TWERD Power Electronics PS100-WT - Dump Load Resistors; The Internal Process of Switching on the Inverter in On-Grid Mode; The Internal Process of Switching the Inverter Off-Grid

Chapter 8. The first run
8.4. Dump load resistors
Dump load resistors (not supplied) should be connected to proper terminals – see suitable Fig. from section
5 or 6.The dump load resistors relays have switching capacity in the category AC1: 30A.
Dump load resistors resistors will be switch on in four cases:
a) generator’s RMS voltage will exceed the value from the parameter 10.2 (U RMS gen. ham.),
b) generator’s frequency will exceed the value set in the parameter 10.3 (Czest. gen. ham.),
c) the lack of an electrical grid,
d) during a failure.
8.5. The internal process of switching ON the inverter in on-grid mode
• After connecting to the electrical grid, the inverter with PV inputs monitors the panel voltage; the
inverter with generator input first disconnects the load dump resistors and starts to monitor the
generator voltage and frequency.
• The inverter checks whether the voltage and frequency of the network is correct.
• By collecting energy from a source connected to the input, it increases the voltage in the DC circuit
to the level suitable for switching on the power network.
• Performs synchronization with the electrical grid.
• If the voltage received from the renewable source is high enough (threshold defined by parameter
1.20), the MPPT algorithm starts and the solar panels load according to the MPPT algorithm or
generator according to the curve introduced in group 3. The obtained electricity is sent to the
electrical grid.
8.6. The internal process of switching the inverter off-grid
The device works autonomously, requires no maintenance.
The internal switching process is as follows:
• After connecting the batteries, the system increases the voltage in the DC circuit to a value that
allows the generation of 230V AC RMS voltage.
• In the case of a photovoltaic input, it monitors the voltage of the panels, while in the case of a
generator input it disconnects the load resistors and begins to monitor the voltage and frequency of
the generator.
• Taking energy from renewable sources, the inverter directs it to electrical loads first. When the
available electrical power exceeds the demand for electrical loads, the process of charging the
batteries connected to the inverter occurs.
In a situation where the demand for electric power by the load exceeds the power generated by
renewable sources, the inverter turns into the battery discharge mode.
PS100 – User manual 39