Microturbine Generation Research Articles

Voltage and frequency control of microgrid in presence of micro-turbine interfaced to matrix converter

The active and reactive load changes have a significant impact on voltage and frequency. In this paper, in order to stabilize the microgrid (MG) against load variations in islanding mode, the active and reactive power of all distributed generators (DGs), including energy storage (battery), diesel generator, and micro-turbine, are controlled. The micro-turbine generator is connected to MG through a three-phase to three-phase matrix converter, and the droop control method is applied for controlling the voltage and frequency of MG. In addition, a method is introduced for voltage and frequency control of micro-turbines in the transition state from grid-connected mode to islanding mode. A novel switching strategy of the matrix converter is used for converting the high-frequency output voltage of the micro-turbine to the grid-side frequency of the utility system. Moreover, using the switching strategy, the low-order harmonics in the output current and voltage are not produced, and consequently, the size of the output filter would be reduced. In fact, the suggested control strategy is load-independent and has no frequency conversion restrictions. The proposed approach for voltage and frequency regulation demonstrates exceptional performance and favorable response across various load alteration scenarios. The suggested strategy is examined in several scenarios in the MG test systems, and the simulation results are addressed.

Optimising microgrid energy management: Leveraging flexible storage systems and full integration of renewable energy sources

The significance of microgrid systems has grown considerably. This research proposes an innovative approach to manage uncertainty in microgrids by employing energy storage systems as the exclusive flexible resource. To address this challenge, a mathematical problem is formulated as a two-stage stochastic programming model, considering two uncertainties in the microgrid: wind and photovoltaic production. The microgrid system encompasses multiple components, including a diesel generator, a microturbine, wind and photovoltaic power generation, an energy storage system, and the microgrid’s demand. Notably, the microgrid exhibits two distinctive features: (i) the complete integration of wind and photovoltaic production, and (ii) the utilisation of an energy storage system as the sole flexible resource. The objective is to minimise the expected cost of the microgrid system while determining the optimal capacity of the energy storage system to meet the energy balance constraint. This constraint takes into account the varying scenarios of wind and photovoltaic production. The decisions are taking for a duration of 8760 h, a long-term evaluation. A case study is presented for actual data from Greece and the results show high volatility of the renewable energy sources implies higher energy storage system capacity as a sole flexible source for avoiding renewable curtailment.

Robust optimization scheduling of microgrid considering carbon capture equipment

To cope with the carbon dioxide generated during the operation of the microgrid and consider the wind power fluctuations, a robust optimization scheduling model for the microgrid is proposed, considering carbon capture equipment. Considering the large amount of carbon emissions caused by micro-turbine power generation and electricity purchase during the operation of microgrid, two operating modes of carbon capture equipment are considered, the carbon trading costs are considered in the objective function, and the output of all wind power is included through a box uncertain set. The C&CG algorithm was used to solve the constructed model and obtain the corresponding scheduling plan. Finally, the effectiveness of the model was verified through numerical examples. The results indicate that the total operating cost of microgrids can be further reduced by setting up carbon capture equipment to operate in flexible mode.

Analysis of Transmission System Stability with Distribution Generation Supplying Induction Motor Loads

A distributed-power-generating source (DPGS) is intended to locally supply the increased power demand at a load bus. When applied in small amounts, a DPGS offers many technical and economic benefits. However, with large DPGS penetrations, the stability of the transmission system becomes a significant issue. This paper investigates the stability of a transmission system equipped with a DPGS at load centres supplying power to both a constant power (CP) and induction motor (IM) load. The DPGSs considered in the present study are microturbine and diesel turbine power generators (MTGS and DTGS), both interfaced with synchronous generators. The influence of an IM load supplied by the DPGS on small-signal stability is studied by a critical damping ratio analysis. On the other hand, time-domain indicators of the transient response following a short circuit are employed in the analysis. Further, a variance analysis test (VAT) is performed to determine the contribution of IM and CP loads on the system stability. The study revealed that large penetration levels of IM loads significantly affect the stability and depend on the kind of DPGS technology used.

Using Multiple Stator Windings and Multi-Level Converters for Frequency Matching in Microturbine Generators

Using Multiple Stator Windings and Multi-Level Converters for Frequency Matching in Microturbine Generators

An integrated approach for cost-and emission optimal planning of coastal microgrid with demand-side management

In the realm of sustainable power systems, the pivotal role of demand-side management (DSM) in Microgrids (MGs) design and planning is increasingly recognized. This study accentuates the significance of DSM in improving operational efficiency, economic viability, and environmental sustainability of MGs, focusing on a remote community in the Gulf Al-Aqaba, Sinai Peninsula, Egypt. An innovative four-level approach is proposed for the techno-enviro-economic modelling, simulation, and optimization-based DSM of MGs, addressing the challenges posed by renewable energy integration and fluctuating electricity demands. The research explores three demand scenarios: a base load without DSM (SC-1), load shifting-based DSM (SC-2), and a combined load shifting/peak shaving DSM (SC-3), to demonstrate the adaptability and robustness of MGs under different conditions. The findings reveal significant improvements in MG performance, with peak load reduction from 73.66 kW in SC-1 to 50.82 kW in SC-2 and 44.82 kW in SC-3, highlighting the effectiveness of the applied DSM strategies. These strategies also yield economic benefits, evident in an 8% and 23% decrease in the total life cycle cost for hybrid and 100% renewable MG configurations under SC-2 and SC-3, respectively, compared to SC-1. Particularly noteworthy is the reduction in required capacities of key MG components in the hybrid MG scenario under SC-3, with reductions of 10% for solar photovoltaic, 33% for microturbine generator, and 40% for battery energy storage, implying cost savings and a more efficient MG setup. Additionally, the environmental impact is profound, with an 80.3% decrease in emissions for the hybrid MG setup under SC-3 compared to a standalone 50 kW MTG system under SC-1. This outcome highlights the potential of DSM in contributing to environmental sustainability, particularly in MG configurations involving renewable energy sources. In conclusion, the study provides comprehensive insights into the synergy between DSM and MG optimization, underscoring its essential role in addressing climate change and transitioning to sustainable energy systems.

Water Microturbines for Sustainable Applications: Optimization Analysis and Experimental Validation

The use of microturbines in irrigation applications represents a great opportunity for increasing sustainable energy generation. Irrigation systems have water flow that can be used to generate electricity based on microturbines that are acceptably configure such, that efficiency in crop irrigation is not affected. This research validates this use of microturbines through a system designed specifically for the characterization of microturbine generation technology. This system includes a closed water pumping circuit capable of working under, different water flow settings, as well as flow, pressure, and electricity generation sensors. For this system, the production range of the microturbines and the pressure loss associated with the various proposed configurations are characterized and specifically quantified for the best performance. After design and characterization of a scalable microturbine system, the feasibility and benefits of this application to supporting most relevant crops supplied by localized irrigation are analysed. The experiments demonstrate the greatest benefit with the implementation of 15 series microturbines each at 80 V, alongside non-Citrus fruit, where a favourable balance is achieved for the amortization period in vineyards and citrus fruit. The results validate a profitable and sustainable design for electricity generation, with return on investment rates of up to 53%. Therefore, this research offers real and extensive applications, while being scalable to rural, residential, urban and industrial settings.

Experimental study of the effect of load and rotational speed on the electrical power of a high-speed ORC microturbogenerator

The article presents the results of the study conducted on a microturbogenerator with a nominal power of 1 kWe. One of the primary objectives of the study was to determine the maximum power of the microturbogenerator for several preset and constant flow rates of the HFE-7100 working medium. During the tests, the variable parameters were the power of the heat source and the electrical load of the microturbine generator. Such a methodological approach made it possible to determine the experimental mechanical and electrical characteristics of the high-speed microturbogenerator, which are practically absent in the subject literature at present.The study shows that, at a preset working medium flow rate, there exists an optimum heat source power level at which the microturbogenerator's power output is maximum. It was determined that the maximum electrical power also depends on the load value of the microturbine generator. At the minimum tested working medium flow rate value of 30 g/s, a maximum power of approx. 210 We was obtained with a heat source power of 12 kWt and a resistive load of approx. 6.4 Ω. On the other hand, at the same flow rate value of the HFE-7100 and a heat source power of 14 kWt, the maximum electrical power of the microturbogenerator was approximately 205 W. On the other hand, for an HFE-7100 flow rate of 60 g/s, the maximum electrical power of approximately 625 W was achieved with a heat source power of 18 kWt. It was found that the load current of the generator had a major influence on the maximum electrical power of the microturbogenerator.

Organic Rankine cycle turbogenerator cooling – Optimization of the generator water jacket heat exchange surface

Discharge of excess heat from the micro-turbine electric generator is an important issue for the micro-turbine operation and should be considered during the design process. The manuscript is intended to present a new tool for rapid shape optimization of the heat exchanging surface of the ORC (Organic Rankine Cycle) micro-turbine electric generator. The optimization of the water jacket geometry of a 10 kWe ORC micro-turbine generator is performed by making use of a modified, with respect to the models presented in the literature, 0D heat transfer model of the finned heat exchange surface of the cooling water jacket, and a genetic algorithm. As a result of optimization, an apparent reduction in fin size and increased fin density at the finned wall surface is achieved, yielding a significant increase of the heat transfer coefficient and a temperature decrease of the electric generator stator. The temperature at the shell surface tangential to the electric generator stator was found to decrease by over 6°C. A considerable reduction of temperature gradients around the water jacket wall is also reported.The results of optimization from the 0D model are verified by numerical simulation using a full 3D CFD model of fluid flow and conjugate heat transfer (CHT) in Ansys CFX for the original and optimized geometries. The CFD CHT model was first validated using experiment-based correlations for heat transfer in liquid flow over a circular cylinder pipe for a wide range of Reynolds numbers.The obtained temperature decrease in the optimized ORC electric generator stator for the nominal operating point of the ORC generator is found similar for both 0D and 3D models. The temperatures calculated in the 0D model at the shell surface tangential to the electric generator stator deviate from respective CFD values by 0.5–1.5°C. Another operational case beyond the nominal operating point has been analysed making use of the 3D CFD method as well, showing that the optimized geometry is characterized by an improved heat exchange performance not only for the nominal operating point.

Coordinated Control of an Islanded Microintegrated Energy System with an Electrolyzer and Micro-Gas Turbine

Microintegrated energy systems (MIESs) can be disconnected from power distribution systems during power system faults. This paper develops a control scheme for an islanded MIES. The VSC inverter controls the AC bus voltage and frequency using a modified AC voltage regulator and a modified frequency regulator. The control structures of the power-to-gas and PMSG-based microturbine generator (MTG) systems are improved. Renewable generation always runs at the maximum power point. The surplus renewable energy in the MIES can be converted into natural gas using power-to-gas, and the MIES can make full use of renewable energy. The proposed coordinated control scheme of the electrolyzer and the supercapacitor can achieve a power balance of the islanded MIES and reduce the DC-link voltage fluctuation. A micro-gas turbine can provide electric energy to the load and enhance distribution system resilience. A coordinated control scheme of the MTG and the supercapacitor is developed to improve MIES operation. A feature of this paper is the research on fault ride-through of the islanded MIES. A fault ride-through strategy is proposed, where the AC voltage of the VSC inverter is reduced to limit the short-circuit current during AC system faults. Islanded MIES simulations are conducted in a MATLAB/Simulink environment to test the control scheme. The simulation results verify the effectiveness of the control scheme during normal operation and failure.

Thermal performance of a microchannel primary surface recuperator for portable microturbine generators: Design and experimental study

The recuperator with high compactness and power/weight ratio is a mandatory component of portable microturbine generators (PMTG) to achieve the required energy density and power density. In order to explore the application prospects of cross-wavy primary surface recuperators (CW-PSR), an annular microchannel CW-PSR with heat transfer matrix compactness up to 2428 m2/m3 was designed by an in-house one-dimensional steady-state heat transfer model and successfully manufactured. Furthermore, an experimental system consisting of gas and air flow paths was built to validate the developed model and investigate the thermal performance of the new CW-PSR. On this basis, heat transfer experiments were performed under steady-state by changing the mass flow rate and inlet temperature of the gas. The experimental results show a good agreement between modeled results and experimental data of the power/weight ratio and effectiveness within an error of ±2%. There exists a significant heat transfer non-uniformity in the radial direction of the CW-PSR, but it was found to have little impact on the design accuracy of overall thermal performance. Due to corrugated microchannels, the heat transfer performance of the developed CW-PSR has been enhanced by up to 113.3% compared with straight channels and the experimental power/weight ratio of the CW-PSR is in the range between 9.6 kW/kg and 16.1 kW/kg, which means the microchannel CW-PSR is a promising heat exchanger for the PMTG.

Heterodyne Controlled Matrix Converter as a Direct Frequency Reduction Method for Microturbine Generators (MTG)

In this paper a control method for a matrix converter (MC) based on the heterodyne concept from the communication field is presented. The method is used to convert the high frequency of a microturbine generator’s (MTG) output voltage to the utility grid’s frequency. In this control method a frequency modulation (FM) of the MC’s switching frequency is achieved using a DQ0 analysis of the converter’s filtered output voltage with the utility grid’s frequency as a reference. After filtration, the MC achieves a conversion to the reference frequency with a minimal total harmonic distortion (THD) of the output voltage while using a low switching frequency. In addition, the proposed method decouples the output frequency, phase angle and voltage amplitude, which allows them to be controlled separately. This significantly simplifies the required control, and enables a robust and low-cost design. The theoretical analysis, simulation and experimental results of the method are reported.

The admissible set of parameters guaranteeing small‐signal stability of a microgrid

Microgrids possess rotating generators and inverter-based renewable resources and have limited inertia. The stability of a microgrid is affected by the parameters of controller and system equipment. This paper analyzes the set of all admissible parameters that guarantee the small-signal stability of a multi-source microgrid, which is called the small-signal stability region (SSSR). First, the stability impact of parameters varying in a given hypercube is studied. A sufficient robust stability condition is proposed with a hypercube parameter set, giving rise to linear matrix inequalities. The maximal hypercube ensuring stability can be found via dichotomy. Then, the SSSR is constructed via the union of hypercubes centered at different points. A special partitioning-and-pruning algorithm is proposed to search the parameter space and reduce the number of hypercube regions. Case studies are conducted on a testing system with a micro-turbine generator and two inverter-based generators. The SSSR is visualized, illustrating the interaction among generators and the stability impact of loads. The proposed method provides a useful reference for system design and security assessment.

Performance of a capstone gas turbine based power plant working on high Butane LPG

This paper presents the operational performance results of a 30 kW microturbine generator (MTGs) fed with high butane content liquefied petroleum gas, while subjected to a test procedure involving steady and transient load conditions. To evaluate the performance, measurements of turbine and generator parameters were gathered from its original unit controller, as load changes were applied. For the stand-alone mode detailed graphs of the test results are presented, showing the transparency and robustness of the turbine-generator set to the used fuel, judging by the quality of the output electric parameters. The results from this performance testing provide good insight into the use of high-butane content liquefied petroleum gas as fuel for the tested microturbine. The continuous use of a fuel would need more tests to establish that the life of the critical components of the microturbine are not hampered from what they are on the baseline fuel.
 The course of selected performance parameters in the microturbine generator is described in this document. The analysis of test results of the microturbine under steady-state and transient operation have been made. Both in steady state and transient conditions, values of output power, speed fluctuation, emissions, noise levels, and exhaust gas temperatures remained under acceptable levels.

Analysis of power conversion technology options for a self-powered furnace

A self-powered furnace is defined as one that imports no electricity: a power cycle integrated into the furnace generates all the electrical power needed, and the heat rejected by the power cycle contributes to space heating. This paper presents criteria for selection of suitable power generation technology for such a furnace. A weighting system was presented to assign weight to each criterion based on its importance to the success of a self-powered furnace implementation. Power generation candidates were reviewed and scored based on the selection criteria. The top five candidates were analyzed to quantitatively compare the additional heat exchange requirements they impose on a baseline furnace. Air-cooled internal combustion engines and microturbine generators had negligible impact on the heat exchange requirement compared to a baseline furnace. Liquid-cooled internal combustion engines increased the heat exchange requirement by a factor of 1.5. Thermoelectric generators and thermophotovoltaic increased the heat exchange requirement by a factor of roughly 2.5. Organic Rankine cycle increased the heat exchange requirement by a factor of 5.

Feasibility analysis and optimization of an energy-water-heat nexus supplied by an autonomous hybrid renewable power generation system: An empirical study on airport facilities

This paper investigates the potential and feasibility of an integrating hybrid renewable power generation system with a large-scale reverse osmosis desalination plant to provide electricity, heat, and water for the New Capital International Airport, Egypt. The proposed energy system contains photovoltaic panels, wind turbine, combined heat-power microturbine generator, diesel generator, batteries, converter, thermal load controller, and a boiler. A comprehensive energy-economic-environmental optimization analysis was performed to optimize energy systems in which 16-feasible solutions were evaluated and compared. The results revealed that the optimal system has the least net present and energy costs by 1.54 M$ and 0.089 $/kWh, respectively, and needs only 1.12 years to recover the invested money. Moreover, the proposed system produces emissions of 59.5% less than the base-case. The optimal system has a negligible unmet load ratio since it has a negligible loss of power supply possibility of 0.0993%. The thermal load controller has a significant impact on reducing the net present cost, cost of energy, emissions, and needed batteries by 52%, 56.4%, 36.5%, and 90%, respectively compared to the base-case. The obtained results are expected to attract large investments in clean energy and water desalination because of the government's challenges in such fields.

Improving frequency regulation of wind‐integrated multi‐area systems using LFA‐fuzzy PID control

Due to the complexity and importance of the electricity grid stability, sophisticated control systems and computational approaches are essentially required to solve dynamical system frequency problems in multi-area systems. Participation of wind turbines in power system frequency control in the form of stepwise inertial control in the presence of a proposed adequately tuned fuzzy-PID load-frequency control is investigated in this paper. A two-area power system is studied in which it is linked through tie-line and equipped with fuzzy-PID control systems. To increase the energy transition and flexibility of the entire system against frequency events and parameters uncertainties, the fuzzy-PID controllers are first tuned using lightning flash algorithm (LFA). The tuned controllers are then used in each area to optimally counterbalance the frequency deviations and the tie-line power of the interconnected areas against varying load disturbances, wind power fluctuations, and to keep the renewable integrated system in a stable state. The sensitivity analysis is also conducted with a wide range of system parameter variations, uncertainties, and disturbances. Furthermore, the LFA-tuned fuzzy-PID load-frequency control is also tested in a two-area isolated microgrid, comprising wind turbine, PV panels, fuel cells, micro-turbine, and diesel engine generator. The results obtained using the proposed approach are compared with other state-of-the-arts algorithms and control systems in the literature. The compared results show the efficiency and robustness of the proposed optimization-based controller for better frequency control in multi-area power systems and isolated microgrids. The results also demonstrate that a finely tuned automatic generation controller gives a significant boost to grid frequency control when wind turbines participate in the inertial control, suggesting migration from conventional PID-based automatic generation control to more adaptive control approaches.

Characterisation of micro turbine generator as a range extender using an automotive drive cycle for series hybrid electric vehicle application

This study investigated a micro turbine generator (MTG) as a range extender for a series hybrid electric vehicle application for a range of constant and dynamic power demand strategies. The power demands were calculated through a mathematical model based on a specific vehicle platform using the New European Drive Cycle (NEDC). The power demands were then used to characterize the MTG in a controlled test environment. Each of the strategies produced interesting results in terms of fuel consumption, specific emissions, net efficiency, and power responses. The experimental results revealed the lowest specific emissions, and fuel consumption while the MTG operated at constant power demand. One of the dynamic power demand strategies also produced low fuel consumption, but with higher specific emissions. Although exhaust emissions in each strategy were well below the Euro 6c limits. These results indicate the potential of MTG as a range extender in a series hybrid vehicle. Even, the MTG can be operated dynamically with relatively low fuel consumption and very low specific emissions, compared to the traditional approach of a constant power demand.

Efficient Energy Delivery System of the CHP-PV Based Microgrids with the Economic Feasibility Study

AbstractA comprehensive theoretical investigation validated by the measurement is necessary to assess the impact of a microgrid on the electric distribution system. Some key parameters worth investigating are- enhancing economy, reliability, quality, and resiliency of a microgrid. Considering this necessity, a study of energy delivery system in a microgrid and its financial feasibility to integrate into the energy infrastructure has been presented in this paper. A campus microgrid with energy-efficient combined heat and power (CHP) natural gas-fired microturbine and photovoltaic generation has been used as a testbed to evaluate the efficiency of the power delivery. With distributed control and communication capability, this microgrid can be considered as a building block of smart grid that facilitates the inclusion of renewable and energy-efficient distributed generation. Simulation work has been performed to study the economic feasibility to integrate such microgrid into the energy grid. Several cases of remote microgrid operation have been studied to compare the best possible solution.

The development of a high efficiency microturbine generator for a vehicle

Currently, microturbines are becoming increasingly common in power generation. There is a desire to use them as an energy source for the hybrid cars with the wheels driven by an electric motor. However, stationary microturbines are not well adapted for use on the automobiles. The main differences are frequent engine stops and lack of space for large heat exchangers. These differences lead to a decrease in the engine efficiency. The article discusses the technical solutions for the design of microturbines with high efficiency, small size of the heat exchanger and the bearings with reduced friction losses. The calculation studies have shown a possibility of achieving high efficiency for microturbines in a car. Currently, tests of real engine components to confirm the calculations have ended. Based on the test data, a microturbine is being designed. This microturbine will have been made by the end of this year.