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1. Cyber Physical Implementation of Improved Distributed Secondary Control of DC Microgrid

   https://doi.org/10.1109/icpee50452.2021.9358705  

   Pragallapati, Nataraj; Ranade, Satish J; Lavrova, Olga (January 2021, 2021 1st International Conference on Power Electronics and Energy (ICPEE))

   null (Ed.)

   This paper presents a cyber physical system implementation of an improved distributed secondary control (IDSC) scheme of islanded dc microgrid (DCMG). The IDSC scheme mitigates the hidden issues of primary control with included droop technique for the distributed generation unit (DGU) in a DCMG by providing the adjustable voltage compensation, improves voltage regulation and enhances the current sharing of all DGUs. The voltage compensation of IDSC is the resultant of two voltage components, i.e., average distributed integral voltage controller and average current controller. The dynamic consensus algorithm is used to obtain the global average values in the for distributed secondary controlusing relatively low bandwidth communication. The impact of communication time delay on the stability in IDSC based DCMG with two DGUs is presented. The performance of IDSC scheme is validated on a microgrid scenario, which includes parallel connection of four DGUs and common load. The real-time cyber physical system of DCMG is implemented on OP AL-RT test platform that combines the device layer on FPGA, control and cyber layers on CPU of OP5700 by using eFPGASim and RT-LAB. 

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2. Self-Powered Motion Tracking Sensor Integrated with Low-Power CMOS Circuitry

   https://doi.org/10.1109/ISCAS51556.2021.9401440  

   Tasneem, Nishat T.; Biswas, Dipon K.; Mahbub, Ifana; Adhikari, Pashupati R.; Reid, Russell (May 2021, 2021 IEEE International Symposium on Circuits and Systems (ISCAS))

   null (Ed.)

   This paper presents a motion-sensing device with the capability of harvesting energy from low-frequency motion activities that can be utilized for long-term human health monitoring. The energy harvester used in the proposed motion sensor is based on the mechanical modulation of liquid on an insulated electrode, which utilizes a technique referred to as reverse electrowetting-on-dielectric (REWOD). The generated AC signal from the REWOD is rectified to a DC voltage using a Schottky diode-based rectifier and boosted subsequently with the help of a linear charge-pump circuit and a low-dropout regulator (LDO). The constant DC voltage from the LDO (1.8 V) powers the motion-sensing read-out circuitry, which converts the generated charge into a proportional output voltage using a charge amplifier. After amplification of the motion data, a 5-bit SAR-ADC (successive-approximation register ADC) digitizes the signal to be transmitted to a remote receiver. Both the CMOS energy harvester circuit including the rectifier, the charge-pump circuit, the LDO, and the read-out circuit including the charge amplifier, and the ADC is designed in the standard 180 nm CMOS technology. The amplified amplitude goes up to 1.76 V at 10 Hz motion frequency, following linearity with respect to the frequency. The generated DC voltage from the REWOD after the rectifier and the charge-pump is found to be 2.4 V, having the voltage conversion ratio (VCR) as 32.65% at 10 Hz of motion frequency. The power conversion efficiency (PCE) of the rectifier is simulated as high as 68.57% at 10 Hz. The LDO provides the power supply voltage of 1.8 V to the read-out circuit. The energy harvester demonstrates a linear relationship between the frequency of motion and the generated output power, making it suitable as a self-powered wearable motion sensor. 

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3. The Duality Droop Control for Grid-Tied Cascaded Microinverter

   https://doi.org/10.1109/APEC43580.2023.10131670  

   Qiu, Maohang; Wei, Mengxuan; Liu, Xiaoyan; Cao, Dong (March 2023, IEEE)

   Cascaded Connected Microinverter (CCM) system takes the advantage of adapting low voltage stress submodules to build the high voltage output, which makes it easier and safer to achieve for many applications. The distribution of active and reactive power in the CCM system has always been interdependent, resulting in additional communication components in different submodules. Such communication components within different submodules can be avoided by droop control. Droop control is widely adopted in parallel inverter system, and it originates from the synchronous generator that active power is controlled by adjusting synchronous generator's frequency and reactive power is controlled by adjusting its output voltage. However, the traditional droop control is not suitable for the cascaded microinverter inverter system. Therefore, it's necessary to modify the droop control to make it suitable for Cascaded Microinverter system, and therefore a control method called inverse droop control is adopted for cascaded inverter system under island mode. However, it requires a large feeder inductor when it's grid connected since every submodule works as voltage source inverter. In this paper, a duality control method that feedbacks each submodule's active power and reactive power to adjust its inductor current amplitude and frequency respectively is proposed. Compared with traditional cascaded inverter system that's controlled by inverse droop control method, the big line frequency feeder inductor is saved. 

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4. Droop-Free Distributed Control of DC Microgrids with Voltage Profile Guarantees and Relaxed Current Sharing

   https://doi.org/10.1109/ISGTEurope52324.2021.9640069  

   Mohiuddin, Sheik M.; Qi, Junjian (October 2021, 2021 IEEE PES Innovative Smart Grid Technologies Europe (ISGT Europe))

   This paper presents a droop-free distributed secondary control for DC microgrids with admissible voltage profile guarantees. The control objectives are achieved through an average voltage regulator, voltage variance regulator, and a relaxed current sharing regulator. Regulations of the global average voltage to the microgrid rated voltage is ensured by the average voltage regulator and regulations of the global voltage variance to a predetermined reference is enabled by the voltage variance regulator. In order to achieve the objectives of voltage regulation, the current sharing from one of the DGs which may be owned by the microgrid community is relaxed. The global dynamic model of the DC microgrid with the proposed control is derived. Besides, steady-state analysis is performed to show that all objectives can be achieved. Finally, simulations on a 4-DG DC microgrid test system are performed to validate the efficacy of the proposed control. 

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5. Fast and Secure Operation of Voltage Source Inverter based DERs using Model Predictive Droop Control

   https://doi.org/10.1109/ECCE.2018.8558323  

   Alhosaini, Waleed; Mahmud, Mohammad Hazzaz; Zhao, Yue (September 2018, Fast and Secure Operation of VSI based DERs using Model Predictive Droop Control)

   Reliability of the power grid can be improved by the use of microgrids (MGs) concept, which regulates the voltage and frequency at the point of common coupling (PCC) during normal and/or faulty conditions. Droop characteristics based hierarchical control strategies are commonly used in MGs, where power converters can operate in parallel. However, the need of multiple control loops not only adds complexity to the controller design, but also reduces the dynamic response of the system. In the future power system, grid-tied converters with fast dynamic response are desired to handle the uncertainties induced by high penetration of distributed energy resources. Therefore, this paper presents a novel model predictive control to ensure fast dynamic response of high power three-level converters in stand-alone operating mode as well as grid-tied operating mode. The proposed controller is applied to a MG which consists of a solar inverter connected in parallel with an energy storage system to the PCC, where a local load is tied. Both simulation and experimental results are presented to demonstrate robustness and the high dynamic performance of the proposed controller under rapidly changing atmospheric conditions and different grid operating modes. 

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