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The current paper explores a solar and wind energy system that is capable of operating in both: on-grid and off-grid regimes. The system contains two on-grid and one off-grid inverter for that purpose. The off-grid operation of the analyzed system is more vulnerable to instabilities. Experiments where made to show how inrush currents of electrical loads cause transient processes in such a renewable...
Digital-physical hybrid real-time simulation is considered to be an advanced method for future power system simulation. However, the physical interface will inevitably exist DC component, which causes negative effects on practical applications, such as degradation of simulation performance, damage to physical equipment, etc. A novel DC component elimination control strategy for the digital-physical...
In this paper we present modifications in the sphere decoder initially introduced in [1] and modified in [2] that allow for its implementation in transient operation. By investigating the geometry of the integer problem underlying direct model predictive control (MPC), a new sphere that guarantees feasibility and includes a significant smaller number of candidate solutions is computed. In a first...
This paper presents a novel hybrid adaptive droop controller to simultaneously regulate both the AC-side and DC-side parameters for power electronic converters in single-phase Microgrids. The main contribution of this paper is to integrate the AC-side and DC-side controllers. Unlike previously presented control schemes, where the DC-bus is considered as an infinite bus or constant voltage bus, the...
This paper proposes a scheme to improve the system transient performance by implementing a power command compensation structure in a single phase transformer less photovoltaic inverter with dynamic power decoupling. The drawback of the original control scheme in the transient performance is analyzed and shown in simulation results. The mechanism of the proposed control scheme is discussed in detail...
Islanding detection is an essential function of distributed grid-connected power generation systems, and an islanding detection method based on adaptive reactive power disturbance is proposed in this article. Importing the reactive power disturbance can make RLC loads generate the frequency shift when the power grid is disconnected for fault and the islanding will be detected. The reactive power disturbance...
As the large-scale integration of photovoltaic (PV) power station, a higher requirement is put forward by power grid analysis on the accuracy of PV station model. For the model of photovoltaic system is complex, and it requires solving large-scale model equation, which is not conductive for simulation and big data analysis when a large-scale PV power station connected to grid. This paper focuses on...
There is the high surge current emerging when the asynchronous traction motor is replaced by PMSM with power down-rejoining on. The high back EMF voltage exists when traction PMSM is passing the switching phase insulator. The reason is due to the constant value existence of the permanent magnet. Aiming at above mentioned problems, this paper analyses the reasons of causing transient surge current...
This paper discusses the challenges of paralleling dual modules with special focus on the currently introduced dual modules like LinPak, nHPD2, XHP, LV/HV100, etc. Compared with IHM/IHV Modules 3 to 4 times as many modules have to be paralleled to achieve the same output power. Therefore the parallel connection will play a major role in designing high power converters, used e.g. in traction applications...
The paper examines the work of the microgenerator inverter during two-phase short circuits. It has been shown that the cause of the oscillation is incorrect synchronization of the inverter. It has been demonstrated that the reduction of the oscillations can be achieved by adapting the synchronization signal to the representation of unbalanced system voltages.
Control of power electronic generations is important in microgrids and power systems. Droop control is proposed for reasonable power allocation among different inverters. Moreover, virtual synchronous generator is proposed to improve frequency dynamics in transient state. Therefore, inertia design in VSG is necessary for integrating power electronic generations into grids. Frequency dynamic and stability...
In this paper, we conduct a data-driven experimental analysis on a single-phase-to-neutral fault at a distribution grid in Riverside, CA using data from five distribution level phasor measurement units, a.k.a, Micro-PMUs. Of particular interest is to extract the time-line during the fault. With the high resolution, precision, and time synchronization of the data from Micro-PMUs, the hypothesis about...
Distributed renewable energy generations bring to attention the grid-connected inverter with LCL filter, whose control performance can be largely influenced by filter parameter variations. This paper has proposed a “comprehensive-loop-search, pattern-recognition, key-parameter-scan” method to evaluate the parameter variation influence, especially grid-side inductance and filter capacitance variation,...
Statistical link analysis and link budget calculation is the essential part for current high-speed system design. Because of the difficulty of low bit-error rate (BER) simulation at SPICE transient solver, several methods were proposed to simulate low BER in a short time. Single-bit response (SBR) method is the most basic method; it uses SBR to construct the arbitrary waveform under the assumption...
For three-phase four-leg inverter, symmetrical component method and double closed-loop control is a traditional method to sustain the symmetry of three-phase output voltage in steady-state under unbalanced load, but asymmetrical output voltage is still generated in transient process. By analyzing the transient process after sudden load change, this paper illustrates the change law of the output voltage...
Inverters in back to back (B2B) connection are utilized to convert the voltage and frequency of the power source to another format. Typical application of inverters is the wind power system. This study presents a B2B inverter for equal voltage and frequency format conversion in which one inverter works to get power from the grid to charge the DC capacitor and another inverter returns most of the active...
In this work, we investigate the dual gate positive feedback field-effect transistor (FBFET) using DC and transient TCAD simulation. I-V characteristics, subthreshold swing, and transient characteristics are analyzed. The FBFET has steep switching property and low off current. We design an inverter that can low power operate with the FBFET. By using the FBFET, the stand-by current is effectively suppressed...
Inverters in voltage control mode including droop control and virtual synchronous generator (VSG) are promising for interconnecting the renewable energy to the grid, which are both emulating the frequency and voltage regulating functions of synchronous generators through droop method. However, improper transient impact current and reactive power output are observed for inverters in voltage control...
The recently proposed concept virtual synchronous generator (VSG) has been intensively researched. Its core idea is to add a segment in traditional inverter control to simulate synchronous generator's rotor motion characteristic so that the distributed energy resources (DER) can have virtual inertia. VSG control usually contains output current amplitude limiting part to avoid too large current from...
The report is dedicated to the closed-loop design for a phase locking and a magnitude balancing of the three-phase inverter voltages to the three-phase grid voltages when the AC motor stator windings are switched to the AC power supply from the power frequency converter and backwards. The proposed control strategy for the AC drive with IGBT-inverter allows to decrease an inductance of current-balancing...
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