Analysis of Synchronous Generators’ Local Mode Eigenvalues in Modern Power Systems

For improving electric power system stability, synchronous generators in power systems are generally equipped with controllers such as AVR, PSS, and GOV. Since the various oscillation modes occur according to system conditions, these fixed parameter controllers deteriorate the control performance. We propose the adaptive power system stabilizer (PSS) using frequency domain analysis for improving electric power system transient stability. In the proposed method, at first, the frequency components of the generator's swings are detected by online FFT. The conventional PSS parameters are tuned online by the fuzzy logic technique based on the frequency domain analysis. We verify that the proposed adaptive PSS using frequency domain analysis can damp the generator's swings effectively.

The Field Tests on Power System Stabilizers for Damping Low Frequency Oscillation

The amount of wind power generation is rapidly increasing. These wind power generators will replace traditional synchronous generators in power systems. Therefore, modern wind turbines must have the similar characteristics of governor and exciter in a traditional synchronous generator to control the real or reactive power outputs by wind turbines. Then, the frequency or voltage stability of a power system can be maintained. In recent years, many studies have proposed various control methods for frequency or voltage regulations, and these methods have different advantages and disadvantages. Thus, this paper will investigate typical and representative control methods for frequency or voltage regulation by wind turbines, and reveal the main principles and key technologies of these methods. Moreover, this paper will provide the future trend about frequency and voltage controls by wind turbines.

Pole–zero placement based feed-forward damping control for virtual synchronous generators in power systems with inverter-based resources

In this paper we extend the energy-shaping controller design technique, which has been successfully used for single-loop excitation regulation of synchronous generators in power systems, to the exciter–governor dual configuration. As in the simpler excitation problem, the aim of the controller is to shape the total energy function via modification of the energy transfer between electrical and mechanical subsystems—but in this dual scenario we also have to take into account the energy contribution of the governor control loop dynamics. Motivated by practical considerations we also present a partial state feedback version of the controller that is derived applying thoe immersion and invariance technique recently reported in the literature. Representative simulations show how the tuning parameters effectively shape the domain of attraction of the desired stable equilibrium enhancing the transient stability of the power system.

Control of Synchronous Generators in Power Systems

A new method for loss of excitation protection of synchronous generators in the presence of static synchronous compensator based on the discrete wavelet transform

As more and more power electronic based generation units are integrated into power systems, the stable operation of power systems has been challenged due to the lack of system inertia. In order to solve this issue, the virtual synchronous generator (VSG), in which the power electronic inverter is controlled to mimic the characteristics of traditional synchronous generators, is a promising strategy. In this paper, the representation of the synchronous generator in power systems is firstly presented as the basis for the VSG. Then the modelling methods of VSG are comprehensively reviewed and compared. Applications of the VSG in power systems are summarized as well. Finally, the challenges and future trends of the VSG implementation are discussed.

Power system security is the power system’s capability to maintain its stability when a disturbance occurs. Transient instability is a phenomenon that threatens the security of the power system and synchronous generators. When rotor angle instability occurs in a synchronous generator, it is capable of driving the generator O.S. If the O.S operation of a generator sustains even for a brief period of time, it may result to serious mechanical and thermal damages to the machine. Therefore, faster identification of such conditions and in time isolation of the unstable generator from the power system is necessary for keeping the power system safe. Conventional methods for the identification of the generator O.S is based on the use of impedance relays. The purpose of this chapter is the prediction of the generator O.S with dynamic data of generator and power system, which can be gathered by PMUs in the fault and clearance period. Generator dynamic information includes variations of voltage phasor, active and reactive power, rotor angle, and speed of generator as well as the data of voltage and line flows in the adjacency of the generator that are collected in different time intervals. The measured information is continually updated in the moving window and with a special algorithm such as a three-step DT that performs the detection fault occurrence and clearance and prediction of O.S of generators. The proposed algorithm is working constantly as a relay, and the proposed algorithm recognizes the stability of the generator whenever changes occur in the generator parameter according to the severity of variations. Since training data perform an effective role in DT learning or other machine learning methods, to increase the learning ability of DT, training samples are prepared for having complete coverage of almost all load levels and different operation points. The proposed scheme is implemented on the generator of the IEEE 39-bus system with promising results.

Self‐synchronization of a dual‐excited synchronous generator in power systems

Renewable power systems dynamic security using a new coordination of frequency control strategy based on virtual synchronous generator and digital frequency protection

The increase in variable renewable generators (VRGs) in power systems has altered the dynamics from a historical experience. VRGs introduce new sources of power oscillations, and the stabilizing response provided by synchronous generators (SGs, e.g., natural gas, coal, etc.), which help avoid some power fluctuations, will lessen as VRGs replace SGs. These changes have led to the need for new methods and metrics to quickly assess the likely oscillatory behavior for a particular network without performing computationally expensive simulations. This work studies the impact of a critical dynamical parameter-the inertia value-on the rest of a power system's oscillatory response to representative VRG perturbations. We use a known localization metric in a novel way to quantify the number of nodes responding to a perturbation and the magnitude of those responses. This metric allows us to relate the spread and severity of a system's power oscillations with inertia. We find that as inertia increases, the system response to node perturbations transitions from localized (only a few close nodes respond) to delocalized (many nodes across the network respond). We introduce a heuristic computed from the network Laplacian to relate this oscillatory transition to the network structure. We show that our heuristic accurately describes the spread of oscillations for a realistic power-system test case. Using a heuristic to determine the likely oscillatory behavior of a system given a set of parameters has wide applicability in power systems, and it could decrease the computational workload of planning and operation.

Based on the integrated design and airworthiness verification of civil aircraft system, this paper completes the simulation modeling and fault modeling of aircraft electrical system. The aircraft electrical system is constructed in the form of dual generators and dual-channel power supply. The main power supply adopts the three-stage power generation system, the auxiliary power supply system uses the permanent magnet synchronous power generation system and a battery. The transmission and distribution system is responsible for the electrical power conversion and the logic control in the system fault-pattern. The simulation results show that the system is reasonable and effective, which provides a reference for the optimal design and control of the actual aircraft electrical system.

An optimal transient controller for a synchronous generator in a multi-machine power system is designed using the concept of flatness-based feedback linearization in this paper. The computation of the flat output and corresponding controller for reduced order model of the synchronous generator is presented. The required feedback gains used to close the linearization loop is optimized using particle swarm optimization for maximum damping. Typical results obtained for transient disturbances on a two-area, four-generator power system equipped with the proposed controller on one generator and conventional power system stabilizers on the remaining generators are presented. The effectiveness of the flatness-based controller for multi-machine power systems is discussed.

The number of synchronous generators is anticipated to be reduced in the future power systems. Factors such as favorable government policies and market's preference are driving enormous deployment of renewables, while there is very little interest in replacing coal fired power stations by the same type of power generators. These have culminated in the increased deployment of asynchronous generators in power systems. While these types of generators are environmentally friendly, they perform poorly in maintaining power system strength. This paper investigates the impact of photovoltaic (PV) generator on fault level as an indicator of system strength of a network. Various technological options for system strength improvement are discussed. It shows that system fault level can be supported by independent control of synchronous condenser's voltage and reactive power control. The paper also formulates an analytical control approach and demonstrates its suitability on a modified 35-bus utility system.