Performance Of Power Control Research Articles

A New Photovoltaic Power Generation of Switched Inductor Quasi ZSource Inverter for BLDC Motor Drive Control

The control of Brushless DC Motor is a challenging task while interfacing with renewable power generation. Especially in photovoltaic power generation having issues such as low power extraction, lagging of current with respect to voltage generation, low load of drives, multi stage of power conversion and control complexity. In this paper Switched Inductor Quasi Z Source Inverter (SL-QZSI) introduces for photovoltaic fed brushless DC Motor drive for reducing multistage power generation, additional power extraction of photovoltaic and reducing complexity of control circuit. Switched inductor circuit is replaces single inductor of quasi z source circuit and extracting high power, improving efficiency without using voltage lifting unit, coupled inductors and transformers. The speed sensing and reference current is used to estimate an actual reference current and Maximum Power Point Tracking (MPPT) is used to tune various modulation value of reference current to generate Maximum Boost Pulse Width Modulation (MB-PWM) scheme. MPPT is generated modulation index value with respect to photovoltaic power conditions. The proposed topology is implemented using MATLAB/Simulink software to verifying about unique merits of power conversion stage and control performances of proposed switched inductor quasi z source inverter topology.

Suppression of synchronous resonance for VSGs

The virtual synchronous generator (VSG) is an attractive interfacing technique for high-penetration renewable generation. By incorporating the inertia control, the grid-connected voltage-source converter can behave in a similar way with the SGs, which is helpful to enhance the stability of the power system. However, it is reported that the synchronous frequency resonance (SFR) can be aroused in the VSG due to the resonance peaks in the power control loops at the fundamental frequency. By modelling the power control loop in the dq domain, the mechanism underlying the SFR is studied. It reveals the frequency shift of the grid impedance in dq frame is the origin of SFR. Moreover, the phase-amplitude cross-regulation scheme is proposed to suppress the SFR. In this way, the resonance peaks in the power control loops are completely removed, and the coupling effects between the active power and reactive power loops are also eliminated. Therefore, superior power control performances can be achieved. Simulation results verify the effectiveness of the theoretical analysis and both dynamic performance and stability of the power loops are greatly improved by the proposed cross-regulation scheme.

Design and Analysis of a Three Level Neutral Point Clamped Fuel Cell based Grid Connected Inverter

The aim of this paper is to present the design and analysis of a three level neutral point clamped grid connected inverter using fuel cell as a green energy source. Three different controllers that is a boost dc to dc converter, a power controller and a current controller were being modeled and simulated on matlab. The system was being investigated using a PI controller and a sliding mode controller. Simulation results show that the sliding mode controller shows a superior performance of the active power control and the voltage regulation capability as compared to a simple PI controller under voltage sag conditions.

Power headroom report-based uplink power control in 3GPP LTE-A HetNet

In a 3rd Generation Partnership Project Long Term Evolution-Advanced (3GPP LTE-A) uplink, user equipment (UE) has a maximum transmission power limit defined by the UE power class. Generally, the cell edge UE has a higher probability to be constrained by the maximum transmission power level owing to the compensation of the large pathloss. When the UE transmission power is constrained by the maximum level, allocating a higher number of physical resource blocks (PRBs) than the UE power capability can afford will reduce the transmission power to be allocated per PRB, resulting in inefficient use of power resources. To avoid this power inefficiency, the uplink transmission power can be controlled according to the number of PRBs allocated using the power headroom report-based power efficient resource allocation (PHR-PERA) scheme proposed in this paper. Furthermore, adaptive open-loop power control (OL-PC) based on the signal-to-interference-plus-noise ratio (SINR) and the uplink interference is used to improve the cell capacity. By the uplink power control employing the proposed PHR-PERA scheme, the macro and femto UE throughputs were increased by 49.9 and 5 %, respectively, compared to the case of conventional fractional power control (FPC). Additional gains of 21.9 and 4.8 % for macro and femto UE throughputs, respectively, were achieved by adaptive OL-PC. The performance of fast closed-loop power control (CL-PC) based on the received SINR is also evaluated in this paper. The simulation results demonstrate that CL-PC supports OL-PC by compensating the fading effect for the UE uplink SINR to meet the target SINR.

Control parameter optimization for AP1000 reactor using Particle Swarm Optimization

The advanced mechanical shim (MSHIM) core control strategy is implemented in the AP1000 reactor for core reactivity and axial power distribution control simultaneously. The MSHIM core control system can provide superior reactor control capabilities via automatic rod control only. This enables the AP1000 to perform power change operations automatically without the soluble boron concentration adjustments. In this paper, the Particle Swarm Optimization (PSO) algorithm has been applied for the parameter optimization of the MSHIM control system to acquire better reactor control performance for AP1000. System requirements such as power control performance, control bank movement and AO control constraints are reflected in the objective function. Dynamic simulations are performed based on an AP1000 reactor simulation platform in each iteration of the optimization process to calculate the fitness values of particles in the swarm. The simulation platform is developed in Matlab/Simulink environment with implementation of a nodal core model and the MSHIM control strategy. Based on the simulation platform, the typical 10% step load decrease transient from 100% to 90% full power is simulated and the objective function used for control parameter tuning is directly incorporated in the simulation results. With successful implementation of the PSO algorithm in the control parameter optimization of AP1000 reactor, four key parameters of the MSHIM control system are optimized. It has been demonstrated by the calculation results that the optimized MSHIM control system parameters can improve the reactor power control capability and reduce the control rod movement without compromising AO control. Therefore, the PSO based optimization method can be used to optimize MSHIM control system parameters to provide much better reactor control capabilities.

Distributed Downlink Power Control by Message-Passing for Very Large-Scale Networks

Downlink power control is revisited by assuming very large-scale networks. In very large-scale networks, conventional centralized power control schemes quickly become impractical owing to the huge computational burden and limited backhaul capacity. Alternative distributed power control schemes have been proposed; however, these schemes suffer from poor performance when compared with the centralized power control. In this work, a completely new approach to distributed downlink power control is proposed using a belief-propagation (BP) framework. The proposed BP approach includes two tasks: first, the sum rate maximizing power control problem is modeled as a factor graph representation. Second, a message-passing algorithm is constructed on the basis of the factor graph, which efficiently computes a near-optimal solution in a distributed manner. The practical issues for implementing the proposed BP approach are extensively discussed in terms of the computational complexity, signaling overhead, convergence, and latency. Surprisingly, the simulation results verify that the average sum rate performance of the proposed BP-based power control is nearly equivalent to that of centralized power control schemes. The proposed BP-based power control even outperforms the centralized binary on/off power control and approaches the performance of geometric programming power control, which is the best-known centralized power control, within only 0.8% of the average sum rate.

Dynamic Performance of Reactive Power Control for Voltage Support in Low-Voltage Distribution Networks with Photovoltaic Systems

The coordinated reactive power control among photovoltaic (PV) systems, without communication requirement, is introduced to prevent the over-voltage problems in radial distribution networks. The voltage source inverter in PV system can provide the reactive power control to deal with the dynamic voltage variations. Two reactive power control methods, Q(P) and Q(V), can be employed into each PV system depending on its location. The dynamic voltage control performances are examined on simulation in DIgSILENT PowerFactory software. The results showed that the proposed control method can mitigate the rise of voltage level sufficiently.

A multi-objective placement of phasor measurement units using fuzzified artificial bee colony algorithm, considering system observability and voltage stability

This paper presents Multi-objective Optimal Placement of Phasor measurement units (MOPP) to improve the performance of power system monitoring and control. It is proposed for achieving complete observability with a minimal number of phasor measurement units (PMUs) and maximising the voltage stability level of the system, simultaneously. As the above mentioned objectives are conflicting in nature, a fuzzified binary artificial bee colony algorithm is considered to solve the MOPP problem to offer a good tradeoff solution between the competing objectives. Here, fuzzy membership for each objective function is designed and proposed to decide the best solution of MOPP problem. Initially, weak buses are identified using the fast voltage stability index calculation for their close and reliable monitoring. This is done in order to prevent the outage of these buses. The conventional rule is used to minimise the number of PMUs and a new rule is proposed to maximise both the observability and voltage stability levels of the system. The efficiency of the artificial bee colony method is validated on IEEE 14, 30 and 57 bus test systems and it is verified by comparing the performance of proposed method with earlier works.

Optimal Power Control and Error Performance for Full-Duplex Dual-Hop AF Relaying Under Residual Self-Interference

This paper investigates optimal power allocation schemes at the relay and their impact on the error performance for a full-duplex, dual-hop, amplify-and-forward system using finite constellations and under residual self-interference. The variance of the interference is assumed to be proportional to the λ-th power of the transmitted power. The worst-case pairwise error probability (PEP) is considered as the performance criterion. To find the optimal power allocation, we first derive a closed-form expression for the derivative of the PEP. A simple bisection method is then applied to obtain the optimal scheme. An asymptotically optimal allocation in closed form is also obtained assuming high power regions. From this analysis, it is shown that power allocation leads to a better diversity performance than full power transmission. In addition, the error floor behavior observed in previous works can be eliminated through power allocation. Numerical results are finally presented to illustrate the advantage of the proposed scheme over full power usage.

Predictive Direct Capacitor Power Control Based on Fractional-Order PID Controller of Three-Phase Voltage Source PWM Rectifiers

In order to improve the dynamic performance of three-phase voltage type PWM rectifiers predictive direct capacitor power control, in view of the deficiencies of slow response and poor dynamic performance of present PI control of load disturbance, the fractional order PID controller of the DC side voltage control section is introduced to the capacitive power control. The new predictive direct power capacitor control strategy has been proposed. It consists of two parts: the outer loop of voltage square model of fractional order PID and the inner loop of capacitor power and the reactive power in network side. Through decoupling control with the prediction control of the inner loop and the voltage outer loop of fractional PID, the dynamic performance of a direct power control has been improved. The Matlab/Simulink simulation results prove that the system has better dynamic performance, robustness and response speed of direct power control.

A performance comparison of DFIG using power transfer matrix and direct power control techniques

This paper presents a direct power control and power transfer matrix model for a doubly-fed induction generator (DFIG) wind energy system (WES). Control of DFIG wind turbine system is traditionally based on either stator-flux-oriented or stator-voltage-oriented vector control. The performance of Direct Power Control (DPC) and Power transfer Matrix control for the same wind speed are studied. The Power transfer matrix Control gave better results. The validity and performance of the proposed modelling and control approaches are investigated using a study system consisting of a grid connected DFIG WES. The performance of DFIG with Power Transfer Matrix and Direct Power Control (DPC) techniques are obtained through simulation. The time domain simulation of the study system using MATLAB Simulink is carried out. The results obtained in the two cases are compared DOI: http://dx.doi.org/10.11591/ijpeds.v5i2.6150

Optimal stabilization of constant power loads with input LC-filters

This contribution examines fundamental performance limitations of active stabilization of constant power loads with input LC filters. In terms of the load input admittance, stabilization is posed as a linear H∞ optimization problem, where the influence of stabilization on power control performance is minimized while meeting stability and robustness constraints. It is shown that the bandwidth of power control is upper limited by the resonance frequency of the input filter and that additional feedforward controllers can be used to individually shape reference tracking and disturbance rejection. Optimal results are verified through simulations using two different stabilization schemes.

Self-Synchronized Synchronverters: Inverters Without a Dedicated Synchronization Unit

A synchronverter is an inverter that mimics synchronous generators, which offers a mechanism for power systems to control grid-connected renewable energy and facilitates smart grid integration. Similar to other grid-connected inverters, it needs a dedicated synchronization unit, e.g., a phase-locked loop (PLL), to provide the phase, frequency, and amplitude of the grid voltage as references. In this paper, a radical step is taken to improve the synchronverter as a self-synchronized synchronverter by removing the dedicated synchronization unit. It can automatically synchronize itself with the grid before connection and track the grid frequency after connection. This considerably improves the performance, reduces the complexity, and computational burden of the controller. All the functions of the original synchronverter, such as frequency and voltage regulation, real power, and reactive power control, are maintained. Both simulation and experimental results are presented to validate the control strategy. Experimental results have shown that the proposed control strategy can improve the performance of frequency tracking by more than 65%, the performance of real power control by 83%, and the performance of reactive power control by about 70%.

Stability and Performance of Continuous-Time Power Control in Wireless Networks

This paper develops a comprehensive stability analysis framework for general classes of continuous-time power control algorithms under heterogeneous time-varying delays. Our first set of results establish global asymptotic stability of power control laws involving two-sided scalable interference functions, and include earlier work on standard interference functions as a special case. We then consider contractive interference functions and demonstrate that the associated continuous-time power control laws always have unique fixed points which are exponentially stable, even under bounded heterogeneous time-varying delays. For this class of interference functions, we present explicit bounds on the decay rate that allow us to quantify the impact of delays on the convergence time of the algorithm. When interference functions are linear, we also prove that contractivity is necessary and sufficient for exponential stability of continuous-time power control algorithms with time-varying delays. Finally, numerical simulations illustrate the validity of our theoretical results.

On The Stability of Generators Load Sharing

This paper deals with the dynamic performance of the active power control of two or more generators electrically connected in parallel, the average power control is used to enable the generators to share the load equally with constant speed.The new system suffered from instability due to the interaction between the different loops.Base on the multi-variable linear equivalent machine system model, the system was analyzed and its stability limits were obtained using MATLAB. The system was simulated using Simulink.A phase-lag network was introduced in the load sharers, and had a major effect on the stability of the system which enables the increase of the gain of the controllers without breaking into instability.

Distributed Generation in the Smart Grid – Case Study of Parintins

This work presents the results of the design phase of project on integration of distributed photovoltaic power generation into the smart grid (distribution level) in the city of Parintins, which is an 17 MW isolated diesel grid located in the State of Amazon, Brazil. PV power generation in isolated systems is economically attractive, as fuel cost of 650 R$/MWh are significantly above PV generation cost. Distributed generation may be implemented without occupying valuable land on the fluvial island.A literature review provides first the general concepts of distributed generation in smart grids. In a brief description the system design, technical data, telecommunication network structure and the smart metering & billing system of the first smart grid implemented in Brazil is given. Within this R&D project financed ANEEL (electric power regulatory body) a smart grid based performance monitoring and power control for PV systems has been developed. Impacts of distributed power in the LV network have been analyzed through power flow simulation. The smart grid infrastructure will be used to assess the impact of PV generation concentrated on selected feeders and to test smart grid control strategies for distributed generation.

Fuzzy logic control to improve the performance of the direct power control based DFIG

Purpose – A direct power control (DPC) of the doubly-fed induction generator (DFIG) is presented. A new method, which is based on the rotation of the space sector, clockwise or vice versa, is proposed to improve the performance of the switching table. Then, it is combined with a fuzzy system to have advantages of both rotation sector and fuzzy controller. The paper aims to discuss these issues. Design/methodology/approach – In this paper, a new DPC of the DFIG is presented. To improve the performance of the switching table, a new method is proposed. The method is based on the rotation of the space sector, clockwise or vice versa. The excellence of the proposed method is proven. Then, it is shown that the performance of the system can be enhanced by using a fuzzy logic controller. The rotation method is combined with a fuzzy system. Findings – Simulation shows that although sector rotation and fuzzy controller can improve the performance of the DFIG, a combination of both demonstrates a smoother response in order that reactive and active power ripples and THD of the injected current decrease in different speeds. Also, it is demonstrated that the proposed method is robust against parameters variations. However, a hardware experiment should be performed to be practically verified. Originality/value – A sector rotation is proposed and its effect on the performance of the DFIG is considered. A simple method to write rules table is presented and the performance of sector rotation and fuzzy controller on the DFIG is analysed.

Application of Sliding Mode Control for Wind Power Generation System

The wind power generation system have strong nonlinear characteristics with many uncertain factors, which was hard to be controlled exactly by traditional controllers and the sliding mode control was proposed, the sliding surface was selected, the equivalent controller and sweithcing controller was designed. The wind power generation system was analyzed and the mathematical models of aerodynamics, drive train and electromagnetic subsystem were created. The control strategy was applied into wind power generation system with MATLAB/Simulink platform, and the simulation result shows this model is of more important significance on researching the power characteristic and control performance for power generation system, the sliding mode control with high power tracking performance, which can effectively implement maximum energy capture.

QoS Guarantees and Service Differentiation for Dynamic Cloud Applications

Cloud elasticity allows dynamic resource provisioning in concert with actual application demands. Feedback control approaches have been applied with success to resource allocation in physical servers. However, cloud dynamics make the design of an accurate and stable resource controller challenging, especially when application-level performance is considered as the measured output. Application-level performance is highly dependent on the characteristics of workload and sensitive to cloud dynamics. To address these challenges, we extend a self-tuning fuzzy control (STFC) approach, originally developed for response time assurance in web servers to resource allocation in virtualized environments. We introduce mechanisms for adaptive output amplification and flexible rule selection in the STFC approach for better adaptability and stability. Based on the STFC, we further design a two-layer QoS provisioning framework, DynaQoS, that supports adaptive multi-objective resource allocation and service differentiation. We implement a prototype of DynaQoS on a Xen-based cloud testbed. Experimental results on representative server workloads show that STFC outperforms popular controllers such as Kalman filter, ARMA and, Adaptive PI in the control of CPU, memory, and disk bandwidth resources under both static and dynamic workloads. Further results with multiple control objectives and service classes demonstrate the effectiveness of DynaQoS in performance-power control and service differentiation.

Channel Estimation with Optimal Power Controls in Amplify-and-Forward Relay Networks

In this paper, we present a power control method of relay for improving a channel estimation performance in amplify-and-forward (AF) relay networks over frequency-selective fading channel. We first analyze a channel mean-square error (MSE) by imposing a power control effect on a simple (LS) channel estimation. Then, we find that there is a trade-off between the amplitude of power control and MSE performance. Moreover, we propose the optimal and suboptimal power control methods in order to resolve such a trade-off. Finally, the superiority of the proposed channel estimation with optimal power controls is verified through numerical simulations.