IET Energy Systems Integration最新文献

This paper presents hybrid quasi-Z-source converters (qZSCs) designed for integrated energy system-based microgrid applications, capable of providing dual-DC and multi-AC outputs from a single DC input source. Microgrids rely on diverse renewable energy sources such as solar and effective power converters and are crucial for integrating these resources into the grid. The proposed converters incorporate series and parallel-configured integrated inverters, facilitating both boost and buck-boost operations simultaneously with an additional inductive branch to the standard quasi-Z-source network. The suggested system utilises a novel control approach to regulate multiple AC and DC output voltages efficiently. Key features include robust power control, single-stage energy conversion, built-in shoot-through protection and immunity to electromagnetic interference. The proposed series and parallel converter circuits offer versatile configurations for generating two DC and multiple AC outputs, enhancing flexibility in microgrid power distribution. A closed-loop control strategy is implemented for the series qZSC to validate its operational effectiveness. Detailed steady-state mathematical analyses for both qZSC configurations are supplemented by simulation results under varying load conditions, confirming their performance capabilities. Additionally, for further validation, Hardware-in-the-loop (HIL) results were obtained with a real-time emulator using Typhoon HIL to prove the effectiveness of the proposed system.

Insufficient dissolved oxygen in aquaculture systems poses a significant challenge to sustainable fish farming, while traditional aeration systems rely heavily on grid electricity, contributing to both operational costs and environmental impact. This study addresses these challenges by integrating a compressed air oxygenation system with floating solar photovoltaic (PV) power generation, supported by deep learning-based forecasting for optimal system control. Our key contributions include: (1) development of an integrated floating PV-powered compressed air oxygenation system for aquaculture, (2) implementation and comparative analysis of three deep learning models (RNN, GRU and LSTM) for forecasting both PV power generation and compressed air production and (3) validation through a real-world case study in Thailand's Pathum Thani Province. The LSTM model demonstrated superior performance, achieving the highest accuracy with RMSE of 172.59 kW and MAPE of 13.87% for PV power forecasting, and a MAPE of 21.72% for compressed air production forecasting. The implemented system successfully improved water quality in a 1200-cubic-metre freshwater fish pond, increasing dissolved oxygen levels from 1.7 to 6.47 mg/L over a 4-month period. These results demonstrate the feasibility and effectiveness of renewable energy integration in aquaculture water treatment, offering a sustainable solution for fish farming operations while reducing dependency on grid electricity.

Multiterminal high-voltage direct current (MTDC) systems are anticipated to enable the massive integration of renewable energies into modern grids. However, the protection of MTDC systems is a major challenge for their application in connection with offshore wind farms (OWF). This is due to the extremely high short circuit currents, present for very short timeframes, and characterised by the absence of zero-crossing currents. Additionally, economic and technological issues further challenge widespread implementation of MTDC systems. The main constraints of MTDC protection coordination systems are generally associated with fault detection, DC reactor (DCR), DC circuit breaker (DCCB) operation time, and converter blocking time. This paper presents strategies for achieving full-selectivity (F-S) and partial-selectivity (P-S) in the protection of voltage source converter (VSC)-MTDC systems. A case study is setup to design both the F-S and P-S protection schemes. Initially, suitable DCRs are calculated for the case study, followed by selecting DCCB operation times with offshore converter blocking for both cases. Finally, an inverse time-current curve is proposed for different scenarios, considering sensitivity to DCR ratings to enhance converter blocking performance. The case study is conducted in PSCAD/EMTDC software and the simulation results demonstrate the impact of the different scenarios on the MTDC systems.

This research investigates the intricate relationship between load variations, environmental conditions, and the resultant stray current generation within DC railway systems. A scaled-down single-viaduct model was employed to establish a controlled experimental environment for real-time monitoring of voltage differentials between the railway tracks and the grounding structure. This research developed a stray current monitoring system for a scaled-down single-viaduct model. The system comprises of a power supply, voltage and current measurement capabilities at the power supply, and two levels of stray current measurements at each point. Data such as ambient temperature and humidity, current and voltage at the power supply, and voltage differentials between the railway tracks and the grounding structure are recorded using an Arduino Mega2560 microcontroller. It is hypothesised that stray currents, quantified as voltage differentials between the tracks and the grounding structure, vary in response to changes in load and environmental conditions. Experiments were conducted under various scenarios: variable load, constant load with rain, and constant load across different seasons. The results indicated that with a variable load, the voltage between the tracks increased. During constant load with rain, the average voltage between the tracks rose due to decreased insulation between the tracks and the grounding structure. Lastly, under constant load across different seasons, the most significant voltage change was observed during the rainy season. The findings demonstrate a significant correlation between these variables, with a pronounced influence of environmental conditions, particularly precipitation, on voltage fluctuations. These results underscore the critical importance of effective stray current mitigation strategies for safeguarding the integrity of railway infrastructure and ensuring the safety of personnel. The study offers a valuable contribution to the understanding of stray current phenomena and provides essential insights for the development of advanced protection systems.

Coal mines consume electricity from grids while making use of various derived energy resources to generate heat and power. This allows coal mines to act as energy prosumers. This paper presents an integrated optimisation model of optimal operation and offers strategies for profit-seeking of a coal-mine energy prosumer in a liberalised market. The discussed problem is formulated as a tri-stage bi-level programming model. In the upper level, the coal mine-integrated energy system (CMIES) operator decides the retail contract management, equipment operation plan, and retail electricity price offered to end-users through three stages to maximise its expected profits at a predefined risk level. In the lower level, the end-users react to the price bids offered by the CMIES operator under study and other market retailers to minimise their costs for energy procurement. Unlike previous approaches, the endogenous uncertainties associated with market subjects' strategic behaviours are explicitly considered. To solve the proposed problem efficiently, the Karush–Kuhn–Tucker conditions and multicut benders decomposition method are employed. The simulation results show that the collaborative optimisation of the energy cycle and production scheduling can reduce daily operating costs by nearly $3576 and carbon emissions by 6.72 tons, which verifies the effectiveness of the proposed method.

In recent years, bifacial solar panels are accelerating to replace single-side PV devices in traditional PV power generation system due to their high utilisation rate and price advantages. This makes the stability and control strategy of grid-connected bifacial PV systems (GCBPVS) to be different from the traditional method after it is connected to the power systems. This paper fully considers each detailed module in GCBPVS using virtual synchronous generator (VSG) technology and derives the small-signal model of the fully grid-connected (GC) system using the linearisation method of each sub-module. Then, it analyses the small disturbance stability and oscillation mode characteristics of GCBPVS by combining the effects of partial system parameters change on eigenvalues. Especially for the key parameters that affect the control stability of the system, this paper proposes a novel global optimisation design method of key control parameters to reform the distribution of system eigenvalues and improve the stability of GCBPVS. Finally, case simulation and result analysis show that the accuracy of the above small-signal model is very high and the related stabilisation control method is very effective. In addition, hardware-in-the-loop (HIL) experiments demonstrate that the proposed control method has strong engineering practicability and is better suitable for application.

The inverter side of hybrid cascaded HVDC adopts the structure of Modular Multilevel Converter (MMC) in series with Line Commutated Converter (LCC). The complete system amalgamates the advantages of LCC with MMC, but it also makes the interaction process of multi-controller more complicated during the failure of the system. Therefore, through the analysis of the controller interaction process during the system fault, this paper proposes a multi-controller coordinated control strategy based on the inverter side of the hybrid cascaded HVDC system, which can suppress the subsequent commutation failure of the system and take into account the recovery characteristics of the system during the fault, which has certain practical application value. Initially, the operational properties of current error control (CEC) and voltage-dependent current limit control (VDCOL) are examined, and a coordinated control technique for subsequent commutation failure suppression and rapid power recovery during fault is proposed. Secondly, aiming at the problem of power return between MMC after VDCOL regulation, the new VDCOL control curve is coordinated to improve the MMC control strategy to ensure stable recovery during system failure. Finally, the simulation model is built in PSCAD/EMTDC simulation environment. The simulation results indicate that the proposed control technique can successfully achieve the synchronisation of commutation failure suppression and rapid, stable power restoration, thereby enhancing the operational performance of hybrid cascaded HVDC.

The inherent randomness and intermittent nature of wind speed fluctuations pose significant challenges in accurately predicting future wind speeds. To address this complexity, a wind speed prediction model based on a multiscale temporal-preserving embedding broad learning system (MTPE-BLS) is proposed. MTPE-BLS used the localised behaviour of wind speed data, which is simpler to model and analyse than global patterns. Firstly, frequency clustering-based variational mode decomposition (FC-VMD) is proposed to deal with the non-stationary wind speed data into multiple intrinsic mode functions (IMFs). Then, temporal-preserving embedding (TPE) is proposed to extract the underlying temporal manifold structure from the decomposed IMFs. Finally, the extracted features are mapped into the broad learning system (BLS) to establish an accurate prediction model. Experimental results on two real-world wind speed datasets demonstrate the best performance of the proposed MTPE-BLS model compared to that of others. Compared to the original BLS, the MTPE-BLS achieves significant improvements, reducing the root mean square error (RMSE) and mean absolute error (MAE) by an average of 48.57% and 47.72%, respectively.

Enhancing the stability of the Virtual Synchronous Generator (VSG) under transient conditions has become a new challenge for VSG operation. This paper presents the design of a Virtual Power System Stabiliser (VPSS) with virtual inertia calculations for the stability enhancement of the VSG system under transient conditions. The virtual inertia is calculated by considering the transient conditions resulting from a three-phase ground fault and the allowable phase margin in the VSG. This aims to prevent the coupling effect, which can cause the active power loop control and reactive power loop control to operate non-independently. Subsequently, the VPSS is specifically designed based on the determined virtual inertia characteristics. The VPSS design is developed by taking into account the phase angle shift of the VSG. The proposed combination of virtual inertia and VPSS is capable of providing accurate compensation for phase angle changes under transient conditions. To evaluate the performance of the proposed virtual inertia and VPSS, a system-level VSG model is used to thoroughly analyse the system's performance. Based on the results and analysis, it is shown that the control strategy utilising the combination of virtual inertia and the proposed VPSS design can improve VSG stability under transient conditions.