Application Note How to simulate SolarEdge power optimizers connected to a non-solaredge inverter in PVsyst

Transcription

1 Application Note How to simulate SolarEdge power optimizers connected to a non-solaredge inverter in PVsyst Contents 1. GENERAL INFORMATION CREATING A NEW PROJECT VARIANT CHANGING SYSTEM PARAMETERS OF THE SOLAREDGE VARIANT General considerations Changing the inverter efficiency Changing the mismatch loss value MAKING CHANGES TO THE 3D SHADING SCENE General considerations regarding the 3D shading scene Shading scene: SolarEdge vs. a traditional inverter PVSYST DATA ANALYSIS General considerations regarding meteorological data Data normalization... 7

2 1. General Information This application note assumes the reader has prior knowledge of the basic use of PVsyst. This paper details the steps needed in order to simulate SolarEdge power optimizers connected to a non- SolarEdge inverter. Adding SolarEdge power optimizers to a PV system ensures that each module is constantly kept at maximum power point (MPP), preventing energy losses due to module mismatch or partial shading conditions. Simulating SolarEdge power optimizers with a non-solaredge inverter in PVsyst is aimed at giving an indication as to the expected energy gain compared to the same system without SolarEdge power optimizers. The steps below will assume that a simulation of the site without power optimizers has been performed and saved as a simulation variant. The SolarEdge simulation (adding the power optimizers) will be saved as an extra variant to the same project file. 2. Creating a new project variant Once a simulation of the PV system without power optimizers has been created and saved as a project variant, you will need to save a new project variant based on it, to which you will apply the changes related to the SolarEdge system. From the main program screen, click Simulation and then click Results In the results screen, click the Save button. A pop-up window appears showing the list of variants in the project. Enter a chosen name for the SolarEdge variant in the Description field and then click Save As New. The popup window will close, and a new project variant with the chosen name will be added. This project variant is identical to the original variant in every way but its name. The next step will be to change the appropriate system parameters of the SolarEdge variant. Creating a new simulation variant

3 3. Changing system parameters of the SolarEdge variant 3.1 General considerations The impact of adding SolarEdge power optimizers in PVsyst will be in two areas: the inverter efficiency and the mismatch loss parameter Click Back and Back to Params to return to the main program screen. Click on the System button to go to the Grid System Definition screen to gain access to the appropriate parameters. 3.2 Changing the inverter efficiency The SolarEdge power optimizers efficiency must be accounted for when calculating the overall efficiency of the system. The best way to achieve this is to multiply the inverter efficiency by the power optimizer efficiency. This is achieved by saving an additional version of the inverter definitions file (.OND), changing its efficiency values, and using it in the SolarEdge simulation variant. Click on the Open button next to the inverter name. This opens the inverter definitions screen. In order to create the new inverter definition file, change the names written in the Model and File name fields. Click OK and then click Save As when prompted. The new inverter file has been created, and you can now make changes to it without affecting the original simulation variant or the original inverter definitions. Note the inverter s name has changed according to the changes you made to the OND file. Creating a new inverter definition file

4 Changing the efficiency values: again, click on the Open button next to the inverter name. Go to the Efficiency curve tab. Here you will enter revised values for the inverter s maximum and EURO efficiency. To calculate the revised efficiency, you will need to multiply the inverter efficiency by that of the power optimizer. For example: Inverter max efficiency = 98.1% Power optimizer max efficiency = 99.5% Revised max efficiency = x = = 97.6% Inverter EURO efficiency = 97.0% Power optimizer EURO efficiency = 98.9% Revised EURO efficiency = x = = 95.93% Once you have calculated and entered the revised efficiency values, click the OK button and save the file when prompted to do so. Changing the inverter efficiency

5 3.3 Changing the mismatch loss value In the System screen (labeled Grid system definitions), click the Detailed losses button. This will bring up a pop-up window allowing you to change different loss parameters such as thermal loss factors, Ohmic losses, soiling losses etc. Click the Module quality Mismatch tab. Change the mismatch losses to zero for both Power Loss at MPP and Loss when running at fixed voltage. Click the Apply this to all subsystems button (if there is more than one subfield in the system) and click the OK button to exit. Changing the mismatch loss parameters 4. Making changes to the 3D shading scene 4.1 General considerations regarding the 3D shading scene If the system in question has shading of any kind (trees, chimneys, inter-row shading) a 3D physical system layout should be designed to account for the energy loss due to shade. An accurate shading simulation will ensure the SolarEdge advantage is reflected in the annual energy output of the system. If needed, you can refer to the PVsyst help files for assistance in constructing a 3D shading scene. PVsyst can calculate the shading according to one of 2 methods: linear and according to strings.

6 1. In Linear shading calculation, the energy loss is linear to the PV area being directly shaded. This method does not take into account the electric interdependency of modules in a string, nor does it allow for the electrical behavior of a partially shaded single module (the protection of bypass diodes). 2. In shading calculation According to module strings, the energy loss due to shading takes into account the effects of partial shading on the entire string. Choosing this method requires division of the PV area in the Near Shadings construction into rectangles corresponding to the size of the strings designed in the System section. This is a more realistic method and therefore more accurate. Use this method to compare a simulation of a traditional system vs. a SolarEdge system, as described below. 4.2 Shading scene: SolarEdge vs. a traditional inverter Unlike a traditional system, in which the production of entire strings is affected by partial shading of as little as one module, a SolarEdge system limits the effects of partial shading to the shaded modules only, thanks to its module-level MPPT. The way to simulate shading in a SolarEdge system in PVsyst is to divide the PV area into strings corresponding to the size of one bypass diode. Depending on the number of bypass diodes in the chosen module, this will usually result in 3-4 substrings per module, running along the long side of the module, as in the image below (module graphics have been inserted for clarity purposes). Once the shading scene is complete and the PV area has been divided into substrings, select the According to module strings option in the Near shadings definition screen and calculate the shading tables. Note: the system variant of the traditional inverter will have an identical shading scene with one exception: in the traditional inverter s shading scene you define the string rectangles based on the physical size of a string (1 rectangle = 1 string), and not based on the bypass diodes.

7 5. PVsyst Data Analysis 5.1 General considerations regarding meteorological data A PVsyst simulation bases its calculations on external meteorological data inserted by the user. As climate varies over time, it is impossible to predict with 100% accuracy how a PV system will perform every year. Since in our case we have a benchmark against which we are comparing the results (the historical site energy production), we should strive to obtain a simulation result that is as close as possible to the existing data. To that end, it is recommended to use the actual meteorological data measured on the site itself to improve the accuracy of the PVsyst simulation. 5.2 Data normalization If no irradiation data is available from the site, meteorological data from available sources should be used instead (common sources are Meteonorm, PVGIS, NASA etc.). Using an external meteorological dataset may lead to a variance between the PVsyst results and the actual energy measured annually from the PV installation. In this case, the result of the PVsyst simulation of the existing site should be normalized against the historical data to provide a basis for comparison to the SolarEdge simulation. Having followed the simulation process described in the previous sections, we will have obtained three energy yield results: 1. Existing energy yield from historical site data denoted M1 2. PVsyst result of the site without power optimizers denoted P1 3. PVsyst result of the site with SolarEdge power optimizers denoted S1 The following table shows an example of how the data may be analyzed. The site s historical energy data is the base against which the PVsyst of the site without power optimizers is compared. The resulting ratio between the real data and the PVsyst simulation forms the normalization factor for the SolarEdge PVsyst simulation, and should be used to calculate the added energy of the SolarEdge system, as shown in the following table: Ratio of historical data to PVsyst of existing site Normalized SolarEdge energy production Added energy with SolarEdge power optimizers Added energy in %