High-voltage pulse-generators can be used effectively for bacterial decontamination in water treatment applications. Applying a pulsed electric field to the infected water sample guarantees killing ...of harmful germs and bacteria. In this paper, a modular high-voltage pulse-generator with sequential charging is proposed for water treatment via underwater pulsed streamer corona discharge. The proposed generator consists of series-connected modules similar to an arm of a modular multilevel converter. The modules' capacitors are charged sequentially from a relatively low-voltage dc supply, then they are connected in series and discharged into the load. Two configurations are proposed in this paper, one for low repetitive pulse rate applications, and the other for high repetitive pulse rates. In the first topology, the equivalent resistance of the infected water sample is used as a charging resistance for the generator's capacitors during the charging process. While in the second topology, the water resistance is bypassed during the charging process, and an external charging resistance with proper value is used instead. In this paper, detailed designs for the proposed pulse-generators are presented and validated by simulation results using MATLAB. A scaled down experimental setup has been built to show the viability of the proposed concept.
A Four-Switch Three-Phase SEPIC-Based Inverter Diab, Mohamed S.; Elserougi, Ahmed; Massoud, Ahmed M. ...
IEEE transactions on power electronics,
09/2015, Letnik:
30, Številka:
9
Journal Article
Recenzirano
The four-switch three-phase (FSTP) inverter has been proposed as an innovative inverter design to reduce the cost, complexity, size, and switching losses of the dc-ac conversion system. Traditional ...FSTP inverter usually operates at half the dc input voltage; hence, the output line voltage cannot exceed this value. This paper proposes a novel design for the FSTP inverter based on the topology of the single-ended primary-inductance converter (SEPIC). The proposed topology provides pure sinusoidal output voltages with no need for output filter. Compared to traditional FSTP inverter, the proposed FSTP SEPIC inverter improves the voltage utilization factor of the input dc supply, where the proposed topology provides higher output line voltage which can be extended up to the full value of the dc input voltage. The integral sliding-mode control is used with the proposed topology to optimize its dynamics and to ensure robustness of the system during different operating conditions. Derivation of the equations describing the parameters design, components ratings, and the operation of the proposed SEPIC inverter is presented in this paper. Simulation model and experimental setup are used to validate the proposed concept. Simulations and experimental results show the effectiveness of the proposed inverter.
Power generation through wind is expected to play a major role in the world's future energy portfolio. Nevertheless, wind power integration remains a challenging research area due to the special ...characteristics of wind power generation. Specifically, offshore wind has received significant attention worldwide due to the vast generation potential available. The electrical infrastructure of offshore wind farms is thus of significant importance. The multi-terminal HVDC solution represents a preferable solution and has shown promise in solving wind farm interconnection problems. Droop control techniques have been proposed as a means to regulate the DC voltage and facilitate the automatic coordination between different converters without the need for fast communication between units. Different methodologies have been developed to select the droop gains to satisfy the system performance specifications. In this work, a control design methodology is proposed for power sharing among the multi-terminal HVDC feeders providing that the power transmission efficiency is optimized. A simulation study on a 400-kV/1000-MW four-terminal HVDC transmission topology is conducted to ensure the validity of the proposed methodology.
Multilevel inverters have been widely used in various applications, as they provide output voltage with better quality, lower dv/dt, and lower Total Harmonic Distortion (THD). Multilevel inverter ...such as Neutral Point Clamped (NPC) inverter uses a large number of semiconductor devices (IGBTs and diodes) which negatively affects the inverter cost and efficiency. Recently, a three-level (3L) F-type inverter has been proposed with lower switch voltage stresses, cost, and losses compared to 3L T-type and NPC inverters. This paper proposes a five-level (5L) F-type inverter as an extension for the 3L F-type inverter. Like a 5L NPC inverter, the voltages of the involved dc-link capacitors should be kept at a certain voltage level. To achieve that, buck-boost converter-based Equalization Channels (ECs) are employed. To show the pros and cons of the 5L F-type inverter, a comparison between the proposed inverter and other existing multilevel inverters has been held. The numerical assessment also shows that the proposed architecture has a lower kVA rating and losses than the conventional 5L NPC inverter. Finally, different Simulation and experimental results of the proposed 5L F-type inverter are presented. The presented results show the viability of the proposed converter.
•We studied the performance of single loop control of the Inverter Based Distributed generators at faults, we found it not stable.•We made a Matlab model to study how the different fault current ...generated by the IBDG affect the power system protection.•We proposed with mathematical analysis an additional control loop to solve the problems at faults.•We built the necessary experimental setup using two voltage source inverters connected to the grid.•The results of the proposed method are presented.
Inverter-based distributed generation (IBDG) is characterized by its negligible fault current contribution compared with synchronous generators due to its inherent non-overload capabilities. Thus, IBDG hardly affects the fault current level; this shadows the conventional protection schemes resulting in improper system protection especially with a high penetration of IBDGs at high power levels and/or in island operation mode. This paper presents an experimental investigation of two scenarios for IBDG fault current contribution under different fault conditions. In the first scenario, the inverter is controlled to produce zero output current or is disconnected upon fault occurrence, which is the case for most commercial grid-connected inverters. In the second scenario, the inverter contributes its rated current to the fault. The practical selection may be questionable and is affected by the fault level, employed protection scheme, and the penetration level of IBDGs. The introduction of double-loop proportional-resonant (PR) current controller is investigated using three case studies applying the previously described fault current contribution scenarios. The double-loop PR controller is found favorable when the inverter is designed to contribute its rated current to the fault. This conclusion is verified experimentally in this work.
► This paper presents a power control strategy to charge/discharge a flywheel DFIM storage system. ► The controller is based on conventional vector control system supplemented by an ANN-based current ...decoupling network. ► The controller is designed to avoid overloading both stator and rotor circuits while the flywheel charges/discharges. ► The validity of the developed concept is confirmed by computer simulation for a medium voltage 1000hp FW-DFIM. ► The simulation is carried out for UPS applications and power leveling to electric power delivered by wind generators.
A large-capacity low-speed flywheel energy storage system (FESS) based on a doubly-fed induction machine (DFIM) consists of a wound-rotor induction machine and a back-to-back converter rated at 30–35% of the machine power rating used for rotor excitation. This system has been promoted as a viable mean of energy storage for power system applications as grid frequency support/control, uninterruptible power supply (UPS), power conditioning, and voltage sag mitigation. This paper presents a simple power control strategy based on artificial neural networks (ANN) to charge/discharge a flywheel DFIM (FW-DFIM) storage system while maintaining controllable grid side power. The proposed controller is based on conventional vector control system supplemented by an ANN-based current decoupling network used to develop the required rotor current components based on the required grid power level and flywheel instantaneous speed. The controller is designed to avoid overloading both stator and rotor circuits while the flywheel is charged/discharged. Additionally, it avoids using the required outer power loop or a hysteresis power controller, hence, simplifies the overall control algorithm. The validity of the developed concept along with the effectiveness and viability of the control strategy in power system applications is confirmed by computer simulation using Matlab/Simulink for a medium voltage 1000hp FW-DFIM. The simulation study is carried out for uninterruptible power supply (UPS) applications and power leveling to improve the quality of electric power delivered by wind generators.
The integration of renewable energy sources in Medium-/High-voltage DC grids has called up continuous research to develop DC-DC conversion systems. This paper presents a hybrid modular multilevel ...DC-DC converter topology which successfully overcomes the issue of capacitors voltage imbalance during DC-DC conversion. In the proposed topology, single MMC leg is employed with half-bridge submodules in the upper arm and full-bridge submodules in the lower arm along with soft-switched high-voltage valves. The proposed hybrid modular multilevel converter has inherited arm energy equalization with the help of the parallel connectivity of involved arms’ capacitors. During the equalization period, the series-connected upper arm capacitors are connected in parallel to the series-connected lower arm capacitors to transfer the energy between the involved arms which results in operating with balanced capacitors voltages. The proposed modular DC-DC converter is a bidirectional converter which allows power flow from high-voltage side to low-voltage side and vice versa, i.e., it can be operated successfully as a DC transformer. The operational concept of the proposed configuration, control strategy, and parameters design are presented. Simulation results are presented along with experimental results of a scaled-down prototype to validate the proposed approach. Simulation and experimental results show the viability of the suggested approach.
The modular multilevel converter (MMC) is a promising candidate for high-/medium-voltage high-power applications such as medium voltage ac drives due to its modularity, reliability, and scalability. ...The main challenge of a conventional MMC is low-frequency operation. Capacitor voltage ripple is inversely proportional to the operating frequency. Hence, operating at low frequency necessitates employing large submodule capacitances to limit voltage ripple or the utilization of energy equalization modules (EEMs). The first option negatively affects converter lifetime, and the second option requires a large number of semiconductor devices and isolating transformers. In this article, a modified MMC topology with self-energy equalization is proposed to ensure converter operation with balanced capacitor voltages with low ripple during zero-/low-frequency conditions. Operating with balanced capacitor voltages with low ripple is achieved by maintaining the same energy level in the involved upper and lower arms. A low device count alternative to the EEMs approach is proposed in this work. Detailed illustration of the operational concept and design of the associated passive components is presented. The performance of the proposed medium voltage ac drive is elucidated through simulation and experimental results.
Modular multilevel converter (MMC)-based AC motor drives are emerging trend-research. They ease medium-/high-voltage handling in high-power applications with reduced footprint and life-cycle costs. A ...known challenge concerning their operation is the zero-/low-speed operating condition. The recent techniques proposed to improve operation during that interval, implement complex hardware/software approaches. To cope with this issue, this paper proposes multiphase machines for MMC-based AC-drives. Among several advantages regarding the power splitting, multiphase machines provide additional degrees of freedom compared with their three-phase counterparts. Novel exploitation to these additional degrees of freedom is proposed in this paper by injecting a secondary current component in the load current with specific magnitude and frequency during zero-/low-speed intervals enabling the motor to function duly. Since the control of these secondary components is already inherited in the current controller structure of any multiphase machine, no additional algorithms or sensors will be required. In this paper, a three-level five-phase MMC-based distributed winding induction machine drive system for medium-/high-voltage applications is investigated during low-speed operation as well as starting from standstill to rated speed. Two different control options are proposed using capacitor voltage measurements or under sensorless operation in order to reduce the cost and complexity in the case of a high number of MMC levels. The experimental results have been obtained with a downscaled drive system to verify the proposed solution.
Modular multilevel converters (MMCs) have become one of the most promising topologies for high-voltage dc-ac conversion. DC-side fault blocking capability of the MMC has prompted significant research ...in recent years. In this paper, a new switched capacitor submodule (SCSM) for MMCs is proposed which provides operation with DC fault blocking capability. In addition, successful voltage balancing is achieved with half the number of voltage sensors used with existing MMC cells. Generally, conventional sensor-based balancing techniques require a significant amount of measurements, 2m(N-1) voltage sensors, and 2m current sensors for an N-level m-phase MMC. The proposed cell will thus aid in reducing the complexity of the control system. A detailed illustration of the operational concept of the proposed architecture is presented in this paper. A comparison between the proposed SCSM and other existing MMC cells has been included to highlight the benefits of the proposed SCSM. A simulation model for an MMC-based HVDC system along with the proposed cell has been built to test its performance during normal as well as abnormal operating conditions. The simulation results show the effectiveness of the proposed architecture.
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