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Three-phase imbalance governance solution

长沙恒开电气设备有限公司 长沙恒开电气设备有限公司


Three-phase unbalanced solution

◆ Accurately adjust the three-phase current of the system and reduce the center line current

◆ Bidirectional, continuous and dynamic reactive power compensation with a compensation accuracy of 99%

◆ Take into account the filter compensation function to improve the power quality of the distribution transformer in the station area

◆ Stabilize the system voltage and increase the voltage qualification rate

Three-phase unbalanced technology

◆ Pure SVG module

◆ Controller + commutation switch

◆ SVG + capacitor reactance combination

◆ SVG + commutation switch



Commutation switch type: switch the single-phase load of the heavy-load phase of the station area to the light-load phase, and realize load balancing distribution from the load side. The effect of governance is extremely uncertain.


Capacitor type: The capacitor-type three-phase load automatic adjustment device uses wangs theorem to connect power capacitors between phase lines to achieve active power transfer, balance active power between phases, reduce three-phase unbalance, and improve power factor. Capacitor type has low cost and can realize step compensation, but the control effect is poor and there is hidden danger of harmonics.


Power electronic type: The power electronic type three-phase unbalanced automatic adjustment device takes the three-phase full-bridge power unit composed of IGBTs as the core, and realizes the accurate adjustment of the three-phase current by means of current absorption → energy storage → current transfer; as a kind of Source-type products can also perform linear compensation for reactive current and harmonic current. The compensation accuracy of power electronic products is high, but the cost is also high, which does not meet the needs of economic development.


Power electronic type + commutation switch: "Power electronic type + commutation switch" combines the advantages of power electronic products and commutation switches, can solve the three-phase imbalance problem from the user side, compared with pure power electronic products, the cost is significantly reduced, And can achieve stepless adjustment.



"SVG + Commutation Switch"

The "SVG + commutation switch" hybrid compensation device is a set of products used to control the three-phase unbalance of the low-voltage distribution station area. It is suitable for the three-phase four-wire 380V / 220V low-voltage distribution system, which can quickly and accurately detect the three-phase imbalance of the low-voltage distribution system. The single-phase load can be roughly adjusted by the commutation switch in real time without power outage, and the SVG fine adjustment mode To make the three-phase load in the station area relatively balanced. This product can effectively reduce the loss of transformers and lines, suppress the occurrence of single-phase overcurrent and low voltage at the terminal, and eliminate many hidden dangers caused by three-phase imbalance.


Device composition

The "SVG + commutation switch" hybrid compensation device consists of one SVG module and multiple commutation switches (proportioning according to the actual situation on site). The SVG module is an intelligent control and compensation device that integrates sampling, calculation, communication, human-computer interaction, intelligent networking, and balanced logic algorithms. The commutation switch is an intelligent switching device that integrates sampling, calculation, communication, and phase sequence switching functions.


Technical principles


The "SVG + commutation switch" hybrid compensation device uses wireless communication to communicate, with SVG as the master and commutation switch as the slave.

An SVG module is installed at the outlet of the distribution transformer, which is responsible for monitoring the three-phase unbalance information and issuing adjustment commands. The branch installs several commutation switches along the front end of the user. The commutation switch can monitor the load of its own load circuit Information, and perform the corresponding commutation operation according to the commutation command issued by the SVG module. If the three-phase unbalance still exists, the three-phase absolute balance can be achieved through the SVG fine-tuning mode.

In order to guarantee the service life, the commutation switch adopts zero-crossing switching technology to minimize the damage to the moving components and electrical equipment by switching. The zero-crossing switching technology is based on the principle of "current zero-crossing removal, voltage zero-crossing input", which can achieve the effect of minimal impact and minimal arc.





  1) Automatically balance three-phase load

  Real-time monitoring of three-phase unbalance, and automatic adjustment of three-phase load according to the unbalance, commutation time ≤10ms, without interrupting the user's power supply, will not cause the reset and restart of common electrical appliances, and will not cause damage to electrical appliances

  2) Reduce transformer losses

  The transformer is in a relatively balanced operation state, which effectively reduces the iron loss and copper loss of the transformer.

  3) Solve the problems of low pressure and overvoltage

  Solve the problems of low voltage and overvoltage caused by three-phase imbalance, and avoid burning out electrical equipment due to overvoltage or affecting the normal operation of electrical equipment due to low voltage.

  4) Protect the safe operation of low-voltage distribution networks

  Avoid heat and old damage caused by long-term excessive neutral current, and eliminate the hidden danger of transformer and other power distribution equipment burning.


Program features

Maintenance-free and management-free; automatic commutation without interrupting the user's power supply; reliable phase-to-phase protection technology; switching elements consume no power and the device consumes little power.


Product advantages

  More reliable-the core devices are all well-known brands to ensure the life of the product;

  More energy-saving-through standby threshold and start and stop time period settings can effectively reduce their own running losses;

  More flexible-the function modes can be freely combined, and the field wiring is not restricted by the phase sequence, making the installation easier;

  More intimate-one-stop services such as pre-sales and after-sales support and program design can be provided to customers;

  More convenient-product status monitoring and debugging can be achieved through mobile phones, mobile terminals and remote backgrounds;


Capacity configuration

Transformer capacity

SVG capacity

Commutation switch
















Project application

  Case number one

  A project site: Since the power load of the residential users is single-phase, the distributed power sources such as small wind turbines and photovoltaic panels prepared by the residents are mostly single-phase power sources. When these power sources are connected to the power grid, three-phase power will be caused. Unbalance; there is randomness in user power consumption, which will also cause three-phase unbalance; with the increase of load during peak power consumption, the three-phase unbalance degree of the power grid is seriously aggravated. If the zero-line current is higher than the designed current-carrying capacity for a long time, it will cause the zero-line overload and burn out, causing failure. In order to solve the hidden dangers of power quality problems in the power grid, InBev Electric researched solutions and thoroughly solved the impact of accidents caused by three-phase imbalance through technical measures.

  The solution provided by our company: add a set of three-phase unbalance adjustment device using the dual management method of line management and distribution station area. The device mainly includes a 35KVAR SVG device installed in the station area and 6 installed in the Commutation switch in the line.





Diagram of the power quality of the device in the reception area




SVG exit, power quality situation diagram after the commutation switch is put in




Diagram of system power quality after SVG and commutation switch are all put in



Trend curve of three-phase current before treatment



Trend curve of three-phase current after treatment


Power Supply Bureau background data



Contact us

Address: Building 3, Xingsha International Enterprise Center, Changsha Economic and Technological Development Zone

Changsha Hengkai Electrical Equipment Co., Ltd.