Harmonic Neutralization – The Key to a More Powerful,
Less Expensive Inverter
“If you always do what you’ve always done, you’ll always get what you’ve always got.”
Alencon’s patented Harmonic Neutralization (HN) technology is a unique power inverter technology that allows PV plant operators to drive the economies we so badly need in the utility scale solar sector. This new approach to inverter design helps breakthrough the AC power-output ceiling found in the traditional, utility scale PV inverters that rely on the pulse-width-modulation (PWM) method of power conversion.
HN allows inverters to be built with several inverter modules on a common DC bus. Each inverter module is synchronized with the grid frequency, however with specifically calculated leading or lagging phase angles between output current and grid voltage, uniquely set for each inverter module in the system. The output AC currents are then summed on a phase shifting transformer to return the phases of all currents to a single combined output, with adjustable phase to the grid’s voltage. This maneuver sums the fundamental currents in all of the inverter windings into the grid winding but neutralizes the higher harmonics and prevents injection of those harmonics into the distribution grid. As a result, HN allows for a simpler solar array topology, lower initial installation costs, increased energy yields and lower power losses.
The HN approach to inverter design has a number of technical benefits over PWM, including:
- Smaller size, higher power density, and lower equipment cost per MW rating.
- High efficiency (99.5%) achieved through low (50/60 Hz) switching frequency
- Unsurpassed reliability from simplified construction: Several three phase heavy-duty inverter modules operate concurrently from the same DC source into the same load assuring that even the entire loss of one module only minimally affects power generation.
However, with HN, the benefits don’t stop at the inverter level. Where HN really gets compelling is at the BoS level. The key to high-energy yield from HN-based inverters is granular, optimized PV power harvesting. The HN system achieves this via string-level DC to DC optimizers.