Abstract

The purpose of this study is to improve the P-I controllers of the voltage-source converters (VSC)-based multiterminal high voltage direct-current (MT-HVDC) networks. Since the VSCs are the non-linear elements of the MT-HVDC stations, the classical optimization methods, which approximately implement the linear model to optimize the P-I controllers of the VSCs, do not generate optimal results. Therefore, this paper presents a novel technique to optimize the VSC-based MT-HVDC grids’ P-I controllers by embedding the artificial bee colony (ABC) algorithm. The voltage-droop control method is employed at on-shore grids to ensure the active and reactive power balance within MT-HVDC networks. During an evaluation, achieved via a detailed four-terminal MT-HVDC model designed in PSCAD/EMTDC, the improved results obtained under different dynamic situations such as unbalance wind power generation, change in load demand at the on-shore side grids, and eventual VSC disconnection, respectively.

Highlights

  • A recent study exhibits that a multiterminal high-voltage direct current (MT-HVDC)network is a realistic approach to fulfill future power system requirements

  • The mechanism consists of two control loops; one is an inner-current control loop (ICC-L), and the seconds one is an outer-current control loop (OCC-L) [8,9]

  • PSCAD/EMTDC is used to design the four-terminal voltage-source converters (VSC)-based MT-HVDC test model to conduct the dynamic simulation to evaluate the performance of the suggested optimization technique

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Summary

Introduction

A recent study exhibits that a multiterminal high-voltage direct current (MT-HVDC). network is a realistic approach to fulfill future power system requirements. PSCAD/EMTDC is used to design the four-terminal VSC-based MT-HVDC test model to conduct the dynamic simulation to evaluate the performance of the suggested optimization technique. VCC is applied for voltage regulation in the MT-HVDC grid’s controller mechanism [21,22] In this technique, the three-phase AC currents and voltages of the converter are converted into a dq reference frame (at PCC) using dq-axis transformation, synchronized to on-shore side grid AC voltages via phase-locked loop (PLL). The three-phase AC currents and voltages of the converter are converted into a dq reference frame (at PCC) using dq-axis transformation, synchronized to on-shore side grid AC voltages via phase-locked loop (PLL) This technique provides a simple and decoupled regulation of active-power and reactive-power, plus control of AC voltage and DC-voltage. The OCC-L produces the ICC-L’s referenced currents, which decides the referenced voltages for the VSC in the dq frame

Inner Current Control Loop
Voltage-Droop Control
Employee Bees
On-Looker Bees
Scout Bees
Execution of the Multiobjective Functions
Comparative Analysis of the Controller’s Efficiency
Tuning of ICC-L Based on the Classical Optimization Method
Multiobjective Optimization of ICC-L and OCC-L Based on ABC Algorithm
Unbalance Wind Power
Unbalanced Load Demand at AC Grids
Eventual VSC Disconnection
Conclusions
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