BS ISO 8528-3:2020 Reciprocating internal combustion engine driven alternating current generating sets.
Asynchronous generators with special generator control and excitation equipment running in parallel (to another such a.c. generators or to the mains), share the reactive power demand of the connected load according to the capabilities of their excitation systems.
Asynchronous generators share the active power demand of the connected load according to the speed of the RIC engine.
7.3 Parallel operation with grid
When an a.c. generator is running in parallel with a public network, it is presupposed that the generating set manufacturer specifies the a.c. generator to fulfil the local grid code requirements.
NOTE 1 EEC/TS 62786 provides principles and technical requirements for generating sets connected to the distribution network.
Means shall be provided to ensure stable operation and correct reactive power sharing. Often this performance is affected by several auxiliary control functions of the a.c generator excitation control system. To obtain reliable results, the a.c. generator manufacturer can be required to provide all generator relevant quantities (including peak value of short circuit current of a generator under specified conditions) and exciter parameters. The tolerance of the parameter shall be agreed between the a.c. generator manufacturer and the generating set manufacturer.
NOTE 2 For some simulations, tolerance of ±30 % for peak value of short-circuit current of an a.c. generator under specified excitation (IEC 60034-1:2017, Table 21) is too wide. Stability simulations demand higher accuracy, i.e. ±15 % of the value, to obtain reliable results.
NOTE 3 At the request of the relevant system operator, the power-generating facility owner is asked to provide simulation models which properly reflect the behaviour of the power-generating module in both steady-state and dynamic simulations or in transient simulations.
7.3.5 Power system stabilizer (optional)
Various grid codes and utilities request the option to implement a “power system stabilizer”. The function shall be agreed upon between the generating set manufacturer and the distribution or transmission network operator. Oscillations between a group of a.c. generators, local area oscillations and interarea oscillations range from typically 0,1 Hz to 2,0 Hz. A power system stabilizer utilizes additional input signals to the a.c. generator excitation system to introduce further positive damping into the complex system comprising the synchronous generator, its excitation system and the power plant.
7.4 Effects of electromechanical vibration and its frequency
It is the responsibility of the generating set manufacturer to ensure that the generating set operate in a stable manner when connected in parallel with others and the a.c. generator manufacturer shall collaborate as necessary to achieve this.
If there is a RIC engine torque irregularity at a frequency close to the electromechanical natural frequency, resonance can occur. The electromechanical natural frequency can be calculated with synchronization power, moment of inertia of the system and firing interval of the engine.BS ISO 8528-3 pdf download.