Power Factor Control, Balancing Active and Reactive Power

What is active and reactive power management and how does it relate to solar PV plants?

Active power (W) is real power, or useful power that can be used to do work and power loads (appliances, lamps, etc.). Reactive power (VAR) is the imaginary power or apparent power which does not do any useful work but has a significant impact on system performance, components, stability and overall system economy.

When there is an increase in power demand, the current drawn from the transmission line is high, this in turn reduces voltages at the load end.  When the power demand is low, the supply voltage level on the load end is very high. Each of these cases will cause an imbalance in the system.

Reactive power management is an essential part of how voltage levels are controlled in the electrical power system. In effect, reactive power can be adjusted as a means of raising voltage levels or absorbed as a means of lowering voltage levels.

A solar PV plant is an intermittent power source, dependent on the fluctuating sunlight local to the area where it is installed. Most inverters installed are set to produce real power only. This can be a problem for commercial sites that have a poor power factor. If a solar PV inverter supplies only real power then the power factor at the site may drop significantly. This not only causes voltage regulation problems at the site but could also trigger utility penalties or surcharges.

Balancing active and reactive power along with power factor control enables more operating flexibility and increased system reliability. Power factor control can benefit solar plant owners and operators by increasing load capacity and reducing power losses, improving voltage and deferring upgrades.

How can Solar-Log® achieve active and reactive power control through power factor control for solar PV plants?

Plant operators can set internal parameters at the inverter level which allow the inverter to operate at a fixed power factor or to vary reactive power. Varying reactive power would depend upon the generation level or the voltage at the inverter terminals.

Controlling active power and regulating reactive power is typically a serious technical challenge. Most inverters are not capable of dynamically injecting or absorbing reactive power in response to local voltage measurements automatically.

This technical challenge is simplified with Solar-Log®.  The Solar-Log® 1900 PM+ and the Solar-Log 2000 PM+ have made this easy through I/O ports that can receive and send a wide range of signals from various grid operators. The Solar-Log® 1900 PM+ and the Solar-Log 2000 PM+ can be combined with a Solar-Log® meter for measured values such as active power, reactive power, voltage and currents. Using the information provided by the meter, the Solar-Log® can control reactive power at the feeding point.

Solar-Log® creates a flexible solution for utility operators by providing a dynamic platform capable of injecting or absorbing reactive power in response to local voltage measurements. The system can maintain voltage levels within their normal ranges and improve efficiency through the addition of I/O’s and energy relays. Solar-Log® allows grid operators to control the active and reactive power based upon generation, load and self-consumption.

This solution, in turn, balances power flow (active and reactive power) and provides power factor control during high peak demand. Other functions such as the fixed value, cos phi shift factor or performance-related cos phi functions can be implemented without additional measurements with the solution provided.