Six PCS Checks to Increase Power Generation | How to Detect Abnormalities

Table of Contents

• PCS checks aimed at increasing power output should begin with anomalies in the power generation curve

• Check item 1: Verify the difference between power generation data and output per PCS unit

• Check item 2: Correlate shutdown history and alarm history by timestamp

• Check item 3: Check for power curtailment and plateaued power generation curves

• Check item 4: Check for input-side string mismatches and connection status

• Check item 5: Verify temperature rise, poor ventilation, and installation environment

• Check item 6: Manage recurrent anomalies using inspection records and location information

• Approach to distinguishing PCS abnormalities from soiling, shading, and weather factors

• Summary

When increasing power output, PCS checks should start with anomalies in the power generation curve

When you want to increase the output of a solar power system, the PCS is something you should always check alongside panel cleaning and weed control. The PCS is an important piece of equipment that converts the direct current electricity generated by solar panels into alternating current suitable for use and transmission. Even if the panels are receiving sufficient sunlight, power generation will not rise if the PCS has stopped, its output is being limited, or there are abnormalities on the input side or in the surrounding environment. If the panels look clean, the weeds are cut, and the weather is good but power output is low, inspecting the area around the PCS is indispensable.

For practitioners searching "how to increase power generation", it's important not to treat PCS abnormalities as mere equipment failures. PCS stoppages and alarms are obvious anomalies, but in reality multiple factors can lead to reduced power generation: short-duration stoppages, output plateauing, temperature rises, string mismatches on the input side, defects in connection points, poor ventilation, and reduced inspectability due to grass or accumulated debris. Viewing only the PCS unit won't reveal the cause; you need to check power generation data, on-site conditions, the input side, and the surrounding environment together.

In photovoltaic power generation, you cannot increase the amount of solar irradiance at the site itself. However, you can move closer to a state where the solar irradiance received is converted into electricity with as little waste as possible. The purpose of checking the PCS is to investigate whether power that should be generated is being lost at the conversion stage or in the connection routes. If generation does not recover after cleaning or weeding, if the generation curve becomes unnaturally flat, if on sunny days only some PCS units have low output, or if there are sudden drops during the daytime, you should suspect an abnormality related to the PCS.

A common cause of failure in PCS checks is judging solely by the on-site display and appearance. Even if the on-site inspection shows normal indicators, the unit may have repeatedly stopped for short periods during the daytime. Even without alarms, power generation can become capped due to output curtailment or rising temperatures. Even if there is no problem with the PCS itself, input-side strings, connection points, cables, surrounding vegetation, or poor ventilation can be affecting performance. Therefore, PCS checks should be conducted by narrowing down the time periods and scope of anomalies from generation data and cross-referencing the history with on-site conditions.

Also, because a PCS is electrical equipment, work that skips safety checks should be avoided. It is not appropriate for on-site personnel to force open the interior or touch connection points to make a judgment simply to try to increase power output. What operational staff should do first is organize the time of the power output decline, the affected PCS, alarm and shutdown history, exterior photos, surrounding environment, and the condition of the input side, and, if necessary, escalate to a specialized inspection. Below, we explain six items to check on the PCS to increase power output, structured around how to detect abnormalities.

Check Item 1: Verify the difference between power generation data and output per PCS unit

The first step in checking PCS is to view the power generation data on a per-PCS basis. If you only look at the total output for the entire plant, anomalies occurring in some PCS can be masked by the average. Even when the plant's total output doesn't appear to indicate a major problem, you may find that only certain PCS have low output, output drops only during specific time periods, or the generation curve differs compared with PCS under the same conditions. To increase power generation, you must first narrow down the anomalous range at the PCS unit level.

Comparing PCS units with the same orientation, the same tilt, a similar number of panels, and similar connection configurations makes it easier to detect anomalies. If you simply compare PCS with different conditions, you risk misidentifying normal differences as abnormalities. The purpose of the comparison is to identify PCS units that consistently have lower power output among units that should produce similar generation. If a unit is the only one performing lower than adjacent equipment or PCS under the same conditions, priority should be given to checking the PCS itself, its input side, connections, cables, and the surrounding environment.

The shape of the power generation curve is also important. If the morning ramp-up is slow, shadows on the east side or on the input side may be involved. If it falls off early in the evening, check for shadows on the west side. If the midday peak does not extend, possible causes include PCS output limits, temperature rise, differences between input-side strings, soiling on the panel surface, and output curtailment. If the power curve suddenly drops midway, cross-reference shutdown and alarm logs with the timestamps.

When comparing output differences at the PCS unit level, it is useful to use clear-sky (sunny) days as a baseline. On cloudy or rainy days, power generation can fluctuate widely due to cloud movement, making it difficult to determine whether differences between PCS units are caused by the weather or by the equipment. If a clear difference appears between PCS units under the same conditions on a clear-sky day, it is more likely to be due to on-site causes. In particular, if the same PCS is consistently lower each time or if dips occur at the same time of day, the anomaly is reproducible and should be prioritized for inspection.

If a discrepancy in output is found, it is important not to immediately assume equipment failure. Even when output is low at the PCS level, factors other than the PCS can be involved, such as panel soiling on the input side, shading from weeds or trees, poor string connections, cable damage, ambient temperature, and poor ventilation. Generation data do not definitively identify the cause; they are an entry point to narrow the scope of what should be checked. By identifying the PCS suspected of abnormality and inspecting the surrounding equipment and the input side as well, it becomes easier to choose measures that will improve power generation.

Check Item 2: Cross-check stop history and alarm history by timestamp

An important part of detecting abnormalities in the PCS is checking the stop history and the alarm history. If the PCS stops even for a short time, the power generation during that period will decrease. In particular, if a stop occurs during the daytime when solar irradiance is strong, even a short stop can have a large impact on power generation. A stop that is not noticeable when looking only at monthly generation can appear as a sudden drop when viewing the generation curve by time of day.

When reviewing stop history, confirm which PCS stopped, when it stopped, and for how long. If multiple PCS units stopped simultaneously, the grid side, output curtailment, external conditions, or common equipment may be involved. If only a specific PCS stopped, check the PCS itself, the input side, the connection points, and the surrounding environment. Whether the stoppage was a single occurrence or repeats multiple times during the daytime will also change what needs to be checked.

Alarm history should also be cross-checked with power generation data and timestamps. If the time of the drop in the generation curve matches the time an alarm occurred, it is likely that a PCS-side fault is related to the decrease in power generation. On the other hand, if power generation has decreased but there is no alarm history, you need to check for soiling, shading, string imbalance on the input side, output curtailment, temperature conditions, measurement issues, and so on. Rather than judging the system to be normal because no alarms have been issued, it is important to view power generation data together with the history.

When checking the cause of shutdowns or alarms, also verify the weather and on-site conditions at the time of occurrence. If anomalies tend to appear after rain, humidity, water ingress, or the environment around connection points may be involved. If shutdowns or alarms are more likely during periods of high ambient temperature, check the temperature conditions and for inadequate ventilation. If grass or accumulated debris is obstructing ventilation around the PCS, the equipment may be more prone to overheating. Because the cause cannot be determined by looking at the shutdown history alone, it is necessary to cross-check with the on-site conditions.

When checking PCS shutdown and alarm histories, pay attention to safety. If reviewing the history indicates that internal inspection or electrical testing is required, responses based on appropriate knowledge and procedures are necessary. Rather than having on-site personnel forcibly open or touch the interior to make a judgment, organize which PCS is showing an anomaly, the time of occurrence, changes in power generation, alarm details, site photos, and the surrounding environment, and, if necessary, escalate to professional inspections. When checking PCS to increase power generation, it is important both to identify abnormalities and to safely isolate their cause.

Checklist item 3: Confirm power curtailment and plateauing of the power generation curve

On sunny days, if power generation does not increase as much as expected, you need to check for PCS output curtailment or output capping. If the top of the generation curve is flat, it may be that, despite sufficient solar irradiance, the system is not producing above a certain level. However, a flat generation curve does not necessarily mean that PCS output curtailment is the only cause. Equipment capacity limits, temperature rise, input-side restrictions, panel soiling, shading, or measurement anomalies can produce a similar shape.

If output curtailment occurs, there may be a history recorded in the PCS or monitoring data. Check whether the time periods when generation output plateaus match the history of curtailment or limitations. If multiple PCS simultaneously plateau in the same way, restrictions affecting the entire plant are suspected. If only a specific PCS plateaus, check that PCS’s settings, operating condition, input side, temperature environment, etc.

When examining generation curves, it is also necessary to isolate the effects of weather. On cloudy or thin-cloud days, the generation curve may not be smooth and can fluctuate irregularly. To determine output curtailment or PCS anomalies, use data from clear, sunny days as much as possible. Comparing PCS units within the same plant and checking whether only some units are hitting a ceiling under similar solar irradiance conditions makes it easier to narrow down the scope of anomalies.

The cause of a plateau is not always the PCS; it can also be on the input side. For example, if some of the input strings are low, if the panel surface is dirty, if weeds or tree shadows partially shade the panels, or if there are faults at connection points, the power entering the PCS itself will be insufficient. In such cases, even if the PCS is operating normally, the output will not increase. When the generation curve fails to rise, it is important to check the generation status on the input side as well as the output side of the PCS.

Do not overlook output reductions caused by temperature. On clear summer days, while solar irradiance is strong, panel temperatures and temperatures around the PCS can rise, making it harder for output to increase. If ventilation around the PCS is poor, heat tends to be trapped by grass or accumulated debris, or equipment is prone to becoming hot due to direct sunlight or surrounding environmental influences, power generation can be affected. When you see a flattened generation curve, checking output curtailment, insufficient input, and thermal conditions together is an effective way to detect anomalies.

Check item 4: Verify the input-side string difference and connection status

If a PCS shows low power generation, you need to check not only the PCS itself but also for string mismatches on the input side. The electricity generated by the solar panels is fed into the PCS through multiple strings. Therefore, if part of the input side is affected by soiling, shading, poor connections, cable damage, or panel abnormalities, the PCS output may appear low. There are cases that look like a PCS fault but are actually problems on the input side.

When checking for string-level abnormalities, compare strings that are under the same conditions. If you simply compare strings with different numbers of panels, orientations, tilts, shading conditions, or connection configurations, you may misidentify normal differences as abnormalities. Check whether any string is consistently lower compared to adjacent rows or strings with the same orientation. If only a specific string is low, possible causes include soiling, partial shading, poor connections, cable damage, or panel defects.

Also pay attention to how string-to-string differences manifest. If a string is consistently lower than its surroundings even on sunny days, dirt or connection problems are suspected. If it is lower only in the morning and evening, check for shading effects. If abnormalities tend to appear after rain, moisture ingress or the condition of connection points may be involved. If it becomes unstable during high-temperature periods, poor contact or the thermal environment are also possible causes. Combining the power output waveform with on-site conditions makes it easier to narrow down the cause.

The condition of connection points and cables is also important. Loose terminals, poor contact, damaged cable sheaths, moisture ingress, damage caused by animals, damage during grass-cutting operations, and deterioration due to aging can all lead to input-side generation losses. These issues can be difficult to detect from appearance alone. Narrowing down abnormal ranges using power generation data and cross-checking with on-site photos, the time of occurrence, weather, and the surrounding environment makes it easier to prioritize inspections.

Even when checking the input side, safety must be the top priority. Just because you want to increase power output, on-site personnel should avoid forcibly touching connection points or internal components to make judgments. First, organize the PCS suspected of abnormality, the relevant string, the time of occurrence, changes in power output, on-site photos, and the surrounding environment. If necessary, escalate to a professional inspection so that the cause can be identified more easily while maintaining safety.

Checklist Item 5: Check for Temperature Rise, Poor Ventilation, and Installation Environment

Things that are often overlooked during PCS checks are temperature rise, poor ventilation, and the installation environment. A PCS is equipment that converts electric power, and stable operation requires an appropriate surrounding environment. Conditions such as overgrown vegetation around the unit, restricted airflow, accumulation of dust or debris, susceptibility to rainwater or sediment, or placement in locations that are difficult to inspect can lead to reduced power generation and delayed detection of abnormalities.

Temperature conditions are an important factor that affect power generation. While solar power systems tend to generate more power with stronger solar irradiance, if panel temperatures or the temperature around the PCS rise, output may be suppressed. If on clear summer days generation does not increase as expected, the midday peak hits a ceiling, or alarms or shutdowns tend to occur during periods of high ambient temperature, it is necessary to check the temperature environment and ventilation conditions.

Also check for grass and obstacles around the PCS. If grass has grown up around the equipment, it not only makes it harder to inspect the exterior and displays but can also obstruct ventilation. If there is debris accumulated around the equipment, it can likewise affect heat dissipation and inspectability. When checking the PCS to increase power generation, it is important to confirm not only the equipment itself but also that the surrounding area is easy to see, easy to access, and allows airflow.

The effects of rainwater and sediment cannot be overlooked. If conditions such as puddles forming around the PCS, sediment flowing in, moisture becoming trapped, or walkways becoming muddy exist, inspection work may be delayed and connections or surrounding equipment may be affected. If abnormalities tend to occur after rain, check not only the history of the PCS unit but also the surrounding drainage and topography. If the same abnormalities recur in the same location even after cleaning or weeding, environmental factors should be suspected.

Checking the installation environment may not immediately be reflected as an increase in power output. However, over the long term it contributes to early detection of shutdowns, suppression of temperature rises, easier inspection, and prevention of overlooking abnormalities at connection points. To make PCS anomalies easier to detect, it is important to create an environment that allows the equipment to operate stably and to maintain a condition where anomalies can be checked immediately.

Checklist Item 6: Manage anomalies prone to recurrence using inspection records and location information

Keeping inspection records is essential to turning PCS checks into improved power generation. Recording PCS units that stopped or issued alarms, time periods with low output, strings suspected of input-side abnormalities, locations with poor ventilation, equipment areas where weeds had overgrown, and places where water had pooled will make future checks faster. Without records, even if the same abnormalities recur you cannot learn their causes and will have to investigate from scratch each time.

What should be recorded are the PCS location, equipment number, time of occurrence, change in power output, details of any alarms or shutdowns, on-site photos, the surrounding environment, the response taken, and whether re-confirmation is necessary. In large power plants, similar equipment and facilities are often lined up, so it can be difficult to identify the location from photos alone. Recording the equipment number together with location information makes it easier for field personnel, managers, inspection personnel, and repair personnel to confirm the same location.

It is also important to correlate power generation data with on-site records. If the time when generation dropped matches the PCS shutdown history, inspections of the equipment take priority. If only a specific PCS shows low output even on sunny days, focus on its input side and the surrounding environment. If anomalies occur only on hot days, records of ventilation and nearby vegetation height are helpful. If anomalies appear after rain, records of puddles, soil or debris, moisture, and the areas around connections provide clues for identifying the cause.

Inspection records also provide input for prioritizing measures to improve power generation. If you can identify trends—such as the same PCS shutting down each time, grass growing in the same spot, the same string showing low output, or abnormalities occurring in the same area after rain—you can proactively check before the problem becomes larger. Rather than responding after a large drop in power output, understanding the conditions that tend to cause drops and conducting earlier inspections leads to operations that reduce losses.

Also, recording the results after countermeasures is important. Verify whether stoppages decreased after improving ventilation, whether the output discrepancy improved after inspections on the input side, and whether mowing the grass improved the temperature environment and the ease of inspection. Countermeasures that show clear effects should be incorporated into standard operations going forward, and if effects are not evident, suspect other causes. PCS checks are important not only for detecting abnormalities but also for using records to guide operations that reduce recurrence.

Approach to Distinguishing PCS Anomalies from Dirt, Shadows, and Weather Factors

When checking the PCS, it is important not to confuse PCS faults with dirt, shading, or weather-related factors. Looking only at the result of low power generation can make it appear as if there is a problem with the PCS. However, in reality the PCS output may only look low because of soiling on the panel surface, shading from weeds or trees, bad weather, or string abnormalities on the input side. To increase power generation, you should avoid assuming a single cause and instead isolate each potential cause in sequence.

First, check the weather and irradiance conditions. During periods with frequent clouds or rain, generation will be low even if the PCS is operating normally. If the entire plant shows a similarly reduced output, the irradiance conditions are likely the main factor. On the other hand, if only some PCS units within the same plant are low, or there is a clear difference compared with PCS under the same conditions, suspect on-site factors such as the PCS unit itself, the input side, shading, or soiling. Comparing sunny days with each other is the basic approach for isolating the issue.

Next, check for dirt and shading. Dirt on the lower edge of the panel surface, bird droppings, fallen leaves, or dust can reduce the power entering the PCS. If production is low only in the morning, check for shading on the east side; if only in the evening, check for shading on the west side. If you inspect the site at noon and, seeing no shadows, conclude there is no problem, you may miss shadows present in the morning or evening. It is important to confirm whether a decrease in generation at the PCS unit is caused by the panel-side environment on the input side.

A PCS fault is suspected when the time of a drop in the power generation curve matches shutdown history or alarm history, when the same PCS repeatedly shuts down, when it becomes unstable during periods of high temperature, or when it is consistently lower than PCS units under the same conditions. However, even in these cases, do not immediately conclude an internal fault—check the input side and the surrounding environment as well. By examining the PCS unit itself, the input side, the output side, and the surrounding environment separately, you can reduce the likelihood of misidentifying the cause.

What is required at the end of the fault isolation process is verifying power generation after countermeasures. After carrying out cleaning, weed control, ventilation improvements, maintenance of the surrounding environment, specialized inspections, and so on, check how the power output has changed. If it has improved, the measures were likely effective; if it has not, look for another cause. Improving power output is not a task of determining the cause in a single step, but a process of increasing accuracy by linking data, on-site findings, historical records, and the results of the measures.

Summary

When checking the PCS to increase power output, it is important to sequentially check generation data, shutdown history, alarm history, output curtailment, differences between input-side strings, temperature conditions, ventilation, and inspection records. In solar power generation, you cannot increase the amount of solar irradiance itself at the site. However, you can improve generation by bringing the system closer to a state that converts the received irradiance into electricity without waste. The PCS is a critical device responsible for that conversion, and any abnormalities or problems in the operating environment can lead to reduced power output.

To detect PCS abnormalities, it is first important to look at the power generation data for each PCS unit. Check whether any unit is producing less than other PCS units under the same conditions, and whether the generation curve shows any sudden drops or plateaus. Next, correlate shutdown logs and alarm histories with the times of the power drops. Also check for output curtailment, differences among input-side strings, connections and cables, temperature rises, poor ventilation, surrounding vegetation, and drainage conditions. By inspecting not only the PCS unit itself but also the input side and the surrounding environment, you can reduce the likelihood of overlooking abnormalities.

Also, safety must be the top priority when checking the PCS. Just because you want to increase power output, on-site personnel should avoid forcefully opening the interior or touching connection points to make a judgment. First, organize the PCS suspected of being abnormal, the time of occurrence, changes in power generation, the history, on-site photos, and the surrounding environment, and, if necessary, arrange for specialized inspection. Safely isolating the cause is the prerequisite for improving power generation.

In particularly large power plants, a system for accurately sharing the locations where PCS abnormalities occur is important. If inspection photos are saved together with location information for PCS units that stop frequently, PCS units that show output discrepancies, areas with poor ventilation, equipment surroundings where grass tends to grow, places where water accumulates, and ranges where input-side abnormalities are suspected, stakeholders can more easily confirm the same location. By combining power generation data with on-site location information, it becomes easier to explain the prioritization of inspections and repairs and to streamline recurrence checks in subsequent visits.

If you want to continue PCS inspections to increase power output based on field data, using LRTK can also be effective. As an iPhone-mounted, high-precision GNSS positioning device, LRTK is useful for recording—with high-accuracy location information—the locations of PCS within a solar power plant, equipment showing abnormalities, input-side inspection points, areas with poor ventilation, equipment surroundings prone to grass overgrowth, areas with poor drainage, and on-site photos. By saving PCS inspection results with location information, it becomes easier to pursue power output improvements based on field data rather than intuition.