POWER SYSTEM JUNCTION TEMPERATURE
CONTROL
BACKGROUND OF THE INVENTION
[0001] The field of the present disclosure relates generally to a
system and method of operating a power generating system to control a peak junction
temperature. More particularly, the present disclosure relates to photovoltaic (e.g.,
solar power) and wind (e.g., wind turbine) power generating systems, including a
controller that limits the peak junction temperature.
[0002] Typically, in power generation systems, the power produced
by the solar module and wind turbine is direct-current (DC) power which must be
converted to alternating current (AC) for export to the power grid. Typically,
converters include insulated gate bipolar transistors (IGBTs) or other power
semiconductors. The semiconductors typically operate within a normal range of
operating temperatures. IGBT junction temperatures are typically rated at either
125°C, 150°C, or 175°C maximum depending upon the type of IGBT. The
semiconductors have an upper limit junction temperature at which they may be
reliably operated. Exceeding the upper limit junction temperature of the
semiconductors may cause undesirable reductions in operating efficiency and/or
failure of the semiconductors.
[0003] Temperature increases at the semiconductor junctions may be
caused by a variety of factors. For example, air filters of cooling systems for the
semiconductors may become dirty/clogged thereby reducing an amount of cooling
medium available to cool the semiconductors. Other environmental factors, such as
high outdoor temperatures, high altitude, humidity levels, sunlight and the like may
also undesirably increase the operating temperature of the semiconductors. Operating
factors such as high output power of the converter and transient power events may
also increase the junction temperature of the semiconductors and the like.
Combinations of such factors may be applied simultaneously, causing more rapid and
sustained high junction temperatures.
[0004] Typically, when the junction temperature of the
semiconductors in the converter reaches an upper limit, a circuit breaker may be
utilized to trip (i.e., shut down) the converter to prevent a failure of the converter.
Further, operating the converters at high temperatures may undesirably reduce the life
of the converter. If the converter is shut down due to high junction temperatures, the
converter may remain in an off state until the semiconductor junction temperatures
have decreased to an acceptable level. Such shutting down of the converter is
typically undesirable because it may reduce or eliminate the ability for the power
generating system to supply electrical power.
BRIEF DESCRIPTION OF THE INVENTION
[0005] In one aspect, an electrical power generating system is
includes a power generating device, a power converter connected to the power
generating device, and an electrical controller connected to the power converter. The
electrical controller is configured to limit a peak junction temperature of the converter
by applying at least one junction temperature derating function.
[0006] In another aspect, a method of controlling a power converter
of an electrical power generating system includes sensing a temperature, applying at
least one junction temperature derating function that is based upon the sensed
temperature to limit the power output of the power converter and limiting the power
of the power converter until a predetermined condition is met.
[0007] In a further aspect, a non-transitory computer readable storage
medium storing program instructions for controlling a power converter of an electrical
power generating system include instructions for sensing a temperature using a
temperature sensing device, applying at least one junction temperature derating
function that is based upon on the sensed temperature to limit the power output of the
power converter and limiting the power of the power converter until a predetermined
condition is met.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] Fig. 1 is a block diagram of an exemplary embodiment of the
present disclosure.
[0009] Fig. 2 is a block diagram of a second embodiment of the
present disclosure.
[0010] Fig. 3 is a block diagram of a third embodiment of the present
disclosure.
[001 1] Fig. 4 is a chart of an exemplary junction temperature
derating function of the present disclosure.
DETAILED DESCRIPTION OF THE INVENTION
[0012] The methods and systems described herein facilitate
controlling a power converter of an electrical power generating system. The technical
effects of the methods and systems of the present disclosure provide the ability to
limit a peak junction temperature of the converter by applying one or more power
limiting factors derived by a junction temperature derating function.
[0013] Shown in Fig. 1 is a block diagram of an exemplary
embodiment of a control system of the present disclosure. The control system
includes a controller 100 connected to a power converter 102 of a power generation
system (not shown). In one embodiment, the controller 100 is connected to the power
converter 102 via a feedback loop arrangement or other arrangements that allow the
control system of the present disclosure to function as described herein.
[0014] During operation of power converter 102, the semiconductor
components (or other mechanical or electrical components) of power converter 102
generate heat. Power converter 102 has a maximum operating temperature 104 (Fig.
4) at which the power converter may reliably operate. In embodiments, maximum
operating temperature 104 is, for example, a predetermined temperature or a
temperature found experimentally to be the maximum operating temperature at which
power converter 102 operates reliably. Reliable operation as used herein, refers to
normal operating conditions at which no permanent substantial damage occurs to the
device. In one embodiment, the power converter 102 is operated with a margin
below the junction temperature rating. For example an IGBT rated at 125°C is
operated with IGBT junction temperatures at 90°C typical, leaving margin for line
surges and overloads, which cause the IGBT junction temperatures to increase
momentarily until the surge or overload ends. In another embodiment, the control
system includes an over-temperature warning indication at a temperature above the
margin and below the maximum junction temperature, for example, an overtemperature
warning is provided at 115°C and an over-temperature circuit trip is
triggered at 125°C. In other embodiments, maximum operating temperature 104 is a
temperature value associated with a junction temperature of a semiconductor of power
converter 102 or a maximum operating temperature of one or more other components
of power converter 102.
[0015] A temperature of power converter 102 is determined, for
example, by a temperature sensor 106 that contacts the power converter 102 or senses
the temperature of power converter 102 in a non-contact manner. Temperature sensor
106 outputs a temperature of power converter 102 to controller 100 as an input 108.
In one embodiment, the output temperature is a temperature of a single component or
multiple components. In other embodiments, the temperature sensor also senses an
ambient temperature and outputs the ambient temperature to controller 100.
Temperature sensor 106 may also sense and output any temperature that allows the
control system of the present disclosure to operate as described herein. In another
embodiment, if multiple temperatures are sensed by temperature sensor 106, a
maximum sensed temperature is output from temperature sensor 106 as input 108 to
controller 100.
[0016] Input 108 is transmitted to controller 100 and is used as an
input value for a derating function 110, such as a junction temperature derating
function. In one embodiment, derating function 100 is a unit function, for example,
with a range of values from 0.0 to 1.0 on the vertical axis. In embodiments, the
horizontal axis represents, for example, temperature values.
[0017] In one embodiment, derating function 110 is utilized to
calculate a system derating factor 112 (i.e., a vertical axis value) associated with input
108. As shown in Fig. 1, derating function 110 has a range of temperatures at which
factor 112 remains constant, and beyond which factor 112 is reduced. In one
embodiment, a factor value of 1.0 represents input 108 values associated with normal
operating temperatures of power converter 102.
[0018] Factor 112 is then used by controller 100 to control a power
output amount of power converter 102. In one embodiment, a factor of 1.0 is used to
control power converter 102 to operate at maximum power, and a factor of 0.0 is used
to control the power converter 102 to shut down, or operate at a minimum operating
power. In another embodiment, a factor of 0.5 is used to instruct power converter 102
to operate at 50% power. Factor 112 may be used to instruct power converter 102 to
operate at any power level that allows the control system of the present disclosure to
function as described herein.
[0019] In embodiments, factor 112 is directly input and used to
control power converter 102. In other embodiments, factor 112 is first transmitted to
and used in further calculations such as, for example, power/var limit calculations 114
and current limit calculations 116. In still other embodiments, output of power/var
limit calculations 114 and/or current limit calculations 116 is input and used to control
power converter 102 as factor 112.
[0020] Factor 112 thus may be used to control the power output of
power converter 102. For example, power converter 102 may initially operate at
100% power output. The temperature of the power converter 102 is sensed by
temperature sensor 106 and output to controller 100 as input 108. Controller 100
processes input 108 using derating function 110. If input 108 is within a normal
operating range of power converter 102, the calculated value of the derating factor
112 is 1.0, for example. Thus, power converter 102 will be instructed to continue
operating at 100% power output, for example.
[0021] However, if input 108 is outside of the normal operating
range of power converter 102 (i.e., a value to the right of the vertical dashed line
indicated in derating function 110), the derating factor is calculated to be less than
1.0. In one embodiment, if power converter 102 is operating at a high temperature at
or near the maximum operating temperature, input 108 is outside of the normal
operating range. Thus, derating function 110, using input 108, outputs a derating
factor 112 that is less than 1.0. The derating factor 112 is then used to instruct/control
power converter 102 to operate at a power level less than 100%.
[0022] In one embodiment, power converter 102 is instructed to
operate at the given power level until a predetermined condition is met, for example,
until a predetermined time has passed or until temperature sensor 106 senses that
power converter 102 is operating at a normal operating temperature. For example,
temperature sensor 106 may continuously or incrementally monitor the temperature of
power converter 102 and continuously or incrementally output the temperature to
controller 100 as input 108. Thus, power converter 102 may be controlled in real
time, or at discrete time intervals.
[0023] In one embodiment, power converter 102 is thus controlled to
operate at a reduced power level. For example, power converter 102 is controlled to
operate at a reduced power level according to a range of temperatures. The control
system of the present disclosure thus allows for the possibility of operating power
converter 102 at a reduced power level when power converter 102 is at a temperature
outside of the normal operating range, thereby avoiding unnecessary shut downs and
maximizing up-time of power converter 102.
[0024] Shown in Fig. 2 is a block diagram of a second exemplary
embodiment of a control system of the present disclosure utilizing a plurality of
derating functions. For example, controller 100, in one embodiment, includes a first
derating function 118 and a second derating function 120. First derating function 118
is supplied with a first input 122 that may be, for example, a temperature of power
converter 102 or an ambient temperature of the operating environment of power
converter 102. First input 122 may be any input values that allow the control system
of the present disclosure to function as described herein.
[0025] Second derating function 120 is supplied with a second input
124. In embodiments, a second input 124 and a third input 126 are input to a
selection module 128. Selection module 128 selects a maximum, or minimum, value
of second input 124 and the third input 126 to be used as input to second derating
function 120. Second input 124 and third input 126 are, for example, a first
temperature of power converter 102 and a second temperature of power converter 102
taken at a different location from the first temperature. However, second input 124
and the third input 126 may be any input values that allow the control system of the
present disclosure to function as described herein.
[0026] In one embodiment, first derating function 118 outputs a first
derating factor 130 and the second derating function 120 outputs a second derating
factor 132. In another embodiment, first derating factor 130 and second derating
factor 132 are transmitted into a derating factor selection module 134 that compares
and/or selects, a minimum derating factor of first derating factor 130 and second
derating factor 132. The derating factor selection module 134 outputs the selected
derating factor as derating factor 136.
[0027] Derating factor 136 is then transmitted directly, or via
power/var calculation 114 and/or current limit calculation 116, to power converter
102 to be used as a control value as discussed above.
[0028] In a third exemplary embodiment, as shown in Fig. 3, the
control system of the present disclosure includes three or more derating functions 118,
120 and 136.
[0029] The operation of the control system according to the third
embodiment may be similar to the operation described above. However, in the third
embodiment, a third derating function 136 is used in conjunction with first derating
function 118 and second derating function 120. In embodiments, third derating
function 136 receives fourth input 138. In one embodiment, fourth input 138 is a
baseplate temperature of power converter 102, a temperature of power converter 102,
an ambient temperature of the operating environment of power converter 102 or the
like. Fourth input 138 may be any input value that allows the control system of the
present disclosure to function as described herein.
[0030] A third derating factor 33 is calculated and output from
derating function 23. The first derating factor 130, second derating factor 132 and
third derating factor 140 may be input to derating factor selection module 134.
Derating factor selection module 134 compares and/or selects, for example, a
minimum derating factor of first derating factor 130, second derating factor 132 and
third derating factor 140. Derating factor selection module 134 outputs the selected
derating factor as derating factor 136.
[0031] Derating factor 136 is then transmitted directly, or via
power/var calculation 114 and/or current limit calculation 116, to power converter
102 to be used as a control value as discussed above.
[0032] In some embodiments, the systems and method disclosed
herein may be incorporated into a computer or stored on a computer readable
medium.
[0033] The embodiments described herein are not limited to any
particular system controller or processor for performing the processing tasks
described herein. The term controller or processor, as used herein, is intended to
denote any machine capable of performing the calculations, or computations,
necessary to perform the tasks described herein. The terms controller and processor
also are intended to denote any machine that is capable of accepting a structured input
and of processing the input in accordance with prescribed rules to produce an output.
It should also be noted that the phrase "configured to" as used herein means that the
controller/processor is equipped with a combination of hardware and software for
performing the tasks of embodiments of the invention, as will be understood by those
skilled in the art. The term controller/processor, as used herein, refers to central
processing units, microprocessors, microcontrollers, reduced instruction set circuits
(RISC), application specific integrated circuits (ASIC), logic circuits, and any other
circuit or processor capable of executing the functions described herein.
[0034] The embodiments described herein embrace one or more
computer readable media, including non-transitory computer readable storage media,
wherein each medium may be configured to include or includes thereon data or
computer executable instructions for manipulating data. The computer executable
instructions include data structures, objects, programs, routines, or other program
modules that may be accessed by a processing system, such as one associated with a
general-purpose computer capable of performing various different functions or one
associated with a special-purpose computer capable of performing a limited number
of functions. Aspects of the disclosure transform a general-purpose computer into a
special-purpose computing device when configured to execute the instructions
described herein. Computer executable instructions cause the processing system to
perform a particular function or group of functions and are examples of program code
means for implementing steps for methods disclosed herein. Furthermore, a particular
sequence of the executable instructions provides an example of corresponding acts
that may be used to implement such steps. Examples of computer readable media
include random-access memory ("RAM"), read-only memory ("ROM"),
programmable read-only memory ("PROM"), erasable programmable read-only
memory ("EPROM"), electrically erasable programmable read-only memory
("EEPROM"), compact disk read-only memory ("CD-ROM"), or any other device or
component that is capable of providing data or executable instructions that may be
accessed by a processing system.
[0035] A computer or computing device such as described herein has
one or more processors or processing units, system memory, and some form of
computer readable media. By way of example and not limitation, computer readable
media comprise computer storage media and communication media. Computer
storage media include volatile and nonvolatile, removable and non-removable media
implemented in any method or technology for storage of information such as
computer readable instructions, data structures, program modules or other data.
Communication media typically embody computer readable instructions, data
structures, program modules, or other data in a modulated data signal such as a carrier
wave or other transport mechanism and include any information delivery media.
Combinations of any of the above are also included within the scope of computer
readable media.
[0036] This written description uses examples to disclose the
invention, including the best mode, and also to enable any person skilled in the art to
practice the invention, including making and using any devices or systems and
performing any incorporated methods. The patentable scope of the invention is
defined by the claims, and may include other examples that occur to those skilled in
the art. Such other examples are intended to be within the scope of the claims if they
have structural elements that do not differ from the literal language of the claims, or if
they include equivalent structural elements with insubstantial differences from the
literal languages of the claims.
WHAT IS CLAIMED IS:
1. An electrical power generating system, comprising:
a power generating device;
a power converter connected to the power generating device; and
an electrical controller connected to the power converter; wherein the
electrical controller is configured to limit a peak junction temperature of the power
converter by applying at least one junction temperature derating function.
2. The electrical power generating system according to claim 1, further
comprising a temperature sensor that senses a temperature of the power converter and
transmits the sensed temperature to the electrical controller.
3. The electrical power generating system according to claim 2,
wherein the junction temperature derating function is a function of the sensed
temperature.
4. The electrical power generating system according to claim 2,
wherein the controller is configured to limit the output power of the power converter
until the sensed temperature reaches a predetermined value.
5. The electrical power generating system according to claim 1,
wherein a power limiting factor derived from the junction temperature derating
function is applied to the controller to reduce at least one of an output power, current
or voltage of the power converter.
6. The electrical power generating system according to claim 5,
wherein the factor is derived from a selected one of a plurality of junction temperature
derating functions.
7. The electrical power generating system according to claim 6,
wherein the factor is selected as a minimum factor of the plurality of junction
temperature derating functions.
8. A method of controlling a power converter of a electrical power
generating system, said method comprising:
sensing a temperature;
applying at least one junction temperature derating function that is
based upon the sensed temperature to limit the power output of the power converter;
and
limiting the power of the power converter until a predetermined
condition is met.
9. The method according to claim 8, wherein sensing a temperature
comprises sensing a temperature of the power converter.
10. The method according to claim 9, wherein:
the predetermined condition is a threshold temperature value of the
power converter; and
limiting the power comprises limiting the power output of the power
converter until the sensed temperature of the power converter is at or below the
threshold value.
11. The method according to claim 8, wherein a power limiting factor
derived from the junction temperature derating function is applied to reduce at least
one of an output power, current or voltage of the power converter.
12. The method according to claim 8, further comprising selecting the
junction temperature derating function from a plurality of junction temperature
derating functions.
13. The method according to claim 12, wherein a power limiting factor
derived from the selected junction temperature derating function is a minimum factor
of the plurality of junction temperature derating functions.
14. A non-transitory computer readable storage medium storing
program instructions for controlling a power converter of an electrical power
generating system, the program instructions comprising instructions for:
sensing a temperature using a temperature sensing device;
applying at least one junction temperature derating function that is
based upon the sensed temperature to limit the power output of the power converter;
and
limiting the power of the power converter until a predetermined
condition is met.
15. The non-transitory computer readable storage medium according to
claim 14, wherein the sensing a temperature comprises sensing a temperature of the
power converter.
16. The non-transitory computer readable storage medium according
to claim 15, wherein:
the predetermined condition is a threshold temperature value of the
power converter; and
the limiting the power comprises limiting the power output of the
power converter until the sensed temperature of the power converter is at or below the
threshold value.
17. The non-transitory computer readable storage medium according to
claim 14, wherein a power limiting factor derived from the junction temperature
derating function is applied to reduce at least one of an output power, current or
voltage of the power converter.
18. The non-transitory computer readable storage medium according to
claim 14, the instructions further comprising selecting the junction temperature
derating function from a plurality of junction temperature derating functions.
19. The non-transitory computer readable storage medium according to
claim 18, wherein the factor is a minimum factor of the plurality of junction
temperature derating functions.
20. The non-transitory computer readable storage medium according to
claim 19, wherein the factor is a real number between 0 and 1.0.