This paper first discusses the operating principle of instantaneous reactive power theory. Then, the theory is introduced into shunt active power filter and its control scheme is studied. Finally, Matlab/Simulink powe...This paper first discusses the operating principle of instantaneous reactive power theory. Then, the theory is introduced into shunt active power filter and its control scheme is studied. Finally, Matlab/Simulink power system toolbox is used to simulate the system. In the simulation model, as the most common harmonic source, 3-phase thyristor bridge rectifier circuit is constructed. The simulation results before and after the shunt active filter was switched to the system corresponding to different firing angles of the thyristors are presented and analyzed, which demonstrate the practicability and reliability of the proposed shunt active filter scheme.展开更多
The source reactive-current compensation is crucial in energy transmission efficiency. The compensator design in frequency-domain was already widely discussed and examined. This paper presents results of a study on ho...The source reactive-current compensation is crucial in energy transmission efficiency. The compensator design in frequency-domain was already widely discussed and examined. This paper presents results of a study on how to design reactive compensators in time-domain. It’s the first time the reactive compensator have been designed in time domain. The example of compensator design was presented.展开更多
Due to the development of Distributed Generation (DG), which is installed in Medium-Voltage Distribution Networks (MVDNs) such as generators based on renewable energy (e.g., wind energy or solar energy), voltage contr...Due to the development of Distributed Generation (DG), which is installed in Medium-Voltage Distribution Networks (MVDNs) such as generators based on renewable energy (e.g., wind energy or solar energy), voltage control is currently a very important issue. The voltage is now regulated at the MV busbars acting on the On-Load Tap Changer of the HV/MV transformer. This method does not guarantee the correct voltage value in the network nodes when the distributed generators deliver their power. In this paper an approach based on Sensitivity Theory is shown, in order to control the node voltages regulating the reactive power exchanged between the network and the dispersed generators. The automatic distributed voltage regulation is a particular topic of the Smart Grids.展开更多
随着出力具有随机波动性特征的分布式电源渗透率的不断攀升以及城市电缆化率的进程加速,有源配电网线路中无功过剩和过电压的现象日益明显,对动态无功补偿装置的经济性、可靠性和精准调控能力提出更高要求。在电流源型静止同步补偿器的...随着出力具有随机波动性特征的分布式电源渗透率的不断攀升以及城市电缆化率的进程加速,有源配电网线路中无功过剩和过电压的现象日益明显,对动态无功补偿装置的经济性、可靠性和精准调控能力提出更高要求。在电流源型静止同步补偿器的基础上,该文结合双旋转移相变压器的连续调节特性,提出一种新型旋转式无功补偿器(novel rotary var compensator,NRVC)拓扑电路。通过构建NRVC稳态数学模型,深入分析得到NRVC补偿调控机理及其补偿容量约束关系。针对NRVC结构特点,提出基于瞬时无功理论的无功补偿控制策略,其中功率外环可对功率因数进行精确控制,电流内环加入限幅环节有效限流,提高装置运行可靠性。通过仿真及动模实验验证所提拓扑及其控制策略的有效性,结果验证了NRVC具备双向、连续调节补偿无功的能力,具有调节精度高、谐波畸变率低的优点。展开更多
Finite control set-model predictive control (FCS-MPC) is employed in this paper to control the operation of a three-phase grid-connected string inverter based on a direct PQ control scheme. The main objective is to ac...Finite control set-model predictive control (FCS-MPC) is employed in this paper to control the operation of a three-phase grid-connected string inverter based on a direct PQ control scheme. The main objective is to achieve high-performance decoupled control of the active and reactive powers injected to the grid from distributed energy resources (DER).The FCS-MPC scheme instantaneously searches for and applies the optimum inverter switching state that can achieve certain goals, such as minimum deviation between reference and actual power;so that both power components (P and Q) are well controlled to their reference values.In addition, an effective method to attenuate undesired cross coupling between the P and Q control loops, which occurs only during transient operation, is investigated. The proposed method is based on the variation of the weight factors of the terms of the FCS-MPC cost function, so a higher weight factor is assigned to the cost function term that is exposed to greater disturbance. Empirical formulae of optimum weight factors as functions of the reference active and reactive power signals are proposed and mathematically derived. The investigated FCS-MPC control scheme is incorporated with the LVRT function to support the grid voltage in fulfilling and accomplishing the up-to-date grid codes. The LVRT algorithm is based on a modification of the references of active and reactive powers as functions of the instantaneous grid voltage such that suitable values of P and Q are injected to the grid during voltage sag.The performance of the elaborated FCS-MPC PQ scheme is studied under various operating scenarios, including steady-state and transient conditions. Results demonstrate the validity and effectiveness of the proposed scheme with regard to the achievement of high-performance operation and quick response of grid-tied inverters during normal and fault modes.展开更多
文摘This paper first discusses the operating principle of instantaneous reactive power theory. Then, the theory is introduced into shunt active power filter and its control scheme is studied. Finally, Matlab/Simulink power system toolbox is used to simulate the system. In the simulation model, as the most common harmonic source, 3-phase thyristor bridge rectifier circuit is constructed. The simulation results before and after the shunt active filter was switched to the system corresponding to different firing angles of the thyristors are presented and analyzed, which demonstrate the practicability and reliability of the proposed shunt active filter scheme.
文摘The source reactive-current compensation is crucial in energy transmission efficiency. The compensator design in frequency-domain was already widely discussed and examined. This paper presents results of a study on how to design reactive compensators in time-domain. It’s the first time the reactive compensator have been designed in time domain. The example of compensator design was presented.
文摘Due to the development of Distributed Generation (DG), which is installed in Medium-Voltage Distribution Networks (MVDNs) such as generators based on renewable energy (e.g., wind energy or solar energy), voltage control is currently a very important issue. The voltage is now regulated at the MV busbars acting on the On-Load Tap Changer of the HV/MV transformer. This method does not guarantee the correct voltage value in the network nodes when the distributed generators deliver their power. In this paper an approach based on Sensitivity Theory is shown, in order to control the node voltages regulating the reactive power exchanged between the network and the dispersed generators. The automatic distributed voltage regulation is a particular topic of the Smart Grids.
文摘随着出力具有随机波动性特征的分布式电源渗透率的不断攀升以及城市电缆化率的进程加速,有源配电网线路中无功过剩和过电压的现象日益明显,对动态无功补偿装置的经济性、可靠性和精准调控能力提出更高要求。在电流源型静止同步补偿器的基础上,该文结合双旋转移相变压器的连续调节特性,提出一种新型旋转式无功补偿器(novel rotary var compensator,NRVC)拓扑电路。通过构建NRVC稳态数学模型,深入分析得到NRVC补偿调控机理及其补偿容量约束关系。针对NRVC结构特点,提出基于瞬时无功理论的无功补偿控制策略,其中功率外环可对功率因数进行精确控制,电流内环加入限幅环节有效限流,提高装置运行可靠性。通过仿真及动模实验验证所提拓扑及其控制策略的有效性,结果验证了NRVC具备双向、连续调节补偿无功的能力,具有调节精度高、谐波畸变率低的优点。
文摘Finite control set-model predictive control (FCS-MPC) is employed in this paper to control the operation of a three-phase grid-connected string inverter based on a direct PQ control scheme. The main objective is to achieve high-performance decoupled control of the active and reactive powers injected to the grid from distributed energy resources (DER).The FCS-MPC scheme instantaneously searches for and applies the optimum inverter switching state that can achieve certain goals, such as minimum deviation between reference and actual power;so that both power components (P and Q) are well controlled to their reference values.In addition, an effective method to attenuate undesired cross coupling between the P and Q control loops, which occurs only during transient operation, is investigated. The proposed method is based on the variation of the weight factors of the terms of the FCS-MPC cost function, so a higher weight factor is assigned to the cost function term that is exposed to greater disturbance. Empirical formulae of optimum weight factors as functions of the reference active and reactive power signals are proposed and mathematically derived. The investigated FCS-MPC control scheme is incorporated with the LVRT function to support the grid voltage in fulfilling and accomplishing the up-to-date grid codes. The LVRT algorithm is based on a modification of the references of active and reactive powers as functions of the instantaneous grid voltage such that suitable values of P and Q are injected to the grid during voltage sag.The performance of the elaborated FCS-MPC PQ scheme is studied under various operating scenarios, including steady-state and transient conditions. Results demonstrate the validity and effectiveness of the proposed scheme with regard to the achievement of high-performance operation and quick response of grid-tied inverters during normal and fault modes.
