Nine-switch Converter Research Articles

Performance analysis of PID and SMC for PEMFC-based grid integrated system using nine switch converter - A comparative study

Hydrogen fuel cells are gaining popularity as a reliable and efficient sustainable energy source. They have found uses in electric vehicles and microgrid applications. A grid-connected microgrid system with a 60 kW proton exchange membrane fuel cell (PEMFC) is proposed. A PEM fuel cell-based generating unit is studied, using a sliding mode controller (SMC) in the control scheme and a nine-switch converter (NSC) for the system integration. The NSC is used to integrate the FC system with the utility grid and controls the system's power flow. This study is focused on the performance evaluation of the proportional-integral-derivative (PID) and SMC controllers. The controllers' gains are tuned using an improved arithmetic optimization method (IAOA). The article also emphasizes improving system performance and stability by incorporating SMC in the control scheme. The suggested system is exposed to different source and load-side disturbances for performance evaluation. Matlab/Simulink is used to model the proposed system and validated by the real-time OPAL-RT 4510.

Nine-Switch Multiport Converter Applied to Battery-Powered Tramway with Reduced Leakage Current

Electrically powered rail transport is constantly increasing in order to meet the high demand for people and cargo transportation, whether with high-speed trains, subways, suburban trains, or electric tramways. In these types of applications, power electronics solutions such as integrated and efficient converters with multiple functionalities are highly desirable. Among these converters, one family stands out for its ability to generating multiple output terminals with reduced number of switches, namely, the nine-switch converter. Therefore, this paper proposes a multiport converter solution based on the nine-switch converter topology that integrates multiple functionalities with a reduced switch count. The converter, responsible for the power drive of the electric tramway, is exclusively powered by a battery. Moreover, it presents a strategically connected passive filter that provides a low-impedance path for high-frequency currents, avoiding leakage of the current circulation in the induction motor. Its phase-shift pulse-width modulation is capable of reducing the high-frequency components of the current delivered by the battery. The energy storage system is designed to optimize the system capacity based on the known real load profile of a public tramway, with a maximum power of 532.1 kW. The control system is designed and applied considering the battery as the energy source. Simulations were performed in the Matlab/Simulink environment to validate the proposed system, along with experiments using a reduced-scale prototype controlled by the dSPACE platform. The results present the converter’s proper operation with integration of the source and AC load, presenting improved features compared with conventional solutions in terms of reduced leakage of the current circulation from the AC load and reduced battery current ripple.

Real-Time Validation of Two-Generator-Based Isolated Hybrid Microgrid System Using a Nine-Switch Converter

Real-Time Validation of Two-Generator-Based Isolated Hybrid Microgrid System Using a Nine-Switch Converter

Evaluation of super-twisting SMC and NSC combination for power control in multi-source renewable power generation system

This work is based on the evaluation of a super-twisting sliding mode controller for power control in an isolated multi-source renewable generation system. The hybrid multi-source system taken into consideration, in this case, is made up of three different generation units. The main generation unit is a 22kW micro-hydro system with a self-excited induction generator. To this, a 7.5kW doubly fed induction generator-based wind energy conversion system is integrated. An 18kW solar PV system connected to a battery energy storage system is connected at the dc-link. All the above systems are integrated through a bidirectional nine-switch converter. The autonomous hybrid system's power control is solely done by the nine-switch converter. In this work, efforts have been made to combine the robustness and accuracy of super-twisting sliding mode controllers with the reliability and flexibility of the nine-switch converters. The performance evaluation of the above combination is done with various load and source side disturbances. The system's uninterrupted power supply capability has also been examined in this work. Using the MATLAB environment, the system's performance is evaluated, examined, and the same has been verified using an OPAL-RT 4510 real-time simulator.

Research on Optimization SVPWM Method of Nine-switch Inverter for Bearingless Motor Based on Reducing Switching Times

The traditional bearingless motor system controlled by two three-phase inverters has a high cost and volume. In this paper, the nine-switch converter is applied to the bearingless motor control system, which can control the torque winding and suspension winding of the bearingless motor at the same time to save three MOSFETs. This paper proposes a nine-switch inverter SVPWM method to reduce switching loss. This method is no longer limited to only considering the action sequence of voltage vectors but reduces the switching number from selecting voltage vectors. The optimal nine-switch inverter basic voltage vector selection principle is determined by comparing the switching times of each sector combination with different voltage vector combinations. Finally, the simulation results verify the effectiveness of this method.

A Novel Multiport Hybrid Wave Energy System for Grid-Connected and Off-Grid Applications

Direct drive wave energy converters (DDWECs) have gradually become the mainstream of wave energy converters (WECs). In order to make better use of wave energy, energy storage devices and other renewable energy sources are often used to suppress power fluctuation in DDWECs. However, the addition of other energy sources will increase the complexity of the converter system and the number of power switches. Considering the flexibility of nine-switch converters (NSCs), this paper proposes a novel nine-switch grid-connected/off-grid multiport hybrid wave energy system (HWES). First, the system structure and modulation principle are described. Then, a model for a generator, a grid and energy storage are built, including a control strategy of each part. Finally, a simulation for the grid-connected/off-grid application and an experiment on the off-grid HWES are carried out. The results show that the multiport wave energy system can achieve the objective of stable and reliable power transmission by reducing power devices.

Effectiveness of B2BC-based SGSC–PGSC and NSC-based SGSC–PGSC in a DFIG-based Grid-connected WT System – A Comparative Study

ABSTRACT This paper presents the doubly fed induction generator (DFIG)-based wind turbine (WT) system with a back-to-back converter (B2BC) and nine-switch converter (NSC) as well as their control schemes. A new slip speed estimator-based control method is also proposed to control RSC of the DFIG-WT system. The system responses are obtained using two different converter topologies, namely (i) B2BC and (ii) NSC-based series grid-side converter (SGSC)–parallel grid-side converter (PGSC) under unbalanced/balanced grid disturbances due to balanced/unbalanced non-linear loads. Their responses are also compared to study the effectiveness of both the converter topologies. Moreover, the system responses are also obtained with the proposed slip speed estimator-based control scheme under varying wind velocity and compared with that of obtained using one of the existing control schemes. The system is modeled in MATLAB/Simulink platform. The time-domain simulation results are presented and analyzed in details. Results show that the B2BC- used with DFIG-WT system can be replaced by NSC under any loading condition and also the proposed slip speed estimator can offer good performance under varying wind velocity.

Current Source Converter as an Effective Interface to Interconnect Microgrid and Main Grid

Back-to-back current source converters play an important role in high power applications. However, this back-to-back converter system uses a larger number of power switches, which is associated with more cost and the power density of the converter system can be affected. To address this issue, in this paper, a novel nine-switch back-to-back current source converter is proposed. To realize proper modulation of this nine-switch converter system, the concept of ampere balance is revisited at first. Then, its relationship with the traditional modulation scheme is revealed. Moreover, based on the ampere balance, the real-time dwell time calculation method is developed, where the tracking of rectifier current and inverter current is taken into consideration simultaneously. Finally, simulation results verify the effectiveness of the proposed modulation scheme.

Improvement of voltage adaptability for decentralised doubly‐fed induction generator wind power system based on nine‐switch converter

This paper proposes a method to improve the voltage adaptability of doubly fed induction generator (DFIG) wind turbines in a decentralised scenario by incorporating a nine-switch converter (NSC). With the proposed scheme, the DFIG can realise low voltage ride-through (LVRT) and continuous operation under the grid voltage harmonic, drop, and rise. The topology of the NSC-DFIG system is introduced and is used to solve the circuit model. Control strategies for voltage compensation and current compensation are based on the circuit model. The corresponding voltage compensation scheme and the NSC DC voltage control scheme were designed according to the specific capacity configuration of the NSC in this study. To reduce the DC-side voltage of the NSC, a third harmonic-injection modulation method and a dynamic modulation ratio allocation strategy were incorporated. Simulations under four power grid voltage conditions were used to validate the scheme. This method can improve the voltage adaptability for decentralised DFIG wind power systems, which can enable their successful interactions with the power grid.

Decoupled Predictive Current Control With Duty-Cycle Optimization of a Grid-Tied Nine-Switch Converter Applied to an Induction Generator

The nine-switch converter (NSC) was developed aiming at the reduction in the number of power converter switches in multiport systems, such as variable-speed drives for power generation. Among the possible control techniques for the NSC, finite-control-set model-predictive control (FCS-MPC) stands out due to its fast dynamics and easy incorporation of system restrictions. However, converters with many switching possibilities and control goals increase the computational burden and the cost function complexity. Moreover, FCS-MPC can present high ripple values in the system outputs. This article proposes a decoupled predictive current control with duty-cycle optimization (PCC-DD) for the NSC, which decouples the control of an induction generator from the grid control. The separation between grid and generator controls decreases the enumeration of voltage vectors to be performed, reducing computational burden. Then, duty-cycle calculations are responsible for reducing torque and active power ripples. Experimental results show that PCC-DD provides lower ripple factors for the desired variables when compared to the approach with a concentrated cost function. The main contribution is a better steady-state performance with a lower computational burden. Therefore, PCC-DD is a suitable low-ripple technique for NSC control and for application to power generation with variable-speed generators.

Pipelining Strategies and Design Considerations of Predictive Current Control Method

This paper explores the pipelining strategies for the model predictive control methods. The array and vector processing methods are examined to discover their applicability in the model predictive current method. The potential benefits of the pipelining methods are investigated, and their design methodologies are scrutinized. The model predictive control is a nonlinear control technique that predicts the system dynamics. The model predictive control (MPC) provides rapid response to the load variations and guarantees robust operation. However, the lower sampling period is the main design constraint to achieve a reliable system operation. The selection of a low sampling period demands a powerful digital controller due to the increasing computational burden. To handle the high calculation burden, a field-programmable gate array (FPGA) is a powerful solution. A proper pipelining strategy enables the use of the MPC in real-time applications. In this paper, pipelining strategies and practical design considerations of the FPGA-based predictive current method are presented. The nine switch converter (NSC) is selected as an experimental case study. The experimental results are provided to demonstrate the theoretical framework. The experimental results prove the feasibility of the array processing and vector processing methods in MPC applications.

Implementation of Nine-Switch converter to PV solar array operating with different loads

Solar energy is a non-depleting source of energy where one hour of solar energy reaching on earth’s surface is enough to meet the world’s demand for a year. In present scenario people need electric power every single minute. Solar energy can be easily generated using photovoltaic panels for any type of purposes i.e., domestic or industrial. It is also very efficient and clean energy system. A lot of researches are going on solar energy to make it more efficient so that maximum energy can be drawn from sunlight. Conversion of solar energy to electrical energy includes a number of converters according to its use. One major issue related to a converter is with respect to switching losses, on state losses and sometimes complex gate circuits. Primarily from few years a lot of emphasis is given to reduce the number of switches in a converter circuit. Nine Switch Converters are a major leap in the world-changing scenario towards the converters that are being employed to the various systems, due to its various advantages which include fewer switching devices than usual, less switching losses and high-power quality. In this paper, a Photovoltaic solar array is used as a source along with a Nine-Switch converter to power a separate three-phase load. The voltage generated by the Photovoltaic solar array is regulated using a dc-dc boost converter whose output is supplied to the input of the nine-switch converter that will ultimately power the loads. The gating signals for the nine-switch converter employs the space vector modulation technique, as space vector modulation has a number of advantages when compared to other modulation techniques which includes less harmonics, higher modulation index etc. A MATLAB simulation is included to show the performance of the system.

Model predictive control of nine-switch converter with output filter for independent control of two loads

This paper proposes a model predictive control (MPC) algorithm designed for nine-switch converter with output filter (NSCOF) to control two three-phase AC loads independently. A state function of each leg of nine-switch converter (NSC) is established to characterize the internal conditions of the NSC because the traditional model of the NSCOF does not involve the interior model of the NSC. Based on the NSCOF model with the state function of each leg, a prediction model of NSCOF is constructed. The two AC terminals of NSCOF are treated as one module when the MPC is designed. The proposed MPC achieves controlling two three-phase AC loads working under different frequency modes. Furthermore, this algorithm is independent of the modulation method for reducing the difficulty of the controller design and its limits. The simulation and experimental results reveal that the steady-state and dynamic response performance of NSCOF are substantially improved using MPC.

Modelling and Control of Nine-Switch Converter-Based DFIG Wind Power System

In this paper, nine-switch converter (NSC) is used to replace the Back-to-Back converter of DFIG wind power system. In order to simplify the control process and improve the performance, the switching function model of nine-switch converter under ABC coordinate system is established, and the mapping relationship between the parameters of NSC’s loads and those of DFIG wind energy conversion system is given. Meanwhile, a Resonant-proportional-integral (Resonant-PI) control strategy for NSC-based DFIG wind energy conversion system is proposed, and the PI controller is used for static control under steady state and the resonant controller for suppressing harmonic content in this method. The proposed method performs better than PI control in harmonic content and dynamic response. The simulations and experimental results verify the validity and reliability of the proposed mathematical model and control algorithm.

Research on simplified SVPWM strategy for nine-switch converter

Nine-switch converter has promising application prospects in fields where cost, volume and power density are required. The performance of the converter depends to a large extent on the modulation strategy. The existing SVPWM strategy for nine-switch converter requires a lengthy zero-vectors table to make over-modulation judgment, which increased the complexity of the algorithm and the runtime of the program. To improve performance, a novel simplified SVPWM strategy for nine-switch converter is proposed in this paper. The zero-vectors table is replaced by a set of simple formulas for over-modulation judgment and processing. This simplification is based on derivation of the implied reference signals of the SVPWM strategy. The correctness of the proposed algorithm is verified through simulation and experimental results. It is also demonstrated that the proposed simplified algorithm can achieve the same output results as the traditional method with less code length and runtime.

Modulation Method for Nine-Switch Converter Based on Equivalent Mechanism Between Nine-Switch Converter and Dual Six-Switch Converters

In this article, the equivalent mechanism between nine-switch converter (NSC) and the two six-switch converters (SSCs) is explained in detail. In order to achieve the decoupling of the upper and lower ac terminals, the concept of virtual leg is proposed and the decoupling model of NSC is established based on virtual legs. In this model, the NSC is equivalent to dual constrained SSCs. Continually, the space vector modulation method of NSC is proposed based on dual constrained SSCs modulation for both common frequency and different frequency modes. In the proposed modulation method, the concept of space vector distance function (SVDF) is proposed. SVDF represents the actual switching times between any two actual working states of NSC. The closer distance between the two actual states is, the smaller the actual switching loss will be. Using the modulation method, the NSC can realize the independent control of two sets of three-phase ac voltage and achieve the same control performance as the dual SSCs. The validity of the proposed converter is verified through simulations and experiments.

Modeling of Nine-Switch-Converter Based on Virtual Leg and Its Application in DFIG Wind Generation System

This article proposes a doubly fed induction generator (DFIG) wind energy conversion system (WECS) based on nine-switch converter. In this article, a new concept of virtual-leg is proposed, and the equivalent mechanism between the nine-switch converter and the dual six-switch converter is first proposed. Furthermore, a mathematical model of the nine-switch converter based on the unipolar binary logic switching function is established. In order to simplify the mathematical model of the nine-switch-converter-based DFIG-WECS, the parameter mapping relationship between the nine-switch converter with loads and the nine-switch-converter-based DFIG-WECS under dq coordinate system is given. Meanwhile, the adaptive resonant proportional integral (PI) (AR-PI) current controller based on the resonant controller, the PI controller, and the adaptive genetic algorithm is applied for the DFIG wind generation system. As a result, harmonic current content, overshoot, and dynamic response speed of the nine-switch-converter-based DFIG-WECS have been significantly improved. Finally, the simulations and experimental results verify the validity and reliability of the proposed mathematical model and control algorithm.

Grid connected DFIG based wind energy conversion system using nine switch converter

In this paper, an attempt is made to develop a speed sensor DFIG-based grid-connected Wind Turbine (WT) system with Nine switch converter (NSC) instead of Back-to-back converter (B2BC). The NSC the merits of reduced number of switching devices and cost, more efficient and reduced installation area over B2BC. a new control scheme, with the use of rotor speed sensors from generator, is proposed for NSC to track the maximum power point (MPP) by controlling the active power flow between rotor and grid under varying wind velocity at unity power factor (UPF). Furthermore, 120 o discontiunuous modulation scheme is also incorporated with proposed control scheme to minimize switching losses of the system. The complete study system has been simulated in MATLAB/simulink platform and all the simulation selults are analyzed in details to study the performance of the system. Simulation results ilustrate that the NSC based WT system and its proposed control scheme can work at its optimum power level for an extensive range of wind velocity and also competent to achieve independent control on flow of both active and reactive powers.

Single-phase transformerless power conditioner based on a two-leg of a nine-switch converter

An interesting solution for problems associated with system voltage, such as sags and swells, as well as those associated with current such as low power factor and harmonic distortion is the unified power quality conditioner. However, one of its drawbacks is the high number of semiconductor devices since its conventional topology presents two full-bridge converters in a back-to-back configuration. Although the six-switch two-leg converter has a feature of presenting two sets of single-phase output terminals, the same as two full-bridge converters, but with a reduced number of switches (six, instead of eight), it has never been used in single-phase power conditioning systems. Therefore, the aim of this paper is to propose a single-phase transformerless power conditioner based on the six-switch two-leg converter. In this solution, there are two sets of single-phase outputs, each set behaving as an independent converter. The top unit of the converter is connected in parallel to the load by means of a series LC filter tuned to a specific frequency, working as a hybrid power filter and being responsible for the dc-link voltage regulation and the compensation of current harmonics generated by the non-linear load. The bottom unit works as a dynamic voltage restorer and it is responsible for compensating harmonics, sags or swells in the grid voltage, in such way that the load receives a sinusoidal voltage waveform. The challenges of the single-phase transformerless power conditioner that is proposed in this paper are different of the three-phase systems based on nine-switch converter previously proposed in literature. Dealing with the circulating current makes mathematical model and the modulation strategy completely different and, therefore, all equations have been developed for this specific single-phase power conditioner application. The proposed power conditioner presents four main advantages when compared with other configurations available in literature: (a) it is a transformerless solution; (b) it has a reduced number of switches; (c) it has a reduced dc-link voltage and rated power because of its hybrid power filter characteristics; (d) it does not have to handle with dc-link voltage unbalance. Experimental results demonstrate the validity and the effectiveness of the proposed topology.

Improvement of ZVS Range and Current Quality of the Nine-Switch Single-Stage AC–DC Converter

The nine-switch single-stage three-phase ac-dc isolated converter integrates a three-phase active front-end ac-dc converter and a three-phase high-frequency galvanically isolated dc-dc converter in one stage, leading to a device count reduction of 25% compared to an equivalent two-stage configuration. The advantage of the nine-switch converter can be truly realized if it can achieve similar efficiency and input current quality as a two-stage converter. In this article, a design methodology is proposed, which ensures zero-voltage switching of the bottom and the middle switches of the nine-switch converter for the entire line cycle and also reduces its input current total harmonic distortion below 5%. By implementing space vector pulsewidth modulation, the dc-link voltage of the nine-switch converter is reduced to the level of an equivalent two-stage converter. The analytical claims are verified with a 3-kW laboratory prototype operating at 400-V ac input, 800-V dc-link voltage, and 380-V isolated dc output voltage.