scholarly journals Development of a brushless HTS exciter for a 10 kW HTS synchronous generator

2021 ◽  
Author(s):  
Christopher Bumby ◽  
Rodney Badcock ◽  
HJ Sung ◽  
KM Kim ◽  
Zhenan Jiang ◽  
...  
Keyword(s):  
Thermal Load ◽  
Synchronous Generator ◽  
Internal Resistance ◽  
Voltage Source ◽  
Synchronous Generators ◽  
Thermal Bridge ◽  
Current Leads ◽  
Experimental Laboratory ◽  
Laboratory Device ◽  
Dc Current

HTS synchronous generators, in which the rotor coils are wound from high-Tc superconducting wire, are exciting attention due to their potential to deliver very high torque and power densities. However, injection of the large DC currents required by the HTS rotor coils presents a technical challenge. In this paper we discuss the development of a brushless HTS exciter which operates across the cryostat wall to inject a superconducting DC current into the rotor coil circuit. This approach fundamentally alters the thermal load upon the cryogenic system by removing the need for thermally inefficient normal-conducting current leads. We report results from an experimental laboratory device and show that it operates as a constant voltage source with an effective internal resistance. We then discuss the design of a prototype HTS-PM exciter based on our experimental device, and describe its integration with a demonstration HTS generator. This 200 RPM, 10 kW synchronous generator comprises eight double pancake HTS rotor coils which are operated at 30 K, and are energised to 1.5 T field through the injection of 85 A per pole. We show how this excitation can be achieved using an HTS-PM exciter consisting of 12 stator poles of 12 mm YBCO coated-conductor wire and an external permanent magnet rotor. We demonstrate that such an exciter can excite the rotor windings of this generator without forming a thermal-bridge across the cryostat wall. Finally, we provide estimates of the thermal load imposed by our prototype HTS-PM exciter on the rotor cryostat. We show that duty cycle operation of the device ensures that this heat load can be minimised, and that it is substantially lower than that of equivalently-rated conventional current leads.

scholarly journals Development of a brushless HTS exciter for a 10 kW HTS synchronous generator

2021 ◽  
Author(s):  
Christopher Bumby ◽  
Rodney Badcock ◽  
HJ Sung ◽  
KM Kim ◽  
Zhenan Jiang ◽  
...  
Keyword(s):  
Thermal Load ◽  
Synchronous Generator ◽  
Internal Resistance ◽  
Voltage Source ◽  
Synchronous Generators ◽  
Thermal Bridge ◽  
Current Leads ◽  
Experimental Laboratory ◽  
Laboratory Device ◽  
Dc Current

HTS synchronous generators, in which the rotor coils are wound from high-Tc superconducting wire, are exciting attention due to their potential to deliver very high torque and power densities. However, injection of the large DC currents required by the HTS rotor coils presents a technical challenge. In this paper we discuss the development of a brushless HTS exciter which operates across the cryostat wall to inject a superconducting DC current into the rotor coil circuit. This approach fundamentally alters the thermal load upon the cryogenic system by removing the need for thermally inefficient normal-conducting current leads. We report results from an experimental laboratory device and show that it operates as a constant voltage source with an effective internal resistance. We then discuss the design of a prototype HTS-PM exciter based on our experimental device, and describe its integration with a demonstration HTS generator. This 200 RPM, 10 kW synchronous generator comprises eight double pancake HTS rotor coils which are operated at 30 K, and are energised to 1.5 T field through the injection of 85 A per pole. We show how this excitation can be achieved using an HTS-PM exciter consisting of 12 stator poles of 12 mm YBCO coated-conductor wire and an external permanent magnet rotor. We demonstrate that such an exciter can excite the rotor windings of this generator without forming a thermal-bridge across the cryostat wall. Finally, we provide estimates of the thermal load imposed by our prototype HTS-PM exciter on the rotor cryostat. We show that duty cycle operation of the device ensures that this heat load can be minimised, and that it is substantially lower than that of equivalently-rated conventional current leads.

scholarly journals A low-cost ac-dc rectifier for variable-speed wind energy conversion systems

2021 ◽  
Author(s):  
Zhenhan. Luo
Keyword(s):  
Control System ◽  
Low Cost ◽  
Synchronous Generator ◽  
Voltage Source ◽  
Current Loop ◽  
Variable Speed ◽  
Synchronous Generators ◽  
Wind Turbine System ◽  
Synchronous Reference Frame ◽  
Energy Conversion Systems

In this thesis, a novel AC-DC rectifier is adopted to convert the variable AC voltages from wind generator to a constant dc-link voltage. A DC-AC inverter is used to transfer the energy to fixed ac grid as well as maintain dc-link voltage constant. The rectifier is connected to the generator, which has two sets of three-phase windings. Electrical exited or permanent magnetic synchronous generators are suitable for this rectifier. The AC-DC rectifier features low cost, low power losses and simple control structure. The major content of this thesis consists of four parts. The first part investigates the operation of the AC-DC rectifier. The analysis illustrates the current paths in the rectifier and the remarkable voltage-boosting capability. A simulation model of the converter is built and verified. The second part models the synchronous generator with two sets of windings. The model is developed in the d-q synchronous reference frame. The simulation results from the model are verified by the experimental results.Then the third part is the design of the control system, which involves the generator, the AC-DC rectifier and constant dc-link voltage source. The control system composites of the inner current loop and the outer speed loop. The control system achieves the variable-speed operation of the generator and the regulation of the dc-link current. Finally, a prototype of wind turbine system is established in the lab to verify the analysis of rectifier, synchronous generator and control system design. The steady-state and transient responses of the wind system are compared. Simulation and experiment verify the analysis in this thesis.

scholarly journals Droop-free controls of inverter-based generator for use in systems that interconnected with synchronous generators

2021 ◽  
Vol 12 (2) ◽  
pp. 765
Author(s):  
Suchart Janjornmanit ◽  
Sakorn Panta ◽  
Wirat Nakkrongdee
Keyword(s):  
Synchronous Generator ◽  
Active Power ◽  
Control Technique ◽  
Voltage Source ◽  
Frequency Change ◽  
Droop Control ◽  
Synchronous Generators ◽  
Voltage Source Inverters ◽  
Autonomous Operation ◽  
The Stability

Because of its simplicity and autonomous operation, droop control technique is widely implemented for power generation control in microgrids. Despite its popularity, it has been reported that the technique has the stability problem. In this paper, the previous work of droop-free inverter-based generator designed for operating in a fix frequency islanded microgrid, is redesigned to have the ability to operate in both islanded and grid connected microgrid as well as to the main power grid where it interconnected with synchronous generators. The proposed voltage source inverters use phase locked loop(PLL) algorithm to synchronize the changing frequency due to the operation of the synchronous generator. Unlike the frequency droop control that the output frequency is varied as its active power changed, the proposed controls do not make an adjustment of the system frequency. This kind of operation reduces the chance of the system unstable due to severe frequency change and it also reduces the frequency deviation when it increases its active power output. Simulation and result of the meshed power network demonstrate the feasibility to implement the proposed controls in thereal system.

scholarly journals Adaptive Protection Coordination Method Design of Remote Microgrid for Three-Phase Short Circuit Fault

Energies ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 7754
Author(s):  
Wookyu Chae ◽  
Jung-Hun Lee ◽  
Woo-Hyun Kim ◽  
Sungwook Hwang ◽  
Jun-Oh Kim ◽  
...  
Keyword(s):  
Short Circuit ◽  
Renewable Energy Sources ◽  
Current Source ◽  
Synchronous Generator ◽  
Voltage Source ◽  
Small Island ◽  
Fault Current ◽  
Synchronous Generators ◽  
Adaptive Protection ◽  
Protection Method

Generally, the fault current supplied by inverter-based renewable energy sources (IBRES) and electrical storage systems (ESS) is about 1.2 to 2 times their rated current and much lower than synchronous generators because the former acts as a current source and the latter acts as a voltage source. A conventional power system in a small island is composed of only synchronous generators and protected from short circuit faults using an overcurrent relay (OCR). However, in the remote microgrid with IBRES, ESS, and synchronous generators, the fault current varies depending on the configuration of generation sources. Namely, the fixed OCR protection method cannot protect microgrids from short circuit faults. This paper proposes an adaptive protection method to protect the microgrid from faults by actively changing the OCR setting according to the state of the generator source combination. A microgrid with ESS and a synchronous generator is modeled and simulated through PSCAD/EMTDC software to validate the proposed adaptive protection method.

scholarly journals A low-cost ac-dc rectifier for variable-speed wind energy conversion systems

2021 ◽  
Author(s):  
Zhenhan. Luo
Keyword(s):  
Control System ◽  
Low Cost ◽  
Synchronous Generator ◽  
Voltage Source ◽  
Current Loop ◽  
Variable Speed ◽  
Synchronous Generators ◽  
Wind Turbine System ◽  
Synchronous Reference Frame ◽  
Energy Conversion Systems

In this thesis, a novel AC-DC rectifier is adopted to convert the variable AC voltages from wind generator to a constant dc-link voltage. A DC-AC inverter is used to transfer the energy to fixed ac grid as well as maintain dc-link voltage constant. The rectifier is connected to the generator, which has two sets of three-phase windings. Electrical exited or permanent magnetic synchronous generators are suitable for this rectifier. The AC-DC rectifier features low cost, low power losses and simple control structure. The major content of this thesis consists of four parts. The first part investigates the operation of the AC-DC rectifier. The analysis illustrates the current paths in the rectifier and the remarkable voltage-boosting capability. A simulation model of the converter is built and verified. The second part models the synchronous generator with two sets of windings. The model is developed in the d-q synchronous reference frame. The simulation results from the model are verified by the experimental results.Then the third part is the design of the control system, which involves the generator, the AC-DC rectifier and constant dc-link voltage source. The control system composites of the inner current loop and the outer speed loop. The control system achieves the variable-speed operation of the generator and the regulation of the dc-link current. Finally, a prototype of wind turbine system is established in the lab to verify the analysis of rectifier, synchronous generator and control system design. The steady-state and transient responses of the wind system are compared. Simulation and experiment verify the analysis in this thesis.

scholarly journals Dual Two-Level Voltage Source Inverter Virtual Inertia Emulation: A Comparative Study

Energies ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 1160
Author(s):  
Mohammad Ali Dashtaki ◽  
Hamed Nafisi ◽  
Amir Khorsandi ◽  
Mojgan Hojabri ◽  
Edris Pouresmaeil
Keyword(s):  
Harmonic Distortion ◽  
Synchronous Generator ◽  
Voltage Source ◽  
Small Signal ◽  
Voltage Source Inverter ◽  
Nonlinear Loads ◽  
Virtual Inertia ◽  
The Stability ◽  
Stability Enhancement ◽  
Oscillation Damping

In this paper, the virtual synchronous generator (VSG) concept is utilized in the controller of the grid-connected dual two-level voltage source inverter (DTL VSI). First, the topology of the VSG and the DTL VSI are presented. Then, the state-space equations of the DTL VSI and the grid-connected two-level voltage source inverter (TL VSI), regarding the presence of the phase-locked loop (PLL) and the VSG, are given. Next, the small-signal modeling of the DTL VSI and the TL VSI is realized. Eventually, the stability enhancement in the DTL VSI compared with the TL VSI is demonstrated. In the TL VSI, large values of virtual inertia could result in oscillations in the power system. However, the ability of the DTL VSI in damping oscillations is deduced. Furthermore, in the presence of nonlinear loads, the potentiality of the DTL VSI in reducing grid current Total Harmonic Distortion (THD) is evaluated. Finally, by using a proper reference current command signal, the abilities of the DTL VSI and the TL VSI in supplying nonlinear loads and providing virtual inertia are assessed simultaneously. The simulation results prove the advantages of the DTL VSI compared with the TL VSI in virtual inertia emulation and oscillation damping, which are realized by small-signal analysis.

Adaptive SRF-PLL Based Voltage and Frequency Control of Hybrid Standalone WECS with PMSG-BESS

2018 ◽  
Vol 19 (6) ◽  
Author(s):  
Anjana Jain ◽  
R. Saravanakumar ◽  
S. Shankar ◽  
V. Vanitha
Keyword(s):  
Reactive Power ◽  
Frequency Control ◽  
Storage System ◽  
Synchronous Generator ◽  
Energy Storage System ◽  
Voltage Regulation ◽  
Operating Conditions ◽  
Voltage Source ◽  
Voltage Source Converter ◽  
Control Scheme

Abstract The variable-speed Permanent Magnet Synchronous Generator (PMSG) based Wind Energy Conversion System (WECS) attracts the maximum power from wind, but voltage-regulation and frequency-control of the system in standalone operation is a challenging task A modern-control-based-tracking of power from wind for its best utilization is proposed in this paper for standalone PMSG based hybrid-WECS comprising Battery Energy Storage System (BESS). An Adaptive Synchronous Reference Frame Phase-Locked-Loop (SRF-PLL) based control scheme for load side bi-directional voltage source converter (VSC) is presented for the system. MATLAB/Simulink model is developed for simulation study for the proposed system and the effectiveness of the controller for bi-directional-converter is discussed under different operating conditions: like variable wind-velocity, sudden load variation, and load unbalancing. Converter control scheme enhances the power smoothening, supply-load power-matching. Also it is able to regulate the active & reactive power from PMSG-BESS hybrid system with control of fluctuations in voltage & frequency with respect to varying operating conditions. Proposed controller successfully offers reactive-power-compensation, harmonics-reduction, and power-balancing. The proposed scheme is based on proportional & integral (PI) controller. Also system is experimentally validated in the laboratory-environment and results are presented here.

scholarly journals A Grid-Supporting Photovoltaic System Implemented by a VSG with Energy Storage

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 3152 ◽  
Author(s):  
Huadian Xu ◽  
Jianhui Su ◽  
Ning Liu ◽  
Yong Shi
Keyword(s):  
Energy Storage ◽  
Synchronous Generator ◽  
Photovoltaic System ◽  
Voltage Source ◽  
Frequency Regulation ◽  
Pv System ◽  
Storage Unit ◽  
Support Functions ◽  
Energy Storage Unit ◽  
Pv Systems

Conventional photovoltaic (PV) systems interfaced by grid-connected inverters fail to support the grid and participate in frequency regulation. Furthermore, reduced system inertia as a result of the integration of conventional PV systems may lead to an increased frequency deviation of the grid for contingencies. In this paper, a grid-supporting PV system, which can provide inertia and participate in frequency regulation through virtual synchronous generator (VSG) technology and an energy storage unit, is proposed. The function of supporting the grid is implemented in a practical PV system through using the presented control scheme and topology. Compared with the conventional PV system, the grid-supporting PV system, behaving as an inertial voltage source like synchronous generators, has the capability of participating in frequency regulation and providing inertia. Moreover, the proposed PV system can mitigate autonomously the power imbalance between generation and consumption, filter the PV power, and operate without the phase-locked loop after initial synchronization. Performance analysis is conducted and the stability constraint is theoretically formulated. The novel PV system is validated on a modified CIGRE benchmark under different cases, being compared with the conventional PV system. The verifications demonstrate the grid support functions of the proposed PV system.

scholarly journals Overview of Methods for Determining Parameters of Synchronous Generators

2020 ◽  
Vol 20 (4) ◽  
pp. 103-113
Keyword(s):  
Power Systems ◽  
Computational Models ◽  
Meta Analysis ◽  
Measurement Data ◽  
Synchronous Generator ◽  
Adaptive Model ◽  
Operational Control ◽  
Synchronous Generators ◽  
Computing Power ◽  
The Stability

A synchronous generator is one of the key elements of any power system, having a significant impact on the stability and reliability of consumers’ power supply. Nowadays, the power systems emergency and operational control issues are being solved using computational models, the parameters whereof are determined using the reference data, or the data obtained during testing. High dependence of the models’ parameters on various external factors leads to a significant decrease in the accuracy of solving the issues of emergency and operational control. Identification based on the traditional telemetry systems or synchrophasor measurements is used to improve the accuracy of parameters of the power systems’ computational models. The purpose of this research lies in a meta-analysis of the available studies aimed at developing a methodology for determining parameters of a synchronous generator on the basis of measurement data. Russian and foreign studies were analyzed and grouped to achieve this goal. After that, for each group, advantages, disadvantages, and the area of application were identified. As a result, it is shown that the existing methods for determining parameters of synchronous generators based on measurement data cannot adapt to the source dataset and also require significant computing power. As a way to overcome these shortcomings, an adaptive model of a synchronous machine is proposed.

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