JP7797940B2 - Power conversion device sensor system - Google Patents

Description

This disclosure relates to a sensor system for a power conversion device.

JP 2009-138521 A (Patent Document 1) discloses that in an electric compressor integrally assembled with an inverter that controls an electric motor as a drive source, the temperature of an accessory component of the inverter (for example, a smoothing capacitor) is detected, and if the detected temperature is equal to or higher than the maximum rated temperature of the accessory component, the input current is limited and the rotation speed of the electric compressor is restricted.

JP 2009-168521 A

In an electric compressor, the current, voltage, temperature, and other conditions of the power conversion device, such as the inverter, are important values when controlling the electric compressor, and these values are detected/measured to control the electric motor. In Patent Document 1, the temperature value of the space in which the accessory is stored and the value of the current flowing through the accessory (for example, a smoothing capacitor) are used to determine whether to control the power conversion device and limit the input current to the accessory.

In order to properly control a power conversion device, it is desirable to accurately measure temperature, current, etc. based on the output signal (output value) of a sensor installed in the power conversion device.

The purpose of this disclosure is to provide a sensor system for a power conversion device that can accurately measure specified measurement quantities, such as temperature and current, based on the output values of sensors installed in the power conversion device.

The sensor system for a power conversion device disclosed herein is a sensor system for a power conversion device that includes a sensor system that measures a measurand within a measurement range based on the output value of a sensor provided in the power conversion device. The sensor is capable of measuring the measurand within a range up to a certain upper limit in output value, and the narrower the measurable range, the higher the sensor's detection sensitivity is defined. The sensor system includes multiple sensors for measuring the measurand within the entire measurement range, and a measurement unit that, when the measurable ranges of the multiple sensors overlap and the measurand is within the measurable range, determines the measurand based on the output value from the sensor with the highest detection sensitivity.

According to this configuration, the power conversion device includes a sensor system that measures the measurand within a measurement range based on the output value of a sensor provided in the power conversion device. The sensor is capable of measuring the measurand within a range up to a certain upper limit of its output value, with the narrower the measurable range, the higher the detection sensitivity. The sensor system includes multiple sensors for measuring the measurand within the entire measurement range. When the measurable ranges of the multiple sensors overlap and the measurand is within the measurable range, the measurement unit of the sensor system determines the measurand based on the output value from the sensor with the highest detection sensitivity.

The higher (greater) the detection sensitivity of the sensor output value to the measured quantity, the better the detection accuracy of the measured quantity. When the measurable ranges of multiple sensors overlap and the measured quantity is within the measurable range, the measurement unit of the sensor system determines the measured quantity based on the output value from the sensor with the highest detection sensitivity, thereby improving the detection accuracy of the measured quantity.

Preferably, the detection sensitivity may be the slope of the output value relative to the amount to be measured.
According to this configuration, when multiple sensors whose output values are linear with respect to the quantity to be measured are provided, the quantity to be measured is measured using the output value of the sensor whose output value slope with respect to the quantity to be measured (gain (sensitivity of output to input (slope of the graph)) is the largest), so the quantity to be measured can be measured with high accuracy.

Preferably, the detection sensitivity has a first slope where the slope of the output value relative to the measured quantity is large, and a second slope where the slope is smaller than the first slope, and the measurement unit may measure the measured quantity using the output value of the sensor with the largest slope in the first slope.

Although it is preferable for the sensor output value to be linear, it may also be nonlinear, with a first slope where the output value has a large slope relative to the measured quantity, and a second slope where the slope is smaller than the first slope. In this case, the amount of change in the output value relative to the measured quantity in the nonlinear region (region with the second slope) is smaller than in the linear region (region with the first slope), which may result in larger detection errors. With this configuration, the measurement unit measures the measured quantity using the output value of the sensor with the largest slope in the first slope. Therefore, the measured quantity can be measured using the output value of the sensor that is in the linear region and has the greatest detection sensitivity, allowing for accurate measurement of the measured quantity.

Preferably, the detection sensitivity is a slope of the output value relative to the measured quantity. The plurality of sensors include a first sensor having a slope connecting a first point corresponding to the minimum value of the measured quantity and the minimum value of the output value, and a second sensor having a slope greater than the slope of the first sensor. The measurement unit may measure the measured quantity using an output value of the second sensor based on the output value of the first sensor.

With this configuration, the first sensor measures the quantity to be measured between the first point, which is the minimum value of the quantity to be measured, and the second point, which is the maximum value of the quantity to be measured, i.e., over the entire measurement range. Because the second sensor has a larger slope than the first sensor, the second sensor measures the quantity to be measured over a portion of the entire measurement range. To enable the second sensor to measure the entire measurement range, the detection circuit of the second sensor may be switched, for example, so that the second sensor has a larger slope than the first sensor, or multiple second sensors may be provided. With this configuration, the quantity to be measured can be measured using the output value of the second sensor while referencing the output value of the first sensor, allowing for accurate measurement of the quantity to be measured.

Preferably, the power conversion device may be an inverter that drives the motor of the electric compressor.

According to the present disclosure, it is possible to accurately measure specified measurands such as temperature and current based on the output values of sensors installed in a power conversion device.

1 is a diagram showing the overall configuration of a vehicle air conditioner AC to which an electric compressor 100 according to the present embodiment is applied. FIG. 2 is a schematic diagram of an inverter 50. 6A and 6B are diagrams illustrating output characteristics of a current sensor 60a1 and a current sensor 60a2. FIG. 10 is a diagram showing output characteristics in a current detection unit 60a equipped with three current sensors. FIG. 4 is a diagram showing the output characteristics of a temperature detection unit 80. FIG. 4 is a diagram showing the output characteristics of a voltage detection unit 70.

Embodiments of the present disclosure will now be described in detail with reference to the drawings. Note that identical or corresponding parts in the drawings will be designated by the same reference numerals, and their description will not be repeated.

Figure 1 is an overall configuration diagram of a vehicle air conditioner AC that uses an electric compressor 100 according to this embodiment. The vehicle air conditioner AC is mounted on a vehicle and is configured to cool and heat the vehicle interior. The vehicle air conditioner AC includes the electric compressor 100, an external cooling circuit 200, and an air conditioning ECU (Electronic Control Unit) 300.

The external cooling circuit 200 is configured to supply refrigerant to the electric compressor 100 and includes, for example, a heat exchanger and an expansion valve. The electric compressor 100 is configured to compress the refrigerant supplied from the external cooling circuit 200. The vehicle air conditioner AC compresses the refrigerant using the electric compressor 100, and the refrigerant undergoes heat exchange and expansion using the external cooling circuit 200. This provides heating and cooling for the vehicle cabin.

The air conditioning ECU 300 has a built-in CPU (Central Processing Unit) and memory (not shown), and controls the various components of the vehicle air conditioner AC based on information stored in the memory and information from various sensors (not shown). The air conditioning ECU 300 can, for example, recognize the temperature set by the user for air conditioning in the vehicle cabin, as well as the current temperature in the vehicle cabin. The air conditioning ECU 300 outputs various commands, such as on/off commands, to the electric compressor 100 based on these parameters, for example.

The electric compressor 100 includes a housing 10, a compression section 20, an electric motor 30, and an inverter unit 40. The electric compressor 100 can be connected to a battery 90 mounted on the vehicle via a cable 95, and is configured to receive a supply of DC power from the battery 90.

The housing 10 is generally cylindrical and houses the compression section 20 and the electric motor 30. The housing 10 is formed with an intake port 11a through which refrigerant is drawn from the external cooling circuit 200, and a discharge port 11b through which refrigerant is discharged.

The compression unit 20 is configured to compress the refrigerant drawn in through the intake port 11a and discharge the compressed refrigerant from the discharge port 11b. The compression unit 20 may be of any type, including a scroll type, piston type, or vane type.

The electric motor 30 is configured to drive the compression section 20. The electric motor 30 includes, for example, a rotating shaft 31, a rotor 32, and a stator 33. The rotating shaft 31 is cylindrical and rotatably supported relative to the housing 10. The rotor 32 is cylindrical and fixed to the rotating shaft 31. The stator 33 is fixed to the housing 10. The rotor 32 and the stator 33 face each other radially of the rotating shaft 31. The stator 33 includes a cylindrical stator core 34 and a coil 35. The coil 35 is formed by winding it around the teeth of the stator core 34. The electric motor 30 is an AC rotating electric machine, and may be, for example, an IPM (Interior Permanent Magnet) synchronous motor in which a permanent magnet is embedded in the rotor 32.

The inverter unit 40 consists of an inverter 50 housed in a case 41. The inverter 50 is a power conversion device that drives the electric motor 30. The inverter 50 converts DC power supplied from the battery 90 into AC power and supplies the converted AC power to the electric motor 30.

The case 41 includes a plate-shaped base member 42 and a cylindrical cover member 43 with a bottom. The cover member 43 is attached to the base member 42. The base member 42 and cover member 43 are fixed to the housing 10 with bolts 44. A connector 54 is provided on the outer surface of the case 41, and the circuit board 55 and the connector 54 are electrically connected.

The connector 54 is configured to connect to a cable 95. DC power is supplied from the battery 90 to the inverter 50 via the connector 54 and the cable 95.

The inverter 50 includes power semiconductors and various circuits mounted on a circuit board 55. Additionally, various sensors such as a current detector 60, voltage detector 70, and temperature detector 80 are mounted on the circuit board 55 using wiring patterns, and are electrically connected to the power semiconductors and various circuits. In this embodiment, the control ECU 400 is also mounted on the circuit board 55.

Figure 2 is a schematic diagram of the inverter 50. The inverter 50 is connected to the battery 90 via a connector 54 and a cable 95. A capacitor C is provided between the inverter 50 and the battery 90, connected between the power lines PL and NL. The capacitor C smoothes the battery voltage and supplies it to the inverter 50. The voltage detection unit 70 detects the voltage across the capacitor C, i.e., the voltage VB between the power lines PL and NL connecting the battery 90 and the inverter 50, and outputs a signal indicating the detection result to the control ECU 400.

The inverter 50 converts DC power supplied from the battery 90 into AC power and supplies it to the electric motor 30. The inverter 50 includes a U-phase arm 51, a V-phase arm 52, and a W-phase arm 53. The phase arms are connected in parallel between the power lines PL and NL. The U-phase arm 51 has switching elements Q1 and Q2 connected in series. The V-phase arm 52 has switching elements Q3 and Q4 connected in series. The W-phase arm 53 has switching elements Q5 and Q6 connected in series. Diodes D1 to D6 are connected in anti-parallel between the collector and emitter of each of the switching elements Q1 to Q6. The switching elements Q1 to Q6 are, for example, insulated gate bipolar transistors (IBGTs) or metal-oxide-semiconductor field-effect transistors (MOSFETs), which are examples of power semiconductors. In the case of MOSFETs, body diodes are used for the diodes D1 to D6.

The midpoint of each phase arm is connected to the respective phase end of the respective phase coil of the electric motor 30. The midpoint of switching elements Q1 and Q2 is connected to one end of the U-phase coil of the electric motor 30. The midpoint of switching elements Q3 and Q4 is connected to one end of the V-phase coil of the electric motor 30. The midpoint of switching elements Q5 and Q6 is connected to one end of the W-phase coil of the electric motor 30. The other ends of the three coils of the U-phase, V-phase, and W-phase of the electric motor 30 are commonly connected to the neutral point.

When voltage VB (battery voltage) is supplied to inverter 50, it converts DC voltage into AC voltage and drives electric motor 30 by switching elements Q1 to Q6 in accordance with control signals S1 to S6 from control ECU 400. As a result, electric motor 30 is controlled by inverter 50 to generate torque in accordance with torque command value Trqcom.

The inverter 50 is provided with a current detection unit 60 (see FIG. 1). In this embodiment, as shown in FIG. 2, a current detection unit 60d is provided to detect the current supplied from the battery 90 to the inverter 50, and current detection units 60a, 60b, and 60c are provided to detect the three-phase currents (motor currents) iu, iv, and iw flowing through the electric motor 30. The detection signals of each current detection unit are output to the control ECU 400. The current detection unit 60d, which detects the current supplied from the battery 90 to the inverter 50, may be provided on either the power line PL or the power line NL. The current supplied to the inverter 50 may also be calculated from the three-phase currents (motor currents) iu, iv, and iw. Note that the current detection unit that detects the three-phase currents may detect two-phase currents, since the current of the other phase can be calculated by detecting two-phase currents.

The rotation angle sensor (resolver) 65 detects the rotation angle θ of the electric motor 30 and outputs a signal indicating the detection result to the control ECU 400. The rotation speed (rotational speed) NM of the electric motor 30 can be detected from the rate of change of the rotation angle θ detected by the rotation angle sensor 65. Note that drive control of the electric motor 30 may be sensorless control without the resolver 65.

Control ECU 400 includes a CPU, memory, and input/output buffers (not shown), and controls the operation of inverter 50 based on torque command value Trqcom output from air conditioning ECU 300, voltage VB detected by voltage detection unit 70, three-phase currents iu, iv, iw from current detection units 60a to 60c, and rotation angle θ from rotation angle sensor 65, so that electric motor 30 outputs torque according to torque command value Trqcom. That is, control ECU 400 generates control signals S1 to S6 for controlling inverter 50 and outputs them to inverter 50.

The control ECU 400 includes a measurement unit 401 as a functional block. The measurement unit 401 detects/measures the measured quantity using the output values (output signals) of the sensors provided in the current detection unit 60, voltage detection unit 70, and temperature detection unit 80, as described below.

The temperature detection unit 80 detects the temperature Ts of the inverter 50 (the temperature of the switching elements Q1-Q6, diodes D1-D6, etc.). If the temperature Ts exceeds the allowable temperature, for example, the torque command value Trqcom is limited to suppress temperature rise in the inverter 50. The temperature Ts may also be used for temperature compensation of various circuits.

In this embodiment, the current detection unit 60 (60a-60d), voltage detection unit 70, and temperature detection unit 80 are composed of multiple sensors that detect the same measured quantity (current, voltage, or temperature at the same location).

(Embodiment 1)
For example, the current detection unit 60a that detects the three-phase current iu is composed of a current sensor 60a1 and a current sensor 60a2 (neither of which are shown in the figure) that detect the three-phase current iu. FIG. 3 is a diagram showing the output characteristics of the current sensors 60a1 and 60a2. In FIG. 3, the horizontal axis represents the magnitude of the current, with the positive value representing the current flowing from the inverter 50 to the electric motor 30. In FIG. 3, the vertical axis represents the output voltage (output value). The solid line represents the output characteristics of the current sensor 60a1, where the output voltage at -α [A] is 0 [V], the output voltage at 0 [A] is 2.5 [V], and the output voltage at α [A] is 5 [V]. The dashed-dotted line represents the output characteristics of the current sensor 60a2, where the output voltage at -α [A] is 0 [V], the output voltage at 0 [A] is 5 [V] or 0 [V], and the output voltage at α [A] is 5 [V]. When the direction of the current is reversed, the detection circuit of current sensor 60a2 is switched so as to have the characteristics shown in Fig. 3. In Fig. 3 , the measurement range of current detection unit 60a is from -α [A] to α [A]. As shown in Fig. 3, the output characteristics (changes in output value relative to current (measured quantity)) of current sensors 60a1 and 60a2 are linear.

As shown in Figure 3, current detection unit 60a, which detects three-phase current iu, detects currents ranging from -α [A] to α [A] using current sensors 60a1 and 60a2. The gain of current sensor 60a1 (sensitivity of the output value to the current (measured quantity) (slope of the graph/detection sensitivity)) is 2α [A]/5 [V]. The gain of current sensor 60a2 is α [A]/5 [V]. Current sensors 60a1 and 60a2 are sensors capable of measuring the measured quantity (three-phase current iu) up to the output voltage (output value) reaching a certain upper limit (5 [V]). The measurable range of current sensor 60a1 is 2α [A] (-α [A] to α [A]), and the measurable range of current sensor 60a2 is α [A]. Therefore, the narrower the measurable range, the higher the detection sensitivity (the higher the gain) of the sensor.

The higher the sensor gain, the greater the change in output value in response to a change in the measured quantity, resulting in better detection accuracy for the measured quantity (current). However, a high sensor gain can exceed the usable range of the output value (5 V in this embodiment). For this reason, the current detection unit 60a combines a high-gain sensor (current sensor 60a2) with a low-gain sensor (current sensor 60a1) to reliably detect currents from -α [A] to α [A], and the measurement unit 401 of the control ECU 400 uses the detection signal (output voltage) of current sensor 60a2 to accurately detect the three-phase current iu.

In the current detection unit 60a, the output voltage of current sensor 60a2 outputs the same value whether the current value is positive (0 to α [A]) or negative (-α to 0 [A]). Therefore, when the output voltage of current sensor 60a1 is 0 to 2.5 [V], the measurement unit 401 of the control ECU 400 measures the three-phase current iu assuming that the output voltage of current sensor 60a2 is a current value between -α [A] and 0 [A]. Furthermore, when the output voltage of current sensor 60a1 is 2.5 to 5 [V], the measurement unit 401 measures the three-phase current iu assuming that the output voltage of current sensor 60a2 is a current value between 0 [A] and α [A]. In this way, by referencing the output voltage of current sensor 60a1, currents between -α [A] and α [A] are detected by current sensor 60a2. Therefore, the measured quantity (current) can be detected using the output value of the sensor (current sensor 60a2) that has high sensitivity to the measured quantity (current), allowing the measured quantity (current) to be detected with high accuracy.

Fault diagnosis can also be performed by comparing the output voltage (output value) of current sensor 60a1 with the output voltage (output value) of current sensor 60a2. For example, if the output value of current sensor 60a2 does not change despite a change in the output voltage of current sensor 60a1, it can be diagnosed that current sensor 60a2 is faulty (e.g., broken). In this case, the output voltage of current sensor 60a1 can be used to measure (detect) the three-phase current iu. In this embodiment, the same measured quantity (three-phase current iu) is detected from -α [A] to α [A] using current sensor 60a1 and current sensor 60a2.

(Embodiment 2)
The current detection unit 60a may be configured to include three or more current sensors. Fig. 4 is a diagram showing the output characteristics of the current detection unit 60a including three current sensors. In this example, the current sensor 60a that detects the three-phase current iu includes a current sensor 60a1, a current sensor 60a2, and a current sensor 60a3.

In Figure 4, the solid line indicates the output characteristics of current sensor 60a1, as in the example shown in Figure 3, where the output voltage at -α [A] is 0 [V], the output voltage at 0 [A] is 2.5 [V], and the output voltage at α [A] is 5 [V]. The dashed-dotted line indicates the output characteristics of current sensor 60a2, as in the example shown in Figure 3, where the output voltage at -α [A] is 0 [V] and the output voltage at 0 [A] is 5 [V]. Note that in this embodiment, current sensor 60a2 does not have a configuration that switches the detection circuit to achieve the characteristics shown in Figure 3 when the current direction reverses. The two-dot-dashed line indicates the output characteristics of current sensor 60a3, where the output voltage at 0 [A] is 0 [V] and the output voltage at α [A] is 5 [V]. As shown in Figure 4, the output characteristics of current sensors 60a1 to 60a3 (changes in output value relative to current (measured quantity)) are linear.

As shown in Figure 4, the gain of current sensor 60a1 is 2α [A]/5 [V]. The gain of current sensors 60a2 and 60a3 is α [A]/5 [V]. The higher the sensor gain, the greater the change in output value relative to a change in the measured quantity, resulting in better detection accuracy for the measured quantity (current). Therefore, in this embodiment, the measurement unit 401 of the control ECU 400 detects the three-phase current iu for currents between -α [A] and 0 [A] using the detection signal (output voltage) of current sensor 60a2. Furthermore, the measurement unit 401 detects the three-phase current iu for currents between 0 [A] and α [A] using the output value of current sensor 60a3. Therefore, by detecting the measured quantity (current) using the output values of sensors (current sensors 60a2 and 60a3) that are highly sensitive to the measured quantity (current), the measured quantity (current) can be detected with high accuracy.

In this embodiment, too, fault diagnosis can be performed by comparing the output voltages of current sensor 60a1, current sensor 60a2, and current sensor 60a3. Furthermore, even if one of the current sensors fails, a redundant sensor system can be provided in which the remaining current sensors can detect the three-phase current iu.

In this embodiment, the same measured quantity (three-phase current iu) is detected from -α [A] to 0 [A] using current sensor 60a1 and current sensor 60a2, and the same measured quantity (three-phase current iu) is detected from 0 [A] to α [A] using current sensor 60a1 and current sensor 60a3.

(Embodiment 3)
5 is a diagram showing the output characteristics of the temperature detection unit 80. The temperature detection unit 80 is composed of a temperature sensor 801 and a temperature sensor 802 (not shown). The temperature sensors 801 and 802 may be temperature sensors made up of NTC (Negative Temperature Coefficient) thermistors.

In Figure 5, the horizontal axis represents temperature and the vertical axis represents output voltage (output value). The solid line represents the output characteristics of temperature sensor 801, which can detect temperatures from -40°C to t1°C. The dashed line represents the output characteristics of temperature sensor 802, which can detect temperatures from -t0°C to 150°C. As shown in Figure 5, the output characteristics of temperature sensor 801 (solid line) are nonlinear, but are in a linear region from approximately -40°C to 0°C. Above 0°C, the amount of change (slope of the graph) with respect to temperature (measured quantity) enters a nonlinear region where the amount of change (slope of the graph) with respect to temperature (measured quantity) is smaller than the linear region. Similarly, the output characteristics of temperature sensor 802 (dashed line) are nonlinear, but are in a linear region from approximately -t0°C to t2°C. Above t2°C, the amount of change (slope of the graph) with respect to temperature (measured quantity) enters a nonlinear region where the amount of change (slope of the graph) with respect to temperature (measured quantity) is smaller than the linear region. If the slope of the graph in the linear region is called the first slope and the slope of the graph in the nonlinear region is called the second slope, the second slope is smaller than the first slope.

In this embodiment, the measurement unit 401 of the control ECU 400 measures the temperature Ts of the inverter 50 using the output voltage (output value) of the temperature sensor 801 when the output voltage of the temperature sensor 801 is 4 V or less (indicating 0°C or less). Then, when the output voltage of the temperature sensor 801 exceeds 4 V, the measurement unit 401 measures the temperature Ts of the inverter 50 using the output voltage (output value) of the temperature sensor 802.

When the output characteristic of temperature sensor 801 is above 0°C, it enters a nonlinear region (second slope), and the amount of change in output voltage with respect to temperature change is smaller than in the linear region (first slope). Therefore, in the nonlinear region, measurement variation of temperature Ts increases, and measurement (detection) accuracy deteriorates. In this nonlinear region, the output characteristic of temperature sensor 802 is linear, and the amount of change in output voltage with respect to temperature change is greater than that of temperature sensor 801. Therefore, in this nonlinear region, the measurement accuracy of temperature Ts can be ensured by measuring temperature Ts using the output voltage of temperature sensor 802.

Temperature Ts can also be measured using temperature sensor 803 with output characteristics as indicated by the dashed line in FIG. 5 . In this case, because the gain of temperature sensor 803 is relatively small, it is preferable to use temperature sensor 801 with a high gain to improve the measurement accuracy of temperature Ts. However, a high sensor gain would exceed the usable output value range (5 V in this embodiment) for the temperature range to be measured. Therefore, in this embodiment, high-gain temperature sensor 801 is combined with a relatively high-gain temperature sensor 802 to reliably detect temperatures from −40°C to 150°C. Then, measurement unit 401 of control ECU 400 measures temperatures Ts below 0°C using the output voltage (output value) of temperature sensor 801 and measures temperatures above 0°C using the output voltage ( output value ) of temperature sensor 802, thereby ensuring the measurement accuracy of temperature Ts.

In this embodiment, the same measured quantity (temperature Ts) is detected using temperature sensor 801 and temperature sensor 802 from -40°C to t1°C. Note that within this temperature range, fault diagnosis can be performed by comparing the output voltages of temperature sensor 801 and temperature sensor 802, as described above. Furthermore, even if one of the temperature sensors fails, a redundant sensor system can be provided in which temperature Ts can be detected using the remaining temperature sensor.

While the above embodiment describes the current detection unit 60a and the temperature detection unit 80, the current detection units 60b-60d and the voltage detection unit 70 may also be provided with multiple sensors with different sensitivities (gains) to the measured quantity, and the measured quantity (current, voltage) may be measured using the output value of the sensor with the larger gain. For example, voltage VB may be measured using a voltage detection unit 70 with output characteristics as shown in Figure 6. Figure 6 shows the output characteristics of the voltage detection unit 70. The voltage detection unit 70 includes four voltage sensors 701-704 (not shown) with different gains. In Figure 6, the output characteristics of voltage sensor 701 are shown by a solid line, the output characteristics of voltage sensor 702 by a dashed line, the output characteristics of voltage sensor 703 by a dashed line, and the output characteristics of voltage sensor 704 by a two-dot chain line. In this example, the output characteristics of voltage sensors 701-704 are linear. The measurement unit 401 of the control device 400 measures voltage VB by measuring 0 to v1 [V] using the output value of voltage sensor 701, measuring v1 to v2 [V] using the output value of voltage sensor 702, measuring v2 to v3 [V] using the output value of voltage sensor 703, and measuring v3 to VT [V] using the output value of voltage sensor 704. A voltage detection unit 70 configured in this way also measures (detects) voltage VB accurately because it includes multiple voltage sensors 701 to 704 that detect voltage VB, and a measurement unit 401 that measures voltage VB using the output value of the voltage sensor with the greatest sensitivity (gain) to voltage VB among the output values of the multiple voltage sensors 701 to 704.

The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims, not by the description of the above embodiments, and is intended to include all modifications within the meaning and scope of the claims.

10 Housing, 11a Intake port, 11b Discharge port, 20 Compression section, 30 Electric motor, 31 Rotating shaft, 32 Rotor, 33 Stator, 34 Stator core, 35 Coil, 40 Inverter unit, 41 Case, 42 Base member, 43 Cover member, 44 Bolt, 50 Inverter, 51 U-phase arm, 52 V-phase arm, 53 V-phase arm, 54 Connector, 55 Circuit board, 60 Current detection section, 60a to 60d Current sensors, 65 Rotation angle sensor, 70 Voltage detection section, 80 Temperature detection section, 90 Battery, 95 Cable, 100 Electric compressor, 200 External cooling circuit, 300 Air conditioning ECU, 400 Control ECU, 401 Measurement section, AC Vehicle air conditioning device, C Capacitor, D1 to D6 Diodes, NL Power line, PL Power line, Q1 to Q6 switching elements.

Claims (4)

A sensor system for a power conversion device, comprising a sensor system that measures a measurand within a measurement range based on an output value of a sensor provided in the power conversion device,
The sensor is a sensor that can measure the measurand within a range up to when the output value reaches a certain upper limit, and the narrower the measurable range, the higher the detection sensitivity of the sensor is defined as;
The sensor system includes:
a plurality of the sensors for measuring the measurand over a full measurement range;
a measurement unit that, when the measurable ranges of the plurality of sensors overlap and the amount to be measured is within the measurable ranges, determines the amount to be measured based on the output value from the sensor with the highest detection sensitivity;
the detection sensitivity is a gradient of the output value relative to the measured quantity,
the plurality of sensors include a first sensor having a slope connecting a first point where the minimum value of the measurand and the minimum value of the output value and a second point where the maximum value of the measurand and the maximum value of the output value over the entire measurement range, and a second sensor having a slope greater than the slope of the first sensor,
the second sensor is capable of measuring the measurand over the entire measurement range;
The measurement unit measures the measured quantity from the output value of the second sensor over the entire measurement range based on the output value of the first sensor. The sensor system for a power conversion device described in claim 1, wherein the sensor system switches the detection circuit of the second sensor to measure the measured quantity from the output value of the second sensor over the entire measurement range. A sensor system for a power conversion device, comprising a sensor system that measures a measurand within a measurement range based on an output value of a sensor provided in the power conversion device,
The sensor is a sensor that can measure the measurand within a range up to when the output value reaches a certain upper limit, and the narrower the measurable range, the higher the detection sensitivity of the sensor is defined as;
The sensor system includes:
a plurality of the sensors for measuring the measurand over a full measurement range;
a measurement unit that, when the measurable ranges of the plurality of sensors overlap and the amount to be measured is within the measurable ranges, determines the amount to be measured based on the output value from the sensor with the highest detection sensitivity;
the detection sensitivity is a gradient of the output value relative to the measured quantity,
the plurality of sensors include a first sensor having a slope connecting a first point at which the minimum value of the measurand and the minimum value of the output value and a second point at which the maximum value of the measurand and the maximum value of the output value over the entire measurement range, and two second sensors having a slope greater than the slope of the first sensor;
Two second sensors are provided,
one of the second sensors measures the measurand including the first point, and the other second sensor measures the measurand including the second point, thereby dividing the entire measurement range by the two second sensors and making it possible to measure the measurand in the entire measurement range;
The measurement unit measures the measured quantity from the output value of the second sensor over the entire measurement range based on the output value of the first sensor . The power conversion device sensor system of any one of claims 1 to 3, wherein the power conversion device is an inverter that drives the motor of an electric compressor.