DQ impedance-based method has been widely used to study the stability of three-phase converter systems.As the dq impedance model of each converter depends on its local dq reference frame,the dq impedance modeling of c...DQ impedance-based method has been widely used to study the stability of three-phase converter systems.As the dq impedance model of each converter depends on its local dq reference frame,the dq impedance modeling of complex converter networks gets complicated.Because the reference frames of different converters might not fully align,depending on the structure.Thus,in order to find an accurate impedance model of a complex network for stability analysis,converting the impedances of different converters into a common reference frame is required.This paper presents a comprehensive investigation on the transformation of dq impedances to a common reference frame in complex converter networks.Four different methods are introduced and analyzed in a systematic way.Moreover,a rigorous comparison among these approaches is carried out,where the method with the simplest transformation procedure is finally suggested for the modeling of complex converter networks.The performed analysis is verified by injecting two independent small-signal perturbations into the d and the q axis,and doing a point-by-point impedance measurement.展开更多
根据三相光伏并网逆变器dq旋转坐标系下数学模型,推导了三相光伏逆变器输出有功功率、无功功率和电网电压、逆变器输出电压、电流之间关系。提出基于空间矢量调制的无差拍功率控制策略,实现三相光伏并网逆器有功功率、无功功率的快速跟...根据三相光伏并网逆变器dq旋转坐标系下数学模型,推导了三相光伏逆变器输出有功功率、无功功率和电网电压、逆变器输出电压、电流之间关系。提出基于空间矢量调制的无差拍功率控制策略,实现三相光伏并网逆器有功功率、无功功率的快速跟踪和解耦控制,输出三相电流波形正弦度好,有功功率和无功功率波动小,且输出频率固定,有利于滤波电感的设计。在一台12 k W样机上进行了实验验证,实验结果表明三相光伏并网逆变器具有良好的静、动态特性,无差拍功率控制策略正确可行。展开更多
This paper presents the Synchronous Reference Frame Theory (SRF) based Phase Locked Loop (PLL) to enhance the performance of Dynamic Voltage Controller (DVR). In a grid connected power conversion system, a critical co...This paper presents the Synchronous Reference Frame Theory (SRF) based Phase Locked Loop (PLL) to enhance the performance of Dynamic Voltage Controller (DVR). In a grid connected power conversion system, a critical component is the Phase-Locked Loop (PLL) that generates the grid voltage’s frequency and phase angle for the grid synchronization. For grid voltage control, accurate and fast responding PLLs are required to provide phase angle and frequency measurements of the grid voltage. Therefore, SRF based PLL is presented in this work and it calculates the phase angle accurately and effectively. This paper also presents a novel feedback mechanism for SRF-PLL which uses the estimated frequency and phase to achieve grid control. The fundamental signal of the grid voltage is extracted by low pass filter and a unit value controller to generate a unity sine reference signal for the feedback network. In particular, the performance of the SRF-PLL in the three-phase PV fed grid connected system is analyzed under the different power quality issues such as voltage sag and swell. In addition, a detailed study on synchronous reference frame theory is presented. An appropriate control algorithm for DVR is developed and the validity of the proposed configuration is verified through MATLAB simulation results as well as experimental results under different operating conditions.展开更多
基金The support of the first and fourth authors is given by National Key R&D Program of China,2018YFB0905200.The support for the second and third authors is coming from BIRD171227/17 project of the University of Padova.
文摘DQ impedance-based method has been widely used to study the stability of three-phase converter systems.As the dq impedance model of each converter depends on its local dq reference frame,the dq impedance modeling of complex converter networks gets complicated.Because the reference frames of different converters might not fully align,depending on the structure.Thus,in order to find an accurate impedance model of a complex network for stability analysis,converting the impedances of different converters into a common reference frame is required.This paper presents a comprehensive investigation on the transformation of dq impedances to a common reference frame in complex converter networks.Four different methods are introduced and analyzed in a systematic way.Moreover,a rigorous comparison among these approaches is carried out,where the method with the simplest transformation procedure is finally suggested for the modeling of complex converter networks.The performed analysis is verified by injecting two independent small-signal perturbations into the d and the q axis,and doing a point-by-point impedance measurement.
文摘根据三相光伏并网逆变器dq旋转坐标系下数学模型,推导了三相光伏逆变器输出有功功率、无功功率和电网电压、逆变器输出电压、电流之间关系。提出基于空间矢量调制的无差拍功率控制策略,实现三相光伏并网逆器有功功率、无功功率的快速跟踪和解耦控制,输出三相电流波形正弦度好,有功功率和无功功率波动小,且输出频率固定,有利于滤波电感的设计。在一台12 k W样机上进行了实验验证,实验结果表明三相光伏并网逆变器具有良好的静、动态特性,无差拍功率控制策略正确可行。
文摘This paper presents the Synchronous Reference Frame Theory (SRF) based Phase Locked Loop (PLL) to enhance the performance of Dynamic Voltage Controller (DVR). In a grid connected power conversion system, a critical component is the Phase-Locked Loop (PLL) that generates the grid voltage’s frequency and phase angle for the grid synchronization. For grid voltage control, accurate and fast responding PLLs are required to provide phase angle and frequency measurements of the grid voltage. Therefore, SRF based PLL is presented in this work and it calculates the phase angle accurately and effectively. This paper also presents a novel feedback mechanism for SRF-PLL which uses the estimated frequency and phase to achieve grid control. The fundamental signal of the grid voltage is extracted by low pass filter and a unit value controller to generate a unity sine reference signal for the feedback network. In particular, the performance of the SRF-PLL in the three-phase PV fed grid connected system is analyzed under the different power quality issues such as voltage sag and swell. In addition, a detailed study on synchronous reference frame theory is presented. An appropriate control algorithm for DVR is developed and the validity of the proposed configuration is verified through MATLAB simulation results as well as experimental results under different operating conditions.
