Power system for a locomotive

A power system for a locomotive includes a dynamic brake (DB) grid, at least one chopper circuit, and a controller. The locomotive includes at least one traction motor to power one or more loads during a braking of the locomotive. The DB grid includes at least one resistor bank and is configured to dissipate at least a portion of the power generated by the traction motor. The chopper circuit includes a three-phase inverter module, and selectively disables an electrical communication between the resistor bank and the traction motor. The controller is coupled to the chopper circuit and the loads. The controller determines a magnitude of the loads, and controls the chopper circuit to disable an electrical communication between the resistor bank and the traction motor for a predetermined duration to control a portion of the power dissipated by the DB grid to meet the magnitude of the loads.

TECHNICAL FIELD

The present disclosure relates to a power system for a diesel electric locomotive. More particularly, the present disclosure relates to a chopper circuit for the power system that may dynamically adapt to varying power requirements of the diesel electric locomotive in a dynamic brake mode of the diesel electric locomotive.

BACKGROUND

Locomotives generally use an internal combustion engine to drive a power source, such as a generator or an alternator, to propel a train. Such generators or alternators may convert a mechanical energy of the internal combustion engine into electrical energy (or power) and energize a set of traction motors of the locomotive. The traction motors in turn drive a set of locomotive wheels, thereby enabling locomotive propulsion.

Trains, including passenger trains typically require electrical power for powering various applications that may be unrelated to locomotive propulsion. For example, some locomotives may include an auxiliary power locomotive (APL) system that may provide electrical power for heating, cooling, ambient lighting, and energizing various electrical outlets of the locomotives, and a head end power (HEP) system that may be configured to provide electrical power for heating, cooling, ambient lighting, and energizing various electrical outlets for the railcars of the trains.

During locomotive retardation or braking, a dynamic brake mode may be applied in such locomotives. In a dynamic brake mode, regenerative energy is generally generated by the traction motors. Such regenerative energy may be dumped into one or more dynamic brake (DB) grids of the braking system, and/or the regenerative energy may be consumed by the HEP system and APL system. However, because a resistance provided by the DB grid is generally of a fixed value, a voltage developed across an associated DC link may drop as power dissipated across the DB grid drops. As a result, the alternator may require to support a steady DC link voltage, and may thus need the internal combustion engine to provide supplementary power, leading to a consumption of fuel in the dynamic braking mode.

German Patent DE102009054785A1 relates to a braking chopper that has a three-phase power inverter module that is linked at the direct current side with connectors of an intermediate voltage circuit and is linked at the alternative current side with resistances. The power inverter module has three bridge sections with two electrical semiconductor switches, whose connection points form the alternative current sided connections of the power inverter. Free ends of the resistances are linked together.

SUMMARY OF THE INVENTION

In one aspect, a power system for a locomotive is disclosed. The locomotive includes at least one traction motor configured to power one or more loads during a braking of the locomotive. The power system includes a dynamic brake (DB) grid, at least one chopper circuit, and a controller. The DB grid includes at least one resistor bank, and is configured to dissipate at least a portion of the power generated by the at least one traction motor. The at least one chopper circuit includes a three-phase inverter module, and is configured to selectively disable an electrical communication between the at least one resistor bank and the at least one traction motor. The controller is coupled to the at least one chopper circuit and the one or more loads. The controller is configured to determine a magnitude of the one or more loads. The controller is further configured to control the at least one chopper circuit to disable the electrical communication between the at least one resistor bank and the at least one traction motor for a predetermined duration to control the portion of the power dissipated by the DB grid to meet the magnitude of the one or more loads.

In another aspect, the disclosure relates to a locomotive. The locomotive includes at least traction motor, a dynamic brake (DB) grid, at least one chopper circuit, and a controller. The at least one traction motor is configured to power one or more loads during a braking of the locomotive. The dynamic brake (DB) grid includes at least one resistor bank, and is configured to dissipate at least a portion of the power generated by the at least one traction motor. The at least one chopper circuit includes a three-phase inverter module, and is configured to selectively disable an electrical communication between the at least one resistor bank of the DB grid and the at least one traction motor. The controller is coupled to the at least one chopper circuit and the one or more loads. The controller is configured to determine a magnitude of the one or more loads. The controller is further configured to control the at least one chopper circuit to disable the electrical communication between the at least one resistor bank of the DB grid and the at least one traction motor for a predetermined duration to control the portion of the power dissipated by the DB grid to meet the magnitude of the load.

In yet another aspect, the present disclosure is directed towards a method of controlling a power system for a locomotive during a braking of the locomotive. The locomotive includes at least one traction motor configured to power one or more loads during the braking of the locomotive. The locomotive further includes a dynamic brake (DB) grid configured to dissipate at least a portion of the power generated by the at least one traction motor. The method includes determining, by a controller, a magnitude of the one or more loads. The method further includes disabling, by at least one chopper circuit, an electrical communication between at least one resistor bank of the DB grid and the at least one traction motor for a predetermined duration to control the portion of the power dissipated by the DB grid to meet the magnitude of the load.

DETAILED DESCRIPTION

Referring toFIG. 1, a machine is illustrated. The machine may be an off-highway machine, such as including a locomotive system100(shown inFIG. 1). The locomotive system100includes a locomotive102and one or more railcars104coupled to the locomotive102. The locomotive102and the railcars104may form a train. Although the locomotive102is shown to be coupled to one end of the train, it is possible that a similar locomotive be coupled to another end (not shown) of the train. Further, it is possible that the train includes a number of locomotives at either ends of the train. Other known arrangements of locomotives may also be contemplated. The railcars104may include passenger cars, freight cars, fuel tenders, etc., for carrying passengers, goods, or other loads. A number of wheel sets106are positioned throughout a length of the train in a known manner. The wheel sets106engage tracks108of an associated railroad, thus supporting and facilitating traversal of the train over the railroad.

Although the above discussion, aspects of the present disclosure may be applicable to various other machines and environments. Non-limiting examples of the machines, for both commercial and industrial purposes, may include diesel electric locomotives, diesel mechanical locomotives, steam locomotives, mining trucks, on-highway trucks, off-highway trucks, loaders, excavators, dozers, motor graders, tractors, trucks, backhoes, agricultural equipment, material handling equipment, marine vessels, and other machines that operate in a work environment. It is to be understood that the locomotive system100is shown primarily for illustrative purposes so as to assist in disclosing features and various embodiments of the present disclosure.

Referring toFIGS. 1 and 2, the locomotive102may include an internal combustion engine110(simply, engine110) that facilitates a locomotion of the train over an expanse of the railroad. The locomotive102further includes a power system112(see alsoFIG. 2) that works in concert with the engine110to cater to various operational requirements, and particularly, with one or more loads, such as one or more of electrical loads of the locomotive102and/or the train, as will be discussed below.

Referring toFIGS. 1 and 2, the locomotive102further includes at least one traction motor116that is driven by the engine110and is configured to power the one or more loads during a braking of the locomotive102. In the depicted embodiment, four traction motors116are shown, and the four traction motors116may drive four wheel sets106of the locomotive102. Description pertaining to only one traction motor116may be discussed, and it may be understood that these discussions will be applicable to each of the traction motors116. The traction motor116is configured to power the wheel sets106to move the train. Further, the traction motor116may act as a generator during a braking of the locomotive102. Therefore, the traction motor116generates electrical power during the braking of the locomotive102. At least a portion of the electrical power so generated may be transferred to the one or more loads of the locomotive system100through the power system112. Further, some portion of the electrical power generated by the traction motor116may also be dissipated through the power system112.

The engine110represents one of the commonly applied power generation units in locomotive systems. The engine110may be housed within an engine compartment of the engine assembly, as well known. The engine110may be powered by gaseous fuel, such as liquefied natural gas (LNG), propane gas, hydrogen gas, or any other suitable gaseous fuel, singularly or in combination with each other. Alternatively, the engine110may be based on a dual-fueled engine system, a diesel-fueled engine system, or a spark ignited engine system. The engine110may embody a V-type, an in-line, or any other configuration, as is conventionally known. The engine110may be a multi-cylinder engine, although aspects of the present disclosure are applicable to engines with a single cylinder as well. Further, the engine110may be one of a two-stroke engine, a four-stroke engine, or a six-stroke engine. Although these configurations are disclosed, aspects of the present disclosure need not be limited to any particular engine type.

Referring toFIG. 2, the power system112is shown. The power system112may be configured to distribute power to the loads and the traction motors116of the locomotive102and/or the railcars104. The loads may include non-propulsion based loads. For example, the loads may include head end power (HEP) loads120of the railcars104and auxiliary power locomotive (APL) loads122of the locomotive102.

The power system112may include various electrical and electronic units, such as logic devices, inverters, rectifiers, etc., that facilitate an operation of the power system112. In detail, the power system112may include a traction alternator126operatively coupled to the engine110. The traction alternator126may convert mechanical energy generated by the engine110into electrical energy in the form of alternating current (AC). At the output of the traction alternator126, one or more rectifiers (see example traction rectifier128) may convert AC to direct current (DC). DC is conveyed on a DC link130. In one example, the traction alternator126may be configured to provide a minimum voltage of 2000 V on the DC link130, based on a rotational speed of 1000 rpm of the engine110. Other known configurations and specifications are possible. The power system112may further include a traction system132that facilitate a transfer of power between the DC link130and the traction motor116. The power system112also includes an APL system134that facilitates a transfer of power from the DC link130to the APL loads122, and an HEP system136that facilitates a transfer of power from the DC link130to the HEP loads120. The power system112further includes a power dissipation system140that is connected to the DC link130to receive power generated by the traction motor116during a braking of the locomotive102to meet a magnitude of the loads120,122.

The traction system132may include, for example, one or more traction inverter modules138to convert DC received from the DC link130into AC so that the traction motor116may drive wheel sets106(FIG. 1) of the locomotive102upon a receipt of AC from the traction inverter modules138in a known manner. Also, the traction inverter modules138may convert AC received from the traction motors116into DC to provide DC to the DC link130. In some implementations, the head end power (HEP) loads120and auxiliary power locomotive (APL) loads122may receive power (i.e. regenerative energy) from the traction motor116during a braking of the locomotive102, and excess regenerative energy may be dumped into the power dissipation system140. To enable such a transfer of power, the traction motors116are electrically coupled to the HEP loads120, APL loads122, and the power dissipation system140via the DC link130. Further, the traction system132may also include various switches and/or other electrical components which help in controlling and transferring power between the DC link130and the traction motors116.

The APL system134may be configured to facilitate transfer of power from the DC link130to the APL loads122to power the APL loads122. The APL loads122may be non-propulsion loads of the locomotive102. Examples of APL loads122may include blowers, cooling fans, compressors, pumps, power outlet systems, radiator fans, and various other loads. The APL system134may be configured to receive DC from the DC link130, and may include an inverter modules (not shown) to convert DC into AC, which is then transferred to the APL loads122. Moreover, the APL loads122may include various electrical components, such as, one or more rectifiers, auxiliary inverters, contactors, transformers, auxiliary power converters, switches, etc., that may facilitate power delivery from the DC link130in an acceptable form to the APL loads122.

The HEP system136may be configured to facilitate transfer of power from the DC link130to the HEP loads120to power the HEP loads120. To this end, the HEP system136may include a distribution network for the distribution of power to various HEP loads120. In one example, the HEP system136may include a distribution network for 480 V 60 Hz passenger train line loads. In some implementations, the HEP system136may power various requirements pertaining to heating, cooling, ambient lighting, energizing electrical outlets, etc., of the railcars104. The HEP system136may include a number of components, such as an HEP inverter system, HEP filters, and an HEP transformer (not shown). The HEP system136is configured to convert DC received from the DC link130into AC and provide AC to the HEP loads120.

Further, the power system112includes a controller160that may be communicatively coupled to the power dissipation system140, the APL system134, and the HEP system136. The controller160may also be in communication with the traction system132, the DC link130, the traction alternator126, etc. The controller160is configured to control a magnitude of dissipation of a power generated by the traction motor116during a braking of the locomotive102. The controller160controls the magnitude of dissipation of the power by controlling the power dissipation system140based on the one or more loads (APL loads and/or the HEP loads) connected to the DC link130. For example, the controller160may be configured to determine a magnitude of load (i.e. the APL load122and the HEP load120). For example, a magnitude of load may relate to a power required by the loads120,122. In some implementations, the controller160is configured to control a magnitude of dissipation of power by the power dissipation system140to maintain a voltage of the DC link130above a predetermined threshold. For example, the predetermined threshold may correspond to a minimum voltage of the DC link130by which a magnitude of the APL load122and the HEP load120may be sufficiently met.

To facilitate a control of such dissipation of power, the controller160may include power electronics, preprogrammed logic circuits, data processing circuits, associated input/output buses, volatile memory units, such as random access memory (RAM), etc., to help process signals or data received from the APL system134and/or the HEP system136. For example, the controller160may be configured to receive signals from the APL system134and the HEP system136pertaining to the magnitude of the load connected to the DC link130. Such signals may be processed by a processor of the controller160, according to which the controller160may determine the magnitude of the APL loads122and the HEP load120(and determine a shortfall of power, if any), and then pass instructions to the power dissipation system140for regulating the power dissipation by the power dissipation system140.

In some implementations, the controller160may be coupled to a variety of sensors, such as including current sensors (not shown) that help determine a magnitude of APL loads122and/or HEP loads120. Further, the controller160may include a non-volatile memory that helps record values associates with such loads. The processor within the controller160may process and compare such loads against an availability of regenerative energy during a braking of the locomotive102. Moreover, the non-volatile memory may store specifications of the APL and HEP systems134,136, and may further include a set of instructions that may be applied by the processor to process the data received pertaining to the APL loads122and HEP loads120.

Controller160may be a microprocessor based device, or may be implemented as an application-specific integrated circuit, or other logic device, which provide controller functionality, and such devices being known to those with ordinary skill in the art. In some implementations, the controller160may form a portion of one of the engine's electronic control unit (ECU), such as a safety module or a dynamics module, or may be configured as a stand-alone entity. Further, the controller160may include an analog to digital converter (not shown) that may be configured to receive electrical signals of data from the APL system134and the HEP system136to convert the data and/or electrical signals from these systems into a feedback-specific format.

Referring toFIG. 3, the power dissipation system140is discussed. The power dissipation system140is described in conjunction withFIG. 2. The power dissipation system140is in electrical communication with the DC link130and configured to receive power from the DC link130through a first power line142and a second power line144. The power dissipation system140includes a dynamic brake (DB) grid146with at least one resistor bank, and a chopper system150.

The DB grid146is configured to dissipate at least a portion of the power generated by the traction motors116. For example, a dissipation of power (i.e. regenerative energy) may be in the form of heat to an ambient. The DB grid146may have an array or multiple banks of resistors. As shown inFIGS. 3, 4, and 5, the DB grid146has at least one resistor bank, for example, a first resistor bank162and a second resistor bank164. The second resistor bank164is parallely connected to the first resistor bank162. In some instances, each resistor bank162,164may have a fixed resistance. For example, a value of resistance of each resistor bank may be 3Ω. Further, in an embodiment, the first resistor bank162and the second resistor bank164may have an equal value of resistance. In another embodiment, the first resistor bank162and the second resistor bank164may have a different value of resistance. The first resistor bank162and the second resistor bank164are electrically coupled to the DC link130through the first power line142and the second power line144. The power dissipation system140may further include a grid blower186to cool the DB grid146.

With continued reference toFIG. 3, further aspects of the power dissipation system140is discussed. Each of the first resistor bank162and the second resistor bank164represent one half of the DB grid146. The first resistor bank162is switchably coupled to the first power line142by a first contactor168, and to the second power line144by a second contactor170. The second resistor bank164is switchably coupled to the first power line142by a third contactor172, and to the second power line144by a fourth contactor174. In some implementations, the contactors168,170,172,174may switch between a closed state and an open state. In the closed state, the contactors168,170,172,174may facilitate a flow of current from the first power line142to the second power line, while in the open state, the contactors168,170,172,174may restrict a flow of current from the first power line142and the second power line144. In an embodiment, the controller160may be coupled to each of the contactors168,170,172,174to switch the contactors168,170,172,174between the open state and the closed state.

Further, the chopper system150may be configured to regulate a magnitude of power dissipated through the DB grid146. The chopper system150may control a magnitude of power that is dissipated into the DB grid146to maintain a minimum value of DC link voltage. In so doing, the chopper system150regulates a magnitude of the power dissipated through the DB grid146based on a power rating of the DB grid146(i.e. a power rating of one or more of the resistor banks162,164), and a magnitude of one or more loads (sum of APL and HEP loads120,122) connected to the power system112. In an implementation, the chopper system150may include at least one chopper circuit that may be coupled with at least one resistor bank to control an amount of power that is dissipated into the associated resistor banks. For example, as shown inFIG. 3, the power dissipation system140includes a single chopper circuit156electrically coupled to the first resistor bank162to control a magnitude of power dissipated by the first resistor bank162, and thus in turn controlling a magnitude of power dissipated by the DB grid146.

The chopper circuit156may be electrically coupled to the first power line142by a first switchgear178and to the second power line144by a second switchgear180. Further, chopper circuit156is also in electrical communication with the first resistor bank162through a three-phase output182, as shown. As with an optional connection between the controller and the contactors168,170,172,174, the controller160may also be coupled to the switchgears178,180so as to vary the switchgears178,180between an open state and a closed state. In an embodiment, the contactors168,170,172,174and the switchgears178,180may be manually operated as well.

The chopper circuit156includes a three-phase inverter module including a plurality of semiconductor switches, as shown. For example, the semiconductor switches are in the form of insulated gate bipolar transistors (IGBTs)184. As shown, the chopper circuit156includes six IGBTs184, with three IGBTs184being coupled to a first (upper) branch and remaining three IGBTs184being coupled a second (lower) branch of the chopper circuit156. A lesser or a higher number of IGBTs184are possible. The six IGBTs184allow an enhancement of the braking power handling capacity of the chopper circuit156. In some implementations, either of the upper three IGBTs184or the lower three IGBTs184may be used to transmit power to the DB grid146. The six IGBTs184may be configured to provide pulse width modulation. In some implementations, a disablement of the electrical connection between the first resistor bank162and the DC link130, and thus the traction motors116, is controlled by controlling the IGBTs184.

In one embodiment, the controller160is configured to switch off the IGBTs184to disable an electrical communication between the first resistor bank162and the traction motors116for a predetermined duration within an interval—and for a remaining period of the interval, the controller160switches on the chopper circuit156for the regenerative energy to be dissipated into the DB grid146. Such control may allow a passage of the regenerative energy from the traction motors116to the APL loads122and/or HEP loads120for the predetermined duration, facilitating a meeting of the magnitude of APL loads122and/or HEP loads120during the DB mode. In one example, the interval may be one second, although multiple other intervals are possible. In some implementations, the interval is based on a switching cycle of the chopper circuit156, and although not limited, a switching cycle of the chopper circuit156may be 600 Hertz (Hz), for example. In some examples, the controller160may include a timer (not shown) to deduce the predetermined duration.

In an implementation, to facilitate a switching of the chopper circuit156, the controller160may facilitate an application of voltage to the IGBTs184, therefore changing the properties of the IGBTs184, blocking, and/or creating electrically conductive paths through the IGBTs184for current to travel. A switched-on state of the IGBTs184may refer to a condition when a portion of power is passed to the DB grid146for dissipation, while a switched-off state of the IGBTs184may refer to a condition of increased resistance that helps divert the power to serve APL loads122and HEP loads120. Further, an operation of the power dissipation system140has been depicted inFIG. 4, and has been discussed later in the application.

Principally, the controller160is configured to determine the predetermined duration relative to a switching of the IGBTs184by comparing the magnitude of the one or more loads (APL and/or HEP loads120,122) with a power rating of the associated resistor bank of the DB grid146. For example, as shown inFIG. 3, the controller160determines the predetermined duration based on a power rating of the first resistor bank162of the DB grid146. Details related to a calculation of the predetermined durations will be discussed later in the application.

Referring toFIG. 5, another exemplary state configuration of the chopper circuit156is shown. Notably, this configuration is shown to understand situations where the chopper circuit156need not be used by the power system, and it is required for the chopper circuit156to be electrically disconnected from the DB grid146. For such a disconnection, both the first switchgear178and the second switchgear180need to be moved to the open position, as shown.

Referring toFIG. 6, a power dissipation system140′ is shown. The power dissipation system140′ is an embodiment of the power dissipation system140discussed above. The power dissipation system140′ may remain similar in form and function to the power dissipation system140. However, according to the embodiment of the present disclosure, the power dissipation system140′ includes a chopper system150′ having a dedicated chopper circuit connected to each of the first resistor bank162and the second resistor bank164. More particularly, the chopper system150′ includes two chopper circuits, namely the already described, chopper circuit156(referred to as the first chopper circuit156for this embodiment) and a second chopper circuit156′. The second chopper circuit156′ is similar to the chopper circuit156. In this embodiment, the first chopper circuit156is electrically coupled to the first resistor bank162, while the second chopper circuit156′ is electrically coupled to the second resistor bank164. In so doing, the chopper circuits156,156′ may respectively and independently control a power dissipation through each of the first resistor bank162and the second resistor bank164, thereby more effectively controlling a power dissipation by the DB grid146. Further, the power dissipation system140′ may further include a grid blower186′ to cool the DB grid146.

For the power dissipation system140′, the controller160may also independently determine the predetermined duration, within an interval, for the chopper circuit156′, since a power rating of the second resistor bank164may be different from the power rating of the first resistor bank162. As a result, power though the first resistor bank162and the second resistor bank164may be regulated differently, in certain scenarios.

With continued reference toFIG. 6, and as with the embodiment of the power dissipation system140, the first resistor bank162is switchably coupled to the first power line142by the first contactor168and to the second power line144by the second contactor170. Similarly, the second resistor bank164is switchably coupled to the first power line142by the third contactor172and to the second power line144by the fourth contactor174. In the depicted configuration of the embodiment, the first contactor168and the third contactor172may be open, while the second contactor170and the fourth contactor174may be closed. As with the embodiment of the power dissipation system140, the first chopper circuit156may be switchably coupled to first power line142by the first switchgear178and to the second power line144by the second switchgear180. Similarly, the second chopper circuit156′ may be switchably coupled to first power line142by a third switchgear178′ and to the second power line144by a fourth switchgear180′. In the provided embodiment, each of the first switchgear178, the second switchgear180, the third switchgear178′, and the fourth switchgear180′ are in a closed state. An operation of the power dissipation system140′ has been depicted inFIG. 7, and has been discussed later in the application.

INDUSTRIAL APPLICABILITY

Referring toFIG. 4an operational configuration of the power dissipation system140and a working, according to an aspect of the present disclosure, is shown. In this configuration, the first contactor168may be open, while each of the second contactor170, the third contactor172, and the fourth contactor174, may be closed. Moreover, both the first switchgear178and the second switchgear180may be in a closed state as well. In such a configuration of the power dissipation system140, as the chopper circuit156(i.e. the IGBTs184) is energized or switched on by the controller160, power may be passed from the first power line142to the chopper circuit156, then regulated by the IGBTs184and dissipated further to the first resistor bank162, and then passed to the second power line144through the second contactor170, to maintain DC link voltage. Since the third contactor172and the fourth contactor174are in a closed state in this embodiment, a portion of the power from the DC link130also passes into the second resistor bank164and may be directly or fully dissipated into the second resistor bank164of the DB grid146as heat (i.e. without a regulation by the chopper circuit156).

The controller160may be configured to control the chopper circuit156to control the power dissipation through the DB grid146. Since the controller160may be in communication with the APL system134and/or the APL load122and the HEP system136and/or the HEP load120, the controller160determines the magnitude of load connected to the DC link130. Thereafter, the controller160compares the magnitude of the loads120,122with the power rating of the DB grid146(or in this case the first resistor bank162). In so doing, the controller160controls the chopper circuit156(for example, by controlling a switching of the IGBTs184), thereby regulating a power dissipation into the first resistor bank162, and transmitting a remaining portion of power to meet the loads120,122. Since a magnitude of loads may dynamically change, the controller160may alter a pattern of switching off and/or switching on of the IGBTs184, in turn varying a portion of regenerative energy that may be dumped to the DB grid146as waste energy, and a portion of regenerative energy that may be supplied to meet the APL loads122and/or and HEP loads120. In some implementations, the controller160may regulate power dissipation into the first resistor bank162, disabling an electrical communication between the traction motors116and the first resistor bank162for a predetermined duration.

A calculation of the predetermined duration for which the chopper circuit156is switched to the off state (or to the on state) within an interval, will now be discussed. This discussion relates to an operation of the power dissipation system140. It may be noted that the calculations are disclosed for an ease in understanding of a determination of a duty cycle of the chopper circuit156, and thus, the values used for such a calculation are purely exemplary in nature.

In one exemplary operational scenario, the first resistor bank162may be rated at 1400 Kilowatts (kW), while a combined HEP and APL loads120,122may total 600 kW. While calculating the combined HEP and APL loads120,122, the controller160may take into account losses in the HEP and APL system134,136. The controller160calculates a ratio of the combined HEP loads and APL loads120,122and the power rating of the first resistor bank162to determine the predetermined duration for which the chopper circuit156is switched off. In this example, the ratio is 0.43 which is, obtained by:
600 kW/1400 kW
Based on the ratio, the controller160determines that a percentage of time in an interval for which the chopper circuit156is switched off. As in the example, the ratio is 0.43, the chopper circuit is switched off for 43% time of the interval. In an exemplary scenario, the interval is one second, and in such a case, the predetermined duration is 0.43 sec for which the chopper circuit156is switched off. As the chopper circuit156is switched off for 0.43 sec and switched on for remaining period of the interval (i.e. 0.57 sec), the first resistor bank162dissipates power only during the 0.57 seconds. Therefore, the predetermined duration may be determined as a quantity of time within the one second, and which may be based on the calculated percentage load (i.e. 43%). In this manner, the controller160controls/reduces the power dissipated by the DB grid146in accordance with the magnitude of the loads120,122connected with the DC link130during braking of the locomotive102.

Further, by controlling the power dissipated by the DB grid146during braking of the locomotive102, the controller160maintains a voltage of the DC link130above the predetermined threshold. By maintaining the voltage of the DC link130above the predetermined threshold (minimum required for the APL and HEP systems) during braking of the locomotive102, the controller160prevents a reduction in a torque (power) of the traction motor116below a minimum threshold value. In this manner, during braking of the locomotive102, a transfer of power from the engine110to the DC link130is prevented, and thereby a fuel consumption of the engine110is reduced.

Referring toFIG. 7, an operational configuration of the power dissipation system140′ and a working, according to an aspect of the present disclosure, is shown. In this configuration of the power dissipation system140′, the first contactor168is kept open while the first switchgear178, the second switchgear180, and the second contactor170are closed. In doing so, an electrical communication of the DC link130to the first resistor bank162though the first chopper circuit156(i.e. the IGBTs184) is enabled. The controller160controls the switching of the IGBTs184to enable or disable electrical communication between the DC link130(traction motor116) and the first resistor bank162. In this manner, the controller160controls a portion of the power dissipated by the first resistor bank162. Further, the third contactor172is kept open while the third switchgear178′, the fourth switchgear180′, and the fourth contactor174are close. In this manner, an electrical communication of the DC link130to the second resistor bank164though the second chopper circuit156′ (i.e. the IGBTs184′) is enabled. The controller160controls the switching of the IGBTs184′ to enable or disable electrical communication between the DC link130(traction motor116) and the second resistor bank164. In this manner, the controller160controls a portion of the power dissipated by the second resistor bank164. Since both the first resistor bank162and the second resistor bank164are in respective electrical communication with the first chopper circuit156and the second chopper circuit156′, a power dissipation through the first resistor bank162and the second resistor bank are regulated by the chopper circuits156,156′. The controller160may regulate amount of power dissipation into each resistor banks162,164by disabling an electrical communication between the traction motors116and the resistor banks162,164for a predetermined duration. Although the configurations shown, it may be understood that in various designs, configurations, and applications, there may be a multiple resistor banks applied, and it is possible that for each of those multiple resistor banks, multiple chopper circuits, such as the chopper circuits156,156′ may be respectively applied.

A calculation of the predetermined duration for which the chopper circuit156,156′ is switched to the off state (or to the on state) within an interval, will now be discussed. This discussion relates to an operation of the power dissipation system140′. It may be noted that the calculations are disclosed for an ease in understanding of a determination of a duty cycle of the chopper circuit156,156′ and thus, the values used for such a calculation are purely exemplary in nature.

In one exemplary operational scenario, the first resistor bank162may be rated at 1400 Kilowatts (kW) and the second resistor bank164at 1400 kW as well, while a combined HEP and APL loads120,122may total 600 kW. While calculating the combined HEP and APL loads120,122, the controller160may take into account losses in the HEP and APL system134,136. The controller160calculates a ratio of the combined HEP loads and APL loads120,122and the power ratings of the resistor banks162,164to determine the predetermined duration for which the respective chopper circuits156,156′ is switched off. In this example, the ratio is 0.21 for each of the chopper circuits156,156′, which is, obtained by:
600 kW/(1400+1400) kW
Based on this ratio, the controller160determines that a percentage of time in an interval for which each of the chopper circuits156,156′ is switched off. As in the example, the ratio is 0.21, the chopper circuits156,156′ are switched off for 21% time of the interval. In an exemplary scenario, the interval is one second, and in such a case, the predetermined duration is 0.21 sec for which each of the chopper circuits156,156′ is switched off. As the chopper circuits156,156′ are switched off for 0.21 sec and switched on for remaining period of the interval (i.e. 0.79 sec), the first resistor bank162dissipates power only during the 0.79 seconds. Therefore, the predetermined duration may be determined as a quantity of time within the one second, and which may be based on the calculated percentage load (i.e. 21%). In this manner, the controller160controls/reduces the power dissipated by the DB grid146(first resistor bank162and the second resistor bank164) in accordance with the magnitude of the loads120,122connected with the DC link130during braking of the locomotive102.

In certain implementations, the controller160may divide the load (APL load122+HEP load120) connected with DC link130into number of portions equal to the number of chopper circuits in the power dissipation system. For example, in the illustrated embodiment ofFIGS. 6 and 7, the controller160may divide the load connected to the DC link130into two portions (first portion and second portion). Thereafter, the controller160may calculate the predetermined duration for first chopper circuit156based on ratio of first portion of the load and the power rating of the first resistor banks162. Similarly, the controller160may calculate the predetermined duration for second chopper circuit156′ based on ratio of second portion of the load and the power rating of the second resistor bank164. The controller160may disable the electrical communication between the DC link130(traction motor116) and resistor banks162,164based on the respective predetermined durations to control the power dissipation by the DB grid146during braking of the locomotive102.

Thus, by controlling the power dissipated by the DB grid146during braking of the locomotive102, the controller160maintains a voltage of the DC link130above the predetermined threshold. By maintaining the voltage of the DC link130above the predetermined threshold (minimum required for the APL and HEP systems) during braking of the locomotive102, the controller160prevents a reduction in a torque (power) of the traction motor116below a minimum threshold value. In this manner, during braking of the locomotive102, a transfer of power from the engine110to the DC link130is prevented, and thereby a fuel consumption of the engine110is reduced.

As the magnitude of the load connected with the DC link may vary, the controller160accordingly controls the power dissipation through the power dissipation system140,140′ to maintain the voltage of the DC link130above the predetermined threshold.

Referring toFIG. 8, an exemplary method for controlling the power system112is discussed. The method has been discussed by way of a flowchart800and is described in conjunction withFIGS. 1-7. The method starts at step802.

At step802, the controller160determines a magnitude of the one or more loads120,122. For example, a magnitude of loads120,122may be determined with help of a current sensor that may be suitably placed in the APL and the HEP systems134,136, facilitate a detection of the loads120,122, during dynamic braking of the locomotive102. The method proceeds to step804.

At step804, the controller160disables an electrical communication between at least one resistor banks162,164and the traction motor116for a predetermined duration to control a portion of the power, generated by the traction motor during braking of the locomotive, dissipated by the DB grid146to meet the magnitude of the loads120,122. The disablement is facilitated by use of the at least one chopper circuits, as aforementioned.

As disclosed above, the controller160determines the predetermined duration by comparing the magnitude of the one or more loads120,122with a power rating of the at least one of the resistor banks162,164. The electrical communication between the at least one of the resistor banks162,164and the traction motor116is disabled by the controller160for the predetermined duration during every interval. In one implementation, a ratio between the predetermined duration and a corresponding interval is directly proportional to a ratio between the magnitude of the one or more loads and the power rating of at least one of the resistor banks162,164.

In brevity, the chopper circuits may facilitate a selective and adaptive disablement of an electrical communication between the at least one of the resistor banks162,164and the traction motor116. This allows a maintenance of the voltage of the DC link130while meeting a power requirement of the one or more loads (APL loads122and HEP load120) from the power generated by traction motor116during a braking of the locomotive102. As a result, a requirement to have the engine110provide power to the DC link130to maintain torque (power) of the traction motor116during braking of the locomotive102is prevented, thereby reducing fuel consumption of the locomotive102.

It should be understood that the above description is intended for illustrative purposes only and is not intended to limit the scope of the present disclosure. Thus, one skilled in the art will appreciate that other aspects of the disclosure may be obtained from a study of the drawings, the disclosure, and the appended claim.