High voltage dynamic reactive power compensation - SVG

High voltage dynamic reactive power compensation - SVG

SVG Principle 

SVG is the representative of newest technology in var compensation area. SVG is connected in parallel to the grid, similar to a variable var current source. Its var current can change following the vary of load var current rapidly and automatically. Since the response speed of SVG is very fast, it is also called Static Synchronous Compensator, STATCOM for short.

SVG’s fundamental configuration is 2-phase or 3-phase self commutated bridge circuits adopting full controlled power electronic semiconductor devices (like IGBT and IGCT). Through reactors the SVG is connected in parallel to the grid. By adjusting the output voltage amplitude and phase angle or direct controlling AC side current, the SVG can absorb or generate var according to the load reactive power or the grid voltage level.

SVG is provided with an overwhelming advantage when it is used for voltage control. The lower the system voltage is, the more dynamicreactive support is needed to support voltage. The reactive current output by SVG has nothing to do with the system 

voltage and may be considered as a controllable constant current source. While, the lower the system voltage is, the lower 

capacity TCR/MCR-type SVC may have to output reactive current.

Technical Advantages of Wanlida SVG

SVG is the most advanced var compensator technologically, which realizes an evolution of reactive power compensation mode basedon voltage source converter. Big volume capacitors and reactors are no longer needed. SVG uses HV IGBT or IGCT with 

high switching frequency to realize reactive power regulation. Therefore, SVG has the following advantages compared with 

traditional compensation methods:

Faster response speed

SVG response time: ≤5ms 

Traditional static compensator response time: ≥10ms.

SVG can finish the conversion from rated capacitance var to rated inductance var in a very short time. This unexampled 

response speed makes SVG very suitable for impact load compensation.

Stronger voltage flicker restrain capability

SVC can restrain voltage flicker to 2:1 in maximum, but SVG can achieve 5:1, even higher. SVC cannot improve its capability for 

voltage flicker mitigation even with high capacity because of low response speed. But SVG responds fast. When its capacity is 

increased, the capability of voltage flicker mitigation can be further improved.

Wide operation range

SVG can work from rated inductive power to rated capacitive power. So compared with SVC, SVG operation range is much wider. Furthermore, SVG can output rated reactive current even under low system voltage.

Multiple compensation function

SVG is not only functioned as fast reactive power compensator, but also harmonics and unbalance compensator according to 

different demands of different clients.

Low harmonic content

SVG utilizes PWM, 3-level and multiple technologies. Therefore, it generates very low harmonics with compensating load harmonics at the same time. Thus, SVG becomes a true multifunctional compensator.

Small volume

HV big capacitors and reactors are not necessary. SVG installation area is greatly smaller than that of the same capacity SVC, only 50% or even lower. At the same time, Wanlida cooperates with the No.1 Science university in China---Tsinghua University

to develop SVG, but the most important advantage for Wanlida is that we have many years experiences for Medium voltage 

variable frequency drives technology, because the Static Var Generator has almost structure and technology with Medium 

voltage variable frequency drives, in addition, Wanlida has over 21 years experiences for protection relays for reactor, 

capacitor etc.

The Structure of Wanlida SVG

It mainly consists of reactor, start-up cabinet, cascade multilevel inverters cabinet and control cabinet.