Control system for distributed power generation, conversion, and storage system

• US 20060017328A1
• Filed: 04/14/2005
• Published: 01/26/2006
• Est. Priority Date: 02/10/2003
• Status: Abandoned Application

• Current Assignee: Jan Henrik Bryde
• Original Assignee: Jan Henrik Bryde
• Inventors: Bryde, Jan Henrik
• Application Number:
  US11/106,925
• Publication Number:
  US 20060017328A1
• Time in Patent Office: Days
• US Class Current: 307/64
• CPC Class Codes: H02J 9/061 for DC powered loads
• CPC Class Codes: H02J 9/062 for AC powered loads
• CPC Class Codes: H02J 9/08 requiring starting of a prime-mover

Abstract

A distributed power generating system enables very rapid and reliable start-up of an engine used to generate back-up power, thereby substantially reducing the need for stored power. More particularly, the distributed power generating system comprises a power bus electrically coupled to commercial power and to a load, an engine comprising a rotatable shaft, a starter/generator operatively coupled to the shaft of the engine and electrically coupled to the power bus, and a temporary storage device electrically coupled to the power bus. The distributed power generating system further comprises a control system adapted to detect a failure of the commercial power and cause the starter/generator to start the engine from a standstill condition. The control system provides the starter/generator with an initial voltage vector selected to rapidly bring the engine to an operational speed sustainable by the engine alone. The temporary storage device supplies electrical power to the power bus for delivery to the load and for powering the starter/generator until the engine reaches the operational speed, whereupon the control system causes the starter/generator to take over supply of electrical power to the power bus for delivery to the load. The control system starts the engine upon detection of a voltage on the power bus below a predetermined lower limit. After the engine has started, the control system monitors speed of the engine to determine whether the operational speed is reached. The control system terminates operation of the engine upon detection of a voltage on the power bus above a predetermined upper limit.

Claims

1. A distributed power generating system, comprising:

a power bus electrically coupled to commercial power and to a load;

an engine comprising a rotatable shaft;

a starter/generator operatively coupled to the shaft of the engine and electrically coupled to said power bus, the starter/generator having a short time torque capability higher than the rated torque of the engine and starter/generator;

a temporary storage device electrically coupled to said power bus; and

a control system adapted to detect a failure of the commercial power and cause the starter/generator to start the engine from a standstill condition with an initial voltage vector selected to rapidly bring the engine to an operational speed sustainable by the engine alone, said temporary storage device supplying electrical power to said power bus for delivery to said load and for powering said starter/generator until said engine reaches the operational speed, whereupon said control system causes said starter/generator to take over supply of electrical power to said power bus for delivery to said load.

2. The distributed power generating system of claim 1, wherein the starter/generator further comprises a rotor and a stator, the stator including a plurality of phase windings, the control system identifying an initial position of said rotor relative to said stator and selecting said voltage vector to provide maximum torque to said rotor.

3. The distributed power generating system of claim 2, wherein the control system measures self-inductance of each said phase winding of said stator.

4. The distributed power generating system of claim 3, wherein the control system estimates an angle of self-inductance of said stator based on said self-inductance inductance of each said phase winding.

5. The distributed power generating system of claim 4, wherein the control system estimates said angle of self-inductance of said stator in accordance with the following equation:

$2<br><br>\mathrm{\theta <br><br>}=-{\tan }^{-1}\left(\frac{\frac{\sqrt{3}}{2}<br><br>\mathrm{\Delta <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>t_b-\frac{\sqrt{3}}{2}<br><br>\mathrm{\Delta <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>t_c}{\mathrm{\Delta <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>t_a-\frac{1}{2}<br><br>\mathrm{\Delta <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>t_b-\frac{1}{2}<br><br>\mathrm{\Delta <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>t_c}\right)$

wherein, θ

is the estimated angle of self-inductance of said stator, Δ

t_a is the time for current in phase A of said stator to fall from a positive selected level to a negative selected level, Δ

t_b is the time for current in phase B of said stator to fall from said positive selected level to said negative selected level, and Δ

t_c, is the time for current in phase C of said stator to fall from said positive selected level to said negative selected level.

6. The distributed power generating system of claim 4, wherein the control system corrects the estimated angle of self-inductance of said stator.

7. The distributed power generating system of claim 1, wherein the control system starts the engine upon detection of a voltage on said power bus below a predetermined lower limit.

8. The distributed power generating system of claim 1, wherein the control system monitors speed of said engine to determine whether said operational speed is reached.

9. The distributed power generating system of claim 1, wherein the control system terminates operation of said engine upon detection of a voltage on said power bus above a predetermined upper limit.

10. The distributed power generating system of claim 1, wherein the temporary energy storage device further comprises at least one capacitor.

11. The distributed power generating system of claim 1, wherein said engine reaches the operational speed in less than one second.

12. The distributed power generating system of claim 1, wherein said engine reaches the operational speed in less than 0.2 second.

13. A method for distributing power to a load coupled to a power bus, comprising:

supplying commercial power to said load over said power bus;

detecting a fault of said commercial power, and in the event of a fault;

supplying stored power to said load and to a starter/generator operatively coupled to an engine, the starter/generator having a short time torque capability higher than the rated torque of the engine and starter/generator;

starting the engine from a standstill condition by applying an initial voltage vector selected to rapidly bring the engine to an operational speed sustainable by the engine alone; and

supplying generated power to said load from said starter/generator after said engine reaches said operational speed.

14. The method of claim 13, wherein the starter/generator further comprises a rotor and a stator, the stator including a plurality of phase windings, the step of starting the engine further comprises identifying an initial position of said rotor relative to said stator and selecting said initial voltage vector to provide maximum torque to said rotor.

15. The method of claim 14, wherein the step of identifying an initial position further comprises measuring self-inductance of each said phase winding of said stator.

16. The method of claim 15, wherein the step of identifying an initial position further comprises estimating an angle of self-inductance of said stator based on said self-inductance of each said phase winding.

17. The method of claim 16, wherein the step of estimating said angle of self-inductance of said stator is performed in accordance with the following equation:

$2<br><br>\mathrm{\theta <br><br>}=-{\tan }^{-1}\left(\frac{\frac{\sqrt{3}}{2}<br><br>\mathrm{\Delta <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>t_b-\frac{\sqrt{3}}{2}<br><br>\mathrm{\Delta <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>t_c}{\mathrm{\Delta <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>t_a-\frac{1}{2}<br><br>\mathrm{\Delta <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>t_b-\frac{1}{2}<br><br>\mathrm{\Delta <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>t_c}\right)$

wherein, θ

is the estimated angle of self-inductance of said stator, Δ

t_a is the time for current in phase A of said stator to fall from a positive selected level to a negative selected level, Δ

t_b is the time for current in phase B of said stator to fall from said positive selected level to said negative selected level, and Δ

t_c is the time for current in phase C of said stator to fall from said positive selected level to said negative selected level.

18. The method of claim 16, wherein the step of estimating said angle of self-inductance further comprises correcting the estimated angle of self-inductance.

19. The method of claim 13, wherein the step of detecting a fault of said commercial power further comprises detecting a voltage on said power bus below a predetermined lower limit.

20. The method of claim 13, wherein the step of starting said engine further comprises monitoring speed of said engine to determine whether said operational speed is reached.

21. The method of claim 13, further comprising terminating operation of said engine upon detection of a voltage on said power bus above a predetermined upper limit.