Method of controlling electrical power system and apparatus using the same

1. A method of controlling an electrical power system, wherein the electrical power system comprises: a DC bus and a DC bus capacitor connected to the DC bus, and the method comprises:

a setting step, receiving a virtual DC bus capacitance value of the DC bus capacitor, wherein the virtual DC bus capacitance value of the DC bus capacitor is an equivalent capacitance value that is expected to be presented by the DC bus capacitor;

a detecting step, detecting a DC bus voltage of the DC bus;

a calculating step, calculating an expected value of a DC bus current of the DC bus based on the virtual DC bus capacitance value and the DC bus voltage; and

an adjusting step, adjusting the DC bus current, such that the DC bus current reaches the expected value and thus the DC bus capacitor presents to be equivalent to the virtual DC bus capacitance value.

2. The method of controlling an electrical power system according to claim 1 , wherein the electrical power system further comprises an energy storage module connected in parallel with the DC bus to store electrical energy provided by the DC bus or provide electrical energy to the DC bus, and

in the adjusting step, an active power charged from the DC bus to the energy storage module is controlled, which makes the energy storage module draw electrical energy from the DC bus so as to adjust the DC bus current; or

in the adjusting step, an active power discharged from the energy storage module to the DC bus is controlled, which makes the energy storage module provide electrical energy to the DC bus so as to adjust the DC bus current.

3. The method of controlling an electrical power system according to claim 2 , wherein the energy storage module comprises an energy storage element and a charging/discharging unit,

in the detecting step, the DC bus current and a charging/discharging current of the charging/discharging unit are further detected,

in the calculating step, the DC bus current is further subtracted from the expected value of the DC bus current to obtain a virtual current value, and

in the adjusting step, a closed-loop control is performed on the charging/discharging current to form switch signals, and the switch signals control operations of power elements in the charging/discharging unit to adjust the charging/discharging current, such that the charging/discharging current is equal to the virtual current value and thus the DC bus current reaches the expected value.

4. The method of controlling an electrical power system according to claim 1 , wherein the electrical power system further comprises a generator-side power converter and a grid-side power converter, and the DC bus capacitor is connected between the generator-side power converter and the grid-side power converter through the DC bus, and

in the adjusting step, an active current between the generator-side power converter and the DC bus is controlled, which makes the generator-side power converter draw electrical energy from the DC bus or provide electrical energy to the DC bus, so as to adjust the DC bus current.

5. The method of controlling an electrical power system according to claim 4 , wherein

in the detecting step, an AC side voltage of the generator-side power converter and an AC side current of the generator-side power converter are further detected,

in the calculating step, a coordinate transformation is further performed on the AC side voltage and the AC side current to obtain the active current and a reference value of the active current, and

in the adjusting step, switch signals are formed by performing a closed-loop control on the active current, and the switch signals control operations of power elements in the generator-side power converter to adjust the active current, such that the active current reaches the reference value of the active current and thus the DC bus current reaches the expected value of the DC bus current.

6. The method of controlling an electrical power system according to claim 5 , wherein the active current has a proportional relationship with the DC bus current, the reference value of the active current has the proportional relationship with the expected value, the proportional relationship is obtained by the coordinate transformation, and in the calculating step, the active current is calculated according to the proportional relationship and the DC bus current, and the reference value is calculated according to the proportional relationship and the expected value.

7. The method of controlling an electrical power system according to claim 1 , wherein the electrical power system further comprises a doubly-fed wind generator, a generator-side power converter, a grid-side power converter and a rectifier circuit, a DC side of the rectifier circuit is connected in parallel to the DC bus capacitor, and an AC side of the rectifier circuit is connected between a stator winding of the doubly-fed wind power generator and a power grid, and

in the adjusting step, by controlling an active current between the rectifier circuit and the DC bus is controlled, which makes the rectifier circuit draw electrical energy from the DC bus or provide electrical energy to the DC bus, so as to adjust the DC bus current.

8. The method of controlling an electrical power system according to claim 7 , wherein

in the detecting step, an AC side voltage of the rectifier circuit and an AC side current of the rectifier circuit are further detected,

in the calculating step, a coordinate transformation is performed on the AC side voltage and the AC side current, to obtain the active current and a reference value of the active current, and

in the adjusting step, switch signals are formed by performing a closed-loop control on the active current, and the switch signals control operations of power elements in the rectifier circuit to adjust the active current, such that the active current reaches the reference value of the active current and thus the DC bus current reaches the expected value.

9. The method of controlling an electrical power system according to claim 8 , wherein the active current has a proportional relationship with the DC bus current, the reference value of the active current has the proportional relationship with the expected value, the proportional relationship is obtained by the coordinate transformation, and in the calculating step, the active current is calculated according to the proportional relationship and the DC bus current, and the reference value is calculated according to the proportional relationship and the expected value.

10. The method of controlling an electrical power system according to claim 7 , wherein the electrical power system further comprises an energy storage module connected in parallel with the DC bus to store electrical energy provided by the DC bus or provide electrical energy to the DC bus, and

in the adjusting step, an active power charged from the DC bus to the energy storage module is controlled, which makes the energy storage module draw electrical energy from the DC bus so as to adjust the DC bus current;

or in the adjusting step, an active power discharged from the energy storage module to the DC bus is controlled, which makes the energy storage module provide electrical energy to the DC bus so as to adjust the DC bus current.

11. An apparatus of controlling an electrical power system, wherein the electrical power system comprises: a DC bus and a DC bus capacitor connected to the DC bus, and the apparatus comprises:

a setting module, configured to receive a virtual DC bus capacitance value of the DC bus capacitor, wherein the virtual DC bus capacitance value of the DC bus capacitor is an equivalent capacitance value that is expected to be presented by the DC bus capacitor;

a detecting module, configured to detect a DC bus voltage of the DC bus;

a calculating module, configured to calculate an expected value of a DC bus current of the DC bus based on the virtual DC bus capacitance value and the DC bus voltage; and

an adjusting module, configured to adjust the DC bus current, such that the DC bus current reaches the expected value and thus the DC bus capacitor presents to be equivalent to the virtual DC bus capacitance value.

12. The apparatus of controlling an electrical power system according to claim 11 , wherein the electrical power system further comprises an energy storage module connected in parallel with the DC bus to store electrical energy provided by the DC bus or provide electrical energy to the DC bus, and

the adjusting module is configured to control an active power charged from the DC bus to the energy storage module, which makes the energy storage module draw electrical energy from the DC bus so as to adjust the DC bus current; or

the adjusting module is configured to control an active power discharged from the energy storage module to the DC bus, which makes the energy storage module provide electrical energy to the DC bus so as to adjust the DC bus current.

13. The apparatus of controlling an electrical power system according to claim 12 , wherein the energy storage module comprises an energy storage element and a charging/discharging unit,

the detecting module further detects the DC bus current and a charging/discharging current of the charging/discharging unit,

the calculating module subtracts the DC bus current from the expected value of the DC bus current to obtain a virtual current value, and

the adjusting module performs a closed-loop control on the charging/discharging current to form switch signals, and the switch signals control operations of power elements in the charging/discharging unit to adjust the charging/discharging current, such that the charging/discharging current is equal to the virtual current value and thus the DC bus current reaches the expected value.

14. The apparatus of controlling an electrical power system according to claim 11 , wherein the electrical power system further comprises a generator-side power converter and a grid-side power converter, and the DC bus capacitor is connected between the generator-side power converter and the grid-side power converter through the DC bus, and

the adjusting module controls an active current between the generator-side power converter and the DC bus, which makes the generator-side power converter draw electrical energy from the DC bus or provides electrical energy to the DC bus, so as to adjust the DC bus current.

15. The apparatus of controlling an electrical power system according to claim 14 , wherein

the detecting module further detects an AC side voltage of the generator-side power converter and an AC side current of the generator-side power converter,

the calculating module performs a coordinate transformation on the AC side voltage and the AC side current to obtain the active current and a reference value of the active current, and

the adjusting module performs a closed-loop control on the active current to form switch signals, and the switch signals control operations of power elements in the generator-side power converter to adjust the active current, such that the active current reaches the reference value of the active current and thus the DC bus current reaches the expected value of the DC bus current.

16. The apparatus of controlling an electrical power system according to claim 15 , wherein the active current has a proportional relationship with the DC bus current, the reference value of the active current has the proportional relationship with the expected value, the proportional relationship is obtained by the coordinate transformation, and the calculating module calculates the active current according to the proportional relationship and the DC bus current, and the reference value according to the proportional relationship and the expected value.

17. The apparatus of controlling an electrical power system according to claim 11 , wherein the electrical power system further comprises a doubly-fed wind generator, a generator-side power converter, a grid-side power converter and a rectifier circuit, a DC side of the rectifier circuit is connected in parallel to the DC bus capacitor, and an AC side of the rectifier circuit is connected between a stator winding of the doubly-fed wind power generator and a power grid, and

the adjusting module controls an active current between the rectifier circuit and the DC bus, which makes the rectifier circuit draw electrical energy from the DC bus or provide electrical energy to the DC bus, so as to adjust the DC bus current.

18. The apparatus of controlling an electrical power system according to claim 17 , wherein

the detecting module further detects an AC side voltage of the rectifier circuit and an AC side current of the rectifier circuit,

the calculating module performs a coordinate transformation on the AC side voltage and the AC side current, to obtain the active current and a reference value of the active current, and

the adjusting module performs a closed-loop control on the active current to form switch signals, and the switch signals control operations of power elements in the rectifier circuit to adjust the active current, such that the active current reaches the reference value of the active current and thus the DC bus current reaches the expected value.

19. The apparatus of controlling an electrical power system according to claim 18 , wherein the active current has a proportional relationship with the DC bus current, the reference value of the active current has the proportional relationship with the expected value, the proportional relationship is obtained by the coordinate transformation, and the calculating module calculates the active current according to the proportional relationship and the DC bus current, and the reference value according to the proportional relationship and the expected value.

20. The apparatus of controlling an electrical power system according to claim 17 , wherein the electrical power system further comprises an energy storage module connected in parallel with the DC bus to store electrical energy provided by the DC bus or provide electrical energy to the DC bus, and

the adjusting module controls an active power charged from the DC bus to the energy storage module which makes the energy storage module draw electrical energy from the DC bus so as to adjust the DC bus current; or

the adjusting module controls an active power discharged from the energy storage module to the DC bus, which makes the energy storage module provide electrical energy to the DC bus so as to adjust the DC bus current.