Hybrid synchronization phase angle generation method

• US 20030222507A1
• Filed: 05/31/2002
• Published: 12/04/2003
• Est. Priority Date: 05/31/2002
• Status: Active Grant

• Current Assignee: Siemens VDO Automotive Corporation (Siemens AG)
• Original Assignee: Ballard Power Systems Corporation (Siemens AG)
• Inventors: Deng, Doug D.
• Granted Patent: US 6,919,650 B2
• Time in Patent Office: Days
• US Class Current: 307/87
• CPC Class Codes: H02J 3/40 Synchronising a generator for connection to a network or to another generator

Abstract

A hybrid use of a phase-locked-loop controller and a microprocessor-based controller to synchronize the phase angles of a three-phase AC power source, such as a static power converter, with those of a three-phase power grid. The phase-angle synchronization may enable the AC power source to be safely connected to the power grid to provide additional power capacity.

Claims

1. A synchronization phase angle generator for synchronizing an AC power source with a power grid, comprising:

a phase locked loop (PLL) controller which receives at least one voltage of the power grid and determines a frequency and a phase angle of the at least one voltage of the power grid; and

a microprocessor-based controller which receives as input the frequency and the phase angle of the at least one voltage of the power grid and determines a phase angle of at least one output voltage of the AC power source.

2. The synchronization phase angle generator of claim 1 wherein the power grid is a three-phase power grid with the at least one voltage of the power grid comprising a first phase voltage, a second phase voltage, and a third phase voltage, and wherein each of the first, the second and the third phase voltages has a magnitude and a phase angle.

3. The synchronization phase angle generator of claim 2 wherein the phase angle of the at least one voltage of the power grid is the phase angle of the first phase voltage of the power grid, and the phase angles of the second phase voltage and the third phase voltage of the grid are both 120°

from the phase angle of the first phase voltage.

4. The synchronization phase angle generator of claim 1 wherein the determined phase angle of the at least one output voltage of the AC power source matches with the determined phase angle of the at least one phase voltage of the power grid, and the AC power source supplies the at least one output voltage with the matched phase angle to the power grid.

5. The synchronization phase angle generator of claim 1 wherein the PLL controller comprises:

a transformation circuit module which receives the at least one voltage of the power grid and a feedback of the phase angle of the at least one voltage of the power grid and generates a first value based on a transformation of the at least one voltage of the power grid and the phase angle of the at least one voltage of the power grid.

6. The synchronization phase angle generator of claim 5 wherein the PLL controller further comprises:

a proportional-integral (PI) regulator that determines the frequency of the at least one voltage of the power grid based on the generated first value.

7. The synchronization phase angle generator of claim 6 wherein the PLL controller further comprises:

an integrator that determines the phase angle of the at least one voltage of the power grid based on the frequency of the at least one voltage of the power grid.

8. The synchronization phase angle generator of claim 1 wherein the microprocessor-based controller comprises:

a first circuit module which generates an initial value for the phase angle of the at least one output voltage of the AC power source based on the phase angle of the at least one voltage of the power grid.

9. The synchronization phase angle generator of claim 8 wherein the microprocessor-based controller further comprises:

a second circuit module which generates an increment value for the phase angle of the at least one output voltage of the AC power source over a predetermined time period based on the frequency of the at least one voltage of the power grid.

10. The synchronization phase angle generator of claim 9 wherein the predetermined time period is the sampling time period of the microprocessor-based controller.

11. The synchronization phase angle generator of claim 9 wherein the microprocessor-based controller further comprises:

a third circuit module which receives the generated initial value and increment value for the phase angle of the at least one output voltage of the AC power source and determines the phase angle of the at least one output voltage of the AC power source.

12. The synchronization phase angle generator of claim 11 wherein the phase angle of the at least one output voltage of the AC power source comprises digitally quantized values.

13. The synchronization phase angle generator of claim 1 wherein the AC power source is a static power converter.

14. A method for synchronizing a polyphase power grid with a polyphase AC power source (APS), comprising:

receiving a phase voltage of the polyphase power grid;

performing a phase-locked-loop (PLL) operation to derive and lock on to a phase angle of the power grid phase voltage;

generating a digitally quantized phase angle for an output phase voltage of the APS, wherein the generated phase angle of the APS output phase voltage is synchronized with the lock-on phase angle of the power grid phase voltage.

15. The method of claim 14 wherein receiving a phase voltage of the polyphase power grid comprises:

receiving a phase voltage of each of a first phase, a second phase, and a third phase of the polyphase power grid.

16. The method of claim 14 wherein performing a PLL operation comprises:

receiving a feedback of the phase angle of the power grid phase voltage;

performing a transformation on the received phase voltage and the feedback phase angle to generate a transformed value;

deriving a frequency of the power grid phase voltage; and

deriving and locking on to the phase angle of the power grid phase voltage based on the transformed value.

17. The method of claim 16 wherein generating a digitally quantized phase angle for an APS output phase voltage comprises:

generating an initial value for the digitally quantized phase angle based on the derived phase angle of the power grid phase voltage;

generating an increment value for the digitally quantized phase angle over a predetermined sampling time period based on the derived frequency of the power grid phase voltage; and

generating the digitally quantized phase angle for the APS output phase voltage based on the generated initial value and increment value.

18. The method of claim 17 wherein generating an initial value for the digitally quantized phase angle comprises:

detecting whether there is an abnormal operation of the phase angle of the power grid phase voltage; and

if the abnormal operation is detected, setting the initial value for the digitally quantized phase angle to zero.

19. The method of claim 17 wherein generating an increment value for the digitally quantized phase angle over a predetermined sampling time period comprises:

generating an increment value for each of a plurality of consecutive time steps, wherein one of the time steps is separated from the next one of the time steps by the predetermined sampling time period;

detecting whether there is an abnormal condition of the frequency of the power grid voltage; and

if the abnormal condition is detected, setting the incremental value for one of the time steps to the incremental value of a previous one of the time steps.

20. The method of claim 15 wherein performing a PLL operation comprises:

receiving a feedback of the phase angle of the power grid phase voltage; and

performing a transformation on the received three-phase voltages and the feedback phase angle to generate a transformed value, wherein the transformation is based on the following equation;

$T<br><br>\left(\mathrm{\gamma <br><br>}\right)=\mathrm{Va\_g}·<br><br>\mathrm{Sin}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\gamma <br><br>}+\mathrm{Vb\_g}·<br><br>\mathrm{Sin}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>}-\frac{2<br><br>\mathrm{\pi <br><br>}}{3}\right)+\mathrm{Vc\_g}·<br><br>\mathrm{Sin}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>}+\frac{2<br><br>\mathrm{\pi <br><br>}}{3}\right),$

wherein γ

represents the feedback phase angle, Va_g represents the first phase voltage of the power grid, Vb_g represents the second phase voltage of the power grid, and Vc_g represents the third phase voltage of the power grid.