scholarly journals On Small Signal Frequency Stability under Virtual Inertia and the Role of PLLs

Energies ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 2372 ◽  
Author(s):  
Sohail Khan ◽  
Benoit Bletterie ◽  
Adolfo Anta ◽  
Wolfgang Gawlik
Keyword(s):  
Frequency Measurement ◽  
Frequency Stability ◽  
Signal Frequency ◽  
Stable Operation ◽  
Small Signal ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Low Pass ◽  
Virtual Inertia ◽  
The Impact

This paper presents a methodology that aims at identifying virtual inertia (VI) gain limitations from virtual synchronous generators (VSGs) while maintaining the frequency stability considering the delay associated with the frequency measurement process. The phase-locked loop (PLL) is typically used for frequency estimation that is used to calculate the rate of change of frequency (RoCoF) and it drives the VI loop. The PLL is generally accompanied by a low-pass filter that aims to suppress the impact of harmonics. This filter introduces a delay that when used with the VI control loop causes stability issues for high values of VI gain. A comparison of various PLL approaches suggests that certain variants tend to permit higher value of cut-off frequencies which can be utilized to increase the VI gain limit from VSG. This study presents a method by which the upper limit on VI gain can be quantified and related to the cut-off frequency of the PLL low pass filter that is indirectly representing the delay. It is performed using small signal frequency stability analysis on the frequency domain model of the grid with virtual inertia emulating VSG. The effective maximum VI gain from VSG is explored while satisfying the frequency measurement accuracy specification considering harmonics. The results show that the requirements of reaching a stable operation with sufficient stability margins can still be met with a faster PLL-based system and the potential increases in VI support from VSG can be quantified using the proposed method. The study has been first performed on a single machine single inverter bus (SMSIB) system and is generalized to the multi-machine and multi-inverter system.

A Rotor Flux Observer Based on Nonlinear Quadrature Double Compensation

2011 ◽  
Vol 128-129 ◽  
pp. 25-29
Author(s):  
Bo Fan ◽  
Xing Li ◽  
Jie Xin Pu ◽  
Jian Wei Ma ◽  
Ju Wei Zhang
Keyword(s):  
Induction Motor ◽  
Electromotive Force ◽  
Signal Frequency ◽  
Quick Response ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Flux Observer ◽  
Low Pass ◽  
Rotor Flux ◽  
Order Change

In order to solve the problem of integration saturation drift and hardship in compensation quantity calculation exist in rotor flux observation of induction motor, a rotor flux observer based on nonlinear quadrature double compensation method is presented in this paper. The quantity of compensation is determined dynamically according to the quadrature level between flux and back electromotive force. Through the order change of compensation and low-pass filter, quick response of flux when signal frequency leaps is realized. The simulation result shows that the method can improve the flux waveform, realize the accurate and swift track of flux.

DC-Bus Voltage Control Strategy Based on Low-Pass Filter for Three-Phase Four-Wire APF

2013 ◽  
Vol 732-733 ◽  
pp. 1167-1170
Author(s):  
Xia Feng ◽  
Xiao Jian Zhong ◽  
Qun Wei Xu ◽  
Guo Zhu Chen
Keyword(s):  
Voltage Control ◽  
Stable Operation ◽  
Voltage Control Strategy ◽  
Signal Model ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Three Phase ◽  
Low Pass ◽  
Dc Bus ◽  
Bus Voltage

The DC-bus voltage control is critical for stable operation of the three-phase four-wire Active Power Filter. DC-bus stable voltage loop and balance voltage loop are established based on the small signal model. Considering the disadvantages of the traditional PI control, second-order low-pass filter is introduced into the proposed controller. Simulation and experimental results are conducted to validate the effectiveness of the proposed strategy.

scholarly journals A Novel Sample Based Quadrature Phase Shift Keying Demodulator

2014 ◽  
Vol 2014 ◽  
pp. 1-7
Author(s):  
Asraf Mohamed Moubark ◽  
Sawal Hamid Md Ali
Keyword(s):  
Phase Noise ◽  
Signal To Noise Ratio ◽  
Local Oscillator ◽  
Coherent Detection ◽  
Signal Frequency ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Incoming Signal ◽  
Shift Keying ◽  
Low Pass

This paper presents a new practical QPSK receiver that uses digitized samples of incoming QPSK analog signal to determine the phase of the QPSK symbol. The proposed technique is more robust to phase noise and consumes up to 89.6% less power for signal detection in demodulation operation. On the contrary, the conventional QPSK demodulation process where it uses coherent detection technique requires the exact incoming signal frequency; thus, any variation in the frequency of the local oscillator or incoming signal will cause phase noise. A software simulation of the proposed design was successfully carried out using MATLAB Simulink software platform. In the conventional system, at least 10 dB signal to noise ratio (SNR) is required to achieve the bit error rate (BER) of 10−6, whereas, in the proposed technique, the same BER value can be achieved with only 5 dB SNR. Since some of the power consuming elements such as voltage control oscillator (VCO), mixer, and low pass filter (LPF) are no longer needed, the proposed QPSK demodulator will consume almost 68.8% to 99.6% less operational power compared to conventional QPSK demodulator.

scholarly journals Demodulation of Angular Position and Velocity from Resolver Signals via Chebyshev Filter-Based Type III Phase Locked Loop

Electronics ◽  
2018 ◽  
Vol 7 (12) ◽  
pp. 354 ◽  
Author(s):  
Huan Liu ◽  
Zhong Wu
Keyword(s):  
Angular Position ◽  
Frequency Measurement ◽  
Phase Locked Loop ◽  
Estimation Accuracy ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Type Iii ◽  
Low Pass ◽  
Chebyshev Filter ◽  
Demodulation Method

A high-accuracy demodulation algorithm is required to estimate angular position and angular velocity from resolver signals. In order to improve the estimation accuracy of conventional phase-locked loop (PLL) based demodulation method, a Chebyshev filter-based type III PLL method is proposed in this paper. The proposed method makes PLL become a system of type III tracking loop, which could greatly reduce the theoretical constant deviation in the estimation results of conventional type II PLL in case of variable speed. Meanwhile, the eigenvalues of type III PLL are placed to be the same position as those of a Chebyshev low-pass filter. In this way, demodulation parameters with stronger filter properties can be obtained to effectively suppress the high-frequency measurement noise in resolver signals. Thus, the proposed method can achieve higher demodulation precision compared with the conventional ones. Simulations and experiments are performed to validate the proposed demodulation method.

Design of Programmable Wideband Low Pass Filter with Continuous-Time/Discrete-Time Hybrid Architecture

2017 ◽  
Vol E100.C (10) ◽  
pp. 858-865 ◽  
Author(s):  
Yohei MORISHITA ◽  
Koichi MIZUNO ◽  
Junji SATO ◽  
Koji TAKINAMI ◽  
Kazuaki TAKAHASHI
Keyword(s):  
Discrete Time ◽  
Continuous Time ◽  
Hybrid Architecture ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Low Pass
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