Speed Governor Research Articles

Development of a Digital Model of the Egyptian Power Grid for Steady-State and Transient Studies

This paper presents the development of a digital model to simulate the Egyptian power grid at 500 kV and 220 kV levels. A professionally available DIgSILENT power system computation package is used. A brief description of the system is given, which includes generating units, transformers, transmission lines and loads. The system includes different types of power plants such as thermal, hydro, and wind. The automatic voltage regulator and speed governor of each unit are simulated in the model.The model is used to perform power system studies such as load flows, short circuit, contingencyand stabilityfor the purposes of performance evaluation and insuring compliance with the technical requirements of the Grid Code. The Performance Code of the Egyptian Grid Code is briefly described and used to evaluate the system performance at different operating scenarios, including steady state and transient analyses. Sample of the simulation results are presented to show the capabilities of the modelin various system studies.

Optimizing the AGC system of a three-unequal-area hydrothermal system based on evolutionary algorithms

This paper focuses on expanding and evaluating an automatic generation control (AGC) system of a hydrothermal system by modelling the appropriate generation rate constraints to operate practically in an economic manner. The hydro area is considered with an electric governor and the thermal area is modelled with a reheat turbine. Furthermore, the integral controllers and electric governor parameters are optimized using integral squared error (ISE) criterion. Also, a novel Teaching-Learning-Based Optimization (TLBO) algorithm, Particle Swarm Optimization (PSO), and Gravitational Search Algorithm (GSA) with controller are proposed for optimizing AGC. Investigations have been conducted for the selection of a suitable value for governor speed regulation parameter R for the hydro and thermal areas, to explore the effect of tie-line power on the dynamic response. The advantages of the proposed approach are demonstrated by comparing the results of optimizing the AGC system of a three-unequal-area hydrothermal system with mentioned algorithms for the first one in comparison with other recently published techniques. The results confirm the flexibility and the suitability of the proposed AGC model for optimizing the different approaches. Moreover, it is more practical to use the proposed method to make a wide variety of changes in the system parameters using sensitivity analysis.

A Novel Design of Decentralized LFC to Enhance Frequency Stability of Egypt Power System Including Wind Farms

This paper presents a real hybrid power system in Egypt, which includes both conventional generation units and Renewable Energy Sources (RESs) for studying the Load Frequency Control (LFC) problem. The conventional generation system in the Egyptian Power System (EPS) is decomposed into three dynamic subsystems; non-reheat, reheat and hydro power plants. Moreover, real wind speed data extracted from Zafarana location in Egypt is used for achieving a realistic wind power study. Each subsystem of the EPS has its own characteristics compared to the others. Moreover, the physical constraints of the governors and turbines such as Generation Rate Constraints (GRCs) of power plants and speed governor dead band (i.e., backlash) are taken into consideration. Therefore, this paper proposes a decentralized controller for each subsystem independently, to guarantee the stability of the overall closed-loop system. Hence, an optimal PID controller-based Particle Swarm Optimization (PSO) algorithm is proposed for every subsystem separately to regulate the frequency and track the load demands of the EPS. The performance of the proposed decentralized controller of each subsystem is compared to the centralized one under different operational scenarios. The EPS is tested using the nonlinear simulation by Matlab/SIMULINK. The obtained results reveal the superior robustness of the proposed decentralized controller against different load disturbance patterns, real wind power fluctuations and EPS uncertainties.

Coordinated Control Strategy of Distributed Energy Resources based Hybrid System for Rural Electrification

This paper proposes coordinated active and reactive power control strategy of wind-biogas based hybrid system for rural electrification (HSRE) in order to provide continuous and reliable source of electricity to a cluster of villages. In the control strategy used for HSRE, a predefined part of load is being supplied by the grid and the remaining part, under steady state as well as small signal disturbances, is taken care by a hybrid system of controllable and intermittent sources of energy. Induction generator (IG) based wind energy conversion system (WECS) has been considered as a source for HSRE. Since reactive power is needed by both IG and load, an additional source of reactive power, static synchronous compensator (STATCOM) is used to fulfill the reactive power requirement. The synchronous generator has been used for power generation from biogas-genset which is fitted with electronic speed governor and automatic voltage regulator (AVR). The concept of defined grid operation is achieved by considering dynamics of system voltage angle as well which cannot be achieved by the usual control techniques for frequency and voltage magnitude. The developed hybrid system is given a small signal disturbance in load as well as input wind power. The robustness of proposed control strategy has been showed from the dynamic performance results by maintaining power balance between system components while regulating the system voltage and frequency.

Two-area load frequency control with redox flow battery using intelligent algorithms in a restructured scenario

Load frequency control (LFC) is an essential aspect of power system dynamics. This paper focuses on the optimization of LFC for a two-area deregulated power system under different scenarios. A recent nature-inspired ower pollination algorithm (FPA), based on the pollination process of plants, is used to tune the proportional integral (PI) controller parameters of LFC for the global minima solution. FPA is compared with a genetic algorithm, particle swarm optimization, and a conventional PI controller. During large load disturbance in the areas, controllers are incapable of reducing frequency deviations and tie-line power oscillations due to the slow response of the speed governor mechanism. Hence, to improve the dynamic response of the LFC, redox ow batteries (RFBs) are added to both areas due to their quick response and lower time constant. The simulation results show the effectiveness of the RFBs and FPA, especially in terms of overshoots, undershoots, and settling time, thereby improving the performance of LFC in the deregulated power system. The simulation was carried out on the MATLAB/Simulink platform.

Diesel engine modeling based on recurrent neural networks for a hardware-in-the-loop simulation system of diesel generator sets

Abstract The electronic speed governors are widely used in diesel generator sets (DGS). To develop and debug electronic speed governor, the best option is to build a hardware-in-the-loop (HIL) simulation system. In the HIL simulation system, the physical diesel engine is replaced with its mathematical model for reducing the cost and producing less emissions. To meet the requirement of closing to the real environment, the performance of mathematical model representatives is very important. This paper presents a diesel engine modeling method based on recurrent neural networks (RNNs). This mathematical model is identified and estimated using the real data from one physical DGS. The experimental results showed that the proposed model accurately reproduced the diesel engine output characteristics with the changes of electrical power loads. To validate the proposed model, the simulation experiment was conducted on the established HIL simulation system. In the simulation experiment, the rack displacement and rotational speed were measured from the physical part of the HIL simulation system. The simulation result has been confirmed that the proposed model could well simulate the loading and unloading processes of the DGS.

A non-linear model based feed forward flatness control approach to speed governor systems of hydropower plants

A non-linear model based feed forward flatness control approach to speed governor systems of hydropower plants

Shipboard Power System Stabilizer Optimization Using GA and QPSO Algorithm

In order to improve shipboard power system dynamic stability, two bio-inspired algorithms, the genetic algorithm (GA) and quantum-behaved particle swarm optimization (QPSO), method are proposed for the shipboard power system stabilizer (PSS) optimization. The proposed PSS optimization method is inspired by a hybrid-coordinated stabilizer for diesel engine generator and the bio-inspired algorithm. The simulations are conducted under load change disturbance and short-circuit fault case for the marine generator with/without the diesel engine speed governor. Simulation results show that the quantum particle swarm optimize strategy could improve the dynamic performance of the marine generator better than the GA method. The dynamic performance for shipboard power system always indicates the effectiveness, feasibility and robustness of the proposed approach.

Discrete Data AGC of Hydrothermal Systems Under Varying Turbine Time Constants Along With the Power System Loading Conditions

The paper deals with the discrete data automatic generation control (AGC) of two area hydrothermal power system operating at different loading conditions. The power system load varies considerably throughout the day and accordingly, thermal and hydropower systems are scheduled to operate at different loading conditions. It is found that steam as well as hydro turbine time constants vary as the power system loading varies. In earlier AGC studies, these parameters are considered to be constant, irrespective of power system loadings. This paper studies the dynamic performance of hydrothermal power system considering the variation of these turbine time constants along with the nominal loading of power system. The studies have been conducted for linear as well as nonlinear models of speed governor and hydroturbine models recommended by the IEEE committee. It is also discovered that conventional empirical formula-based hydraulic governor settings recommended by the IEEE working group are completely unacceptable for hydrothermal power system. A maiden attempt is made to optimize the hydraulic governor settings simultaneously along with the controller gains using metaheuristic algorithm. The comparison of system dynamic responses reveal that optimization-based hydrogovernor settings give the better dynamic performance in case of linear as well as nonlinear models of hydro system, and therefore are strongly recommended over the conventional settings. The paper also deals with the optimum selection of sampling periods for discrete data AGC operation of hydrothermal systems.

Accurate modelling of discrete AGC controllers for interconnected power systems

This paper deals with the modeling of discrete automatic gain control (AGC) controllers for an interconnected power system. The AGC supplementary controllers continuously try to reduce the ACE signal to zero by sending control commands/signals to the speed governor set points. Typically, control signals are sent in the form of discrete control pulses to adjust the generating unit outputs in discrete steps. However, in the preceding AGC studies, ZOH circuit has been misplaced in discrete supplementary controller models. Therefore, control signals feed to the speed governor set points no longer remains in discrete mode or in other words, controller action no longer remains in discrete steps. Therefore, the results and inferences drawn in these studies are erroneous and unrealistic. This paper presents the realistic model of discrete AGC controllers and removes the anomaly in existing works. Furthermore, it is also discovered that inappropriate selection of sampling period of ACE signal degrades the system dynamic performance or even cause system instability. Surprisingly, no proper guidelines/method has been provided yet to select the appropriate sampling period of ACE signals for discrete AGC operation. Here, a maiden attempt has been made to obtain the suitable values of ACE signal&s sampling periods using Shannon&s sampling theorem.

Discrete sliding mode variable structure control over the rotating speed of marine diesel engines

This article presents a discrete sliding mode variable structure control used for the speed governing system of marine diesel engines. It is widely accepted that the steady operation of marine diesel engines plays an important role in ensuring the power quality of marine electronic system and good engine performance. In other words, it means that a speed governor with excellent performance is crucial to ensuring the steady rotating speed of a diesel engine. However, due to the fact that diesel engine normally has a complex structure and is often influenced by multiple and nonlinear factors, a traditional proportional integral differential controller cannot optimize the sailing parameters of ships, making it difficult to satisfy the requirements of the speed control for diesel engines under various operation conditions. In view of this problem, this article developed a nonlinear mathematical model of the speed governing system for diesel engines based on experimental tests. Moreover, a discrete sliding mode controller was designed by applying the discrete sliding mode variable structure control, and a simulation model was then developed under the Simulink environment, illustrating that the performance of the designed sliding mode controller is much better than a traditional proportional integral differential controller. Finally, a bench test used for the nonlinear speed governing system based on the discrete sliding mode variable structure control approach was carried out using the bench of a diesel engine Model 2135. The experimental results further illustrated that the discrete sliding mode variable structure controller showed some super advantages, such as smaller overshoot and error, faster response and stronger anti-jamming capability, when comparing with the traditional proportional integral differential controller.

Research and Improvement of the High-speed Elevator Over-speed Governor

This paper focuses on the issues that the action speed of the traditional mechanical over-speed governor could not follow the speed of the car and the over-speed governor action speed is not precise, which are significant in the elevator safety and the whole cost of elevator. A new governor called mechanical-electronic over-speed governor without altering the original mechanical governor had been present to improve the performance of mechanical governor. The structure, control part and the principle of the mechanical-electronic governor had been given in this article. Based on the design of the mechanical-electronic governor, data analysis interrelated have been given. The result shows that this design could significantly increase the safety performance of high-speed elevator, and has important reference value in the elevator design. Mechanical-electronic over-speed governor has great significance not only for the safety of elevator but also for shortening distance of pit and overhead. Using this method, lower speed governor and shorter distance of pit and overhead could be chosen for high-speed elevator to improve the elevator safety and reduce the whole cost.

Load Frequency Control of Nonlinear Power System Employing Firefly Algorithm

Background/Objectives: Firefly Algorithm (FA) is employed to for Load Frequency Control (LFC) of nonlinear power system. Methods/Statistical Analysis: The supremacy of FA technique is established by comparing the outcomes with Genetic Algorithm (GA). Findings: Additionally, sensitivity study is conducted by changing system parameters like time constants of turbine, speed governor and inertia constant as well as generator initial loading condition by +50% to -50% from their normal values in addition to the magnitude and location of load disturbance to illustrate the effectiveness of the suggested design approach. Application/Improvements: A nonlinear three area thermal system is taken as the system under study and the parameters of the LFC controller are tuned using FA technique.

Assessing the Operation of the Cooling Water System of a Hydro-Power Plant Using EPANET

This paper focuses on the Cooling Water System (CWS) of Vidraru Hydro-Power Plant (HPP) − a 220 MW underground HPP, on the Arges River in Romania. It is equipped with 4 high head vertical Francis turbines of 55 MW each, 4 hydropower generators of 61 MVA each, and 7 step-up transformers of 40 MVA each. The goal is to model the above CWS and to analyse the system response under normal and critical operating scenarios. The numerical model built in EPANET is complex: the cooling water network is normally fed by pumping from the underground tailrace (using up to 3 pumps of 110kW each), but there is a backup supplying circuit fed directly from the penstock bifurcation pipe (using pressure reducing valves). Within the power plant, the following equipments need cooling water: air-water heat exchangers (related to generators and HVAC system); oil-water heat exchangers (related to bearings, speed governors and transformers); coolers of the turbines seals. Since EPANET lacks such physical components, they are artificially replaced by throttle control valves set with equivalent loss coefficients, established upon pressure drop values available for each equipment. The computed flow rate and pressure values match the existing recordings for normal operation. The numerical model also provides data on the system behaviour under critical operation conditions, e.g. when the HPP is operating at full capacity with CWS fed only by 2 pumps, out of 3 available pumps.

Load Performances of a PIC Based Speed Governor for Micro Hydro Power Plant

Load Performances of a PIC Based Speed Governor for Micro Hydro Power Plant

Hybridized gravitational search algorithm tuned sliding mode controller design for load frequency control system with doubly fed induction generator wind turbine

SummaryIn this paper, the load frequency regulation problem of 2‐area interconnected power system is resolved using the sliding mode control (SMC) methodology. Interconnected 2‐area power systems with and without doubly fed induction generator wind turbines are considered for implementing the proposed optimal control methodology. Here, a heuristic gravitational search algorithm (GSA) and its variants such as opposition learning–based GSA (OGSA), disruption‐based GSA (DGSA), and disruption based oppositional GSA (DOGSA) are employed to optimize the switching vector and feedback gains of SMC. In order to overcome the inherent chattering problem in SMC, the control signals are considered in the objective function. The robustness of optimized SMC is analyzed by the inclusion of nonlinearities such as generation rate constraint (GRC), governor deadband, and time delay during the signal processing between the control areas, which are present in the real‐time power system. The insensitiveness of the optimal controller is shown by variation in system parameters like loading condition, speed governor constant, turbine constant, and tie‐line power coefficient. Further, the optimal SMC has been studied with significant load variations and wind power penetration levels in the control areas. The potential of proposed SMC design with chattering reduction feature is shown and validated by comparing the results obtained with the other reported methods in the literature.

Study of Integrated Rural Electrification System Using Wind-Biogas Based Hybrid System and Limited Grid Supply System

This paper presents modeling of system having wind-biogas based hybrid system operating in parallel with limited grid supply system to meet the rural demand, of a cluster of villages continuously. In this integrated rural electrification system (IRES), a fixed part of the power is supplied by the grid and the remaining power, required by the load under steady state and also the variations, is taken care by a hybrid renewable energy system (HRES). The wind energy converting system (WECS) uses a permanent magnet synchronous generator (PMSG) and synchronized in the hybrid system through a voltage source converter (VSC). The other source considered in the hybrid system is biogas-genset equipped with electronic speed governor and synchronous generator (SG) with automatic voltage regulator (AVR). The variation in load and/or input wind power to WECS may cause deviation in frequency and voltage and to maintain these parameters at nominal values, the power generated by biogas-genset is controlled, through governor control. The basic control schemes for frequency and magnitude of system voltage may not ensure limited grid operation. Therefore the system model is unique as it considers the dynamics and control of system voltage angle also. The main contribution of this paper is the system dynamic model development and its performance study. Proportional integral (PI) controllers are used in the model and their values are optimized using integral square error (ISE) criteria. Finally, the system simulation results have been shown for step deviations in load and/or input wind power to the WECS.

Shear Resistance Properties of Modified Nano-SiO2/AA/AM Copolymer Oil Displacement Agent

To address the problem regarding poor shear resistance of commonly employed polymers for oil displacement, modified nano-SiO2/AA/AM copolymer (HPMNS) oil displacement agents were synthesized using acrylic acid (AA), acrylamide (AM), and modified nano-SiO2 of different modification degrees as raw materials. HPMNS was characterized by means of infrared spectroscopy (IR), nuclear magnetic resonance (1H-NMR, 13C-NMR), dynamic/static light scattering, and scanning electron microscope. A comparative study of the shear resistance properties for partially hydrolyzed polyacrylamide (HPAM) and HPMNS was conducted. Compared to HPAM, the introduced hyperbranched structure endowed HPMNS with good shear resistance, which was quantified from the viscosity retention ratio of the polymer solutions. From the perspective of rheological property, HPMNS also showed great shear stability after shearing by a Mixing Speed Governor and porous media shear model. Furthermore, with a higher degree of modification, HPMNS-2 had better shear stability in terms of viscosity and rheological property than HPMNS-1. The phenomena were due to its lower hydrodynamic radius, weight-average molecular weight, and better flexibility of its molecular chains. In addition, upon the indoor displacement test, the resistance factor and residual resistance factor values of HPMNS-2 were higher than those of HPAM. This behavior is beneficial for increasing oil recovery.

The Dynamic Analysis of Hydropower House and Unit System in Coupled Hydraulic-mechanical-electric Factors

A hydraulic-mechanical-electric and structures coupled model of hydropower station system including subsystem models of the penstock, hydro-turbine model, speed governor, synchronous generator as well as grid, rotor-bearing system and powerhouse structure is established. This model is used to simulate the small fluctuation transient process of 10% load-up in the part load condition for hydropower station. Mechanical eccentric force, unbalanced magnetic pull and vortex pressure fluctuation at inlet of draft tube are considered in the numerical calculation. The interaction between hydraulic-mechanical-electric coupled factors and structural vibration properties during the small fluctuation transient process is studied. The results indicate that the speed regulation for turbine has very litter impact on the transient process of generator. In the process of small fluctuation with loading method in this paper, structure of powerhouse is greatly influenced by vortex pressure pulse in the draft tube, and the vibration of unit is excited by loads which caused by itself rotating.

A model establishment and numerical simulation of dynamic coupled hydraulic–mechanical–electric–structural system for hydropower station

A nonlinear dynamic coupled model for hydropower station system, which contains the model of water-carriage system, water turbine system, speed governor system, generator’s electromagnetic system, grid, shaft system of hydroelectric generating set, as well as the powerhouse, is established in this paper. Firstly, the simultaneous differential equations for coupled hydraulic–mechanical–electric transient process are set up based upon the theories of hydraulics, electrical machinery, etc., while the coupled structural models for shaft system of unit and powerhouse are built by means of finite element method. Secondly, a new method for investigating nonlinear dynamic properties of structures influenced by coupled hydraulic–mechanical–electric factors in different conditions is introduced with the help of user-programmable features from Ansys software. Finally, in order to verify the rationality, several numerical calculation methods are used to study the starting-up process of hydropower station. The results indicate that the model presented in this paper is adoptable for simulating specified condition and reflect the nonlinear dynamic characteristics of hydropower station comprehensively. In addition, the model can also be used to assess the operation safety and predict the structures reliability of hydropower station system, so as to provide some profitable reference for dynamic regulation during limited and transient conditions for hydropower station.