A Fast and Accurate Synchronization Technique for Extraction of Symmetrical Components

Abstract

This paper introduces an approach for the real-time extraction of the frequency, phase angle, and symmetrical components of the grid signal, which is of great importance for many applications in power systems such as power quality and protection. The proposed method is based on the concept of the adaptive notch filter that provides a fast and accurate estimation of the symmetrical components in the presence of frequency and amplitude variations. In addition, the system offers a high degree of immunity and insensitivity to power system disturbances, harmonics, and other types of pollutions that exist in the grid signal. The simplicity of the structure makes the method suitable for both software and hardware implementations. Moreover, this very simple and very powerful tool can be used as a synchronization technique, which further simplifies the control issues currently challenging the integration of distributed energy technologies into the electricity grid. Mathematical derivations are presented to describe the principles of operation, and experimental results confirm the validity of the analytical work.

Research on Technology of Grid-Connected/Islanded Smooth Switchover of Microgrid

“…From literature [14], we can know that if we get cosine and sine of synchronous rotary angle ωt+θ by adaptive notch filter(ANF) and transform original voltage to dq rotating coordinate system, the voltage contains information such as amplitude, frequency and phase. Both controlled quantity of the modified quasi-synchronization controller and V/f controller are voltage in dq rotating coordinate system.…”

“…As shown in Fig.6,take microgrid system as an example, according to literature [14],sine and cosine value of the synchronous rotation angle of bus voltage can be obtained.Then by the means of Park transformation, the voltage in dq rotating coordinate system…”

A New Synchronization Algorithm for Grid-Connected Inverters

“…Based on the theory of symmetrical components [26], the positive sequence components of three-phase utility voltages can be obtained as follows…”

Seamless Grid Synchronization of a Proportional+Resonant Control-Based Voltage Controller Considering Non-Linear Loads under Islanded Mode

“…In the event of any grid faults or intentional switchover, the inverter has to operate as a voltage source to supply power to the local load under islanded mode [2].However, the transient performance of the inverter output voltage control is limited due to the characteristics of the non-zero output impedance of the inverter, the accurate voltage regulation becomes more difficult when the nonlinear or unbalanced load is connected to the inverter [2][3][4][5]. The design of a multi loop voltage controller has been studied conventionally to improve the dynamic response of the inverter [6][7][8][9][10][11][12][13][14][15][16][17], and different types of controllers for harmonics compensation, such as Proportional+Integral (PI), Proportional+Resonant (PR) and repetitive based methods, etc., have been proposed [4][5][6][7][8][9][10][11][12][13]. Among these controllers, the harmonic compensation method using the Proportional+Multi Resonant (P+MR) controller has attracted attention because it is simpler to implement than the PI-based harmonics compensation method and the positive and negative sequence components can be controlled simultaneously by one controller [13,14].…”

“…Therefore, the phase of generated voltage reference can be smoothly synchronized with the phase When the grid fault is recovered or the strategic islanding is no longer required, the inverter operation is switched from the islanded mode to the grid-connected mode. During this transition, the phase of the inverter output voltage is to be synchronized with the phase of the grid voltage, and the Phase Locked Loop (PLL) has been usually used for synchronization [15][16][17][18][19]. The PI-based grid synchronization technique was implemented in [10,20] as the partial study of indirect current control based inverter operation which includes the inner filter capacitor voltage loop.…”