Differences between HVDC VSC system and CSC system

Hi this is Min and i am writing this posting for letting you know about differences between HVDC VSC system and CSC system.

HVDC VSC (Voltage Source Converter) and HVDC CSC (Current Source Converter) are two different types of high-voltage direct current (HVDC) transmission technologies. They differ in a number of ways, including:

Feature                                                HVDC VSC                                    HVDC CSC

Device type	Self-commutated	Line-commutated
Device characteristic symmetry	Asymmetrical	Symmetrical
Short-circuit current	Higher	Lower
Rate of rise of fault current	Fast	Limited by DC reactor
Losses	Lower	Higher
AC capacitors	Not required	Required
DC capacitors	Required	Not required
Interface with AC system	More complex	Less complex
Reactive power generation	Independent of energy storage	Depends on current flowing through energy storage
Performance	Better	Good
Harmonics	Less	More

HVDC VSC technology is newer and more advanced than HVDC CSC technology. It offers a number of advantages, including:

• Black start capability: HVDC VSC systems can start up without the need for an external AC power supply. This is important for applications such as connecting offshore wind farms to the grid.
• Flexible control: HVDC VSC systems can be controlled independently of the AC power systems on either side of the link. This allows for greater flexibility in power transmission and grid management.
• Low harmonics: HVDC VSC systems produce less harmonic distortion than HVDC CSC systems. This is important for maintaining the quality of the AC power supply.

However, HVDC VSC systems are also more expensive than HVDC CSC systems.

HVDC CSC technology is still widely used in existing HVDC transmission systems. However, new HVDC transmission systems are increasingly using HVDC VSC technology.

Here is a table summarizing the key differences between HVDC VSC and HVDC CSC:

Feature                                                HVDC VSC                                    HVDC CSC

Device type	Self-commutated	Line-commutated
Device characteristic symmetry	Asymmetrical	Symmetrical
Short-circuit current	Higher	Lower
Rate of rise of fault current	Fast	Limited by DC reactor
Losses	Lower	Higher
AC capacitors	Not required	Required
DC capacitors	Required	Not required
Interface with AC system	More complex	Less complex
Reactive power generation	Independent of energy storage	Depends on current flowing through energy storage
Performance	Better	Good
Harmonics	Less	More
Advantages	Black start capability, flexible control, low harmonics	More mature technology, lower cost
Disadvantages	More expensive	Lower performance, higher harmonics

Which type of HVDC technology is best depends on the specific application. HVDC VSC technology is generally preferred for new HVDC transmission systems due to its advantages in terms of performance and flexibility.

However, HVDC CSC technology is still widely used in existing HVDC transmission systems and maybe a more cost-effective option for some applications.

I hope this posting can be helpful for broadening your knowledge.

Min, P.E.