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AC-DC converters are mostly used as power supplies for microelectronic systems, battery chargers, wind energy applications, electric appliances in household and dc motor drives. Switched-capacitor (SC) network based converters can be good solution to the challenges of 21st century having high voltage conversion ratio and low EMI emissions. The application of this type of converters is in microprocessor...
Circuit breaker (CB) installed for capacitor bank is the CB which commonly experiences the switching process due to the capacitor bank function as a voltage regulator. In closing switching process, CB encounter transient condition due to inrush current. In this paper, the simulation for studying the inrush current characteristic of capacitor bank switching in Indonesia has been performed. Simulation...
This paper discusses the active and reactive power control method for a modular multilevel converter (MMC) based grid-connected PV system. The voltage vector space analysis is performed by using average value models for the feasibility analysis of reactive power compensation (RPC). The proposed double-loop control strategy enables the PV system to handle unidirectional active power flow and bidirectional...
Voltage deviations of dc-link capacitors are the main problem of multilevel diode-clamped converters (DCC). In this paper, a novel carrier-based voltage balance method is proposed to balance the dc-link capacitors of five-level DCCs. The proposed method is characterized by injecting proper zero-sequence voltages in the modulation signals of carrier-based modulators. The effects of the injected zero-sequence...
This paper introduces a three-phase grid-connected inverter for commercial-scale photovoltaic systems. The circuit topology combines an electrolytic-capacitor-less and ac-inductor-less active bridge with a parallel-connected PWM inverter acting as an instantaneous reactive power compensator. The active bridge, called a 120°-conduction inverter, operates at the switching frequency equal to the grid...
This paper presents Direct Power Control (DPC) based on instantaneous power theory is presented. The simulation of a grid connected five level inverter via an inductive filter with a new direct power strategy is used. However, this control method is similar to the classic DPC method, in which used triangles instead of the sectors. Furthermore, the regulation of DC link without interfering the hysteresis...
A novel switching power loss estimation method for modular multilevel converters (MMCs) with the nearest level modulation (NLM) is introduced in this paper. It focuses on the switching actions caused only by change of the inserted submodule (SM) number per arm, named as the essential switching transitions. Every essential switching action can be identified under the assumption of ideal sinusoidal...
In this paper, a predictive direct power control (P-DPC) strategy for a three level NPC rectifier under ideal grid voltage is proposed, discussed and applied. With the proposed P-DPC strategy, the control targets are the active power, the reactive power and the neutral potential voltage; neither hysteresis comparators nor switching table are needed; sinusoidal input current with low total harmonic...
Although the mechanism of electric energy flow for nonsinusoidal conditions is well described today, so fare is not yet available a generalized power theory, and theoretical calculations for the design of such devices as active filters or dynamic compensators. Therefore the task of designing compensators for optimize energy transmission with nonlinear time-varying loads in nonsinusoidal regimes is,...
A single phase transformer-less inverter is introduced in this paper. The negative polarities of the input voltage and output terminal have common ground. Therefore, the leakage current problem that is common in PV systems is eliminated naturally. In addition, the proposed inverter has fewer components compared with its counterparts and only one switch conducts during the active states which enhance...
This paper proposes a self-tuning model predictive direct power control (MPDPC) strategy for power flow control and power quality improvement in grid-connected power converters. At each sampling instant, a fuzzy logic controller is used to determine online the best weighting factor values for a given operating point. These values are then used to solve the multi-objective optimal control problem associated...
The increasing penetration of electric vehicles (EVs) will bring great challenges to the secure and economic operation of distribution networks. On the other hand, coordinated charging of EVs can alleviate the adverse impacts of charging loads and even increase the efficiency of distribution network operation. This paper aims at optimally scheduling the daily charging of EVs and the daily on/off switching...
The Switched Capacitor (SC) Circuit is investigated in this paper as a Solid-State Fault Current Limiter and interrupting device (FCLID) with power factor correction suitable for low-voltage distribution networks. It was applied so far successfully as a power factor and harmonic current compensator and as a Switched Capacitor Circuit inverter. In this application it is inserted in series with the...
Performance of multilevel inverters (MLI) are distinguished because of their low harmonic waveform generation, low filtering requirements on AC side and high voltage application. Among different (MLI) topologies, cascaded multi-level inverters (CMLI) are easier to implement and are much more cost effective. The main drawback of multilevel inverters is requirement of more than one isolated DC source...
A solid state transformer (SST) is going to be a vital part of the future grid due to its attractive features such as step-up/step-down of grid voltage, provision for an intermediate DC bus to interface renewable energy source and energy storage, controlled bidirectional power flow between two girds etc. Even though the reliability of the SST is questioned due to high switching device count, redundant...
An HVDC system based on a Cockcroft-Walton (CW-HVDC) topology is presented and a novel strategy is proposed to analyze and control the converter. In the connection to the grid the CW-HVDC uses a 3×2 matrix converter. The CW-HVDC voltage state-space vectors are derived and used to control the AC currents, guaranteeing nearly unitary power factor in the connection to the grid. Sliding mode controllers...
This paper proposes a novel switched-capacitor (SC) ac-ac converter using nested voltage equalizers. In the proposed ac-ac converter, a part of the capacitor voltage of a voltage equalizer is converted by other voltage equalizers. For this reason, the proposed ac-ac converter can achieve not only high step-up/step-down gain but also fewer circuit components than conventional SC ac-ac converters. Furthermore,...
High inertial loads are abundant in the industry and most of them are direct on line starter type induction machines with double cage rotors. Due to their higher starting time higher power dissipation in the rotor makes the rotor wear out and eventually gets destroyed. A new starting method proposed herein makes the motor start quickly and smoothly by using an inverter. After reaching it's steady...
This paper presents a single phase converter topology that integrates a second harmonic energy buffer. The buffer is formed by converting one branch of the converter to use half-bridge cells, similar to an MMC type design. The energy buffer allows complete elimination of the 2nd harmonic ripple from the main DC bus and reduces overall DC link capacitor size. The topology also reduces the rms current...
Continuous conduction mode (CCM) boost power factor corrector (PFC) is widely used for high power applications such as server power supply. PFC performs AC/DC conversion with nearly unity power factor (PF) and low current harmonic distortion. However, the electromagnetic interference filter capacitors in front of the bridge diode and input filter capacitor behind the bridge diode incur phase leading...
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