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This paper presents various control strategies to improve operations in two interconnected areas connected by a VSC‐HVDC transmission line. The main focus is on designing a central control system (CCS) that coordinates control units in both areas. In area 1, an AC voltage control unit is connected to the CCS. In area 2, three control units including a load power control unit, a fault detection unit, and an AC voltage control unit are also connected to the CCS. The CCS receives inputs from these units and generates commands for the DC voltage and active/reactive power control units on both sides of the DC line. The first proposed strategy addresses permanent voltage drops caused by load fluctuations in area 2. It adjusts the transmitted power from area 1 based on voltage variations in area 2. The second strategy focuses on mitigating faults in area 2 by injecting active and reactive power from area 1 during such events. The third strategy resolves transient voltage oscillations in both areas by controlling the reactive power of stations on either side of the DC line. Simulations using MATLAB‐SIMULINK demonstrate that these mechanisms successfully achieve their objectives. [ABSTRACT FROM AUTHOR]

Summary: This paper presents a new concept for district energy (DE) systems using central battery storage and decentralized hybrid renewable systems. The proposed DE consists of five buildings integrated with centralized 300 (V), 6.5 (A.h) batteries, locally distributed generations such as 8.5 (kW) wind turbines and 10 (kW) solar cells rated at 110 (V) and three‐phase loads. The central battery can be connected to each home for exchanging power. To increase the resilience, the proposed control system connects home 1 to the external 380 (V) and 50 (Hz) network when the battery is operating above the limited power (ie, 50 [kW] for this case study). The connection to the external grid is done by assessing and confirming a set of necessary conditions. The proposed integrated control system for DE is designed to achieve the following objectives: maximum power extraction from local wind/solar units by maximum power point tracking, optimal charge‐discharge process for central battery, connecting DE to the upstream network under outages and supplying the loads under all operating conditions. These goals are investigated by implementing six different scenarios of performance. In scenario 1, wind and solar units produce 6.6 (kW) and 24 (kW), respectively. Therefore, to feed the total load of 42.5 (kW), the central battery produces 15 (kW). In scenario 2, the total load in the first step is 35 (kW) and it is 95 (kW) in the second step. The power of solar and wind units in both loading steps is constant. The battery power increases from 6.5 (kW) absorption in the first step to 22 (kW) injections in the second step. In scenario 3, the solar units are switched off and in scenario 4, both solar and wind units are switched off. In such conditions, the battery responds to supply loads of homes. Increasing the energy resilience of DE during grid outages is modeled in scenario 5; where the battery power increases from 21 to 51.7 (kW) to deal with such outages. The nonlinear simulations in MATLAB/SIMULINK software show that the developed control strategy is able to control local renewable energies as well as the central battery while increasing the resilience and harvesting maximum power from decentralized wind/solar units. [ABSTRACT FROM AUTHOR]

Summary: This paper presents a novel control scheme on AC/DC ring bus islanded microgrid under unbalanced and non‐linear loads. The DC bus is integrated with the fuel cell, one wind turbine, and two batteries. The DC bus can be divided into two sub‐sections, where the first zone is supported by the fuel cell and battery 1, and the second zone is installed with the wind turbine and battery 2. The AC bus is also able to be sectionalized into two sub‐sections where the diesel generator and the unbalanced load are located on the first section and the non‐linear load with one wind turbine are placed on the other section. The DC bus is connected to the AC bus through two parallel three‐phase lines each one configured by three single‐phase inverters. The proposed control scheme in the ringed and separated modes presents several contributions including balancing the unbalanced loads, compensating the harmonics of non‐linear loads, improving the voltage stability and sag/swells, enabling partial operation under outages, and enhancing resilience. In the ring mode, wind turbine 1 and diesel generator inject balanced and linear P‐Q powers to the system as 39 kW/6 kVAr and 7 kW/9 kVAr, respectively. In the separated mode, the P‐Q powers of wind turbine 1 are 36 kW/9 kVAr and they are 15 kW/9 kVAr for diesel generators. In both modes, the unbalanced and non‐linear powers are supplied by the DC bus. The results verify that the developed control strategy efficiently deals with harmonic components, unbalanced currents and voltage issues. [ABSTRACT FROM AUTHOR]

This paper presents a control mechanism on high voltage direct current (HVDC) transmission line for frequency/voltage regulation, fault ride through (FRT) capability, and cyber‐attack/fault detection. The network under study consists of two areas with different frequencies that are connected through one 300 km HVDC line. The proposed control system regulates the frequency in both areas by managing power through HVDC line. The converters on both sides of HVDC line are controlled to handle faults on the DC and AC sections as well as improving fault ride through capability. The control strategies are implemented and operated depending on fault/cyber‐attack type and behaviour. In this respect, the control mechanism may change the firing angle of converters, switch their operating mode from rectifier to converter and vice‐versa or even block the converters. The proposed paradigm successfully distinguishes between the cyber‐attacks and faults. The simulations in MATLAB software validate that the proposed mechanism realizes all the objectives and the cyber‐attacks are completely identified and separated from the faults. [ABSTRACT FROM AUTHOR]

A resilient control system in the island microgrid including AC and DC buses is designed here. The DC bus is supported by fuel cell, solar cell and battery and the AC bus is equipped with diesel generator and wind turbine. The AC bus is sectionalized into three sub‐buses that enables to continue operation when one section is not functioning. The connection between DC and AC buses is made by two parallel three‐phase lines each line made by three single‐phase inverters. The objectives are to eliminate the harmonics, the unbalanced load management, dealing with outage of resources and short circuits, providing backup strategies and supplying critical loads under all events. The simulations are performed by MATLAB/Simulink. It is demonstrated that the resilient control technique can achieve all the defined purposes at the same time. The harmonics are eliminated, the unbalanced load issues are dealt with and the microgrid has sufficient resilience against outages and faults. [ABSTRACT FROM AUTHOR]