Active Power Changes Research Articles

Real-time implementation of finite control set model predictive control for matrix converter based solid state transformer

Solid state transformer formed by back-to-back connection of two three-to-single-phase matrix converter, so called MC-SST, owns ac–ac power conversion in a single stage and an absence of the bulky line-frequency transformer when linking ac sources of different voltage amplitudes and frequencies. Current modulation methods for this topology include sophisticated computation of current and voltage vectors besides duty cycle composition. Moreover, extra control design is required to manage the power exchange. In this paper, the easy-to-perform finite control set model predictive control (FCS-MPC) for this type of MC-SST is implemented in real-time platform and compared with the proportional–integral control strategy. The active power changes, different voltage amplitudes and phases, and parameter variations are investigated. Simulation and real-time implementation results demonstrate the simplicity and validity of the MPC approach for power management of the MC-SST system.

Performance Analysis of a Four-Switch Three-Phase Grid-Side Converter with Modulation Simplification in a Doubly-Fed Induction Generator-Based Wind Turbine (DFIG-WT) with Different External Disturbances

This paper investigates the performance of a fault-tolerant four-switch three-phase (FSTP) grid-side converter (GSC) in a doubly-fed induction generator-based wind turbine (DFIG-WT). The space vector pulse width modulation (SVPWM) technique is simplified and unified duty ratios are used for controlling the FSTP GSC. Steady DC-bus voltage, sinusoidal three-phase grid currents and unity power factor are obtained. In addition, the balance of capacitor voltages is accomplished based on the analysis of current flows at the midpoint of DC bus in different operational modes. Besides, external disturbances such as fluctuating wind speed and grid voltage sag are considered to test its fault-tolerant ability. Furthermore, the effects of fluctuating wind speed on the performance of DFIG-WT system are explained according to an approximate expression of the turbine torque. The performance of the proposed FSTP GSC is simulated in Matlab/Simulink 2016a based on a detailed 1.5 MW DFIG-WT Simulink model. Experiments are carried out on a 2 kW platform by using a discrete signal processor (DSP) TMS320F28335 controller to validate the reliability of DFIG-WT for the cases with step change of the stator active power and grid voltage sag, respectively.

Active and reactive power control of the doubly fed induction generator based on wind energy conversion system

Abstract This paper presents a dynamic modeling and control of doubly fed induction-generator (DFIG) based on the wind turbine systems. Active and reactive power control of the DFIG are based on the feedback technique by using the suitable voltage vectors on the rotor side. The rotor flux has no impact on the changes of the stator active and reactive power. The proposed controller is based on the feedback technique in order to reduce the oscillation of the generator. The control approach is estimated through the simulation result of the feedback controller assembled with DFIG wind turbines. It is applied by the feedback control based techniques in order to control the power flowing of DFIG and the power grid. Hence, an improved feedback control technique is adopted to get a better power flow transfer and to improve the dynamic system and transient stability. In stable condition, the improved performance of the controller, the proposed method is verified for the effectiveness of the control method is done in stable conditions.

Dynamic modelling and small signal stability analysis of voltage source converter-based HVDC system

In this paper, the modelling of the entire VSC-HVDC system is presented based on d-q axis decomposition and state space modelling is formulated for analysis. Eigenvalues analysis is used for optimal tuning of PI controller based on PSO technique. The system is simulated under most of the frequently occurring faults and abnormal operating conditions such as three-phase fault, parameter variation, frequency variation and change in active and reactive power, change in short circuit ratio and bus voltage reduction and change in converter parameters through MATLAB simulation. The results are presented for the proposed controller with comparison to conventional PI controller under various fault condition.

Combining two techniques to develop a novel islanding detection method for distributed generation units

Renewable energy is a fast-growing sector given that it does not cause the pollution produced by nuclear and fossil generation systems. The use of renewable energy for distributed generation (DG) is important worldwide not only because it increases profits but also because integrating it into utility systems ensures power supply at points of consumption even when a DG system is disconnected from the main system. Researchers continue to exert efforts in improving islanding detection methods because current detection approaches remain unsatisfactory. Accordingly, this paper presents two new islanding detection methods that are suited for single and multiple DG units. The methods are based on the rate of change in active and reactive power, frequency, and voltage angle. They are tested on single and multiple DG systems with wind turbines and simulated using the Power World Simulator software. The simulation results show that the methods effectively reduce the time spent on islanding detection and efficiently decrease non-detection zones. To verify the accuracy and speed of the proposed methods, the results are compared with those achieved by different islanding detection approaches.

Distributed Generation Placement in Radial Distribution Networks using a Bat-inspired Algorithm

<p>Distributed generation (DG) is an important issue for distribution networks due to the improvement in power losses, but the location and size of generators could be a difficult task for exact techniques. The metaheuristic techniques have become a better option to determine good solutions and in this paper the application of a bat-inspired algorithm (BA) to a problem of location and size of distributed generation in radial distribution systems is presented. A comparison between particle swarm optimization (PSO) and BA was made in the 33-node and 69-node test feeders, using as scenarios the change in active and reactive power, and the number of generators. PSO and BA found good results for small number and capacities of generators, but BA obtained better results for difficult problems and converged faster for all scenarios. The maximum active power injections to reduce power losses in the distribution networks were found for the five scenarios.</p>

Minimization of Voltage Deviation by Considering Active Power Change of Solar PV Plant

For grid-connected photovoltaic systems, voltage profile is one of the most important issues to consider when the active power from PV plant changes because of variation of sunlight or night time. This paper proposes a method to calculate the optimal reactive power from solar PV plant to minimize voltage deviation when active power of one PV plant changes. By injecting of optimal reactive power, the voltage profile of all buses will be improved. The IEEE 33 bus system is selected to analyse the voltage deviation in various conditions [1].

Design of Robust PID Power System Stabilizer for Multimachine Power System Using HS Algorithm

In this paper, the design of a proportional, derivative and integral (PID) based power system stabilizer (PSS) is carried out using a new Meta heuristic harmony search algorithm (HSA) to optimize the parameters. The design of proposed PID controller is considered with an objective function based on eigenvalue shifting to guarantee the stability of nonlinear plant for a wide range of conditions using HSA. The HSA optimized PIDPSS (HSPIDPSS) controller is applied to the standard IEEE ten-machine thirty nine-bus test power system model in decentralized manner and the performance is compared with a robust fuzzy controller. The robustness is tested by considering four plant conditions with change of active power, active load and faults at different buses of the power system to establish, the superior performance with HSPIDPSS over the FPSS.

New Method of Overhead Line Icing Online Monitoring

Present icing monitoring system mainly depends on detecting the meteorological parameters and dynamic characteristics of the structure of the overhead icing line. However, all these systems need additional equipments for data collection. This paper provides a new method based on voltage and current of both ends of the line and discriminates the icing region and its severity via the change of active power and reactive power. It requires the voltage and current serving as signal source which is provided by the data collecting device on the both ends of lines. In this way it can accomplish the Monitoring task of icing transmission.

Single-Phase Grid-Connected PV System Island Effect Detection Based on Active Output Power Change Method

In order to solve the islanding effect of single phase photovoltaic grid-connected system, by introducing some common passive and active detection, and generalizing the advantages and disadvantages of the two detections, we came up with and design an output energy changing method to achieve the detection and prevention of the islanding effect. Modeling and simulating this system under MATLAB , and the results show that the output energy changing method can detect the generation of islanding effect accurately, and achieve the anti-islanding effect effectively.

Coordination of multiple grid-connected inverters for harmonic compensation

For multiple grid-connected inverters with active filter function, it makes sense to regulate every unit to output maximum active power from photovoltaic arrays, as well as eliminate the harmonic due to the non-linear loads connected to the electric networks. Naturally, a centralized control coordination strategy was proposed for the purpose of high facility utilization, good harmonic compensation ability and unwanted overcompensation condition. Based on a vector decoupling control scheme and generalized instantaneous reactive power theory, the solution was to allocate the harmonic eliminating task for every inverter according to the instantaneous power margin of each. The grid current always keeps sinusoidal in spite of non-linear load change and output active power change for any inverter. The simulation results validate the efficacy of the proposed coordination strategy.

Model and Performance of Current Sensor Observers for a Doubly Fed Induction Generator

—This article presents a stator and rotor current observer for a doubly fed induction generator. First, the dynamic models of the wind turbine drive train are presented, and the vector control strategies of a doubly fed induction generator for the rotor-side and grid-side converters are described. A stator and rotor current observer model, which is based on the state–space models of doubly fed induction generators, is then derived by using the stator and rotor voltage signals as inputs. To demonstrate the effectiveness of the proposed current observer, its dynamic performance is simulated using a MATLAB/Simulink software platform under the conditions of active power change of doubly fed induction generators and grid voltage dip fault. Furthermore, the robustness of the proposed current observer is investigated when the doubly fed induction generator rotor resistance is changed. Results show that the proposed observer has good coherence and robustness with the current sensor output when the doubly fed induction generator is in dynamic and transient responses. Compared with the referenced bilinear observer, the proposed observer has better fault-tolerant ability when the fault in the observed current sensor occurs.

Możliwości świadczenia usług regulacyjnych przez generację rozproszoną

The article proposed definitions of regulatory services that can be provided by a local energy source. Shows a review of manufacturing technology including the ability to regulate these sources and assess the potential changes in demand DSO standard conditions sources. The Document presents the DSO’s benefits resulting from the implementation of these services. The use of regulatory services will allow the potential of distributed generation to improve the performance of the network, the creation of a decentralized model of services and enable growth RES connecting to the network. DOI: 10.12736/issn.2300-3022.2014207 Service category P Q U control f control ISC Active power change on DSO’s demand l Frequency control l l Reactive power change on DSO’s demand l 1 l l2 Ability to operate at disturbed conditions l l l l Operation in isolated circuits l l l l Tab. 1. Connection between service categories and grid parameters 1 Only in the case of voltage control service, when change of reactive power proves insufficient, and change of active power enables further control. 2 Only in the case of voltage controls service, in the case of other services U control within a permissible band, depending on grid interconnection point. J. G. Korpikiewicz et al. | Acta Energetica 2/19 (2014) | 70–74

A new method of voltage and frequency control in isolated microgrids using enhanced droop controller optimized by frog algorithm

This paper presents a new method for optimal frequency and voltage control in microgrids (MG) considering the mutual effect of line parameters on power transfer. In MGs each distributed generation (DG) has its special droop characteristics. When a load consumption change occurs in the MG, an imbalance between generation and consumption rises, thus a change occurs in the voltage and frequency of DGs according to their droop characteristics. In order to minimize oscillations of voltage and frequency, we have used optimal droop controller which is based on considering the mutual effects of transfer parameters on active and reactive powers. Since line parameters heavily affect the droop characteristics, these parameters are obtained optimally by the frog algorithm such that oscillations in voltage and frequency are minimized. In order to enhance the controlling scheme, effects of line resistance on reactive power changes and effects of line reactance on active power changes are also considered. Since enhanced droop control depends on line parameters, it cannot be implemented in large MGs; therefore, it is modeled by multi-layer perceptron neural networks. We have used the frog algorithm in order to train the perceptron network. The obtained results show satisfactory voltage and frequency control in various load level. In this paper, MGs are studied and simulated in an isolated state.

Studies on the Low-Voltage Dynamic Reactive Power Compensation and Switching Control for Capacitors Device

This paper is for the problems of the 400V low voltage power capacitor reactive power compensation and for the problems existing in the transient process, resuming the principle of low-voltage capacitor intelligent technology and its implementation briefly. Propose a synchronization of reactive compensation capacitor switching on-off control system based on the micro controller and adaptive control. Real-time monitoring system is used to access system active and reactive power changes in order to extract the zero voltage signals; intelligent control algorithm is used to realize the intelligence of capacitor reactive power compensation on-spot and cutting, which greatly reduce the over-voltage and flow phenomenon produced by the capacitor in the cutting process. The result checked by actual measured shows that the device is stable, reliable, and can be effective to on-site system reactive power compensation and realize intelligent cutting.

Reflections on current components according to CPC concept in a single phase circuit with nonsinusoidal voltage and current waveforms and LTI load

PurposeThe purpose of this paper is to show the limitation of current physical components (CPC) concept in a practical application.Design/methodology/approachThe study proposes using the sum of active and scattered currents in the compensation procedure of the reactive current according to Czarnecki's concept as well as in scattered current elimination, to get the optimal energy transfer from the source supply to the load.FindingsThe results show that CPC concept can be apply only when supply circuit voltage does not consist of interharmonics or/and subharmonics. It can also be shown that elimination of particular harmonics of the scatter current cannot be applied in practice due to the change of active power in the circuit. Only complete elimination of scatter current, e.g. by an active filter is possible without any change of active power.Practical implicationsThe paper provides new information about CPC practical implementation.Originality/valueThis paper presents new features of CPC concept.

Reactive Power Loss & Efficiency Calculation Using Load Flow Technique In Distribution System For Pune City

Reactive power compensation is an important issue in electric power systems, involving operational, economical and quality of service aspects. Consumer loads (residential, industrial, service sector, etc.) impose active and reactive power demand, depending on their characteristics. This paper presents an efficient method for solving the load flow problem in distribution systems and which is implemented for Pune city (India) to check the validity of proposed method. A simple algebraic matrix equation to solve the load flow problem is derived by using the complex power balance equations. By adopting the rectangular coordinate, which requires the neglect of only second order terms in the linearization procedure, the proposed method gives better convergence characteristics. Newton-Raphsonmethod is the famous load flow calculation technique, and normally used dueto its rapidness of numerical convergence. The proposed method estimates the incremental changesof active power on each generation bus with respect to the total system power loss, efficiency and the estimated value are used to update the slack bus power.

Medium-Frequency Induction Melting Furnace as a Load on the Power System

The variable-frequency operation of the coreless induction melting furnace (IMF) has been investigated in detail both theoretically and experimentally. The time variations of the operational impedance value of the IMF, owing to the time-varying resonance frequency and crucible conditions, have been derived for typical melting cycles by using a variable parallel RLC model derived from extensive field measurements. The work coil and its crucible are supplied at variable frequency from a multipulse rectifier and a current-fed load-resonant inverter cascade. Uncharacteristic current harmonics caused by cross-modulation phenomenon across the alternating current ac-dc-ac link have been derived theoretically and verified by field tests. These theoretical results and extensive field measurements on a sample IMF installation have shown the following: 1) The major power quality problem of an IMF as a load on the power system is the injection of various characteristic and uncharacteristic current harmonics to the grid; 2) line currents on the supply side are nearly balanced; 3) flicker contribution is below the limits specified in the standards; 4) reactive power demand is relatively low and the variations in the magnitude and rate of change of active power are not drastic; and 5) no voltage sag and swell phenomena arising from furnace operation occur.

Direct Active and Reactive Power Regulation of Grid-Connected DC/AC Converters Using Sliding Mode Control Approach

This paper proposes a new direct active and reactive power control (DPC) for the three-phase grid connected dc/ac converters. The proposed DPC strategy employs a nonlinear sliding mode control (SMC) scheme to directly calculate the required converter's control voltage so as to eliminate the instantaneous errors of active and reactive powers without involving any rotating coordinate transformations. Meanwhile, there are no extra current control loops involved, which simplifies the system design and enhances the transient performance. Constant converter switching frequency is achieved by using space vector modulation, which eases the design of the ac harmonic filter. Simulation and experimental results are provided and compared with those of the classic voltage-oriented vector control (VC) and conventional lookup table (LUT) DPC strategies. The proposed SMC-DPC is capable of providing enhanced transient performance similar to that of the LUT-DPC, and keeps the steady-state harmonic spectra at the same level as those of the VC scheme. The robustness of the proposed DPC to line inductance variations is also inspected during active and reactive power changes.

Investigation of StatComs With Capacitive Energy Storage for Reduction of Voltage Phase Jumps in Weak Networks

The voltage at the point of common coupling (PCC) in a weak network is very sensitive to load changes. A sudden change in active load will cause both a phase jump and a magnitude fluctuation in the bus voltage (voltage at the PCC), whereas reactive load changes mainly affect the voltage magnitude. With the addition of energy storage to a static synchronous compensator (STATCOM), it is possible to compensate for the active power change as well as providing reactive power support. In this paper effective active power compensation schemes are proposed. Simulation and experimental results verify the compensation schemes by showing that a STATCOM with energy storage can significantly reduce phase jumps and magnitude deviations of the bus voltage under load disturbances.