A supply equipment communication controller module in a charging station for batteries

Abstract

In a charging station (22) for electric batteries (21), a supply equipment communication controller module (24) monitoring the charging process between the power module (23) and a supervisor module (25) integrates an insulation monitoring device (29) and a manager (19) thereof for repeatedly estimating insulation resistances between the poles (DC+, DC-) of the battery, and the charging conductors (27, 28) with respect to the earth (PE). The device (29) replaces conventional, separate apparatus which must be plugged to the battery and involve cumbersome measurements. In preferred embodiments, the device (29) cooperates with a measurement chain for the voltages of the poles with very little hardware added, which may consist in an electric discharge branch connecting the measurement chain to the earth, and comprising a resistor and a switchable switch.

Description

A SUPPLY EQUIPMENT COMMUNICATION CONTROLLER MODULE IN A CHARGING STATION FOR BATTERIESField of the invention

[0001] This invention relates to a supply equipment communication controller module (generally abridged to SECC module, or even SECC) in a charging station for batteries, for instance batteries equipping electric vehicles.Technological background

[0002] Charging stations for batteries of electrical vehicles require precise energy metering to calculate the energy delivered from the grid to a vehicle. According to the state of the art, this function is performed by dedicated energy meters (also called e-meters) which are integrated into the charging station. The e-meters are subject to regulations concerning the accuracy of the measurement, which ensure verifiable and tamper-proof metering for billing purposes. The inclusion of a dedicated DC e-meter to a charging station adds cost and complexity to the system, in which other necessary components, such as the SECC module and the insulation monitoring devices (often abridged as IMD) already possess some of the necessary functionalities.

[0003] More precisely, according to the state of the art, in electrical charging stations, the SECC modules are combined with power modules supplying the electrical energy to the batteries, for monitoring the charging process and react to particular events and hazards.

[0004] The insulation status of the battery poles with respect to an electrical earth (also called protective earth, abridged PE) is one of the parameters that must be monitored. An insufficient insulation may result from a damp charging cable, although other causes exist. A warning must be issued when the value of any one of the overall resistances between the electrical potential of the poles and the protective earth is found below a first threshold value, and the charging process must even be interrupted when this value is found below a second, lower threshold value.

[0005] The values of these resistances are conventionally sensed by insulation monitoring devices which are independent apparatus making active measurements. A schematic illustration of a widespread example of such apparatus is made in Figure 1. Electrical energy is supplied to the conventional insulation monitoring device 1, separate from the SECC module of the charging station, by a direct current supply 2through a pair of wires 3, and the insulation monitoring device 1 senses an equipment under test 4 through a coupling device 5. The coupling device 5 is often necessary for adapting the electrical potentials of the equipment under test 4 when they are at too high levels. Poles DC+ and DC- of the equipment under test 4 are connected to the coupling device 5, when it must be present, by respective wires 6 and 7, their electrical potentials are indirectly transmitted to the insulation monitoring device 1 by other wires 8 and 9, while the electrical potential of the protective earth is communicated to the insulation monitoring device 1 directly by wires 10. Further wires 11 must generally be added between the insulation monitoring device 1 and the coupling device 5 for enabling their cooperation. The measurements of the resistances between the poles DC+ and DC- and the protective earth appear on a display 12 of the insulation monitoring device 1. This addition of external, plug-in means to the charging station is clearly cumbersome, even when the coupling 5 need not be added to the arrangement.

[0006] The goal of the present invention is to simplify the charging station, while adding new functionalities, as will be explained below.Summary of the invention

[0007] An object of the invention is therefore to improve the general arrangement of electrical charging stations by a different design of the insulation monitoring device.

[0008] Another object of the invention is to avoid cumbersome equipment that must be plugged in to the equipment under test and the SECC module for enabling the insulation measurements.

[0009] A third object of the invention is to simplify, and making more reliable, the insulation measurements.

[0010] A fourth object of the invention is to store the measurements by the insulation measurement device in a memory of the SECC so that it can be retrieved with any other useful information, for instance for confirming a faulty state of the charging process.

[0011] The present invention solves this problem by proposing a novel charging station and a novel method to perform energy metering using the computational resources of the SECC, the voltage measurement capability of the IMD, and a current sensor, thereby eliminating the need for a standalone DC e-meter. More precisely, the SECC serves as the computational hub, integrating data from other componentsand providing features for verifiability and regulatory compliance. The IMD measures voltage across the battery during the charging operation. According to the invention, current measurements can be obtained either from the power module, which already measures currents as part of the AC / DC conversion process, or from an external current resistor such as a Hall-effect sensor or a shunt resistor.

[0012] According to optional features of the invention, the SECC can ensure compliance with energy metering standards through cryptographic signing of energy records using a private key, and / or real-time energy display via a display screen or a video output for consumer transparency.

[0013] According to a main definition, the invention consists in an improved supply equipment communication controller module, which integrates an insulation monitoring device for sensing resistances between poles of a battery to be charged and a protective earth.

[0014] The advantage is twofold: the SECC hardware needs little modification for enabling the insulation measurements, and the measurements can be made quickly and easily. The insulating measurements are passive, i.e. without any plug-in or manual connection of other apparatus. The measurements can be made at any moment by automatised routines. Further, their results are easily managed by the SECC.

[0015] These advantages are most noticeable if the insulation monitoring device is integrated in a direct current, high voltage measurement chain, already present in the SECC module for measuring electrical potentials of said poles: by exploiting the measurement chain and the measurements of these electrical potentials, the insulation resistance may be computed easily and with very little hardware added.

[0016] A still greater integration is obtained if an insulation monitoring device manager, which comprises means for computing said insulation resistances between the poles and the protective earth, is integrated in the supply equipment communication controller. Said insulation monitoring device monitors the insulation resistance of the charging system for safety purposes. In particular, it measures the voltage across the battery during the charging operation, providing high-precision data to the SECC.

[0017] Advantageously, the means for computing use measurements of the electrical potentials of the poles made by the direct current, high voltage measurement chain.

[0018] In important embodiments of the invention, the direct current, high voltage measurement chain comprises:

[0019] - an electric line having ends respectively connected to said poles and composed of a positive side and a negative side, the positive side and the negative side joining at an electrical connection to the electrical earth (also called protective earth);

[0020] - the positive side comprising a first data acquisition resistor and a first voltage measurer for providing the electrical potential of a first one of the poles, the negative side comprising a second voltage measurer for providing the electrical potential of a second one of the poles and a second data acquisition resistor;

[0021] - and the insulation monitoring device comprises: a first electric discharge branch having ends respectively connected to the positive side of the electric line, between the first pole and the first data acquisition resistor, and to the electrical earth, and comprising a switch and a discharge resistor; and a second electric discharge branch having ends respectively connected to the negative side of the electric line, between the second data acquisition resistor and the second pole, and to the electrical earth, and comprising a switch and a discharge resistor.

[0022] The first electric discharge branch and the second electric discharge branch are advantageously identical. Also, the positive side and the negative side of the electric line are advantageously identical.

[0023] The insulation measurement device manager may comprise switch control means for alternatively closing and opening the switches of the first and the second electric discharge branches.

[0024] The insulation monitoring device manager may also comprise means for selecting either the first electric discharge branch or the second electric discharge branch to be closed, for computing one of the insulation resistances.

[0025] Said one of the insulation resistances may be computed according to formulae

[0026] REQ = R0 *{ [VDC-(1) * VDC+(2) I (VDC+(1) * VDC-(2)] - 1} and

[0027] RISO = REQ * (R1 + R2) / [ (R1 + R2) - REQ ],

[0028] in which R0 is the value of the discharge resistor in the selected electric discharge branch; R1 and R2 are, in the side of the electric line to which the selectedelectric discharge branch is connected, values of the data acquisition resistor and of a resistor shunting the voltage measurer; VDC+(1) and VDC-(1) are voltage values respectively measured by the first and the second voltage measurer when the switch of the selected electric discharge branch is open; VDC+(2) and VDC-(2) are voltage values respectively measured by the first and the second voltage measurer when the switch of the selected electric discharge branch is closed; and RISC is the value of said one of the insulation resistances, which corresponds to the side of the electric line to which the electric discharge branch which is not selected is connected.

[0029] Further optional characteristics of the invention include:

[0030] - the means for computing comprise at least one criterion for discarding measurements intended for computing said insulation resistances but having values considered as unreliable;

[0031] - the at least one criterion comprises a model voltage ramp increasing with charging time and a voltage threshold, said measurements being discarded when a difference between their value and the voltage ramp has an absolute value superior to the voltage threshold;

[0032] - the at least one criterion comprises another voltage threshold, the model voltage ramp being corrected by a constant amount when a difference between the value of said measurements and the voltage ramp has an absolute value superior to said another voltage threshold.

[0033] Said supply equipment communication controller can form part of a charging station for batteries, in particular for batteries equipping electric vehicles. Said charging station can be mono-directional (i.e. , grid-to-battery operation) or bidirectional (i.e., grid-to-battery operation or battery-to-grid operation). Said supply equipment communication controller (SECC) is configured to communicate with the electrical vehicle and with the charging network to coordinate the charging operation as well as the billing of the current drawn from the grid into the battery (in the case of grid-to-battery operation) or from the battery into the grid (in the case battery-to-grid operation in bi-directional charging stations). Furthermore, the SECC can implement software algorithms for energy metering based on inputs from the IMD and from a current sensor.

[0034] A particularly advantageous subject-matter of the invention is a charging station for batteries, in particular for batteries equipping electric vehicles, comprisinga power module, a supply equipment communication controller module and a supervisor which comprises a software for managing said charging station, wherein

[0035] said supply equipment communication controller module integrates an insulation monitoring device for sensing insulation resistances (RISO+, RISC-) between poles (DC+, DC-) of a battery to be charged and a protective earth (PE), and characterised in that- the insulation monitoring device is integrated in a direct current, high voltage measurement chain of the supply equipment communication controller module, for measuring electrical potentials (VDC+, VDC-) of said poles, and- said charging station further comprises an insulation monitoring device manager, which is integrated in the supply equipment communication controller and comprises means for computing said insulation resistances between the poles and the electrical earth, and- said means for computing use measurements of the electrical potentials (VDC+, VDC-) of the poles made by the direct current, high voltage measurement chain.

[0036] In an advantageous embodiment, this charging station is characterised in that the direct current, high voltage measurement chain comprises:- an electric line having ends respectively connected to said poles and composed of a positive side and a negative side, the positive side and the negative side joining at an electrical connection to the protective earth (PE);- the positive side comprising a first data acquisition resistor and a first voltage measurer for providing the electrical potential of a first one of the poles (DC+), the negative side comprising a second voltage measurer for providing the electrical potential of a second one of the poles (DC-) and a second data acquisition resistor, - and the insulation monitoring device comprises: a first electric discharge branch comprising a switch and a discharge resistor arranged in series and having ends respectively connected to the positive side of the electric line, between the first pole (DC+) and the first data acquisition resistor, and, via said switch, to the protective earth (PE) ; and a second electric discharge branch comprising a switch and a discharge resistor arranged in series and having ends respectively connected to the negative side of the electric line, between the second data acquisition resistor and the second pole (DC-), and, via said switch, to the electrical earth, wherein in each of thefirst and second electric discharge branches said discharge resistor is arranged in parallel with said first or second data acquisition resistor, respectively.

[0037] In an advantageous embodiment, said supply equipment communication controller module comprises a single printed circuit board having: a) a processing unit; b) communication circuitry, controlled by said processing unit, for establishing and controlling a charging session with an electric vehicle; c) a high-voltage DC voltage measurement chain for measuring the electrical potentials of the positive and negative poles of a DC bus relative to a protective earth, and d) an insulation monitoring device circuit, controlled by said processing unit and in functional relationship with said high-voltage DC voltage measurement chain, comprising at least one switchable electric discharge branch for controllably creating an impedance path between one of the DC bus poles and the protective earth.

[0038] Said processing unit can be integrated with said high-voltage DC voltage measurement chain.

[0039] According to a first advantageous variant of this embodiment, said processing unit is configured for both monitoring the DC bus voltage during the charging operation and for determining the insulation resistance by measuring voltage changes when said discharge branch is activated.

[0040] According to a second advantageous variant of this embodiment, said supply equipment communication controller module further comprises a communication interface for receiving partial current measurements from one or more external power modules, wherein said processing unit is further configured to calculate total electric power and energy by combining a sum of the received partial current measurements with the voltage measured by said high voltage DC voltage measurement chain, thereby performing a virtual e-meter function.

[0041] A charging station comprising said supply equipment communication controller module can be configured to carry out a method for monitoring insulation resistance, said method comprising the steps of : a) measuring a first set of DC bus pole voltages using the high voltage DC voltage measurement chain while at least one discharge branch is in an open state; b) closing a switch in the at least one discharge branch to introduce a known impedance; c) measuring a second set of DC bus pole voltages; and d) calculating, by said processing unit, the insulation resistance based on the difference between the first and second sets of measured voltage. This method forms a second subject-matter of the invention.

[0042] In a first advantageous embodiment of said method, said method further comprises the steps of measuring the initial rate of change of said DC bus pole voltages during step a) or step c, estimating an RC time constant of the connected electrical system based on said rate of change, and dynamically adjusting a duration for the voltage measurements based on the estimated RC time constant to optimize measurement accuracy and speed, in particular during pre-charge phases of the charging session. Said estimation of an RC time constant can be achieved by said processing unit.

[0043] In a second advantageous embodiment of said method, said method further comprises the steps of comparing the measured voltage values against a predicted voltage model, and discarding the calculated insulation resistance value if the measured values deviate from the predicted model by more than a predetermined threshold, thereby rejecting unreliable measurements, in particular when charging converters are unloaded.

[0044] A charging station comprising said supply equipment communication controller module can also be configured to carry out a method for performing diagnostics with the charging station according to any of its embodiments, said method comprising the steps of: a) logging, by said processing unit, communication fault events detected by said supply equipment communication controller module, b) logging, by said processing unit, insulation fault events detected by said insulation monitoring device, and c) triggering a diagnostic routine when a communication fault and an insulation fault are logged within a predefined time window of each other, thereby correlating said communication fault events and said insulation fault events. This method forms a third subject-matter of the invention.

[0045] A charging station comprising said supply equipment communication controller module can also be configured to use a method for metering performed by the charging station, said method comprising the steps of a) periodically requesting and receiving partial current measurements from a plurality of power modules connected to said DC bus, b) summing the partial current measurements to determine a total charging current, and c) calculating total power by multiplying the total charging current by the voltage measured via the high voltage DC voltage measurement chain. Said summing can be achieved by said processing unit. This method forms a fourth subject-matter of the invention.

[0046] In a variant of this method, said method further comprises the steps of formatting the calculated total power and energy data into a standard meter protocol, and transmitting said formatted data over a communication interface to emulate the output of a physical e-meter device. Said communication interface can be a serial communication interface, such as an RS485 interface.

[0047] In another variant of this method, said method further comprises the steps of receiving a temperature measurement from a temperature sensor (which is typically located in the charging connector), calculating an adjusted resistance value from the charging cable based on the temperature measurement and a known baseline resistance, calculating the voltage drop and power loss in the charging cable using the total charging current and the adjusted cable resistance, and compensating the calculated total power to determine the actual power delivered to the vehicle’s battery terminals. This variant allows for cable loss compensation.Short description of the figures

[0048] The characteristics, purposes and advantages of the invention will now be exposed more in detail with the help of the following figures, of which figures 2 to 6 disclose a preferred embodiment of the invention, in a purely illustrative way only, while figure 1 illustrates a prior art:- Figure 1 (already described) illustrates a conventional device comprising an external, plugged-in insulation monitoring device;- Figure 2 illustrates the main components of an electrical charging station, comprising a supply equipment communication controller according to the invention;- Figure 3 illustrates the direct current, high voltage measurement chain and the integrated insulation monitoring device of the inventive supply equipment communication controller;- Figure 4 is a diagram showing the general method for computing the insulation resistance;- Figure 5 is a plot indicating how measurements are taken into account, or cancelled; - Figure 6 is a diagram showing the detail of computations of the insulation resistance.Detailed description of the invention

[0049] Figure 2 will be described now. An electric vehicle 20 comprises a battery 21 having a positive pole DC+ and a negative pole DC-. A charging station 22 designed for charging a vehicle battery comprises a power module 23, a supply equipment communication controller (SECC) 24 and a supervisor 25 which comprises a software for managing the charging station 22, and possibly a man-machine interface. The SECC 24 is connected to the power module 23 and to the supervisor 25 so that the SECC 24 monitors the charging process and issues warnings to the supervisor 25, or interrupts the process, when malfunctions occur. A charging cable 26 links the power module 23 and the battery 21 and comprises two conductors 27 and 28 leading to the positive and negative poles DC+ and DC- respectively.

[0050] In a specific embodiment, said charging cable 26 comprises a connector configured to be connected to the positive and negative poles of the battery. In another specific embodiment, which can be combined with the previous one, said connector can house a temperature sensor.

[0051] According to the invention, the SECC 24 comprises an insulation monitoring device 29 integrated therein, as well as an insulation monitoring device manager 19. The integration means that the insulation monitoring device 29 and the insulation monitoring device manager 19 are not physically separable from the remainder of the SECC 24. Since the SECC 24 often consists in a board carrying processors and other electronic equipment, the equipment characterising the insulation monitoring device 29 and the insulation monitoring device manager 19 will be borne by this board. But the degree of integration is actually deeper in the instant embodiment, because it takes advantage of an equipment of the SECC 24 already used for another measurement, for contributing to the determination of the insulation resistances. In other words, the components specific to the insulation measurement device 29 are connected to the components of this other equipment and cooperate with them.

[0052] Advantageously, the SECC comprises one single printed circuit board, said printed circuit board comprising a processing unit, communication circuitry, a high-voltage DC voltage measurement chain, and an insulation monitoring device 29. Said processing unit is equipped with a processor capable of real-time data acquisition and computation.

[0053] This is explained in Figure 3. The SECC 24 comprises a measurement chain 30, in which an electric line 31 is continuous between ends 32 and 33 connectedto the conductors 27 and 28 respectively. The electric line 31 comprises, from end 32 to end 33:

[0054] - at a positive side of the measurement chain 30, a first or positive electric discharge branch 37 carrying a resistor 38 and a switch 39 in series, and leading to the protective earth PE;

[0055] - a first main resistor 40;

[0056] - a first voltage measurer 41 , with a shunt resistor 42:

[0057] - a connection 43 to the protective earth PE;

[0058] - and a symmetrical arrangement at a negative side of the measurement chain 30, successively comprising a second voltage measurer 44 with a shunt resistor 45, a second main resistor 46, a second or negative electric discharge branch 47, and a connection of a second earthing line 49. The negative electric discharge branch 47 also comprises a resistor 48 and a switch 49 in series and leading to the electrical potential. The corresponding components are advantageously identical. For instance, the first and second main resistors 40 and 46 have same values, and the same applies to resistors 38 and 48. The switches 39 and 49 consist, in this embodiment, of solid-state relays switched by energising circuits (not shown on the figures) which are known as such. Each of the voltage measurers 41 and 44 comprises two input lines each, both the input lines are connected to the electric line 31 on either side of the respective shunt resistor 42 or 45.

[0059] With the exception of the positive and negative electric discharge branches 37 and 47, all these components are designed for measuring the electrical potentials of the poles DC+ and DC-, and they belong to a so-called direct current, high voltage (HVDC) section of the SECC 24. The measurements VDC+ and VDC-with respect to the protective earth of these electrical potentials are provided at the respective output lines of the voltage measurers 41 and 44. Thus, the insulation monitoring device 29 is composed of the electric discharge branches 37 and 47, which cooperate with this HVDC section.

[0060] The electric charging circuit is considered as having an overall resistance, called an insulation resistance RISO+, between the pole DC+ and the protective earth PE, and another insulation resistance RISC- between the other pole DC- and- the protective earth PE. They should not dwindle under specified values for safety reasons. The operation of the SECC 24 for determining these insulation resistancesRISO will be described now with reference to Figure 4. It is performed with the help of the insulation monitoring device manager 19, which may consist in a processor, integrated in the SECC 24 like the insulation monitoring device 29 itself, and which may also include software like switch controller means for controlling the switches 39 and 49, computing means for obtaining the values of the insulation resistances, and selecting means for cancelling some measurements, as described hereunder.

[0061] A computation of the insulation resistances RISO is triggered (step S1) automatically at regular times. Both the switches 39 and 49 are open at the beginning of the process. A time counter is initialised (step S2), the voltage measurers 41 and 44 are repeatedly sampled, and successive values of the measured values of VDC+ and VDC- are stored at step S3. However, the algorithm is devised to discard noisy or unreliable measurements. In a following step S4, it is checked whether the sum VDC of the measurements VDC+ and VDC- (VDC+ + VDC- = VDC) is greater than a first threshold Vmin corresponding to a lower operation limit of the insulation monitoring device 29 (Figure 5). If they are greater, the algorithm progresses to the following steps, otherwise a reset is done, the algorithm returns to step S3, and the previous measurements, considered as irrelevant, are not processed. Further, the evolution of the measurements of the sum VDC is surveyed.

[0062] The measurements are compared to a preset voltage ramp Vramp representative of a normal charging process and having a moderate slope according to time (t). In a next step S6, it is checked whether the absolute value | VDC - Vramp | becomes greater than a second threshold Vrampl at any moment. If this absolute value is smaller, the measurements of the sum VDC are considered to be fitting for a computation of the insulation resistances RISO+ and RISC-, and the program goes to step S9 and may engage this computation. If it is greater, an abnormal charge process may be present, and there is no computation of the insulation resistances at this time. However, if the difference | VDC - Vramp | is greater than a third threshold Vramp2 (step S7), the voltage ramp Vramp will be adjusted (step S8) by adding or subtracting a value Vcorr so that the voltage ramp Vramp is displaced and coincides with the VDC measurement at this moment (VDC = Vramp + Vcorr), while remaining at the same slight slope. This correction will enable a better match of the model charging function embodied by the voltage ramp Vramp and the actual measurements VDC, so that the computations of the insulation resistances RISO will not be excessively delayed in the circumstances of a normal charging process, in which the slope of the measurements VDC will converge to the slope of Vramp.

[0063] After S7, or S8 when this is necessary, the program returns to step S3 and the measurements of the sum VDC are resumed. Also, the program returns to step S3 when the insulation resistance is computed and step S9 has ended, in order to repeatedly update the computation.

[0064] Figure 5 illustrates these different possible states of the measuring process, when the sum VDC of the measured voltages VDC+ and VDC- has reached the minimal voltage Vmin at instant to, and the insulation monitoring device 29 become active. The voltage ramp being applied from this instant, the difference between Vramp and VDC reaches Vrampl and Vramp2 at later instants t1 and t2 respectively in this particular illustration, and Vcorr is applied shortly after Vramp2 has been found. As already explained, the computation of the resistances RISO+ and RISC- is interrupted between instants t1 and t2.

[0065] Should however the charge process remain unstable, a warning of failure to compute the insulation resistances will be issued after a preset expiration time has elapsed. The process may comprise a step S5 between steps S4 and S6, which consists in reading the time counter (initialised at step S2). If the expiration time has been reached, the warning is issued at step S10, the computation process is interrupted, and it will be resumed later with a reset to step S1.

[0066] Step S9 will now be disclosed in detail with reference to Figure 6.

[0067] A first measurement of the electrical potentials VDC+(1) and VDC-(1) of the battery poles is made at a same instant (1) by the voltage measurers 41 and 44 (step S12), and the corresponding values are stored.

[0068] These values VDC+(1) and VDC-(1) and compared (step S13). According to the result of the comparison, one of the switches 39 and 49 is selected and closed (S14).

[0069] The comparison in step S13 and the selection in step S14 are made as follows. If VDC+(1) > VDC-(1) (or more generally [VDC+(1) - PE] > [PE - VDC-(1)] if it is not assumed that the earth potential is zero) it is stated that the impedance is lower in the negative side of the measurement chain 30, so RISO- is lower than RISO+ and will be critical so that it will be computed first. Further, the switch 39 in the positive electric discharge branch 37 is selected and closed.

[0070] In the next step (S15), a second measurement of the electrical potentials VDC+(2) and VDC-(2) is made at an instant (2), when the selected switch 39 has just been closed.

[0071] The computation of the insulation resistances RISO+ and RISO- becomes possible and is made in the following steps (S16 and S17).

[0072] RISO- is determined in step 16 by applying formulae {1} and {2}:

[0073] {1} REQ_N = RO *{ [VDC-(1) * VDC+(2) I (VDC+(1) * VDC-(2)] - 1}

[0074] then {2} RISO- = REQ_N * (R1 + R2) / [ (R1 + R2) - REQ_N ],

[0075] in which RO is the value of the resistor 38 in the positive electric discharge branch 37, R1 the value of the main resistor 40, and R2 the value of the shunt resistor 42 in the positive side of the measurement chain 30.

[0076] RISO+ can easily be computed in the last step 17. Since the electric circuit may be considered as consisting of the two insulation resistances RISO+ and RISO-between the poles DC+ and DC-, VDC+ and VDC- have been measured and RISO-has just been computed, a voltage division operation RISO+ = RISO- (VDC+ 1 VDC-) becomes possible, both the switches 39 and 49 being opened for this.

[0077] It is valuable to close the switch 39 or 49 associated to the side (here, the switch 39 associated to the positive side) having the greater impedance. The perturbation of the electrical balance brought about by the switching operation is greater, the effects of noise in the measurements are smaller, and the computations are more accurate.

[0078] If conversely VDC+ < VDC-, the impedance is lower in the positive side of the measurement chain 30, and the insulation resistance RISO+, being lower than RISC-, is preferably computed. Steps S14 to S17 are performed as follows. The switch 49 in the negative electric discharge branch 47 is selected and closed, and the modified values of VDC+(2) and VDC-(2) are measured and stored in step S15. The computations in step S16 consist of:

[0079] (3) REQ_P = R0 *{ [VDC-(1) * VDC+(2) I (VDC+(1) * VDC-(2)] - 1}

[0080] then (4) RISO+ = REQ_P * (R1 + R2) / [ (R1 + R2) - REQ_P ].

[0081] in which R0 is the value of the resistor 48 in the negative electric discharge branch 47, R1 the value of the main resistor 46, and R2 is the value of the shunt resistor 45 in the negative side of the measurement chain 30.

[0082] The voltage division in step S17 therefore consists in RISO- = RISO+ (VDC- 1 VDC+) in this situation, both the switches 39 and 49 being opened.

[0083] The rationale of the method can be explained as follows. The insulation resistances RISO+ and RISO- correspond to all the resistances separating the ends 32 and 33 from the protective earth PE. The voltage distribution along the measurement chain 30 can be expressed by an equation f(VDC+, VDC-, RISO+, RISO-). VDC+(1) and VDC-(1) being measured at the voltage measurers 41 and 44, two unknown variables (RISO+ and RISO-) remain. The insertion of the resistor 38 or 48 into the system introduces a disparity in the voltage distribution according to a second equation with the same unknown variables. When VDC+(2) and VDC-(2) are measured in the new configuration of the measurement chain 30, the system of the two equations can be solved.

[0084] Another advantage of the integration of the insulation measurement device 19 in the SECC 24 consists in that the measurements made in steps S12 and S15 are stored and can be retrieved with other measurements by the SECC 24 when this is wanted, if any fault has been diagnosed. The access to past measurements will help the operator to conclude whether, for instance, the cable is really damaged or otherwise unable to perform its function, or the measurements were rather spoilt by noise and the material is convenient. Further, the common timing for the insulation measurement device and the SECC 24 will enable to correlate the voltage measurements by the insulation measurement device 19 with any other information delivered by the SECC 24. This easy access and exploitation of the memory of the insulation measurement device 19 is not available in conventional installations with a plugged-in apparatus.

[0085] This new architecture of the supply equipment communication controller with an integrated insulation monitoring device involves a series of advantages over the suppression of separate, plugged-in devices. The use of an existing circuit (the measurement chain 30) enables to hardly complicate the existing SECCs for computing the insulation resistance. The measurements allowed by the integrated insulation measurement device 29 are easily triggered, do not require great care from the operator; they can be stored easily, and exploited directly by the insulation measurement device manager 19 which is also integrated in the SECC 24 and in which data characterising the insulation measurement device 29 are logged. The computations can be performed within a few seconds either in real chargingprocesses or autotests. The SECC 24 can be adapted to a number of combinations of batteries 21 and charging stations 22.

[0086] The invention has further advantages. It eliminates the need for a standalone DC e-meter by utilizing existing components. In particular, the integration of energy metering into existing components reduces system complexity and maintenance requirements. It can be implemented in various types of battery charging stations, in particular suitable for electrical vehicles, including residential charging stations and high-power DC fast charging stations. The SECC can accommodate different cable types and lengths and still maintain the required accuracy of the energy metering process. It uses the computational capabilities of the SECC for real-time data processing and fault detection. It is capable of meeting applicable accuracy standards for energy metering with appropriate calibration and temperature compensation. It can integrate cryptographic signing to ensure data integrity, and can therefore meet requirements regarding verifiability and tamper-proofing.

Claims

CLAIMS1. A charging station (22) for batteries, in particular for batteries equipping electric vehicles, comprising a power module (23), a supply equipment communication controller module (24) and a supervisor (25) which comprises a software for managing said charging station (22), wherein said supply equipment communication controller module (24) integrates an insulation monitoring device (29) for sensing insulation resistances (RISO+, RISC-) between poles (DC+, DC-) of a battery (21) to be charged and an electrical earth (PE), and characterised in that- the insulation monitoring device is integrated in a direct current, high voltage measurement chain (30) of the supply equipment communication controller module (24), for measuring electrical potentials (VDC+, VDC-) of said poles, and- said charging station further comprises an insulation monitoring device manager (19), which is integrated in the supply equipment communication controller (24) and comprises means for computing said insulation resistances between the poles and the electrical earth, and- the means for computing use measurements of the electrical potentials (VDC+, VDC-) of the poles made by the direct current, high voltage measurement chain (30).

2. The charging station according to claim 1, characterised in that the direct current, high voltage measurement chain (30) comprises:- an electric line (31) having ends (32, 33) respectively connected to said poles and composed of a positive side and a negative side, the positive side and the negative side joining at an electrical connection (43) to the electrical earth (PE); - the positive side comprising a first data acquisition resistor (40) and a first voltage measurer (41) for providing the electrical potential of a first one of the poles (DC+), the negative side comprising a second voltage measurer (44) for providing the electrical potential of a second one of the poles (DC-) and a second data acquisition resistor (46),- and the insulation monitoring device (29) comprises: a first electric discharge branch (37) comprising a switch (39) and a discharge resistor (38) arranged in series and having ends respectively connected to the positive side of the electricline, between the first pole (DC+) and the first data acquisition resistor (40), and, via said switch (39), to the electrical earth (PE) ; and a second electric discharge branch (47) comprising a switch (49) and a discharge resistor (48) arranged in series and having ends respectively connected to the negative side of the electric line, between the second data acquisition resistor (46) and the second pole (DC-), and, via said switch (49), to the electrical earth, wherein in each of the first and second electric discharge branches (37,47) said discharge resistor (37,48) is arranged in parallel with said first (40) or second (46) data acquisition resistor, respectively.

3. The charging station according to claim 2, characterised in that the first electric discharge branch and the second electric discharge branch (37, 47) are identical.

4. The charging station according to claim 3, characterised in that the positive side and the negative side of the electric line (31) are identical.

5. The charging station according to claims 1 and 2, characterised in that the insulation measurement device manager (19) comprises switch control means for alternatively closing and opening the switches (39, 49) of the first and the second electric discharge branches.

6. The charging station according to claims 1 and 2, characterised in that the insulation monitoring device manager (19) comprises means for selecting either the first electric discharge branch or the second electric discharge branch (37, 47) to be closed, for computing one of the insulation resistances, and characterised in that said one of the insulation resistances is computed according to formulaeREQ = RO *{[VDC-(1) * VDC+(2) I (VDC+(1) * VDC-(2)] - 1} andRISO = REQ * (R1 + R2) / [ (R1 + R2) - REQ],in which RO is the value of the discharge resistor in the selected electric discharge branch; R1 and R2 are, in the side of the electric line (31) to which the selected electric discharge branch is connected, values of the data acquisition resistor (40, 46) and of a resistor (42, 45) shunting the voltage measurer (41, 44); VDC+(1) and VDC-(1) are voltage values respectively measured by the first and the second voltage measurer when the switch of the selected electric discharge branch is open; VDC+(1) and VDC+(2) are voltagevalues respectively measured by the first and the second voltage measurer when the switch of the selected electric discharge branch is closed; and RISC is the value of said one of the insulation resistances, which corresponds to the side of the electric line (31) to which the electric discharge branch which is not selected is connected.

7. The charging station according to claim 1 , characterised in that the means for computing comprise at least one criterion for discarding measurements intended for computing said insulation resistances but having values considered as unreliable.

8. The charging station according to claim 7, characterised in that the at least one criterion comprises a model voltage ramp (Vramp) increasing with charging time and a first voltage threshold (Vrampl), said measurements being discarded when a difference between their value and the voltage ramp has an absolute value superior to the voltage threshold.

9. The charging station according to claim 8, characterised in that the at least one criterion comprises a second voltage threshold (Vramp2), the model voltage ramp (Vramp) being corrected by a constant amount when a difference between the value of said measurements and the voltage ramp has an absolute value superior to said second voltage threshold.

10. The charging station according to any of claims 1 to 9, characterised in that said supply equipment communication controller module comprises a single printed circuit board having:a) a processing unit;b) communication circuitry, controlled by said processing unit, for establishing and controlling a charging session with an electric vehicle;c) a high-voltage DC voltage measurement chain for measuring the electrical potentials of the positive and negative poles of a DC bus relative to a protective earth, andd) an insulation monitoring device circuit, controlled by said processing unit and in functional relationship with said high-voltage DC voltage measurement chain, comprising at least one switchable electric discharge branch for controllably creating an impedance path between one of the DC bus poles and the protective earth.

11. The charging station according to claim 10, characterized in that said processing unit is configured for both monitoring the DC bus voltage during the charging operation and for determining the insulation resistance by measuring voltage changes when said discharge branch is activated.

12. The charging station according to claim 10 or 11, further comprising a communication interface for receiving partial current measurements from one or more external power modules, wherein said processing unit is further configured to calculate total electric power and energy by combining a sum of the received partial current measurements with the voltage measured by said high voltage DC voltage measurement chain, thereby performing a virtual e- meter function.

13. The charging station according to any of claims 1 to 12, characterized in that it comprises a charging cable (26) comprising a connector configured to be connected to the positive and negative poles of a battery, and wherein said connector houses a temperature sensor.

14. The charging station according to any of claims 1 to 13, characterized in that said supply equipment communication controller is configured to communicate with the electrical vehicle and with the charging network to coordinate the charging operation as well as the billing of the current drawn from the grid into the battery, in the case of grid-to-battery operation, or from the battery into the grid, in the case battery-to-grid operation in bi-directional charging stations.

15. The charging station according to any of claims 1 to 14, characterized in that said supply equipment communication controller is configured for cryptographic signing of energy records.

16. A method for monitoring insulation resistance using a charging station according to claim 11 to 15, said method comprising the steps of:a) measuring a first set of DC bus pole voltages using the high voltage DC voltage measurement chain while at least one discharge branch is in an open state;b) closing a switch in the at least one discharge branch to introduce a known impedance;c) measuring a second set of DC bus pole voltages; andd) calculating, by said processing unit, the insulation resistance based on the difference between the first and second sets of measured voltage.

17. The method according to claim 16, further comprising the steps of:- measuring the initial rate of change of said DC bus pole voltages during step a) or step c);- estimating an RC time constant of the connected electrical system based on said rate of change;- dynamically adjusting a duration for the voltage measurements based on the estimated RC time constant to optimize measurement accuracy and speed, in particular during pre-charge phases of the charging session.

18. The method according to claim 16 or 17, further comprising the steps of:- comparing the measured voltage values against a predicted voltage model; and- discarding the calculated insulation resistance value if the measured values deviate from the predicted model by more than a predetermined threshold, thereby rejecting unreliable measurements, in particular when charging converters are unloaded.

19. A method for performing diagnostics with the charging station (22) according to any of claims 1 to 15, said method comprising the steps of: a) logging, by said processing unit, communication fault events detected by said supply equipment communication controller module,b) logging, by said processing unit, insulation fault events detected by said insulation monitoring device, andc) triggering a diagnostic routine when a communication fault and an insulation fault are logged within a predefined time window of each other, thereby correlating said communication fault events and said insulation fault events.

20. A method for metering performed by the charging station according to any of claim 12 to 15, comprising the steps of:a) periodically requesting and receiving partial current measurements from a plurality of power modules connected to said DC bus;b) summing the partial current measurements to determine a total charging current; andc) calculating total power by multiplying the total charging current by the voltage measured via the high voltage DC voltage measurement chain.

21. The method according to claim 20, further comprising the steps of:- formatting the calculated total power and energy data into a standard meter protocol; and- transmitting said formatted data over a communication interface to emulate the output of a physical e-meter device.

22. The method according to claim 20, further comprising the steps of:- receiving a temperature measurement from a sensor located in the charging connector;- calculating an adjusted resistance value from the charging cable (26) based on the temperature measurement and a known baseline resistance;- calculating the voltage drop and power loss in said charging cable (26) using the total charging current and the adjusted charging cable resistance; and - compensating the calculated total power to determine the actual power delivered to the vehicle’s battery terminals.

23. The method according to any of claims 20 to 22, further comprising cryptographic signing of energy records.

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