Control Strategy Of Generator Research Articles

Research on the virtual synchronous generator control strategy of grid-connected permanent-magnet direct-driven wind power system

Renewable energy, distributed generation, and micro-grid technology have been widely concerned for a long time. The traditional grid-connected inverter control strategy does not take into account the problem of inertia which is short and fast to cause the frequency change. The virtual synchronous generator control strategy is adopted to simulate the synchronous generator characteristics, which enhanced the inertia and damp of the system. For the micro-grid of wind power grid-connected, the storage battery is arranged on the AC side of the permanent magnet direct-drive wind turbine, and the model of the virtual synchronous generator is established. Thus the grid-connected performance of large-scale wind farm is improved. Here, the effect of moment of inertia in the virtual synchronous generator and the grid-connected regulation of virtual synchronous generator are verified by using PSCAD/EMTDC. The simulation results show that the grid-connected inverter controlled by the virtual synchronous generator is approximately equivalent to the synchronous generator in external characteristic. The grid-connected inverter based virtual synchronous generator control has a beneficial to adjust frequency and voltage, and can enhance the standby inertia of new energy and grid power generation

PV-based virtual synchronous generator with variable inertia to enhance power system transient stability utilizing the energy storage system

The Photovoltaic (PV) plants are significantly different from the conventional synchronous generators in terms of physical and electrical characteristics, as it connects to the power grid through the voltage-source converters. High penetration PV in power system will bring several critical challenges to the safe operation of power grid including transient stability. To address this problem, the paper proposes a control strategy to help the PVs work like a synchronous generator with variable inertia by energy storage system (ESS). First, the overall control strategy of the PV-based virtual synchronous generator (PV-VSG) is illustrated. Then the control strategies for the variable inertia of the PV-VSG are designed to attenuate the transient energy of the power system after the fault. Simulation results of a simple power system show that the PV-VSG could utilize the energy preserved in the ESS to balance the transient energy variation of power grid after fault and improve the transient stability of the power system.

Low-Complexity Distributed Predictive Automatic Generation Control With Guaranteed Properties

An automatic generation control scheme for multi-area power systems is presented, based on the technique of distributed model predictive control (MPC). Local area controllers solve nested MPC problems in order to regulate states to steady values, and reject the disturbances induced by tie-line interactions. The approach achieves guaranteed constraint satisfaction, recursive feasibility of the MPC problems and stability, while maintaining on-line complexity similar to conventional MPC. A rigorous off-line design methodology is given for selecting controller parameters, and is demonstrated on an example 4-area system.

Multiarea Deregulated Automatic Generation Control Scheme of Power System Using Imperialist Competitive Algorithm Based Robust Controller

ABSTRACTThis paper is focused on design and application of proportional integral derivative (PID) controller for deregulated multiarea automatic generation control (AGC) scheme utilizing the imperialist competitive algorithm (ICA) under various electricity market transactions. A multiarea hydro thermal 75-bus real power system is considered as a test system for deregulated AGC scheme. Simulation study results demonstrate the effective performance of controller on various load disturbance scenarios. The performance of ICA-tuned PID controller is also compared with genetic algorithm (GA)-tuned PID controller. The comparative results show that ICA–PID controller has higher convergence rate, smaller settling time, reduced oscillations than GA-tuned PID controller, i.e. reaching to better solution. Robustness of ICA–PID controller is also checked to determine its response towards system parameters uncertainties through sensitivity analysis. It is seen that the performance of PID controller tuned by ICA algorithm is robust for the system parameter uncertainties while GA–PID controller performance degrades.

Primary Frequency Regulation With Load-Side Participation—Part I: Stability and Optimality

We present a method to design distributed generation and demand control schemes for primary frequency regulation in power networks that guarantee asymptotic stability and ensure fairness of allocation. We impose a passivity condition on net power supply variables and provide explicit steady-state conditions on a general class of generation and demand control dynamics that ensure convergence of solutions to equilibria that solve an appropriately constructed network optimization problem. We also show that the inclusion of controllable demand results in a drop in steady-state frequency deviations. We discuss how various classes of dynamics used in recent studies fit within our framework and show that this allows for less conservative stability and optimality conditions. We illustrate our results with simulations on the IEEE 68-bus transmission system and the IEEE 37-bus distribution system with static and dynamic demand response schemes.

Research on the control strategy of distributed energy resources inverter based on improved virtual synchronous generator

This paper focus on the power fluctuations of the virtual synchronous generator(VSG) during the transition process. An improved virtual synchronous generator(IVSG) control strategy based on feed-forward compensation is proposed. Adjustable parameter of the compensation section can be modified to achieve the goal of reducing the order of the system. It can effectively suppress the power fluctuations of the VSG in transient process. To verify the effectiveness of the proposed control strategy for distributed energy resources inverter, the simulation model is set up in MATLAB/SIMULINK platform and physical experiment platform is established. Simulation and experiment results demonstrate the effectiveness of the proposed IVSG control strategy.

Behavior Modeling and Auction Architecture of Networked Microgrids for Frequency Support

As intermittent generation profiles introduce more stress due to the sudden imbalance in supply and demand, power systems are becoming more dependent on online aggregated support of networked utility-independent private microgrids. During the aggregation process, microgrid operators’ preferences and bidding behaviors are priority. New aggregation approaches are required considering the individual behaviors of the networked and geographically dispersed independent microgrids. In this paper, we present a novel bidding behavior modeling and an auction architecture consisting of a central aggregator and networked microgrid agents. The bidding behavioral states of the microgrid agents are formalized as partially observable Markov processes for the belief updates and short-term policy determination in order to maximize the individual profit. A reverse auction model is adopted to enable competitive negotiations between the central aggregator and networked microgrid agents. The auction and aggregation processes were implemented in a power system control area along with an automatic generation control (AGC) scheme to contribute frequency control. The proposed AGC and auction mechanism were verified with an industrial multi-agent framework in a laboratory-based real-time application.

Primary frequency regulation in power networks with ancillary service from load-side participation

We consider the problem of designing distributed generation and demand control schemes that provide ancillary service in primary frequency regulation in power networks such that stability and fairness in the power allocation can be guaranteed. It is desirable in such schemes that load side participation in frequency control is activated only when the frequency exceeds prescribed thresholds so as to avoid frequent intervention in the operation of loads. This, however, leads to nonlinear control schemes with vector fields with discontinuous derivatives. In this paper, we investigate how stability and optimality may be ensured when such dynamics are considered. We show that subgradient methods can be used to derive decentralised conditions that ensure optimality of the equilibrium points. Decentralised conditions for asymptotic stability that are valid in this context are also provided. We illustrate our results with simulations on the IEEE 68 bus system, where it is demonstrated that the inclusion of controllable loads offers improved transient behaviour and that an optimal power allocation among controllable loads is achieved.

Factorial Based Stochastic Optimization Approach for Energy and Environmental Systems Management Under Uncertainty

Abstract In this study, an optimization programming based on inexact stochastic method and factorial design was proposed to support management of energy and environmental systems under uncertain conditions. It could be used for analyzing various policy scenarios associated with different levels of economic penalties when promised targets are violated. Moreover, it can obtain optimal decisions of primary energy supply, electricity, and thermal power generation, capacity expansion, and emission control scheme. The developed model has been applied to a case study within a multifacility, multiperiod, and multidemand-level context to demonstrate the feasibility of the proposed methodology. Factorial method has been used for sensitivity analysis to address the interactive uncertainties in modeling parameters, as well as providing a trade-off analysis between the economic objective and the relevant energy and environmental policies. The generated approach will be able to reflect dynamic complexities in energy an...

Decentralised power sharing control strategy in LV microgrids under unbalanced load conditions

In this paper, a decentralized control strategy for inverter-based distributed generation (DG) is proposed to enhance the accuracy of power sharing under unbalanced load conditions in low-voltage microgrids. The proposed method includes two important saliences: (1) accurate unbalanced current injection from DGs, and (2) reduction of circulating real and reactive powers in an islanded microgrid. The features are complied with the proposed droop strategy utilized in the control system of each phase of DG converters. Based on the proposed triple-droop control strategy, the real power sharing in an AC low-voltage microgrid is significantly improved via P–V control strategy and the reactive power sharing accuracy is enhanced via Q–f control strategy. By this method, the amplitude of the output voltage of each phase of the converters is determined based on the amount of load connected to that phase. In addition, the efficiency of the microgrid is increased due to the circulating current reduction between DGs. A virtual impedance concept is also utilized to improve the accuracy of the proposed power sharing method. The feasibility and effectiveness of the proposed strategy are validated using MATLAB/SIMULINK software for International Council for Large Electric Systems (CIGRE) low-voltage distribution network benchmark.

ARMC-AGC strategy for multi-area optimal cooperation to cover the variability of renewable energy resources

The integration of large-scale variable renewable energy (VRE) has increased the demand for additional regulation capacity to manage the variability of renewable generation. This problem can be solved by exploiting regulation flexibility from neighboring areas; however, this solution is restricted by the existing automatic generation control (AGC) strategy. In this paper, an AGC strategy based on the area regulation marginal cost is presented for multi-area AGC optimal cooperation. A multi-area system dynamic model for AGC is improved, and the formulation of the multi-area AGC optimal cooperation model considering tie-line power security, which is the objective of the proposed control strategy, is developed. Next, the stability and optimality of the proposed strategy are studied based on the linear theory. Finally, comparative simulations based on a simple three-area system show that the proposed strategy is effective in enabling further VRE penetration and can improve the economic efficiency of regulation in multi-area power systems. A case study using a real multi-area power system demonstrates the benefits of the proposed strategy in practice.

Application of fractional order PID controller for AGC under deregulated environment

In this paper, a fractional order proportional integral derivative (FOPID) controller for multiarea automatic generation control (AGC) scheme has been designed. FOPID controller has five parameters and provides two additional degrees of flexibility in comparison to a proportional integral derivative (PID) controller. The optimal values of parameters of FOPID controller have been determined using Big Bang Big Crunch (BBBC) search algorithm. The designed controller regulates real power output of generators to achieve the best dynamic response of frequency and tie-line power on a load perturbation. The complete scheme for designing of the controllers has been developed and demonstrated on multiarea deregulated power system. The performance of the designed FOPID controllers has been compared with the optimally tuned PID controllers. It is observed from the results that the FOPID controller shows a considerable improvement in the performance as compared to the conventional PID controller.

Enhanced Virtual Synchronous Generator Control with Fuzzy Logic Controller for Parallel Inverters in Microgrids

Objective: To reduce the power oscillations and also to provide accurate active power and reactive power sharing. Methods: In this paper enhanced Virtual Synchronous Generator (VSG) control strategy along with Fuzzy Logic Controller (FLC) is employed for parallel inverters in microgrids. It deals with design of the system and simulation results shows the improvement obtained through it. Findings: By using enhanced VSG control, the oscillation damping and proper transient active power sharing are achieved by adjusting the virtual stator reactance and also accurate reactive power sharing is achieved based on inversed voltage droop control. Furthermore, FLC is used as suitable controllable mechanism (which was PI in basic VSG) for controlling the parallel inverters in microgrids with which power oscillations are further damped and accurate active and reactive power sharing are achieved. The simulation results prove that the proposed method is better than the basic VSG for parallel inverters in microgrids. Application: This scheme is used for control of inverters in distributed source environments. This is essential for the operation of large AC systems, where distances between inverters make communication impractical. Use of multilevel inverters or an adaptive neuro-fuzzy inference system (ANFIS) can be considered as improvement for this paper. Keywords: Distributed Power Generation, Droop Control, Fuzzy logic controller, Microgrids; Reactive Power Control, Virtual Synchronous Generator Control1.

Improved power decoupling control strategy based on virtual synchronous generator

Virtual synchronous generator (VSG) control scheme, which can be regarded as an extension of droop control, has received much attention from researchers as the introduction of rotational inertia to inverters. This study discusses an active and reactive power decoupling technique for VSGs in microgrid, as an important aspect of VSG. The traditional power decoupling mechanism is initially analysed. Subsequently, the properties of the line impedance at different voltage degrees are compared. Results indicate that the traditional power decoupling method is unsuitable for medium- and low-voltage microgrids. Thus, an improved power decoupling method is proposed. By estimating the voltage at the point of common coupling and tracking their reference values, the output active and reactive power of inverters can perform dynamic decoupling. Furthermore, the stability of the new control structure and selection of relevant coefficients are analysed. The simulation and experimental results verify the enhanced decoupling strategy for VSGs.

Modeling and Maximum Power Point Tracking Control of Wind Generating Units Equipped with Permanent Magnet Synchronous Generators in Presence of Losses

This paper focuses on the modeling of wind turbines equipped with direct drive permanent magnet synchronous generators for fundamental frequency power system simulations. Specifically, a procedure accounting for the system active power losses to initialize the simulation starting from the load flow results is proposed. Moreover, some analytical assessments are detailed on typical control schemes for fully rated wind turbine generators, thereby highlighting how active power losses play a fundamental role in the effectiveness of the wind generator control algorithm. Finally, the paper proposes analytical criteria to design the structure and the parameters of the regulators of the wind generator control scheme. Simulations performed with Digsilent Power Factory validated the proposed procedure, highlighting the impact of active power losses on the characterization of the initial steady state and that the simplifying assumptions done in order to synthesize the controllers are consistent with the complete modeling performed by the aforementioned power system simulator.

On-Road Path Generation and Control for Waypoints Tracking

This article addresses path generation and predictive control for waypoints tracking. By considering irregularity of waypoints given by the leading vehicle, the waypoints-following vehicle is made to track a clothoid path that assures safe and comfortable driving while keeping track of the waypoints in the least squares sense. In the generation of such a clothoid path, the path generation scheme utilized the clothoidal constraint and weighted least squares curve fitting. Predictive control is applied to improve path tracking performance over horizon, with constraints on steering and its rate being considered for safe and comfortable steering. A computational experiment, utilizing a set of leading vehicle generated waypoints on a highway, is conducted to demonstrate utility of the path generation and predictive control scheme.

Power Control of Low Frequency AC Transmission Systems Using Cycloconverters with Virtual Synchronous Generator Control

This paper is focused on the application of a multi-terminal line-commutated converter-type low frequency AC transmission system (MTLF) using a cycloconverter by applying a new power control scheme for multi-terminal operation. With the virtual synchronous generator (VSG) control scheme, the transmitting power among the multi-terminal system can be accomplished without a communication link for frequency synchronization in each terminal. The details of the proposed control scheme are explained in order to understand the advantages of this method. The configuration of a two-phase low frequency AC transmission system (LFAC) is adopted to examine with the proposed control scheme. Simulation results are provided to illustrate the proposed control scheme with respect to the LFAC system’s performance.

Collaborative Practical Oriented Independent Variable Pitch Control Strategy for Wind Power Generation

Collaborative Practical Oriented Independent Variable Pitch Control Strategy for Wind Power Generation

A Novel Dual-Winding BLDC Generator–Buck Converter Combination for Enhancement of the Harvested Energy From a Flywheel

This paper proposes a novel flywheel energy storage system which results in up to 20% enhancement in the harvested energy from the flywheel, in comparison with the existing schemes. Generally, boost converters are used for boosting the voltage in such systems. Major limitation of a boost converter is the dependency of its maximum achievable voltage gain on the ratio of its source resistance to load resistance which limits the amount of harvested energy from a flywheel and lowers the efficiency at low input voltages. The proposed scheme uses a novel and unique combination of dual armature winding permanent-magnet brushless dc machine and a buck converter to maintain the dc-bus voltage to overcome the limitations of the boost converter. Further, the new scheme helps in reducing the armature current loading on the machine to a large extent when it is being used as a generator. A detailed study has been carried out and the effect of generator winding configurations and control strategies adopted in the proposed scheme are analyzed. The proposed scheme is simulated using MATLAB/SIMULINK software. A hardware prototype having 1.0 kW/200 V rating has been built. The theoretical and experimental results are found to be in agreement.

A Power Sharing Method for Parallel Inverters with Virtual Synchronous Generator Control Strategy

<p>A new power sharing method of a virtual sychronous generator control based inverters is introduced in this paper. Since virtual synchronous generator has virtual inertia and damping properties, it significantly enhances the grid stability. However, its output power considerably affects by the line impedance. Thus, in this paper, the relation between the droop control and the line impedance is analyzed at first. Then, by appling an improved droop control strategy to an inverter based on the virtual sychronous generator control, achieving proportional active and reactive power sharing unaffected by the line impedance is realized. The result shows that a smooth response is achieved. As well as, the voltage drop caused by the line impedance is totally compensated. As a result, the system stability is furtherly improved. At last, the effectiveness of the proposed method is verified through MATLAB/Simulink.</p>