APPLICATION NOTE AP004 - OCT 17, 2017 HOW TO USE H5000B TO RUN 5KW OF ENPHASE M250 OFF-GRID Dr. Frank O Young frank.oyoung@darfon.com
1. Principle of AC-coupling When Off-Grid When the grid is down and an existing solar system with Enphase M250 is inoperable, the best solution for continuous use of the solar system is to use Darfon's H5000B hybrid inverter and a battery array in an AC-coupled configuration with the microinverters. Darfon s H5000B hybrid inverter can operate in an off-grid environment. The H5000B hybrid inverter is nominally 5kW of AC output and allows a short burst up to 7kW. The built-in battery charger can charge at 60A and discharge at 150A. The inverter is bidirectional which allows charging the battery from the grid if it is present. In the top illustration of the drawing below, a typical grid-tied PV system with Enphase M250 microinverters is depicted. Since grid power is present, the microinverters operated normally to supply power to the loads at home through the home s main service panel. Without the grid present, the microinverters would shut down due to anti-islanding mechanism. PV MODULES ON-GRID ENPHASE M250 MICRO INVERTERS HOME MAIN PANEL PV MODULES OFF-GRID ENPHASE M250 MICRO INVERTERS HOME SUB- PANEL H5000 HOME MAIN PANEL BATT The lower illustration of the drawing above shows how AC-coupling configuration is setup between the Enphase M250 and Darfon H5000B. When the grid is down, the H5000B, coupled with batteries, becomes a voltage and frequency source for the M250 units, keeping them in continuous operation without going into anti-islanding. To power the home during the blackout, a particular load circuit running critical appliances is rerouted to a subpanel situated between the microinverters and the H5000B. The battery array should be nominally around 48 to 50V. Either lead-acid or lithium-based batteries can be used, though the lead-acid and lithium batteries behave slightly different in charging and discharging modes. 2017 Darfon America Corp. www.darfonsolar.com Page 2 of 8
2. Batteries In this paper lithium ferrite phosphate (LiFePO4 or LFP) batteries are being used to pair with the H5000B. The LFP batteries are USA-made, and has built-in BMS. It is a 12V module with BMS board built-in. It is specially designed to be used as a replacement for lead-acid batteries so 4 of the LFP modules can be serially connected to form 48V. Specifications Features 12.8V Operating Voltage Built in Battery Management System 14.4-14.6V Charging Voltage 100 amp continuous current ABS Fire Rated Case 200 amp surge for 30 seconds 0.25 Thick Brass Terminal Blades 1/2 second surge for higher loads Operating Temp Range -4F 160F High/Low Voltage Protection Dimensions (L x W x H) 12.75x 6.88 x 9 Short Circuit Protection 29 lbs High/Low Temperature Protection Automatic Cell Balancing 12V LFP battery module 2017 Darfon America Corp. www.darfonsolar.com Page 3 of 8
3. System Specifications H401B is a system SKU that include a H5000B hybrid inverter, twelve (12) 100Ah/12V lithium LFP battery packs, and a distribution box. H401B x1 x12 SOLAR MODULE AC INPUT Maximum Power 5000W Voltage Interactive Range L-L: 211 to 264V ± 3.0V Frequency Interactive Range 59.4 to 60.4Hz ± 0.05Hz Maximum Input Current 20A AC OUTPUT TO LOAD Output Power (Continuous) @ 25 C 5000W Surge Output Power 7500W Rated Output Current 20A (@120V and 240V) Output Frequency 60Hz (default) Output Voltage L-N: 120V ± 3%; L-L: 240V ± 3% Total harmonic distortion (THD) at rated power < 5% AC INPUT FROM GRID AC Input Voltage Limits (Bypass) L-L: 180 to 280V (240V nominal) Automatic Transfer Relay Rating / Typical Transfer Time 33A / 20ms AC Input Frequency Range (Bypass) 55 to 65 Hz AC OUTPUT TO GRID Grid Feed-in Current Range 0 to 20A (240V) Grid Feed-in Voltage Range L-L: 211 to 264V ± 3.0V Grid Feed-in Frequency Range 59.4 to 60.4Hz ± 0.05Hz DC BATTERY CHARGER Maximum Charge Current 60A Output Voltage Range 42-60V (48V Nominal) Power Factor Corrected of Charging Mode >98% FEATURES System monitoring and network communications Available Intelligent features AC coupled in OFF Grid Operation. Auxiliary function port Auto Cut off PV power energy when PV power > Load Power and battery full 2017 Darfon America Corp. www.darfonsolar.com Page 4 of 8
4. Off-Grid Priorities Normally when the grid is present, the H5000B can operate in one of the following 4 modes: 1. Backup (default) 2. Time-of-Use without battery feed-in 3. Time-of-Use with battery feed-in 4. Peak-shaving 5. Frequency regulation However, once the grid is missing, the H5000B would automatically enter the off-grid mode where it has a preset of priorities for PV, load, and battery in terms of direction of energy flow. AC COUPLING MODES PV POWER TO LOAD POWER FROM CHARGE SOURCE Load Batt. Grid PV Grid Batt. PV Grid Off-grid priorities 1 2 N/A 1 3 2 Yes No When the grid is down, this configuration allows the energy of the microinverters to either go directly to the loads, or to charge the batteries. The loads can receive energy from either the microinverters or the batteries. PV priorities and load priorities are illustrated in the drawings below. PV PRIORITIES LOAD PRIORITIES 1 1 PV INVTR H5000 PV INVTR H5000 2 2 2017 Darfon America Corp. www.darfonsolar.com Page 5 of 8
5. Wiring for AC-Coupling The drawing below shows how the H5000B and microinverters are to be wired with critical loads, batteries and the main service panel, in an AC-coupled configuration. IMPORTANT NOTES In the AC-coupled operation, the recommended ratio of micro inverter power to battery power is equal or less than 1, i.e. micro inverter power shall be no more than 5kWac. For the protection of the entire system, it is required to use a 240VDC / 30A relay for cutting off the power of the micro inverters. A current sensor is to be installed for power measurement. See next section for controlling the micro inverters. 2017 Darfon America Corp. www.darfonsolar.com Page 6 of 8
6. Controlling the Micro Inverters 6.1. Auxiliary Control Port On the bottom panel of H5000B, there are 7 pins on the auxiliary control port with definitions for 1) dry contact, 2) 12VDC source and 3) Current/voltage level sensor. It could be used to remote control an external relay. Electric Parameter 1 2 3 4 5 6 7 PIN # SYMBOL DESCRIPTION REMARK 1 - sensor Current /Voltage Level Sensor By using high resistance resistor for Current/voltage sensor. 2 + sensor 3 +12V 12 VDC source Max. rating current: 250mA 4 Ground 5 N/A N/A N/A 6 Normal Open Dry contact Normal : Open 7 Common Action : Close Function Description UNIT CONDITION 12VDC SOURCE DRY CONTACT Power Off Unit is off and no output is powered. 12 Vdc Open Power On Grid Available Battery voltage < Battery cut-off discharge voltage 12 Vdc Open Battery voltage > Battery re-discharging voltage 12 Vdc Open Grid Unavailable Battery voltage < Battery cut-off discharge voltage 12 Vdc Close Battery voltage > Battery re-discharging voltage 12Vdc Open Battery SOC > 97% or DC bus voltage > 500VDC 0 Vdc Open A current sensor is also required to measure the power of the microinverters. The auxiliary port is also connected to the current sensor. 6.2. Frequency-Shift Regulation (*Frequency-shift regulation maybe activated starting from Nov 2017) Here frequency-shift regulation is done on the AC side of the system by limiting the output of the microinverters when the batteries are fully charged. In order to protect the H5000B, the frequency-shift regulation is adopted in the off-grid mode. The H5000B can use frequencyshift to control the output of the microinverters in one of the two statuses: 1. No output 2. Derated output (Enphase M250 does not support this mode) 2017 Darfon America Corp. www.darfonsolar.com Page 7 of 8
7. Distribution Box for H5000B Darfon has designed a pre-integrated distribution box, D06, which is designed specifically for the H5000B in the AC-coupling configuration. The D06 pre-wires the battery and PV disconnects, load and grid breakers, all the DC and AC terminals and generator (or other inverter) connection in a metallic enclosure with lockable access door, as seen below. The D06 has a built-in electromagnetic switch which is used as a relay to cut off the power from microinverters in the ACcoupled configuration. Grid Breaker Interlock & Load Select from Magnetic Contactor INV. Grid Battery Breaker Power Distributed Terminal Power Distributed Terminal Definition of Power Distribution Terminals: PIN DEFINITION DETAIL DESCRIPTION Utility Grid Terminals L1 (Black) AC input Voltage: 240V/120V. N (Gray) Maximum Current: 21 Amp L2 (Red) Critical Load Terminals L1 (Black) AC output Voltage: 240/120V N (Gray) Maximum Output Current: 21Amp AC Input (AC Module or Generator) L2 (Red) L1 (Black) L2 (Red) 12VDC Signal GND Dry Con. 1 Dry Con. 2 Acceptable AC power supply (ex: Grid-tied inverter or Generator) Input Voltage: 240V/120V. Maximum Current: 21 Amp 12VDC source: Max. 240mA output. Dry connector: Max. 8 Amp current pass though. 2017 Darfon America Corp. www.darfonsolar.com Page 8 of 8