Active Power Generation Research Articles

Load-Frequency Control in a Two-Area Power System Using the Fuzzy-PID Method

Power systems are plant units connected to each other, with the electrical power flow constantly moving between them and the load. All systems must be implemented in such a way that they remain stable not only under normal conditions but also after the implementation of unwanted inputs or malfunctions and should be able to return to stable nominal conditions as soon as possible. The basic factors of stability control in a power system are the frequency of different areas and the amount of power flow between them. Now that the main goals of stability control in a power system have been stated, these indicators must be kept at their desired levels through the design and implementation of controllers. This paper first describes the mechanism of load frequency control (LFC). The parameters of several types of complementary controllers are then designed based on the proposed algorithm. The controllers designed on the simulated power system are finally applied, and the effect of each controller on faster damping of frequency fluctuations is discussed. In this study, a multi-area power system is simulated and the effect of disturbance in each area and the performance of the proposed controller in controlling the frequency of the whole network are investigated. The case studies show that the share of active and reactive power generation sources in each region have the greatest impact on frequency control, given that the proposed control coefficients are determined using fuzzy logic in the shortest possible time and the number of transient oscillations eliminated, resulting in a steady system.

An Optimized Proportional Integral Derivative (PID) based Power System Stabilizer (PSS) for Damping of Active Power Oscillations

Rising load demand and possibilities of short interruptions either due to temporary faults or equipment switching may lead to a transient instability in terms of growing oscillations and eventually result into cascaded outages if not being damped properly and timely. To damp out such oscillations, the power system stabilizers (PSS) are invariably being installed to regulate the excitation of synchronous generators. In this research, a comparative analysis among the two design variants of PSS i.e., Lead Lag and PID is performed by comparing the overshoot and settling time of generator active power after distrubance, to observe the effect of each on the system characteristics and nominal conditions. The results obtained show a better performance of PID based PSS having better overshoot response and reduced settling time for symmetrical as well as unsymmetrical faults.

Optimal Active Power Generation in Electrical Networks Using Distributed Fixed-Time Control of Multi-Agent Systems

This paper tackles the Economic Dispatch Problem (EDP) in power systems, with the objective of generating optimal active power at each source to minimize overall generation costs, while maintaining the power generation-demand equality and staying within the source generation limits. The main motivation behind this work is to create a power optimization strategy that accomplishes these goals while providing superior performance in terms of convergence speed and accuracy of the optimal solution. To this end, a fixed-time active power optimization protocol is proposed for power sources in electrical networks. Distributed and local fixed-time control laws of first-order multi-agent systems are developed for this purpose. This paper presents four technical contributions: i) minimizing active power generation costs in electrical network sources within a predetermined maximum settling time without violating their generation limits while ensuring generation-demand equality, ii) a distributed overall control system connected through a sparse communication network modeled as an undirected graph that avoids the pitfalls of centralized solutions, iii) a model-free optimization method that does not require previous knowledge of power system parameters, and iv) a continuous optimization law that provides smooth power variations. Simulations are conducted to demonstrate the effectiveness of the proposed approach.

MATHEMATICAL MODEL OF A VOLTAIC SOLAR POWER PLANT

In many countries, including Armenia.Solar power plants, are constructed according to the scheme of voltaic solar power plants that directly convert solar energy into electrical energy. The schemes and methods of research and calculation of such solar power plants are not sufficiently developed. That is solution to these issues is relevant. Mathematical models and software and computing complexes are effective tools for research and calculation. The developed schemes and mathematical model of a voltaic power plant based on a voltage inverter and a resonant parallel-series filter operating in parallel with the network are presented. The intensity of solar radiation is an argument for the processes taking place and, with the existing approach, is expressed by the magnitude of the generated direct current. Voltage and power are considered derived quantities. In the schemes and mathematical model, a transformation is performed in which solar panels are presented as a voltage source, where the independent variable is voltage, which linearly depends on solar radiation, and the function is the generated current and load power. Using the model, the following was studied: ensuring a sinusoidal shape of the output voltage, the frequency spectra and distortion coefficients of the output voltage shape were calculated, the functions of the transient process when connecting a solar power plant to the network, the load characteristics of the generation and transmission of active and reactive power to the network were determined. The developed mathematical model of a voltaic solar power plant is an adequate tool for research and calculation of power plant parameters. Studies conducted on the model confirm the possibility of generating and transmitting active and reactive power to the network, linearly related to the intensity of solar radiation, while ensuring the sinusoidal shape of the output voltage and satisfactory quality of the transient process. To increase the overloadability, stability and controllability of power (both active and reactive) of voltaic solar inverter power plants, it is advisable to use buffer batteries at the inverter input and/or synchronous compensators at the inverter output, as well as parallel operating synchronous generators of traditional power plants with low communication resistances.

An Orthogonal Learning Bird Swarm Algorithm for Optimal Power Flow Problems

A dominant statistical method, in which the best combination of factors’ levels are predicted by analyzing a few representative combinations of factors’ levels named as orthogonal experimental design (OED). The OED is an effective approach for analyzing the effect of multi-levels factors simultaneously and it works on orthogonal learning (OL) strategy. An evolutionary programming based heuristic method has two contradictory features such as exploration and exploitation, balancing in these features have significant impact on its optimization performance. We have applied an OED based auxiliary search strategy for enhancing performance of the bird swarm algorithm (BSA) by improving its exploitation search ability. It is a challenging task to keep balance among two contradictory features – exploration and exploitation of a heuristic approach, while addressing optimal power flow (OPF) problems in power systems. In this research study, we have proposed improved BSA (IBSA) for solving the OPF problems in thermal power systems. We have conducted a study of the OPF problems with objective functions - reducing electricity generation cost, emission pollution, and active power loss to measure the efficiency of proposed IBSA. In this work, we have utilized five benchmark functions and solved OPF problems using three IEEE test systems including IEEE-30 bus system, IEEE-57 bus system, and IEEE-118 bus system to verify stability, effectiveness, and performance of proposed IBSA. The statistical and simulation results have indicated that the proposed IBSA has better convergence, efficiency, and robustness features than the original BSA as well as other heuristic approaches. It is observed that lowest electricity generation cost 800.3975$/h on IEEE-30 bus system, 41663.5500$/h on IEEE-57 bus system, and 134941.0367$/h on IEEE-118 bus system have been achieved using proposed IBSA to address the OPF problems. Furthermore, in transmission lines of the power system network minimum active power loss 16.2869MW has been observed by conducting a case study on the IEEE 118-bus system based on the proposed IBSA approach.

PV Power Curtailment and BESS Management for Distribution Networks: A Practical Approach

Voltage and thermal limits in distribution feeders are the main features assessed to determine their hosting capacity (HC) due to the integration of distributed generation (DG), especially photovoltaic systems (PV). This paper proposes a PV active power curtailment control strategy combined with the management of battery energy storage systems (BESS) under high penetration of PV systems. In addition, the voltage imbalances rate is included in the evaluated operating parameters in order to reduce voltage and thermal issues and avoid or postpone the feeder reinforcement costs. The study uses Monte-Carlo and stochastic simulations to determine the HC and the PV system's random location. Also, several PV systems capacities are proposed by using statistics. Mexican standards are used for the HC estimation and to perform the power curtailment control strategy. The use of smart PV inverters is considered to reduce or increase the PV active power generation. The BESSs are capable of regulating their charge and discharge cycle independently. The results show the advantages of using strategies separately and in combination can be beneficial to improve the feeder performance.

Development of converter configuration and corresponding control strategy for wind turbines using permanent magnet synchronous generator: A Case study

This study aims to investigate a feasible converter architecture and corresponding control method for Wind Turbine (WT) systems using permanent magnet synchronous generators (PMSG). The converter configuration is designed based on the AC/DC/AC converter, including the Diode Bridge Rectifier (DBR) and Pulse Width Modulated Current Source Inverter (PWM-CSI), Buck-Boost Converter (BBC), and Bypass Chopper (BC). The control strategy for the proposed converter is developed to enhance the operating performance of WT-PMSG, which must satisfy four requisitions. Firstly, it proposes the control approach for the pitch angle to control the output power of the WT when the wind speed is over the rated value. The selected control variables are the generator speed and active power. Secondly, the Maximum Power Point Tracking (MPPT) is archived to the satisfaction of the full-range operation through the control strategy for the BBC. The control strategy is applied by the Proportional Integral (PI) controller. The control variables are the generator speed and the diode rectifier's output DC current. Thirdly, the control strategy for PWM-CSI controls the voltage at the connection point and the frequency of the inverter. Fourthly, the DC-link voltage is controlled to the constant value at various operating conditions. Simulation of a 3MW and 0.69 kV WT-PMSG was carried on in PSCAD software to verify under considering the variable wind speed and the three-phase fault. The obtained results prove the feasibility of the proposed WT-PMSG system that serves as an alternative for a high-power wind energy conversion system.

Metaheuristic for the Allocation and Sizing of PV-STATCOMs for Ancillary Service Provision

In addition to active power generation, photovoltaic inverters can be used to provide ancillary services to grids, including reactive power compensation. This paper proposes a metaheuristic approach based on particle swarm optimization for the allocation and sizing of photovoltaic inverters that perform the complementary functions of static synchronous compensator (PV-STATCOM) units. The objective of the aforementioned approach is to reduce the initial investment cost in the acquisition of PV-STATCOM units. The proposed methodology considers both the daily load curve and generation and is applied to a 33-bus test system. The methodology is validated based on an exhaustive search algorithm and tested over 1000 consecutive simulations for the same problem; consequently, the methodology produces low standard deviations and errors, indicating its robustness. The methodology demonstrates an improved grid voltage profile throughout the day when applied to the 33-bus test system. Furthermore, the photovoltaic inverter efficiently performs its main function of active power generation. As a major contribution, the proposed methodology may assist investors in determining the allocation and sizing of PV-STATCOM units to perform the ancillary service of reactive power compensation in grids

A Non-iterative Optimal Power Flow Calculation Method in Power System

The optimal power flow is very important in the study of power system, and it is of great significance for the economic operation of the power system to solve the active power output of the generator through the optimal power flow. In order to solve the problem that the traditional method is sensitive to the initial state and the large iteration times, this paper applies the holomorphic embedding method to solve the optimal power flow. By embedding holomorphic variables, the holomorphic embedding forms of constraints and KKT conditions are obtained. The power series coefficients of node voltage and generator active power output are calculated by non-iterative solution. Finally, the active power output of the generator is obtained by the method proposed in this paper, and then the lowest power generation cost of the system is calculated. Simulation results on IEEE study Case 3, Case 4, Case 30 and Case 39 verify the feasibility and accuracy of the proposed method.

Synchronized-ambient-data-driven participation-factor-based generation rescheduling strategy for enhancing the damping level of interconnected power systems

Participation factor (PF) is widely used in assisting the selection of critical rescheduled generators in re-dispatching issues. The conventional PF relies heavily on the detailed system model and is commonly limited to quantifying the participation degree of system state variables in electromechanical mode. In this paper, the PF with respect to generator active power is presented by employing LQ-decomposition based recursive sub-DMD (Rsub-DMD) from synchrophasor ambient data. The proposed participation factor directly quantifies the relationship between the mode damping and generator outputs with the ability to track system operation conditions, thereby identifying the most effective re-dispatching generators online. Then a general online generation rescheduling strategy integrated with the proposed PF is applied for enhancing critical damping. The proposed PF-assisted rescheduling strategy is ambient data oriented, and the developed scheme enables online damping enhancement of critical mode. The effectiveness of the PF-assisted selection of rescheduled generators and the proposed rescheduling strategy has been demonstrated via numerical simulation and simplified China Northern system model cases.

Multiple objective optimization based on particle swarm algorithm for MMC-MTDC system

Multi-terminal high voltage DC (MTDC) network is an effective technology to integrate large-scale offshore wind energy sources into conventional AC grids and improve the stability and flexibility of the power system. In this paper, firstly, an analytical model of a general applicable MTDC system integrated with several isolated AC grids is established. Then, an improved AC-DC power flow algorithm is used to eliminate the additional DC slack bus or droop bus iteration (SBI/DBI) step of the conventional AC-DC sequential power flow. A multi-objective optimal power flow (MOPF) algorithm is proposed to minimize two optimization targets, i.e., overall active power loss and generation costs of the system. To increase the degree of freedom, adaptive droop control is used in the proposed optimization algorithm in which the voltage references and droop coefficients of the modular multilevel converters (MMCs) are control variables. A multiple objective particle swarm optimization (MOPSO) method is applied to solve the MOPF problem and achieve the Pareto front. A technique for order of preference by similarity to ideal solution (TOPSIS) is incorporated in the decision analysis section and helps the decision maker to identify the best compromise solution.

Matlab Applications for Power Flow Analysis

In this paper a brief review has been done on MATLAB Applications for power flow analysis with realistic loads . The classical algorithms for power flow Gauss Seidel and Newton Raphson method has been implemented under MATLAB codes, Simpower, simulink ,and fuzzy logic environment. Simscape™ Electrical™ can perform a power-flow, or load-flow, analysis for an AC, DC, or mixed AC and DC electrical power transmission system modeled using the Simscape three-phase electrical domain. A load-flow analysis allows to determine the voltage magnitudes, voltage phase angles, active power, and reactive power of the electrical system in steady-state operation. For a given steadystate operating point, the load-flow data reveals the:Voltage magnitude and voltage phase angle at each bus,Active and reactive power generation for each generator that supplies the grid,Active and reactive power that flows to each load that places demand on the grid , the data is used to determine ideal operating conditions or estimate the response of your system to hypothetical situations.

Sensorless passivity based control of doubly-fed induction generators in variable-speed wind turbine systems based on high gain observer

The current study presents a robust sensorless control using passivity based control (PBC) combined with high gain observer (HGO). The proposed controller is applied to control the generated doubly-fed induction generator (DFIG) active and reactive power installed on a variable speed wind energy conversion system. The control objective is used to regulate independently the DFIG stator active and reactive power, which are decoupled by using the field oriented control technique. Additionally, this process leads to reduce the cost of control scheme by eliminating the speed sensor. Firstly, the DFIG is modeled under the port controlled Hamiltonian (PCH) model, as well as the method of simultaneous injection damping. Then, the DFIG is further modeled by assignment passivity based on the simultaneous injection damping and assignment (SIDA-PBC) control of the obtained model under such conditions and a comparison with the fuzzy sliding mode controller is carried out. Furthermore, the HGO is selected in order to estimate the rotor position and the speed from the measurement of the DFIG currents and voltages, and compared with fuzzy sliding mode observer. For testing the proposed control scheme performance, a 1.5 MW DFIG system is developed and simulated using MATLAB/Simulink. The obtained results demonstrate the effectiveness of the proposed control scheme in the presence of various DFIG parameters variation. Additionally, the control objective is achieved without speed sensor.

Dynamic modeling of power network-integrated wind turbine

This paper presents the performance investigation of voltage and current for dynamic model of the wind turbine. In this study, the various numbers of wind turbine speed are applied in the simulation. This treatment is intended to see how much influence the turbine speed has on the voltage and current output. IEEE 14 bus system is integrated to the wind turbine in order to observe the impact of on-grid connection to the voltage and current performance. How to model wind turbine in PSCAD simulation software also discussed in this paper. The detail of supporting components in designing a wind turbine system and their functions are also explained. Several values of turbine speed are also considered in this paper as a study material in seeing the performance of wind turbines. The relationship between wind speed and pitch angle will also be discussed to ensure that the wind turbine is not damaged. In order to prove the accuracy of the simulation model, the obtained measurement generation of active power from the wind turbine is matched with the manual calculation. Based on the various wind speed values that have been tested, this can be the basis for the application of wind turbine (renewable energy) design development for further research.

OPTIMIZATION OF CHARGE / DISCHARGE TIME OF ACTIVE FILTER CAPACITORS DURING VOLTAGE FLUCTUATIONS

A voltage regulator on capacitors has been developed for the control circuit of a parallel active filter based on dq-theory with a block of sliding averaging current in the current control circuit i_d. It contains a delay unit, a digital low-pass filter of the first order FIR or IIR (depending on the variant of the considered scheme) and the unit “sgn”, which stabilizes the output signal. The voltage control circuit on the capacitor can be implemented entirely in digital signal processing and used instead of the analog PID controller, which is much more effective if you need to adapt the circuit to the load mode. Most analog filters suffer from phase distortion when signals at different frequencies are delayed by different amounts. Although it is still present in digital IIR filters. FIR filters are usually designed as a “linear phase”, which means that the filter has no phase distortion. Phase distortions occur due to the fact that signals of different frequencies are delayed differently when crossing the filter. For IIR filters, it is necessary to enter an additional factor that will regulate the group delay, during which the filter will delay the signal of a certain frequency. If you do the same for the FIR filter, you will see a straight horizontal line, which means that all signals are delayed by the same amount, which is good and will provide better signal quality. The unit “sgn” does not affect the process of maintaining the voltage on the capacitors and the speed of transients, its role is to enhance the compensatory capacity of the voltage regulator by filtering the digital signal. The selected filter, by automatically stabilizing the voltage on the capacitor provides a stable charge / discharge process of the capacitor and a high level of compensation of higher harmonics without significant additional generation of active power in the network. When used in the context of real-time analog systems, the digital filter sometimes has a problematic delay (input-output time difference) due to analog-to-digital and digital-to-analog conversion and smoothing. It is shown that by optimizing the charge / discharge time of the capacitor of the power active filter it is possible to achieve the minimum duration of the transient process with the minimum values of harmonic distortions.

An Evaluation of Co-Simulation for Modeling Coupled Natural Gas and Electricity Networks

Reliance on natural gas for power generation has increased the coupling between gas and power networks. While this coupling can bring operational and economic benefits, it can also yield challenges, as the constraints in one system can impact the other. Co-simulation can capture the constraints and interactions between these systems, but so far, there has been limited comparison of co-simulation results to those of an integrated model. In this work, we develop a new co-simulation framework using the HELICS platform and the SAInt tool for modeling transient gas and AC optimal power flow. We evaluate this co-simulation framework against a fully integrated version of the SAInt power and gas simulators, thus providing a benchmarking of the co-simulation approach. We compare results across the two approaches for two test networks and a network representing the Belgian power and gas networks, testing both normal operating conditions and cases with compressor disruptions. In each of the cases tested, we find nearly identical results from the two approaches across various metrics of interest, such as nodal pressure, gas flow rates, and active power generation. This alignment suggests that co-simulation can yield comparable results to fully integrated models for modeling coupled gas and electricity networks.

Transient stability constrained optimal power flow solution using ant colony optimization for continuous domains (ACO R )

This paper aims to improve transient stability using the Ant Colony Optimization for Continuous Domains (ACOR). This improvement is obtained by solving the Transient Stability Constrained Optimal Power Flow (TSCOPF) problem and extracting the sensitivity coefficients. The presented costs minimization approach requires less execution time to manage energy resources efficiently and compared to other conventional methods, it also outperforms based on statistical indicators such as mean and standard deviation. Furthermore, the sensitivity analysis of the suggested method considers the active power generation of the generating units along with their terminal voltage, which notably decreases the operation cost and reduces risk to the power system. On the other hand, the application of ACOR algorithm can reduce the fuel cost of power system operation to 60,928.36 $/h with a decrease of 15.33 $/h compared to the conventional method with a standard deviation equal to 2.51 $/h and an execution time of 7.66 s. This strategy could be used in power system dispatching. This method is implemented on the New England 39 bus system, and the results demonstrate the method's efficiency compared to other conventional methods.

Exploring potential storage-based flexibility gains of electric vehicles in smart distribution grids

Flexibility is one of the most important solutions for facilitating the variability of renewable energy sources (RESs) in a distribution network. It is predicted that electric vehicles (EVs) can play an effective role in improving it in the distribution networks. So, this paper presents multiobjective scheduling of batteries of EVs in parking lots (EVPLs) to improve the storage-based flexibility of smart distribution networks (SDNs). The proposed formulation minimizes the energy cost and the voltage deviation function and maximizes the system flexibility (SF) as multiobjective functions that will be optimized subject to the AC load flow, RES and EV constraints, and the allowable limits of the flexibility and operation indices. The resulting model is in the form of a nonlinear programming (NLP) model. Therefore, an equivalent linear programming (LP) formulation is obtained for the original problem to achieve the global optimum result. The stochastic programming approach is used to model uncertainties of the load, active power generation of RESs, price of energy, and EV parameters. The flexible power management is formulated as one of the objective functions of the proposed multiobjective framework, which is solved by using the ε-constraint method, reaching the best possible compromise solution by a fuzzy decision-maker. The proposed framework is tested by using a 33-bus radial test distribution network in the GAMS software environment to evaluate the EVs capability in improving the flexibility indices. Based on the numerical results, it is observed that the proposed scheme with optimal energy management of EVs is able to obtain a high flexibility for SDN. It can also reduce energy losses in terms of network operation and provide a rather smooth voltage profile.

Finding Optimal Solutions for the Placement of Reactive and Active Power Generation Components in Distribution Networks Using a High-Performance Metaheuristic Algorithm

This paper proposes a modified slime mold algorithm (MSMA) for finding optimal site and size of both photovoltaic generators (PGs) and shunt capacitors (SCs) in radial distribution power systems (RDPSs). The most suitable site together with the most effective size of PGs and SCs can reduce currents of conductors effectively, resulting in the significant reduction of active power loss on all conductors. MSMA and two other applied algorithms, slime mold algorithm (SMA) and equilibrium optimizer (EO), are implemented for three study cases of IEEE 33, 69, and 85 RDPSs including Case (1) place only PGs with both active and reactive power generations; Case (2) place both SCs and PGs with only active power generation; and Case (3) place both SCs and PGs with both active and reactive power generations. Comparisons with SMA and EO, MSMA can reach either the same loss or much smaller loss for study cases. Furthermore, MSMA also outperforms other previously published methods for the three study cases, and it can reach significantly smaller loss for the three cases by 1.5%, 30.55%, and 19.64% for system 1, 7.59%, 0.26%, and 0.32% for system 2, and 7.51%, 34.2%, and 22.65% for system 3. As comparing the loss among three study cases obtained by MSMA, Case 3 can reach less loss than Case 1 and Case 2 by 11.71% and 11.64% for system 1, 26.27% and 26.13% for system 2, and the same 26.6% for system 3. Thus, it is recommended that MSMA is the most effective algorithm and the placement of both SCs and PGs with active and reactive power generations is the most optimal.

Automatic Generation Control Application for Transmission and Generation Centres

Recently, a new Emergency Control Centre for Albanian Transmission System Operator (TSO), which includes Supervisory control and data acquisition (SCADA) and Automatic Generation Control (AGC) applications, has been commissioned. Nowadays, an AGC application is being prepared for the biggest generation company in Croatia, as part of control centre for hydropower plants within western part of Croatia. Both of these implementations use the same AGC application, which is presented in this paper. Although AGC for TSO and AGC for Generation Centre (GC) have many similarities, their main goals are different. AGC for TSO must mainly regulate system’s frequency and area’s active power interchange to their desired values, using only power plants engaged in load-frequency control (LFC). However, AGC for GC must ensure that power production of each power unit not engaged in LFC tracks its planned value, while also ensuring that centre’s share in LFC is being respected. Albeit the AGC is standalone application, in both afore-mentioned implementations it is affiliated with SCADA application, from which it obtains all required input measurements and indications and to which it delivers calculated setpoints. Additionally, all AGC pictures are integrated into SCADA pictures as well, in order to simplify operation and monitoring functionalities. AGC for Albanian TSO controls active power generation of six hydro power plants engaged in LFC. AGC for GC West in Croatia controls active power generation of ten hydro power plants. In both implementations, communication with remote objects is done using IEC 60870-5-104 communication protocol, while communication with other control centres is done using ICCP communication protocol. Power production plans are sent to AGC either from Market Management Systems (in TSO case) or from scheduling and optimization application (in GC case).