A frequency servo SoC with output power stabilization loop technology for miniaturized atomic clocks

A frequency servo system-on-chip(FS-SoC)featuring output power stabilization technology is introduced in this study for high-precision and miniaturized cesium(Cs)atomic clocks.The proposed power stabilization loop(PSL)technique,incorporating an off-chip power detector(PD),ensures that the output power of the FS-SoC remains stable,mitigating the impact of power fluctuations on the atomic clock's stability.Additionally,a one-pulse-per-second(1PPS)is employed to syn-chronize the clock with GPS.Fabricated using 65 nm CMOS technology,the measured phase noise of the FS-SoC stands at-69.5 dBc/Hz@100 Hz offset and-83.9 dBc/Hz@1 kHz offset,accompanied by a power dissipation of 19.7 mW.The Cs atomic clock employing the proposed FS-SoC and PSL obtains an Allan deviation of 1.7×10^(-11) with 1-s averaging time.

Power system stabilizer design using hybrid multi-objective particle swarm optimization with chaos

A novel technique for the optimal tuning of power system stabilizer (PSS) was proposed,by integrating the modified particle swarm optimization (MPSO) with the chaos (MPSOC).Firstly,a modification in the particle swarm optimization (PSO) was made by introducing passive congregation (PC).It helps each swarm member in receiving a multitude of information from other members and thus decreases the possibility of a failed attempt at detection or a meaningless search.Secondly,the MPSO and chaos were hybridized (MPSOC) to improve the global searching capability and prevent the premature convergence due to local minima.The robustness of the proposed PSS tuning technique was verified on a multi-machine power system under different operating conditions.The performance of the proposed MPSOC was compared to the MPSO,PSO and GA through eigenvalue analysis,nonlinear time-domain simulation and statistical tests.Eigenvalue analysis shows acceptable damping of the low-frequency modes and time domain simulations also show that the oscillations of synchronous machines can be rapidly damped for power systems with the proposed PSSs.The results show that the presented algorithm has a faster convergence rate with higher degree of accuracy than the GA,PSO and MPSO.

Optimal and Robust Power System Stabilizers in a Multi Machine System

One method for eliminating oscillations in power systems is using stabilizers.By applying an appropriate control signal in the excitation system of a generator,a power system stabilizer improves the dynamic stability of power systems.However,the issue that is of high importance is the correct design of these stabilizers.These stabilizers must be designed to have proper performance when operating conditions change.When designed incorrectly,not only they do not improve the stability margin,but also increase the oscillations.In this paper,the robust design of power system stabilizers on a four-machine power system has been performed.For this purpose,the differential evolution algorithm has been used.The studies have been repeated as three scenarios by producing different loading conditions for the generators.The performances of the conventional stabilizer and the optimized one have been compared.Simulation results indicate that the designed robust stabilizer outperforms other stabilizers in different conditions and has damped the interarea and intra-area oscillation modes in the shortest time with minimum amplitude.

An Improved Immune Clone Selection Algorithm for Parameters Optimization of Marine Electric Power System Stabilizer

In themarine electric power system,the marine generators will be disturbed by the large change of loads or the fault of the power system.The marine generators usually installed power system stabilizers to damp power system oscillations through the excitation control.This paper proposes a novel method to obtain optimal parameter values for Power System Stabilizer(PSS)to suppress low-frequency oscillations in the marine electric power system.In this paper,a newly developed immune clone selection algorithm was improved from the three aspects of the adaptive incentive degree,vaccination,and adaptive mutation strategies.Firstly,the typical PSS implementation type of leader-lag structure was adopted and the objective function was set in the optimization process.The performance of PSS tuned by improved immune clone selection algorithm was compared with PSS tuned by basic immune clone selection algorithm(ICSA)under various operating conditions and disturbances.Then,an improved immune clone selection algorithm(IICSA)optimization technique was implemented on two test systems for test purposes.Based on the simulations,it is found that an improved immune clone selection algorithm demonstrates superiority over the basic immune clone selection algorithm in getting a smaller number of iterations and fast convergence rates to achieve the optimal parameters of the power system stabilizers.Moreover,the proposed approach improves the stability and dynamic performance under various loads conditions and disturbances of the marine electric power system.

Suppression of laser power error in a miniaturized atomic co-magnetometer based on split ratio optimization

A miniaturized atomic spin-exchange relaxation-free(SERF)co-magnetometer measures angular velocity using a balanced polarimetry technique which is easily affected by the laser power.A laser power closed-loop control system is usually used to suppress the fluctuation of the laser power.Although this method can greatly eliminate the fluctuation of the in-loop laser power(the feedback laser),it cannot fully eliminate the fluctuation of the out-of-loop laser power(the signal measurement laser).This leads to SERF gyroscope laser power error,which reduces the inertial measurement accuracy.In this paper,the influence mechanism of the split ratio(the ratio of the in-loop laser power to the out-of-loop laser power)on the out-of-loop laser power control accuracy is analyzed by establishing a laser power transmission model inside and outside the loop.Moreover,a method is developed to improve the out-of-loop laser power stability by optimizing the split ratio.Comparative experiments showed that the relative Allan standard deviation of the out-of-loop laser power decreased from 5.48×10^(-6)to 2.62×10^(-6)at 100 s,and decreased by an order of magnitude from 1.76×10^(-5)to 3.30×10^(-6)at1000 s.Correspondingly,the rate ramp coefficient in the Allan standard deviation curve of the SERF gyroscope test data decreased from 1.312[(°/h)/h]to 0.246[(°/h)/h].And the bias stability increased from 0.032°/h to 0.019°/h.Therefore,the proposed method can improve the long-term stability of the probe laser power and effectively suppress the laser power error of the SERF gyroscope.

IC Pattern Based Power Factor Maximization Model for Improved Power Stabilization

The voltagefluctuation in electric circuits has been identified as key issue in different electric systems.As the usage of electricity growing in rapid way,there exist higherfluctuations in powerflow.To maintain theflow or stabi-lity of power in any electric circuit,there are many circuit models are discussed in literature.However,they suffer to maintain the output voltage and not capable of maintaining power stability.To improve the performance in power stabilization,an efficient IC pattern based power factor maximization model(ICPFMM)in this article.The model is focused on improving the power stability with the use of IC(Inductor and Conductor)towards identifying most efficient circuit for the current duty cycle according to the input voltage,voltage in capacitor and output voltage required.The model with boost converter diverts the incoming voltage through number of conductors and inductors.By triggering specific inductor,a specific capacitor gets charged and a particular circuit gets on.The model maintains num-ber of IC(Inductor and Conductor)patterns through which the powerflow occurs.According to that,the pattern available,the mofset controls the level of power to be regulated through any circuit.From the pattern,the model computes the Cir-cuits Switching Loss and Circuits Conduction Loss for various circuits.Accord-ing to the input voltage,the model estimates Circuit Power Stabilization Support(CPSS)according to the voltage available in any capacitor and input voltage.Using the value of CPSS,the model trigger optimal number of circuits to maintain voltage stability.In this approach,more than one circuit has been triggered to maintain output voltage and to get charged.The proposed model not only main-tains power stability but also reduces the wastage in voltage which is not utilized.The proposed model improves the performance in voltage stability with less switching loss.

Multimachine Power System Stabilizer based on Optimal Fuzzy PID with Genetic Algorithm Tuning

This paper presented PSS （Power system stabilizer） design based on Genetic Algorithm - Fuzzy PID （Proportional Integral and derivative） or GAFPID. GAFPID based PSS design is considered for multimachine power system. The main motivation for this design is to stabilize or to control low-fi＇equency oscillation and terminal voltage of power systems. Genetic Algorithm （GA） is employed for the optimization of the parameter of stabilizer. By minimizing an objective function in which the oscillatory speed deviation of the generator, small signal and large signal performance of the system is improved. The effectiveness of the proposed PSS in increasing the damping of system electromechanical oscillation is demonstrated in a simple two-area power system.

Most Suitable Power System Stabilizer Selection for the Improvement of Dynamic Stability

A method of enhancing power system stability for a single machine to infinite bus power system is presented. The technique used compromises the effectiveness of Proportional-Integral-Derivative controller （PID）. In order to satisfy the damping characteristics for the proposed power system over a wide range of operating interval, rotational speed, torque angle and terminal voltage signals of the synchronous machine are utilized as control signals of the system. It is well known that these variables have significant effects on damping the generators shaft mechanical oscillations, it＇ll be so easy to validate the most suitable controller as seen from the simulation results.

Coordinated Design of Thyristors Controlled Braking Resistors and Power System Stabilizer for Damping

This paper presents a new concept for damping electro-mechanical oscillations in large turbo generator. The proposed concept is based on coordination between Power System Stabilizer （PSS） and Thyristor Controlled Braking Resistor （TCBR）. This coordination will enhance the stability of the inertial and torsional oscillatory modes. The study is performed on system-I of the second IEEE benchmark for simulation of Sub-Synchronous Oscillations, using eigenvalue analysis and verified by detailed digital simulation. A dynamic fundamental frequency model for TCBR is developed. The pole placement technique is used to design the control system of TCBR and PSS. The shaft torque＇s following a disturbance is computed and analyzed. The obtained results indicate that substantial damping is achieved by the proposed coordination.

Impact of interconnections and renewable energy integration on the Philippine-Sabah Power Grid systems

This study presents a comprehensive impact analysis of the rotor angle stability of a proposed international connection between the Philippines and Sabah,Malaysia,as part of the Association of Southeast Asian Nations(ASEAN)Power Grid.This study focuses on modeling and evaluating the dynamic performance of the interconnected system,considering the high penetration of renewable sources.Power flow,small signal stability,and transient stability analyses were conducted to assess the ability of the proposed linked power system models to withstand small and large disturbances,utilizing the Power Systems Analysis Toolbox(PSAT)software in MATLAB.All components used in the model are documented in the PSAT library.Currently,there is a lack of publicly available studies regarding the implementation of this specific system.Additionally,the study investigates the behavior of a system with a high penetration of renewable energy sources.Based on the findings,this study concludes that a system is generally stable when interconnection is realized,given its appropriate location and dynamic component parameters.Furthermore,the critical eigenvalues of the system also exhibited improvement as the renewable energy sources were augmented.

Design of Power System Stabilizer for DFIG-based Wind Energy Integrated Power Systems Under Combined Influence of PLL and Virtual Inertia Controller

Wind energy systems (WESs) based on doubly-fed induction generators (DFIGs) have enormous potential for meeting the future demands related to clean energy. Due to the low inertia and intermittency of power injection, a WES is equipped with a virtual inertial controller (VIC) to support the system during a frequency deviation event. The frequency deviation measured by a phase locked loop (PLL) installed on a point of common coupling (PCC) bus is the input signal to the VIC. However, a VIC with an improper inertial gain could deteriorate the damping of the power system, which may lead to instability. To address this issue, a mathematical formulation for calculating the synchronizing and damping torque coefficients of a WES-integrated single-machine infinite bus (SMIB) system while considering PLL and VIC dynamics is proposed in this paper. In addition, a power system stabilizer (PSS) is designed for wind energy integrated power systems to enhance electromechanical oscillation damping. A small-signal stability assessment is performed using the infinite bus connected to a synchronous generator of higher-order dynamics integrated with a VIC-equipped WES. Finally, the performance and robustness of the proposed PSS is demonstrated through time-domain simulation in SMIB and nine-bus test systems integrated with WES under several case studies.

A novel stabilization approach for small signal disturbance of power system with time-varying delay

Small signal instability may cause severe accidents for power system if it can not be dear correctly and timely. How to maintain power system stable under small signal disturbance is a big challenge for power system operators and dispatchers. Time delay existing in signal transmission process makes the problem more complex. Conventional eigenvalue analysis method neglects time delay influence and can not precisely describe power system dynamic behaviors. In this work, a modified small signal stability model considering time varying delay influence was constructed and a new time delay controller was proposed to stabilize power system under disturbance. By Lyapunov-Krasovskii function, the control law in the form of nonlinear matrix inequality （NLMI） was derived. Considering synthesis method limitation for time delay controller at present, both parameter adjustment method by using linear matrix inequality （LMI） solver and iteration searching method by solving nonlinear minimization problem were suggested to design the controller. Simulation tests were carried out on synchronous-machine infinite-bus power system. Satisfactory test results verify the correctness of the proposed model and the feasibility of the stabilization approach.

A multi-objective gravitational search algorithm based approach of power system stability enhancement with UPFC

On the basis of the theoretical analysis of a single-machine infinite-bus （SMIB）, using the modified linearized Phil- lips-Heffron model installed with unified power flow controller （UPFC）, the potential of the UPFC supplementary controller to enhance the dynamic stability of a power system is evaluated by measuring the electromechanical controllability through singular value decomposition （SVD） analysis. This controller is tuned to simultaneously shift the undamped electromeehanical modes to a prescribed zone in the s-plane. The problem of robust UPFC based damping controller is formulated as an optimization problem according to the eigenvalue-based multi-objective function comprising the damping factor, and the damping ratio of the undamped electromechanical modes to be solved using gravitational search algorithm （GSA） that has a strong ability to find the most optimistic results. The different loading conditions are simulated on a SMIB system and the rotor speed deviation, internal voltage deviation, DC voltage deviation and electrical power deviation responses are studied with the effect of this flexible AC transmission systems （FACTS） controller. The results reveal that the tuned GSA based UPFC controller using the proposed multi-objective function has an excellent capability in damping power system with low frequency oscillations and greatly enhances the dynamic stability of the power systems.

Lyapunov-Krasovskii functional based power system stability analysis in environment of WAMS

In order to analyze power system stability in environment of WAMS(wide area measurement system),a new steady state stability model with time-varying delay was proposed for power system.The factors of exciter and power system stabilizer with delay were introduced into analytical model.To decrease conservativeness of stability analysis,an improved Lyapunov-Krasovskii functional was constructed,and then a new delay-dependent steady state stability criterion for power system,which overcomes the disadvantages of eigenvalue computation method,was derived.The proposed model and criterion were tested on synchronous-machine infinite-bus power system.The test results demonstrate that Lyapunov-Krasovskii functional based power system stability analysis method is applicable and effective in the analysis of time delay power system stability.

Study on the measureto improve the arcstabilization in smaller current welding for the variable polarity GTAW powersource

The variable polarity power source which incorporates a constant current power and a secondary inverter does not need special apparatus for stabilizing arc. The pulse for stabilizing arc is created by the circuit structure itself. The paper analyzes the principle of acquiring the pulse, provides the better method to improve the arc stabilization under smaller welding current. Test shows the arc is highly stable , and the process has no high frequency electromagnetic interference, which is suitable for automatic welding case.

Complex Dynamics Caused by Torus Bifurcation in Power Systems

Torus bifurcation is a relatively complicated bifurcation caused by a pair of complex conjugate Floquet multipliers coming out of unit circle on the Poincare section. A three-bus system is employed to reveal the relationship between torus bifurcation and some complex dynamics. Based on theoretical analysis and simulation studies, it is found that torus bifurcation is a typical route to chaos in power system. Some complex dynamics usually occur after a torus bifurcation, such as self-organization, deep bifurcations, exquisite structure, coexistence of chaos and divergence. It is also found that chaos has close relationship with various instability scenarios of power systems. Studies of this paper are helpful to understand the mechanism of torus bifurcation in power system and relationship of chaos and power system instabilities.

An Advanced FMRL Controller for FACTS Devices to Enhance Dynamic Performance of Power Systems

The parameters of power system slowly change with time due to environmental effects or may change rapidly due to faults. It is preferable that the control technique in this system possesses robustness for various fault conditions and disturbances. The used flexible alternating current transmission system （FACTS） in this paper is an advanced super-conducting magnetic energy storage （ASMES）. Many control techniques that use ASMES to improve power system stability have been proposed. While fuzzy controller has proven its value in some applications, the researches applying fuzzy controller with ASMES have been actively reported. However, it is sometimes very difficult to specify the rule base for some plants, when the parameters change. To solve this problem, a fuzzy model reference learning controller （FMRLC） is proposed in this paper, which investigates multi-input multi-output FMRLC for time-variant nonlinear system. This control method provides the motivation for adaptive fuzzy control, where the focus is on the automatic online synthesis and tuning of fuzzy controller parameters （i.e., using online data to continually learn the fuzzy controller that will ensure that the performance objectives are met）. Simulation results show that the proposed robust controller is able to work with nonlinear and nonstationary power system （i.e., single machine-infinite bus （SMIB） system）, under various fault conditions and disturbances.

Automatic Voltage Regulator Test of Three Gorges Right Bank Hydropower Station

Based on real-time digital simulations(RTDS),a laboratory environment similar to the real-time operation situation of the Three Gorges Hydropower Station is established.Then,the causes for the power fluctuation of the second generator by errors in the rotor rotating speed calculation are found,and the tuning method of the speed related parameters are given.The damping and reverse tuning characteristics of power system stabilizers(PSSs)in the digital automatic voltage regulator(AVR)are compared and investigated in the frequency range of 0.18-1.1 Hz.The efficiency of the proposed tuning method for ensuring power system stability is verified by RTDS.Finally,field tests show the validity of the laboratory test results.

Improving Dynamic Stability of Yunnan Provincial and South China Power System by PSS

For solving the dynamic instability problem of Yunnan Provincial Power System (YNPS) and the South China Interconnected Power System (SCIPS), Lubuge Hydropower Station was chosen to install Power System Stabilizer (PSS). This paper introduces the principles and methods of parameter selection for PSS, in addition to field test. The test results show that the PSS installed can significantly improve the system damping.

Three Routes to Chaos in Electrical Power Systems

Routes to chaos in power systems are studied. Using a three-bus simple system, three routes that can lead power system to chaos are presented, illustrated and discussed. They are cascading period doubling bifurcation, torus bifurcation and route directly initiated by a large disturbance. Period doubling bifurcation is caused by a real Floquet multiplier going out of the unit circle from point (-1,0), while torus bifurcation is caused by a couple of conjugated Floquet multipliers going out of the unit circle with a non-zero imaginary part in the complex plane. Cascading period doubling bifurcation and torus bifurcation are two typical routes to chaos in dynamic systems, which have been investigated in the previous studies. The last route, i.e. directly initiated by a large disturbance, is reported and studied. This phenomenon reveals that chaos is caused by external disturbances in power systems.