Governor System Research Articles

Complexity and Multistability in the Centrifugal Flywheel Governor System With Stochastic Noise

In this paper, dynamics and complexity of the integer-order and fractional-order centrifugal flywheel governor systems are investigated numerically by the bifurcation diagram, Lyapunov exponents (LCEs), chaos diagram and spectral entropy (SE) algorithm separately. Moreover, the effect of periodic force and stochastic noise on the dynamics and complexity of the integer-order and fractional-order systems also are analyzed. Finally, the multistability of the system is discussed by coexisting attractors and the basins of attraction. The results show that the fractional-order system has rich dynamical behaviours. Stochastic noise has a great effect on dynamics and complexity of the integer-order and fractional-order systems. The high complexity region is determined and SE complexity can indicate different state of the system effectively. And the integer-order and fractional-order systems show multistability with the variation of initial conditions.

Design of various Automatic Control Topologies for Load Frequency Control of Six Area Hybrid Multi-Generation Power System

The automatic load frequency control of six unequal areas hybrid model consist of thermal, reheat thermal plants, hydraulic governor system, nuclear, diesel, gas turbine plants. These generating units are represented from area one to area six. If any disturbance occurs in load results to variation of frequency and tie-line. When the generating area doesn’t meet load unit gives abnormal limits in response. This can be solved by the implementation of Proportional integral controller(PI), Artificial Neural Network controller(ANN), Adaptive Neuro Fuzzy Inference System controller (ANFIS).But still there is a chance to achieve better responses can be done by the proposed Genetic Algorithm (GA) based PI controller. In the MAT LAB environment hybrid model is developed. The Step varying input is applied that will leads to creating the disturbances and controlled by applying controller respectively. The evaluation of responses will be carried out by the control strategies of frequency responses and tie-lie power responses in all six areas hybrid model system. This work gives the information about the dynamic responses achieved by GA controller is more efficient than that of existing controllers and evaluated by MATLAB Simulink results.

A Novel Frequency Support Control Method for PV Plants Using Tracking LQR

Growing level of Photovoltaic (PV) generation challenges the conventional generation control in power systems, as the current PV systems do not possess inertia or governor system. However, a supervisory control can be adopted for such PV systems to provide frequency support. In this article, a novel controller for large-scale PV plants is proposed for this purpose. Different than other approaches which only focus on emulating droop and inertial response of local PV, the proposed approach uses a tracking linear quadratic regulator (LQR) based controller to help the system frequency effectively track that of a designed reference system with given inertia and droop constants. To design the LQR, an unknown input observer (UIO) is adopted to estimate the system states, as well as the unknown disturbance. We also introduce a small-signal PV system model which is suitable for designing frequency support controls. The model is validated against the detailed nonlinear PV system model, and the effectiveness of the proposed controller is demonstrated using a standard test system. Test results also show that the proposed method achieves the desired frequency response more effectively than the alternative method from literature, while the later method is liable to over-compensation of frequency response at the price of requiring more power reserve in PV.

Investigation of hydro‐governor parameters’ impact on ULFO

The ultra-low-frequency oscillation (ULFO) problem reappears in China recently, but its specific mechanism is not so clear. Although the hydraulic governor system is confirmed as the source of ULFO, the parameters’ impacts are not studied thoroughly. This study investigates the specific impact of the important parameter of governing system in different control modes based on the complex coefficient torque method including the parameters of regulator, actuator and the turbine in hydraulic governing system. The damping torques under different situations are illustrated when parameters and control modes change, and the ultra-low-frequency-band dynamic characteristics of hydro generator are obtained. The simulations match well with the theoretical analysis, and the suggestions are made for parameter settings at last. The findings of this study are significant for ultra-LFO elimination. Moreover, it can also help designers and operator identify the most influential parameters and develop effective control strategies.

Multistability in the Centrifugal Governor System Under a Time-Delay Control Strategy

Abstract The centrifugal governor system plays an indispensable role in maintaining the near-constant speed of engines. Although different arrangements have been developed, the governor systems are still applied in many machines for its simple mechanical structure. Therefore, the large-amplitude vibrations of the governor system which can lead to the function failure of the system should be attenuated to guarantee reliable operation. This paper adopts a time-delay control strategy to suppress the undesirable large-amplitude motions in the centrifugal governor system, which can be regarded as the practical application of the delayed feedback controller in this system. The stability region of the trivial equilibrium of the controlled system is determined by investigating the characteristic equation and generic Hopf bifurcations. It is found that the dynamic behavior of multistability can be induced by the Bautin bifurcation, arising on the stability boundary of the trivial equilibrium with a constant delay. More specifically, a coexistence of two desirable stable motions, i.e., an equilibrium or a small-amplitude periodic motion, can be observed in the controlled centrifugal governor system without changing the physical parameters. This is a new feature of the motion control in the centrifugal governor systems, which has not yet been reported in the existing studies. Finally, the results of theoretical analyses are verified by numerical simulations.

Performance Analysis of Closed loop Control of Diesel generator power supply for Base Transceiver (BTS) Load

This paper describes closed loop control of Diesel Generator (DG) supplying power to a Base Transceiver (BTS) load of a telecommunication tower, which is DC in nature. Detail modeling of Diesel Generator set has been presented.. The stability analysis of governor and excitation system has been carried out in frequency domain. When DG source is connected to the BTS load bus through bridge rectifier, the output waveform distorted due to high odd harmonics content. To solve this problem a unity power factor rectifier has been designed. For the control operation of this UPFC rectifier, double loop mode control method has been used and results are presented. The complete system has been simulated in MATLAB-SIMULINK environment.

On the mechanism and control for the ultra-low frequency oscillation in NY Power Grid with large-scale hydropower

The power grid with large proportion of hydropower may engage the ultra-low frequency oscillation (ULFO), which threatening the operation of system. To the NY Power Grid system, whose dimension is over thousands, this paper reveals the cause of ULFO with the phase portrait method, i.e., lies in the saturation of the different limits of the governor system of the generators, in other words, the occurrence of limit cycle is due to the non-smooth bifurcation. And furthermore, it proposes two methods to suppress ULFO with the philosophy of destroying the condition of non-smooth bifurcation. In detail, first, the phenomenon of ULFO in NY Power Grid, the damping characteristics and the limits in the governor system of the hydropower units are presented. Second, based on the non-smooth bifurcation theory, the mathematical basis of the oscillation in the non-smooth system caused by the saturation of limits is introduced. And then, the non-oscillation and oscillation dynamic of the system corresponding to without/with limits in the governor system are analyzed. Furthermore, it discusses the influence of the saturation of single limit on the characteristics of ULFO with the phase portraits. Moreover, the phase portraits of the ULFO under different faults is analyzed, and it shows that the limiting saturation occurs with a large enough disturbance. Thus, the ULFO is resulting from the negative damping of generation and the saturation of multiple limits under a large enough disturbance. In addition, according to the above mechanism, two strategies to suppress the ULFO, i.e., the governor parameters tuning and the fault strength relief are designed. The simulation shows the effectiveness of proposed strategies.

Active control of variable geometry Francis Turbine

The governor is an important component of a hydro power plant. It actuates the guide vanes that regulate the water input to the turbine that controls the turbine power and speed. Laboratory studies have given important information about the model characteristics and performance. This work concerns laboratory studies with focus on the characteristics of the Francis turbine model. Appropriate representations of the hydraulic turbine, driven by a Francis turbine and conduit system were developed in various models of varying degrees of details. The laboratory model considered in this study is a test rig set in the Fluid Mechanics laboratory at Al-Azhar University, representing a Francis turbine hydro power plant model. Development and improvement of the measurements on the test rig have been done using sensors instead of manual parameters measurements. A simulation model for the Francis turbine is created by MATLAB simulation software. The governor system is modeled using PID controller. The dynamic response of governing system to load disturbances on the turbine is studied. In addition, different tuning designs for PID governor are studied. The comparison between linearized ideal and experimental model are presented. By applying MATLAB simulation, the result shows that the best output is obtained when the change in speed will stabilize and using the value of KP = 50, KI = 45 and KD = 10.

An Improved Low Frequency Oscillation Disturbance Source Localization Method in Control Devices of Generator

In this paper, an improved oscillation disturbance source localization method in control devices of generator is investigated. Using the dominant component of the electrical signals by the fast Fourier transform (FFT), the oscillation energy for governor system and excitation system is obtained separately. Then, based on the direction of the non-periodic component of the oscillation energy for the two systems, the control device level locating of the oscillation disturbance source is realized. Taking the forced power oscillation accident caused by too strong primary frequency modulation as an example, the oscillation energy based on FFT for the two systems show that the proposed method can locate the disturbance source accurately.

State‐space modelling of an interconnected system of renewable energy sources and grid for rural electrification

This study deals with the development of a state-space model for an interconnected system of renewable energy sources (RES) with grid. The RES technologies considered for power generation in the interconnected system are doubly fed induction generator (DFIG) based wind energy conversion system and biogas genset. A linearised model for DFIG has been developed for the system. For biogas genset, the control of frequency and voltage is taken care by the electronic speed governor and IEEE type-I excitation system, respectively. The interconnected system takes a fixed feed of power supply from the grid and the rest of the consumer load is taken care by the RES. Finally, state feedback controllers have been developed for this interconnected system which maintains the active and reactive power balance between different sources of RES when small signal perturbations are given in load and input wind power. The comparative analysis has also been performed with the conventional PI controllers in order to demonstrate the superiority of proposed feedback controllers for the interconnected power system.

Electric power frequency and nuclear safety - Subsynchronous resonance case study

Abstract The increase of the alternate current frequency results in increased rotational speed of the electrical motors and connected pumps. The consequence for the reactor coolant pumps is increased flow in primary coolant system. Increase of the current frequency can be initiated by the subsynchronous resonance phenomenon (SSR). This paper analyses the implications of the SSR and consequential increase of the frequency on the nuclear power plant safety. The Simulink MATLAB® model of the steam turbine and governor system and RELAP5 computer code of the pressurized water reactor are used in the analysis. The SSR results in fast increase of reactor coolant pumps speed and flow in the primary coolant system. The turbine trip value is reached in short time following SSR. The increase of flow of reactor coolant pumps results in increase of heat removal from reactor core. This results in positive reactivity insertion with reactor power increase of 0.5% before reactor trip is initiated by the turbine trip. The main parameters of the plant did not exceed the values of reactor trip set points. The pressure drop over reactor core is small discarding the possibility of core barrel lift.

A Method for the Evaluation of Generator Damping During Low-Frequency Oscillations

A new generator phasor measurement unit can provide a generator internal response during transient periods, thereby enabling online evaluation of generator damping in detail. In this paper, a method for the online detailed evaluation of the generator damping contribution during oscillation periods based on the damping loss factor (DLF) and multi-scale chirplet sparse signal decomposition (MCSSD) is proposed. First, the DLF in a simple elastic oscillation system, which can be used to quantitatively evaluate the damping characteristics of components, is introduced. After analyzing the feasibility of using the DLF during low-frequency oscillation, the generator damping loss factor (GDLF) is established to quantitatively evaluate the generator damping contribution, including the effects of the excitation system, governor system, and generator winding. Next, the modal composition of the generator dissipation energy is studied to extend the application of the GDLF to a multi-machine power system. Finally, a method for the online evaluation of generator damping during low-frequency oscillation based on the GDLF and MCSSD is presented. The proposed method is examined in detail using a single-machine infinite-bus system and then further demonstrated by applying it to a practical power system with multiple electromechanical oscillations.

A nonlinear load frequency controller for hydropower plants

ABSTRACT An efficient way to generate power is the key requirement for hydropower plants. One can improve the overall efficiency of hydropower plants by using advanced turbine models, appropriate design of tunnel and water storage areas, by designing efficient control systems, etc. The ultimate aim of the governor or control systems is to maintain the load frequency at the desired or reference value during the nominal as well as uncertain conditions. Most of the present hydraulic-electrical control systems for hydropower plants are based on linearised models; wherein tedious tuning process is required to achieve the desired response. Furthermore, the linear control design may not work for wide range of operating points. In this paper, we propose a nonlinear controller and observer scheme using State-Dependent Riccati Equation (SDRE) methodology for hydropower plant to achieve the desired frequency in nominal and uncertain conditions. The proposed SDRE scheme is directly based on nonlinear hydropower plant models, wherein linearisation is not required. The effectiveness of the proposed SDRE scheme is validated on a nonlinear hydropower plant model and is compared with the conventional controller in the presence of noises and parametric uncertainties.

UNIVERSAL CONTROLLER OF DIESEL ON THE BASIS OF ELECTRIC SERVO-ACTUATOR

An electronic actuator of a high-pressure fuel system for a transport diesel has been developed, the introduction of the actuator will allow to formulate optimum characteristics of a vehicle taking into account the conditions of its operation and co-ordination with any types of transmission and engine. The authors proposed a functional scheme and an algorithm for an electronic diesel actuator, based on the analogy with the operation of a mechanical spring-lever governor of direct action. The algorithm of the HEINZMANN actuator positioning control subsystem (servo-actuator) is developed. The algorithm is built on the parallel operation of the positional and proportional-differential-isodromic actuators. The motorless research of the high-pressure fuel pump BOSCH PES 4P 100A, equipped with an electric servo-actuator, showed that the electronic governor system developed by the authors can provide identical with a regular mechanical governor characteristics and could be easily adapted to the any necessary regulatory characteristics of the engine.

Parameters identification of reduced governor system model for diesel‐engine generator by using hybrid particle swarm optimisation

This study presents an approach to build a reduced-order model (ROM) for the governor control systems of diesel-engine generators in an island power system. The hybrid particle swarm optimisation (PSO) is used in the parameter identification of the ROM. The reduced-order governor system model could be a useful and feasible model in the stability analysis of the island power system by using power system simulator for engineering. The results of the ROM and a sixth-order model have been compared. It is found that the ROM with the parameter values identified using the hybrid PSO is robust. Moreover, real-case validation of the ROM shows that it is usable to analyse stability and contingency in the power system.

Generator Out-of-Step Prediction Based on Faster-Than-Real-Time Analysis: Concepts and Applications

This paper introduces a new approach, based on faster-than-real-time (FTRT) analysis, to predict out-of-step (OOS) condition of a turbine-generator (T-G) unit subsequent to a fault scenario. The proposed FTRT analysis is based on 1) solving a state-space model of the T-G electromechanical system and corresponding controllers without the need for online measurements, and 2) an estimated Thevenin equivalent of the rest of the power system. The measurement-free FTRT analysis is carried out after the Thevenin parameters are estimated subsequent to the fault clearance instant. Equal area criterion is applied on the predicated variables to detect OOS condition. A reliable decision can be made based on this approach, since it does not involve simplifying assumptions contrary to the existing approaches. The FTRT approach accurately considers the impacts of the detailed model of the generator, automatic voltage regulator, prime mover, governor system, and the host power system. This paper provides detailed mathematical formulation for the proposed OOS detection method and verifies its feasibility and accuracy based on single machine and large test systems. The proposed approach is also implemented on an industrial platform and evaluated. The results confirm that the proposed approach can accurately identify OOS conditions, earlier than the rotor angle noticeably increases.

Active–disturbance–rejection–control and fractional–order–proportional–integral–derivative hybrid control for hydroturbine speed governor system

A novel approach named active–disturbance–rejection–control (ADRC) and fractional–order–proportional–integral–derivative (FOPID) hybrid control scheme is proposed for hydroturbine speed governor system, which is based on ADRC and FOPID control methods. By combining the advantages of ADRC and FOPID controllers, the proposed ADRC–FOPID hybrid control scheme can actively reject the unpredictable disturbance, even with random noises, and can be adapted to the nonlinearities as well as unknown dynamics of hydroturbine speed governor system. The control performances of ADRC–FOPID, ADRC, FOPID as well as conventional proportional–integral–derivative (PID) controllers have been compared. And ADRC–FOPID has been proved to be an effective control scheme for hydroturbine speed governor system.

Nonlinear Modeling and Dynamic Analyses of the Hydro–Turbine Governing System in the Load Shedding Transient Regime

Load shedding processes are widespread in hydropower stations, which has great influence on the safe and stable operation of the hydro–turbine governing system. In order to study the dynamic characteristics of the hydro–turbine governing system during the load shedding process, a novel nonlinear mathematical model of the hydro–turbine governing system is established considering the hydro–turbine system, the generator system and the governor system. In particular, a novel nonlinear mathematical model of the six hydro–turbine transfer coefficients is presented based on the definitions and hydro–turbine internal characteristics. After that, from the viewpoint of nonlinear dynamics and the practical engineering, the dynamic characteristics of the hydro–turbine governing system are investigated utilizing bifurcation diagrams, time series, Poincare maps, power spectrums and phase planes. Some meaningful results are found. The advantages of the novel nonlinear mathematical model are illustrated and commented in detail in comparison with the previous model. Finally, these models and analysis results will provide some theoretical references for the operation of hydropower stations in the load shedding transient.

Fast discrete s-transform and extreme learning machine based approach to islanding detection in grid-connected distributed generation

This paper presents an approach for islanding detection in distributed generation systems (DGs) using fast discrete s-transform (FDST) algorithm and bidirectional extreme learning machine (BELM) classifier. The system undertaken for this study comprises of two different kinds of DGs such as hydro turbine governor system and wind turbine generator. The analysis starts with extracting the non-stationary negative sequence voltage and current signals at DG end and then the instantaneous amplitude and frequency information are extracted through FDST algorithm. From this information, different distinguishing features are computed such as energy and standard deviation of amplitude to track the islanded event from different non-islanded events. The obtained features are examined through an extreme learning machine classifier to discriminate islanding and non-islanding events, under various operating conditions of distribution system. The accuracy of the proposed method is compared with other recently published techniques by various researchers to justify its improved performance for islanding detection.

Hydraulic damping mechanism of low frequency oscillations in power systems: Quantitative analysis using a nonlinear model of hydropower plants

As power systems grow reliant on an increasing mix of intermittent renewables, hydropower units are being called upon to provide more aggressive power-frequency control. This dynamic is enlarging the significance of interaction between hydraulic and electrical subsystems in hydropower plants (HPPs). The influence from HPPs on power system stability is of great importance, especially for hydro-dominant power systems like the Nordic power system and the China Southern Power Grid. This paper aims to quantify and reveal the influencing mechanism of the hydraulic damping of low frequency oscillations in power systems. An equivalent hydraulic turbine damping coefficient is introduced, and a nonlinear HPP model that combines electrical subsystems with a refined hydraulic-mechanical subsystem is established and verified. A novel quantifying methodology is proposed through simulations by two different models based on case studies on a Swedish HPP. Then, the quantification results of the damping coefficient are presented and the influencing mechanism behind is revealed, by studying three representative factors from the hydraulic-mechanical system: the delay in turbine governor systems, governor parameter and penstock length. Observations and discussions of on-site measurements are included to support the analysis. The results show that the damping effect from hydraulic turbines can be considerable. Based on the limited cases in the HPP, the damping coefficient can vary from + 3.0 to −2.3, while previously the contribution has been unclear and normally assumed to be positive. The phase shift in the mechanical power response with respect to the rotational speed deviation is an important reason for the different damping performance. Furthermore, the effect and significance of implementing the damping coefficient on cases with power system stabilizer (PSS) are demonstrated.