Frequency regulation of a RES integrated power system with AC/DC parallel link employing a fuzzy tuned fractional order controller

This paper demonstrates the operational efficacy of a newly proposed fuzzy tuned fractional order controller to offer an improved frequency regulation of a multi area renewable energy source (RES) integrated nonlinear power system. The effect of governor dead band nonlinearity and generation rate constraint of hydro and thermal power plants are considered in the system. Moreover, a proposed appropriate High voltage direct current (HVDC) tie line model is incorporated in this work, to verify the frequency deviation. Different test cases are applied to verify the robustness of the controllers on frequency response. The superiority of the proposed controller upon Proportional integral and derivative (PID), fuzzy logic controller and fuzzy PID controller in minimizing frequency deviation has been verified through MATLAB SIMULINK environment.

A Design Methodology for EV-WPT Systems to Resonate at Arbitrary Given Bands

Due to the effects of splitting frequency and cross coupling, the resonant frequency of the WPT system usually deviates from the given frequency band, and the system operating at the given frequency band suffers a very low output power. Ensuring that electric vehicle wireless power transfer (EV-WPT) systems operate at a resonant state is the prerequisite for efficient energy transfer. For this purpose, a novel design method by manipulating the eigenstate parameters is proposed in this paper. The proposed system can make a EV-WPT system with arbitrary coil successfully to resonate at any given bands, not just a single band. Therefore, the method designed in this article cannot only eliminate the problem of low power caused by frequency deviation, but also realize the application requirements of multiple frequency bands. Firstly, this article establishes an accurate state space model of an n-coil fully coupled EV-WPT system, and after that, the analytical current response on each circuit is derived. Based on that, a detailed frequency spectrum analysis is presented, along with several essential spectrum parameters’ derivations, including center frequencies and bandwidths. Then, with the center frequency and bandwidth as the design indexes, a novel methodology of designing to make EV-WPT systems achieve resonant-state at arbitrary given bands is derived. Finally, simulation and experimental verification are carried out. Simulation and experimental results show that whether it is a single-band or multi-band system, the accuracy of the value under designed resonant frequency is less than 0.01, which can effectively eliminate the frequency deviation phenomenon and obtain the maximum power output at the given frequency band.

Enhanced Inertial Response Capability of a Variable Wind Energy Conversion System

An inertial response emulated control strategy of doubly-fed induction generators (DFIGs) is able to arrest their frequency decline following a severe frequency event. Nevertheless, the control coefficient is unchanged, so as to limit the benefit potentiality of improving the inertial response capability for various disturbances and provide less of a benefit for boosting the frequency nadir. This paper addresses an enhanced inertial response emulated control scheme for a DFIG to improve the maximum frequency deviation and maximum rate of change of frequency for various disturbances. To this end, the control coefficient is coupled with the system frequency deviation so as to regulate the control coefficient according to the system frequency deviation (i.e., sizes of the disturbance). Results clearly indicate that the proposed inertial response emulated control strategy provides better performance in terms of improving the maximum rate of change of frequency and maximum frequency deviation under various sizes of disturbance and random wind speed conditions.

Power Sharing and Control Strategy for Provisionally Coupled Microgrid Clusters through an Isolated Power Exchange Network

The two common mechanisms of load-shedding and renewable curtailment can prevent provisional overloading and excessive generation and the subsequent unacceptable voltage and frequency deviation in standalone microgrids (MGs), which makes MGs less resilient and reliable. However, instead of enabling load-shedding or renewable curtailment, such overloading or over-generation problems can be alleviated more efficiently and cost-effectively by provisionally interconnecting the neighboring MGs to exchange power amongst themselves. In such a scheme, the interconnected MGs can supply their local demand, as well as a portion of the demand of the adjacent MGs. In order to implement this strategy, a three-phase ac link can be used as the power exchange network, while each MG is coupled to the link through a back-to-back power electronics converter, in order to maintain the autonomy of each MG if they are eachoperated under different standards. This paper proposes a suitable decentralized power management strategy without a communication link between the MGs to achieve power-sharing amongst them and alleviate unacceptable voltage and frequency deviation along with the required control technique for the power electronic converters, which can be implemented at the primary level based on the measurement of the local parameters only. To this end, one of the converters should always regulate the dc link voltage while the other converter should operate in droop control mode when the MG is healthy and in constant PQ mode when overloaded or over-generating. Suitable status detection and mode transition algorithms and controllers were also developed and are proposed in this paper. The performance of the proposed power exchange and control mechanisms were evaluated and verified via PSIM®-based numerical simulation studies. The stability and sensitivity of the proposed power exchange topology are also analyzed against several critical design and operational parameters.

An optimization method of clock synchronization for large-scale regional power network based on IEEE 1588

At present, mobile devices generally use GPS, Beidou and other satellite time service methods to obtain time, but the clock synchronization based on IEEE 1588 protocol still has deviation. To solve this problem, a clock synchronization method is proposed to improve IEEE 1588 protocol. Based on the analysis of IEEE 1588 protocol, the clock deviation and frequency deviation which affect the synchronization accuracy are modeled. The second-order Kalman filtering algorithm is used to recursively deduce the clock deviation and frequency deviation, and the Allan variance is used to verify the noise characteristics and constantly correct the clock deviation. Finally, the improved effect is verified by relevant experiments. The results show that the improved system can improve the synchronization accuracy.

Multi-Objective Decentralized Model Predictive Control for Inverter Air Conditioner Control of Indoor Temperature and Frequency Stabilization in Microgrid

Microgrid (MG) is a novel concept for a future distribution power system that enables renewable energy sources (RES). The intermittent RES, such as wind turbines and photovoltaic generators, can be connected to the MG via a power electronics inverter. However, the inverter interfaced RESs reduce the total inertia and damping properties of the traditional MG. Consequently, the system exhibits steeper frequency nadir and the rate of change of frequency (RoCoF), which may degrade the dynamic performance and cause the severe frequency fluctuation of the system. Smart loads such as inverter air conditioners (IACs) tend to be used for ancillary services in power systems. The power consumption of IACs can be regulated to suppress frequency fluctuation. Nevertheless, these IACs, regulating power, can cause the deviation of indoor temperature from the temperature setting. The variation in indoor temperature should be controlled to fulfill residential comfort. This paper proposes a multi-objective decentralized model predictive control (DMPC) for controlling the power consumption of IACs to reduce MG frequency fluctuation and control the variation in indoor temperature. Simulation results on the studied microgrid with the high penetration of wind and photovoltaic generator demonstrate that the proposed DMPC is able to regulate frequency deviation and control indoor temperature deviation as a user preference. In addition, the DMPC has a superior performance effect to the proportional-integral (PI) controller in terms of reducing frequency deviation, satisfying indoor temperature preferences, and being robust to the varying numbers of IACs.

Research of metrological capabilities of digital (DDS- and Trueform-) generators

One of the fundamental improvements of the measurement standard of frequency deviation of frequency-modulated oscillations was the replacement of analog frequency-modulated generators used in DETU 09-03-95 with digital ones based on the principle of direct digital synthesis (DDS) and its next version of Trueform technology. These generators have wider ranges of frequency deviation and modulation frequencies than analog ones, but nonlinear distortion laws of the frequency modulation are not standardized. The subject of the article is the development of methods and research of these generators and frequency-modulated signals generated by them for nonlinear distortions, accompanying amplitude modulation, frequency noise. Three methods were used in the study: direct measurement; “combination frequencies” and “frequency shift”. The experiment was performed using several measurement methods, which allowed to estimate very small values of nonlinear distortion. Methods were developed and experimental estimations of concomitant amplitude modulation of DDS-generators (in frequency modulation mode), as well as their frequency noise level, were performed. An experimental evaluation of the capabilities of the analog-digital demodulator of the R&S FSL6 spectrum analyzer with the K7 option was performed, its high linearity was shown, its capabilities with respect to the frequency ranges of carrier oscillations and frequency deviation were evaluated. The research results provide a basis for the method of calibration of DDS-generators and demodulator of spectrum analyzers with the K7 option in those ranges where their parameters are not normalized (at direct current up to 8 MHz and F up to 500 kHz).

AGC Including ELD and Emission Coordination Using Sine Cosine Algorithm

The aim of conventional AGC is to regulate the demand load of the area with taking into account the sharing power with the others area and also the frequency deviation and tie-line power deviation within minimum error steady-state. The proposed coordination's goal is to regulate the demand load between the interconnected area when taking into account the optimal dispatch and emission effect. The two-area that be consist of three units in each one (hydro, thermal, and gas) is used of proposed system. The optimization algorithms were used to find the best operating point of the system by tuning the integral gain are located in ACE that named primary control and Generation allocation logic named secondary controller. The Particle Swarm Optimization (PSO) and Sine Cosine Algorithm (SCA) are used to tune gains of the integral (I) controller to show the superiority in identifying robust controller. The simulation results prove that the SCA with proposed coordination is very effectiveness as compared with PSO algorithm in enhance the dynamic performance and reduce overshoot, maximum frequency deviation, and net tie line power flow deviation error for a given load change and disturbed the demand load between two-area as economic.

An Adaptive Sliding Mode Control Based on Disturbance Observer for LFC

In the power system, the loads and nonlinearity parameters cause the system frequency deviation, which complicates the load frequency control (LFC). To deal with the above problem, an adaptive sliding mode control (SMC) based on disturbance observer is proposed to eliminate frequency deviation for interconnected power system in this paper. Firstly, the mathematical model of the power system is established, where the power exchange between the tie line is considered as the variable of the designed sliding surface. Secondly, the nonlinear disturbance observer is constructed to estimate the parameter uncertainty and load of power system. Thirdly, combined with the estimated value of the disturbance observer and integral sliding mode surface, the SMC is designed. Moreover, considering the inherent shortcoming of SMC—the chattering problem, an adaptive strategy is applied to the SMC to ensure the stability of controller. Next, the stability of the designed SMC is proved by Lyapunov stability theory. Finally, to verify the effectiveness of the proposed controller, several simulations are presented.