JP2009194974A - Inverter apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inverter apparatus which can start by precisely estimating the position of a magnet rotor, regardless of the temperature of a motor at the time of startup. <P>SOLUTION: When positioning the magnet rotor of a motor for outputting DC current from an inverter circuit to the motor prior to operation of the motor, a resistance value of the stator winding of the motor is calculated based on the current value detected with a current sensor. During startup operation of the motor, the position of the magnet rotor is estimated based on at least the current value detected with the current sensor and the resistance value of the stator winding calculated at positioning. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an inverter device that can accurately estimate and start the position of a magnet rotor regardless of the temperature of a sensorless DC brushless motor.

  A conventional method for positioning the magnet rotor before the motor operation and a method for estimating the position of the magnet rotor during the motor operation will be described below. FIG. 10 shows an electrical circuit diagram of a conventional inverter device 20 and its periphery. Prior to operation, the magnet rotor 5 constituting the sensorless DC brushless motor 11 (hereinafter referred to as a motor) is positioned. The positioning is performed by outputting a direct current from the inverter device 20 to the stator winding 4 constituting the motor 11.

  During operation, the control circuit 7 controls the switching element 2 (IGBT, FET, transistor, etc.) constituting the inverter circuit, so that the DC voltage from the battery 1 is switched by PWM modulation, and is sinusoidal. Is output to the stator winding 4 constituting the motor 11. Thereby, the motor 11 is driven. The diode 3 serves as a circulation route for the current flowing through the stator winding 4. The detected current value of the current sensor 6 is sent to the control circuit 7, used for power consumption calculation, switching element 2 protection, and the like, and further used for position estimation of the magnet rotor 5 described later (for example, Patent Document 1). reference).

  Details of the phase current detection method by the current sensor 6 are omitted. If the phase current for two phases is detected, the phase current for the remaining one phase can be calculated (Kirchhoff's current law is applied at the neutral point of the stator winding 4). As the current sensor 6, a sensor that can detect the peak of the switching current by the switching element 2, such as a sensor using a Hall element, a shunt resistor, or the like is used.

Next, a method for estimating the position of the magnet rotor 5 during operation will be described. FIG. 11 shows a circuit configuration of the stator winding 4 and a relational expression between voltage and current in the U phase. FIG. 12 shows an example of phase characteristics of voltage and current for one phase. Since the induced voltage is a voltage induced in the stator winding 4 by the rotation of the magnet rotor 5 shown in FIG. 10, it is used for estimating the position of the magnet rotor 5. The stator winding 4 also has a resistance R as well as an inductance L. The sum of the induced voltage, the voltage of the inductance L, and the voltage of the resistor R is equal to the applied voltage from the inverter device 20. When the induced voltage is EU, the phase current is iU, and the applied voltage is VU, since VU = EU + R · iU + LdiU / dt, EU = VU−R · iU−LdiU / dt. Therefore, the inductance value L and the resistance value R of the stator winding 4 are programmed, the applied voltage is calculated from the PWM modulation, and the phase current is detected by the current sensor 6, whereby the induced voltage EU is calculated by the above formula. Can be calculated. Thereby, the position of the magnet rotor 5 during operation is estimated.
JP 2004-282848 A (pages 5-6, FIGS. 1-3)

  As described above, in the conventional inverter device, the resistance value of the stator winding is programmed in order to estimate the position of the magnet rotor during operation. This resistance value is a fixed value. On the other hand, since the actual stator winding is composed of a copper wire, the resistance value varies with temperature. Therefore, in calculating the induced voltage accurately (position estimation of the magnet rotor), it is necessary to correct the resistance value of the program according to the temperature of the stator winding.

  Since the current value is large and the resistance voltage drop is large when the motor is started, the influence on the induced voltage calculation is large. Further, since the rotational speed is low and the induced voltage is small when the motor is started, it is necessary to calculate the voltage drop of the resistor with high accuracy. In order to perform accurate control so as not to step out when the motor is started, it is necessary to accurately calculate the induced voltage (accurate position estimation of the magnet rotor). On the other hand, the temperature at the start of the motor is not constant, and there is a cold start and a hot start. In a motor that drives a compressor, particularly a high-pressure compressor, the temperature rise due to continuous operation is large. Therefore, in order to perform optimal startup based on accurate magnet rotor position estimation regardless of cold startup or thermal startup, the resistance value of the program at startup is corrected by the temperature of the stator winding. It is desirable to do.

  However, in order to detect the temperature of the stator winding, it is necessary to provide a temperature sensor, wiring, an interface circuit, and the like. For this reason, an increase in parts and an increase in the size of the motor or the like are caused. In the compressor, it is necessary to add terminals to the temperature sensor for high temperature and high pressure and the electrical connection terminal for the high pressure vessel.

  The present invention solves such a conventional problem, and there is no need to add special parts, and an inverter device capable of accurately estimating and starting the position of the magnet rotor regardless of the motor temperature at the time of starting. For the purpose of provision.

  In order to solve the above problems, an inverter device according to the present invention includes an inverter circuit including an upper arm switching element connected to the plus side of a DC power source and a lower arm switching element connected to the minus side, and an inverter circuit A motor that outputs a motor current to a sensorless DC brushless motor by energization of PWM modulation and a current sensor that detects the motor current, and the control circuit outputs a DC current from the inverter circuit to the motor before the motor is operated. When positioning the magnet rotor, calculate the resistance value of the stator winding of the motor based on the current value detected by the current sensor, and calculate at least the detected current value of the current sensor and positioning during motor start-up operation The position of the magnet rotor of the motor is estimated based on the resistance value of the stator winding.

  Thereby, the resistance value of the stator winding calculated at the time of positioning is used for estimating the position of the magnet rotor during the start-up operation of the motor. That is, the resistance value of the stator winding at the temperature of the stator winding during start-up operation is used. Therefore, it is possible to accurately calculate the induced voltage regardless of the temperature of the stator winding during the start-up operation. In other words, the position of the magnet rotor can be accurately estimated and activated regardless of the motor temperature at the time of activation. In addition, there is no need to add special parts such as a temperature sensor, wiring, and interface circuit, so that the number of parts and the size of the motor are not increased.

  The inverter device of the present invention does not require any special components, and can accurately start and start the position of the magnet rotor regardless of the motor temperature at the time of startup.

  According to a first aspect of the present invention, there is provided an inverter circuit including an upper arm switching element connected to a plus side of a DC power source and a lower arm switching element connected to a minus side, and a motor by energizing PWM modulation to the inverter circuit. A control circuit for outputting a current to a sensorless DC brushless motor and a current sensor for detecting the motor current are provided, and the control circuit positions a magnet rotor of the motor that outputs a direct current from the inverter circuit to the motor before the motor is operated. At the time, the resistance value of the stator winding of the motor is calculated based on the current value detected by the current sensor, and at the start of the motor, at least the detected current value of the current sensor and the stator winding calculated at the time of positioning are calculated. The position of the magnet rotor of the motor is estimated based on the resistance value.

  As a result, the position of the magnet rotor can be accurately estimated and activated regardless of the motor temperature at the time of activation. In addition, there is no need to add special parts such as a temperature sensor, wiring, and interface circuit, so that the number of parts and the size of the motor are not increased.

  The second invention drives the motor of the electric compressor in the inverter apparatus of the first invention. In the compressor, when a temperature sensor is provided, it is necessary to add a terminal to the temperature sensor for high temperature and pressure and the electrical connection terminal for the high pressure vessel. Therefore, the present inverter device that does not require a temperature sensor is useful.

  According to a third aspect of the invention, in the inverter device of the second aspect of the invention, the electric compressor is a high pressure type. In a motor that drives a high-pressure compressor, the temperature rise due to continuous operation is large, so the temperature difference between cold start and hot start becomes large. Therefore, the present inverter device that can accurately estimate and start the position of the magnet rotor regardless of the motor temperature at the time of starting is useful.

  According to a fourth invention, in the inverter device of the second or third invention, the inverter device is mounted on an electric compressor. The electric compressor is increased in size by installing an inverter device. Therefore, it is not necessary to add special parts such as a temperature sensor, wiring, and interface circuit, and the present inverter device that does not increase the number of parts and increase the size of the motor is useful.

  A fifth invention is an inverter device according to the first to fourth inventions, which is mounted on a vehicle. For vehicles, there is a restriction on the mounting space and miniaturization is required, so there is no need to add special parts such as temperature sensors, wiring, interface circuits, etc., which may increase the number of parts and increase the size of motors, etc. This inverter device is not useful. Moreover, since the ambient temperature rises when mounted near the engine, the present inverter device that is able to accurately estimate and start the position of the magnet rotor regardless of the motor temperature at the start is useful.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the embodiment.

(Embodiment 1)
FIG. 1 shows an inverter device 22 according to Embodiment 1 of the present invention and an electric circuit around it. The positioning energization of the magnet rotor 5 before operation will be described below. FIG. 2A shows a case where the magnet rotor 5 is positioned with the U phase and V phase of the stator winding 4 set to the S pole and the W phase set to the N pole in the case of four poles. The N pole of the magnet rotor 5 is positioned on the S pole of the stator winding 4 and the S pole of the magnet rotor 5 is positioned on the N pole of the stator winding 4 so as to be opposed to each other. . At this time, the control circuit 7 of the inverter device 22 controls the switching element 2 so that a current flows from the W phase to the U phase and the V phase of the stator winding 4 as shown in FIG. The control circuit 7 detects the phase current of the motor based on the voltage from the shunt resistor 6.

  FIG. 3 shows an example of the ON period within the carrier cycle of the upper arm switching element at the initial stage of positioning in relation to the above switching. The thin line is the U phase, the middle line is the V phase, and the thick line is the W phase. FIG. 3A shows a case where the energization period is set small in order to gradually increase the current in the initial stage of positioning. In the initial stage of positioning, the energization period is gradually increased as shown in FIGS. 3 (B) and 3 (C). Here, the time until the current has risen (initial positioning) is 50 mS. The stator winding 4 has an inductance L as well as a resistance R. Therefore, the current is gradually increased.

  In FIG. 4, the energization period is set so that a predetermined constant current flows in the stationary positioning period. Approximately 100 ms is executed. As an example, the DC voltage of the battery 1 is DC 300 V, the resistance value R of each phase of the stator winding 4 is 1Ω, and the carrier frequency is 10 kHz (carrier cycle 100 μS). Here, in order to set the phase current value of the W phase in the stationary positioning period to 20 A, since the equivalent resistance value of the stator winding 4 is 1.5Ω, it is necessary to apply a DC equivalent to 30 V. DC30V is 10% of DC300V. Therefore, the total of the first half and the second half displayed as Duty of the energization period, that is, Δt may be set to 10% (10 μS).

  FIG. 5 shows the time course of the W-phase phase current. The current increases in the initial stage of positioning, and the predetermined constant current flows in the stationary positioning period. Here, it is assumed that the temperature of the stator winding 4 is high during positioning, and the resistance value R of each phase of the stator winding 4 is 1, 2Ω. When there is no feedback control of the phase current, the phase current value of the W phase decreases to 16.7 A (20 A / 1.2). Further, when there is phase current feedback control, the phase current value of the W phase does not change at 20 A, but the total of the first half and the second half of the energization period displayed as Duty, that is, Δt, is 12% (12 μS). Thereby, the control circuit 7 calculates that the resistance value R of each phase of the stator winding 4 is 1 or 2Ω. The resistance value of each phase of the stator winding 4 calculated in the stationary positioning period is RS.

  Since the current value for positioning is as large as about 20 A, the current sensor (shunt resistor 6) does not need to detect a small current. Further, since it is direct current, a small resistance value can be easily calculated. And since only the positioning software of the magnet rotor 5 that is always performed before the start-up operation is applied, the addition of the function has a small burden in terms of software.

  Next, the start operation shown in FIG. Although the W-phase current is shown, the U-phase and the V-phase behave in the same way only with different phases. The control circuit 7 calculates the induced voltage of the stator winding 4 by the magnet rotor 5 constituting the motor 11 and estimates the position of the magnet rotor 5. At this time, the resistance value RS of each phase of the stator winding 4 calculated in the stationary positioning period is used. As shown in FIG. 6, taking the U phase as an example, if the induced voltage is EU, the phase current is iU, the applied voltage is VU, and the inductance is L, EU = VU−RS · iU−LdiU / dt. Similarly, the W phase is EW = VW−RS · iW−LdiW / dt, and the V phase is EV = VV−RS · iV−LdiV / dt. The control circuit 7 detects the current values iU, iW, iV for these three phases based on the voltage from the shunt resistor 6. Thereby, each induced voltage EU, EW, EV can be calculated, that is, the position of the magnet rotor 5 can be estimated.

  At this time, the resistance value RS of the stator winding 4 calculated at the time of positioning is used for estimating the position of the magnet rotor during the start-up operation of the motor. That is, the resistance value RS of the stator winding 4 at the temperature of the stator winding 4 at the start-up operation is used. Therefore, it is possible to accurately calculate the induced voltages EU, EW, EV regardless of the temperature of the stator winding 4 during the starting operation. That is, the position of the magnet rotor 5 can be accurately estimated and activated regardless of the motor temperature during the activation operation. In addition, there is no need to add special parts such as a temperature sensor, wiring, and interface circuit, so that the number of parts and the size of the motor are not increased.

  The control circuit 7 controls the switching element 2 constituting the inverter circuit 10 based on the position estimation, the rotation speed command signal (not shown), etc., and switches the DC voltage from the battery 1 by PWM modulation. Thus, a sinusoidal alternating current is output to the stator winding 4 of the motor 11. The control circuit 7 is connected to the upper arm switching elements U, V, W and the lower arm switching elements X, Y, Z by a connection line 18 via a drive circuit or the like, and controls each switching element. When the switching element 2 is an IGBT or a power MOSFET, the gate voltage is controlled. When the switching element 2 is a power transistor, the base current is controlled.

  In the steady operation shown in FIG. 5, the temperature of the stator winding 4 increases with time. Therefore, it is desirable to change the resistance value RS of the stator winding 4 used for calculating the induced voltages EU, EW, EV. This is called RN (shown in FIG. 7). As the value of RN, for example, a resistance value at a standard temperature during steady operation, a resistance value when the air conditioner compressor is stable at room temperature, a resistance value at the center temperature of the operating temperature range of the stator winding 4, a stator An average value of the resistance value and RS at the highest temperature in the operating temperature range of the winding 4 can be considered.

  In FIG. 1, a battery voltage detector 8 is provided. It can be easily configured by dividing the battery voltage by a resistor. The battery voltage detector 8 is provided to accurately output applied voltages VU, VW, and VV even when the DC voltage of the battery 1 fluctuates. Thereby, the induced voltage can also be accurately calculated. The battery voltage detector 8 may be omitted, and the voltage information of the battery 1 may be obtained by communication from the controller.

  In the above embodiment, the case where the U-phase and V-phase of the stator winding 4 are set to the S-pole and the W-phase is set to the N-pole is shown, and the 4-pole magnet rotor 5 is positioned. The phase of the S pole and the N pole of the stator winding 4 is arbitrary, and is applicable to two poles, six poles, etc., and also when a current is passed through only two phases of the stator winding 4. it can. The shunt resistor 6 may be provided on the plus side of the power supply line. Further, it may be provided on the negative side of the lower arm switching element and the power supply line. The current sensor is not limited to a shunt resistor, and may be any sensor that can detect an instantaneous peak current, such as a current sensor using a Hall element. It may be provided between the inverter circuit 10 and the motor 11 to directly detect the motor current (phase current). The period of start-up operation is not limited to the example shown in FIG.

(Embodiment 2)
FIG. 8 shows a diagram in which the inverter device 22 is attached in close contact with the right side of the electric compressor 40. The compression mechanism 28, the motor 11, and the like are installed in the metal casing 32. The refrigerant is sucked from the suction port 33 and compressed by the compression mechanism 28 (scroll in this example) being driven by the motor 11. The compressed refrigerant cools the motor 11 when passing through the motor 11 and is discharged from the discharge port 34.

  The inverter device 22 uses a case 30 so as to be attached to the electric compressor 40. The inverter circuit unit 10 serving as a heat source is cooled by the low-pressure refrigerant through the low-pressure pipe 38. A terminal 39 connected to the stator winding 4 of the motor 11 inside the electric compressor 40 is connected to the output section of the inverter circuit section 10. The connection line 36 fixed to the inverter device 22 by the holding unit 35 includes a power line to the battery 1 and a signal line to an air conditioner controller (not shown) that transmits a rotation speed signal.

  If a temperature sensor is provided, it is necessary to add terminals to the high-temperature and high-pressure compatible temperature sensor and the electric connection terminal 39 for the high-pressure vessel, which increases the complexity and size. Moreover, since it is a high-pressure type compressor, since the compressed high-temperature / high-pressure refrigerant passes through the motor 11, the temperature of the motor 11 increases greatly. When the motor 11 stops when the temperature rises and starts immediately, the temperature of the stator winding 4 of the motor 11 is high. The electric compressor 40 is increased in size by installing the inverter device 22. Therefore, it is possible to accurately estimate and start the position of the magnet rotor regardless of the motor temperature, and there is no need to add special parts such as temperature sensors, wiring, and interface circuits, increasing the number of parts and increasing the size of the motor, etc. The present inverter device that does not cause the problem is useful.

  In the above embodiment, the compression mechanism of the electric compressor is a scroll. However, the present invention is not limited to this. Moreover, although the compressed refrigerant showed about the high voltage | pressure type which cools a motor, a low voltage | pressure type may be sufficient. In steady operation, the temperature of the stator winding 4 may be estimated from the temperature of the inverter device 22, and the resistance value R of the stator winding 4 may be calculated from the estimated temperature.

(Embodiment 3)
FIG. 9 shows an example in which the inverter device of the present invention is configured integrally with a compressor (Embodiment 2) and applied to an air conditioner and mounted on a vehicle 60. The inverter device-integrated electric compressor 61, the outdoor heat exchanger 63, and the outdoor fan 62 are mounted in an engine room (or motor room) in front of the vehicle 60. On the other hand, an indoor fan 65, an indoor heat exchanger 67, and an air conditioner controller 64 are disposed in the vehicle compartment. Air outside the vehicle is sucked from the air inlet 66 and the air heat-exchanged by the indoor heat exchanger 67 is blown out into the vehicle interior.

  For vehicles, there is a limitation in the mounting space, and it is often mounted in a place where various devices and parts such as a motor room (or engine room) are complicated. In particular, in a hybrid car, both the motor and the engine are mounted, so the periphery of mounting the electric compressor is complicated. Therefore, it is not necessary to add special parts such as a temperature sensor, wiring, and interface circuit, and this inverter device that does not increase the number of parts and increase the size of the motor is very suitable. Moreover, since the ambient temperature rises when mounted near the engine, the present inverter device that is able to accurately estimate and start the position of the magnet rotor regardless of the motor temperature at the start is useful.

  In each of the above embodiments, the DC power source is a battery. However, the present invention is not limited to this, and a DC power source rectified from a commercial AC power source may be used. Although the motor is a sensorless DC brushless motor, it can be applied to a motor that requires positioning, such as a reluctance motor. The present invention is not limited to sinusoidal driving, and can be applied to a driving method that requires detection of a phase current during positioning. It can also be applied to PWM two-phase modulation.

  As described above, the inverter device according to the present invention does not require any special components, and can accurately start and start the position of the magnet rotor regardless of the motor temperature at the time of startup. Therefore, it can be applied to various consumer products and various industrial equipment.

The inverter apparatus which concerns on Embodiment 1 of this invention, and its surrounding electric circuit diagram (A) Positional relationship diagram of stator winding and magnet rotor during positioning, (B) Current diagram of stator winding during positioning (A) 1st explanatory drawing which shows the example of electricity supply in the initial stage of positioning, (B) 2nd explanatory drawing, (C) 3rd explanatory drawing Explanatory drawing showing an example of energization in the stationary positioning period Illustration of phase current of W phase from positioning to operation Explanatory drawing which shows the impedance of the stator winding | coil at the time of start-up operation which concerns on Embodiment 1 of this invention Explanatory drawing showing the impedance of the stator windings during steady operation Sectional drawing of the inverter apparatus integrated electric compressor which concerns on Embodiment 2 of this invention. Schematic diagram of a vehicle equipped with an inverter device according to Embodiment 3 of the present invention Conventional inverter device and peripheral electrical circuit diagram Explanatory drawing showing impedance of the same stator winding Explanatory drawing showing phase characteristics of voltage and current for one phase of the same stator winding

Explanation of symbols

1 Battery 2 Switching Element 3 Diode 4 Stator Winding 5 Magnet Rotor 6 Shunt Resistance (Current Sensor)
7 Control Circuit 8 Battery Voltage Detector 10 Inverter Circuit 11 Sensorless DC Brushless Motor 22 Inverter Device 40 Electric Compressor 60 Vehicle

Claims (5)

An inverter circuit having an upper arm switching element connected to the plus side of the DC power source and a lower arm switching element connected to the minus side, and outputting motor current to the sensorless DC brushless motor by applying PWM modulation to the inverter circuit In the inverter device comprising a control circuit for causing the motor current to be detected, the control circuit outputs a direct current from the inverter circuit to the motor before the motor is operated. A resistance value of the stator winding of the motor is calculated based on a current value detected by the current sensor at the time of positioning of the child, and at least a detected current value of the current sensor and the positioning at the start-up operation of the motor The motor magnets based on the stator winding resistance values calculated at times The inverter device for performing the position estimate for the rotor. The inverter apparatus of Claim 1 which drives the motor of an electric compressor. The inverter device according to claim 2, wherein the electric compressor is a high-pressure type. The inverter apparatus of Claim 2 or Claim 3 mounted in the said electric compressor. The inverter apparatus as described in any one of Claims 1-4 mounted in a vehicle.

Images