Robin Vincent

With Peak shaving, the strategy is relatively simple: charge the battery with excess energy and discharge the battery into the grid up to the grid limitation value. You could set up your system to start discharge during the night (i.e with PV zero production). In this case, you will discharge at the max inverter power (20MW) until the battery is empty. To ensure your battery is fully charged each day, you can use the power shifting strategy instead Using the "Fixed charging power before exporting" will prioritize battery charging before grid injection. This won't guarantee a full 40MWh/day of charging if the PV production is lower than that, but you should be closer to your target. This will probably lower your overall PV production though, since the battery will be more likely to be fully charged when your PV production reaches the grid limitation.

With the Peak shaving strategy, you will indeed put any excess production into the battery with respect to the charger max power and battery state of charge. In these conditions, you can charge your battery up to 20MW, but only if the total AC power is 50+20MW. Your system will always output less than 70MW (max clear sky production being estimated to 68.23MW), but will also charge for more than 2 hours a day, so your daily charging energy will be somewhere between 0 and 40MWh/day. The actual energy will depend on the weather and battery state of charge at the beginning of the day, so you cannot predict the charging/discharging energy based on the max charging power.

From your table, I understand you have in one case 2*2 MPPT with 2 strings each, and on the other one only 2 MPPT with 2 strings each, is that correct ? You may or may not see any difference in your results depending on how you've set your simulation parameters. Having two strings per MPPT may result in a lower production when : The combined strings power or current exceed the MPPT limits. The voltage mismatch value in the detailed losses in not null. Please also note that the maximum MPPT power depends on the power sharing option. If you have unbalanced MPPT input power, you can redistribute the total inverter power accordingly. This will let the MPPT connected to two strings to have a higher power limit, and strongly reduce the difference between your two configurations

There is a known issue where the total AC power in the report is not accurate with SolarEdge subarrays. This is due to the way the total is computed in the report, based on individual MPPT powers. With SolarEdge and its specific way to attribute (and distribute) strings to inverters, the computation is sometimes incorrect. This issue is on our roadmap, but as it does not impact the simulation results, it has been scheduled for a later version.

In both versions an issue may happen for systems using the power shifting strategy with transformers losses. The issue happens when most of the PV production is diverted to the battery or most of the grid injection comes from the battery. In these cases the AC losses computation may lead to unrealistic values. This issue will be corrected in the next release. In the meantime, users are strongly advised to use PVsyst 8.0.17 for projects using power shifting.

Optimizers won't necessarily increase the system production. Optimizers are especially useful when a part of the string is partially shaded, and has a different Impp (current at max power point) from the rest. Without optimizers, the whole string have to use the current of the worst module, leading to a lower overall production. With optimizers, the shaded and unshaded modules can operate at their own optimum current, the optimizers ensuring the output current to be the same. But when you don't have partial shadings, optimizers cannot improve anything. And since optimizers have their own efficiency, they end up increasing the system losses, leading to a lower PR.

For SolarEdge system there is two different advanced parameters limiting the Pnom ratio, one for inverters with less than 25kW nominal power, on for more than 25kW. Since the 50kUS is set to 16.7kW (1/3 of the physical inverter), the <25kW parameter. Please check these parameters in the advanced parameter menu (Settings => edit advanced parameters) You should be able to simulate your system if you change the parameter 404 to something higher than 39%

This is a known, but benign, issue where the total AC power is not always well recomputed when you have inverters with MPPTs connected to varying DC power. This is due to the total AC power being the sum of each MPPT equivalent AC power, itself based on the power sharing options. This approach is necessary to be able to deal with fraction of inverters, but may lead to small discrepancies in total. We will solve that in a future PVsyst version.

Since PVsyst 8.0.17, you have the possibility to use the "power shifting" strategy in Grid storage. If you do so and select "Fixed charging power before exporting" you can set it to charge as much as possible between 8 and 10. If the charging power is higher than the PV production, nothing will be injected to the grid. The main limitation for the moment is that any value you set will be applied every day for the whole year. Time series import should be available starting from PVsyst 8.1.0

Again, if you change any figure for the battery, it WILL impact your simulation. If you change the number of cells or the number of blocks or the number of racks, the battery characteristics will be impacted (voltage for the components in series, capacity for the components in parallel). The only issue I can see is the display of the number of UNITS in the grid storage window, which is not changed as it should when you change the number of blocks in the battery component. Now, if you have this values in your report (10*2 Units) but did not set 10 racks in series and 2 racks in parallel, please contact us at support@pvsyst.com with your project so we can have a better look at what's happening.

I think you misunderstood what I meant. You can any number of cells, modules and racks and it will be taken into account during the simulation. Only this specific figure displayed here is false. But that's only for display, so it won't impact your simulation.

The "number of elements" displayed might be misleading, as it should represent the total number of cells in your system, but it does not seem to take into account the number of blocks (or modules). This is definitively a bug, but as long as the total voltage and capacity are consistent with your design, the computation will be valid.

Hi, From the information you provided, this behavior does not seem normal indeed. The 1st graph looks ok, having 5.8% losses due to the grid limitation with 320kVa installed and 250kVa does not strike me as unusual. The fact is has been lowered to almost nothing in the second case is strange. I tried to reproduce your test case, but the results I obtain are correct. Please contact support@pvsyst.com and share your project so we can have a better look at what's happening.

Grid Storage Release note : New strategy of power shifting, from the diurnal PV production to a period offering a better tariff A new grid storage strategy is available : Power shifting. It allows for storing part of the produced energy during the day, then releasing it when the PV production is lower. This option is accessible in Storage => Power Shifting More details in the dedicated help page : https://www.pvsyst.com/help/project-design/grid-connected-system-definition/grid-systems-with-storage/power-shifting-storage.html This update also brings a few minor correction related to how the battery charger and inverter losses are computed. It may impact existing simulation results for all grid storage strategy. These changes should be especially visible in the following conditions : Battery charger / inverter is undersized (e.g : Charger power < PVpower-Grid limitation) Battery Charger / inverter power is largely oversized (e.g : Charger power >> PVpower-Grid limitation) Battery Charger / inverter efficiency is low NB: This new feature is likely to be updated in the future releases, so results are likely to change a little.

Compatibility rules between optimizers and inverters are implemented in PVsyst directly based on Huawei's requests. In this case, Huawei requested the maximum connected power to be limited to a certain DC/AC ratio. This is what is displayed in the message box: with only two MPPT input used, the maximum allowed DC/AC ratio is 1. Because you have a total connected STC power of 30.6kW, this configuration is not considered valid for Huawei. Huawei asked us to strictly enforce their rules, so there is no possibility to overstep this one. The only solution is to change your system somehow (configuring more strings, or slightly altering your inverter AC power or modules power so keep the DC/AC ratio below 1). Nb: Mixed orientation are only applied to different strings, not on different modules within a string. Since you can individually assign strings to each MPPT inputs with Huawei, the concept of mixed orientation is redundant and often misleading. In future releases, the mixed orientation option may not be possible anymore with Huawei, and you will have to separate your subarray into two, each with its own orientation.