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The asymmetry of the inherent distributed capacitances causes the rise of neutral-to-ground voltage in ungrounded system or high resistance grounded system. Overvoltage may occur in resonant grounded system if Petersen coil is resonant with the distributed capacitances. Thus, the restraint of neutral-to-ground voltage is critical for the safety of distribution networks. An active grounding system...
The application of inverter power supply is introduced and defects and shortcomings of traditional inverter control method. The advantages and disadvantages of the control method are analyzed through the study of the double closed-loop control method and the repetitive control method, according to the characteristics of the control method, a compound control method is proposed, the simulation model...
The differential boost inverter (DBI) generates an alternating differential voltage from two dc-dc converters. The instantaneous output voltage can be higher or lower than the dc input voltage, however DBIs exhibit nonlinear control-to-output behavior in large-signal sense. Furthermore, switched capacitor cells may operate as a gain multiplier in classical converters. The integration of switched capacitors...
The photovoltaic (PV) grid-connected power generation has become an important direction of energy development. A grid-connected inverter is the key equipment in the PV grid-connected system. The efficiency and performance of the PV grid-connected inverter mainly depend on its topology and control technology. The PI controller has good dynamic and steady-state performance, which is widely used in the...
The paper presents the study of a process's calculation in circuits with incommensurable frequencies. In such circuits the analysis of processes is realized by the use of an additional independent variable. Definitions of RMS currents, voltages and active power are introduced on the base of double integrals. Calculations of an active power in circuits with two independent voltage sources and a single-phase...
A method to control the output current of a three-phase grid-tied inverter is presented. An LCL-filter is used to reduce the current distortion injected into the grid. The objective is to minimise current distortion and switching frequency to reduce losses. The control approach is based on finite control set model predictive control with sphere decoding to make the problem computationally tractable...
The transformer-less Photovoltaic (PV) power inverters are mostly well-liked and exceedingly recommended for grid-connected PV power systems because of low cost, small size and high efficiency. Nevertheless, the injection of Direct Current (DC) is effectively involved in grid-connected PV inverters without isolating transformers. An improved and efficient control method is presented in the paper,...
Increase in renewable power generation increases the power penetration to grid. Inverter plays a major role in power penetration. In this paper transformer-less single phase grid tie inverter based on synchronous reference frame current control is proposed to supply active power (P) to grid. This current control provides infinite control gain and zero steady state error ideally. The plant transfer...
The well-known active power-frequency and reactive power-voltage amplitude droop control is widely used in the coordinative control of parallel inverters in Microgrids. However, this conventional droop method may cause deviation on the frequency and voltage amplitude, which will affect the accuracy of power supply. This paper proposes a novel secondary control method to compensate this deviation....
With a still increase of grid-connected Photovoltaic (PV) systems, challenges have been imposed on the grid due to the continuous injection of a large amount of fluctuating PV power, like overloading the grid infrastructure (e.g., transformers) during peak power production periods. Hence, advanced active power control methods are required. As a cost-effective solution to avoid overloading, a Constant...
A semi-dual-bridge resonant converter derived from the popular dual-bridge resonant converter (DBRC) topology is proposed in this paper for applications requiring only unidirectional power flow such as various types of DC power supplies, battery chargers in electric vehicles and dc-dc stage of different types of photovoltaic inverters. Based on the similarity of topology to the DBRC converter, the...
One of the most important challenges associated with the droop control of parallel inverters in a microgrid is reactive power sharing between parallel units1. This paper proposes to integrate Direct Current Vector Control (DCVC) method2 with the droop control method to overcome this challenge. Another issue in droop control of parallel inverters in islanding mode is voltage level drop associated with...
For the independent DC link voltage control of the single phase cascaded multilevel PV inverter, this paper proposes an improved control strategy that consists only one total voltage loop and n feed-forward-based weighting factors. Actually, the multiple modulation signals have predictable ratios with each other because the series connection of the outputs of the H-bridges. Utilizing this feature,...
Electric Vehicles (EV) or Hybrid electric vehicles (HEV) require an electric motor which has high power density, high efficiency and a wide constant power operating region with flux weakening (FW) capability. Three phase Interior Permanent Magnet Synchronous Motors (IPMSMs) meet these criteria and are hence used in most commercial electrified vehicles. This work presents analysis, control system design...
This paper describes real time implementation of converter transformer tap changer controller on an X86 processor based hardware and Hardware-In-Loop validation of controller using Real Time Digital Simulator. The detailed Tap-changer controller algorithm and design had been implemented and verified in C language. The production code has been generated for the verified design and it has been ported...
MicroGrid is a local distribution system where loads are supplied by parallel-connected inverters controlled by decentralized active power/voltage frequency and reactive power/voltage magnitude droop controller. A paralleled ac system, such as a multi-inverter MicroGrid with droop controller, is susceptible to large variations in frequency/voltage magnitude. Therefore, the protection issues are very...
Half-Bridge Neutral Point Clamped (NPC) converter topology is particularly proper for transformer-less grid-connected photovoltaic (PV) systems since it avoids leakage currents circulation. In case of single-phase applications, resonant controllers are successfully applied to PV converters due to the optimum tracking and harmonic rejection capability in spite of the poor performances of the PI controllers...
In this paper, the idea of modelling the Inverter-Based Distributed Generators by using the concept of Electrostatic synchronous machines is discussed. A mathematical model of the inverter has been established which depends on the dc bus voltage, modulation index and frequency of the system. Two mathematical models have been developed: a small signal model and a steady-state model. These mathematical...
One of the most common solutions to the problem of feeding a three-phase induction motor from a single-phase line is using AC/DC/AC converter. An AC/DC/AC converter is composed by two stages, rectifying and inverting. The rectifying stage, or front-end, is generally implemented using a diode bridge rectifier or a boost rectifier. This paper evaluates the performance of a SEPIC (Single Ended Primary...
This paper discusses various transient trajectories for increasing the magnetization state (MS) of variable flux permanent magnet synchronous machines (VF-PMSMs), a class of PMSM where the magnets are demagnetized and remagnetized using the drive inverter during drive cycle operation. To manipulate MS, a magnetizing current pulse can be used, which may drive a large amount of flux linkage in the machine...
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