Current Issue : October - December Volume : 2020 Issue Number : 4 Articles : 5 Articles
In order to realize the unsupervised extraction and identification of fault features in power electronic circuits, we proposed a fault\ndiagnosis method based on sparse autoencoder (SAE) and broad learning system (BLS). Firstly, the feature is extracted by the\nsparse autoencoder, and the fault samples and feature vectors are combined as the input of the broad learning system. The broad\nlearning system is trained based on the error precision step update method, and the system is used to the fault type identification.\nThe simulation results of the thyristor fault diagnosis of the three-phase bridge rectifier circuit show that the method is effective\nand has better performance than other traditional methods....
Virtual synchronous generator control is considered as an effective solution to optimize the\nfrequency response characteristics of doubly fed induction generator. However, due to the insufficient\ncontrol bandwidth of the original virtual synchronous generator, it has little control effect over the\noscillating components of the power caused by the unbalanced grid voltage. Therefore, long-term\nunbalanced voltage will cause a series of problems, such as distortion of stator and rotor currents, as\nwell as oscillations of power and electromagnetic torque, which seriously affect the power quality\nand the operating performance of the doubly fed induction generator. To solve these problems,\nthe concept of extended power is introduced, and the second-order generalized integrator-based\nresonant controller is used to control the extended power and traditional power. Control targets of\nthe extended power method are discussed and extended, so that the doubly fed induction generator\nsystem using extended power resonant control-based virtual synchronous generator control can\nrealize three different control targets under the unbalanced grid condition. The three control targets\nare: balanced and sinusoidal stator current, sinusoidal stator current and constant active power,\nand sinusoidal stator current and constant reactive power and electromagnetic torque. The three\ncontrol targets can also be flexibly switched according to the real-time requirements of the grid with\nunbalanced voltage. The simulation results verify the effectiveness of the control method....
In this paper, the problem of finite-time tracking is investigated for switched buck power converters based on the pulse width\nmodulation (PWM) technique. For the continuous model, an equivalent continuous controller is solved by the backstepping\ntechnique, such that all signals are finite-time stable. PWM-based finite-time tracking with the equivalent control input is\nproposed for the switched buck converter, such that the tracking error converges to an arbitrarily small neighborhood of the origin\nin finite time, and the origin of the closed-loop system is practically finite-time stable. Simulation results are given to demonstrate\nthe effectiveness of the proposed schemes....
Model and parameters are the indispensable conditions for the simulation calculation of\npower systems with a high proportion of photovoltaic power generation. Conventional models of\npower electronic devices are difficult to meet the requirement of power system electromechanical\ntransient simulation, and the parameters are difficult to obtain. Aiming at this problem, this paper\nproposes a structure of an electromechanical transient simulation model of a photovoltaic power\nstation and designs a set of photovoltaic power generation transient characteristic test systems\nbased on a fault simulation device. Through a disturbance test and model parameter identification,\nthe electromechanical transient simulation model and parameters of photovoltaic power generation\nare obtained. In this paper, based on the test system, the electromechanical transient characteristics of\na certain type of photovoltaic inverter are modeled. The results show that the model can successfully\ndescribe the electromechanical transient characteristics of photovoltaic power generation, and the\nsimulation results obtained based on the model parameters have a good fitting degree compared\nwith the measured curve....
Bipolar DC grids have become an adequate solution for high-power microgrids. This is\nmainly due to the fact that this configuration has a greater power transmission capacity. In bipolar DC\ngrids, any distributed generation system can be connected through DC-DC converters, which must\nhave a monopolar input and a bipolar output. In this paper, a DC-DC converter based on the\ncombination of single-ended primary-inductor converter (SEPIC) and C´ uk converters is proposed,\nto connect a photovoltaic (PV) system to a bipolar DC grid. This topology has, as main advantages,\na reduced number of components and a high efficiency. Furthermore, it can contribute to\nregulate/balance voltage in bipolar DC grids. To control the proposed converter, any of the techniques\ndescribed in the literature and applied to converters of a single input and single output can be used.\nAn experimental prototype of a DC-DC converter with bipolar output based on the combination of\nSEPIC and Cuk converters was developed. On the other hand, a perturb and observe method (P\nand O) has been applied to control the converter and has allowed maximum power point tracking\n(MPPT). The combined converter was connected in island mode and in parallel with a bipolar DC\nmicrogrid. The obtained results have allowed to verify the behavior of the combined converter with\nthe applied strategy....
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