Current source converter on-line pattern generator switching frequency minimization

2002 ◽  
Author(s):  
J.R. Espinoza ◽  
G. Joos
Keyword(s):  
Current Source ◽  
Pattern Generator ◽  
Switching Frequency ◽  
Line Pattern ◽  
Current Source Converter ◽  
On Line

scholarly journals Current source converters for megawatt wind energy conversion systems

2021 ◽  
Author(s):  
Jingya Dai
Keyword(s):  
Wind Energy ◽  
Reactive Power ◽  
Controller Design ◽  
Low Voltage ◽  
Dynamic Performance ◽  
Current Source ◽  
Current Control ◽  
Switching Frequency ◽  
Current Source Converter ◽  
Energy Conversion Systems

The rapid growth of wind energy market has propelled the research and development of high-power wind turbines in the megawatt range. At this power level, current source converter (CSC) topologies possess favorable features such as simple structure, grid friendly waveforms, controllable power factor, and reliable grid short-circuit protection. This dissertation proposes the use of current source converters for permanent magnet synchronous generator based megawatt wind energy conversion systems (WECS). Related research in terms of converter topology, modulation scheme, control strategy and grid integration are carried out to adapt the proposed configuration for megawatt wind applications. Various current source converter topologies are compared for wind applications. Detailed feasibility study and performance evaluation are conducted based on theoretical analysis and simulation results. Among all, the back-to-back pulse-width modulated (PWM) current source converter is identified as the most promising converter configuration for megawatt WECS due to its high performance, control flexibility and compliance with grid connection codes. A novel multi-sampling space vector modulation (MS-SVM) scheme with superior harmonic performance and controllability is proposed to operate the PWM CSC. The device switching frequency under MS-SVM is investigated and methods to eliminate additional switching are presented. The proposed scheme is compared with the conventional modulation schemes. It is demonstrated that the MS-SVM scheme provides superior performance at low switching frequency. It not only offers high control flexibility but also substantially reduces the low-order harmonics existing in the conventional schemes. System modeling and controller design for the current source converter based WECS are then presented. Dynamic, steady-state and small-signal models are developed for analysis and controller design. An optimum de-link current control scheme is developed to achieve the best dynamic performance and maximize the system overall efficiency. Control strategies such as decoupled active and reactive power control and power feed-forward control are also proposed to further improve the system dynamic performance. Grid integration issues, especially the low-voltage ride-through capability of the current source converter based WECS, are addressed. Challenges for the grid-connected current source converter are identified based on grid code requirements. A unified de-link current control scheme is proposed to assist the system to ride through grid low-voltage faults while maintaining the control capability of active and reactive power during and after the fault. The unified de-link controller can be well embedded in the system control structure. Smooth transitions between normal and fault operations are achieved. Simulation and experimental verifications for various objectives are provided throughout the dissertation. The results validate the proposed solutions for the main challenges of using current source converter in a megawatt WECS.

scholarly journals Five-level parallel current source converter for high power drives with DC current balance control and superior harmonic performance

2021 ◽  
Author(s):  
Navid Binesh
Keyword(s):  
High Power ◽  
Balance Control ◽  
Dynamic Performance ◽  
Current Source ◽  
Modulation Scheme ◽  
Switching Frequency ◽  
Switching Loss ◽  
Switching Sequence ◽  
Current Source Converter ◽  
Parallel Current

In this thesis, space vector modulation is developed for a 5-level parallel current source converter for high power drives. The modulation scheme is designed to bring superior harmonic performance to the currents on the AC sides. This method synthesizes the rotating reference current vector in the converter's space vector's plane with three adjacent switching vectors. Unbalanced currents of DC links become a practical challenge when two converters are connected in parallel. To balance the DC currents, the proper switching state for every Small and Medium switching vector is chosen from redundant switching states corresponding to the vector based on circuit circumstances and the designed switching sequence. Simulated results verify the effectiveness of the method. In addition, the switching sequence is designed to lower the switching frequency and minimize the switching loss. Finally, the proposed converter and switching scheme are simulated and steady state and dynamic performance are investigated in detail.

scholarly journals Current source converters for megawatt wind energy conversion systems

2021 ◽  
Author(s):  
Jingya Dai
Keyword(s):  
Wind Energy ◽  
Reactive Power ◽  
Controller Design ◽  
Low Voltage ◽  
Dynamic Performance ◽  
Current Source ◽  
Current Control ◽  
Switching Frequency ◽  
Current Source Converter ◽  
Energy Conversion Systems

The rapid growth of wind energy market has propelled the research and development of high-power wind turbines in the megawatt range. At this power level, current source converter (CSC) topologies possess favorable features such as simple structure, grid friendly waveforms, controllable power factor, and reliable grid short-circuit protection. This dissertation proposes the use of current source converters for permanent magnet synchronous generator based megawatt wind energy conversion systems (WECS). Related research in terms of converter topology, modulation scheme, control strategy and grid integration are carried out to adapt the proposed configuration for megawatt wind applications. Various current source converter topologies are compared for wind applications. Detailed feasibility study and performance evaluation are conducted based on theoretical analysis and simulation results. Among all, the back-to-back pulse-width modulated (PWM) current source converter is identified as the most promising converter configuration for megawatt WECS due to its high performance, control flexibility and compliance with grid connection codes. A novel multi-sampling space vector modulation (MS-SVM) scheme with superior harmonic performance and controllability is proposed to operate the PWM CSC. The device switching frequency under MS-SVM is investigated and methods to eliminate additional switching are presented. The proposed scheme is compared with the conventional modulation schemes. It is demonstrated that the MS-SVM scheme provides superior performance at low switching frequency. It not only offers high control flexibility but also substantially reduces the low-order harmonics existing in the conventional schemes. System modeling and controller design for the current source converter based WECS are then presented. Dynamic, steady-state and small-signal models are developed for analysis and controller design. An optimum de-link current control scheme is developed to achieve the best dynamic performance and maximize the system overall efficiency. Control strategies such as decoupled active and reactive power control and power feed-forward control are also proposed to further improve the system dynamic performance. Grid integration issues, especially the low-voltage ride-through capability of the current source converter based WECS, are addressed. Challenges for the grid-connected current source converter are identified based on grid code requirements. A unified de-link current control scheme is proposed to assist the system to ride through grid low-voltage faults while maintaining the control capability of active and reactive power during and after the fault. The unified de-link controller can be well embedded in the system control structure. Smooth transitions between normal and fault operations are achieved. Simulation and experimental verifications for various objectives are provided throughout the dissertation. The results validate the proposed solutions for the main challenges of using current source converter in a megawatt WECS.

scholarly journals Sensorless Current Source-Fed PM Drive System For Low Speed Operations

2021 ◽  
Author(s):  
Ehsan Al-Nabi
Keyword(s):  
Permanent Magnet ◽  
High Power ◽  
Permanent Magnet Synchronous Motor ◽  
Current Source ◽  
Drive System ◽  
Switching Frequency ◽  
Low Speed ◽  
Pulse Width Modulated ◽  
Medium Voltage ◽  
Current Source Converter

In this thesis, a sensorless method for low and zero speed operation is proposed for a high-power medium-voltage pulse-width-modulated Current–Source-Converter (CSC)-fed Interior Permanent Magnet Motor (IPM) drive system. The proposed method is based on injection of a high-frequency (HF) pulsating sinusoidal signal into the estimated synchronous reference frame of the drive’s Field Oriented Control (FOC) scheme. The conventional FOC control scheme, low switching frequency, dc-link inductor and the inverter output three-phase filter capacitor of the medium-voltage high-power current-source drive present some challenges in the generation and design of the HF injection signal. To overcome the challenges, the FOC scheme is modified by introducing a modulation index control with a suitable dc-link current compensation to enhance the dynamic response of the injected signal and prevent any clamp in the injected signal. In addition, a Multisampling Space Vector Modulation (MS-SVM) method is proposed to prevent the distortion in the HF signal due to a low switching frequency to injected signal ratio. It is found that by using the proposed FOC scheme and multisampling modulation scheme, and proper design of the HF signal, an accurate rotor flux angle can be estimated for sensorless zero/low speed operation. Moreover, a novel input power factor compensation method is proposed for a high-power pulse-width-modulated Current-Source-Converter (CSC)-fed Permanent Magnet Synchronous Motor (PMSM) drive system. The proposed method is based on controlling the d-axis stator current component in the field-oriented control scheme of the drive system. The main feature of the proposed scheme is to compensate for the line-side power factor without the need for modulation index control in either the rectifier or the inverter. Simulation and experimental verification for various objectives are provided throughout the thesis. The results validate the proposed solutions for the main challenges of zero/low speed operation of sensorless Current-Source-Converter (CSC)-fed Permanent Magnet Synchronous Motor (PMSM) drive system.

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