Zhou Yang

Bio: Zhou Yang is an academic researcher from Huazhong University of Science and Technology. The author has contributed to research in topic(s): Electric power system & Power system simulation. The author has an hindex of 3, co-authored 3 publication(s) receiving 30 citation(s).

Study of Coherency-based Dynamic Equivalent Method for Power System with HVDC

Abstract: In order to reduce the calculation amount of numerical simulation in transient analysis for large-scale power system, the network can be simplified by dynamic equivalence. This paper presents the coherency-based equivalent technique for power system with HVDC. Both frequency-domain method and weighting method are comprehensively used in parameter aggregation section in this paper. The adaptability of ac system equivalence to dc system is concerned, and the accuracy of dynamic equivalence of ac system is estimated using dc system disturbance. In numerical simulator PSASP, a dynamic equivalence of EPRI 8-machine 36-bus ac/dc hybrid power system can be derived, in which the specific model of HVDC system is considered. The comparisons of steady-state and dynamic response of original and equivalent system show that the dynamic equivalent model is feasible and available.

A real-time dynamic equivalent solution for large interconnected power systems

Abstract: Dynamic equivalent has been a basic approach for analysis and computation of large scale-increasing interconnected power systems in China. Security defense of power systems and real-time monitoring of system states require more rapid and effective computation of large power grids. This paper introduces a solution for real-time dynamic equivalent of large multi-area power systems. It is based on real-time measurement data from Wide Area Measurement System and parameter identification. A parallel dynamic equivalent model composed of an equivalent generator and an equivalent synthesis load was put forward, in which the equivalent generator uses a 3rd order electromechanical transient model with damping while the equivalent synthesis load uses a static characteristic model considering both voltage and frequency. Identifiability analysis was carried out for this nonlinear dynamic equivalent model. In order to apply Laplace transformation-transfer function method, the model was firstly linearized. Particle Swarm Optimization algorithm was utilized for parameter identification of the dynamic equivalent model. For AC power systems, this model is verified on CEPRI 8-machine 36-bus example system. Load model and the style of disturbance are two remarkable factors that relate to the stability of the whole power system, which are fully considered in this paper. The simulation results show that the dynamic equivalent model can reflect the dynamic responses and the transient stability of the original system, no matter which is transient stable or unstable, angle unstable or voltage stable. When we change the load model in the original system, the static characteristic model with both voltage and frequency factors can throughout represents the dynamic behavior of the original system, which confirms its robustness of this dynamic equivalent model. All the simulation work was performed on PSASP.

Study of Power System Online Dynamic Equivalent Based on Wide Area Measurement System

Abstract: Dynamic equivalent can largely reduce the calculation amount for cross-area interconnected power systems. It is fundamental work and an effective approach for dynamic analysis of large power systems. Online dynamic security analysis needs real-time calculation of dynamic equivalents. Wide area measurement system supplies a good support for realizing possible real time dynamic equivalent. One way is based on coherency equivalent theory and to use plenty of history data from measurements to obtain coherency information of generators offline and match the dynamic equivalents through real-time measurements. The other way is based on parameter and model identification. A dynamic equivalent model of a parallel of equivalent generator and load was put forward. The identifiability of equivalent model and the identification algorithm of parameters were briefly discussed. Test on EPRI 8-machine 36-bus system shows that dynamic equivalent model of external system can reflect the dynamic behaviors of the original system accurately.

Identification of dynamic equivalents based on heuristic optimization for smart grid applications

Abstract: Vulnerability assessment is one of the main tasks in a Self-Healing Grid structure, since it has the function of detecting the necessity of performing global control actions in real time. Due to the short-time requirements of real time applications, the eligible vulnerability assessment methods have to consider the improvement of calculation time. Although there are several methods capable of performing quick assessment, these techniques are not fast enough to analyze real large power systems in real time. Based on the fact that vulnerability begins to develop in specific regions of the system exhibiting coherent dynamics, large interconnected power systems can be reduced through dynamic equivalence in order to reduce the calculation time. A dynamic equivalent should provide simplicity and accuracy sufficient for system dynamic simulation studies. Since the parameters of the dynamic equivalent cannot be easily derived from the mathematical models of generators and their control systems, numerical identification methods are needed. Such an identification task can be tackled as an optimization problem. This paper introduces a novel heuristic optimization algorithm, namely, the Mean-Variance Mapping Optimization (MVMO), which provides excellent performance in terms of convergence behavior and accuracy of the identified parameters. The identification procedure and the level of accuracy that can be reached are demonstrated using the Ecuadorian-Colombian interconnected system in order to obtain a dynamic equivalent representing the Colombian grid.

A strategy to simultaneously tune power system stabilizers

Abstract: This paper is aimed to tune multi-band power system stabilizers (MB-PSSs), which main purpose is the power oscillation damping enhancement. The proposition is formulated as the minimization of a quadratic criterion, which is solved by the differential evolution (DE) optimizer. Likewise, dynamic equivalents are employed in order to reduce the dimensionality and complexity of the problem as well as to facilitate the solution. Results on a portion of the high voltage Mexican power grid are presented, showing the proposal’s applicability.

Dynamic equivalence by an optimal strategy

Abstract: Due to the curse of dimensionality, dynamic equivalence remains a computational tool that helps to analyze large amount of power systems’ information. In this paper, a robust dynamic equivalence is proposed to reduce the computational burden and time consuming that the transient stability studies of large power systems represent. The technique is based on a multi-objective optimal formulation solved by a genetic algorithm. A simplification of the Mexican interconnected power system is tested. An index is used to assess the proximity between simulations carried out using the full and the reduced model. Likewise, it is assumed the use of information stemming from power measurements units (PMUs), which gives certainty to such information, and gives rise to better estimates.

Heuristic optimization based approach for identification of power system dynamic equivalents

Abstract: This paper introduces an approach for identification of dynamic equivalent parameters from measured operational dynamic responses associated to different disturbances. To tackle challenges related to optimization problem complexity (i.e., non-linearity of time-domain simulation based fitness calculation, discontinuity, non-convexity, and multimodality), the approach adopts a novel variant of the mean-variance mapping optimization algorithm to pursue efficient and fast search capability. This variant bases on swarm intelligence precepts and employs a multi-parent crossover criterion for offspring creation. Numerical tests performed on the Ecuadorian–Colombian interconnected system, including performance comparisons with other heuristic optimization tools, support the potential of the proposal to provide accurate estimates within a fast convergence rate.

Precise equivalent model of small hydro generator cluster and its parameter identification using improved Grey Wolf optimiser

Abstract: With the total installed capacity of small hydro generator cluster (SHGC) continues to grow rapidly, the effect of SHGC will have affected to the security and stability of the main network in China, especially to power oscillations of passageway of ultra-high-voltage AC and DC. Thus, a precise equivalent model of SHGC is proposed in this study. In the proposed model, the fifth-order model of generator is adopted as the equivalent generator model, the excitation system is simplified into proportional feedback control model and exponential load model is used as equivalent load model. In addition, Grey Wolf optimiser with chaotic local search is designed to identify the parameters of the equivalent model. Finally, the proposed equivalent technique is applied in one simulation experiment and one practical experiment. The experimental results demonstrate that the validity and accuracy of the proposed equivalent model and identification method in solving dynamic equivalent of SHGC in engineering practice.