5 steps to configure modules and PCS in PVsyst

In power generation simulations for photovoltaic plants, not only meteorological data, azimuth, and tilt angle but also the settings of the module and PCS affect the results. A common point of confusion when using PVsyst is not simply selecting equipment but verifying that the chosen combination of module and PCS falls within reasonable ranges for voltage, current, capacity ratio, temperature conditions, and operating conditions. In this article, we organize the workflow that practitioners should follow when configuring modules and PCS in PVsyst into five steps.

Table of Contents

• Step 1 モジュールとPCSの仕様書を先に整理する

• Step 2 モジュール情報を選択し電気特性を確認する

• Step 3 PCS情報を選択し入力条件を確認する

• Step 4 直列枚数と並列回路数を決める

• Step 5 エラーや警告を確認して設定を調整する

• PVsyst設定で見落としやすい実務上の注意点

• まとめ モジュールとPCS設定は発電量評価の前提条件になる

Step 1: First organize the specification documents for the module and PCS

Before configuring modules and the PCS in PVsyst, the first thing you should do is organize the specifications of the equipment you plan to use. If you start working directly in the simulation software and select equipment as you go, it’s easy to become uncertain when multiple candidates with similar model numbers or close ratings appear. In practice, the equipment information you should use may change between the early-stage conceptual design, the provisional design at the estimating stage, the final design before construction, and the post-completion reevaluation. For that reason, it’s important to clarify which stage of the study this simulation represents before opening PVsyst.

For modules, organize the nominal maximum output, open-circuit voltage, short-circuit current, maximum power operating voltage, maximum power operating current, temperature coefficient, module dimensions, number of modules, installation angle, and installation orientation. If you configure based only on the nominal maximum output, verification of string voltage and PCS input current may be insufficient. In solar power generation systems, module voltage varies with temperature. On the low-temperature side the open-circuit voltage becomes higher, making the relationship with the PCS's absolute maximum input voltage and the module's maximum system voltage important. Conversely, on the high-temperature side the operating voltage drops, so it is necessary to confirm compatibility with the PCS's MPPT voltage range.

For PCS, organize the rated AC output, maximum DC input voltage, MPPT voltage range, maximum input current, number of input circuits, number of MPPT inputs, conversion efficiency, and control conditions during overloading. In domestic practice the term PCS is often used, but in PVsyst it is mainly treated as an inverter. What is important here is to understand not only the rated output of the PCS but also the DC-side acceptance conditions. If you decide module capacity by looking only at PCS capacity, it may appear valid in energy yield calculations, but in reality confirmation of input current and voltage range can be insufficient.

When organizing specifications, attention must also be paid to units. Voltage has different meanings on the DC side and the AC side, and output is typically treated as DC capacity on the module side, while on the PCS side it is treated as AC capacity. Treating DC capacity and AC capacity as the same thing can lead to misinterpretation of the DC/AC ratio. Also, a module’s output is the value under standard test conditions and will not always be obtained under local temperature and irradiance conditions. Since PVsyst calculates energy production based on input conditions, it is essential to align the assumptions about equipment information.

In practice, a specification sheet may list multiple values. When nominal values, tolerances, values for different temperature conditions, values under certification conditions, and the like are mixed, you must decide which values to use for simulation. As a rule, check that the equipment data registered in PVsyst and the key values in the specification at hand do not differ substantially. Even if they do not match exactly, values may vary slightly due to specification revisions of the same model or differences in shipping dates. In such cases, recording which specification you used as the basis will make it easier to explain later.

When using PVsyst, it is more important to adopt the practice of cross-checking pre-organized specifications with the values entered into the software than simply memorizing on-screen input operations. Simulation results are built up from the accumulation of input conditions. If the settings for the modules and PCS remain ambiguous, the appearance of annual energy generation, loss breakdowns, output clipping due to overloading, temperature losses, and so on will change. Therefore, in the initial steps it is desirable to organize the equipment specifications, the design stage, the reference documents to be used, and the assumed plant capacity as a single premise before proceeding to the settings in PVsyst.

Step 2 Select the module information and check the electrical characteristics

Next, set the module information in PVsyst. In the typical workflow, on the system settings screen you select the photovoltaic module and specify a model that is close to the planned installation or has equivalent electrical characteristics. What you should be careful about here is not to treat module selection as merely choosing an equipment name. What matters for energy yield simulation is whether the electrical characteristics of the selected module match the actual design conditions.

When you select a module, first check its nominal maximum power. Verify that the module capacity listed in the design documents and layout drawings matches the module capacity you selected in PVsyst. For example, if the plan assumes high‑output modules but you choose a similar yet lower‑output module in PVsyst, the total DC capacity will be off. Conversely, selecting a higher‑output module can make the estimated energy production look overstated. Even if the per‑module difference is small, it can add up to a large discrepancy for the entire plant, so pay special attention to this.

Next, check the open-circuit voltage and the maximum power operating voltage. The open-circuit voltage is important in relation to the PCS's absolute maximum input voltage. Module voltage, in particular, rises in cold regions and under low-temperature winter conditions. PVsyst evaluates the voltage range based on the design temperature, but if the underlying assumptions—such as the module temperature coefficient and the design temperature—do not match reality, the evaluation of the maximum voltage under low-temperature conditions may be inaccurate. The maximum power operating voltage is important to determine whether the string voltage will fall within the range in which the PCS operates efficiently. You need to know this value before deciding the number of modules in series.

Short-circuit current and maximum operating output current should also be checked. The PCS has an upper limit on input current, and when connecting multiple strings you must ensure the current does not exceed that limit. The higher the module current, the more the number of parallel circuits that can be connected to the same PCS input may be restricted. If input conditions in PVsyst are not set correctly, warnings or errors may appear, but the absence of a warning does not mean field verification is unnecessary. It is important to cross-check against the design drawings, the specifications of junction boxes and combiner boxes, and the PCS input circuit configuration.

You also need to check the temperature coefficients. Module output generally decreases as temperature rises. In PVsyst, temperature conditions are reflected in energy production and losses, so if the temperature coefficients differ from the actual equipment specifications, the annual energy yield assessment may change. Temperature coefficients are specified for maximum power, open-circuit voltage, short-circuit current, and so on. In practice, it is particularly important to verify the power temperature coefficient and the voltage temperature coefficient. These relate not only to energy production but also to voltage rise at low temperatures and to operating voltage drop at high temperatures.

After setting the module information, check the relationship between the total number of modules and the DC capacity. In PVsyst, the overall DC capacity of the system is calculated from the selected module’s capacity and the number of modules. Verify that the number of modules on the design drawings, the counts for each placement area, and the array configuration all match. If these quantities do not match here, even if the later PCS settings and string configurations are correct, the assumptions for energy production will be off.

Approximate data may be used when selecting modules. If the official model is not yet decided in the early planning stage, estimates may be made using generic module data in the same power range. However, this should be treated only as a rough evaluation; when used for formal design assessment or external presentation, it is desirable to replace it with the finalized specifications and recalculate. When using PVsyst, it is important not to confuse provisional settings with confirmed settings. Make the module conditions used clear in the file name or memo field so that they are easier to identify when reviewing later.

Step 3 Select PCS information and check input conditions

After setting the module information, next configure the PCS. The PCS is the device that converts the generated DC power into AC, and in simulations it relates to conversion efficiency, input voltage range, input current, rated output, and behavior under overloading. When selecting a PCS in PVsyst, check not only the AC rated capacity but also the DC-side acceptance conditions.

The first thing to check is the PCS's rated AC output. The total PCS capacity of the installation is an important value that determines the plant's AC capacity. The ratio of the modules' DC capacity to the PCS's AC capacity affects estimates of energy production and potential output curtailment. Designs that make the DC capacity larger than the PCS capacity are common, but if the ratio is too high the PCS may have its output curtailed during periods of strong solar irradiance. In PVsyst, losses from such curtailment are reflected in the results, so PCS capacity should be set carefully.

Next, check the maximum DC input voltage. When modules are connected in series, the string voltage is the sum of the voltages of each module. Because the open-circuit voltage rises at low temperatures, too many modules in series can cause the PCS’s absolute maximum input voltage to be exceeded. In PVsyst, you can verify the validity of the voltage based on the selected module, the number of modules in series, and the design temperature. If an error related to safety limits appears here, you should reduce the number of modules in series, review the PCS input conditions, or recheck the design temperature.

The PCS's MPPT voltage range is also important. Even if you only verify that the maximum input voltage is not exceeded, if the operating voltage during actual use does not fall within the range where the PCS can properly track, it will affect power generation. In particular, because module operating voltage decreases at high temperatures, having too few modules in series can create conditions where the PCS cannot operate efficiently. In PVsyst, the number of modules in series is adjusted while checking that the voltage stays within the appropriate range.

Maximum input current is another item that can be easily overlooked. The current flowing into the PCS input is determined by the module current and the number of parallel circuits. When combining multiple strings into the same input, you must ensure the current does not exceed the PCS's limit. In PVsyst you can configure the connection layout, but you need to verify that it matches the actual switchboard configuration and the allocation of input circuits. If the PCS has multiple MPPT inputs, the number of strings connected to each input and differences in their orientation can affect the simulation results.

The efficiency characteristics of the PCS also affect energy yield. A PCS does not always operate at a constant efficiency; its conversion efficiency changes depending on input power and voltage conditions. In PVsyst, conversion losses are calculated based on the efficiency characteristics of the selected PCS data. Therefore, if the efficiency characteristics of the chosen PCS data differ significantly from the actual equipment, there may be a discrepancy in the annual energy yield. During the planning stage a PCS of similar capacity may be provisionally assigned, but in the final design it is important to review and adjust the settings by cross-checking with the specifications.

Also pay attention to the configured number of PCS units. When using multiple PCS units for the entire power plant, verify that the number of modules connected per unit, the DC capacity, and the number of input circuits match the design. In PVsyst, you can model PCS as multiple units to build up the system’s total capacity. However, simply matching the total PCS capacity can result in per-unit connection conditions that differ from the actual setup. For example, if only some PCS have different numbers of connected modules, or if array orientations differ due to terrain, more careful settings—such as separating subarrays—may be necessary.

When configuring the PCS, you should pay attention not only to the expected energy production but also to how explainable the design is. When using PVsyst results in external documents or internal reviews, it is important to be able to explain why that PCS capacity was chosen, whether the ratio to module capacity is reasonable, and to what extent overloading imposes limitations. PVsyst’s result screens show loss items, but if you do not understand what they mean you may draw conclusions based solely on the numbers. PCS configuration is an important step that connects generation assessment and equipment design.

Step 4 Determine the number of modules in series and the number of parallel strings

After configuring the module and PCS equipment information, next decide the number of modules in series and the number of parallel circuits. This is a part of PVsyst that users particularly find confusing. The number of modules in series determines the string voltage, and the number of parallel circuits determines the input current and the total number of modules. In other words, this configuration must simultaneously satisfy the voltage, current, capacity, module count, and PCS input conditions.

When determining the number of modules in series, first confirm that the open-circuit voltage at low temperature does not exceed the PCS’s absolute maximum input voltage. Because photovoltaic modules increase in voltage as temperature drops, what appears acceptable under standard test conditions may exceed the limit under winter low-temperature conditions. PVsyst allows checks that take the design temperature into account, but it is also important to decide how to set the site’s minimum temperature or the temperature conditions to be adopted as the design basis. In cold regions, mountainous areas, and snowy regions, checks should be carried out with an adequate margin.

On the other hand, if the number of modules in series is too low, the operating voltage at high temperatures may fall below the PCS MPPT voltage range. Module voltage decreases during hot summer conditions. Even when irradiance is sufficient, if the voltage conditions are not met the PCS may not operate as expected. Therefore, having too many or too few modules in series can both cause problems. Adjust the series count while checking the voltage-range display and warnings in PVsyst so that it stays within a reasonable range throughout the year.

When determining the number of parallel circuits, verify the PCS's maximum input current and the input circuit configuration. If module currents are large, increasing the number of parallels will bring the PCS input side closer to its current limit. It is important to separately confirm the limit for each input circuit, for each MPPT input, and for the entire PCS. Even if junction boxes or combiner boxes are consolidated on the design drawings, if the input configuration in PVsyst does not properly reflect that, the actual connection conditions and the simulation conditions will diverge.

When you decide the number of modules in series and the number of parallel circuits, the total number of modules is determined. At this point, check whether it matches the planned layout quantity. For example, adjusting the number of modules in series can result in a total count that no longer matches the design drawings. Even if the configuration is electrically valid in PVsyst, problems can occur in the actual layout—such as leftover modules, mismatched numbers per row, or an inability to implement the same string configuration due to terrain or obstacles. It is important to verify electrical validity and on-site layout feasibility separately.

If there are multiple orientations or tilts, handle string configuration even more carefully. Mixing strings with significantly different irradiance conditions on the same PCS or the same MPPT input can affect energy production. In PVsyst, defining separate sub-arrays makes it easier to account for different orientations and tilts. Grouping everything under a single representative condition simplifies setup, but may not adequately represent actual generation behavior. Determine how far to separate them based on the complexity of the design.

Also, the concept of oversizing is related to the number of modules connected in series and the number of parallel strings. Making the DC-side module capacity larger than the AC capacity of the PCS makes it easier to use the PCS effectively even during times or seasons of low solar irradiance, but during periods of strong irradiance some generation may be limited by the PCS output limit. In PVsyst you can check the losses caused by this limitation. Oversizing is not simply a bad thing; it should be evaluated as a balance among energy generation, equipment utilization, grid conditions, and design policy.

In this procedure, it is important not to make eliminating errors in PVsyst the sole objective. A configuration with no errors is meaningless if it does not match the actual design drawings. Conversely, when warning messages appear, their content should be checked by separating items that relate to safety limits from those that are design considerations. What is important is that the number of modules in series, the number of parallel circuits, the number of PCS units, the total number of modules, and the array divisions are consistent as a single design.

Step 5 Check for errors and warnings and adjust settings

After configuring the modules, PCS, number of modules in series, and number of parallel strings, check the errors and warnings shown in PVsyst. The items displayed here are not merely indications of simple user mistakes. They include important information affecting the validity of the design, such as voltage range, input current, capacity ratio, string configuration, and the combination with the PCS. When using PVsyst, you should not change values merely to clear warnings; it is necessary to understand why a warning is appearing.

If you receive warnings or errors about voltage at low temperatures, the number of modules in series may be too high. This means that, as the module open-circuit voltage reflects temperature conditions, there is insufficient margin relative to the PCS's absolute maximum input voltage or the module's maximum system voltage. In this case, the basic response is to reduce the number of modules in series. However, reducing the number of modules in series lowers the operating voltage at high temperatures, so you must recheck whether it falls within the PCS's MPPT voltage range. Adjusting based on only one condition can cause problems under other conditions.

If a warning about voltage at high temperatures appears, the number of modules in series may be too low. As module temperature rises, the operating voltage decreases and may fall below the PCS's MPPT voltage range. In this case, consider increasing the number of modules in series. However, increasing the series count raises the open-circuit voltage at low temperatures, so recheck its relationship with the absolute maximum input voltage. Adjustments in PVsyst should always be made while considering both the low-temperature and high-temperature sides.

If a warning about input current appears, review the number of parallel circuits and the allocation of PCS inputs. If module currents are large, combining multiple strings can exceed the PCS input current limit. If there are insufficient input circuits, it may be necessary to reconsider the number of PCS units and the circuit partitioning. In practice, it is important to verify not only the settings in PVsyst but also the actual junction boxes, combiner boxes, wiring plans, and protection device conditions.

If there are warnings or cautionary notices regarding the capacity ratio, check the balance between DC capacity and AC capacity. If the DC capacity is large relative to the PCS capacity, there will be periods when power generation increases, but losses due to output clipping are also more likely to occur. In PVsyst, you can confirm this impact in the loss diagram and result tables. The capacity ratio is not simply “the higher the better” or “the lower the better.” The appropriate range depends on the plant’s purpose, grid interconnection conditions, available installation area, equipment configuration, and the assumptions used in the economic evaluation.

After checking errors and warnings, review the breakdown of losses in the simulation results. Losses related to module and PCS settings include temperature-related losses, PCS conversion losses, losses due to PCS output limits, and mismatch losses. If these values are larger than expected, the configured conditions may not match the actual situation. For example, if losses from PCS output limits are larger than expected, this may indicate that the DC capacity is excessive, the PCS capacity is too small, or the specified irradiance or orientation conditions differ from those assumed.

When making adjustments, it is also important not to change too many conditions at once. If you change the module type, PCS capacity, number of modules in series, number of modules in parallel, tilt angle, and azimuth all at the same time, it becomes difficult to determine which change affected the results. In practice, you create a baseline case first, and then examine cases that are easy to compare—such as a case with a different number of series modules, a case with a different PCS capacity, and a case with a different capacity ratio. To use PVsyst results for design decisions, it is important not only to rely on a single result but also to be able to explain the differences caused by changes in conditions.

Ultimately, we will resolve errors related to safety limits and reach a state where we can explain the meaning of warning indications and how they are handled in the design. However, this is not the end. Power generation simulations involve many other factors, such as shading, terrain, wiring losses, soiling, temperature conditions, operational outages, and output control. Among these, module and PCS settings form the foundational part of the system configuration. By carefully checking this area, subsequent detailed settings and explanations of results will be more stable.

Practical cautions in PVsyst settings that are easy to overlook

When setting modules and PCS in PVsyst, there are practical points to watch for that are easy to overlook if you only follow the operation steps. The main issue is a mismatch between the design drawings and the simulation conditions. Even if the total capacity lines up neatly in PVsyst, the actual layout may have different module counts by area. Due to terrain, roads, drainage facilities, existing structures, and spacing requirements, it may not be possible to configure every string with the same number of modules. In such cases, you need to decide whether to summarize them with a representative configuration or to separate them as sub-arrays.

Next, there is a problem where provisional settings remain as the final settings. In the early planning stages, the official module or PCS may not be decided. At that stage, it can be practical to make rough estimates using generic data with similar performance. However, if the equipment is later finalized but the settings in PVsyst are not updated before documentation is prepared, the estimated energy production and loss breakdown will diverge from the actual design. When provisional settings are used, it is necessary to indicate this in the file name or notes and to update them when the decisions are finalized.

How the PCS's MPPT inputs are handled is also a point to be careful about. If you configure arrays with multiple orientations and tilts to be connected to the same MPPT input, it can become difficult to reflect the actual generation characteristics. In particular, for east-west layouts, staggered arrangements, and installations with multiple tilts following the terrain, the times of peak solar irradiance and the voltage conditions differ by area. When making simplified settings in PVsyst, you must be aware of how much that simplification will affect the results.

Module temperature conditions are another item that is easy to overlook. In energy yield assessments, not only the ambient air temperature from meteorological data but also the heat-dissipation conditions determined by the module’s mounting configuration have an impact. Whether the modules are rooftop-mounted or ground-mounted, the racking height, and ventilation conditions all change how quickly the module temperature rises. If module temperature is estimated higher, temperature-related losses increase; if estimated lower, the energy yield may be reported as higher. Even if the module and PCS settings are correct, if the assumed temperature conditions do not match the site, the results can be misinterpreted.

The relationship with wiring losses is also important. Once the positions of the modules and the PCS are determined, the wiring routes, distances, and voltage-drop conditions on the DC and AC sides become clear. In PVsyst you can also set wiring losses, but if you enter only standard values without considering the positional relationship between the modules and the PCS, you may not sufficiently reflect site conditions. This is especially true for large-scale power plants, where wiring losses vary depending on the PCS placement and the collection method. Even if equipment settings and wiring settings are separate items, in practice they need to be checked in conjunction.

When checking the results, it's important not to judge only by the annual energy production. Even if the annual production is close to the estimate, if there are anomalous items in the loss breakdown the settings may be problematic. For example, if the PCS output limit is too large, temperature losses are greater than expected, or mismatch losses are extremely high, you should review the equipment settings, string configuration, orientation settings, or shading settings. When using PVsyst, you need the ability to read the intermediate loss structure as well as the final output value.

When explaining the results to internal staff or stakeholders, it is smoother if you organize the rationale for the module and PCS settings. Be prepared to explain which specification sheets were used, how many modules there are, how many PCS units, the ratio between DC capacity and AC capacity, and how the number of series-connected modules and the number of parallel circuits were determined. Simply handing over PVsyst screens or reports may not allow the recipient to judge the validity of the settings. In practice, it is very important to explain how the design conditions correspond to the simulation conditions.

Summary: Module and PCS settings are prerequisites for power generation assessment

Setting modules and the PCS in PVsyst is not simply a matter of selecting equipment on the screen. It is a process of combining the module’s output, voltage, current, temperature coefficients; the PCS’s input range, input current, rated output, and conversion efficiency; and the number of modules in series and the number of parallel circuits, to create the conditions that make the installation a viable system. If this premise is off, evaluations of annual energy production, loss breakdown, output limitations, and temperature effects will change.

In practice, start by organizing the specifications, verify the module information and the PCS information, and then determine the number of modules in series and the number of parallel strings. Finally, adjust the settings while reviewing errors, warnings, and the loss breakdown in PVsyst. Carefully following these five steps improves the clarity of the simulation results and makes them easier to use for design decisions.

What's particularly important is not to take PVsyst results at face value, but to verify that the input conditions match the site design. If the number of modules, number of PCS units, DC/AC ratio, string configuration, differences in azimuth or tilt, temperature conditions, and wiring conditions are not consistent, even a superficially neat report will have reduced practical reliability. For energy yield simulations, it is important not only to present the numerical results but also to be able to explain the assumptions that led to those numbers.

When you are not yet familiar with using PVsyst, you may be unsure how detailed your settings should be. In that case, first focus on checking the module and PCS specifications, the number of modules in series, the number of parallel circuits, the DC/AC ratio, and any warnings. These form the backbone of the energy yield assessment and are items that, if modified later, can easily affect the overall results.

In planning a solar power plant, linking desk-based simulations with on-site conditions is indispensable. Not only carefully configuring modules and the PCS, but also considering terrain, shading, layout, construction constraints, and ease of operation and maintenance leads to an energy yield assessment that more closely reflects reality. It is important to improve the planning accuracy of a solar power plant by aligning on-site data, design drawings, equipment specifications, and simulation conditions.