JP7570558B2 - Voltage detection device for power converter - Google Patents

Description

The present disclosure relates to a voltage detection device that detects the output voltage of a power converter.

Patent Document 1 discloses a method for detecting the output voltage of a power converter, which integrates the pulsed voltage output by PWM (Pulse Width Modulation) control, integrates the integrated value with a reference voltage, and measures the discharge time. This method makes it possible to accurately detect the small on-voltage of a semiconductor switching element and the minute voltage during a high-speed transient response period.

JP 2006-317425 A

When performing PWM control, in the method of measuring the discharge time by integrating the integrated value of the pulsed output voltage with a reference voltage, if the output voltage is large and the pulse width is close to the PWM period, the discharge time falls into the next PWM period, making it impossible to detect the voltage continuously.

The present disclosure has been made in consideration of the above, and aims to obtain a voltage detection device for a power converter that can accurately and continuously detect minute voltages.

In order to solve the above-mentioned problems and achieve the objective, the voltage detection device for a power converter disclosed herein is a voltage detection device for a power converter that detects the output voltage of a power converter that outputs a voltage to a load of at least one phase, and includes a voltage divider that divides the output voltage and outputs a divided voltage, an integrator that integrates the divided voltage output by the voltage divider and outputs a voltage integral value, a charger/discharger that changes the voltage integral value output by the integrator based on whether a charge/discharge command is on or off, a comparator that compares the voltage integral value output by the integrator with a reference voltage and outputs a determination signal indicative of the comparison result, and a detection controller that turns on the charge/discharge command based on the determination signal output by the comparator.

The voltage detection device for a power converter according to the present disclosure has the effect of being able to accurately and continuously detect minute voltages.

FIG. 1 is a diagram showing a configuration of a system including a voltage detection device for a power converter according to a first embodiment; FIG. 1 is a diagram showing a configuration of a voltage detection device for a power converter according to a first embodiment; FIG. 1 is a diagram showing a configuration of a voltage divider included in a voltage detection device for a power converter according to a first embodiment; FIG. 1 is a diagram showing the configuration of an integrator and a charger/discharger included in a voltage detection device for a power converter according to a first embodiment; FIG. 1 is a diagram showing a configuration of a comparator included in a voltage detection device for a power converter according to a first embodiment; FIG. 13 is a diagram showing operational waveforms of the voltage detection device for the power converter according to the first embodiment for the u-phase component when the output voltage of the power converter is medium. FIG. 13 is a diagram showing operational waveforms of the voltage detection device for the power converter according to the first embodiment for the u-phase component when the output voltage of the power converter is small. FIG. 13 is a diagram showing a configuration of a system including a voltage detection device for a power converter according to a second embodiment; FIG. 13 is a diagram showing a configuration of a voltage detection device for a power converter according to a second embodiment; FIG. 13 is a diagram showing operational waveforms of the voltage detection device for the power converter according to the second embodiment for the u-phase when the output voltage of the power converter is medium. FIG. 13 is a diagram showing a configuration of a system including a voltage detection device for a power converter according to a third embodiment. FIG. 13 is a diagram showing a configuration of a voltage detection device for a power converter according to a third embodiment; FIG. 13 is a diagram showing operational waveforms of the voltage detection device for the power converter according to the third embodiment for the u-phase when the output voltage of the power converter is medium. FIG. 13 is a diagram showing a configuration of a system including a voltage detection device for a power converter according to a fourth embodiment. FIG. 13 is a diagram showing a configuration of a voltage detection device for a power converter according to a fourth embodiment; FIG. 13 is a diagram showing a configuration of a voltage converter included in a voltage detection device for a power converter according to a fourth embodiment; FIG. 13 is a diagram showing a configuration of a system including a voltage detection device for a power converter according to a fifth embodiment. FIG. 13 is a diagram showing a configuration of a voltage detection device for a power converter according to a fifth embodiment; FIG. 1 shows the operation waveforms when the upper semiconductor switching element of the u-phase is turned on from the on state of the lower semiconductor switching element of the u-phase. FIG. 2 shows the operation waveforms when the upper semiconductor switching element of the u-phase is turned on from the on state of the lower semiconductor switching element of the u-phase. FIG. 13 is a diagram showing a configuration of a system including a voltage detection device for a power converter according to a sixth embodiment. FIG. 13 is a diagram showing a configuration of a voltage detection device for a power converter according to a sixth embodiment; FIG. 13 is a diagram showing the configuration of an integrator and a charger/discharger included in a voltage detection device for a power converter according to a sixth embodiment. FIG. 1 is a diagram showing a configuration of a voltage detection device for a power converter according to a first embodiment, in which the function of a detection controller included in the voltage detection device is realized by a dedicated processing circuit. FIG. 1 is a diagram showing a configuration of a voltage detection device for a power converter according to a first embodiment, in which the function of a detection controller included in the voltage detection device is realized by a processor and a storage device.

Below, the voltage detection device for a power converter according to an embodiment is described in detail with reference to the drawings.

Embodiment 1.
FIG. 1 is a diagram showing a configuration of a system including a voltage detection device 3 of a power converter according to a first embodiment. In FIG. 1, the voltage detection device 3 of the power converter is described as a "voltage detection device 3". Hereinafter, the voltage detection device 3 of the power converter may be described as a "voltage detection device 3". The system has a power converter 1, a motor 2, a voltage detection device 3, and a motor controller 4. The voltage detection device 3 is a device that detects the output voltage of the power converter 1 that outputs a voltage to a load of at least one phase. The voltage detection device 3 is connected to the output terminals u, v, and w of the power converter 1 and the negative terminal N on the DC side. The power converter 1 is a device that supplies power to the motor 2, which is a load.

The voltage detection device 3 outputs voltage integral values _vuNi , _vvNi , and _vwNi of the u-phase, v-phase, and w-phase voltages with respect to the negative terminal N, to the motor controller 4. The motor controller 4 calculates a voltage command for operating the motor 2 at a desired torque and speed based on the voltage integral values _vuNi , _vvNi , and _vwNi , and generates gate signals g _up , g _un , g _vp , g _vn , g _wp , and g _wn for generating voltages corresponding to the voltage commands obtained by the calculation, thereby operating the power converter 1.

The power converter 1 has three phases of legs 21 in which two semiconductor switching elements having reverse conduction function are connected in series. Both ends of each leg 21 are connected to a DC power source 22 and a capacitor 23, and the intermediate terminal of each leg 21 is connected to one of the phases of the motor 2, which is the load. For example, the semiconductor switching element having reverse conduction function is composed of an IGBT (Insulated Gate Bipolar Transistor) and an anti-parallel diode. The semiconductor switching element having reverse conduction function may be an element using a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) or an RC (Reverse-Conducting)-IGBT, etc., in which case the anti-parallel diode may be omitted. Note that the power converter 1 only needs to have at least one phase of a leg including two or more semiconductor switching elements having reverse conduction function. In this case, both ends of the leg are connected to the positive and negative terminals of the DC power supply 22, and the intermediate terminal of the leg is connected to a load, and the power converter 1 supplies a rectangular voltage to the load by turning on and off two or more semiconductor switching elements. The power converter 1 is a two-level, three-phase power converter, but the power converter 1 may be a multilevel converter having three or more levels. The power converter 1 and the multilevel converter are also applicable to one-phase, two-phase, and four or more phase loads without any problem. The load is not limited to the motor 2. The load may be an inductive load or a diode rectifier circuit, etc.

2 is a diagram showing a configuration of the voltage detection device 3 of the power converter according to the first embodiment. The voltage detection device 3 has a u-phase voltage detection unit 30A, a v-phase voltage detection unit 30B, and a w-phase voltage detection unit 30C. The u-phase voltage detection unit 30A has a voltage divider 31 that divides the output voltage of the power converter 1 and outputs a voltage-divided voltage v _ain , an integrator 32 that integrates the voltage-divided voltage v _ain output by the voltage divider 31 and outputs a voltage integral value v _aint , and a comparator 33 that compares the voltage integral value v _aint output by the integrator 32 with a reference voltage v _ab and outputs a judgment signal s _comp indicative of the comparison result. The u-phase voltage detection unit 30A further includes a detection controller 34 that turns on a charge/discharge command s _reset based on the judgment signal s _comp output by the comparator 33, and a charger/discharger 35 that changes the voltage integral value v _aint output by the integrator 32 based on the on/off of the charge/discharge command s _reset . The detection controller 34 outputs the voltage integral value v _uNi to the motor controller 4. The charger/discharger 35 changes the voltage integral value v _aint at a predetermined rate of change. The detection controller 34 turns on the charge/discharge command s _reset for a predetermined time.

The configuration of each of the v-phase voltage detection unit 30B and the w-phase voltage detection unit 30C is the same as that of the u-phase voltage detection unit 30A. Therefore, in FIG. 2, the internal configuration of each of the v-phase voltage detection unit 30B and the w-phase voltage detection unit 30C is omitted. In addition, a method may be used in which the voltages of two of the three phases are detected and the voltage of the remaining phase is calculated by utilizing the fact that the sum of the voltages of the three phases is zero.

The operation of the voltage detection device 3 will be described. However, it is assumed that the voltage integral value v _aint output by the integrator 32 is returned to a specified value by the charger/discharger 35. First, the voltage divider 31 converts the u-phase voltage, which is the output voltage of the power converter 1, into an analog input voltage v _ain at a level that can be handled by an electronic circuit. The analog input voltage v _ain is the voltage v _ain after voltage division. The integrator 32 integrates the analog input voltage v _ain to obtain the voltage integral value v _aint . The integration operates in the direction that inverts the input voltage, that is, in the negative direction.

The comparator 33 sets the judgment signal s _comp to true when the voltage integral value v _aint falls below the reference voltage v _ab . When the judgment signal s _comp becomes true, the detection controller 34 turns on the charge/discharge command s _reset for a certain period of time. The detection controller 34 integrates the voltage change amount of the voltage integral value v _aint due to charging/discharging based on the charge/discharge command s _reset , and outputs the detected voltage integrated value. More specifically, the detection controller 34 integrates the voltage change amount of the voltage integral value v _aint associated with the charge/discharge command s _reset being turned on, and outputs the detected voltage integrated value.

While the charge/discharge command s _reset is on, the charger/discharger 35 charges with a constant current based on the voltage integral value v _aint output from the integrator 32. The voltage integral value v _aint is charged with a constant current, i.e., a constant voltage change rate, for a fixed period of time, so that the voltage integral value v _aint is charged by a fixed amount of voltage change each time the charge/discharge command s _reset is turned on, and the voltage integral value v aint returns to a specified value. In other words, when the voltage integral value v _aint obtained by integrating the phase voltage falls below the reference voltage v _ab , a fixed amount of voltage change is integrated into the detected voltage integrated value to detect the voltage. At the same time, the voltage integral value v _aint is returned to its original value by the charger/discharger 35 by the voltage change amount. The magnitude of the voltage change amount is equal to the amount of change from the specified value to the reference voltage v _ab .

3 is a diagram showing the configuration of a voltage divider 31 included in the voltage detection device 3 of the power converter according to the first embodiment. The voltage divider 31 divides the output voltage of the power converter 1 using resistors, and outputs an analog input voltage v _ain . The voltage division ratio is selected so that the output voltage dependent on the DC voltage of the power converter 1 and the load voltage are converted to a voltage level that can be handled by an electronic circuit, in this case, a voltage within the range of ±5V. The operating voltage of the analog electronic circuit may be designed to be ±15V or the like. The voltage divider 31 may not be a circuit that divides voltage using resistors, but may be a component that utilizes an isolated voltage converter.

4 is a diagram showing the configuration of the integrator 32 and the charger/discharger 35 included in the voltage detection device 3 of the power converter according to the first embodiment. The integrator 32 integrates the analog input voltage v _ain by an integrating circuit using an operational amplifier, and outputs a voltage integral value v _aint . The charger/discharger 35 turns on the switch during a period in which the charge/discharge command s _reset is on, and charges the capacitor of the integrator 32 with a constant current. Even during this charging, the integrator 32 can continue integrating the analog input voltage v _ain .

5 is a diagram showing the configuration of the comparator 33 included in the voltage detection device 3 of the power converter according to embodiment 1. When the voltage integral value _{v_aint} falls below the reference voltage _{v_ab} , the determination signal _{s_comp} becomes true.

The motor controller 4 calculates the flux linkage from the voltage integral value v _aint . The equation for calculating the flux linkage is the following equation (1).

Ψ _ph is the flux linkage, v _ph is the phase voltage value, R _s is the winding resistance value, and i _ph is the phase current value. In equation (1), at medium to high rotation speeds, the second term is small compared to the first term and may be ignored. In equation (1), the flux linkage can be calculated by using the voltage integral value v _aint as the integral value of the first term. The motor controller 4 calculates a voltage command to realize the generation of flux linkage that operates the motor 2 at a desired torque and speed, and generates gate signals g _up , g _un , g _vp , g _vn , g _wp , and g _wn .

6 is a diagram showing the operation waveforms of the voltage detection device 3 of the power converter according to the first embodiment for the u-phase when the output voltage of the power converter 1 is medium. The power converter 1 performs PWM control with a PWM period of 1 ms to output a rectangular wave voltage. The post-division voltage V _ain obtained by dividing the u-phase _voltage is the analog input voltage V _ain .

At the initial time 0 ms, the voltage integral value v _aint is a specified value of 4×10 ⁻⁵ V. When the u-phase voltage is output, the analog input voltage v _ain is integrated, and the voltage integral value v _aint decreases. When the voltage integral value v _aint falls below the reference voltage v _ab of 1×10 ⁻⁵ V, the voltage detection device 3 sets the judgment signal s _comp to true. When the judgment signal s _comp becomes true, the charge/discharge command s _reset is turned on for a fixed period, here 1 μs. The voltage detection device 3 integrates the voltage change amount of the voltage integral value v _aint due to charging and discharging, 3×10 ⁻⁵ V, and outputs the detected voltage integration value v _uNi . As for charging and discharging, charging is performed at a fixed current for a very short time, here 1 μs. The amount of voltage change due to charging is designed to be 3×10 ⁻⁵ V, and after charging, the voltage integral value v _aint returns to the specified value of 4×10 ⁻⁵ V. Even during charging, the integrator 32 can continue integrating the u-phase voltage to be detected, so the voltage detection device 3 can continuously detect the voltage.

In this way, the u-phase voltage is integrated in the reverse direction, and when the voltage integral falls below the reference voltage, the voltage integral is charged, and the amount of voltage change due to charging and discharging is integrated into the detected voltage integral to detect the integrated value of the u-phase voltage. The voltage detection device 3 according to embodiment 1 does not need to integrate the voltage for one or more PWM periods, convert the integral into time based on a predetermined voltage, and measure the time to integrate in the reverse direction at the predetermined voltage, so it can detect the voltage continuously without interruption.

7 is a diagram showing the operation waveforms of the voltage detection device 3 of the power converter according to the first embodiment for the u-phase when the output voltage of the power converter 1 is small. The power converter 1 performs PWM modulation with a PWM period of 1 ms to output a rectangular wave voltage. Since the output voltage is small, the width of the analog input voltage v _ain of the rectangular wave voltage is small, so the voltage change amount is not integrated even once into the detection voltage integrated value v _uNi in one PWM period.

However, since the integrator 32 continues to integrate the minute output voltage as the voltage integral value v _aint , the voltage change amount is integrated at the timing of t=1.5 ms in the next period and detected as the output voltage. Similarly, in the third period, that is, in the period from t=2 ms to 3 ms, the voltage change amount is not integrated, but the minute output voltage continues to be integrated, and in the next fourth period, that is, in the period from t=3 ms to 4 ms, the voltage change amount is integrated and detected as the output voltage. Here, a thin rectangular wave voltage has been used to explain the case where the output voltage is small, but the voltage detection device 3 can also detect the small on-voltage of the semiconductor switching element and the minute voltage during a high-speed, short transient response period.

In this way, even minute voltages that cannot be sensed in only one PWM cycle can be detected by continuing to integrate the output voltage. Even when detecting minute voltages using AD (Analog-to-Digital) conversion, they cannot be detected if the voltage is below the resolution. The voltage detection device 3 according to embodiment 1 has an integrator 32 and is therefore capable of detecting minute output voltages.

In the above operation explanation, it was explained that the detected voltage integrated value is detected based on the analog input voltage, but the detected value needs to be corrected by the voltage division ratio from the output voltage of the power converter 1 to the analog input voltage. Here, it was explained that the voltage ratio from the analog input voltage to the detected voltage integrated value is 1:1, but it goes without saying that if the voltage is converted and operated in the circuit from the analog input voltage to the integrator 32, or from the integrator 32 to the detection controller 34, the detected value can be corrected by the voltage conversion ratio.

As described above, by using the voltage detection device 3 of the power converter according to the first embodiment, it is possible to accurately detect the small on-voltage of the semiconductor switching element and the minute voltage during the high-speed transient response period, and it is also possible to obtain a remarkable effect not seen in the past, that is, to detect the voltage continuously without interruption. That is, the voltage detection device 3 can accurately and continuously detect the minute voltage. More specifically, the charger/discharger 35 changes the voltage integral value v _aint at a predetermined rate of change, and the detection controller 34 turns on the charge/discharge command s _reset for a predetermined time. Therefore, the voltage detection device 3 can continue the integral operation of the output voltage even while changing the voltage integral value, and can accurately detect the voltage.

Embodiment 2.
Fig. 8 is a diagram showing the configuration of a system including a voltage detection device 5 of a power converter according to embodiment 2. In Fig. 8, the voltage detection device 5 of the power converter is described as a "voltage detection device 5". Hereinafter, the voltage detection device 5 of the power converter may be described as a "voltage detection device 5". The second embodiment differs from the first embodiment in that the voltage detection device 3 is replaced with the voltage detection device 5 and that the motor controller 4 is replaced with a motor controller 6.

FIG. 9 is a diagram showing the configuration of the voltage detection device 5 of the power converter according to the second embodiment. The voltage detection device 5 has a u-phase voltage detection unit 30D, a v-phase voltage detection unit 30E, and a w-phase voltage detection unit 30F. The configurations of the v-phase voltage detection unit 30E and the w-phase voltage detection unit 30F are the same as those of the u-phase voltage detection unit 30D. Therefore, in FIG. 9, the internal configurations of the v-phase voltage detection unit 30E and the w-phase voltage detection unit 30F are omitted. The voltage detection device 5 differs from the voltage detection device 3 according to the first embodiment in that the detection controller 34 is replaced with a detection controller 51. The detection controller 34 of the first embodiment continuously accumulates the detection voltage integrated value from the time of startup, while the detection controller 51 outputs the detection voltage integrated values v _uNiT , v _vNiT , and v _wNiT from a certain point in time to a point in time one detection cycle before the point in time. The detection cycle is equal to the PWM cycle. In other words, the detection controller 51 outputs an integrated value of the detected voltage for a predetermined period.

The motor controller 6 calculates the flux linkage from the voltage integral value v _aint . When the calculation formula (1) is discretized, the following formula (2) is obtained.

In equation (2), the superscript -1 indicates the value of one control calculation cycle before, and _Tsmp is the control calculation cycle, which is the same as the PWM cycle. In equation (2), at high rotation speeds, the second term is smaller than the first term and may be ignored. In equation (2), the flux linkage can be calculated by using the integrated value of the detected voltage for one control calculation cycle, obtained by the voltage detection device 5, here for one PWM cycle, as the integral value of the first term.

FIG. 10 is a diagram showing the operation waveforms of the voltage detection device 5 of the power converter according to the second embodiment for the u-phase when the output voltage of the power converter 1 is medium. The power converter 1 performs PWM modulation with a PWM period of 1 ms to output a rectangular wave voltage. The detected voltage integrated value is integrated as in the first embodiment, but in the second embodiment, the integrated voltage v _uNiT up to one detection period before, here one PWM period before, is calculated. At the timing of t=1 ms, the average analog input voltage v _ain in the previous PWM period is 0.6 V. The detected voltage integrated value is 6×10 ⁻⁴ V=0.6 V×1 ms, and the detected voltage integrated value for one PWM period is detected. Similarly, at the timing of t=2 ms, the average analog input voltage v _ain in the previous PWM period is 0.4 V. The detected voltage integrated value is 4×10 ⁻⁴ V=0.4 V×1 ms, and the detected voltage integrated value for one PWM cycle is detected. Note that, for ease of understanding, the explanation has been given at a point in time that is an integer multiple of the PWM cycle, but the voltage detection device 5 can detect the voltage integrated value up to the point in time of one detection cycle prior at any point in time.

As described above, by using the voltage detection device 5 of the power converter according to embodiment 2, in addition to the effect obtained in embodiment 1, a remarkable effect not seen in the past can be obtained, that is, even when the voltage accumulation value of a past control calculation period is required for controlling a load using the power converter 1, the load can be controlled with high precision by detecting and using the voltage accumulation value.

Embodiment 3.
Fig. 11 is a diagram showing the configuration of a system including a voltage detection device 7 of a power converter according to embodiment 3. In Fig. 11, the voltage detection device 7 of the power converter is described as a "voltage detection device 7". Hereinafter, the voltage detection device 7 of the power converter may be described as a "voltage detection device 7". The third embodiment differs from the first embodiment in that the voltage detection device 3 is replaced with the voltage detection device 7 and that the motor controller 4 is replaced with a motor controller 8.

FIG. 12 is a diagram showing the configuration of a voltage detection device 7 of a power converter according to a third embodiment. The voltage detection device 7 has a u-phase voltage detection unit 30G, a v-phase voltage detection unit 30H, and a w-phase voltage detection unit 30J. The configurations of the v-phase voltage detection unit 30H and the w-phase voltage detection unit 30J are the same as those of the u-phase voltage detection unit 30G. Therefore, in FIG. 12, the internal configurations of the v-phase voltage detection unit 30H and the w-phase voltage detection unit 30J are omitted. The voltage detection device 7 differs from the voltage detection device 3 according to the first embodiment in that the detection controller 34 is replaced with a detection controller 71. The detection controller 34 of the first embodiment continuously accumulates the detection voltage integrated value from the time of startup, but the detection controller 71 outputs the average detection voltage values v _uNT , v _vNT , and v _wNT from a certain point in time to a point in time one detection cycle before the point in time. That is, the detection controller 71 outputs a detection voltage value obtained by dividing the integrated value of the detection voltage for a predetermined period by the period. The detection period is equal to the PWM period.

The motor controller 8 calculates the flux linkage from the detected voltage value based on equation (2). In equation (2), at high rotation speeds, the second term is small compared to the first term and may be ignored. In equation (2), the flux linkage can be calculated by using the average detected voltage value in one control calculation period, here one PWM period, obtained by the voltage detection device 7 as the phase voltage v _ph ^-1 in the first term.

FIG. 13 is a diagram showing the operation waveforms of the voltage detection device 7 of the power converter according to the third embodiment for the u-phase when the output voltage of the power converter 1 is medium. The power converter 1 performs PWM modulation with a PWM period of 1 ms to output a rectangular wave voltage. The detected voltage integrated value is integrated in the same manner as in the first embodiment, but in the third embodiment, the average detected voltage value v _uNT in one past detection period, here, in one past PWM period, is calculated. At the timing of t=1 ms, the average analog input voltage v _ain in one immediately preceding PWM period is 0.6 V. The detected voltage value is 0.6 V, and the average detected voltage value in one PWM period is detected. Similarly, at the timing of t=2 ms, the average analog input voltage v _ain in one immediately preceding PWM period is 0.4 V. The detected voltage integrated value is 0.4 V, and the average detected voltage value in one PWM period is detected. In order to make the explanation easier to understand, the explanation has been given with respect to points at which the PWM period is an integer multiple; however, at any point in time, the voltage detection device 7 can detect the average detection voltage value up to the point in the previous detection period.

From the above, by using the voltage detection device 7 of the power converter of embodiment 3, in addition to the effect obtained in embodiment 1, a remarkable effect not seen in the past can be obtained, in that even when a detected voltage value from a past control calculation period is required for controlling a load using the power converter 1, the detected voltage value can be observed and used to control the load with high precision.

Embodiment 4.
Fig. 14 is a diagram showing the configuration of a system including a voltage detection device 9 of a power converter according to embodiment 4. In Fig. 14, the voltage detection device 9 of the power converter is described as "voltage detection device 9". Hereinafter, the voltage detection device 9 of the power converter may be described as "voltage detection device 9". The fourth embodiment differs from the first embodiment in that the voltage detection device 3 is replaced with the voltage detection device 9 and that the motor controller 4 is replaced with a motor controller 10. The voltage detection device 9 outputs voltage integral values v _uvi , v _vwi , and v _wui of the line voltages on the output side of the power converter 1.

FIG. 15 is a diagram showing the configuration of a voltage detection device 9 of a power converter according to a fourth embodiment. The voltage detection device 9 has a u-phase voltage detection unit 30K, a v-phase voltage detection unit 30L, and a w-phase voltage detection unit 30M. The configurations of the v-phase voltage detection unit 30L and the w-phase voltage detection unit 30M are the same as the configuration of the u-phase voltage detection unit 30K. Therefore, in FIG. 15, the internal configurations of the v-phase voltage detection unit 30L and the w-phase voltage detection unit 30M are omitted. The voltage detection device 9 differs from the voltage detection device 3 according to the first embodiment in that the voltage detection device 9 detects a line voltage. When detecting a line voltage, the analog input voltage v _ain changes between the positive and negative sides, so that the design of an analog circuit following the component that detects the line voltage becomes complicated. Therefore, a voltage converter 91 is added.

FIG. 16 is a diagram showing the configuration of a voltage converter 91 included in the voltage detection device 9 of the power converter according to the fourth embodiment. The voltage converter 91 includes an inverting amplifier circuit 92 and a differential amplifier circuit 93. The analog input voltage v _ain is a voltage that changes between the positive and negative sides. The inverting amplifier circuit 92 in the front stage of the voltage converter 91 determines the sign of the analog input voltage v _ain , and the inverting differential amplifier circuit 93 in the rear stage of the voltage converter 91 converts the analog input voltage v _ain into a signal centered on the offset v _an . Here, it is assumed that the electronic circuit is designed for ±5V, and the offset v _an is set to 2.5V. Since the inverting differential amplifier circuit 93 is used to invert the direction of change of the analog input voltage v _ain , the inverting amplifier circuit 92 in the front stage returns the direction of change to the original direction. The analog input voltage v _ain that changes between the positive and negative sides becomes a signal that changes only on the positive side centered on the offset v _an =2.5V by the voltage converter 91.

The motor controller 10 calculates the flux linkage from the voltage integral value v _aint based on the formula (1). However, the motor controller 10 converts the voltage integral value v _aint of the line voltage into the voltage integral value of the phase voltage, and calculates the flux linkage by substituting the converted voltage integral value into the formula (1). The conversion from the line voltage to the phase voltage can be performed by using the following formulas (3), (4), and (5).

From the above, when using the voltage detection device 9 of embodiment 4, even when it is desired to detect the output voltage of the power converter 1 or the line voltage of the load, in addition to being able to accurately detect the small on-voltage of the semiconductor switching element and the minute voltage during a fast transient response period, as in embodiment 1, a remarkable effect not seen in the past can be obtained, namely, being able to detect voltage continuously without interruption.

Embodiment 5.
Fig. 17 is a diagram showing the configuration of a system including a voltage detection device 11 of a power converter according to embodiment 5. In Fig. 17, the voltage detection device 11 of the power converter is described as "voltage detection device 11". Hereinafter, the voltage detection device 11 of the power converter may be described as "voltage detection device 11". The fifth embodiment differs from the first embodiment in that the voltage detection device 3 is replaced with the voltage detection device 11 and that the motor controller 4 is replaced with a motor controller 12.

FIG. 18 is a diagram showing the configuration of a voltage detection device 11 of a power converter according to a fifth embodiment. The voltage detection device 11 differs from the voltage detection device 3 according to the first embodiment in that the voltage detection device 11 includes a current detector 1101. The current detector 1101 detects a current flowing from the power converter 1 to a load. More specifically, the current detector 1101 detects three-phase currents _iu , _iv , and _iw . The current detector 1101 may detect currents of two of the three phases, rather than detecting three-phase currents, and may calculate the current of the remaining phase by utilizing the fact that the sum of the currents of the three phases is zero. The current detector 1101 is connected to an end u1 on the u-phase power converter 1 side, an end v1 on the v-phase power converter 1 side, an end w1 on the w-phase power converter 1 side, an end u2 on the u-phase load side, an end v2 on the v-phase load side, and an end w2 on the w-phase load side.

The voltage detection device 11 has a current detector 1101, so in addition to being able to continuously detect minute voltages like the voltage detection device 3 according to embodiment 1, it can also measure voltages that depend on current, that is, the relationship between voltage and current. For example, the on-voltage of the semiconductor switching element of the power converter 1 changes depending on the current, so the voltage detection device 11 can measure voltages that depend on the current.

It will be explained that the voltage during the on and off transient response of the semiconductor switching element changes depending on the phase current. First, when commutation is performed between the upper semiconductor switching element and the lower semiconductor switching element, a dead time is inserted to turn off both semiconductor switching elements in order to prevent both semiconductor switching elements from being simultaneously turned on and short-circuited. FIG. 19 is a first diagram showing the operation waveforms when the upper semiconductor switching element of the u phase is turned on from the state in which the lower semiconductor switching element of the u phase is turned on. FIG. 20 is a second diagram showing the operation waveforms when the upper semiconductor switching element of the u phase is turned on from the state in which the lower semiconductor switching element of the u phase is turned on. FIG. 19 shows the operation waveforms when the phase current i _u is small, and FIG. 20 shows the operation waveforms when the phase current i _u is large. The period td during which an off signal is sent to both semiconductor switching elements is the dead time.

In the dead time period td, the polarity of the phase voltage changes depending on the direction of the current. In Figs. 19 and 20, when the phase current _iu flows from the load to the power converter, the current flows through the positive anti-parallel diode while both semiconductor switching elements are off, and the phase voltage _vuN becomes positive. The magnitude of the phase voltage _vuN during this period changes depending on the magnitude of the current. The operation waveform in Fig. 19 shows that when the phase current _iu is small, it takes time to charge and discharge the parasitic capacitance of the semiconductor switching element, so the rise of the phase voltage _vuN is gradual. The operation waveform in Fig. 20 shows that when the phase current _iu is large, charging and discharging are fast and the rise of the phase voltage _vuN becomes steep. The phase voltage _vuN in Fig. 20 is larger than that in Fig. 19. The voltage detection device 11 according to the fifth embodiment can measure the phase voltage _vuN that depends on the current during such a transient response period of the on and off of the semiconductor switching element.

The motor controller 12 calculates the flux linkage from the voltage integral value v _aint in the same manner as in the first embodiment. However, the motor controller 12 does not ignore the product of the winding resistance and the phase current in the second term of the equation (1) and performs the calculation using the detected phase current. The motor controller 12 then calculates a voltage command so as to generate a flux linkage that operates the motor 2 at a desired torque and speed, and generates gate signals g _up , g _un , g _vp , g _vn , g _wp , and g _wn .

The motor controller 12 can accurately measure and use voltages that depend on current, such as the on-voltage of the semiconductor switching element and the voltage during the on and off transient response of the semiconductor switching element. Therefore, the motor controller 12 can accurately compensate for these voltages and control the load with high precision. In addition, the motor controller 12 can accurately calculate, for example, the winding resistance value Rs using the accurate measured voltage and current. Therefore, the motor controller 12 can calculate the flux linkage using the accurate winding resistance value Rs in, for example, equation (1).

The winding resistance value Rs changes depending on the temperature T and is expressed by the following equation (6).

In equation (6), _R is the resistance of the winding at the reference temperature, α is the temperature coefficient, and _T is the reference temperature. By estimating the temperature of the motor 2, which is the load, from the change in the winding resistance R, the temperature of the motor 2 can be appropriately maintained and parameters dependent on temperature can be corrected, thereby enabling high-performance and high-precision control of the load.

As described above, by using the voltage detection device 11 according to embodiment 5, in addition to the effects obtained in embodiment 1, it is possible to accurately compensate for the on-voltage of the semiconductor switching element, which varies depending on the current. Also, it is possible to control the load with high precision by calculating the winding resistance value of the motor 2, which is the load, and accurately compensating for the voltage error that occurs due to the dead time required when operating the semiconductor switching element. Furthermore, it is possible to obtain a remarkable effect not seen in the past, such as being able to estimate the temperature from the change in the winding resistance value and control the load with high functionality.

Embodiment 6.
Fig. 21 is a diagram showing the configuration of a system including a voltage detection device 13 of a power converter according to embodiment 6. In Fig. 21, the voltage detection device 13 of the power converter is written as "voltage detection device 13". Hereinafter, the voltage detection device 13 of the power converter may be written as "voltage detection device 13". The sixth embodiment differs from the first embodiment in that the voltage detection device 3 is replaced with the voltage detection device 13.

Figure 22 is a diagram showing the configuration of the voltage detection device 13 of the power converter according to embodiment 6. The voltage detection device 13 has a u-phase voltage detection unit 30P, a v-phase voltage detection unit 30Q, and a w-phase voltage detection unit 30R. The configurations of the v-phase voltage detection unit 30Q and the w-phase voltage detection unit 30R are the same as the configuration of the u-phase voltage detection unit 30P. Therefore, in Figure 22, the internal configurations of the v-phase voltage detection unit 30Q and the w-phase voltage detection unit 30R are omitted. The voltage detection device 13 differs from the voltage detection device 3 according to embodiment 1 in that the detection controller 34 is replaced with a detection controller 131, and the charger/discharger 35 is replaced with a charger/discharger 132.

The operation of the voltage detection device 13 will be described. However, it is assumed that the voltage integral value v _aint output by the integrator 32 is returned to a specified value by the charger/discharger 132. The voltage divider 31 converts the u-phase voltage, which is the output voltage of the power converter 1, into an analog input voltage v _ain at a level that can be handled by an electronic circuit. The integrator 32 integrates the analog input voltage v _ain to obtain the voltage integral value v _aint . The integration operates in the inverted direction of the input voltage, that is, in the negative direction. The comparator 33 sets the judgment signal s _comp to true when the voltage integral value v _aint falls below the reference voltage v _ab .

When the determination signal _{s_comp} becomes true, the detection controller 131 turns on the charge/discharge command _{s_reset} . The detection controller 131 integrates the amount of voltage change in the voltage integral value _{v_aint} due to charging/discharging based on the charge/discharge command _{s_reset} , and outputs a detected voltage integration value. When the charge/discharge command _{s_reset} becomes on, the charge/discharger 132 charges the voltage integral value _{v_aint} output by the integrator 32 to a specified value, here. When charging is completed, the determination signal _{s_comp} becomes false, the charge/discharge command _{s_reset} becomes off, and the integrator 32 resumes integrating the analog input voltage _{v_ain} .

Since the voltage integral value v _aint is charged from the reference voltage to the specified value, the voltage integral value v _aint is charged by a certain voltage change amount and returns to the specified value every time the charge/discharge command s _reset is turned on. In other words, when the phase voltage is integrated and the voltage integral value v _aint falls below the reference voltage, the voltage is detected by integrating the certain voltage change amount into the detected voltage integrated value. At the same time, the voltage integral value v _aint is returned to the original value by the voltage change amount by the charge/discharger 132. The magnitude of the voltage change amount is equal to the change amount from the specified value to the reference voltage.

FIG. 23 is a diagram showing the configuration of the integrator 32 and the charger/discharger 132 included in the voltage detection device 13 of the power converter according to the sixth embodiment. When the charge/discharge command _{s_reset} is turned on, the charger/discharger 132 turns on the switch to charge the capacitor of the integrator 32 to a specified value _{v_sd} . The specified value is 4×10 ⁻⁵ V, which is the same as the specified value in the first embodiment. In the sixth embodiment, since it is not necessary to charge with a constant current as the charger/discharger 35 in the first embodiment does, the charger/discharger 132 can be realized with a circuit having a simpler configuration. However, unlike the first embodiment, the integrator 32 cannot change the voltage integral value by integrating the analog input voltage during the charging period. However, since the charging/discharging period is instantaneous, there is almost no effect on the detection of the voltage.

From the above, by using the voltage detection device 13 of the power converter of embodiment 6, a remarkable effect not seen in the past can be obtained, in that the effect obtained in embodiment 1 can be realized with a circuit of a simpler configuration.

24 is a diagram showing the configuration of the voltage detection device 3 in the power converter according to the first embodiment when the function of the detection controller 34 of the voltage detection device 3 is realized by a dedicated processing circuit 141. In other words, the function of the detection controller 34 may be realized by the dedicated processing circuit 141.

The dedicated processing circuit 141 is dedicated hardware. The dedicated processing circuit 141 is, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a combination of these. Each of the multiple functions of the detection controller 34 may be realized by a dedicated processing circuit that is different from the dedicated processing circuit that realizes the other functions.

25 is a diagram showing a configuration of the voltage detection device 3 when the function of the detection controller 34 of the voltage detection device 3 of the power converter according to embodiment 1 is realized by the processor 142 and the memory device 143. In other words, the function of the detection controller 34 may be realized by the processor 142 and the memory device 143.

When the function of the detection controller 34 is realized by the processor 142 and the storage device 143, the function is realized by the processor 142 and software, firmware, or a combination of software and firmware. The software or firmware is written as a program and stored in the storage device 143. The processor 142 realizes the function of the detection controller 34 by reading and executing the program stored in the storage device 143. The program stored in the storage device 143 can also be said to cause the computer to execute the procedure or method executed by the detection controller 34.

The processor 142 is a CPU (Central Processing Unit), a processing system, an arithmetic system, a microprocessor, or a DSP (Digital Signal Processor).

The storage device 143 may be, for example, a non-volatile or volatile semiconductor memory such as a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an EPROM (Erasable Programmable Read Only Memory), an EEPROM (registered trademark) (Electrically Erasable Programmable Read-Only Memory), a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, or a DVD (Digital Versatile Disk).

Some of the functions of the detection controller 34 may be implemented in software or firmware, and the remaining functions may be implemented in dedicated hardware. In this manner, the functions of the detection controller 34 may be implemented in hardware, software, firmware, or a combination thereof.

The functions of the detection controller 51 of the voltage detection device 5 according to the second embodiment, the detection controller 71 of the voltage detection device 7 according to the third embodiment, and the detection controller 131 of the voltage detection device 13 according to the sixth embodiment may be realized by a dedicated processing circuit. The dedicated processing circuit is a dedicated processing circuit equivalent to the dedicated processing circuit 141. The functions of the detection controller 51 of the voltage detection device 5 according to the second embodiment, the detection controller 71 of the voltage detection device 7 according to the third embodiment, and the detection controller 131 of the voltage detection device 13 according to the sixth embodiment may be realized by a processor and a storage device. The processor is a processor equivalent to the processor 142, and the storage device is a storage device equivalent to the storage device 143.

The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, or the embodiments may be combined with each other, or parts of the configurations may be omitted or modified without departing from the spirit of the invention.

1 Power converter, 2 Motor, 3, 5, 7, 9, 11, 13 Power converter voltage detection device, 4, 6, 8, 10, 12 Motor controller, 21 Leg, 22 DC power supply, 23 Capacitor, 30A, 30D, 30G, 30K, 30P u-phase voltage detection unit, 30B, 30E, 30H, 30L, 30Q v-phase voltage detection unit, 30C, 30F, 30J, 30M, 30R w-phase voltage detection unit, 31 Voltage divider, 32 Integrator, 33 Comparator, 34, 51, 71 Detection controller, 35 Charger/discharger, 91 Voltage converter, 92 Inverting amplifier circuit, 93 Differential amplifier circuit, 131 Detection controller, 132 Charger/discharger, 141 Dedicated processing circuit, 142 Processor, 143 Storage device, 1101 Current detector.

Claims (7)

A voltage detection device for a power converter that detects an output voltage of a power converter that outputs a voltage to a load of at least one phase, comprising:
a voltage divider that divides the output voltage and outputs a divided voltage;
an integrator that integrates the divided voltage output by the voltage divider to output a voltage integral value;
a charger/discharger that changes the voltage integral value output by the integrator based on whether a charge/discharge command is on or off;
a comparator that compares the voltage integral value output by the integrator with a reference voltage and outputs a determination signal indicative of a comparison result;
a detection controller that turns on the charge/discharge command based on the determination signal output by the comparator. The charger/discharger changes the voltage integral value at a predetermined rate of change,
2. The voltage detection device for a power converter according to claim 1, wherein the detection controller turns on the charge/discharge command for a predetermined period of time. 3. The voltage detection device for a power converter according to claim 1, wherein the detection controller integrates a voltage change amount of the voltage integral value associated with turning on of the charge/discharge command, and outputs an integrated detected voltage value. 4. The voltage detection device for a power converter according to claim 3, wherein the detection controller outputs the integrated value of the detected voltage for a predetermined period. 5. The voltage detection device for a power converter according to claim 3, wherein the detection controller outputs a detected voltage value obtained by dividing the detected voltage integrated value for a predetermined period by the period. 6. The voltage detection device for a power converter according to claim 1, further comprising: a current detector for detecting a current flowing from the power converter to the load. the power converter has at least one phase of legs each including two or more semiconductor switching elements each having a reverse conduction function;
Both ends of the leg are connected to positive and negative terminals of a DC power supply,
The intermediate terminal of the leg is connected to the load;
7. The voltage detection device for a power converter according to claim 1, wherein the power converter supplies a rectangular voltage to the load by turning on and off the two or more semiconductor switching elements.

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