scholarly journals Current source converter-based offshore wind farm: configuration, modulation, and control

2021 ◽  
Author(s):  
Qiang Wei
Keyword(s):  
Wind Farm ◽  
Current Source ◽  
Offshore Wind ◽  
Modulation Scheme ◽  
Offshore Wind Farm ◽  
Control Schemes ◽  
Current Source Converter ◽  
Power Balancing ◽  
And Control ◽  
Low Order

Offshore wind power is attracting increased attention because of considerable wind resources, higher and steadier wind speeds, and smaller environmental impact. Recently, a current source converter (CSC)-based series-connected configuration is proposed and it is considered a promising solution for offshore wind farms as the offshore substation used in existing systems can be eliminated. However, such a CSC-based configuration has disadvantages in terms of size and weight, dynamic performance, cost, reliability, and efficiency. Therefore, this thesis proposes new configurations, modulation scheme, and control schemes to improve the performance of the CSC-based offshore wind farm. First, a new configuration is proposed for the CSC-based offshore wind farm. Compared with existing CSC-based configurations, the new one is expected to be smaller in size and weight. Second, conventional space vector modulation (SVM) with fast dynamic response cannot be used for grid-side CSCs because of its high-magnitude low-order harmonics. To solve this issue, an advanced SVM with superior low-order harmonics performance is proposed. Third, power balancing among series-connected CSCs is an important consideration for system reliability. The possible imbalance of power is investigated and quantitatively defined. A power balancing scheme is proposed, based on which equal power distribution among CSCs is ensured. Fourth, to lower the system insulation requirement of the CSC-based configuration, a bipolar operation is investigated. Compared with monopolar mode, bipolar mode gives lower insulation level, thus contributing to the system in terms of lower cost and higher reliability for a given power rating. In addition, an optimal dc-link current control giving higher efficiency is proposed for the bipolar system. Fifth, an optimized control strategy with reduced cost and improved efficiency is proposed for the CSC-based offshore wind farm. The nominal number of onshore CSCs is optimized, which reduces the cost on power converters. And an optimized bypass operation is introduced to onshore CSCs, which improves the efficiency of the system. Finally, simulation and experimental results are provided to verify the performance of the proposed configuration, modulation scheme, and control schemes.

scholarly journals Current source converter-based offshore wind farm: configuration, modulation, and control

2021 ◽  
Author(s):  
Qiang Wei
Keyword(s):  
Wind Farm ◽  
Current Source ◽  
Offshore Wind ◽  
Modulation Scheme ◽  
Offshore Wind Farm ◽  
Control Schemes ◽  
Current Source Converter ◽  
Power Balancing ◽  
And Control ◽  
Low Order

Offshore wind power is attracting increased attention because of considerable wind resources, higher and steadier wind speeds, and smaller environmental impact. Recently, a current source converter (CSC)-based series-connected configuration is proposed and it is considered a promising solution for offshore wind farms as the offshore substation used in existing systems can be eliminated. However, such a CSC-based configuration has disadvantages in terms of size and weight, dynamic performance, cost, reliability, and efficiency. Therefore, this thesis proposes new configurations, modulation scheme, and control schemes to improve the performance of the CSC-based offshore wind farm. First, a new configuration is proposed for the CSC-based offshore wind farm. Compared with existing CSC-based configurations, the new one is expected to be smaller in size and weight. Second, conventional space vector modulation (SVM) with fast dynamic response cannot be used for grid-side CSCs because of its high-magnitude low-order harmonics. To solve this issue, an advanced SVM with superior low-order harmonics performance is proposed. Third, power balancing among series-connected CSCs is an important consideration for system reliability. The possible imbalance of power is investigated and quantitatively defined. A power balancing scheme is proposed, based on which equal power distribution among CSCs is ensured. Fourth, to lower the system insulation requirement of the CSC-based configuration, a bipolar operation is investigated. Compared with monopolar mode, bipolar mode gives lower insulation level, thus contributing to the system in terms of lower cost and higher reliability for a given power rating. In addition, an optimal dc-link current control giving higher efficiency is proposed for the bipolar system. Fifth, an optimized control strategy with reduced cost and improved efficiency is proposed for the CSC-based offshore wind farm. The nominal number of onshore CSCs is optimized, which reduces the cost on power converters. And an optimized bypass operation is introduced to onshore CSCs, which improves the efficiency of the system. Finally, simulation and experimental results are provided to verify the performance of the proposed configuration, modulation scheme, and control schemes.

scholarly journals Current Source Converter Based Offshore Wind Farm: Configuration and Control

2021 ◽  
Author(s):  
Miteshkumar Nandlal Popat
Keyword(s):  
Wind Farm ◽  
Current Source ◽  
Wind Farms ◽  
Offshore Wind ◽  
Grid Integration ◽  
Offshore Wind Farm ◽  
Offshore Wind Farms ◽  
Control Scheme ◽  
Current Source Converter ◽  
Grid Side

Recently, offshore wind farms have emerged as the most promising sector in the global renewable energy industry. The main reasons for the rapid development of offshore wind farms includes much better wind resources and smaller environmental impact (e.g., audible noise and visual effect). However, the current state of the offshore wind power presents economic challenges significantly greater than onshore. In this thesis, a novel interconnecting method for permanent magnet synchronous generator (PMSG)-based offshore wind farm is proposed, where cascaded pulse-width modulated (PWM) current-source converters (CSCs) are employed on both generator- and grid-side. With the converters in cascade to achieve high operating voltages, the proposed method eliminates the need for bulky and very costly offshore converter substation which is usually employed in voltage source converter (VSC) high voltage DC (HVDC)-based counterparts. Related research in terms of control schemes and grid integration are carried out to adapt the proposed cascaded CSC-based offshore wind farm configuration. The large distance between generator- and grid-side CSC in the proposed wind farm configuration addresses significant challenges for the system control. In order to overcome the problem, a novel decoupled control scheme is developed. The active and reactive power control on the grid-side converters are achieved without any exchange of information from the generator-side controller. Therefore, the long distance communication links between the generator- and grid-side converters are eliminated and both controllers are completely decoupled. At the same time, the maximum power tracking control is achieved for the generator-side converters that enable full utilization of the wind energy. Considering inconsistent wind speed at each turbine, a coordinated control scheme is proposed for the cascaded CSC-based offshore wind farm. In proposed control strategy, the wind farm supervisory control (WFSC) is developed to generate the optimized dc-link current control. This enables all the turbines to independently track their own MPPT even with inconsistent wind speed at each turbine. Grid integration issues, especially the fault ride-through (FRT) capability for the cascaded CSC-based offshore wind farm are addressed. Challenges in implementing existing FRT methods to the proposed offshore wind farm are identified. Based on this, a new FRT strategy using inherent short circuit operating capability of the CSC is developed. Moreover, the mitigation strategy is developed to ensure the continuous operation of the cascaded CSC-based offshore wind farm when one or more turbines fail to operate. Simulation and experimental verification for various objectives are provided throughout the thesis. The results validate the proposed solutions for the main challenges of the cascaded current source converter based offshore wind farm.

scholarly journals Current Source Converter Based Offshore Wind Farm: Configuration and Control

2021 ◽  
Author(s):  
Miteshkumar Nandlal Popat
Keyword(s):  
Wind Farm ◽  
Current Source ◽  
Wind Farms ◽  
Offshore Wind ◽  
Grid Integration ◽  
Offshore Wind Farm ◽  
Offshore Wind Farms ◽  
Control Scheme ◽  
Current Source Converter ◽  
Grid Side

Recently, offshore wind farms have emerged as the most promising sector in the global renewable energy industry. The main reasons for the rapid development of offshore wind farms includes much better wind resources and smaller environmental impact (e.g., audible noise and visual effect). However, the current state of the offshore wind power presents economic challenges significantly greater than onshore. In this thesis, a novel interconnecting method for permanent magnet synchronous generator (PMSG)-based offshore wind farm is proposed, where cascaded pulse-width modulated (PWM) current-source converters (CSCs) are employed on both generator- and grid-side. With the converters in cascade to achieve high operating voltages, the proposed method eliminates the need for bulky and very costly offshore converter substation which is usually employed in voltage source converter (VSC) high voltage DC (HVDC)-based counterparts. Related research in terms of control schemes and grid integration are carried out to adapt the proposed cascaded CSC-based offshore wind farm configuration. The large distance between generator- and grid-side CSC in the proposed wind farm configuration addresses significant challenges for the system control. In order to overcome the problem, a novel decoupled control scheme is developed. The active and reactive power control on the grid-side converters are achieved without any exchange of information from the generator-side controller. Therefore, the long distance communication links between the generator- and grid-side converters are eliminated and both controllers are completely decoupled. At the same time, the maximum power tracking control is achieved for the generator-side converters that enable full utilization of the wind energy. Considering inconsistent wind speed at each turbine, a coordinated control scheme is proposed for the cascaded CSC-based offshore wind farm. In proposed control strategy, the wind farm supervisory control (WFSC) is developed to generate the optimized dc-link current control. This enables all the turbines to independently track their own MPPT even with inconsistent wind speed at each turbine. Grid integration issues, especially the fault ride-through (FRT) capability for the cascaded CSC-based offshore wind farm are addressed. Challenges in implementing existing FRT methods to the proposed offshore wind farm are identified. Based on this, a new FRT strategy using inherent short circuit operating capability of the CSC is developed. Moreover, the mitigation strategy is developed to ensure the continuous operation of the cascaded CSC-based offshore wind farm when one or more turbines fail to operate. Simulation and experimental verification for various objectives are provided throughout the thesis. The results validate the proposed solutions for the main challenges of the cascaded current source converter based offshore wind farm.

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