scholarly journals Optimal linear quadratic Gaussian control based frequency regulation with communication delays in power system

Author(s):  
Hoan Bao Lai ◽  
Anh-Tuan Tran ◽  
Van Huynh ◽  
Emmanuel Nduka Amaefule ◽  
Phong Thanh Tran ◽  
...  

<p>In this paper, load frequency regulator based on linear quadratic Gaussian (LQG) is designed for the MAPS with communication delays. The communication delay is considered to denote the small time delay in a local control area of a wide-area power system. The system is modeled in the state space with inclusion of the delay state matrix parameters. Since some state variables are difficult to measure in a real modern multi-area power system, Kalman filter is used to estimate the unmeasured variables. In addition, the controller with the optimal feedback gain reduces the frequency spikes to zero and keeps the system stable. Lyapunov function based on the LMI technique is used to re-assure the asymptotically stability and the convergence of the estimator error. The designed LQG is simulated in a two area connected power network with considerable time delay. The result from the simulations indicates that the controller performed with expectation in terms of damping the frequency fluctuations and area control errors. It also solved the limitation of other controllers which need to measure all the system state variables.</p>

Author(s):  
Barjeev Tyagi ◽  
S.C. Srivastava

This paper presents the design of a Linear Quadratic Gaussian (LQG) regulator for the frequency control of a multi-area power system in a restructured competitive electricity market environment. A general model of the LQG regulator has been developed for multi-area system (with hydro and thermal generators) having Poolco and bilateral transactions. To account for the modeling uncertainties and non-measurable states, a Kalman filter has been designed to estimate the state variables. The controller uses these estimates, optimizes a given performance index, and reschedules the generators’ outputs according to their bids for the frequency regulation. The functioning of the proposed LQG regulator has been demonstrated on a four area test system and the results have been compared with those obtained by using an optimal PID controller.


Energies ◽  
2017 ◽  
Vol 10 (5) ◽  
pp. 621 ◽  
Author(s):  
Yunpeng Guo ◽  
Liyan Zhang ◽  
Junhua Zhao ◽  
Fushuan Wen ◽  
Abdus Salam ◽  
...  

2013 ◽  
Vol 13 (05) ◽  
pp. 1350027 ◽  
Author(s):  
KUN LIU ◽  
LONG-XIANG CHEN ◽  
GUO-PING CAI

In this paper, an active controller for buildings with bilinear hysteresis and time delay is studied. The bilinear hysteretic model is treated as a stiffness restoring force. By using specific transformation and augmentation of state parameters, the equation of motion of the system with an explicit time delay is transformed into a standard state space where there is no explicit time delay. A linear quadratic Gaussian control method is proposed for the controller design with time delay. The method is verified with numerical simulations of three-story and 20-story buildings. Comparison study of simulation results indicates that the control performance will deteriorate if the time delay is not taken into account in the control design. The proposed time-delay controller not only effectively compensate the time delay for better control effectiveness, but it also works well with both small and large time-delay problems.


Author(s):  
Anju G. Pillai ◽  
Elizabeth Rita Samuel ◽  
A. Unnikrishnan

AbstractCombined estimation of state and feed-back gain for optimal load frequency control is proposed. Load frequency control (LFC) addresses the problem of controlling system frequency in response to disturbance, and is one of main research areas in power system operation. A well acknowledged solution to this problem is feedback stabilization, where the Linear Quadratic Regulator (LQR) based controller computes the feedback gain K from the known system parameters and implements the control, assuming the availability of all the state variables. However, this approach restricts control to cases where the state variables are readily available and the system parameters are steady. Alternatively, by estimating the states continuously from available measurements of some of the states, it can accommodate dynamic changes in the system parameters. The paper proposes the technique of augmenting the state variables with controller gains. This introduces a non-linearity to the augmented system and thereby the estimation is performed using an Extended Kalman Filter. This results in producing controller gains that are capable of controlling the system in response to changes in load demand, system parameter variation and measurement noise.


Author(s):  
Gaber Magdy ◽  
Abualkasim Bakeer ◽  
Mohammed Alhasheem

Abstract A robust decentralized model predictive control (DMPC) design is proposed for frequency stability of hybrid renewable power systems considering high renewables energy penetration and nonlinearity effects. The Egyptian power system (EPS) considered as a test system comprises both traditional power stations (i.e., steam, gas, combined cycle, and hydraulic power plants) and renewable energy sources (RESs). Where the considered RESs contain both the wind power generated from Zafarana and Gabel El-Zeit wind farms and the solar power generated from Benban solar park, which is considered one of the world’s largest photovoltaic (PV) plants. To obtain an accurate insight into a real modern power system, this research takes into account the effects of the important nonlinearity such as generation rate constraints (GRCs), governor deadband (GDB), and communication time delay (CTD). The designed control is set based on the DMPC for each subsystem independently to ensure the frequency stability of the whole system as each subsystem has different characteristics and operating constraints than the others. Moreover, the decentralized control scheme has become imperative for large power systems due to the high cost of transmitting data over long distances and the probability of error occurrence with the centralized control scheme. To verify the effectiveness and robustness of the proposed DMPC for the EPS, it is compared with the centralized MPC (CMPC) scheme in different operating conditions. The simulation results, which are conducted using MATLAB/SIMULINK® software, emphasized that the proposed DMPC scheme can effectively handle several load disturbances, high uncertainty in the system parameters, and random communication delays. Hence, it can regulate the grid frequency and ensure the robust performance of the studied renewable power system with high RESs penetration and maximum communication delays in the system.


Author(s):  
Mohamad Morhaf Bachar Alnifawi, Bassem Omran, Jomana Mahmoud Mohamad Morhaf Bachar Alnifawi, Bassem Omran, Jomana Mahmoud

Electrical power systems distributed over wide geographical areas are exposed to a set of factors that affect their stability. The most important factors are the time delays between their subsystems. In this paper, a flexible modeling method was concluded consisting of a set of generalized rules and conditions that apply to any network controlled system to ensure its stability with time delays between the elements of the controlled network. In addition, a linear quadratic regulator (LQR) controller was implemented. The aim of the LQR controller is to reduce the negative impact of the time delay on the stability of the electrical power system. The study was applied to a networked electrical power system consisting of three-generation stations distributed in three separate geographical areas. Computer simulations using MATLAB showed a remarkable improvement in the stability of the discrete networked system through the speed of damping the vibrations in the system, and the system ability to be stable at certain limits of the time delay.


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