Static synchronous compensator for electric traction

Static synchronous compensator for electric traction

Main Functions

Improve the stability of power transmission

In long distance transmission system, Static synchronous compensator (STATCOM) can not only compensate the power line losses caused byreactive power, increase line voltage and improve effective transmission capacity under normal operation,but also offer reactive power adjustment in time, damp system oscillation and improve system stability incase of fault.

Maintain the receiving-end voltage level

Since high capacity load centers lack reactive power support, it is easy to cause grid voltage dip, evencause voltage collapse. However, Static synchronous compensator (STATCOM) is capable of fast var adjustment. Therefore, the receiving-endvoltage level is greatly stabilized.

Reactive power compensation leading to high power factor and low line losses

Many types of loads need a mass of reactive power when operation, such as asynchronous motors, arcfurnaces, rolling mills and high rating rectifiers. At the same time, the upstream transformer and lineimpedance also generate reactive power, which still leading to low power factor.

For the power system, loads with lower power factor will increase the line losses, voltage drop anddeterioratevoltage quality. Additionally, reactive power will reduce efficiency of power generation,transmission and distribution. For clients, low power factor will increase production costs.

Restrain voltage fluctuation and flicker.

Voltage fluctuation and flicker are mainly caused by rapid loads variation. This rapid variation also causesthe load current fluctuation dramatically. The current variation leads to system voltage losses changingvery fast, which brings the receiving-end grid voltage flicker. The typical loads that cause voltage flicker arearc furnaces, rolling mills, electric locomotives, etc.

Static synchronous compensator (STATCOM/SVG) can offer fast reactive power regulation, which mitigate voltage fluctuation and flicker easily caused byloads variation.

Now, Static synchronous compensator (STATCOM/SVG) is the best solution to restrain voltage fluctuation and flicker compared with MCR, TCR etc.

Mitigate 3-phase unbalance.

In distribution network, there are a lot of 3-phase unbalance loads, typically like electric locomotives and arcfurnaces. At the same time, line and transformer impedance unbalances can also cause voltage unbalanceproblem. Static synchronous compensator (STATCOM) can fast compensate negative sequence current caused by unbalance loads, which ensurebalanced 3-phase grid current. Thus, it improves the power supply quality greatly.

Eliminate harmonics including Even-order, Odd-order, subharmonic and inter-harmonics(Option)

Static synchronous compensator (STATCOM/SVG) has very good harmonic suppression functions including even-order harmonic, odd-order harmonic, subharmonic and inter-harmonics, it adopted Instantaneous power theory to detect and calculate harmonic current automatically and then control PWM converter, and input compensated current into power grid which is of the right magnitude with harmonic current, but with inverse polarity.

Structure of Wanlida Static Synchronous Compensator

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

Technical Advantages 

Static Synchronous Compensator  has the following advantages compared with traditional compensation methods:

Faster response speed

STATCOM response time: ≤5ms 

Traditional static compensator response time: ≥10ms.

STATCOM can finish the conversion from rated capacitance var to rated inductance var in a very short time. This unexampled response  speed makes STATCOM very suitable for impact load compensation.

Stronger voltage flicker restrain capability

SVC can restrain voltage flicker to 2:1 in maximum, but STATCOM 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 STATCOM responds fast. When its 

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

Wide operation range

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

Multiple compensation function

STATCOM 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

STATCOM utilizes PWM, 3-level and multiple technologies. Therefore, it generates very low harmonics with compensating load 

harmonics at the same time. Thus, STATCOM becomes a true multifunctional compensator.

Small volume

HV big capacitors and reactors are not necessary. STATCOM 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.

Technical Features

• Provides fast smooth dynamic compensation from inductive to capacitive in reactive power, also eradicates reactive power delivery to power grid, it can meet the maximum request to compensate power factor and keep power factor close to 1.0 anytime.
• Low power loss, more better economical operation.
• Has powerful capability to support voltage and ability to continuously operate under the 1.1 times of overload.
• More fast response time and better effect for restraining flicker.
• Produce no harmonic and and compensate nearly all load harmonics without amplifying them and without generating harmonic resonance, it has more safety, stability and reliability because it is not sensitive to the system power parameters.
• Modular design. All power units are the same in structure and electric performance,thus they are interchangeable, which is easy for installation and maintenance. Redundant N+1 structure provides more higher reliability.

• Less space for installation.

Technical Specifications

Factory Acceptance Test

We built the first-class high voltage and big capacity power electronic equipments test platform to realize Factory Acceptance Testing for whole machine before delivery.