Solar 1.5MVA power System’s Grid Connection Feasibility Study

This case study evaluates a Solar Power Plant impact on the network operation and to determines the maximum power of PV system

Main objective

To evaluate Solar Power Plant impact on network operation and to determine maximum solar PV power that can be installed at the connection point.

Performed calculations

Long-time voltage level, voltage fluctuation, harmonics, short circuits. Analyzed minimal loading system operation mode.

Voltage level and fluctuations

Calculations are performed assuming the worst-case scenario: all other solar power plants connected to the same distribution line are operating at maximum installed power and energy consumption is equal to zero. It is assumed that other solar power plants generate only active power. Analyzed 1.5 MVA solar power plant generation is evaluated with power factor („PF“) values of -0.9, 0, and +0.9.

Based on calculation results, solar power plant connected to the network would increase voltages at other substations on this line by 5 %.


EA-PSM Energy System Calculations softwareFigure 1. Modeled network scheme

Because voltage change in the power plant turning on/off case is higher than 5%, the amount of permissible voltage changes is limited (up to 4 times a day). As power generation depends on the level of cloudiness, the number of voltage fluctuations can increase. Because of that, the designed 1,5 MVA Solar power plant does not meet requirements for energy quality.  

Based on energy quality requirements for voltage, in this particular case, it would be recommended to install a power plant that would generate voltage fluctuations at a connection point not greater than 3%. Such requirement would be met by 1,15 MVA power plants operating at PF=0 operation mode or 0,84 MVA power plants operating at PF = -0.9 mode. Since electrical network legislation requires for the power plant to be able to operate at PF ≠ 0 mode, it is only possible to connect the power plant with lower installed power.

Higher harmonics

Designed Solar power plant generated total harmonic voltages distortion at the connection point is significantly lower (0,2%) comparing to standard limits (8%), THD of harmonic currents is 0,855%.

All harmonics are within permissible limits.

Figure 2. Harmonic currents

Figure 3. Harmonic voltages

Short circuit calculations

Solar power plant-generated short circuit current is up to 6.5% from the overall network and power plant short circuit current.

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