Microprocessor based integrated generator set controller apparatus and method

• US 5,006,781 A
• Filed: 05/09/1988
• Issued: 04/09/1991
• Est. Priority Date: 05/09/1988
• Status: Expired due to Term

• Current Assignee: Cummins PowerGen IP, Inc. (Cummins Incorporated)
• Original Assignee: ONAN Corporation (Cummins Incorporated)
• Inventors: Koenig, David J., Schultz, Mark H.
• Primary Examiner(s): Hickey, R. J.
• Application Number:
  US07/191,560
• Time in Patent Office: 1,065 Days
• Field of Search: 322/25, 322/28, 322/15, 307/87
• US Class Current: 322/25
• CPC Class Codes: H02P 9/04 Control effected upon non-electric prime mover and dependent upon electric output value of the generator
• CPC Class Codes: H02P 9/30 using semiconductor devices

Abstract

An electrical generator system integrated controller device utilizing PID control and capable of regulating voltage or current, and frequency simultaneously. The device utilizes a micro-controller (30.1) to monitor the engine generator set (20), then determines the appropriate signal to deliver to the electrical generator set (20) to regulate the engine throttle (21) and the generator (22) field windings. The micro-controller (30.1) also provides for real and reactive load sharing with additional generator sets (40) while also providing for an integrated circuit interrupter module (500) to open the line from the generator (22) to the load bus (42). Additionally, serial communications (34) are provided as well as displays (35), meters (37), and operator input (36). Finally, the permissive paralleling module (700) provides that the engine electrical generator set (20) will not be allowed to be connected to the load bus (42) until standards of voltage and phase have been achieved for a set period of time.

Claims

1. A control system for controlling the voltage and current output signals of a generator, comprising:

(a) first sensing means, operatively connected to the generator, for sensing the voltage and current output signals of the generator and for providing a sensed voltage signal and a sensed current signal; and

(b) first control means, operatively connected to the generator and to said first sensing means to receive said sensed voltage and current signals, for selectively controlling the voltage or current output signals of the generator in response to the magnitude of the current output signal, said first control means controlling the voltage or current signals according to a control process equation having coefficients, wherein the coefficients of said control process equation are changed according to whether the voltage or current signals are being controlled.

2. The control system in accordance with claim 1, wherein said first control means selectively control the voltage and current output signals in real time.

3. The control system in accordance with claim 2, wherein said first control means controls the voltage output signal, selectively controlling the current output signal when the magnitude of the current output signal exceeds a first current threshold level.

4. The control system in accordance with claim 3, wherein said first control means selectively returns to control the voltage output signal when the magnitude of the current output signal is less than a second current threshold level, whereby hysteresis is added to said first control means.

5. The control system in accordance with claim 4, wherein said first control means further includes a microprocessor.

6. The control system of claim 1, wherein said control process equation is implemented by the equations:

space="preserve" listing-type="equation">A=(K.sub.1)(V.sub.1)

space="preserve" listing-type="equation">B=(K.sub.2)(X.sub.2)

space="preserve" listing-type="equation">C=(K.sub.3)(X.sub.2)

space="preserve" listing-type="equation">D=(K.sub.4)(X.sub.2)

space="preserve" listing-type="equation">X.sub.2 =X.sub.1 +A

space="preserve" listing-type="equation">X.sub.2 =A+B+C

space="preserve" listing-type="equation">U.sub.1 =A+B-D

wherein A, B, C, D, X₁ and X₂ are six variables defined to store intermediate results, U₁ equals the output of said control process equation and K₁, K₂, K₃ and K₄ comprise a set of control process equation coefficients.

7. The generator set of claim 1, wherein said control process equation is implemented by the equations:

space="preserve" listing-type="equation">A=(K.sub.1)(V.sub.1)

space="preserve" listing-type="equation">B=(K.sub.2)(X.sub.2)

space="preserve" listing-type="equation">C=(K.sub.3)(X.sub.2)

space="preserve" listing-type="equation">D=(K.sub.4)(X.sub.2)

space="preserve" listing-type="equation">X.sub.1 =X.sub.1 +A

space="preserve" listing-type="equation">X.sub.2 =A+B+C

space="preserve" listing-type="equation">U.sub.1 =A+B-D

wherein A, B, C, D, X₁ and X₂ are six variables defined to store intermediate results, U₁ equals the output of said control process equation and K₁, K₂, K₃ and K₄ comprise a set of control process equation coefficients.

8. The method of claim 1, wherein said controlling step comprises implementing said control process equation with the equations:

space="preserve" listing-type="equation">A=(K.sub.1)(V.sub.1)

space="preserve" listing-type="equation">B=(K.sub.2)(X.sub.2)

space="preserve" listing-type="equation">C=(K.sub.3)(X.sub.2)

space="preserve" listing-type="equation">D=(K.sub.4)(X.sub.2)

space="preserve" listing-type="equation">X.sub.1 =X.sub.1 +A

space="preserve" listing-type="equation">X.sub.2 =A+B+C

space="preserve" listing-type="equation">U.sub.1 =A+B-D

wherein A, B, C, D, X₁ and X₂ are six variables defined to store intermediate results, U₁ equals the output of the algorithm and K₁, K₂, K₃ and K₄ comprise a set of control process equation coefficients.

17. The control system in accordance with claim 7, wherein said first and second control means includes a microprocessor and wherein said microprocessor ramps the rotational speed and the output voltage signal when going from an inhibited to an operative state.

9. A control system for controlling the voltage and current output signals of a generator, comprising:

(a) first sensing means, operatively connected to the generator, for sensing the voltage and curent output signals of the generator and for providing a sensed voltage signal and a sensed current signal; and

(b) first control means, operatively connected to the generator and to said first sensing means to receive said sensed voltage and current signals, for selectively controlling the voltage or current output signals of the generator in response to the magnitude of the current output signal, wherein said first control means controls the voltage output signal and selectively controls the current output signal when the magnitude of the current output signal exceeds a first current threshold level and wherein said first control means selectively returns to control the voltage output signal when the magnitude of the current output signal is less than a second current threshold level, whereby hysteresis is added to said first control means, said first control means comprises a microprocessor including;

(i) control equation memory means for storing a control process equation;

(ii) co-efficient memory means for storing a plurality of co-efficient sets corresponding to selectively controlling the voltage output signal, defining a first set of co-efficients, and for controlling the current output signal, defining a second set of co-efficients;

(iii) data processing means including;

(A) means for computing said control process equation where said sensed voltage output signal is the input;

(B) means for changing the coefficients of said control process equation to said second set when the magnitude of the current output signal exceeds said first current threshold level;

(C) means for computing said control process equation where said sensed current output signal is the input; and

(D) means for changing the coefficients of said control process equation to said first set when the magnitude of the current output signal is less than said second current threshold level.

10. A generator set, of the type having a generator powered by a prime mover for connection to a load conductor, comprising:

(a) a generator;

(b) prime mover means cooperatively connected to said generator for transmitting rotational energy to said generator;

(c) first sensing means, operatively connected to said generator, for sensing the voltage and current output signals of said generator and for providing a sensed voltage signal and a sensed current signal;

(d) first control means, operatively connected to said generator and to said first sensing means to receive said sensed voltage and current signals, for selectively controlling the voltage or current output signals of said generator in response to the magnitude of the current output signal, said first control means operatively controlling the voltage or current output signals in accordance with a control process equation, wherein a first set of coefficients are utilized when controlling voltage and a second set are utilized when controlling current;

(e) second sensing means, cooperatively connected to said prime mover means, for providing a sensed rotational speed signal of said prime mover means corresponding to the output waveform frequency of said generator; and

(f) second control means, cooperatively connected to said prime mover means and to said second sensing means to receive said sensed rotational speed signal, for controlling the rotational speed of said prime mover means, whereby the generator output waveform frequency and either the current output signal or voltage output signal are simultaneously controlled.

11. The generator set of claim 10, further comprising synchronization means, cooperatively connected to said first sensing means, said second control means, and the load conductor, for synchronizing the generator output waveform to a waveform present on the load conductor.

12. The generator set of claim 11, wherein said synchronization means includes;

(a) waveform detection means, cooperatively connected to said generator and the load conductor, for providing signals responsive to the zero crossing points of said generator and load conductor waveforms;

(b) duty cycle means, cooperatively connected to said waveform detection means, for establishing a pulse train signal having a duty cycle proportional to the offset between the generator waveform and the load conductor waveform; and

(c) averaging means cooperatively connected to said duty cycle means and said second control means, for providing an average voltage level of said established pulse train signal to said second control means, wherein said second control means adjusts the rotational speed of the said prime mover to synchronize the generator output waveform to the waveform present on the load conductor using proportional integral control.

13. The generator set of claim 12, wherein said first and second control means includes a microprocessor.

14. The generator set of claim 10, wherein said first and second control means includes a microprocessor.

15. The generator set of claim 14, wherein said generator is connected to the load conductor and further includes:

(a) a contactor in line between said generator and the load conductor, said contactor cooperatively connected to said microprocessor; and

(b) third sensing means, cooperatively connected to the load conductor, for sensing the voltage on the load conductor and for providing a sensed voltage signal, wherein said microprocessor establishes said contactor in an open position until permissive paralleling conditions have been satisfied, wherein permissive paralleling conditions include synchronization to a waveform present on the load bus.

16. The generator set of claim 10, wherein said first and second control means includes a microprocessor, and further including power sharing means, cooperatively connected to said microprocessor, for generating a signal representative of the power being delivered by the generator and for receiving a power signal indicative of the power being delivered by a second generator connected to the load bus, wherein the microprocessor receives said created power signal and tends to equalize said power delivered by said generator and the second generator by adjusting the speed of said prime mover or excitation of said generator.

18. A method of automatically controlling the voltage and current output system of a generator, comprising the steps of:

(a) sensing the voltage and current output signals of the generator;

(b) providing a sensed voltage signal and a sensed current signal;

(c) receiving said sensed voltage and current signal;

(d) controlling selectively the voltage or current output signals of the generator in response to the magnitude of the current output signal utilizing a control process equation having coefficients; and

(e) changing the coefficients of the control process equation based upon whether voltage or current is being controlled.