Utility-Scale Solar Solutions
Mitsubishi Electric Power Products, Inc. offers an industry leading PV inverter and integrated skid solution. An inverter is a power electronics device that converts the DC power generated by a solar array into AC power which feeds into the utility grid. MEPPI supplies a full range of PV inverters rated up to 1833kW at 1000Vdc and between 2500 and 3200kW at 1500Vdc. The newest addition to this line is the PVH-L3200GR inverter rated at 3200kW/3200kVA, compliant with new UL 1741-SA rules, and ready for delivery in early 2018.
The inverters require an external step up transformer to match the grid interconnection voltage. The use of an external transformer allows for flexibility in transformer selection and overall optimization of the system for specific project requirements. MEPPI can provide a skid solution which integrates the inverter, recombiner, and transformer on a common skid base for easy site installation.
MEPPI's inverter offers numerous key and differentiating features:
- Advanced multilevel inverter - up to 56% reduction of switching losses
High-yield power generation - maximum efficiency of 99%
Cooling system optimized for desert environments
High efficiency in any weather
Maximized and optimized efficiency at high load
Wide MPPT range allowing for best-in-class DC/AC ratios
Flexible DC-input configuration to meet complex array configurations
One of the key technical advances designed into this inverter is the use of a 3-level neutral point switch (NPS) topology based power electronics bridge. NPS is a more advanced architecture than that previously used in inverter design and offers higher efficiency and improved power quality through:
- Higher DC voltage capability
- Support for higher DC/AC ratios
- Significant reduction in swiching losses
- Significant reduction in stress on components
The rating of each inverter is achieved by paralleling four separate inverter modules. The four modules are operated in parallel but function continuously as one large inverter. A single MPPT algorithm operates on the entire DC input. The DC input from the array is connected to the inverter through a recombiner box. This box is designed to meet the requirements of the project and local electrical safety code.
The AC inverter outputs are in parallel and connect to a single three phase AC output bus and simple step up transformer – no complicated multi-winding transformers are required.
MEPPI’s inverter incorporates a hybrid cooling system that utilizes heat pipe technology and convection at different load conditions:
- For low load (≤50% rated load), the inverter is cooled by the heat pipe system along with natural convection located on the IGBT stack
- Above 50% load, variable speed fans are used to assist the heat pipe system with cooling
This approach to cooling is significantly less complex and more reliable than the liquid cooling or high speed fan convection cooling systems used in every other inverter. The low number of moving parts, low component count, and minimal fan operation results in an industry-leading efficiency and reliability.
A critical metric for PV inverters is the operating efficiency over the full range of output power levels and across the range of typical DC input voltages. MEPPI inverters provide peak efficiency of 99% at unity power factor and CEC efficiency of 98.5%. This industry-leading efficiency results in improved LCOE for the solar plant – improving return on investment and profitablity for our customers.
The heart of the inverter is the Mitsubishi Electric 7th generation IGBT. These IGBTs are well known for having one of the semiconductor industry’s most stringent in-house quality and reliability screen testing. This level of quality has resulted in single digit IGBT field failures across 10GW of installations.
High reliability is accomplished using two design philosophies – minimizing component stress and proper component selection. High quality parts are designed to operate at stress levels that allow them to perform reliably for their service lifetime (and often beyond, allowing for usage in 30-35 year solar projects). When selecting components, MEPPI avoids use of any items with known wear-out mechanisms. Examples of items with known wear-out mechanisms that are used in the solar industry are electrolytic capacitors (commonly found in string inverters) and cooling systems using pumps and fans (found in most central inverters). MEPPI’s inverter does not use any electrolytic capacitors and the hybrid cooling system minimizes fan usage while eliminating pumps entirely.
As the only inverter supplier with over 30 years of electric utility experience and a sole focus on the utility industry, MEPPI understands the importance and challenges with grid integration. MEPPI’s inverter provides grid support features to ensure successful integration and operation:
- Voltage conditioning
- Reactive power support
- Power factor control
- Flexible ride-through features
Having provided analytical services for over 10GW of projects integrating renewable energy technologies, MEPPI is a partner you can count on for grid modernization.
Integrated Skid Option
MEPPI can provide a standalone central inverter or an integrated skid solution. The skid option allows a single physical structure to be deployed on-site. The skid solution includes the DC recombiner, inverter, output step-up transformer and any optional equipment. Skid details are reviewed on a project-by-project basis to ensure compliance with specific installation requirements.