Abstract

In power systems, although the inertia energy in power sources can partly cover power unbalances caused by load disturbance or renewable energy fluctuation, it is still hard to maintain the frequency deviation within acceptable ranges. However, with the vehicle-to-grid (V2G) technique, electric vehicles (EVs) can act as mobile energy storage units, which could be a solution for load frequency control (LFC) in an isolated grid. In this paper, a LFC model of an isolated micro-grid with EVs, distributed generations and their constraints is developed. In addition, a controller based on multivariable generalized predictive control (MGPC) theory is proposed for LFC in the isolated micro-grid, where EVs and diesel generator (DG) are coordinated to achieve a satisfied performance on load frequency. A benchmark isolated micro-grid with EVs, DG, and wind farm is modeled in the Matlab/Simulink environment to demonstrate the effectiveness of the proposed method. Simulation results demonstrate that with MGPC, the energy stored in EVs can be managed intelligently according to LFC requirement. This improves the system frequency stability with complex operation situations including the random renewable energy resource and the continuous load disturbances.

Highlights

  • Due to technological and regulatory innovations, the micro-grid has become an alternate choice to compete with traditional centralized electricity plants for its small-scale and on-site distributed energy providing capability

  • We focus on the design of a power system frequency oscillation damping controller using electric vehicles (EVs)

  • Load frequency stability is an important issue in micro-grid, especially for the power fluctuation caused by renewable energy sources

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Summary

Introduction

Due to technological and regulatory innovations, the micro-grid has become an alternate choice to compete with traditional centralized electricity plants for its small-scale and on-site distributed energy providing capability. The distributed generation has to cope with varying load and fluctuating renewable energy sources in the isolated mode, which requires proper control of micro-grid to ensure frequency and voltage stability in order to supply high-quality power to customers. With the control procedure of multi-step prediction, rolling optimization and feedback correction [17], MGPC can effectively solve multivariable optimal control problem with constraints even without an accurate system model, so that the rapid change of system operation status can be tracked quickly In this controller design, the LFC signal is dispatched to diesel generator (DG) and EVs according to the response speed and the controllable capacity; the wind turbine generator is modeled as a random fluctuating resource in this paper.

Model of the Benchmark Micro-Grid
Benchmark Micro-Grid with LFC Controller
Ht s f
The Electric Vehicle Model
Diesel Generator Model
Wind Turbine Model
CARIMA Model for Isolated Micro-Grid
State Monitoring and Output Prediction
Optimal Control
Simulation Studies
Case A
Case B
Case C
Findings
Conclusions
Full Text
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