阅读说明：本技术 电流测量方法和电流测量装置 (Current measuring method and current measuring device ) 是由 阿卜德勒拉希姆·查希德 因戈尔夫·霍夫曼 亚历山大·艾特茨克 罗兰德·韦斯 于 2018-04-04 设计创作，主要内容包括：本发明涉及一种借助于电流测量装置测量电流的方法,其中电流测量装置(1)具有至少两个第一类型的传感器(11)和至少两个第二类型的传感器(12)。为了改进测量精度而提出,第一类型的传感器(11)是磁通门磁场传感器且第二类型的传感器(12)是霍尔传感器。第一类型的传感器(11)的灵敏度比第二类型的传感器(12)更高,其中,第一传感器(11)径向对称地布置在第一环绕轨道上,特别是椭圆或第一圆形路径(K<Sub>1</Sub>)上,并且第二传感器(12)径向对称地布置在第二环绕轨道上,特别是椭圆形的或第二圆形路径(K<Sub>2</Sub>)上,其中第一类型的传感器(11)各自布置成相邻于第二类型的传感器(12)。为了确定电流强度,如果至少两个第一类型的传感器(11)的测量值处于测量范围内,则第一类型的传感器(11)中的至少一个传感器被评估,否则评估至少一个第二类型的传感器(12)。(The invention relates to a method for measuring a current by means of a current measuring device, wherein the current measuring device (1) has at least two sensors (11) of a first type and at least two sensors (12) of a second type. In order to improve the measurement accuracy, it is proposed that the sensor (11) of the first type is a fluxgate magnetic field sensor and the sensor (12) of the second type is a Hall sensor. The sensitivity of the sensors (11) of the first type is higher than that of the sensors (12) of the second type, wherein the first sensors (11) are arranged radially symmetrically on a first circumferential path, in particular an elliptical or first circular path (K1), and the second sensors (12) are arranged radially symmetrically on a second circumferential path, in particular an elliptical or second circular path (K2), wherein the sensors (11) of the first type are each arranged adjacent to a sensor (12) of the second type. For determining the current intensity, at least one of the sensors (11) of the first type is evaluated if the measured values of at least two sensors (11) of the first type are within the measuring range, and at least one sensor (12) of the second type is evaluated otherwise.)

1. A method for measuring a current by means of a current measuring device, wherein the current measuring device (1) has:

-at least two sensors (11) of a first type,

At least two sensors (12) of a second type,

Wherein the first type of sensor (11) is a fluxgate magnetic field sensor and the second type of sensor (12) is a Hall sensor, wherein the first type of sensor (11) has a higher sensitivity than the second type of sensor (12), wherein the first sensor (11) is arranged radially symmetrically on a first encircling track, in particular an elliptical or first circular path (K1), and the second sensor (12) is arranged radially symmetrically on a second encircling track, in particular an elliptical or second circular path (K2), wherein the first type of sensor (11) is arranged adjacent to the second type of sensor (12), respectively, wherein, for determining the current strength, at least one of the first type of sensor (11) is evaluated if the measured values of at least two of the first type of sensor (11) are within a measurement range, otherwise, at least one sensor (12) of the second type is evaluated.

2. Method according to claim 1, wherein for determining the current strength, at least one of the sensors (11) of the first type is evaluated if the measured values of all the sensors (11) of the first type are within the measurement range, and the sensor (12) of the second type is evaluated otherwise.

3. Method according to claim 1 or 2, wherein during the determination of the current intensity by the sensor of the first type (11), a correction value for the offset of the sensor of the second type is derived from the measured values from the sensor of the second type (12) from the current intensity determined by the sensor of the first type (11).

4. The method according to any one of claims 1 to 3, wherein the sensitivity of the first type of sensor (11) is 5 to 20 times higher than the second type of sensor (12).

Technical Field

the invention relates to a method for measuring a current by means of a current measuring device.

Background

Current measuring devices, also referred to as current sensors, are used to measure or determine current at specific locations within an electrical installation. In this case, sensor devices for current measuring devices and corresponding evaluation methods are considered which enable energy-efficient measurement of currents between 400A and 10kA without flux concentrators (flux loops). The sensor device can also be operated without a magnetic circuit and, compared to the prior art, can have an improved sensitivity to interfering conductors parallel to the magnetic field, as are common, for example, in three-phase alternating current systems. Such current sensors can be used for low and medium voltage converters or for battery monitoring. In particular, converters for ships and track drives or wind power installations operate in this current range and are usually designed to be relatively compact, so that high external fields and also superimposed intrinsic fields (eigenfeeders) are common at the current measuring point. As a result of the "open-loop" operation, the measuring range of the sensor arrangement is limited by the measuring range of the individual sensors. In addition, magnetic field sensors with the measurement range required for the maximum field (about 50mT) have a relatively large offset error, much larger than 1% of the maximum value. In this field range, almost only hall sensors work, but hall sensors are known for their offset error. Since the offset error of each sensor varies with temperature and time, additional analog or digital offset stabilization is difficult.

Hitherto, current was measured using shunt resistors, toroidal transformers, Rogowski coils or single field probes (hall probes or GMR sensors). In the currently known measurement configurations, relatively large offset errors and thus low accuracy are acceptable at low currents. It should be mentioned here that it is difficult to simply directly compensate for the observed offset error due to its non-deterministic temporal and significantly non-linear temperature behavior. The measuring range of the sensor device is derived from the measuring ranges of the available individual sensors. Since available hall-technology sensors can achieve very good accuracy in the measurement range of about 25mT and above, and available MR technology instead of them can only achieve sensors with a measurement range of at most lmT, there has been a large gap in the measurement range for "on-chip" magnetic field sensors for a long time. Furthermore, MR sensors lose calibration at magnetic fields greater than about 20mT, so that their accuracy deteriorates significantly.

Disclosure of Invention

The object of the present invention is to provide a current measuring device which can achieve higher accuracy in current measurement.

This object is achieved by a method for measuring a current by means of a current measuring device, wherein the current measuring device has at least two sensors of a first type and at least two sensors of a second type, wherein the sensors of the first type are fluxgate magnetic field sensors and the sensors of the second type are hall sensors, wherein the sensors of the first type have a higher sensitivity than the sensors of the second type, wherein the first sensors are arranged radially symmetrically on a first encircling track, in particular an oval or a first circular path, and the sensors of the second type are arranged radially symmetrically on a second encircling track, in particular an oval or a second circular path, wherein the sensors of the first type are arranged adjacent to the sensors of the second type, respectively, wherein, for determining the current strength, if the measured values of at least two of the sensors of the first type are within a measuring range, at least one sensor of the first type of sensor is evaluated, otherwise at least one sensor of the second type is evaluated.

Further advantageous embodiments of the invention are given in the dependent claims.

the invention is based on the following recognition: the measurement accuracy of the annular arrangement of the individual sensors is improved by arranging the sensors of different types at one or more measurement positions in each case such that they are on the one hand as close as possible to one another and on the other hand all sensors of the same type form an independent, as radially symmetrical measurement arrangement as possible. Here, two sensors of different types are arranged adjacent to one another at one measuring point. This means that they are at a distance from each other that is less than the extension of one of the sensors. In addition to improving measurement accuracy, this arrangement can also extend the measurement range. In this case, the different types of sensors may be arranged tangentially or radially adjacent.

Sensitivity (also referred to as resolution) is understood to be the property by which changes in the measured value can be detected. The higher the sensitivity, the smaller the change in the measured variable that can be detected.

The expansion of the measurement range and the improvement of the measurement accuracy achieved by the measuring device can be achieved by a method for current measurement. These advantages can be achieved here by an advantageous switching method between the different types of sensors. Through studies based on actual measurement data, it has been possible to demonstrate that sensor switching by type is clearly superior to all other methods, taking into account disturbances due to additional current-carrying conductors. Sensor switching by type is achieved by: when a plurality of sensors of the first type, i.e. at least two sensors, each provide a separate effective value in their measurement range, all sensors of the first type with a high sensitivity are always used for calculating the current value. The individually valid measured values are values which lie within the permissible measuring range of the sensor. Otherwise, the second type of sensor is always used to calculate the current value. That is, when at least two sensors of the first type are simultaneously within their magnetic field measurement range, the signals of the sensors of the first type are used for current calculation, otherwise the signals of the sensors of the second type are used for current calculation.

The sensors of the first type and of the second type each form two concentric annular arrangements of sensors which have a parallel orientation of the field sensitivity direction. However, when a single sensor is overloaded, the sensor-by-sensor switching is not performed. In order to obtain good measurement results, a per-type handover is performed. The advantages of this method are an extension of the measurement range, a general improvement of the accuracy and a possible reduction of offset errors.

The first type of sensor is a fluxgate magnetic field sensor and the second type of sensor is a hall sensor. These sensors are available at low cost. Furthermore, their dimensions are correspondingly small, so that they can be easily integrated into a measuring device.

Those skilled in the art know that, as described in, for example, the freely accessible encyclopedia, wikipedia, the measurement ranges are the following ranges of measurement variables: within this range, the measurement deviations remain within the specified limits. The specified margin of error is only valid within a defined measurement range. Beyond the measurement range, accuracy cannot be guaranteed. In the case of fluxgate magnetic field sensors and hall sensors, the measurement range is also given in the data table.

in an advantageous embodiment of the invention, the sensitivity of the sensor of the first type is 5 to 20 times higher than that of the sensor of the second type. It has been shown that particularly low offset errors can be achieved thereby. If the sensitivity of the first type of sensor is 5 to 20 times greater than that of the second type of sensor, a very small offset error can be achieved in practice with respect to the measurement range. The measuring ranges of the individual sensors of different types can thus be staggered in a rational manner, so that the measuring errors are kept low.

In a further advantageous embodiment of the invention, at least one of the sensors of the first type is evaluated for determining the current intensity if the measured values of all sensors of the first type are within the measuring range, and at least one of the sensors of the second type is evaluated otherwise.

This means that, as soon as the measured value of one of the sensors of the first type leaves its measuring range, the current is calculated by at least one sensor of the second type, in particular by a weighted sum of the sensors of the second type. The current value is calculated by at least one of the sensors of the first type, in particular by a weighted sum of the sensors of the first type, only if the measured values of all sensors of the first type come from the effective range. All sensors therefore contribute to an improved current determination and are able to determine measured values with a particularly high accuracy.

In a further advantageous embodiment of the invention, during the determination of the current intensity by the sensor of the first type, a correction value for the offset of the sensor of the second type is derived from the measured values from the sensor of the second type, in particular also from the current intensity determined by the sensor of the first type. If the effective current value is calculated for a first type of sensor, the current of a second type of sensor is also calculated in parallel in one type of ancillary calculation. In both cases and in one of these cases, the calculation can be carried out by a weighted sum of the measured values of the individual sensors. Thereby, a current correction value for the offset of the second type of sensor arrangement is derived. The current measured by the second type of sensor is determined in accordance with the following equation

Thereby obtaining a single value of the correction factor

Advantageously, the correction value Koff, II for the offset of the sensor arrangement of the second type is derived within the maximum possible range of effective values of the sensor arrangement of the first type. In order to correct the current values by means of weighting and correction of the second type of sensor during the active calculation, the average value of the final correction values Koff, II of the offset of the second type of sensor arrangement is used at this time.

Drawings

The invention will be described and explained in more detail hereinafter with reference to an embodiment shown in the drawings. It shows that:

Figure 1 is a first embodiment of a current measuring device,

FIG. 2 is a second embodiment of a current measuring device, an

Fig. 3 is a possible implementation of the method for offset correction.

Detailed Description

fig. 1 shows a first embodiment of a current measuring device 1 surrounding an electrical conductor 2. The current measuring device 1 has a plurality of sensors 11 of a first type and a plurality of sensors 12 of a second type adjacent thereto in each case. In the present embodiment, "adjacent" means that the distance between two sensors is less than the minimum extension of the sensors. These types differ, for example, in their measurement principle. The different types of sensors are arranged on a common circular path K. In this case, it is arranged such that the field orientations 20 measurable by the respective sensors are oriented tangentially to the circular path. In order to be able to evaluate the measurement signals of the individual sensors, the current measuring device 1 has evaluation electronics 13. In order to arrange the measuring device 1 around an electrical conductor in a simple manner, it has proven advantageous to provide an angular opening 21 in the circular structure of the current measuring device 1. The more flexible the current measuring device 1, the smaller the angular opening 21 can be.

Fig. 2 shows a further exemplary embodiment of the current measuring device 1. To avoid repetition, reference is made to the description relating to fig. 1 and the reference numerals introduced therein. In the present embodiment, the different types of sensors are adjacently arranged on different concentric circular paths K1, K2, respectively. In the present embodiment, "adjacent" means that the distance between two sensors is less than the minimum extension of the sensors. With this arrangement, good measurement results similar to those in the structure of the foregoing embodiment can also be obtained.

Fig. 3 shows a flow chart of an advantageous measuring method for offset correction. In a first step 101, current measurements are performed by the first and second type of sensors. In a decision 102, it is checked whether all measured values of the first type of sensor are within the allowed measurement range. If not within the allowed measurement range, the first step 101 is returned to in path N (for no) and a new measurement value is recorded. In another case Y (for which) the measured values of the sensors of the first type are now within the permitted range, in which case the offset KoffB is determined in step 103 from the values of the sensors 12 of the second type. Only when the minimum amount for the KoffB value is reached, an offset value is specified for the second type of sensor in step 105. Otherwise, decision 104 ensures that the determination of new measurement values is continued in step 101.

In summary, the invention relates to a current measuring device. In order to increase the measurement accuracy, it is proposed that the current measuring device has at least two sensors of a first type and at least two sensors of a second type, wherein the sensors of the first type have a higher sensitivity than the sensors of the second type, wherein the first sensors are arranged radially symmetrically on a first circular path and the second sensors are arranged radially symmetrically on a second circular path, wherein the sensors of the first type are each arranged adjacent to a sensor of the second type. The invention further relates to a method for measuring a current with such a current measuring device, wherein, for determining the current intensity, at least one of the sensors of the first type is evaluated if the measured values of at least two sensors of the first type are within the measuring range, and at least one sensor of the second type is evaluated otherwise.