Electric power system and control method thereof

An electric power system for driving an inductive load, the electric power system being connected with a DC power generating system and comprising:

• a variable-frequency drive for converting electric energy in a bidirectional manner, wherein the variable-frequency drive comprising:
• an inverter circuit receiving a DC voltage and converting the DC voltage into AC output energy, wherein the AC output energy is outputted to the inductive load;
• and
• at least one energy storage module connected with the inverter circuit;
• and
• a control module connected with the variable-frequency drive and the inductive load, wherein according to a dynamic loading change of the inductive load, the control module controls a charge/discharge operation of the at least one energy storage module so as to reversely compensate the dynamic loading change of the inductive load and reduce an influence of the dynamic loading change of the inductive load on an input power of the variable-frequency drive.

A control method of an electric power system, the electric power system being connected between an electric/kinetic energy conversion device and a power terminal, the electric power system comprising a variable-frequency drive and a control module, the control module controlling a charge/discharge operation of an energy storage module of the variable-frequency drive, electric energy being transferred between the electric power system and the power terminal at a first power, electric energy being transferred between the electric power system and the electric/kinetic energy conversion device at a second power, the second power being dynamically changed in response to an operational change of the electric/kinetic energy conversion device, the control method comprising steps of:

• (a) calculating the second power according to plural parameters of the variable-frequency drive, and performing a spectral decomposition on the second power to acquire a spectral sequence of the second power;
• (b) filtering the spectral sequence to acquire a compensated power in a specified frequency range;
• and
• (c) the control module using the compensated power to control a charge/discharge operation of the energy storage module according to a dynamic change of the second power, thereby reversely compensating the operational change of the electric/kinetic energy conversion device and reducing an influence of the operational change of the electric/kinetic energy conversion device on the first power.