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Pulsed electric field is a commonly used and effective disinfection method in drinking water treatment applications. In this paper, a transformerless unipolar/bipolar high-voltage pulse generator is presented with well-regulated pulsed output voltage for drinking water treatment via underwater pulsed corona discharge. The proposed high-voltage pulse generator is fed from a relatively low-voltage dc supply. Then, capacitor–diode voltage multiplier centrally fed from a dc–dc boost converter is used to elevate the input voltage to a proper high-voltage level. Finally, a modular multilevel converter is employed to chop the elevated voltage into unipolar or bipolar pulsed output voltage (based on the user selection). The suggested arrangement provides a high-voltage gain with relatively low-voltage components, i.e., neither high-voltage nor series-connected components are needed in the proposed approach. A comparison between the proposed approach and the other Marx-Based pulse generators has been held to show the merits of the proposed approach. A detailed design of the generator passive components and semiconductor devices has been presented. Simulation and experimental results are presented for the unipolar as well as the bipolar pulsed output to validate the proposed concept. [ABSTRACT FROM AUTHOR]

In order to generate bipolar high-voltage (HV) pulses across certain load from HV dc (HVdc) power supply, a voltage source inverter (VSI) stage should be inserted between the load and the supply. In order to meet the required HV level, series connection of semiconductor devices should be employed with dynamic voltage sharing between the involved devices. Modular multilevel converter (MMC) can be used instead of the conventional two-level VSI to alleviate the complexity introduced by the deployment of series-connected devices. The voltage level of the HVdc power supply and the voltage rating of the available semiconductor devices determine the suitable number of MMC voltage levels ( $N$ ). Capacitor voltage balancing is a vital issue for proper operation of the MMC. In general, conventional sensor-based balancing techniques require a significant amount of measurements, which increases the complexity of the system. In addition, the high dv/dt during switching times causes electromagnetic interference, which may adversely affect the accuracy of the measurements. In this paper, a sensorless voltage balancing technique is proposed for the MMC-based bipolar HV pulse generator that reduces the system sensitivity, cost, and complexity. A detailed illustration of the proposed approach is presented in this paper. The simulation and experimental results are used to validate the proposed concept. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM PUBLISHER]