This paper presents a comprehensive study that includes the sizing and power flow by series and parallel inverters in a distributed generation system(DGs)that integrates the system of hybrid wind photovoltaic with a u...This paper presents a comprehensive study that includes the sizing and power flow by series and parallel inverters in a distributed generation system(DGs)that integrates the system of hybrid wind photovoltaic with a unified power quality conditioner(UPQC).In addition to supplying active power to the utility grid,the system of hybrid wind photovoltaic functions as a UPQC,compensating reactive power and suppressing the harmonic load currents.Additionally,the load is supplied with harmonic-free,balanced and regulated output voltages.Since PVWind-UPQC is established on a dual compensation scheme,the series inverter works like a sinusoidal current source,while the parallel inverter works like a sinusoidal voltage source.Consequently,a smooth alteration from interconnected operating modes to island operating modes and vice versa can be achieved without load voltage transients.Since PV-Wind-UPQC inverters handle the energy generated through the hybrid wind photovoltaic system and the energy demanded through the load,the converters should be sized cautiously.A detailed study of the flow of power via the PV-Wind-UPQC is imperative to gain a complete understanding of the system operation and the proper design of the converters.Thus,curves that allow the sizing of the power converters according to the power flow via the converters are presented and discussed.Simulation results are presented to assess both steady state and dynamic performances of the grid connected hybrid system of PV-Wind-UPQC.This investigation is verified by simulating and analyzing the results with Matlab/Simulink.展开更多
由于统一电能质量调节器(unified power quality conditioner,UPQC)系统结构复杂、控制难度大,单一的控制策略不足以使其应对电网系统中的各种故障情况。因此,文中采用一种线性自抗扰控制(linear active disturbance rejection control,...由于统一电能质量调节器(unified power quality conditioner,UPQC)系统结构复杂、控制难度大,单一的控制策略不足以使其应对电网系统中的各种故障情况。因此,文中采用一种线性自抗扰控制(linear active disturbance rejection control,LADRC)与模型预测控制(model predictive control,MPC)的复合控制策略。在电压外环控制中采用LADRC策略以提高系统快速性与抗扰性,并给电流内环提供更精确的参考电流信号;在电流内环控制中采用电流MPC策略以提高跟踪参考信号的能力与系统的鲁棒性,同时对模型预测的空间电压矢量的分区进行优化,减少控制器计算量,在保证输出电流质量的前提下提高运算速度。最后,基于MATLAB/Simulink仿真实验平台对系统进行建模仿真,结果验证了采用LADRC-MPC控制策略对电网电压暂升/暂降、负载不对称引起的电流畸变与谐波污染等综合电能质量问题,可以起到更好的补偿效果,对电网电压的支撑能力也更强。展开更多
This paper presents a novel and efficient control scheme for unified power quality conditioner （UPQC） based on three-level neutral point clamped （NPC） inverter using fuzzy logic techniques. The proposed UPQC is ca...This paper presents a novel and efficient control scheme for unified power quality conditioner （UPQC） based on three-level neutral point clamped （NPC） inverter using fuzzy logic techniques. The proposed UPQC is capable of mitigating source current harmonics and compensate all voltage disturbances such as voltage sags, swells, unbalances and harmonics. It is designed by the integration of series and shunt active filters （AFs） sharing a common DC bus capacitor. The DC voltage is maintained constant using proportional integral voltage controller. The synchronous reference frame （SRF） theory is used to get the reference signals for shunt active power filters （APFs） and the power reactive theory （p-q theory） for series APFs. The shunt and series APF reference signals derived from the control algorithm and sensed signals are injected in two controllers to generate switching signals. To improve the UPQC capability, fuzzy logic techniques are introduced to control the series APF. The performances of the proposed UPQC system are evaluated in terms of power factor correction, mitigation of voltage or current harmonics and all other voltage disturbances compensation using Matlab-Simulink software and SimPowerSystem toolbox. The simulation results illustrate the performance of the proposed UPQC at the common connection point of the nonlinear load to improve the power energy quality.展开更多
Unified power quality conditioner(UPQC)holds the capability of solving power quality problems,especially shows good performance in the voltage sag compensation. In this paper, a compensation strategy based on simultan...Unified power quality conditioner(UPQC)holds the capability of solving power quality problems,especially shows good performance in the voltage sag compensation. In this paper, a compensation strategy based on simultaneous reactive power injection for UPQC(namely UPQC-SRI) is proposed to address the issue of voltage sag. The proposed UPQC-SRI determines the injection angle of compensation voltage with consideration of optimal configuration of UPQC current-carrying.Moreover, the compensation strategy also considers the current-carrying limit of UPQC, and then the zero active power injection region of UPQC-SRI(also called UPQCSRI region) is obtained. Under the conditions which exceed the UPQC-SRI region, the limit value of shunt current is determined by this proposed strategy. Finally, the proposed strategy and the corresponding algorithm are verified under the PSCAD/EMTDC platform. The result indicates the proposed UPQC-SRI strategy in this paper can provide more persistent voltage sag compensation than the previous strategies for the sensitive load.展开更多
This paper presents a comprehensive control strategy for unified power quality conditioners(UPQCs) to compensate for both voltage and current quality problems.The controllers for the series and shunt components of the...This paper presents a comprehensive control strategy for unified power quality conditioners(UPQCs) to compensate for both voltage and current quality problems.The controllers for the series and shunt components of the UPQC are, equally, divided into three blocks: à main controller, which deals with the fundamental-frequency issues such as active and reactive power flow;` harmonic controller, which ensures zero-error tracking while compensating voltage and current harmonics;′ the set-point generation block, which handles the different control objectives of the UPQC. The controller design procedure has been simplified to the selection of three parameters for each converter. Furthermore, the proposed strategy can be implemented measuring only four variables, which represents a reasonable number of sensors. In addition, a pulse width modulation(PWM)-based modulation with fixed switching frequency is used for both converters. The proposed control strategy has been validated experimentally under different conditions, including grid-frequency variations.展开更多
The development of DC custom power protection devices is still in infancy that confines the sensitive loads integrated into medium-voltage(MV) and low-voltage(LV) DC networks. Considering the DC doubly-fed induction g...The development of DC custom power protection devices is still in infancy that confines the sensitive loads integrated into medium-voltage(MV) and low-voltage(LV) DC networks. Considering the DC doubly-fed induction generator(DCDFIG) based wind energy conversion system(WECS), this paper proposes a dual active bridge(DAB) based DC unified power quality conditioner(DC-UPQC) with the integration of superconducting magnetic energy storage(SMES) to maintain the terminal voltage of DC-DFIG and regulate the current flow. The principle of the proposed DC-UPQC has three parts, i.e., parallel-side DAB(PDAB), series-side DAB(SDAB), and SMES,used for the voltage compensation, current and power regulation, and energy storage, respectively. The circuit principle of the PDAB and SDAB and the modeling of SMES are analyzed in this paper. A DC dual control strategy is also proposed to deal with the DC voltage oscillation generated by the AC-side asymmetrical fault. A case study of DC-DFIG interfaced with DC power grid is carried out, integrated with the proposed SMES-based DC-UPQC to verify the high-power applications of the proposed structure. Finally, an experiment is implemented, and the results demonstrate the correctness of the theoretical analysis and the feasibility of the proposed structure.展开更多
This paper proposes a cascaded low-pass filter(CLPF)scheme for the control of a unified power quality conditioner(UPQC)installed for enhancing the power quality of an electric vehicle(EV)charging station.With the inco...This paper proposes a cascaded low-pass filter(CLPF)scheme for the control of a unified power quality conditioner(UPQC)installed for enhancing the power quality of an electric vehicle(EV)charging station.With the incorporation of UPQC,the EV charging station draws sinusoidal currents at unity power factor and the supply voltage is maintained at the nominal value at the charger input.In the CLPF scheme,theα-βcomponents of the load current are individually processed through a cascade connection of two LPFs to determine the corresponding fundamental orthogonal components.Based on thus determined components,the instantaneous and peak value and phase angle of the fundamental positive sequence component(FPSC)of the load current are computed.Similarly,the corresponding quantities related to the load and supply voltages are also computed with the CLPF scheme.With the computations related to the load current and supply voltage,the unit voltage templates(UVTs),power factor and fundamental active component(FAC)of the load current are calculated.For the control of shunt compensation,reference currents are generated based on the FAC of the load current and UVTs.Alternately,the control of series compensation is employed with the help of UVTs and peak amplitude of the FPSC of the load voltage.The performance of CLPF scheme-based extraction is compared with that of the earlier reported schemes through simulation and experimental studies.The performance comparison reveals a faster dynamic and more accurate steady-state response with the proposed scheme.The performance analysis of the proposed CLPF scheme-based control of a UPQC deployed at the EV charging station for different operating conditions demonstrates station operation with requisite reactive power compensation and mitigation of voltage sag/swell,and prevention of propagation of harmonic and unbalanced currents into the grid.This results in increased reliability of charger operation,energy savings and increased efficiency of the distribution network.展开更多
针对模块化多电平统一电能质量调节器(modular multilevel unified power quality conditioner, MMC-UPQC)六桥臂结构下的单相桥臂故障问题,提出了一种五桥臂拓扑,这种新型拓扑可实现故障情况下的电能质量补偿。首先,对MMC-UPQC串并联...针对模块化多电平统一电能质量调节器(modular multilevel unified power quality conditioner, MMC-UPQC)六桥臂结构下的单相桥臂故障问题,提出了一种五桥臂拓扑,这种新型拓扑可实现故障情况下的电能质量补偿。首先,对MMC-UPQC串并联侧的数学模型进行分析,提出了一种复合模型预测控制(hybrid model predictive control,H-MPC),所提控制方法结合了有限集模型预测控制(finite-control-set model predictive control, FCS-MPC)以及快速模型预测控制(fast model predictive control, F-MPC)。然后,通过构建两侧独立的价值函数减少了控制方法的计算量,同时也实现了五桥臂解耦控制。最后,相比传统线性(例如PI)和非线性(例如无源控制passivity-based control,PBC)的控制策略,所提复合模型预测控制在电压补偿、负序电压抑制以及谐波电流补偿等方面具有一定优势,并在一定程度上避免了复杂的参数整定及坐标变化环节。仿真实验结果证明了所提控制方法的可行性和优越性。展开更多
文摘This paper presents a comprehensive study that includes the sizing and power flow by series and parallel inverters in a distributed generation system(DGs)that integrates the system of hybrid wind photovoltaic with a unified power quality conditioner(UPQC).In addition to supplying active power to the utility grid,the system of hybrid wind photovoltaic functions as a UPQC,compensating reactive power and suppressing the harmonic load currents.Additionally,the load is supplied with harmonic-free,balanced and regulated output voltages.Since PVWind-UPQC is established on a dual compensation scheme,the series inverter works like a sinusoidal current source,while the parallel inverter works like a sinusoidal voltage source.Consequently,a smooth alteration from interconnected operating modes to island operating modes and vice versa can be achieved without load voltage transients.Since PV-Wind-UPQC inverters handle the energy generated through the hybrid wind photovoltaic system and the energy demanded through the load,the converters should be sized cautiously.A detailed study of the flow of power via the PV-Wind-UPQC is imperative to gain a complete understanding of the system operation and the proper design of the converters.Thus,curves that allow the sizing of the power converters according to the power flow via the converters are presented and discussed.Simulation results are presented to assess both steady state and dynamic performances of the grid connected hybrid system of PV-Wind-UPQC.This investigation is verified by simulating and analyzing the results with Matlab/Simulink.
文摘由于统一电能质量调节器(unified power quality conditioner,UPQC)系统结构复杂、控制难度大,单一的控制策略不足以使其应对电网系统中的各种故障情况。因此,文中采用一种线性自抗扰控制(linear active disturbance rejection control,LADRC)与模型预测控制(model predictive control,MPC)的复合控制策略。在电压外环控制中采用LADRC策略以提高系统快速性与抗扰性,并给电流内环提供更精确的参考电流信号;在电流内环控制中采用电流MPC策略以提高跟踪参考信号的能力与系统的鲁棒性,同时对模型预测的空间电压矢量的分区进行优化,减少控制器计算量,在保证输出电流质量的前提下提高运算速度。最后,基于MATLAB/Simulink仿真实验平台对系统进行建模仿真,结果验证了采用LADRC-MPC控制策略对电网电压暂升/暂降、负载不对称引起的电流畸变与谐波污染等综合电能质量问题,可以起到更好的补偿效果,对电网电压的支撑能力也更强。
文摘This paper presents a novel and efficient control scheme for unified power quality conditioner （UPQC） based on three-level neutral point clamped （NPC） inverter using fuzzy logic techniques. The proposed UPQC is capable of mitigating source current harmonics and compensate all voltage disturbances such as voltage sags, swells, unbalances and harmonics. It is designed by the integration of series and shunt active filters （AFs） sharing a common DC bus capacitor. The DC voltage is maintained constant using proportional integral voltage controller. The synchronous reference frame （SRF） theory is used to get the reference signals for shunt active power filters （APFs） and the power reactive theory （p-q theory） for series APFs. The shunt and series APF reference signals derived from the control algorithm and sensed signals are injected in two controllers to generate switching signals. To improve the UPQC capability, fuzzy logic techniques are introduced to control the series APF. The performances of the proposed UPQC system are evaluated in terms of power factor correction, mitigation of voltage or current harmonics and all other voltage disturbances compensation using Matlab-Simulink software and SimPowerSystem toolbox. The simulation results illustrate the performance of the proposed UPQC at the common connection point of the nonlinear load to improve the power energy quality.
基金supported by the twelfth five-year National Mega-projects of Science and Technology (2011BAA01B03)
文摘Unified power quality conditioner(UPQC)holds the capability of solving power quality problems,especially shows good performance in the voltage sag compensation. In this paper, a compensation strategy based on simultaneous reactive power injection for UPQC(namely UPQC-SRI) is proposed to address the issue of voltage sag. The proposed UPQC-SRI determines the injection angle of compensation voltage with consideration of optimal configuration of UPQC current-carrying.Moreover, the compensation strategy also considers the current-carrying limit of UPQC, and then the zero active power injection region of UPQC-SRI(also called UPQCSRI region) is obtained. Under the conditions which exceed the UPQC-SRI region, the limit value of shunt current is determined by this proposed strategy. Finally, the proposed strategy and the corresponding algorithm are verified under the PSCAD/EMTDC platform. The result indicates the proposed UPQC-SRI strategy in this paper can provide more persistent voltage sag compensation than the previous strategies for the sensitive load.
基金partially financed by the Spanish Government RETOS programme(No.ENE2011-28527-C0401)research Grant FPI BES-2012-055790
文摘This paper presents a comprehensive control strategy for unified power quality conditioners(UPQCs) to compensate for both voltage and current quality problems.The controllers for the series and shunt components of the UPQC are, equally, divided into three blocks: à main controller, which deals with the fundamental-frequency issues such as active and reactive power flow;` harmonic controller, which ensures zero-error tracking while compensating voltage and current harmonics;′ the set-point generation block, which handles the different control objectives of the UPQC. The controller design procedure has been simplified to the selection of three parameters for each converter. Furthermore, the proposed strategy can be implemented measuring only four variables, which represents a reasonable number of sensors. In addition, a pulse width modulation(PWM)-based modulation with fixed switching frequency is used for both converters. The proposed control strategy has been validated experimentally under different conditions, including grid-frequency variations.
文摘The development of DC custom power protection devices is still in infancy that confines the sensitive loads integrated into medium-voltage(MV) and low-voltage(LV) DC networks. Considering the DC doubly-fed induction generator(DCDFIG) based wind energy conversion system(WECS), this paper proposes a dual active bridge(DAB) based DC unified power quality conditioner(DC-UPQC) with the integration of superconducting magnetic energy storage(SMES) to maintain the terminal voltage of DC-DFIG and regulate the current flow. The principle of the proposed DC-UPQC has three parts, i.e., parallel-side DAB(PDAB), series-side DAB(SDAB), and SMES,used for the voltage compensation, current and power regulation, and energy storage, respectively. The circuit principle of the PDAB and SDAB and the modeling of SMES are analyzed in this paper. A DC dual control strategy is also proposed to deal with the DC voltage oscillation generated by the AC-side asymmetrical fault. A case study of DC-DFIG interfaced with DC power grid is carried out, integrated with the proposed SMES-based DC-UPQC to verify the high-power applications of the proposed structure. Finally, an experiment is implemented, and the results demonstrate the correctness of the theoretical analysis and the feasibility of the proposed structure.
文摘This paper proposes a cascaded low-pass filter(CLPF)scheme for the control of a unified power quality conditioner(UPQC)installed for enhancing the power quality of an electric vehicle(EV)charging station.With the incorporation of UPQC,the EV charging station draws sinusoidal currents at unity power factor and the supply voltage is maintained at the nominal value at the charger input.In the CLPF scheme,theα-βcomponents of the load current are individually processed through a cascade connection of two LPFs to determine the corresponding fundamental orthogonal components.Based on thus determined components,the instantaneous and peak value and phase angle of the fundamental positive sequence component(FPSC)of the load current are computed.Similarly,the corresponding quantities related to the load and supply voltages are also computed with the CLPF scheme.With the computations related to the load current and supply voltage,the unit voltage templates(UVTs),power factor and fundamental active component(FAC)of the load current are calculated.For the control of shunt compensation,reference currents are generated based on the FAC of the load current and UVTs.Alternately,the control of series compensation is employed with the help of UVTs and peak amplitude of the FPSC of the load voltage.The performance of CLPF scheme-based extraction is compared with that of the earlier reported schemes through simulation and experimental studies.The performance comparison reveals a faster dynamic and more accurate steady-state response with the proposed scheme.The performance analysis of the proposed CLPF scheme-based control of a UPQC deployed at the EV charging station for different operating conditions demonstrates station operation with requisite reactive power compensation and mitigation of voltage sag/swell,and prevention of propagation of harmonic and unbalanced currents into the grid.This results in increased reliability of charger operation,energy savings and increased efficiency of the distribution network.
文摘针对模块化多电平统一电能质量调节器(modular multilevel unified power quality conditioner, MMC-UPQC)六桥臂结构下的单相桥臂故障问题,提出了一种五桥臂拓扑,这种新型拓扑可实现故障情况下的电能质量补偿。首先,对MMC-UPQC串并联侧的数学模型进行分析,提出了一种复合模型预测控制(hybrid model predictive control,H-MPC),所提控制方法结合了有限集模型预测控制(finite-control-set model predictive control, FCS-MPC)以及快速模型预测控制(fast model predictive control, F-MPC)。然后,通过构建两侧独立的价值函数减少了控制方法的计算量,同时也实现了五桥臂解耦控制。最后,相比传统线性(例如PI)和非线性(例如无源控制passivity-based control,PBC)的控制策略,所提复合模型预测控制在电压补偿、负序电压抑制以及谐波电流补偿等方面具有一定优势,并在一定程度上避免了复杂的参数整定及坐标变化环节。仿真实验结果证明了所提控制方法的可行性和优越性。
