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With the rapid development of renewable energy and the continuous growth of new loads, VPP has become an important form of smart grid and energy internet due to its flexible and effective management of distributed energy. During the operation of Virtual power plant, there is a game relationship between the system operator and VPP, and they are in a non-complete information environment. However, most of the current game optimization modeling is under the condition of complete information, and the game model based on complete information cannot solve this problem. This article focuses on the VPP cluster trading problem based on non-complete information game theory, constructs a Bayesian game model for multiple VPPs with multiple subjects under the master-slave game framework by introducing the Bayesian concept to optimize the cluster transactions within VPPs, and verifies the effectiveness of the model through simulation experiments. The experimental results show that the multi-VPP multi-subject Bayesian game model established in the study can guarantee the privacy of each subject and effectively reduce PAR, thus ensuring the security and stability of the VPP network and reducing cost expenditures, which has practicality in actual VPP cluster transactions. [ABSTRACT FROM AUTHOR]

Studying the grid integration of renewable energy power generation is crucial for achieving the goal of carbon neutrality since it may have a significant influence on the secure and reliable functioning of the power system. In order to solve the problem of deviation impact caused by renewable energy fluctuations and the optimal scheduling of VPP (Virtual Power Plant), the study divides the internal aggregation unit of the virtual power plant into two parts to model. One part is the source equipment, including wind power generation equipment, gas turbine, gas boiler and waste heat boiler. And the other part is the generalized Energy storage, including electric vehicles, air conditioners and alternative response loads. Ultimately, a generalized energy storage-based virtual power plant operation optimization model is developed under multi-market coordination of electricity-gas-heat-carbon. According to the study's findings, adding more power-to-gas technology boosts revenue in the carbon trading market by 25.24 percent. The energy market's revenue is equal to that in the absence of a carbon trading market, and the income of the natural gas market increases by $ 32.96. The income of the carbon trading market is $ 181.51, and the final operating cost is reduced by $ 180.80, a drop of 7.81%. To sum up, the suggested approach may more effectively achieve the best distribution of different energy sources, increase the dependability of VPP operation, and make it more low-carbon. [ABSTRACT FROM AUTHOR]

The general mathematical model of the transcritical CO2 compressor was presented to assess the compressor efficiencies including isentropic efficiency and volumetric efficiency based on the thermodynamic theories and compressor structures. Furthermore, the prototype of the transcritical CO2 system was established and relative measurements were carried out to evaluate the precision of the simulation. Results showed that the volumetric efficiency of the compressor kept decreasing while the isentropic efficiency increased first and then kept almost constant and even declined with the increase in the pressure ratio. Besides, the indicated efficiency and volumetric efficiency declined slightly with the decrease in the suction density corresponding to the increase in suction superheating. As for the effects of compressor structures on the performances, the indicated efficiency increased sharply and then decreased gradually, while the volumetric efficiency kept declining with the increase in the cylinder diameter-to-height ratio, respectively. [ABSTRACT FROM AUTHOR]

An active islanding detection method based on frequency-locked loop (FLL) for constant power controlled inverter in single-phase microgrid is proposed. This method generates a phase shift comparing the instantaneous frequency obtained from FLL unit with the nominal frequency to modify the reference phase angle. An initial low frequency variable triangular disturbance is added to the phase shift in order to reduce non-detection zone and accelerate the detection process especially in the case of power matching. With the modified phase angle, the frequency at point of common coupling will be drifted away from the nominal frequency until exceeding the threshold because of the frequency positive feedback after islanding. Besides, FLL is introduced to this method in order to lock frequency quickly considering that the frequency is time-varying during the islanding detection process. Simulation and experiment have been done to evaluate this method. [ABSTRACT FROM PUBLISHER]

The topology of three-phase inverters can divide into a three-phase bridge structure and a single-phase combined structure. Three-phase combined inverters have their own advantages compared to normal three-phase bridge inverters, such as enhanced functionality, more choices for power resources, and simple maintenance, and so on. Therefore, it is worthwhile to study the technology of three-phase combined inverters, especially the study of the synchronous control method for three-phase combined inverters. In this paper, the synchronous control method for three-phase combined inverters was studied in the island operation and the process of pre-synchronization between island and grid-connected operations based on the Y/Δ connection of three single-phase energy storage inverters. When in the island operation, a synchronous control method of master/slave mode through a time benchmark synchronization and a phase adjustment synchronization was proposed based on a CAN (controller area network) bus communication. With the help of a CAN bus, an automatic network was designed to determine the A, B, and C-phase for the three inverters. A synchronization frame was designed and sent every 20 ms by the A-phase inverter, which was taken as the reference phase and corrected the phase error of the sine signal, to make sure that the time benchmark synchronized and the phase adjustment synchronized. And on this basis, when in the process of pre-synchronization between island and grid-connected operations, a synchronous control method of improved PLL (phase-locked loop) through frequency adjustment synchronization and logic judgment controller was proposed based on a SOGI (second-order generalized integrator). The improved PLL added a virtual PLL compared to the traditional PLL for the calculation of the real gird voltage phase angle. And the logic judgment controller used the difference between the output voltage phase angle of the inverters and the real gird voltage phase angle as the input, which implemented the smooth handoff from the island mode to a grid-connection. The actual experiments of the three-phase combined inverters were finished to verify the proposed synchronous control methods. The controller of the inverters was developed on the popular digital processor, which is TMS320F28335 from Texas Instrument. The CAN bus baud rate was set to 125 kB/s. The reference voltage was set to 220 V, 50 Hz, and the capacity of each inverter was 8kVA. As the result, when in the island operation, the proposed method implemented the three-phase output voltages of three-phase combined inverters and always kept the phase difference for 120°, and the average of the unbalance of three phase voltage in 5 minutes was 0.4%, which is less than the specified value 1.3% and meets the standards. When in the process of pre-synchronization between island and grid-connected operations, the maximum of the unbalance of three phase voltage in 5 minutes was 2.1%, which is less than the specified value of 2.6% and meets the standards. Therefore, both in the island operation and the process of pre-synchronization between island and grid-connected operations, the results showed that the synchronous control method for three-phase combined inverters is reliable and useful. [ABSTRACT FROM AUTHOR]