High Voltage Conversion Research Articles

Имитатор импульсных высоковольтных перенапряжений

The electrical circuit of a simulator of pulse high voltage overvoltages with an amplitude of up to 10 kV DC, which is intended for testing the stability of solid-state power converters to emergency conditions according to item 4.9.3.5 of State Standard GOST 33726-2016, is proposed. By using the developed simulator, a high voltage pulse with the required values of amplitude, duration, and rising and falling rates can be obtained. Analytical expressions are derived that describe, with sufficient accuracy, the transients in the electrical circuits of the proposed pulse high voltage overvoltage simulator, which is confirmed by computer simulation carried out in the MATLAB Simulink environment. Based on the obtained theoretical results, a mockup simulator for testing the stability of a high-voltage power converter to overvoltage of a given shape and amplitude has been developed. The results of practical use of the developed simulator on the example of testing the PSN110 U1 auxiliary converter are given. The article may be of interest to specialists who design equipment for carrying out overvoltage tests of solid-state high-voltage converters for both railway transport and industrial applications.

Narrow band-gap materials with overlapping absorption simultaneously increase the open circuit voltage and average visible transmittance of semitransparent organic solar cells

Overlapping near-infrared absorption not only does not reduce short-circuit current density (JSC), but also can ensure a high average visible transmittance (AVT) and get a high open-circuit voltage (VOC) and power conversion efficiency (PCE) at the same time.

A Novel Relaying Scheme Using Long Short Term Memory for Bipolar High Voltage Direct Current Transmission Lines

In this paper, a novel relaying scheme is proposed for bipolar line commutated converter (LCC) high voltage direct current (HVDC) transmission lines that detects the fault, identifies the pole of fault and estimates the location of the fault. The scheme uses features extracted from rectifier end DC current and voltage signals. Long short term memory (LSTM), a deep learning method has been designed as classifier as well as predictor for carrying out different relaying tasks. Three modules have been designed namely LSTM-FD (LSTM module for fault detection (FD)), LSTM-FI (LSTM module for fault pole identification (FI)) and LSTM-FL (LSTM module for fault location estimation (FL)). The voltage and current signals are obtained from measuring units. Then with a moving window of one cycle, the RMS of signals is calculated. The current and voltage features are obtained in the time domain. The voltage and current features obtained are used as input to fault detection and fault pole identification module. For fault location estimation, half cycle samples of RMS current and voltage after the fault have been taken. From half cycle sample, maximum value of current and minimum value of voltage has been obtained. This single value of current and voltage are used as input feature to the fault location module. All the relaying modules have been tested varying fault types, locations, resistances, smoothing reactors, noisy signals, etc. Sensitivity and reliability of the proposed relaying scheme is 100% with all the tested fault cases. Error in location estimation is within 1% for all the tested fault cases. Advantage of the method is that it does not require communication link. Another advantage of the proposed method is that it can work with low sampling frequency. Additionally, reliability and sensitivity of proposed method is very high, hence can be used as an alternative to travelling wave based relaying schemes.

Implementation of Double Loop Controller Tuned Super Lift Luo Converter and Unipolar Inverter for Solar Fed Grid Application

The main objective of this article gives detail about the solar power conditioning system to make the PV power generation with high power quality before it is connected to the grid. The PV side DC-DC conversion is done by Positive Output Elementary Super Lift Luo converter (POESLLC) with high voltage conversion ratio for better performance. The grid side AC conversion is done by simply double loop controller is introduced in this system to keep less variation and to maintain the grid voltage constant for line and load variations. DC power received from the solar panel is stabilized in the POESLLC converter with double loop controller which consists of PI controller on the outer loop and hysteresis current controller inner loop. Open-loop Pulse Width Modulation (PWM) based unipolar full-bridge inverter is used to maintain the grid parameters to meet the power quality issues. This system avoids the closed-loop controller for inverter and also omits the Maximum Power Point Tracking (MPPT) algorithm in DC to DC conversion. It has some advantages such as fewer components, less weight and avoids complexity in controllers which inject steady current to the utility line. The effectiveness of the converters is verified through MATLAB Simulink.

Stabilization of wind farm integrated transmission system with input delay

<abstract> In the process of large-scale wind farms integration, the time delay is usually caused by the introduction of wide area control signal, which leads to the unstable operation of integrated transmission system. In order to solve this problem, using the control principle of interconnection and damping assignment passivity-based (IDA-PB), this paper puts forward a control method which applies voltage source converter high voltage direct current (VSC-HVDC) technology to the integrated system of time-delay wind farm and keeps the system running stably. In this method, the framework of time-delay port controlled Hamiltonian (PCH) system is constructed, and the energy shaping of the system is carried out by extending the IDA-PB control principle, thus the feedback controller of the system is designed. Around the problem of time-delay stabilization, the stability criterion is obtained by constructing Lyapunov-Krasovskii functional and introducing free weighting matrices. Finally, the simulation results show that the proposed method can effectively solve the time delay problem of the integrated transmission system and avoid the performance deterioration of the system. </abstract>

Voltage Correlation Based Single Pole-to-Ground Fault Detection of MMC-HVDC Transmission Line

Through analysis of various fault voltage characteristics of modular multilevel converter high voltage direct current (MMC-HVDC) transmission system, it shows that the positive and negative voltage relationships of direct current transmission lines with single pole-to-ground faults are obviously different from other faults. Hence, Pearson correlation coefficient is used to describe the degree of difference in this work. In the case of single pole-to-ground fault, correlation coefficient is positive and close to 1, while as for other failures, correlation coefficient is negative and close to −1. This article analyzes the mechanism of correlation coefficient to withstand transition resistance and verifies the effectiveness of the proposed method under high resistance grounding fault. A novel scheme is proposed by combining the quantity sum of voltage variation characteristics, which can effectively identify fault pole. The proposed scheme needs smaller time window and owns high efficiency, as well as great robustness to transition resistance.

A High Step-Up/Step-Down Input-Parallel Output-Series ZVS Bidirectional Converter With Coupled Inductors

This article introduces a nonisolated bidirectional converter with high-voltage conversion ratio. In the proposed converter, by integrating the two-phase low-voltage-side (LVS)-parallel high-voltage-side (HVS)-series bidirectional converter with the coupled inductors, features, such as high voltage gain, low voltage stresses, current sharing, and current ripple cancelation, are achieved. Due to the proposed converter's operation in triangular conduction mode, the desirable benefits of zero voltage switching, diode reverse recovery elimination, and reduction of converter filter inductors and, consequently, leakage inductors are obtained. To recycle the leakage inductors’ energy and to solve the related difficulties for both operation modes, a simple passive clamp with the minimum number of elements is utilized. Also, to improve the light-loads’ efficiency, the variable frequency control is developed. The proposed converter is comprehensively analyzed, and to verify the analysis, the experimental results are provided.

An Interleaved Zero-Voltage Zero-Current Switching High Step-Up DC-DC Converter

An interleaved zero-voltage zero-current switching (ZVZCS) high step-up DC-DC converter is proposed for modern photovoltaic power generation systems. The proposed converter can achieve high voltage conversion gain without operating under extreme duty cycles. The voltage conversion gain can be readily adjusted by selecting different numbers of the diode-capacitor multiplier (DCM) cells in the circuit at the design stage. Moreover, with the passive snubber circuit in the proposed converter, all power switches and diodes in the DCMs can achieve zero-voltage turn-off and zero-current turn-on, which effectively reduces switching losses and increases the overall converter efficiency. The operational principles and analysis of the performance analysis with two DCMs are presented for demonstrative purpose. The effectiveness of the proposed ZVZCS DC-DC converter is validated using an 800W experimental prototype.

State Space Modeling and Stability Analysis of a VSC-HVDC System for Exchange of Energy

Nowadays, relevant actors are searching for solutions to produce energy with a low impact on the environment. Indeed, transmitting power via large distances with maintaining low losses is one of the main challenges. To improve electricity communication between countries and offshore wind, a new interconnections line must be built. Therefore, Voltage Source Converter High Voltage Direct Current (VSC-HVDC) transmission is incoming as the exceptive technology in order to address the challenges related to the integration of future offshore wind power plants. In spite of its many advantages, VSC-based HVDC transmission systems can experience unexpected instability and interaction phenomena: Small disturbances that occur continually in VSC-HVDC transmission systems due to the complex VSC based interconnections and an important number of components with non-linear nature that may cause failure. Thus, before installing the HVDC system, there is a significant need for studying a hybrid AC-DC system to guarantee the reliable and stable operation. This paper deals with the stability of a VSC-HVDC system by the use of a small signal stability method; such procedure enables to study the stability of a linearized VSC-HVDC system through state-space modeling and eigenvalue-based stability analysis.

Control and Derived Topologies of Parallel Hybrid Converter

The modular multilevel converter (MMC) is the most preferred voltage source converter high voltage direct current (VSC-HVdc) topology. However, its limitations such as, large energy storage requirements and a large number of devices and capacitors required in its chain-links (CLs), have led to the development of some hybrid multilevel converter topologies. These topologies aim to address the major technical constraints of MMC. The parallel hybrid converter (PHC) is such a hybrid topology, which has evolved as a promising alternative for high power applications because its CLs are not subjected to the fundamental component of ac current and hence the size of its submodule capacitors is substantially lower. Furthermore, for the same power rating, the device count in PHC is only a fraction of that in MMC. However, the PHC suffers from some operational constraints. The dc and ac sides of PHC are strongly coupled, which leads to a single stable operating point resulting in a fixed output voltage if a dedicated controller is not used to tackle this issue. Moreover, the PHC loses control during dc-side faults and it also necessitates a bulky dc filter inductor to filter the dc-side harmonics. Various advanced control methods and derived PHC topologies have been proposed in literature to eradicate these shortcomings of the PHC. This article presents a detailed analysis and review of these state-of-art control strategies and derived PHC topologies. The capability of the PHC and the derived topologies to ride through ac and dc faults are also discussed. This article contributes in summarizing key benefits and limitations of various existing control methods through extensive analyses, simulation, and experimental studies.

A high efficiency soft‐switched DC–DC converter with high voltage conversion ratio

SummaryThis work proposes a kind of DC–DC topology with a higher voltage conversion ratio. The suggested converter utilizes a coupled inductor and a voltage multiplier cell to enhance the voltage conversion ratio. The voltage multiplier cell has the feature of the clamping circuit, which can decrease the maximum voltage of the semiconductors elements. In the presented structure, only one lower ON‐state resistance (RDS‐ON) power switch is utilized that makes the control circuit to be simple. The proposed converter has soft‐switching features such as zero‐current switching (ZCS) and zero voltage switching (ZVS) that lead to decrease the diodes reverse recovery losses and increase the efficiency. Besides, the ripple value of the input current is lower than the other similar works. The high efficiency and low input current ripple make the suggested converter suitable for photovoltaic (PV) applications. In order to approve the technical analysis of the recommended structure, technical investigations and comparison study with some similar structures are carried out. Finally, for demonstrating the advantages of the presented structure, a laboratory circuit is built with 12‐V DC source voltage, 120‐V load voltage, and power rate of 100 W in 50‐kHz operation frequency.

A Bidirectional DC–DC Converter With High Voltage Conversion Ratio and Zero Ripple Current for Battery Energy Storage System

In this article, a novel bidirectional dc-dc converter (BDC) consisting of an active switched-inductor (A-SL) cell, a zero current ripple cell and an auxiliary capacitor cell is proposed for the battery energy storage system. The proposed BDC integrates with the advantages of high voltage conversion ratio, low power switch voltage stresses, zero ripple current on the low voltage side (LVS), and constant potential difference between the grounds of LVS and high voltage side. Thanks to the use of synchronous rectification technology, the efficiency of the proposed BDC is increased. The operating principles, the characteristics analysis and the parameter design of the proposed BDC are given. In addition, to show the merits of the proposed BDC, a comparison study involves the proposed converter and other BDCs is demonstrated. Finally, some experimental results obtained using a 1000 W prototype are presented to valid the effectiveness of the proposed BDC. 96.43% and 96.67% maximum conversion efficiencies can be achieved in the step-up and step-down modes, respectively.

Research on fault clearing scheme for half-bridge modular multilevel converters high voltage DC based on overhead transmission lines

Abstract When a short-circuit fault occurs on the transmission lines of high voltage DC transmission system based on modular multilevel converters, the fault cannot be cleared by adjusting the converter control system, which results in longer recovery time. Aiming at the problem above, a fault self-clearing scheme based on the fault clearing module for the half-bridge converter station is proposed. Combined with the actual operating status of the flexible DC transmission project, centralized parameter models are utilized to analyze the fault self-clearing mechanism. Besides, the impact of the discharge branch on the fault clearing effect is studied in depth to provide a design consideration for the fault clearing module and improve the comprehensive benefits of the proposed scheme. PSCAD/EMTDC simulation results show that the introduction of the fault clearing module in the half-bridge converter station can effectively suppress the fault short-circuit current and shorten the fault clearing time. In addition, circuit breakers on both sides of the line do not need to be tripped, providing a reliable guarantee for the subsequent adaptive restart process.

Fault steady-state analysis method for the AC system with LCC-HVDC infeed

Fault steady-state analysis method can help to analyze the variation law of electrical quantities, clarify the fault characteristics, and provide the basis of power system design, protection scheme formulation, short-circuit current limitation and electrical equipment selection. Existing methods of fault steady-state analysis for alternating current (AC) system with line-commutated converter (LCC) high voltage direct current (HVDC) infeed are not suitable for high-severity AC system faults and existing equivalent models of LCC-HVDC system are inaccurate under asymmetrical AC system fault. Hence, a more accurate method is proposed in this paper. First, according to the relationship between the injected current of LCC-HVDC system and the fault phase voltage of commutation bus, equivalent models of the LCC-HVDC system under symmetrical fault and asymmetrical fault of AC system are established respectively. Based on the equivalent models of LCC-HVDC system and the fault sequence network of AC system, a fault steady-state analysis method for AC system with LCC-HVDC infeed is proposed. The proposed method is validated on CIGRE Benchmark HVDC model using PSCAD/EMTDC software. The results show that the proposed method is accurate and suitable for faults of different severities in AC system with LCC-HVDC infeed.

Research on the dynamic characteristics of electric field distribution of the ± 1100 kV Ultra high voltage converter transformer valve‐side bushing using weakly ionised gas conductance model

Research on the dynamic characteristics of electric field distribution of the ± 1100 kV Ultra high voltage converter transformer valve‐side bushing using weakly ionised gas conductance model

A Multiport Modular DC–DC Converter With Low-Loss Series LC Power Balancing Unit for MVDC Interface of Distributed Photovoltaics

An input-independent and output-series modular dc-dc converter with multiple input ports and high voltage conversion ratio can apply well to medium-voltage dc interface of distributed photovoltaics (PV). However, PV power mismatch will result in output voltage imbalance of the submodules (SMs), which is contrary to the standardized multimodule design. In this article, a multiport modular dc-dc converter with low-loss series LC power balancing unit (PBU) is proposed to address this problem. An isolated dc-dc converter is employed as the SM, which consists of full-bridge (FB) circuit on the PV side and half-bridge (HB) circuit on the grid side. Independent maximum power point tracking can be realized by controlling the phase shift between the FB and the HB, while voltage balancing (or power balancing) of SMs can be achieved by regulating the phase shift between adjacent HBs. Only one inductor and one capacitor are used in the PBU and all the switches of SM turn on with zero-voltage switching, which contributes to the low-cost and low-loss characteristic of the converter. Simulations and experiments are carried out to verify the validity of the theory.

Interleaved non‐isolated DC–DC converter for ultra‐high step‐up applications

This study presents a novel interleaved non-isolated converter for ultra-high step-up applications. This circuit utilises coupled inductor and voltage-lift techniques to achieve high voltage gain. In the proposed converter, the configuration of interleaved technique and winding-cross-coupled inductors not only reduces the input current ripple and current stress of semiconductor devices but also increases the voltage gain. Further, using voltage-lift technique helps to reach a very high voltage conversion ratio with low turn ratio and proper duty cycle. Since the voltage stress of semiconductor devices is low enough, low on resistance switches and low voltage ultra-fast recovery diodes are used. For this converter, high voltage gain, low conduction losses, low reverse recovery losses, high efficiency, low input current ripple, small volume and reduced cost are provided. Therefore, the proposed converter is a good choice for ultra-high step-up applications. The implemented 100 W laboratory prototype circuit with 18 V input voltage and unity turn ratio of coupled inductors reaches 360 V output voltage and 94.7% efficiency which validates the accuracy of theoretical analysis.

Battery Charger with Improved Power Quality Cuk Derived Power Factor Correction Converter

In this paper, a single switch single stage switched inductor based cuk converter with power factor correction control techniques is proposed. The main features of the proposed converter is low current stress, high voltage conversion ratio, reduction of components, high efficiency, low THD, etc., The operation of the proposed converter is explained in several modes along with the design of the converter. The performance of the proposed converter with different loads such as resistive, battery and motor loads with CC and CV control is analyzed and various factors such as power factor, efficiency and THD are compared. The Simulation work is carried out in MATLAB/Simulink software.

Design, fabrication, and characterization of the modular integrated exploding foil initiator system based on low temperature co-fired ceramic technology

In this study, the flyback high-voltage conversion unit, capacitor discharge unit, and EFI chip of the exploding foil initiator (EFI) system were highly integrated using low temperature cofired ceramic technology and MEMS, forming a modular integrated system with boost, discharge, and firing functions. The modular integrated EFI system used the design idea of system in a package, selected chip-level or planar components, eliminating the need for connecting wires and reducing the volume of the EFI system to 5.67 cm3. Compared with the traditional EFI system, while analysis from the characterization showed that the integrated structure reduced the loop inductance of the system to 27 nH, which was 55 % lesser, it accelerated the flyer to 3800 m/s, which was 15.2 % faster. These accomplishments indicated that the energy utilization rate of the integrated system was higher. The input voltage of the system was reduced from traditionally high voltage of 1250 V to lower voltage of 24 V due to the integrated-system boost function. Simultaneously, the 5 V MOS controlled thyristor (MCT) chip was selected to replace 1800 V∼2500 V spark gap switch as the working voltage, thus making 5 V the switching voltage of the system. These changes made high safety operation of the system. Moreover, the system had used modular design and manufacturing to improve its reliability and obtained the characteristics of mass production.

Hybrid cascaded high step‐up DC/DC converter with continuous input current for renewable energy applications

This study proposes a new structure of hybrid cascade coupled-inductor high step-up (HCCIHSU) DC/DC converter for renewable energy sources. The proposed topology can provide an ultra-high voltage gain under continuous input current and low voltage stress on semiconductor devices. This converter is a hybrid cascade connection of the boost and buck–boost converters. The HCCIHSU utilises a coupled-inductor (CI) and a voltage multiplier (VM) cell to enhance the voltage gain ratio as a semi-quadratic function. The magnetic energy of the leakage inductor of the CI is recycled to the VM capacitors that reduce the component voltage stress and improve the converter voltage gain. Additionally, the voltage stress on the main power switch is clamped by two passive clamp capacitors. Due to the very high voltage conversion ratio at a reduced turn's ratio, the maximum voltage stresses on the switches and diodes are significantly alleviated, which further improve the efficiency. In this study, detailed steady-state analysis and comparisons with other related converters are provided. Finally, a 160 W/200 V laboratory prototype is built with 24 V input voltage at a switching frequency of 50 kHz to verify the performance of the proposed converter.