulink environment on a single machine network. Optimal controller tuning gives a better transient stability improvement by reducing the transport angle oscillations from 248.17% to 9.85%.展开更多
The problem of harmonic pollution has brought wide attention with the increase of power customers. The adoption of the technology of active power factor correction (APFC) with advanced high frequency power converter i...The problem of harmonic pollution has brought wide attention with the increase of power customers. The adoption of the technology of active power factor correction (APFC) with advanced high frequency power converter is a more efficient solution to the problem of harmonic pollution. A single stage isolated high power factor AC/DC converter, which features wide range DC output, high power factor, lower harmonic pollution in input current, and phase shift PWM full bridge circuit can achieve soft switching. The principle of the circuit topology and the reasons of voltage surges across the power switch are analyzed. Experiment results illustrate that this circuit has the advantages of high power factor and lower harmonic distortion.展开更多
The full bridge zero voltage zero current switching （ FB-ZVZCS ） , which could adjust the output power by keeping the duty ratio of lagging leg constant and changing the duty ratio of leading leg, was a common circu...The full bridge zero voltage zero current switching （ FB-ZVZCS ） , which could adjust the output power by keeping the duty ratio of lagging leg constant and changing the duty ratio of leading leg, was a common circuit of soft switching arc welding inverter power source. However, when the duty ratio of leading leg was reduced to zero, the output power stayed the constant value instead of becoming zero. The working status and waveforms of some major parameters were studied in this paper while the duty ratio of leading leg was zero. It was concluded that the minimum output power of soft switching inverter was related to the charging voltage of paraUel capacitors, and the output power also could be reduced by reducing the duty ratio of lagging leg. A novel two-stage continuous PWM control method that could switch working-mode between full bridge and half bridge was put forward in this paper. This kind of control method could further reduce the output power of soft switching inverter in order to meet the requirement of low heat input of sheet metal welding.展开更多
In this review article, a stage-convertible RF power amplifier designed with a 0.18-μm RF CMOS process is described. A method to implement a low-power matching network is an essential technology for the stage-convert...In this review article, a stage-convertible RF power amplifier designed with a 0.18-μm RF CMOS process is described. A method to implement a low-power matching network is an essential technology for the stage-convertible power amplifier. Various low-power matching networks with distributed active transformers as an output power combiner are compared in terms of the amounts of undesired coupling, the chip size, and the amount of power loss. The feasibility of a differential line inductor for the stage-convertible power amplifier is assessed and explained. Finally, we show that the differential line inductor is a realistic means of reducing the overall chip size, enhancing the quality factor of the matching network, and minimizing the undesired coupling between the inter-stage matching network and any output matching network. Additionally, the operating mechanism of the stage-convertible power amplifier using the differential line inductor for a low-power matching network is described in detail.展开更多
There are abundant water power resources in the Yalong River which are suitable for the large hydroelectric engineering. But a reliability study should be made for the valley which liable to frequent earthquakes. The ...There are abundant water power resources in the Yalong River which are suitable for the large hydroelectric engineering. But a reliability study should be made for the valley which liable to frequent earthquakes. The color infrared aerophotos, multi-spectral photography and thermal infrared scanning had been specially done besides MSS image, processing. Researches on remote sensing applications to engineering geology, hydrogeology, deformation of neo-tectonics, Iandslide, mud-rock flow, ecological environment and geographical information system had been carried out by more than 20 research units.展开更多
With the increase of the clock frequency and silicon integration, power aware computing has become a critical concern in the design of the embedded processor and system-on-chip （SoC）. Dynamic voltage scaling （DVS）...With the increase of the clock frequency and silicon integration, power aware computing has become a critical concern in the design of the embedded processor and system-on-chip （SoC）. Dynamic voltage scaling （DVS） is an effective method for low-power designs. However, traditional DVS methods have two deficiencies. First, they have a conservative safety margin which is not necessary for most of the time. Second, they are exclusively concerned with the critical stage and ignore the significant potential free slack time of the noncritical stage. These factors lead to a large amount of power waste. In this paper, a novel pipeline structure with ultra-low power consumption is proposed. It cuts off the safety margin and takes use of the noncritical stages at the same time. A prototype pipeline is designed in 0.13 μm technology and analyzed. The result shows that a large amount of energy can be saved by using this structure. Compared with the fixed voltage case, 50% of the energy can be saved, and with respect to the traditional adaptive voltage scaling design, 37.8% of the energy can be saved.展开更多
At high speeds and high resolution, the Pipeline ADCs are becoming popular. The options of different stage resolutions in Pipelined ADCs and their effect on speed, power dissipation, linearity and area are discussed i...At high speeds and high resolution, the Pipeline ADCs are becoming popular. The options of different stage resolutions in Pipelined ADCs and their effect on speed, power dissipation, linearity and area are discussed in this paper. The basic building blocks viz. Op-Amp Sample and Hold circuit, sub converter, D/A Converter and residue amplifier used in every stage is assumed to be identical. The sub converters are implemented using flash architectures. The paper implements a 10-bit 50 Mega Samples/Sec Pipelined A/D Converter using 1, 1.5, 2, 3, 4 and 5 bits/stage conversion techniques and discusses about its impact on speed, power, area, and linearity. The design implementation uses 0.18 μm CMOS technology and a 3.3 V power supply. The paper concludes stating that a resolution of 2 bits/stage is optimum for a Pipelined ADC and to reduce the design complexity, we may go up to 3 bits/stage.展开更多
The system planning of the Northwest China 330 kV Power System from present to the year 2000 is introduced in this paper. Some technical problems arising from the system planning, such as network configuration, system...The system planning of the Northwest China 330 kV Power System from present to the year 2000 is introduced in this paper. Some technical problems arising from the system planning, such as network configuration, system stability and reactive power compensation etc. are also briefly summarized.展开更多
为了应对可再生能源输出和负荷需求不确定性带来的风险,提出了一种联合风机、光伏、负荷和储能运营的虚拟电厂(virtual power plant,VPP)鲁棒优化调度模型。优化目标是在源荷不确定性的情况下,最大化系统收益并降低惩罚成本,从而构建了m...为了应对可再生能源输出和负荷需求不确定性带来的风险,提出了一种联合风机、光伏、负荷和储能运营的虚拟电厂(virtual power plant,VPP)鲁棒优化调度模型。优化目标是在源荷不确定性的情况下,最大化系统收益并降低惩罚成本,从而构建了min-max-min形式的两阶段鲁棒优化模型。首先,在预调度阶段,根据源荷侧的预测值来制定VPP日前收益最大的出力方案;其次,再调度阶段结合前一阶段的决策,VPP利用购售电和储能系统等快速调节出力,应对不确定性变量的波动进而在最坏情况下实现最佳运行效益;再次,在交互迭代中,使用了对偶变换及列约束生成算法(columnand-constraint generation C&CG)。最后,仿真结果不仅验证了模型的经济性、鲁棒性和稳定性,而且表明优化调度方案有助于减少不确定性带来的波动,最终实现平衡VPP的经济效益和运营风险。展开更多
文摘This paper focuses on the design of the inverter power stage connected with PV-grid which supports the contrived PV system. The increased number of grid connected photovoltaic (PV) inverters gave rise to problems concerning the stability and safety of the utility grid, as well as power quality issues. The proposed systems can overcome these issues and improve standard regulation methods for gird connected PV inverter. The maximum available voltage in the PV string is tracked by the power stage which has been planned and designed in such a way. The tracked voltage is boosted then. The important components to voltage source inverter (VSI) are boost inductor and input capacitor which are calculated. To get a clear sinusoidal output phase voltage of 230 V from a DC capacitance bus projected to deal with 400 V, the important inverter stage parameters have been planned and modeled in Mat lab. Each block stage of the converter is easily understandable by the Simlink of the dual stage DC-AC converter explanation. The control schemes which have been proposed would compromise with the inverter power stage which forms the neat grid system. The existing renewable energy sources in the laboratory are integrated by the proposed control.
基金supported by the National Natural Science Foundation of China (Grant No.51007068)the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No.20100201120028)+1 种基金the Fundamental Research Funds for the Central Universities of Chinathe State Key Laboratory of Electrical Insulation and Power Equipment of China (Grant No.EIPE10303)
文摘In this paper, period-doubling bifurcation in a two-stage power factor correction converter is analyzed by using the method of incremental harmonic balance （IHB） and Floquet theory. A two-stage power factor correction converter typically employs a cascade configuration of a pre-regulator boost power factor correction converter with average current mode control to achieve a near unity power factor and a tightly regulated post-regulator DC-DC Buck converter with voltage feedback control to regulate the output voltage. Based on the assumption that the tightly regulated postregulator DC-DC Buck converter is represented as a constant power sink and some other assumptions, the simplified model of the two-stage power factor correction converter is derived and its approximate periodic solution is calculated by the method of IHB. And then, the stability of the system is investigated by using Floquet theory and the stable boundaries are presented on the selected parameter spaces. Finally, some experimental results are given to confirm the effectiveness of the theoretical analysis.
基金National Basic Research and Development Program(973)(Grant no.2007CB210306)
文摘This paper constructs the index system of the regional division of the development stage of China's wind power resources,including the index of energy,the index of wind energy endowments and other indices.Based on principal component analysis and layered clustering analysis of these indices,and combined with the conceptual function of the development and utilization stage of the wind power,this paper divides the development and utilization stage of the wind power into four stages taking province as the basic yardstick:optimization growth stage,the rapid growth stage,the slow growth stage and the initial growth stage.In addition,this paper briefly discusses the basic strategy that should be adopted in each development stage of wind power resources.
文摘The use of an electrical network as close as possible to its limits can lead to its instability in the event of a high amplitude disturbance. The damping of system oscillations can be achieved by conventional means of voltage and speed regulation but also by FACTS (Flexible AC Transmission Systems) devices, which are increasingly used in power networks. In this work, optimal control coordination between a hybrid power flow controller and a three-level inverter was used to improve the transient stability of a transmission line. The UPFC is a combination of a serial compensator (SSSC) and a parallel compensator (STATCOM) both connected to a DC-LINK DC bus. The SSSC acts as a voltage source for the network and injects a voltage that can be adjusted in phase and amplitude in addition to the network voltage;the STATCOM acts as a current source. The approach used is tested in the Matlab Simulink environment on a single machine network. Optimal controller tuning gives a better transient stability improvement by reducing the transport angle oscillations from 248.17% to 9.85%.
文摘The problem of harmonic pollution has brought wide attention with the increase of power customers. The adoption of the technology of active power factor correction (APFC) with advanced high frequency power converter is a more efficient solution to the problem of harmonic pollution. A single stage isolated high power factor AC/DC converter, which features wide range DC output, high power factor, lower harmonic pollution in input current, and phase shift PWM full bridge circuit can achieve soft switching. The principle of the circuit topology and the reasons of voltage surges across the power switch are analyzed. Experiment results illustrate that this circuit has the advantages of high power factor and lower harmonic distortion.
文摘The full bridge zero voltage zero current switching （ FB-ZVZCS ） , which could adjust the output power by keeping the duty ratio of lagging leg constant and changing the duty ratio of leading leg, was a common circuit of soft switching arc welding inverter power source. However, when the duty ratio of leading leg was reduced to zero, the output power stayed the constant value instead of becoming zero. The working status and waveforms of some major parameters were studied in this paper while the duty ratio of leading leg was zero. It was concluded that the minimum output power of soft switching inverter was related to the charging voltage of paraUel capacitors, and the output power also could be reduced by reducing the duty ratio of lagging leg. A novel two-stage continuous PWM control method that could switch working-mode between full bridge and half bridge was put forward in this paper. This kind of control method could further reduce the output power of soft switching inverter in order to meet the requirement of low heat input of sheet metal welding.
文摘In this review article, a stage-convertible RF power amplifier designed with a 0.18-μm RF CMOS process is described. A method to implement a low-power matching network is an essential technology for the stage-convertible power amplifier. Various low-power matching networks with distributed active transformers as an output power combiner are compared in terms of the amounts of undesired coupling, the chip size, and the amount of power loss. The feasibility of a differential line inductor for the stage-convertible power amplifier is assessed and explained. Finally, we show that the differential line inductor is a realistic means of reducing the overall chip size, enhancing the quality factor of the matching network, and minimizing the undesired coupling between the inter-stage matching network and any output matching network. Additionally, the operating mechanism of the stage-convertible power amplifier using the differential line inductor for a low-power matching network is described in detail.
文摘There are abundant water power resources in the Yalong River which are suitable for the large hydroelectric engineering. But a reliability study should be made for the valley which liable to frequent earthquakes. The color infrared aerophotos, multi-spectral photography and thermal infrared scanning had been specially done besides MSS image, processing. Researches on remote sensing applications to engineering geology, hydrogeology, deformation of neo-tectonics, Iandslide, mud-rock flow, ecological environment and geographical information system had been carried out by more than 20 research units.
基金supported by the Important National S&T Special Project of China under Grant No.2011ZX01034-002-001-2the Fundamental Research Funds for the Central Universities under Grant No.ZYGX2009J026
文摘With the increase of the clock frequency and silicon integration, power aware computing has become a critical concern in the design of the embedded processor and system-on-chip （SoC）. Dynamic voltage scaling （DVS） is an effective method for low-power designs. However, traditional DVS methods have two deficiencies. First, they have a conservative safety margin which is not necessary for most of the time. Second, they are exclusively concerned with the critical stage and ignore the significant potential free slack time of the noncritical stage. These factors lead to a large amount of power waste. In this paper, a novel pipeline structure with ultra-low power consumption is proposed. It cuts off the safety margin and takes use of the noncritical stages at the same time. A prototype pipeline is designed in 0.13 μm technology and analyzed. The result shows that a large amount of energy can be saved by using this structure. Compared with the fixed voltage case, 50% of the energy can be saved, and with respect to the traditional adaptive voltage scaling design, 37.8% of the energy can be saved.
文摘At high speeds and high resolution, the Pipeline ADCs are becoming popular. The options of different stage resolutions in Pipelined ADCs and their effect on speed, power dissipation, linearity and area are discussed in this paper. The basic building blocks viz. Op-Amp Sample and Hold circuit, sub converter, D/A Converter and residue amplifier used in every stage is assumed to be identical. The sub converters are implemented using flash architectures. The paper implements a 10-bit 50 Mega Samples/Sec Pipelined A/D Converter using 1, 1.5, 2, 3, 4 and 5 bits/stage conversion techniques and discusses about its impact on speed, power, area, and linearity. The design implementation uses 0.18 μm CMOS technology and a 3.3 V power supply. The paper concludes stating that a resolution of 2 bits/stage is optimum for a Pipelined ADC and to reduce the design complexity, we may go up to 3 bits/stage.
文摘The system planning of the Northwest China 330 kV Power System from present to the year 2000 is introduced in this paper. Some technical problems arising from the system planning, such as network configuration, system stability and reactive power compensation etc. are also briefly summarized.
文摘为了应对可再生能源输出和负荷需求不确定性带来的风险,提出了一种联合风机、光伏、负荷和储能运营的虚拟电厂(virtual power plant,VPP)鲁棒优化调度模型。优化目标是在源荷不确定性的情况下,最大化系统收益并降低惩罚成本,从而构建了min-max-min形式的两阶段鲁棒优化模型。首先,在预调度阶段,根据源荷侧的预测值来制定VPP日前收益最大的出力方案;其次,再调度阶段结合前一阶段的决策,VPP利用购售电和储能系统等快速调节出力,应对不确定性变量的波动进而在最坏情况下实现最佳运行效益;再次,在交互迭代中,使用了对偶变换及列约束生成算法(columnand-constraint generation C&CG)。最后,仿真结果不仅验证了模型的经济性、鲁棒性和稳定性,而且表明优化调度方案有助于减少不确定性带来的波动,最终实现平衡VPP的经济效益和运营风险。
