Feng Zhou

To shorten the surface transmission chain of conventional beam pumping units while improving compatibility between direct-drive actuation and the existing walking-beam structure, this study proposes an arc permanent-magnet synchronous motor (arc-PMSM) arranged along the walking-beam trajectory. The rotary motor–belt–gearbox–crank/linkage drive chain is replaced while the walking beam, horsehead, polished rod, and principal lifting geometry are retained. A two-dimensional (2D) equivalent linear-motor model is used for electromagnetic design and sequential parametric screening, followed by a three-dimensional (3D) arc model for numerical cross-checking of the principal electromagnetic quantities. Performance is further evaluated over a representative motor-side speed range of 0.28–0.70 m/s, and two dynamic pumping scenarios are investigated using a sequential electromagnetic–kinematic framework. After screening, the average thrust increases from 58.76 to 59.72 kN, the thrust ripple decreases from 26.7% to 12.6%, and the maximum flux density decreases from 1.92884 to 1.71113 T. The approximately equivalent 3D model gives an average thrust of 60.78 kN and a thrust ripple of 14.9%, with only a 1.77% difference in average thrust relative to the 2D design. Across 0.28–0.70 m/s, the calculated average thrust remains within 56.31–60.07 kN, total electromagnetic loss is 2.01–2.55 kW, and motor efficiency is 88.7%–94.4%; the rated power factor given in the 3D design data is 0.97. Under a scheme-level comparison reflecting the characteristic low average motor load factor of conventional beam-pumping operation, the conventional drive-chain efficiency is 44.16% and the arc-PMSM direct-drive efficiency is 87%, corresponding to a 42.84-percentage-point difference. The two dynamic scenarios yield average motor efficiencies of 71.33% and 82.18%, with the target-trajectory case showing better coordinated input/output power variation during low-load and acceleration/deceleration intervals. The results support the high-efficiency potential of trajectory-matched arc-PMSM direct drive while retaining the principal lifting structure and removing intermediate surface mechanical transmission stages.

To address the challenges of achieving thermostatic control and mitigating temperature non-uniformity in battery packs using conventional liquid cooling methods, this study proposes an optimized cooling strategy that combines PCMs with mini-channel structures. To investigate the influence of PCMs on enhancing heat dissipation performance, a three-dimensional transient temperature field analysis is conducted to compare the impact of different cooling media on lithium-ion battery temperatures under identical cooling structures. The results indicate that when a phase change medium is utilized as the coolant, the peak temperature and overall temperature difference of the battery pack are fundamentally consistent with the cooling performance achieved by conventional liquid cooling. However, the global uniformity of the battery pack is significantly improved, accompanied by a substantial reduction in the required coolant flow rate. Two PCM-based optimization models are proposed: a dual-channel cold plate and a mini-channel cold plate, both evaluated at a 1C charging rate. Theoretical calculations and simulation analyses reveal that the dual-channel model reduces the peak temperature and overall temperature difference by 1.5 ℃ and 1.0 ℃, compared to a conventional liquid cooling system. In contrast, the mini-channel model achieves further improvement, lowering the peak temperature and temperature difference by 1.7 ℃ and 1.2 ℃. These findings demonstrate that an optimized heat dissipation architecture and medium can achieve robust thermostatic control and effectively enhance thermal uniformity. This work lays a theoretical foundation and provides technical references for designing thermal management systems in energy storage power stations, ensuring optimal operating temperatures and improved overall efficiency.

Traditional electromagnetic heaters close the magnetic circuit through a core and yoke, causing material redundancy and higher costs. This paper proposes a self-closed magnetic circuit that eliminates the core and yoke without increasing magnetic leakage or degrading performance. Based on a three-phase three-column transformer, a 10 kV/600 kW coreless, yoke-less, self-closed Dual-Pipe electromagnetic heater with a three-phase spatial structure was designed, achieving 98.05% heating efficiency. To reduce local leakage at the junctions between the inner pipe core and elbows, an inner-pipe self-closed magnetic circuit was introduced, increasing efficiency to 98.26% and reducing the primary-winding back-EMF waveform distortion rate from 1.813% to 0.813%.The effects of inner-pipe hollow radius, spacing between the three-phase closed pipelines, and secondary-winding outer-pipe wall thickness were systematically investigated. Increasing the hollow radius stabilized heating power but increased back-EMF distortion. Increasing pipeline spacing also increased distortion and reduced magnetic flux density, while a more uniform magnetic-field distribution occurred only at a specific spacing. Increasing outer-pipe wall thickness decreased the maximum magnetic flux density in the inner pipe.After structural optimization, a three-phase planar self-closed electromagnetic heater was designed with 98.02% efficiency, confirming that the three-phase spatial structure achieves higher efficiency. The proposed concept reduces magnetic leakage and core-material use. Powered directly by a power-frequency source, it avoids high-frequency power electronic devices, improves reliability, and is suitable for medium- and small-scale, low-cost industrial and residential electromagnetic heating systems.

Traditional electromagnetic heaters typically close the magnetic circuit through the connection of a core and yoke, which can lead to issues such as material redundancy and increased costs. This paper proposes a design concept centered on a self-closed magnetic circuit, eliminating the core and yoke structure while ensuring no increase in magnetic leakage and maintaining optimal system performance. Based on the structure of a three-phase three-column transformer, a 10kV/600kW coreless and yoke-less self-closed magnetic circuit three-phase spatial structure Dual-Pipe electromagnetic heater was designed. The heating efficiency reached 98.05%, demonstrating the effectiveness of the proposed structure. To address the issue of partial magnetic leakage at the junction between the inner pipe core and elbows, an inner pipe self-closed magnetic circuit structure was introduced. As a result, the heating efficiency increased to 98.26%, and the waveform distortion rate of the primary winding back electromotive force was reduced from 1.813% to 0.813%. The influence of key structural parameters, including the inner pipe hollow radius, the spacing between the three-phase closed pipelines, and the outer pipe wall thickness of the secondary winding, on performance is systematically studied and analyzed to identify the corresponding influence patterns. It was observed that as the hollow radius of the inner pipe increased, the heating power of the electromagnetic heater tended to stabilize. However, the waveform distortion rate of the primary winding back electromotive force increased accordingly. As the spacing between the closed pipes increased, the waveform distortion rate of the primary back electromotive force also increased, and the magnetic flux density decreased. It was observed that only at a certain distance would the magnetic field distribution become more uniform. As the wall thickness of the outer pipe increased, the maximum magnetic flux density in the inner pipe showed a decreasing trend. Based on the above observations, further optimization of the structural parameters was performed. Finally, a three-phase planar structure self-closed electromagnetic heater was designed, achieving a heating efficiency of 98.02%. Clearly, the three-phase spatial structure is capable of achieving higher efficiency. The design concept proposed in this paper, which centers on a self-closed magnetic circuit, effectively reduces magnetic leakage and minimizes the use of core materials. Powered by a power frequency source, it eliminates the need for high-frequency power electronic devices, thereby ensuring system reliability. This design is particularly suitable for medium- and small-sized, low-cost industrial and residential electromagnetic heating systems.

To address the grid volatility issues caused by the integration of electric vehicles and distributed energy storage, a multi-timescale real-time rolling optimization scheduling strategy for virtual power plants based on model predictive control (MPC) is proposed. Considering the particularity of the electric vehicle units aggregated in the virtual power plant, an analysis of electric vehicle travel behavior is conducted to enable effective participation of electric vehicles in the charging and discharging scheduling plan of the virtual power plant. A multi-timescale day-ahead and intra-day operational framework for the virtual power plant is constructed, considering the constraints involved in system operation. An objective function incorporating intra-day balancing market and incentive-based demand response price incentives is introduced, and a multi-objective, multi-timescale optimization scheduling model based on the MPC rolling optimization algorithm is established for day-ahead and intra-day scheduling. By employing the MPC algorithm for real-time rolling optimization, the optimal day-ahead and intra-day scheduling plan for the virtual power plant is obtained. Simulation results indicate that the proposed strategy improved economic performance by 6.7%, increased carbon-credit revenues by 43.6%, reduced photovoltaic curtailment by 8291 kW, and decreased the output variability of distributed energy resources by 32%. The multi-timescale rolling optimization scheduling strategy presented in this paper addresses the volatility challenges of integrating distributed energy into the power grid. It offers theoretical value and serves as a practical reference for studying the large-scale integration of distributed energy resources on the user side.

To address the source‐load mismatch and photovoltaic (PV) curtailment caused by the large‐scale integration of distributed PV into distribution networks, this paper proposes an optimal control strategy for PV accommodation considering the coordination of a centralized energy storage system (CESS) and demand response. To achieve coordinated regulation on both the supply and demand sides, a multiobjective optimization model is established. It minimizes the comprehensive operating cost, including electricity purchasing, PV curtailment, CESS operation and maintenance, and the peak‐to‐valley load difference. On this basis, a time‐of‐use pricing mechanism is introduced to establish a piecewise linear load transfer rate model, which quantifies users’ dynamic electricity consumption behavior and optimizes the allocation of peak and valley loads. The proposed model is solved using particle swarm optimization (PSO). Case study results show that, compared with the scenario considering only CESS, the coordinated strategy reduces PV curtailment by 12.34%, electricity purchasing by 10.0%, and the total operating cost by 8.37%, demonstrating good performance in improving PV accommodation and the economic efficiency of the distribution network.

Large‐scale deployment of distributed photovoltaic (PV) systems brings challenges such as voltage violation and increased active power loss. Due to its high efficiency and low cost, the centralized energy storage system (CESS) has become a key technology to optimize distribution network operation. This paper proposes a multiobjective optimization model for CESS configuration in typical scenarios of Chinese rural residential users and enterprises, which considers voltage deviation, active power loss, and comprehensive costs. The analytic hierarchy process (AHP) is used to assign differentiated weights to different scenarios, transforming the multiobjective problem into a single‐objective problem. The particle swarm optimization (PSO) algorithm is then used to solve the problem, finally achieving collaborative optimization of the access location and capacity configuration of CESS. The validity of the proposed optimization model is confirmed by case studies in typical scenarios. In the rural residential scenario, CESS controls the voltage deviation within ±5%, with costs reduced by more than 50% compared to distributed energy storage systems (DESSs). In the enterprise scenario, CESS eliminates the voltage overlimit and reduces the cost by 53.95%. The proposed optimal configuration method for CESS effectively improves the voltage stability and economic performance, providing a low‐cost energy storage solution for the large‐scale application of distributed PV.