SunSpec Model 64411 — AC Simulator Control Interface
SunSpec Model 64411 is a Modbus TCP control interface for AC grid simulator instruments used in DER compliance testing labs. The template reads measured per-phase voltages (va, vb, vc), currents (ia, ib, ic), and output frequency (hz), and writes simulator configuration registers including nominal voltage (vnom), per-phase voltage setpoints (vseta, vsetb, vsetc), frequency (freq), voltage and frequency slew rates (vslew, freqslew), output and relay enable flags, and harmonic and THD readback arrays across all three phases. Scale factor registers (v_sf, a_sf, hz_sf, thd_sf) apply SunSpec exponent scaling to all numeric readings. Connecting this template in the ModbusCloud portal gives test engineers live visibility into simulator state during inverter certification runs.
- Protocol
- Modbus TCP
- Connection
- Ethernet, Modbus TCP
- Registers
- 50, read and write
- Brand
- SunSpec
- Last updated
Registers (50)
50 read, 16 write
| Name | Unit | Access | Address (Hidden until you enter your email) | Function (hidden) | Type (hidden) |
|---|---|---|---|---|---|
| id | Read | ||||
| l | Read | ||||
| phases | Read and write | ||||
| phaseangle | Read and write | ||||
| vnom | V | Read and write | |||
| vmax | V | Read and write | |||
| imax | A | Read and write | |||
| freq | Hz | Read and write | |||
| output | Read and write | ||||
| relay | Read and write | ||||
| regen | Read and write | ||||
| vset | V | Read and write | |||
| vseta | V | Read and write | |||
| vsetb | V | Read and write | |||
| vsetc | V | Read and write | |||
| freqslew | Hz/s | Read and write | |||
| vslew | V/s | Read and write | |||
| va | V | Read | |||
| vb | V | Read | |||
| vc | V | Read | |||
| hz | Hz | Read | |||
| ia | A | Read | |||
| ib | A | Read | |||
| ic | A | Read | |||
| vhara | V | Read | |||
| vharb | V | Read | |||
| vharc | V | Read | |||
| ihara | A | Read | |||
| iharb | A | Read | |||
| iharc | A | Read | |||
| iinthara | A | Read | |||
| iintharb | A | Read | |||
| iintharc | A | Read | |||
| vthda | % | Read | |||
| vthdb | % | Read | |||
| vthdc | % | Read | |||
| ithda | % | Read | |||
| ithdb | % | Read | |||
| ithdc | % | Read | |||
| enaprof | Read and write | ||||
| profrslt | Read | ||||
| nprof | Read | ||||
| npt | Read | ||||
| v_sf | Read | ||||
| a_sf | Read | ||||
| tms_sf | Read | ||||
| hz_sf | Read | ||||
| hzslew_sf | Read | ||||
| vslew_sf | Read | ||||
| thd_sf | Read |
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If a device is not in the library yet, we build the template for free as soon as we have the register data.
Use cases
- Monitor per-phase output voltages (va, vb, vc) in real time to verify simulator stability during inverter grid-code tests.
- Track total harmonic distortion registers (vthda, vthdb, vthdc) across a test campaign to confirm waveform quality over time.
- Alert when measured output frequency (hz) deviates from the setpoint (freq) by more than an acceptable margin.
- Compare voltage slew rate (vslew) and frequency slew rate (freqslew) setpoints against actual ramp behavior to spot misconfiguration.
- Verify that the output and relay enable flags are in the expected state before and after each automated profile run (enaprof, profrslt).
Installation
Enable Modbus TCP on the AC simulator instrument under its communication or network settings menu, and note the assigned IP address and TCP port (typically 502).
Connect the simulator to the same LAN segment as the ModbusCloud Gateway, ensuring no firewall blocks port 502 between them.
In the ModbusCloud portal, add a new gateway, import the SunSpec Model 64411 template, and set the Modbus unit ID and base address offset to match the simulator's configured values.
Spot-check the connection by reading the id register (address 0) and confirming the returned value matches the expected model ID, then verify hz shows a plausible frequency reading.
Things to watch for
Voltage and current readings look wrong by a factor of 10 or 100. Why?
SunSpec uses signed integer scale factors. Read the v_sf and a_sf registers and apply the exponent: actual value equals raw register value multiplied by 10 raised to the power of v_sf or a_sf. A v_sf of -2 means divide raw volts by 100. Confirm the portal is applying these scale factors.
The gateway connects but all harmonic array registers return zeros or errors.
The vhara, vharb, vharc, ihara, iharb, iharc, iinthara, iintharb, and iintharc registers are large string-typed arrays at high offsets (31 to 1380). Some Modbus TCP implementations limit single read length to 125 registers. If your gateway issues one large read request, it will be rejected. Configure the ModbusCloud Gateway to split reads into smaller chunks covering each array separately.
The gateway shows no data after import. What should I check first?
Confirm the unit ID in the portal matches the simulator's configured Modbus slave address. SunSpec devices using base address 0 require the client to start reading at 0, not 40001. Also confirm TCP port 502 is reachable from the Gateway host using a Modbus scanner or ping before ruling out network issues.
Is it safe to write vset, vseta, freq, or output during a live test?
Exercise caution with all write registers (vnom, vmax, imax, freq, vset, vseta, vsetb, vsetc, vslew, freqslew, output, relay, regen, enaprof). Writing unexpected voltage or frequency values during an active test can disrupt the device under test, trip protection relays, or invalidate test results. Always confirm the test sequence is paused before issuing writes from the portal.
Knowledge base articles for this device
SunSpec Modbus: one register map for many inverters
SunSpec Modbus is the open register map SMA, Fronius, SolarEdge and Kostal share. The layout, int+SF vs float, the TCP port per brand and reading a mixed fleet.
Fronius Modbus: read a Symo GEN24 over Modbus TCP
Fronius Modbus explained: enable Modbus TCP on the Symo GEN24 on port 502, choose between int+SF and float, read the right SunSpec registers and scale them correctly. Practical guide for solar installers.
SMA Modbus: reading a Sunny Boy over Modbus TCP (installers)
SMA Modbus explained: enable the Modbus TCP server on port 502, choose between the SMA profile (unit ID 3) and SunSpec (unit ID 126), read the right registers, and handle the NaN values at night. Practical guide for installers.
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