NL2030275B1 - Method for Preventing Overcurrent and Apparatus Thereof - Google Patents
Method for Preventing Overcurrent and Apparatus Thereof Download PDFInfo
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- NL2030275B1 NL2030275B1 NL2030275A NL2030275A NL2030275B1 NL 2030275 B1 NL2030275 B1 NL 2030275B1 NL 2030275 A NL2030275 A NL 2030275A NL 2030275 A NL2030275 A NL 2030275A NL 2030275 B1 NL2030275 B1 NL 2030275B1
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- grid
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
- H02H9/02—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess current
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/24—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to undervoltage or no-voltage
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/44—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to the rate of change of electrical quantities
- H02H3/445—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to the rate of change of electrical quantities of DC quantities
Abstract
The invention provides a device being an electric control unit and a method of managing grid electric power drawn from an electrical grid by an electrically-powered machine, wherein the electrical grid provides a grid voltage and a grid current to the electrically-powered apparatus connected to the electrical grid. The method performed by the device comprises the recurring steps of measuring one or more voltage values ofthe grid voltage provided by the electrical grid, determining whether a voltage drop of the grid voltage provided by the electrical grid has occurred, based on determining a voltage change, reducing an electric power drawn by the electrically-powered machine from the electrical grid, when it is determined that a voltage drop ofthe power provided by the electrical grid has occurred.
Description
Method for Preventing Overcurrent and Apparatus Thereof
[01] The invention relates to a method of managing grid electric power drawn from an electrical grid by an electrically-powered machine. The invention further relates to an an electrical control unit configured for performing said method. The invention also relates to an electrically powered machine including an electrical control unit configured for performing said method.
[02] When many devices are connected to the same electrical grid, it is necessary to protect the system against electrical overload. An overcurrent in an electrical system occurs when a conductor carries a larger current than intended, resulting in excessive heat generation and in the risk of fire or equipment damage. Short circuits, excessive loading, improper construction of the circuit are all possible causes of an overcurrent.
[03] Overcurrent protection is usually provided by elements such as fuses or circuit breakers. A fuse is commonly made out of a metal strip sandwiched between two electrical terminals. When an excessive amount of current passes through the metal strip, the temperature rises to the point where the metal strip or other elements of the fuse melt. Since the fuse is connected in series with the circuit to be protected, the melting of the fuse elements causes the circuit to open, thereby stopping the current to flow in the circuit. The disadvantage of using a fuse to protect a circuit is that, when a fuse melts, it must be replaced or repaired.
[04] A circuit breaker is an electrical switch that automatically protects a circuit from damage caused by excessive current flow due to an overload or short circuit. Its main function is to interrupt the flow of current when a fault is detected. Unlike a fuse, a circuit breaker can be reset, either manually or automatically, to restore normal operations.
However, the disadvantage of using a circuit breaker to protect a circuit is that circuit breakers have usually quite long operational times, i.e. they are slower in reacting to an overcurrent than fuses.
[05] In addition, whatever element is used, either a fuse or a circuit breaker, when a current overload occurs, the operations of replacing or repairing the fuse or of restoring the circuit breaker request some time, during which the current does not flow in the circuit and, hence, operations cannot be performed. In addition, it is still possible that in case of overcurrent the devices connected to the grid get damaged, in that the operational time (i.e. the time between the moment at which the overcurrent happens and the moment in which fuses or circuit breakers operate) may be not short enough to prevent the overcurrent to create any damage.
[06] Overcurrent due to excessive loading of the circuit could be avoided by simply limiting the power drawn by elements connected to the circuit itself, however, in some cases this is not an easy task. For instance, at construction sites, many user may connect several devices to the electrical grid and, especially at large construction sites, it could be difficult to keep track of all the devices simultaneously connected to the grid.
[07] A user may be unaware of the fact that another user is already using a device or machine connected to the electrical grid and may connect a further device or machine to the grid, thereby requesting an excessive load from the grid itself. In another scenario, the users may be unaware of the load which is drawn from the electrical grid by different devices and connect these devices simultaneously to the electrical grid. In these and other cases, the overcurrent could make fuses melt or circuit breakers operate, thereby causing a stop to the current provided by the electrical grid and a stop to the different activities of the construction site.
[08] Electric or hybrid machines, e.g. electrically-powered machines or apparatus like excavators, trucks, loaders, cranes, crawlers or the like, that are connected to the electrical grid are more and more present on construction sites. The power drawn by these machines from the electrical grid is considerable and the risk of overloading the electrical network by connecting either a plurality of machines or other devices to the network is not negligible. lt is therefore essential to provide an apparatus and a method thereof to prevent the onset of overloading an electrical grid of a construction site.
[09] In an aspect, it is an objective of the invention to provide an efficient method of managing grid electric power drawn from an electrical grid by an electrically-powered machine, wherein the electrical grid provides a grid voltage and a grid current to the electrically-powered apparatus connected to the electrical grid, wherein one or more batteries provide electric power to the electrically-powered apparatus in addition to the grid electric power drawn from the grid by the electrically- powered apparatus, the method comprising the recurring steps of: - measuring one or more voltage values of the grid voltage provided by the electrical grid, - determining whether a voltage drop of the grid voltage provided by the electrical grid has occurred, based on determining a voltage change, - reducing an electric power drawn by the electrically-powered machine from the electrical grid, when it is determined that a voltage drop of the power provided by the electrical grid has occurred.
[10] It is another or alternative objective of the invention to provide a method of managing grid electric power drawn from an electrical grid by an electrically-powered machine comprising the recurring steps of measuring an additional voltage value of the electric power provided by the electrical grid, after that the electric power drawn by the machine from the electrical grid has been limited,
- determining whether the measured additional voltage value is higher than a voltage drop value, wherein the voltage drop value corresponds to the last voltage value measured before limiting the power drawn by the machine, - when it is determined that the measured voltage value is higher than the voltage drop value, increasing the power drawn by the machine from the electrical junction box or the electrical grid.
[11] It is another objective of the invention to to provide a method of managing grid electric power drawn from an electrical grid by an electrically-powered machine wherein increasing the electric power drawn by the machine from the electrical grid to a value corresponding to the value of the electric power drawn by the machine from the electrical grid before the electric power drawn by the machine from the electrical grid has been limited.
[12] It is another or alternative objective of the invention to provide a method wherein determining whether the voltage drop occurs includes determining whether the measured voltage value is lower than a threshold voltage value.
[13] It is another or alternative objective of the invention to provide a method wherein measuring the one or more voltage values of the power provided by the electrical grid includes: - measuring a first voltage value at a first measuring time, - measuring a second voltage value at a second measuring time, wherein the time difference between the second measuring time and the first measuring time is comprised in a a fraction ranging from 0.01 to 0.5 of an operational time of a fuse or circuit breaker of the electrical grid, and - storing, in a memory of the ECU, the first voltage value, the second voltage value, the first measuring time and the second measuring time, wherein determining whether the voltage drop occurs comprises determining whether a voltage difference between the second measured voltage value and the first measured voltage value is negative and smaller than the pre-determined voltage difference value.
[14] It is another or alternative objective of the invention to provide a method wherein measuring the one or more voltage values of the grid voltage includes measuring a plurality of voltage values, and storing, in a memory of the ECU, the plurality of storage values, and wherein determining whether the voltage drop occurs comprises calculating a linear regression of the plurality of measured voltage values and determining that the voltage drop occurs when it is determined that the slope of the linear regression is negative and lower than a pre-determined slope value.
[15] It is another or alternative objective of the invention to provide a method wherein measuring the one or more voltage values of the grid voltage includes measuring a plurality of voltage values, and storing, in a memory of the ECU, the plurality of storage values, wherein determining whether the voltage drop occurs comprises: - calculating a first average voltage value of a first plurality of measured voltage values,
- calculating a second average voltage value of a second plurality of measured voltage values, wherein all the voltage values of the first plurality of measured voltage values are measured at a measuring time earlier than a measuring time corresponding to any voltage value of the second plurality of measured voltage values, - determining that the voltage drop occurs when it is determined that a voltage difference between the second average voltage value and the first average voltage value is lower than a pre-determined difference average value.
[16] It is another or alternative objective of the invention to provide a method wherein measuring the one or more voltage values of the power provided by the electrical grid includes measuring a plurality of voltage values, and storing, in a memory of the ECU, the plurality of storage values, and wherein determining whether the voltage drop occurs comprises: - calculating a first linear regression of a first plurality of voltage values and a second linear regression of the second plurality of measured voltage values as a function of the measuring time, wherein all the voltage values of the first plurality of measured voltage values are measured at a measuring time earlier than a measuring time corresponding to any voltage value of the second plurality of measured voltage values - determining that the voltage drop occurs when it is determined that a second slope of the second linear regression is negative and smaller than a first slope of the first linear regression.
[17] In another aspect, it is an objective of the invention to provide an electrical control unit, ECU, of an electrically-powered machine connectable to an electric grid for providing by the electric grid of an electric voltage and electric current to the electrically- powered machine when connected to the electric grid, wherein one or more batteries provide electric power to the electrically-powered apparatus in addition to the grid electric power drawn from the grid by the electrically-powered apparatus, the ECU comprising: - an input unit configured to receive the electric current from the electrical grid and to continuously measure a voltage value of the electric voltage associated with the electric current provided by the electrical grid, - a memory configured to store data, - an output unit configured to output an output electric current, - a processor, wherein the processor is configured to: - control the input unit to measure one or more voltage values of the grid voltage provided by the electrical grid, - determine whether a voltage drop of the grid voltage provided by the electrical grid has occurred, based on determining a voltage change, - reduce an electric power drawn by the electrically-powered machine from the electrical grid, when it is determined that a voltage drop of the power provided by the electrical grid has occurred.
[18] It is another or alternative objective of the invention to provide a ECU further configured to: control the input unit to measure an additional voltage value of the electric power provided by the electrical grid, after that the electric power drawn by the machine from the electrical grid has been limited, determine whether the measured additional voltage value is higher than a voltage drop value, wherein the voltage drop value corresponds to the last voltage value measured before limiting the power drawn by the machine, and when it is determined that the measured voltage value is higher than the voltage drop value, increase the electric power drawn by the machine from the electrical junction box or the electrical grid and output the increased electric power through the output unit.
[19] It is another objective of the invention to provide a ECU configured to increase the electric power drawn by the machine from the electrical grid to a value corresponding to the value of the electric power drawn by the machine from the electrical grid before the electric power drawn by the machine from the electrical grid has been limited
[20] It is another or alternative objective of the invention to provide a ECU wherein further configured to determine whether the voltage drop occurs by determining whether the measured voltage value is lower than a threshold voltage value.
[21] It is another or alternative objective of the invention to provide a ECU wherein the processor is further configured to: - control the input unit to measure a first voltage value at a first measuring time, - control the input unit to measure a second voltage value at a second measuring time, wherein the time difference between the second measuring time and the first measuring time is comprised in a fraction ranging from 0.01 to 0.5 of an operational time of a fuse or circuit breaker of the electrical grid, and - store, in the memory, the first voltage value, the second voltage value, the first measuring time and the second measuring time, wherein the processor is configured to determine whether the voltage drop occurs by determining whether a voltage difference between the second measured voltage value and the first measured voltage value is negative and smaller than the pre-determined voltage difference value.
[22] It is another or alternative objective of the invention to provide a ECU wherein the processor is further configured to measure a plurality of voltage values, and storing, in the memory, the plurality of storage values, and determine whether the voltage drop occurs by calculating a linear regression of the plurality of measured voltage values and determining that the voltage drop occurs when it is determined that the slope of the linear regression is negative and lower than a pre-determined slope value.
[23] It is another or alternative objective of the invention to provide a ECU wherein the processor is further configured to measure a plurality of voltage values, and store, in the memory, the plurality of measured values, wherein the processor is further configured to determine whether the voltage drop occurs by: - calculating a first average voltage value of a first plurality of measured voltage values, - calculating a second average voltage value of a second plurality of measured voltage values, wherein all the voltage values of the first plurality of measured voltage values are measured at a measuring time earlier than a measuring time corresponding to any voltage value of the second plurality of measured voltage values, - determining that the voltage drop occurs when it is determined that a voltage difference between the second average voltage value and the first average voltage value is lower than a pre-determined difference average value.
[24] It is another or alternative objective of the invention to provide a ECU wherein the processor is further configured to measure a plurality of voltage values, and store, in the memory of the ECU, the plurality of storage values, and wherein the processor is further configured to determine whether the voltage drop occurs by: - calculating a first linear regression of a first plurality of voltage values and a second linear regression of the second plurality of measured voltage values as a function of the measuring time, wherein all the voltage values of the first plurality of measured voltage values are measured at a measuring time earlier than a measuring time corresponding to any voltage value of the second plurality of measured voltage values - determining that the voltage drop occurs when it is determined that a second slope of the second linear regression is negative and smaller than a first slope of the first linear regression.
[25] In another aspect of the invention, an electrically-powered machine comprising a electrical control unit, ECU, is provided.
[26] It is another or alternative objective of the invention to provide wherein the electrically-powered machine is a crane.
[27] Further features and advantages of the invention will become apparent fromthe description of the invention by way of non-limiting and non-exclusive embodiments. These embodiments are not to be construed as limiting the scope of protection. The person skilled in the art will realize that other alternatives and equivalent embodiments of the invention can be conceived and reduced to practice without departing from the scope of the present invention. Embodiments of the invention will be described with reference to the accompanying drawings, in which like or same reference symbols denote like, same or corresponding parts, and in which
Figure 1 schematically shows a simplified electrical scheme of a construction site.
Figure 2 shows a schematic scheme of an electric control unit.
Figure 3 schematically shows a series of measured voltage values.
Figure 4 shows a workflow of a method of managing grid electric power drawn from an electrical grid by an electrically-powered machine, according to an embodiment of the invention.
Figures 5 and 6 show a workflow of a method of managing grid electric power drawn from an electrical grid by an electrically-powered machine, according to another embodiment of the invention.
Figures 7 and 8 show a workflow of a method of managing grid electric power drawn from an electrical grid by an electrically-powered machine, according to another embodiment of the invention.
Figures 9 and 10 show a workflow of a method of managing grid electric power drawn from an electrical grid by an electrically-powered machine, according to another embodiment of the invention.
Figures 11 and 12 show a workflow of a method of managing grid electric power drawn from an electrical grid by an electrically-powered machine, according to another embodiment of the invention.
Figure 13 shows a workflow of a method of managing grid electric power drawn from an electrical grid by an electrically-powered machine, according to another embodiment of the invention.
Figure 14 shows an example of an electrically-powered machine, e.g. a crane.
[28] Figure 1 shows a simplified electrical scheme of a construction site. An electric or hybrid electrically-powered machine 10 (hereinafter simply referred to as the electrically- powered machine) is electrically connected to the main electrical grid 30. The electric or hybrid electrically-powered machine 10 is shown in figure 14 as a crane, however, the invention is not limited thereto and it will be clear that the invention can be applied to any electric or hybrid electrically-powered machine, e.g. an excavator, a truck, a loader, a crane, a crawler or the like. In some cases, as shown in figure 1, electricity is provided to the electrically-powered machine 10 (according to the invention) and to other equipment machines or devices 40 on the construction site by an electrical junction box 20 directly connected to the electrical grid 30. The electrical junction box 20 is a part of the electrical grid 30 electrically connected to the electrical grid 30 through a conductive line 31, e.g. a cable or a wire.
[29] In case a voltage, different from the voltage provided by the electrical grid 30, is needed on the construction site, a transformer {not shown in figure 1) may be connected to the electrical grid 30 and to the electrical junction box 20, so as to transform an input current coming from the electrical grid 30 at a determined voltage to a second current at a different voltage and output the transformed electric current to the electrical junction box 20.
[30] The junction box 20 is that part of the electrical grid 30 allowing electric connections for machines or devices at the construction site. Hereinafter, the electrically- powered machine 10 and the other external equipment 40 will be described, for the sake of clarity, as being connected to the electrical grid 30. However, the person skilled in the art will realize that the invention disclosed in the following is applicable also to the electrically- powered machine 10 and the other external equipment 40 connected to the junction box 20.
[31] In the example shown in figure 1, the electrical system of the electrically- powered machine 10 comprises an electrical control unit (ECU) 110, a charger 120, a battery 130, and various electrical equipment 140. The electrical equipment 140 has to be intended as any electrical system or subsystem of the electrically-powered machine 10 which requires power in form of electricity or electric current for functioning.
[32] In an alternative, the charger 120 and the battery 130 can be replaced by any source of electric power, e.g. an electric generator, a fuel cell, a photovoltaic panel, and the like. It will be clear to the person skilled in the art that an external source of electric power external to the electrically-powered machine 10 is also encompassed by the invention disclosed herein and does not alter the scope of the present invention.
[33] Examples of electrical equipment 140 of the electrically-powered machine10 are motors, pumps, rollers, actuators, control systems, etc. The person skilled in the art will understand that the above list of electrical equipment 140 of the electrically-powered machine 10 is given here as a mere example and is not exhaustive since it may be extended to all the devices of the electrically-powered machine 10 which need electric power to function or to be activated, like lighting systems, air conditioning, onboard computers, etc.
In standard operational conditions, the electrical systems and subsystems, e.g. the electrical equipment 140, of the electrically-powered machine 10 are powered uniquely by the electric power provided by the electrical grid 30.
[34] The electrical junction box 20, hence, the electrical grid 30, is constructed so as to provide at most a maximum grid current Imax at a determined nominal grid voltage Vnomnat, corresponding to a maximum power Pmax. On the construction site, several miscellaneous electrical equipment 40 external to the electrically-powered machine 10 may be connected to the electrical gird 30 or the electrical junction box 20. In case the electrically-powered machine 10 and external equipment 40 connected to the electrical grid 30 or the electrical junction box 20 request a total power Preg greater than the maximum power Pmax deliverable by the electrical junction box 20, an overload of the electrical junction box 20 occurs.
[35] To prevent damages due to overcurrent, the electrical grid 30 or the electrical junction box 20 comprise protection devices, i.e. fuses or circuit breakers, which are activated when the sum of the powers requested Preg by the electrically-powered machine 10 and the external equipment 140 exceeds the maximum power Pmax.
[36] As it has already been observed, the activation of the protection devices causes a stop to the current provided by the electrical grid 30 and, therefore, a stop to the different activities present on the construction site. The construction activities are then delayed due to the time needed for replacing or restoring the protection device(s). To prevent the onset of an overcurrent, the following devices and methods are provided.
[37] The electrically-powered machine 10 is connected to the electrical grid 30,
possibly through the electrical junction box 20. Power, i.e. electricity, is provided by the electrical grid 30, possibly the electrical junction box 20, to the electrical control unit (ECU) 110 of the machine 10. The ECU 110 is an electronic unit embedded in the electrically-powered machine 10 that is configured for controlling the one or more electrical systems or subsystems 140 of the machine 10.
[38] In standard operational conditions, the ECU 110 is configured to provide power, ie. an electric current, to the charger 120, via the conductive line 33, for charging the battery 130 and to the electrical systems and subsystems 140 via the conductive line 34. In these conditions, the battery 130 or, optionally, the alternative source of electric power does not provide electric power to the electrical systems and subsystems 140 of the machine 10.
[39] However, when the electric power provided by the electrical grid 30 is insufficient for the functioning of the electrical systems or subsystems 140, the ECU 110 is further configured to control the battery 130 or, optionally, the alternative source of electric power to provide electric power, i.e. an electric current, to the electrical systems or subsystems 140 of the electrically powered machine 10. The methods of the ECU 110 for providing power to the charger 120 and the electrical systems or subsystems 140 or to control the battery 130 or, optionally, the alternative source of electric power, will be discussed later in detail.
[40] With reference to figures 2 and 3, the ECU 110 comprises an input unit 111 for receiving an electric current and an electric voltage from the electrical grid 30 and for continuously measuring a voltage value associated with the electric current provided by the electrical grid 30, a memory 112 for storing the measured voltage values, an output unit 113 for outputting an electric current to either the electrical systems or subsystems 140 through the conductive line 34 or to the charger 120 through the conductive line 33, and a processor 114 for controlling the input unit 111, the memory 112, the output unit 113, and the battery 130 or, optionally, the alternative source of electric power.
[41] Conductive lines 31, 32, 33, and 34 are represented in the figures as a single conductive line. However, each of the conductive lines 31, 32, 33, and 34 may comprise one or more wires or cables, depending on whether the electric current is a direct current, DC, a monophase alternate current or polyphase alternate current, AC.
[42] Usually, on a construction site, a tri-phase current is provided by the electrical grid 30 or the electrical junction box 20. The root mean square value of the associated voltage provided is commonly 400 V and the intensity of the current usually ranges from 16 to 32 A. However, it will be clear that the invention can be carried out with different values of voltage and current provided by the electrical grid 30.
[43] When electricity is provided by the electrical grid 30 to the input unit 111 of the
ECU 110 through the conductive line 32, the electrically-powered machine is powered and driven by the electric power. The processor controls the input unit 111 to continuously measure voltage values of the provided electric current at node 50. The node 50 is shown for clarity reasons in figure 1 as external to the ECU 110, however, it simply corresponds to an entrance point of the ECU 110, where the current is input into the ECU 110 in the input unit 111.
[44] The input unit 111 measures a series of voltage values 1000 vi, v2, ..., Vis, vi of the electric current at different measuring times ts, tz, ..., ti1, ti, respectively. The processor 114 further controls the input unit 111 to store the voltage values vi, v2, ..., Vis, vi in the memory 112 of the ECU 110. The voltage values described hereinafter always refer to a value of an electric potential difference between the current and the ground being at 0 V. In the case of a polyphase alternate current, the voltage is intended as the electric potential difference between one of the phases and the ground.
[45] Voltage measurements vi, vz, ..., Vit, Vi are performed by a voltmeter or the like 50 included in the input unit 111 and a time difference Di between two adjacent measuring times t.1 and t, i.e. a sampling time, corresponds to a fraction of the standard operational time of a fuse or circuit breaker, the fraction ranging from 0.01 to 0.5 of the standard operational time of a fuse or circuit breaker. It will be clear to the person skilled in the art that, when the current provided by the electrical grid 30 and/or the electrical junction box 20 is an alternate current, the measured voltage value corresponds to the root mean square value of the alternate current voltage, which is a positive number. Hereinafter, it is assumed that voltage values are positive numbers and that voltage values related to an alternate current correspond to the root mean square value of the alternate current voltage.
[46] While the machine 10 is connected to the electrical grid 30, when an external equipment 40 is newly connected to the electrical grid 30, the power drawn by the external equipment 40 from the electrical grid 30 causes the voltage of the current provided by the electrical grid 30 to decrease by a certain amount which depends on the power requested by the connected external equipment 40.
[47] Based on the amount by which the voltage associated with the current provided by the electrical grid 30 is decreased, it is possible to predict whether an overcurrent is going to occur.
[48] In view of this, to prevent overcurrent, the processor 114 is configured to determine a voltage drop associated with the current provided by the electrical grid 30 and to limit the current reguested by the machine 10 from the electrical grid 30.
[49] A voltage value is measured at time steps, i.e. a sampling time, corresponding to a fraction in the range of 0.01 to 0.5 of a standard operational time of a protection device, e.g. a fuse or a circuit breaker usually have an operational time of around 100 ms. In this way, it is possible to predict the onset of an overcurrent before the protection devices are activated, thereby preventing the stopping of power provision by the electrical grid 30 and the rupture/melting of the fuse or the activation of the circuit breaker.
[50] Methods of predicting the onset of an overcurrent and of preventing overload of an electrical grid are discussed with reference to figures 4 — 12. The disclosed methods are performed during the whole period in which the machine 10 is connected to the electrical junction box 20 or the electrical grid 30. In the following, for the sake of clarity, the invention will be described in terms of the electrically-powered machine 10 connected to the electrical grid 30. However, it will be clear to the person skilled in the art that the invention can be also carried out when the electrically-powered machine is connected to the electrical junction box 20 being part of the electrical grid 30.
[51] Figure 4 shows a method of predicting the onset of an overcurrent and of preventing overload of an electrical grid by repeatedly measuring voltage values associated with an electric current input into an electrically-powered machine 10. When the electrically- powered machine is powered and driven in step 1300 by the electric power provided by the electrical grid 30, the processor 114 is configured to measure in measuring step 410 a voltage value vi and to determine in determining step 420 a voltage difference by comparing the measured voltage value vi with a threshold value.
[52] The processor 114 determines in determining step 425 whether a voltage drop occurs. If the measured voltage value v; is lower than the threshold value, the processor 114 determines that the voltage drop occurs. Usually, on a construction site, a tri-phase current is provided by the electrical grid 30 or the electrical junction box 20. The root mean square value of the associated voltage provided is commonly 400 V and the threshold value is set between 300 — 380 V. However, it will be clear that the invention can be carried out with different values of voltage provided by the electric grid and, hence, with different values of the threshold.
[53] When it is determined that the voltage drop occurs, i.e. when it is determined that the measured voltage value vi is lower than the threshold value, the processor 114 is configured to control the input unit 111 of the ECU 110 to limit in limiting step 1330 the power drawn from the electrical grid 30 by limiting the amount of current requested by the input unit 111 to the electrical grid 30. The input unit 111 limits the current requested to the electrical grid 30 to a current value limites lower than the nominal current value nomina: of the current drawn under common operational conditions, i.e. when no voltage drop is determined.
[54] On the other hand, if it is determined that a voltage drop does not occur, i.e. if the measured voltage value vi is greater than or equal to the threshold value, the processor 114 is configured to control the input unit 111 to perform another measurement of a voltage value after a pre-determined period of time, i.e. a sampling time, corresponding to a fraction of the standard operational time of a fuse or circuit breaker, the fraction ranging from 0.01 to 0.5 the standard operational time of a fuse or circuit breaker, and to determine whether the voltage drop occurs based on the newly measured voltage value.
[55] In an alternative embodiment disclosed in figures 5 and 6, when the electrically- powered machine 10 is powered and driven in step 1300 by the electric power provided by the electrical grid 30, the processor controls the input unit 111 to perform a first voltage measurement 1000 for measuring a first voltage value v1000 at a first measuring time t1000 and to perform a second voltage measurement 1001 for measuring a second voltage v1001 at a second measuring time t:1001, wherein the time difference Dont between the second measuring time t109: and the first measuring time t100, the sampling time, corresponds to a fraction of the standard operational time of a fuse or circuit breaker, the fraction ranging from 0.01 to 0.5 the operational time of a fuse or circuit breaker, which corresponds to a range between 1 and 50 ms for an operational time of 100 ms.
[56] The processor 114 controls the input unit 111 to measure in measuring steps 500 and 510 a first voltage value v100 related to the first voltage measurement 1000 and a second voltage value v1001 related to the second voltage measurement 1001, respectively, and to store 515 the first and second voltage values, vice and vioos, respectively, and their associated measuring times t1000 and t:1001, respectively, in the memory 112 of the ECU 110.
[57] After storing the first and second voltage values and times, the processor 114 is configured to determine in determining step 520 a voltage difference by calculating a voltage difference A1001, Ascot being Asoor= V1001-V1000, between the second voltage value v100: and the first voltage value v1000.
[58] Subsequently, the processor 114 determines in determining step 525 whether a voltage drop occurs by determining whether the voltage difference A00: is lower than a pre-determined voltage difference value, the pre-determined voltage value being a negative number. As a non-exhaustive example, the pre-determined voltage difference value can be set to -20V for a voltage provided by the electrical grid 30 having root mean square value of 400 V.
[59] If it is determined that the voltage drop occurs, i.e. if the voltage difference value
A00: is smaller than the pre-determined voltage difference value, the processor 114 is configured to control the input unit 111 of the ECU 110 to limit in limiting step 1330 the power drawn from the electrical grid 30 by limiting the amount of current requested by the input unit 111 to the electrical grid 30. The input unit 111 limits the current requested to the electrical grid 30 to a limited current value limited lower than the nominal current value nomina of the current drawn under standard operational conditions, i.e. when the voltage drop is not determined.
[60] On the other hand, if it is determined that a voltage drop does not occur, i.e. if the voltage difference value A01 is greater than or equal to the pre-determined voltage difference value, the processor 114 is configured to control the input unit 111 to perform in measuring step 510 an additional voltage measurement after a period of time, i.e. the above- described sampling time, and to repeat the process for determining whether the voltage drop occurs based on the newly measured second voltage value and one of the voltage values stored in the memory 112.
[61] Usually, to determine whether a voltage drop occurs, the value of the newly measured second voltage value is subtracted to the voltage value stored in the memory 112 corresponding to the voltage value measured before the newly measured second voltage value. However, the person skilled in the art will understand that the choice of the voltage measurement stored in the memory 112, with respect to which calculating the voltage difference, can be arbitrarily chosen without altering the scope of the invention.
[62] In an alternative embodiment disclosed in figures 7 and 8, when the electrically- powered machine is powered and driven in step 1300 by the electric power provided by the electrical grid 30, the processor controls the input unit 111 to perform in measuring step 710 at least two voltage measurements 1000, 1001, 1002, 1000+N at respective measuring times t1000, 1003, t1002, t000+n, wherein the time difference D between two consecutive measuring times, i.e. the sampling time, is a fraction of the standard operational time of a fuse or circuit breaker, the fraction ranging from 0.01 to 0.5 the operational time of a fuse or circuit breaker. It will be clear to the person skilled in the art that the number of voltage measurements shown in figure 8 has a mere indicative purpose and that it does not limit the scope of the invention.
[63] The processor 114 controls the input unit 111 to measure in measuring step 710 a plurality voltage values v1000, Vi001, Vi002, Vicoosn related to the plurality of voltage measurements 1000, 1001, 1002, 1000+N, respectively, and to store in storing step 715 the voltage values V1000, V1001, V1002, V1000+n, and their respective measuring times t1000, t1001, t1002, t1o00+N, respectively, in the memory 112.
[64] After storing the plurality of voltage values v000, Vioo1, V1002, Viooosn and associated times, the processor 144 is configured to determine in determining step 720 a linear regression L of the plurality of measured voltage values v1000, V1001, V1002, V4000+N 8S a function of the measuring time, and to determine in determining step 725 whether a voltage drop occurs based on the linear regression obtained in step 720.
[65] The processor 114 is configured to determine that the voltage drop occurs by considering a slope of the linear regression L in step 725. When the slope of the linear regression is negative and smaller than a pre-determined slope value, the processor 114 determines in step 725 that an overcurrent event occurs. The pre-determined slope value is a negative number and can be either pre-set or manually set by a user.
[66] If it is determined that the voltage drop occurs, the processor 114 is configured to control the input unit 111 of the ECU 110 to limit in limiting step 1330 the power drawn from the electrical grid 30 by limiting the amount of current requested by the input unit 111 to the electrical grid 30. The input unit 111 limits the current requested to the electrical grid 30 to a limited current value limited lower than the nominal current value lnominat Of the current drawn under standard operational conditions.
[67] The advantage of calculating a linear regression of a plurality of voltage values is to avoid that random voltage fluctuations could affect the determination of the voltage drop. In addition, in view of the fact that the determination of the voltage drop should be made in a time shorter than the operational time of a protective device, i.e. a fuse or a circuit breaker, such method can be used when the period of time D between two adjacent voltage measurements, i.e. the sampling period, is a fraction of the operational time of a fuse or circuit breaker, the fraction ranging from 0.01 to 0.2 the operational time of a fuse or circuit breaker.
[68] In case it is determined that a voltage drop does not occur, i.e. if the slope of the linear regression L is greater than or equal to the pre-determined slope value, the processor 114 is configured to control the input unit 111 to perform 710 an additional voltage measurement, and to repeat the process for determining whether the voltage drop occurs based also on the newly measured voltage value.
[69] In such a case, the determination of the occurrence of a voltage drop in step 725 is performed by taking into account, for the calculation of the linear regression L in step 720, all the voltage values stored in the memory 112. However, the person skilled in the art will understand that the choice of the subset of voltage values stored in the memory 112, with respect to which calculating the linear regression L, can be arbitrarily chosen without altering the scope of the invention.
[70] In an alternative shown in figures 9 and 10, when the electrically-powered machine is powered and driven in step 1300 by the electric power provided by the electrical grid 30, the processor 114 controls the input unit to perform in measuring step 910 a plurality of voltage measurements 1000, 1001, 1002, 1000+N at respective measuring times tiooo, 1004, t1002, t:000+n, respectively, and to store the measured voltage values V1000, V1004, Viooz,
V1000+n, respectively, and the related measuring times in step 915. Steps 910 and 915 correspond to steps 710 and 715 to which reference is made.
[71] The processor 114 is configured to determine in determining step 920 average values of the measured voltage values. In detail, the processor 114 is configured to calculate a first average voltage value 2000 of a first plurality P+ of successively measured voltage values viooo, Vvioot, and to calculate a second average voltage value 2002 of a second plurality Pz of successively measured voltage values viooz, Viooo+n, Wherein all the voltage values of the first plurality of successively measured voltage values are measured at a measuring time earlier than a measuring time corresponding to any voltage value of the second plurality of successively measured voltage values.
[72] Voltage values belonging to the first plurality P+ of voltage values correspond to voltage values measured in a first time interval |; starting from the measuring time t:000 of the first measured voltage value v:000 and having a first time length S. Similarly, voltage values belonging to the second plurality P2 of voltage values correspond to voltage values measured in a second time interval L starting from the end of the first time interval | and having a second time length Sa.
[73] The processor 114 is configured to determine in determining step 925 whether a voltage drop occurs by calculating whether a voltage difference between the second average voltage value 2002 and the first average voltage value 2000 is lower than a pre- determined difference average value, being the pre-determined difference average value a negative number.
[74] If it is determined that the voltage drop occurs, the processor 114 is configured to control the input unit 111 of the ECU 110 to limit in limiting step 1330 the power drawn from the electrical grid 30 by limiting the amount of current requested by the input unit 111 to the electrical grid 30. The input unit 111 limits the current requested to the electrical grid 30 to a limited current value limited lower than the nominal current value lnomina: of the current drawn under standard operational conditions.
[75] The advantage of calculating average values of a plurality of voltage values is to avoid that random voltage fluctuations could affect the determination of the voltage drop.
In addition, in view of the fact that the determination of the voltage drop should be made in a time shorter than the operational time of a protective device, i.e. a fuse or a circuit breaker, such method can be used when the period of time between two adjacent voltage measurements, i.e. the sampling period, is a fraction of the operational time of a fuse or circuit breaker, the fraction ranging from 0.01 to 0.2 the operational time of a fuse or circuit breaker.
[76] In case it is determined that a voltage drop does not occur, i.e. if the voltage difference between the second average voltage value 2002 and the first average voltage value 2000 is greater than or equal to the pre-determined difference average value, the processor 114 is configured to control the input unit 111 to perform 910 an additional voltage measurement, and to repeat the process for determining whether the voltage drop occurs based also on the newly measured voltage value.
[77] In an alternative shown in figures 11 and 12, when the electrically-powered machine is powered and driven in step 1300 by the electric power provided by the electrical grid 30, the processor 114 controls the input unit to perform in measuring step 1110 a plurality of voltage measurements 1000, 1001, 1002, 1000+N at respective measuring times 1000, t1005, t1002, t1000+n, respectively, and to store the measured voltage values v1009, Vioot,
V1002, V1000+n, respectively, and the related measuring times in step 115. Steps 1110 and 1115 correspond to steps 710 and 715 to which reference is made.
[78] Subsequently, the processor 114 calculates a first linear regression Li of the first plurality P+ of voltage values and a second linear regression Lz of the second plurality
P2 of measured voltage values as a function of the measuring time. The selection of the voltage values belonging to the first plurality Ps and the second plurality Pz of measured voltage values is performed in the same way as in the embodiment disclosed in figures 9 and 10, to which reference is made.
[79] The processor 114, in step 1120, compares a first slope of the first linear regression Li and a second slope of the second linear regression Lz and determines in determining step 1125 whether a voltage drop occurs. If the second slope is negative and smaller than the first slope, and if the difference between the second slope and the first slope is lower than a slope threshold, the processor 114 determines that a voltage drop occurs.
[80] If it is determined that the voltage drop occurs, the processor 114 is configured to control the input unit 111 of the ECU 110 to limit in limiting step 1330 the power drawn from the electrical grid 30 by limiting the amount of current requested by the input unit 111 to the electrical grid 30. The input unit 111 limits the current requested to the electrical grid 30 to a limited current value limited lower than the nominal current value liomna: of the current drawn under standard operational conditions
[81] On the contrary, if it is determined that a voltage drop does not occur, the processor 114 is configured to control the input unit 110 to perform an additional measurement of a voltage value, and to repeat the process for determining whether the voltage drop occurs by including in the calculation of the linear regressions the newly measured voltage value. Usually, the newly measured voltage value is taken into account to calculate the second linear regression Lz, However, it will be clear to the person skilled in the art that the subset of the voltage measurements used to calculate the first and second linear regressions can be arbitrarily chosen without altering the scope of the invention.
[82] In any one of the examples above related to figures 4 to 12, when the processor 114 determines that a voltage drop occurs, the processor 114 controls the input unit 111 to limit in limiting step 1330 the power drawn from the electrical grid 30 by limiting the amount the current requested by the input unit 111 to the grid 30.
[83] The input unit 111 limits the current requested to the electrical grid 30 to a value himtea lower than the nominal value of the current drawn under standard operational conditions, Inomina, i.e. when no voltage drop is determined.
[84] To obtain that the electrically-powered machine 10 does not stop working when a voltage drop is determined, the processor 114 is configured to control the input unit 111 to limit the current requested to the electrical grid 30 to a value limitea greater than or equal to zero. The value limited can be a pre-determined value, corresponding to a fraction of the nominal current needed under standard operational conditions, normal, or can be set by a user depending on the working conditions on the construction site.
[85] When controlling the input unit 111 to limit the power drawn by the machine 10 from the electrical junction box 20 or the electrical grid 30, the processor 114 is further configured to control the battery 130 or the alternative electric power source to provide electric power to the electrical systems or subsystems 140 of the electrically-powered machine 10. If the current drawn by the electrically-powered machine 10 from the electrical grid 30 is limited to limited, the processor 114 controls the battery 130 orthe alternative electric power source to provide the remaining needed electric power to the electrical systems and subsystems 140, i.e. the processor 114 controls the battery 130 or the alternative electric power source to provide a current corresponding to Inominarlimited.
[86] Figure 13 shows a method of increasing the amount of electric power drawn by the electrically-powered machine 10 from the electrical grid 30. The method disclosed in figure 13 is combined to any one of the methods disclosed in figures 4 to 12 after that the processor 114 controls the input unit 111 to limit the power drawn from the electrical grid 30 in step 1330, as discussed above.
[87] Once the processor 114 controls in the limiting step 1330 the input unit 111 to limit the power drawn by the machine 10 from the electrical grid, i.e. to limit the drawn current to the value limited, the processor 114 is further configured for controlling the input unit 111 to perform in measuring step 1340 an additional voltage measurement associated with the current provided by the electrical grid 30 and to store the measured voltage value in the memory 112 of the ECU 110.
[88] The measurement of the voltage value is performed at a pre-determined time, corresponding to the sampling time used for measuring voltage values in any one of the methods disclosed in relation to figures 4 to 12. Alternatively, the pre-determined time for performing a voltage measurement can range from tenths of seconds to tenths of minutes from the moment at which the power drawn by the machine 10 has been limited in step 1330.
The preOdetermined time for performing a voltage measurement can be pre-set or can be manually set by a user.
[89] The processor 114 is then configured to determine in determining step 1350 whether the measured voltage value is higher than a voltage drop value, wherein the voltage drop value corresponds to the last voltage value measured before limiting the power drawn by the machine 10 from the electrical grid 30.
[90] When it is determined that the measured voltage value is higher than the voltage drop value, the processor is configured for controlling the input unit 111 to increase the power drawn by the machine 10 from the electrical grid 30. The electric power drawn from the electrical grid 30 is increased by increasing the current drawn from the electrical grid 30 by a step Al corresponding to a fraction of the difference between the nominal current drawn by the machine in standard operational conditions, lominat, and the limited current, limited.
Consequently, the value of limited is increased by the amount Al.
[91] Alternatively, if the measured voltage value is higher than the voltage drop value and is higher than the 95% of the nominal voltage value associated with the current provided by the electrical grid 30, the electric power drawn from the electrical grid 30 is immediately increased to the value of the nominal power drawn by the machine in standard operational conditions, i.e. the current drawn by the machine 10 from the electrical grid 30 is increased to nominal, the value of the electric current drawn by the electrically-powered machine 10 from the electrical grid 30 before the electric power drawn by the machine 10 from the electrical grid 30 has been limited.
[92] Subsequently, the processor 114 controls the input unit 111 to repeatedly perform one of the methods disclosed in relation to figures 4 to 12 to determine whether the increased (updated) current value limited can be kept without incurring in an overcurrent of the system. In this way, if the risk of an overcurrent has been overcome, the machine 10 can quickly be provided with the nominal current lnominai after few repetitions of anyone of the methods disclosed in figures 4 to 12 in combination with the method disclosed in figure 13.
[93] On the contrary, if it is determined that the voltage value is lower than or equal to the voltage drop value, the processor 114 is configured to control the input unit to measure an additional voltage value in the measuring step 1340 and to perform the determining step 1350.
[94] In the method disclosed in figure 13, when controlling the input unit 111 to limit the power drawn by the machine 10 from the electrical junction box 20 or the electrical grid 30, the processor 114 is further configured to control the battery 130 or the alternative electric power source to provide electric power to the electrical systems or subsystems 140 of the electrically-powered machine 10. If the current drawn by the electrically-powered machine 10 from the electrical grid 30 is limited to limites, the processor 114 controls the battery 130 or the alternative electric power source to provide the remaining needed electric power to the electrical systems and subsystems 140, i.e. the processor 114 controls the battery 130 or the alternative electric power source to provide a current corresponding to fnominal-Himited.
[95] The method disclosed in figure 13, in combination with any one of the methods disclosed in figures 4-12, allows the electrically-powered machine 10 to be powered by the electrical grid 30 with the nominal current lhomina after few repetitions of the any one of the methods disclosed in figures 4 to 12 in combination with the method disclosed in figure 13.
Claims (20)
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| NL2030275A NL2030275B1 (en) | 2021-12-23 | 2021-12-23 | Method for Preventing Overcurrent and Apparatus Thereof |
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| NL2030275A NL2030275B1 (en) | 2021-12-23 | 2021-12-23 | Method for Preventing Overcurrent and Apparatus Thereof |
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| KR20030046835A (en) * | 2001-12-06 | 2003-06-18 | 엘지전자 주식회사 | Method for controlling of power supply in potable system |
| WO2010144077A1 (en) * | 2009-06-08 | 2010-12-16 | Hewlett-Packard Development Company, L.P. | Decreasing voltage detection with control signaling |
| US9190830B1 (en) * | 2012-05-03 | 2015-11-17 | Universal Lighting Technologies, Inc. | Overcurrent protection circuit and method for an LED driver |
| DE102017202103B3 (en) * | 2017-02-09 | 2018-03-01 | Ellenberger & Poensgen Gmbh | Method of operating an electronic circuit breaker and electronic circuit breaker |
| DE102018219745A1 (en) * | 2018-11-19 | 2020-05-20 | Zf Friedrichshafen Ag | Controlling an electrical system of a motor vehicle |
| CN111016655B (en) * | 2019-12-16 | 2021-03-19 | 珠海格力电器股份有限公司 | Charging control circuit and method for air conditioner of electric automobile and voltage detection method |
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| KR20030046835A (en) * | 2001-12-06 | 2003-06-18 | 엘지전자 주식회사 | Method for controlling of power supply in potable system |
| WO2010144077A1 (en) * | 2009-06-08 | 2010-12-16 | Hewlett-Packard Development Company, L.P. | Decreasing voltage detection with control signaling |
| US9190830B1 (en) * | 2012-05-03 | 2015-11-17 | Universal Lighting Technologies, Inc. | Overcurrent protection circuit and method for an LED driver |
| DE102017202103B3 (en) * | 2017-02-09 | 2018-03-01 | Ellenberger & Poensgen Gmbh | Method of operating an electronic circuit breaker and electronic circuit breaker |
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