Parallel Connections Of Converters; General; Parallel Connections Of Sinamics Converters - Siemens SINAMICS G130 Engineering Manual

1.15 Parallel connections of converters

1.15.1

General

It can be useful to connect complete converters and their components (Infeed Modules and Motor Modules) in
parallel for a number of reasons:
·
To increase the converter output power if it is not technically or economically feasible to achieve the
required output power by any other means. For example, it is a relatively complicated procedure to create
parallel connections of large numbers of IGBT modules within the same power unit which means that
using parallel connection of complete power unit s can be the simpler and more cost-effective solution.
·
To increase the availability in cases where it is necessary after a converter malfunction to maintain
emergency operation during which the unit can operate at a lower output than its rated value. In the event
of more or less minor defects within the power unit, for example, it is feasible to deactivate the affected
power unit via the converter control system without shutting down the power unit that are still functional.
The parallel connection strategy for SINAMICS units is essentially designed to increase the converter power output.
The parallel-connected modules (Infeed Modules and Motor Modules) are driven and monitored by a single Control
Unit and are constructed of exactly the same hardware components as the equivalent modules for single drives. All
the functions required for parallel operation are stored in the firmware of the Control Unit. The use of a single shared
Control Unit for the parallel-connected modules and the fact that each fault in any module leads to immediate
shutdown of the entire paralleled system means that a converter parallel connection can be regarded in practical
terms as a single, high-power-output converter.
The parallel connection must be protected on the line side. This protection can be realized by a single circuit breaker
for the entire parallel connection or several circuit breakers or switch disconnectors with fuses or fuse holders with
fuses that are assigned to the partial infeeds of the parallel connection. In the latter case, the line-side components
specified for the relevant individual infeeds in Catalog D 21.3 should be used wherever possible. Where these
components are used to protect parallel connections, they must be monitored commonly so as to ensure reliable
detection of malfunctions of individual protective devices within the parallel connection.
1.15.2

Parallel connections of SINAMICS converters

The modular SINAMICS S120 drive system provides the option of operating Infeed Modules and Motor Modules in
parallel on S120 units in the Chassis and Cabinet Modules format. SINAMICS S120 units in Booksize and Blocksize
format cannot be operated in parallel.
S120 Motor Modules can be operated in parallel in vector control mode (drive objects of vector type), but not in servo
control mode (drive objects of servo type).
The SINAMICS G150 cabinet units in the high output range (P ≥ 630 kW for 400 V units, P ≥ 630 kW for 500 V units
and P ≥ 1000 kW for 690 V units) are also designed as a parallel connection. They are based on two low-output
G150 converter cabinets or, in the power range above 1500 KW, on the parallel connection of two Basic Line
Modules and two or three Motor Modules. The details and special features of the G150 converter parallel connections
are described at the end of chapter "Converter Cabinet Units SINAMICS G150".
This section will provide a more detailed description of the basic options for making parallel connections of units of
the SINAMICS S120 modular drive system in Chassis and Cabinet Modules format.
A SINAMICS S120 converter parallel connection consists of:
·
Up to four Infeed Modules (line-side rectifiers) connected in parallel.
·
Up to four Motor Modules (motor-side inverters) connected in parallel.
·
A Control Unit which controls and monitors the power units connected in parallel on the line and motor
sides. In addition to the line-side and motor-side parallel connections, the Control Unit is capable of
controlling one further Motor Module or drive object of vector type.
·
Components on the line and motor side for line-side protection of the parallel connection, for de-coupling the
parallel-connected power units and for ensuring symmetrical current distribution.
Fundamental Principles and System Description
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