Robust Strategy for VSC HVDC Transmission System

Project Title

Robust Strategy for VSC HVDC Transmission System

Project Area of Specialization Electrical/Electronic EngineeringProject Summary

In this project focuses on transmitting the power in HVDC (High Voltage Direct Current) system. HVDC system can transmit power over long distances. There are two AC system connected with the DC cable. AC voltages is generated, phase reactors and AC filters are used which reduce the high frequency harmonic contents of AC currents, which will be rectified into DC voltages and transmitted through DC cables after using reactors, filters, dc link capacitors. On DC side dc capacitors used to provide the low inductive path for turned off current and energy storage which controls the power flow and also reduces the voltage ripples. Now DC voltages inverted into AC voltages in a same manner. This project is on VSC (Voltage source converter) based HVDC transmission system which transfer the controlled power and have lower losses. Rectifier side controls the DC voltages and inverter side controls the Active power. VSC makes possible to control the active and reactive power independently. AC voltages set manually to controlled the reactive power flow in each converter without changing DC voltages. By DC voltage on DC side or setting manually or the variation in frequency of AC side to controlled the active power. In this way active and reactive power flow, AC / DC voltages and frequency can be controlled in a VSC HVDC system. VSC based HVDC uses inner current control loop, outer active-reactive power and voltage loop and DC voltage balance control. VSC controller has inner current loop which control the ac currents and that ac current provide by the outer controller. The outer controller consists of dc / ac voltage controller, active / reactive power controller, and frequency controller. So the reference active current obtained from dc voltage controller, active power controller and frequency controller. And the reference of reactive current derived from ac voltage controller and reactive power controller. In this manner, controls the inner current whose output signal is given to the DC voltage balance control which controls DC voltages of DC side through the IGBT/Diode. IGBT/Diode are used for VSC to control the VSC switching rapidly, because there is no telecommunication and commutation failure problem for the stations of VSC HVDC system. For the better performance and high capability HVDC system are used. HVDC is environmentally friendly, providing more energy per square meter over greater distances more efficiently than AC systems, as well as lower losses and less space requirements.

Project Objectives

The main objective of this project is to analyze the technology for transmitting the power between one point to another, controlling active and reactive power the VSC based HVDC system. For fulfilling the objective, enabling objectives are:

• To develop a simulation model f HVDC transmission line.
• To design a VSC controller for transmission line for HVDC transmission system.
• To design a simulation model of VSC HVDC transmission line system by interconnecting the VSC model with the HVDC transmission line.
• Analyze the results of VSC HVDC transmission line system.

Project Implementation Method

• First synchronize the two AC system through transmission line.
• Develop the HVDC transmission line system.
• Design a VSC controller.
• Then interconnect the HVDC transmission line with the VSC controller.
• Observe and Analyze the results.

1.1 Simulink model of HVDC transmission line System 

In the fig 1.1.1 the HVDC model is shown in which the High voltage is given to rectifier which rectifies the AC voltages into the DC voltage through IGBT/Diode. Now After the transmission line DC voltages again convert into the AC voltage through IGBT/ Diode inverter. Here AC voltages is step down through the transformer to get the desired DC voltages for transmitting. AC filters and phase reactors are used to reduce the higher frequency harmonics. Rectifier and inverter utilizes the IGBT / Diode. DC capacitor, DC filter and smoothing reactors are used to store the energy and to reduce the ripples. These same components are used both in rectifier and as well as in inverter.

1.1.1 Simulink model:

                                                                                                                                                                                                                          Fig  1.1.1   1.2 Simulink model of VSC controller:

In the fig 1.2.1 the VSC model is shown in which controlling the inner loop current through the active / reactive power and voltage loop of the system. This current loop signal is used for DC Voltage balancing which will control the output DC voltage. Calculations was done through the Clark’s transformation which gives easiness for the calculation of complex system. These calculations are used now in signal calculation block in which all the basic calculation of the system are done. The output of these blocks were given to a single bus bar for the overall results of the system. It will be approximately same on both sending and receiving side of ac and dc.

1.2.1 Simulink model:

                                                                                                                                                                                                      Fig 1.2.1 1.3 Simulink model of VSC HVDC transmission line system:

In this fig 1.3.1, the VSC controller model is interconnected with HVDC model for transmitting the power over long distances. Controlled pulse of VSC controller is given to the IGBT/Diode. 

1.3.1 Simulink model:

 

 

                                                                                                                                                                                                                    Fig 1.3.1

The results are approximately same it means power delivering over the long distance will be approximately same because the active and reactive power was controlled through the VSC controller. And the current and voltage which were converted are same in both sending and receiving side of the VSC HVDC transmission system.

Benefits of the Project

• The power can be transmitted over the long distances without any power loss. Power will remain same from generation to the distribution side.
• In compare of the conventional HVDC it’s better to control the high voltages with VSC controller through which we can control active and reactive power of the system.
• There is continuous operation because of voltage source which compensate and control for the active and reactive power requirements.
• There will be less losses.
• This control methodology is advanced for high performance operation.
• It can be independently control the voltages and power flow for the application of direct power transfer.
• In this advanced level of power semi-conductor devices used for lower losses and high reliability.
• Low level of maintenance and service required.
• It’s size compact and reduced volume for the installation of flexibility.
• It’s construction and operation costs also reduced.AC filters a

Technical Details of Final Deliverable

230kV, 2000MVA input is given to the voltage through the AC voltage source which was step down for dc voltages and that will be controlled by VSC controller through IGBT/Diode and ripples was reduce by the dc capacitors and reactors same this is on both side rectifier and inverter. At output side 230kV, 2000MVA was recieving.

The above input and output is for the simulink model. for the protype we use lower voltages.

Basically VSC is used for controlling purpose it controls the active and reactive power of the system. Project works on transmitting the power over long distances without power loss and it will be cost efficient because of DC transmission line which has less cost of insulation. This project also works on control methodology on advanced level for high performance operation. This project can be independently control the voltages and power flow for the application of direct power transfer. Voltage will approximately same on both receiving and sending side and power will be transmitted.

Final Deliverable of the Project Hardware SystemCore Industry Energy Other Industries Education Core Technology Clean TechOther Technologies Shared EconomySustainable Development Goals Affordable and Clean Energy, Industry, Innovation and InfrastructureRequired Resources

Item Name	Type	No. of Units	Per Unit Cost (in Rs)	Total (in Rs)
			Total in (Rs)	79010
Raspberry pi	Equipment	2	22000	44000
Transformer	Equipment	2	720	1440
Rectifier / Inverter	Equipment	2	5000	10000
Transmission block	Equipment	1	10000	10000
AC DC couplers	Equipment	2	2000	4000
Voltage Controlling IC	Equipment	2	35	70
Miscellaneous	Miscellaneous	1	9500	9500