SunSpec Inverter Controls Model
SunSpec Alliance Members’ Meeting Jan 2012
Inverter Controls Model
 Defines a model for support of programmed, scheduled and
autonomous inverter control operations.
 New inverter control modes to be optional on a feature basis, via a
set of new SunSpec Device Identifiers (DIDs).
 Allows the inverter to offer a set of capabilities to clients and for
those clients to discover the capabilities of the inverter and to skip
function blocks it does not recognize or implement.
 Applies to PV inverters, with or without battery storage.
 Based on past and on-going work in various industry and standards
bodies, including IEC TC57/WG17, DNP3 User’s Group and EPRI.
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Aligns with IEC draft 61850-90-7 and EPRI draft 1023059.
Current Inverter Model
 Basic inverter measurements and status; no control operations.
 Two maps defined: integer with scale factors and floating point
without scale factors. Unique DID for each map.
 Inverter model map elements:
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AC current and voltages (all phases) and scale factors
AC power, AC frequency, AC VA, AC VAR, AC PF, AC Energy
DC current, voltage, power and scale factors
Temperatures (4) and scale factor
SunSpec status (enumeration), vendor defined status
SunSpec event flags (64 bits), vendor defined event flags (128 bits)
Inverter Controls Model Overview
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Nameplate Ratings
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Basic Settings
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Extended Measurements and Status
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Controls
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Immediate Controls
Basic Storage
Pricing Signal
Static Volt-VAR Arrays
Frequency-Watt Curve
Dynamic Reactive Current
LVRT/HVRT Arrays
Watt-PF
Voltage-Watt
Basic Scheduling
Chained Control Blocks with Defined Device IDs
Nameplate Ratings
 Read-only values set by inverter manufacturer
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Inverter Ratings (Watt, VA, VAR)
Storage Ratings (Amps, Ahr, Whr, Max Charge Rate, Max Disch. Rate
 Required if any controls blocks are used
Basic Settings
 Operating limits and reference values used in control functions
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WMax, PRef, VMin, VMax, VAMax, VarMax, VRef, VRefOfs
MaxWLimPct, ECPNomHz
 Default ramp rates
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MaxRmpRte
 Measurement/setting meanings
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PFSign, VarAct, ClcTotVA, ConnectedPhase
 Required if any controls blocks are used
Extended Measurements/Status
 Inverter present/available
 Storage present/available
 ECP connection status
 Real energy (64-bits)
 Apparent energy (64-bits)
 Reactive energy by quadrant (64-bits each)
 Available VARs
 Time source and current time
 Required if any controls blocks are used
Immediate Controls
 Connect/disconnect from grid
 Max power output [curtailment] (% WMax)
 Fixed PF (cos(ϕ) + excitation)
 Fix VAR (% VarMax)
 Plus random time window, reversion time, ramp time
Basic Storage
 Setpoints for max charge, max charging VA
 Set maximum charge/discharge gradients
 Set minimum reserve storage (% max storage)
 Status/Measurements
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Charge state, state of charge, battery voltage, charge status
 Set storage control mode (charge/discharge)
 Ramp rates
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Power output rate, power input rate
Random window, reversion time, ramp time for in/out power rates
 Grid charge allowed (yes/no)
Pricing Signal
 Pricing signal type
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Absolute price
Relative price
Price multiplier
Qualitative (high/medium/low)
 Pricing signal value
 Random window, reversion time, ramp time
 Used with built-in pricing knowledge or pricing schedule
Static Volt-VAR
 Curve-based description of response
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Variable number of curves (recommend min 4)
Variable number of points (recommend min 10)
 Curves contain points and filter/ramp values
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Volt-VAR pairs as %VRef and %VarAval
Low pass filter time (seconds)
Increment and decrement ramps (%VarAval/min)
Number of active points in curve
 Random time window, reversion time, ramp time
Frequency-Watt
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Parameter or curve-based
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Parameter method
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Watt reduction gradient
Start frequency
Stop frequency
Hysteresis
Curve-based description of response
o Variable number of curves (recommend min 4)
o Variable number of points (recommend min 10)
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Curves contain points and filter/ramp values
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Frequency-Watt pairs as Hertz and %PRef
Low pass filter time (seconds)
Increment and decrement ramps (%WMax/min)
Number of active points in curve
Dynamic Reactive Current Support
 Inject additional reactive current based on change in voltage
 Upper/lower zone limits, outside which no additional VARs supplied
 Upper/lower delta voltages, below which no additional VAR support
 Gradient for additional inductive or capacitive current
 Filter time for calculating average voltage
 Hysteresis voltage
LVRT/HVRT
 Curve-base description
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Must disconnect curve
Optional must remain connected curve
Variable number of points (recommend min 10)
 Curves contain points
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Time-Voltage pairs as seconds and %VRef
 Min/max service voltage for reconnection
 Delay times for reconnection
Watt-Power Factor
 Curve-based description of response
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Single curve (infrequently changed control)
Variable number of points (recommend min 10)
 Curve contains points and filter/ramp values
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Watt-PF pairs as %WMax and cos(ϕ) plus PF excitation
Low pass filter time (seconds)
Increment and decrement ramps (%PF/min)
Number of active points in curve
 Random time window, reversion time, ramp time
Volt-Watt
 Curve-based description of response
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Variable number of curves (recommend min 4)
Variable number of points (recommend min 10)
 Curves contain points and filter/ramp values
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Volt-Watt pairs as %VRef and %WMax
Low pass filter time (seconds)
Increment and decrement ramps (%WMax/min)
Number of active points in curve
 Random time window, reversion time, ramp time
Basic Scheduling
 Array-based X-Y description of schedule
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Variable number of schedules (recommend min 4)
Variable number of entries (recommend min 10)
Variable X meaning (relative time, temperature, price)
Variable Y meaning (%WMax, PF, price, Volt-VAR array,
charge/discharge gradient, VarAval)
 Schedules contain X-Y values
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X value as defined by its meaning
Y value as defined by its meaning
Repetition flag (none, daily, weekly, monthly, weekdays, weekends)
Random time window and ramp time
Number of active entries in schedule
Current Status (2/01/12)
 Two working documents: Word doc with explanatory text and
spreadsheet with Modbus map details.
 Working group meeting weekly (8am PST, Wednesdays).
 Completed first pass of proposed Modbus map and explanatory
document.
 Ready for review by an extended technical audience.
Questions
Bill Randle
AE Solar Energy Headquarters
20720 Brinson Blvd
Bend, OR. 97701
541.323.4441
877.312.3832
bill.randle@aei.com
www.advanced-energy.com/solarenergy