Although the introduction of distributed power sources will bring some power quality problems to the system, distributed power sources also have the potential to improve power quality.
(1) Distributed power supply has backup and emergency functions. Distributed power supply has a small capacity of a single unit, a large number of units, and a relatively scattered distribution. It is convenient and quick to start and stop, and the operation control has strong flexibility. Under the relevant control strategy, the distributed power supply can be put into use in a short time, and can also be quickly withdrawn from operation as needed.
If the distributed power source can continue to operate in the event of grid failure and disturbance, or can be converted to a backup power source, it is very helpful for reducing the power failure range or shortening the power failure time, and it also has a restraining effect on the voltage sag problem of many nodes.
(2) Coordinate control according to load changes. The distance between distributed power and power users is very close, and it is easy to realize the nearby supply of active power and the nearby compensation of reactive power, and the transmission loss is small. In the traditional distribution network, when the user’s load suddenly increases or decreases greatly, the voltage of the power supply line will decrease or increase significantly. If the number of changes in the user load is large and dynamic, it will also cause problems such as voltage fluctuations and flicker. When the distributed power supply and the local load can operate in coordination (the output of the distributed power supply changes synchronously with the load), the fluctuation of the system voltage will be suppressed. Specifically, if the distributed power supply can also be included in the unified dispatching management of the power grid, when the user load suddenly increases or decreases greatly,, the output power of the distributed power supply can be adjusted accordingly to compensate or offset the power fluctuation of the load, thereby suppressing the fluctuation of the voltage.
(3) The specially equipped compensation device is also helpful to improve the system voltage quality. When many distributed power sources are connected to the grid, they are often equipped with some reactive power compensation devices or energy storage devices. These compensating devices are connected to the access point of the distributed power supply. While compensating for the power quality problems of the distributed power supply itself, they must also improve the original power quality problems in the distribution network.
Distributed power sources and grid-connected converters also serve as compensation equipment. The grid-connected converters of distributed power sources are very similar to the circuit structure and control technology used in power quality adjustment devices such as active power filters and static var generators. This opens up possibilities for optimal configuration of both types of equipment. The optimal configuration system utilizes the existing power electronic equipment to absorb or release active and reactive power, thereby not only realizing the transmission and conversion of electric energy, but also improving the power quality of the system and reducing the additional investment of the system.
Of course, the power electronic conversion equipment of the distributed power source itself cannot completely replace the technical equipment to improve the power quality in the traditional power grid. However, if the distributed power source is applied to the flexible power technology of the distribution network, it can not only improve the power quality level, but also can reduce the use of passive filters and active filters, save a lot of investment in harmonic control, will bring huge economic and social benefits.
Read more: Improvement measures for power quality.