How maximum power point tracking (MPPT) is used in utility-scale solar design

What is maximum power point tracking MPPT? 

Maximum Power Point Tracking definition - Maximum Power Point Tracking (MPPT) is a technique used in photovoltaic (PV) systems to maximize the inverter output. It does this by continuously adjusting the operating conditions, ensuring it operates at the point on its voltage-current curve where it produces the maximum power.

One of the biggest setbacks of solar power is that the amount of power produced by solar panels can vary depending on sunlight intensity, temperature, and shading. For example, a typical PV module produces a maximum power voltage of around 17V when operating at 25°C. Due to the way solar panels respond to heat, this can rise to 18V when operating on a colder day or drop to 16V on a hot day.

These variables can be managed somewhat with careful planning during the design phase, but they are sometimes unavoidable. This directly affects a solar panel's maximum power point (MPP), which is the point at which it generates the maximum power output for a given set of environmental conditions. 

Maximum power point tracking systems use electronic circuitry to continuously adjust the operating voltage and current of the solar panels in an effort to keep them running at their maximum power point. The maximum power point tracking algorithm checks the output of a PV module and compares it to the inverter’s optimal voltage range. It then defines the best power the solar panel can produce to charge the battery and converts it to the best voltage to ensure the maximum current always flows to the grid.

Engineers can maximize the power output from the panels using maximum power point tracking systems. The system works by constantly monitoring the panels' voltage and current output and adjusting the operating point to ensure that the panels are operating at their maximum power point.

Maximum power point tracking controllers are commonly used in solar power systems to increase the solar panels' efficiency and overall energy yield. Using maximum power point tracking systems within a PV plant can help optimize its performance and improve its overall economic viability.

How do maximum power point trackers (MPPTs) improve the efficiency of inverters?

Maximum power point trackers ensure that the panels operate at their peak efficiency regardless of changes in environmental conditions by continuously adjusting the panels' operating point to the maximum power point.

This optimization results in higher energy harvest from the solar panels, which leads to increased overall efficiency of the PV system. Additionally, by maximizing the power output of the solar panels, maximum power point trackers reduce the load on the inverter, allowing it to operate more efficiently within its optimal range.

What are mismatch losses?

Mismatch losses refer to the reduction in overall energy harvest caused by disparities or mismatches between different PV modules within the same system.

Solar PV modules may have variations in their electrical parameters, such as voltage, current, and power output, due to manufacturing tolerances, shading, soiling, aging, or differing environmental conditions (e.g., temperature). When multiple PV modules are connected in series or parallel within a PV system, these variations can lead to mismatches in their operating points.

MPPTs help mitigate mismatch losses by continuously tracking the maximum power point (MPP) of each PV module or string of modules and optimizing their performance despite any discrepancies. By dynamically adjusting the operating conditions of each module, MPPTs ensure that all modules operate at their respective maximum power points, thereby minimizing mismatch losses and maximizing the overall energy harvest of the PV system. This optimization is crucial for maximizing the efficiency and output of solar PV installations, particularly in situations where modules experience varying conditions or are not perfectly matched.

Advanced MPPTs are based on adaptive algorithms to dynamically adjust tracking strategies based on real-time measurements and environmental conditions. These are particularly useful in areas where weather conditions often change and help operators maintain efficient PV systems even during sudden weather changes. 

How many MPPTs are typically found in string and central inverters?

String inverters usually have one MPPT per string. This configuration allows each string of solar panels to be optimized independently, which is crucial for compensating for panels in a string that are subject to different shading conditions or orientations.

Central inverters (also known as large or utility-scale inverters) usually have multiple MPPT inputs. The number of MPPTs in a central inverter can vary (ranging from 2 to 6 or more) depending on the size of the inverter and the requirements of the PV system.

Having multiple MPPTs in central inverters allows for greater flexibility in system design and optimization. The inverter can handle inputs from multiple strings of solar panels with different characteristics or orientations and optimize their power outputs independently. This helps maximize the overall energy yield of the PV system and improve efficiency. 

How do you change the maximum power point tracking configuration in RatedPower?

The maximum power point tracking configuration options are only available when an E-W structure is selected. After choosing this option, you need to go back to “Equipment > Inverter > MPPT configuration” and select the preferred configuration. 

This option will not be available if you use a tracker or a fixed structure. This is because our energy model will consider flat terrain and homogeneous irradiance. That means that no difference will be computed in terms of energy in each of the different maximum power point tracking levels of that inverter, as it would be like using an inverter with only one maximum power point tracker. However, the software considers voltage and temperature parameters to calculate the maximum power point tracking window.