Repower PV Systems

Ampt adapts modern inverters to legacy systems

With Ampt, system owners can use easy-to-source, fully supported, and lower cost-per-watt modern inverters in legacy systems without having to decrease the rated power of the inverter. For example, Ampt optimizers allow 1000V inverters, string or central, to deliver full rated output power in 600V systems. In addition, 1500V inverters can deliver full rated power in 1000V systems.

Ampt optimizers act as a programmable adapter

Ampt optimizers perform maximum power point tracking (MPPT) on each string of PV modules. Full available power from the array is delivered on a high, fixed voltage bus (HFVB) that can be set within the new inverter’s operating range and below the maximum system voltage. In addition to allowing the inverter to deliver full rated power, the higher MPPT resolution improves energy production beyond the central MPPT of the inverter.

1000V central inverters deliver full power in 600V systems with Ampt

A typical 1000V inverter has a standard operating range of 480–850 volts. With Ampt, this inverter operates at a fixed voltage (e.g. 550V). This value is within the inverter operating range and below the 600V maximum system voltage. As a result, the 1000-volt inverter with Ampt delivers its full rated power in a 600V system at the lowest cost-per-watt.

1000V string inverters deliver full power in 600V systems with Ampt

A typical 1000V string inverter has an operating range of 550-850V. For this inverter to be deployed in a 600V system without Ampt, the input voltage would need to be lowered to 275-600V which would decrease its output power. For example, a 1000V 66kW inverter would be derated to 33kW in a 600V system. However with Ampt, this same inverter operates at a fixed input voltage (e.g. 550V) which is within the inverter's operating range and below the 600V maximum system voltage. As a result, the 1000V string inverter with Ampt delivers its full rated power of 66kW in a 600V system. Using string inverters with Ampt results in fewer inverters that are each a lower cost-per-watt.

1500V central inverters deliver full power in 1000V systems with Ampt

A typical 1500V inverter shown has a standard operating range of 850–1250 volts. With Ampt, this inverter operates at a fixed voltage (e.g. 950V). This value is within the inverter operating range and below the 1000V maximum system voltage. As a result, the 1500V inverter with Ampt delivers its full rated power in a 1000V system at the lowest cost-per-watt.

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1500V string inverters deliver full power in 1000V systems with Ampt

A typical 1500V string inverter has an operating range of 850-1250V. For this inverter to be deployed in a 1000V system without Ampt, the input voltage would need to be lowered to 550-1000V which would decrease its output power. For example, a 1500V 125kW inverter would be derated to 80kW in a 1000V system. However with Ampt, this same inverter operates at a fixed input voltage (e.g. 900V) which is within the inverter's operating range and below the 1000V maximum system voltage. As a result, the 1500V string inverter with Ampt delivers its full rated power of 125kW in a 1000V system. Using string inverters with Ampt results in fewer inverters that are each a lower cost-per-watt.

Ampt enables the lowest cost approach to replace legacy central inverters

Ampt allows legacy central inverters to be replaced with modern central inverters that are easier to source, fully supported, and cost less per watt. For example, using Ampt in a 600V system allows a modern 1000V central inverter to deliver full rated power while avoiding the costs of rewiring the PV array to a higher voltage, replacing combiner boxes, and replacing/retrenching DC homeruns. In addition to lowering equipment and labor costs, Ampt optimizers perform MPPT on each string of PV modules. Increasing the MPPT resolution beyond the central MPPT of the inverter improves legacy system performance.

Ampt lowers costs when using string inverters to replace a central inverter

Ampt lowers costs by allowing modern string inverters to deliver their full rated power without rewiring the PV array to a higher voltage. For example, a 1000V 66kW string inverter deployed in a 600V system without Ampt would only deliver 33kW. However, deploying Ampt optimizers on existing PV strings allows this same inverter to deliver its full 66kW in a 600V system. As a result, fewer inverters are used and each one cost less per watt. By centrally locating the string inverters, the existing DC homeruns can be used to avoid the cost of rewiring/retrenching AC homeruns. Ampt also replaces the central MPPT of the legacy inverter with string-level MPPT to improve system performance.

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Ampt lowers the cost of using distributed string inverters to replace a central inverter

When replacing a central inverter by distributing string inverters throughout the array, Ampt saves on equipment and labor costs by reducing the number of inverters and AC homeruns to purchase and install. For example, a 1000V 66kW string inverter deployed in a 600V system without Ampt would only deliver 33kW. However, deploying Ampt optimizers on existing PV strings allows this same inverter to deliver its full 66kW in a 600V system. As a result, fewer inverters are used and each one cost less per watt. Fewer inverters mean that there are fewer AC homeruns compared to the same approach without Ampt. Ampt also replaces the central MPPT of the legacy inverter with string-level MPPT to improve system performance.

Low-cost solution restores system performance

Voltage sag refers to a gap between the minimum DC voltage required by the inverter to meet grid requirements and the MPP voltage of the array (Vmp). When this occurs, the inverter takes the array off its MPP voltage to meet grid requirements which results in production losses. The low MPP voltage of the array is unplanned and is typically due to a system design related issue or accelerated module degradation. Once observed, voltage sag will increase as the modules age.

Ampt optimizers eliminate voltage sag losses by converting the variable PV string voltages into a high and fixed voltage. This ensures that the inverter always receives full available power from the array while meeting grid requirements.

Restore system performance without reworking the array

Ampt optimizers have two inputs and one output. PV strings are connected to each input. The full power from each PV string is combined and delivered to the optimizer output at a fixed DC voltage that is set by the inverter and high enough for it to meet the grid’s VAC requirement.

Ampt fits into the existing DC array wiring to avoid costly rework of the system. Without Ampt, system owners would need to replace large numbers of modules to build up voltages and/or rewire the PV strings to be different lengths.

Mix new and legacy PV modules during replacement without creating mismatch

The challenge of mixing new and old modules is that they have different output characteristics that create electrical mismatch. The resulting performance losses can be substantial – offsetting the intended production gain of the new modules.

Ampt optimizers perform MPPT on each string to deliver full available array power at a high, fixed voltage. This eliminates voltage mismatch between strings and prevents energy losses that would normally occur without Ampt.

Increase inverter loading ratio to generate more energy

Older PV systems have relatively low inverter loading ratios (ILR) compared to modern systems. These systems can be repowered by using today’s lower-cost modules to increase annual energy generation. This is beneficial where the value of energy is relatively high or when excess energy can be captured in an energy storage system.

Ampt String Optimizers allow PV systems to achieve higher loading ratios without creating performance issues caused by mixing new and old modules and without overloading the existing wires and inverter. Increasing the ILR with Ampt can be done by either replacing legacy modules with new high-power modules or by adding more PV strings to the existing inverter. Ampt enables loading ratios up to 3:1 for DC-coupled storage applications.

Replace legacy modules with new, higher power modules to generate more energy

By replacing legacy modules with new, higher power modules, system owners can increase the energy generation of their system. Ampt String Optimizers perform MPPT on each string to allow both the old and new modules to deliver full power. Because the optimizers are installed on existing wires, combiners, and inverters, Ampt lowers the cost of repowering with new modules. Ampt also ensures that the added DC power does not exceed the ampacity of the existing wires or inverter.

Add new modules to generate more energy

Adding new strings of higher-power modules is another way to grow the DC power of a PV system and increase production. Using Ampt optimizers allows strings of new and old modules to be used together without creating voltage mismatch losses. Ampt’s string-level MPPT maximizes the energy produced by both the new and old strings while Ampt’s patented output voltage and current limits ensures system operation below the ampacity of existing wires and the input current limit of the inverter.

Ampt recovers degradation losses

As systems age, PV modules naturally degrade over time and at different rates. This results in voltage imbalances, or mismatch, between strings which compromises the performance of the array. Ampt Optimizers perform MPPT on each string of PV modules and typically recover 66% of mismatch losses or approximately 33% of total annual system degradation. Repowering with Ampt improves system performance over its remaining lifetime.

Ampt recovers energy losses from other sources of mismatch

In addition to degradation recovery, Ampt delivers incremental system performance improvement by recovering energy losses from other sources of mismatch. For example: manufactured module mismatch, thermal gradients, uneven soiling, shade, cloud shading, and voltage drop in conductors.

Improve performance at a lower cost

In addition to recovering energy losses by performing MPPT on each string of PV modules, Ampt enhances system O&M by providing string-level data via wireless communication. Ampt delivers these system improvements in an easy-to-mount package that is deployed on existing wiring, combiners, and inverters.

Rapid installation on existing wiring and combiners

Disconnect strings from combiner.
Connect one string to each optimizer input using existing cables.
Connect optimizer output to combiner.
Set inverter to constant or narrow-range voltage operation.

Contact us to see how to upgrade your system with Ampt

Ampt works closely with you to understand how your system is performing today and how to best use Ampt to increase your production and maximize your return on investment.