Electricity: single generator systems – Automatic control of generator or driving means – Antihunting or rate of change
Reexamination Certificate
1999-06-18
2001-01-16
Ponomarenko, Nicholas (Department: 2834)
Electricity: single generator systems
Automatic control of generator or driving means
Antihunting or rate of change
C322S028000, C322S036000, C322S045000
Reexamination Certificate
active
06175217
ABSTRACT:
BACKGROUND OF THE INVENTION
THIS invention relates to generator apparatus which can be used to supply loads which vary substantially with time.
In conventional electric generator sets an engine or other prime mover drives a synchronous alternator at a nominally constant speed which is calculated to provide an AC electrical output of the correct frequency. In practice, the engine speed does not remain exactly constant, with a resultant undesirable variation in the frequency of the electrical output of such generator sets.
In order to supply maximum load demand, such a generator set must be sized accordingly, which can be very wasteful due to the fact that the average load may typically be only 20% of the peak load. There are numerous applications, such as welding, battery charging and the starting/operation of electric motors where load demand may vary greatly, with only intermittent heavy loading of the generator set. Thus, it is desirable that a generator set which is used in such applications be able to cope efficiently with light load conditions.
Variable speed generator sets have been proposed (see, for example, U.S. Pat. No. 5,563,802 of Plahn et al) which respond to variations in load demand by varying the speed of the engine/generator, and which utilise batteries to supply the load under low-load conditions. However, known systems of this kind have various limitations, including a limited engine speed operating range, poor battery life due to onerous duty cycles, and poor performance under adverse load conditions.
It is an object of the invention to provide hybrid generator apparatus which can cope with substantial variations in load while also operating efficiently.
SUMMARY OF THE INVENTION
According to the invention power supply apparatus comprises:
at least one controllable source arranged to provide a variable voltage and/or current electrical output;
decoupling converter means for generating an intermediate DC output from the variable voltage and/or current electrical output of said at least one controllable source which is substantially independent of variations in the electrical output of the source;
output means for generating an AC or DC output to supply a time varying load from the intermediate DC output;
sensor means for monitoring the voltage and/or current of said at least one controllable source and the intermediate DC output and for generating output signals corresponding thereto; and
control means responsive to the output signals to control the operation of said at least one controllable source, to dynamically vary the power output of the source and thereby to supply the power required by the time varying load.
The controllable source may comprise a fuel cell or another device such as a hydro-electric generator, a wind turbine, a gas turbine/generator or any other device which generates an electrical output from a non-electrical input.
Alternatively the controllable source may comprise an engine and a generator which provides a variable voltage output to the decoupling converter means.
Preferably, the generator is an AC generator which provides a variable voltage, variable frequency AC output to the decoupling converter means, the apparatus including rectifier means for rectifying the AC output of the generator and the decoupling converter means comprising a DC to DC converter for converting the rectified AC output to an intermediate DC output having a voltage which is controlled with respect to a reference voltage.
The control means may include sensor means arranged to monitor the loading of the intermediate DC output of the converter means and/or the controllable source, and to increase the speed of the engine when the loading exceeds a predetermined value.
In one embodiment, the control means operates to maintain the current drawn from the controllable source at a predetermined level or within a predetermined range, the sensor means comprising a voltage sensor arranged to monitor the output voltage at the intermediate DC output of the converter means, and to increase the speed of the engine to increase the power supplied to the converter means when the voltage of the intermediate DC output drops below a first voltage threshold.
In another embodiment, the control means operates to maintain the voltage of the intermediate DC output substantially constant, the sensor means comprising a current sensor arranged to monitor the current drawn from the controllable source and to increase the speed of the engine to increase the power supplied to the convertor means when the current drawn from the controllable source exceeds a first current threshold.
The apparatus may include at least first energy storage means arranged to be charged from the intermediate DC output and to discharge energy into the intermediate DC output when the voltage of the intermediate DC output falls below a nominal value.
Alternatively or in addition, the apparatus may include auxiliary load control means arranged to detect the connection of an onerous auxiliary load to the output means and to control the supply of power to the auxiliary load, thereby to prevent excessive loading to the output means.
Preferably, the apparatus includes at least second energy storage means, a charge circuit arranged to charge the second energy storage means from the intermediate DC output of the converter means, and a discharge circuit arranged to discharge the second energy storage means in parallel with the first energy storage means when the intermediate DC output voltage drops below a second voltage threshold below the first voltage threshold.
In one embodiment, the apparatus includes third energy storage means, a charge circuit arranged to charge the third energy storage means from an electrical source, and auxiliary converter means arranged to discharge the third energy storage means in parallel with the first and second energy storage means after the second energy storage means has discharged at least partially.
The first and second energy storage devices are preferably capacitors, and the third energy storage device is preferably a battery.
The apparatus may include a speed sensor for monitoring the speed of the engine/generator and for generating a speed output signal related thereto, and function generator means for generating a power signal from the speed output signal, the power signal being representative of a power/speed characteristic of the engine and being utilised by the control means to optimise the operation of the engine.
The apparatus may further include ambient pressure and temperature sensors for monitoring ambient pressure and temperature and for generating respective pressure and temperature output signals, and may further include respective pressure and temperature function generators for generating outputs comprising engine derating characteristics to compensate for variations in ambient operating pressure and temperature.
The apparatus may also include an exhaust temperature sensor arranged to monitor the engine exhaust temperature and to generate an exhaust temperature output signal, an exhaust temperature function generator for generating an exhaust temperature/speed-load characteristic signal from the speed output signal, and a controller for generating an error signal from the difference between the exhaust temperature output signal and the exhaust temperature/speed-load characteristic signal, thereby to compensate for factors affecting the engine exhaust temperature.
REFERENCES:
patent: 4697090 (1987-09-01), Baker et al.
patent: 4908565 (1990-03-01), Cook et al.
patent: 5015941 (1991-05-01), Dhyanchand
patent: 5198698 (1993-03-01), Paul et al.
patent: 5493200 (1996-02-01), Rozman et al.
patent: 5495162 (1996-02-01), Rozman et al.
patent: 5559685 (1996-09-01), Lauw et al.
patent: 5563802 (1996-10-01), Plahn et al.
patent: 5942818 (1999-08-01), Satoh et al.
patent: 5955809 (1999-09-01), Shah
Da Ponte Manuel Dos Santos
Grzesiak Lech
Koczara Wlodzimierz
Niedzialkowski Andrzej
Pospiech Pawel
Blakely & Sokoloff, Taylor & Zafman
Da Ponte Manuel Dos Santos
Ponomarenko Nicholas
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