并网型光伏发电系统的建模与故障穿越控制策略研究
发布时间：2020-10-19 06:24
随着化石燃料的日益枯竭和全球能源需求的持续增加,环境问题变得日益严峻。由于光伏组件及其系统的技术进步和政府对清洁能源的激励,光伏发电系统的成本逐年下降。在过去几十年中,光伏的累计装机容量在全球范围内以极高的速度增长。光伏发电系统的大规模并网给电力系统的稳定和安全运行带来了重大冲击。因此,光伏发电系统接入电网需要一种有效的控制策略,该策略应能确保系统在电网正常和故障条件下均能良好运行,并满足可再生能源可靠和安全并网规范要求。本文针对电网正常和故障运行两种情况,研究和提出了两级光伏发电系统的建模与控制方法。针对电网正常运行情况,设计了用于调节两级并网光伏发电系统的多层控制结构,以满足电网规范要求并能有效地促进光伏发电系统的集成。设计的控制方案具有最大功率跟踪功能,该功能由升压DC-DC变换器对电流进行调节来实现,能根据电能质量需求调节注入电网的电流。通过控制并网逆变器实现所需的电能质量,其中电流控制通过dq坐标系下的PI控制器来完成。针对网侧对称故障情况,建立了完整的双级光伏发电系统低电压穿越模型,满足电压跌落期间提供无功电流的电网规范要求。提出的模型通过更新电流发生器的参考值及相应的控制器,有效地实现低电压穿越和改善电能质量及并网稳定性。提出的控制方案有助于满足电网规范要求,并确保光伏发电系统在电网发生对称故障时能够平稳运行。针对网侧不对称故障情况,提出了两级光伏发电系统的低电压穿越控制策略。提出的策略包括适应电网规范要求的功率参考值计算、有功和无功功率控制,以及实现低电压穿越的灵活电能质量控制和峰值电流限幅控制。该控制策略通过dq坐标系下的电流参考值发生器,实现低电压穿越过程中电能质量的灵活控制,并具有峰值电流限制能力,以避免逆变器过电流。所设计的电流参考值发生器,能够实现光伏发电系统在各种电网故障下均能可靠运行。而且,提出了用于有效降低PV功率的故障穿越方案,采用光伏阵列功率削减策略来避免DC电压增加,以防止故障期间出现直流过电压。首先,将减少的光伏阵列功率注入电网,如果由于网侧电压跌落过大或持续时间过长而使直流电压持续增加的话,则直流斩波器将被激活,以防止直流母线电压超过其允许极限。此外,所提出的控制策略还包括:用于电网电压幅值计算和故障检测的混合电网同步和序列分离方法。通过现场测试和模拟仿真验证了提出的建模和控制策略的有效性。最后,研究了光伏发电系统接入对弱电网电压稳定性的影响,主要包括光伏电站不同控制策略对光伏系统输出特性及并网点电压的影响。建立了简化的光伏电站动态模型,在不同的负荷模型和电网强度下,对比分析了各种控制策略对并网点电压恢复特性的影响。提出了一种改进的有功电流恢复方法,实现光伏发电功率和并网点电压的有效恢复。采用MATLAB/SIMULINK仿真验证了提出的光伏系统控制策略的有效性。
【学位单位】：哈尔滨工业大学
【学位级别】：博士
【学位年份】：2019
【中图分类】：TM615
【文章目录】：
摘要
Abstract
Chapter 1 Introduction
1.1 Background and significance of study
1.2 Objective of the thesis and main contributions
1.3 Review of related research
1.4 Outlines of the thesis
Chapter 2 Fundamentals of Grid-Connected PV Systems and TheirControls
2.1 Introduction
2.2 Structure and topologies
2.2.1 Connection topologies of PV systems
2.2.2 Power conditioning unit
2.3 Description of grid-connected PV System and component modeling
2.3.1 Description of PV system structure
2.3.2 Modelling of PV system components
2.4 Mathematical model of a grid-connected PV system in dq frame
2.4.1 Park’s transformation (or dq transformation)
2.4.2 Mathematical model of a PV system in dq frame
2.4.3 Grid synchronization
2.5 PV system control under normal operation
2.5.1 DC-DC converter control and MPPT
2.5.2 Three-layer control scheme
2.6 Simulation results
2.7 Summary
Chapter 3 Control of PV Systems under Balanced Grid Faults
3.1 Introduction
3.2 Standards and requirements for PV grid integration
3.2.1 Grid codes
3.2.2 Stationary grid support
3.2.3 Voltage support during grid disturbance
3.3 Control strategies under balanced grid faults
3.3.1 Boost DC‐DC converter control
3.3.2 Two-layer inverter control scheme
3.4 Simulation results
3.5 Summary
Chapter 4 Control of PV Systems under Unbalanced Grid Faults
4.1 Introduction
4.2 Control strategy under unbalanced grid faults
4.2.1 Framework of the proposed control strategy
4.2.2 Fault detection and grid voltage synchronization
4.2.3 Power references calculation
4.2.4 Power reduction strategy for DC-link voltage control
4.2.5 Proposed current reference generators
4.3 Inverter controller implementations
4.3.1 Inner control loop: current controller design
4.3.2 Outer control loops
4.3.3 Inverter current limitation
4.4 Simulation results
4.5 Summary
Chapter 5 Impacts of PV Integration on Voltage Stability of Weak Grids
5.1 Introduction
5.2 Definition and measure of grid strength
5.2.1 Definition of grid strength
5.2.2 Measurement of grid strength
5.3 Overview of voltage stability analysis
5.3.1 Definition of voltage stability
5.3.2 Classification of voltage stability
5.4 Test system and its modeling
5.4.1 Test system
5.4.2 Simplified PV system model
5.4.3 Load modeling
5.5 Impacts of FRT strategies of PV systems on voltage stability of weak grids
5.5.1 Existing FRT control strategies
5.5.2 Proposed FRT control strategy
5.5.3 Case studies for analysis of voltage stability
5.6 Summary
Conclusions and Future Work
Conclusions
Future work
References
Publication During the Doctoral Study
Acknowledgement
Cirriculum Vitae (CV)
本文编号：2846842
【学位单位】：哈尔滨工业大学
【学位级别】：博士
【学位年份】：2019
【中图分类】：TM615
【文章目录】：
摘要
Abstract
Chapter 1 Introduction
1.1 Background and significance of study
1.2 Objective of the thesis and main contributions
1.3 Review of related research
1.4 Outlines of the thesis
Chapter 2 Fundamentals of Grid-Connected PV Systems and TheirControls
2.1 Introduction
2.2 Structure and topologies
2.2.1 Connection topologies of PV systems
2.2.2 Power conditioning unit
2.3 Description of grid-connected PV System and component modeling
2.3.1 Description of PV system structure
2.3.2 Modelling of PV system components
2.4 Mathematical model of a grid-connected PV system in dq frame
2.4.1 Park’s transformation (or dq transformation)
2.4.2 Mathematical model of a PV system in dq frame
2.4.3 Grid synchronization
2.5 PV system control under normal operation
2.5.1 DC-DC converter control and MPPT
2.5.2 Three-layer control scheme
2.6 Simulation results
2.7 Summary
Chapter 3 Control of PV Systems under Balanced Grid Faults
3.1 Introduction
3.2 Standards and requirements for PV grid integration
3.2.1 Grid codes
3.2.2 Stationary grid support
3.2.3 Voltage support during grid disturbance
3.3 Control strategies under balanced grid faults
3.3.1 Boost DC‐DC converter control
3.3.2 Two-layer inverter control scheme
3.4 Simulation results
3.5 Summary
Chapter 4 Control of PV Systems under Unbalanced Grid Faults
4.1 Introduction
4.2 Control strategy under unbalanced grid faults
4.2.1 Framework of the proposed control strategy
4.2.2 Fault detection and grid voltage synchronization
4.2.3 Power references calculation
4.2.4 Power reduction strategy for DC-link voltage control
4.2.5 Proposed current reference generators
4.3 Inverter controller implementations
4.3.1 Inner control loop: current controller design
4.3.2 Outer control loops
4.3.3 Inverter current limitation
4.4 Simulation results
4.5 Summary
Chapter 5 Impacts of PV Integration on Voltage Stability of Weak Grids
5.1 Introduction
5.2 Definition and measure of grid strength
5.2.1 Definition of grid strength
5.2.2 Measurement of grid strength
5.3 Overview of voltage stability analysis
5.3.1 Definition of voltage stability
5.3.2 Classification of voltage stability
5.4 Test system and its modeling
5.4.1 Test system
5.4.2 Simplified PV system model
5.4.3 Load modeling
5.5 Impacts of FRT strategies of PV systems on voltage stability of weak grids
5.5.1 Existing FRT control strategies
5.5.2 Proposed FRT control strategy
5.5.3 Case studies for analysis of voltage stability
5.6 Summary
Conclusions and Future Work
Conclusions
Future work
References
Publication During the Doctoral Study
Acknowledgement
Cirriculum Vitae (CV)
本文编号：2846842
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