Module Embedded Micro-inverter Smart Grid Ready Residential Solar Electric System

Transcription

1 1 Module Embedded Micro-inverter Smart Grid Ready Residential Solar Electric System This material is based upon work supported by the Department of Energy- under Award DE-EE

2 Technology Summary Module Embedded Micro-inverter Develop and demonstrate power electronics technologies that address: Objective 1 An Innovative microinverter topology that reduces the cost from the best in class microinverter and provides high efficiency (>96% CEC - California Energy Commission), and 25+ year warranty, as well as reactive power support. Objective 2 Integration of microinverter and PV module to reduce system price by at least $0.25/W through a) accentuating dual use of the module metal frame as a large area heat spreader reducing operating temperature, and b) eliminating redundant wiring and connectors. Objective 3 Centralization of a subset of microinverter smart grid and safety functions into an intelligent back-feed capable circuit breaker that can protect the dedicated PV circuit and simplify such functionality for individual microinverters for lower total system cost. SEGIS-AC program Program Summary Key Milestones & Deliverables Year 1 Year 2 Year 3 Lab demonstrations of micro-inverter breadboard designed for thin film module with 96% CEC efficiency and Volt/VAR support and intelligent circuit breaker System cost projection Micro-inverter prototype and reliability test Micro-inverter cost data AC PV module design 2.5KW pilot system demonstration Technical Impact $3/W total installed price vs. GE base residential $4/W; $0.13/kWh LCOE (< average EIA 2015 retail electricity price) Simplified module integration Safety, MPPT and grid support functions including Volt/VAR support Integrated micro-inverter with plug and play interconnections Safety and protection at the feeder circuit level through intelligent breaker

3 Optimization of the Electrical System: GE vision 3 System performance optimization Wider voltage input Volt/Var support Mechanical integration Total system cost reduction

4 Differentiations 4 Key design features Topology generates output with high frequency ripple, which reduces the size of the output filter needed to fulfill the grid requirements. Special control t keep the circuit efficiency high under a wider operating region. Adequate behavior for transformer-less operation with respect to the commonmode noise. Topology and control algorithms modify the output characteristics of the PV panel(s). This yields higher converter efficiency when connected to a higher PV voltage source. Simple integration with added safety Unsubsidized target installed price of $<3.00/W is competitive with retail electricity Gen 1 micro-inverter Not reactive power capable Module embedded micro-inverter Volt/VAR CEC 96% CEC 96% Electrolytic Cap Opto-coupler Micro-inverter optimization 4.0$/W system cost Rack mounted PLC Si-module High reliability No electrolytic cap, no optocoupler Focused on electrical system optimization Reduced system cost 3$/W Mechanical integration AC-PV module (no-junction box) Zigbee communication Si-module, HV GaAs-module, Thin film

5 5 Topology Input stage is a partial power processing LLC resonant converter and the output stage consists of two interleaved full bridge inverters. Input partial power processing LLC resonant DC/DC stage Interleaved DC/AC inverter stage

6 6 Topology Topology generates an output with high frequency ripple, which reduces the size of the output filter needed to fulfill the grid requirements. Special control under light load, keeping the circuit efficiency high under a wider operating region. Adequate behavior for transformer-less operation with respect to the common-mode noise. This yields higher converter efficiency when connected to a higher PV voltage source. The topology and operation have been verified for both high voltage thin film panels as well as for mc-si panels with minor modifications to the input stage. A 96% efficiency was achieved for the high voltage version and preliminary measurements show an efficiency of 95.5% was achieved for the low voltage version

7 Feeder Voltage (pu) Grid Support Functions Voltage variation is caused by the interaction of power output with system resistance Proposed Solution for Voltage Variation Leveraged from Large Scale PV System :00 AM 11:00 AM 3:00 PM 7:00 PM Hour V P V R Q V X

8 Grid Support Functions 8 Var support based on power level (1-10sec) Active Anti-islanding (10-100ms) Var support based on voltage level (1-10 ms)

9 Experimental Results 9 Soft start Low output current THD Anti-islanding shutdown OF Waveforms at 100% load, pf = 1 UF Waveforms at 100% load, pf = 1 50% UV Waveforms at 100% load

10 10 Mechanical Integration + DC and AC Connectors Micro-inverter Simple panel integration with module with no dc cables No Junction box Cheaper installation cost (labor/material) Simpler AC harness with half the cable length requirement of regular AC cabling Grounding through AC ground line Enhanced connection/disconnection safety

11 11 Ongoing and Future Work Testing the integrated ACPV and preliminary verification of compliance with UL 1741/UL1703. Setting up and running ACPV based system in 2 demo sites (rated 2.5kW each). Demonstrate system level communication and control and response to grid commands ACPV module certification.

12 12