JP6686472B2 - Power calculator - Google Patents

Description

  The present invention relates to a power conversion device and a power calculation device that calculates a loss in a load that is a driving target thereof.

  In industrial facilities such as factories and various plants, a control system for controlling various operations is often constructed. This type of control system includes a power conversion device such as an inverter, a control device that controls the power conversion device, and a load (for example, a motor) that is a drive target of the power conversion device. In recent years, it has been said that the power consumed by the control system accounts for 50% or more of the total power consumed in Japan due to the widespread use of devices such as pumps and blowers having a motor as a drive source. There is.

  Background of the Invention Due to an increase in global energy consumption, there is an increasing demand for high efficiency of various devices that constitute a control system. The International Electrotechnical Commission (IEC) is in the process of issuing regulations regarding test conditions for calculating efficiency classes of inverters and motors, and regulations regarding efficiency classes of inverters and motors calculated using those test conditions. Companies are required to adopt inverters and motors of efficiency class in accordance with IEC regulations, and to construct an energy management system for managing the power consumption of the entire control system including these.

  As an example of this type of energy management system, a device that consumes a large amount of power, for example, an input unit of an inverter main circuit is provided with a sensor that detects the input current, and the power consumption is calculated based on the detection result of the sensor. System. More specifically, the detection result of the sensor is transmitted to the upper management system via the network, and the input power of the inverter main circuit calculated based on the detection result is managed as power consumption.

  However, for a company that builds an energy management system, it is necessary to bear the cost of installing a new sensor, and even if such a sensor is installed, the productivity of a factory or the like is improved. Nothing. Therefore, it is desired to measure the input power of the inverter main circuit without providing new equipment such as the sensor.

  As a technique for measuring the input power of the inverter main circuit without providing new equipment, a motor control sensor for detecting the output current of the inverter main circuit, that is, a technique using an existing sensor is considered. An example thereof is the technique disclosed in Patent Document 1. The inverter device disclosed in Patent Document 1 calculates the output power of the inverter main circuit based on the detection result of the current detection circuit (sensor) that detects the output current of the inverter main circuit, and the calculation result and the internal part of the inverter device. The instantaneous value of the input power of the inverter main circuit is calculated by adding the loss in the circuit (rectifier circuit, smoothing capacitor circuit, inverter main circuit, etc.).

JP2012-39783A

  The IEC regulations stipulate various various standards such as "annual energy-saving effect according to operating conditions" and "power consumption per day in industrial facilities", and companies are required to comply with the above standards. Has been requested. For example, when the target of the regulation is the inverter main circuit, the loss according to the operating condition for one year (when the target driven by the inverter is a motor, the operating speed and output torque of the motor) is calculated, and the loss is calculated. By comparing the loss value with the loss value required by the standard, it is possible to verify whether or not the former standard is complied with. In addition, for example, by calculating the power consumption (input power) of the inverter main circuit per day and comparing the power consumption with the power consumption required by the standard, it is possible to determine whether or not the latter standard is complied with. Can be verified. If the output power of the inverter main circuit is known in advance, the loss in the inverter main circuit is calculated, and the input power (power consumption) calculated based on the loss and the output power is the power consumption required by the standard. May be compared with. That is, in order to comply with the above standards, it is necessary to verify the power consumption and loss of the inverter main circuit and the like in a predetermined period.

  In the technique disclosed in Patent Document 1, the instantaneous value of the power consumption (input power) of the inverter main circuit can be calculated in real time, but the power consumption and loss calculated in real time cannot be aggregated over a predetermined period. Such tallying processing must be performed by the host system, and in order to realize it, it is necessary to provide a high-performance CPU capable of withstanding an excessive computational load in the host system, which may increase costs.

  When calculating the power consumption and loss of the entire control system, it is necessary to calculate the loss in the motor as well as the inverter main circuit. Patent Document 1 does not disclose any means for calculating the loss in the motor. Therefore, in order to obtain the power consumption and the loss of the entire control system, it is necessary to separately provide a device for measuring the mechanical output of the motor, which may increase the cost.

  The present invention has been made in view of the above circumstances, and a first object thereof is to provide a technique of calculating a loss in an inverter main circuit in a predetermined period without increasing cost. . A second object of the present invention is to provide a technique for calculating the loss in the motor without increasing the cost.

  In order to achieve the first object, the present invention receives data indicating an input to a motor that is a driving target from an inverter main circuit during operation, and based on the data, an instantaneous value of loss in the inverter main circuit. And a second power calculation means for receiving the calculation result by the first power calculation means and integrating the calculation result over a predetermined integration period. There is provided a power calculation device having: Specific examples of the data indicating the input from the inverter main circuit to the motor to be driven include data indicating the frequency of the AC voltage applied from the inverter main circuit to the motor and the current of the output current from the inverter main circuit to the motor. Data showing a value can be given. The frequency of the AC voltage applied from the inverter main circuit to the motor represents the operating speed of the motor, and the current value of the output current from the inverter main circuit to the motor represents the output torque of the motor. The data indicating the input from the inverter main circuit to the motor to be driven during operation is the data indicating the operating condition of the motor.

  According to the present invention, the first power calculation means executes the process of calculating the instantaneous value of the loss in the inverter main circuit according to the operating condition of the motor, and the calculation result of the first power calculation means is calculated for a predetermined integration period. The second power calculation means executes a process of integrating over a period of time, that is, a process of calculating the loss in the inverter main circuit according to the operating condition of the motor in a predetermined period. In this way, the two power calculation units (two CPUs or CPU cores) execute the respective processes while sharing the respective processes, whereby the load can be distributed. Therefore, it is possible to calculate the loss in the inverter main circuit according to the operating condition of the motor in a predetermined period without using a high-performance CPU that can withstand an excessive calculation load.

  In order to achieve the second object, the present invention provides data indicating an input from an inverter main circuit to a motor to be driven (that is, data indicating a motor operating condition) and data indicating a loss in the motor. The storage means storing a table stored in association with each other and the data indicating the input during operation are received, and the loss in the motor is calculated according to the received data indicating the input based on the stored content of the table. And a power calculation means for outputting the calculation result.

  According to the present invention, it is possible to calculate the loss in the motor according to the operating conditions of the motor without separately providing a device for measuring the mechanical output of the motor.

  According to the present invention, the following effects can be obtained. First, it is possible to calculate the loss in the inverter main circuit in a predetermined period without increasing the cost. Secondly, it is possible to calculate the loss in the motor without increasing the cost.

It is a block diagram which shows the structure of the control apparatus 1 which is one Embodiment of this invention. It is a block diagram which shows the structure of the electric power calculation part 40 in the same embodiment. It is a figure which shows the loss point defined by the standard of IEC. It is a figure which shows the loss value in the inverter main circuit in each loss point. It is a figure which shows the loss value in the inverter main circuit after interpolation processing. It is a figure which shows the loss value in the motor in each loss point.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a block diagram showing a configuration of a control device 1 which is an embodiment of the present invention. The control device 1 controls the inverter main circuit and the motor to be driven, and plays the role of a power calculation device that calculates the amount of power consumption in the inverter main circuit and the motor. The control device 1 is, for example, a processor having a plurality of cores, and by executing software stored in a storage unit (not shown), the voltage command generation unit 10, the PWM signal generation unit 20, and the current detection unit 30. And functions as the power calculation unit 40.

  The voltage command generation unit 10, the PWM signal generation unit 20, and the current detection unit 30 are the same as those in the known control device, and the outline thereof is as follows. Every time the current detection unit 30 acquires data (hereinafter, current detection value) indicating the detection result from a current sensor (not shown) that detects the output current of the inverter main circuit, the voltage detection unit 10 outputs the detection result. And the power calculation unit 40. As will be described later, the detected current value is data representing the output torque of the motor.

  The voltage command generator 10 acquires a frequency command value that specifies the frequency of the output voltage of the inverter main circuit (in other words, the operating speed of the motor) from an external higher-level device (for example, VCU (Vehicle Control Unit)), and Get the current detection value. The voltage command generation unit 10 generates a voltage command based on the frequency command value and the current detection value by a known method such as V / f constant control, and gives the voltage command to the PWM signal generation unit 20. The PWM signal generation unit 20 generates a PWM signal based on the voltage command received from the voltage command generation unit 10 and outputs the PWM signal to the inverter main circuit. The PWM signal turns on / off the switching element of the inverter main circuit, and the AC voltage corresponding to the voltage command is output from the inverter main circuit to the motor.

  The power calculator 40 calculates the instantaneous value of loss in the inverter main circuit and the motor, and the amount of power consumption of the inverter main circuit and the motor in a predetermined period. FIG. 2 is a block diagram showing the configuration of the power calculator 40. As shown in FIG. 2, the configuration of the power calculation unit 40 is roughly divided into an inverter loss calculation unit 410, a motor loss calculation unit 420, and a system loss calculation unit 430.

  The inverter loss calculation unit 410 has an inverter real-time processing unit 411 and an inverter batch processing unit 412. The motor loss calculation unit 420 has a motor real-time processing unit 421 and a motor batch processing unit 422. In the following, when it is not necessary to distinguish between the inverter real-time processing unit 411 and the motor real-time processing unit 421, they are referred to as “real-time processing unit”. Further, when it is not necessary to distinguish between the inverter batch processing unit 412 and the motor batch processing unit 422, they will be referred to as “batch processing unit”.

  The real-time processing unit calculates an instantaneous value of loss in the inverter or the motor according to the operating conditions of the motor. The batch processing unit calculates loss and power consumption in the inverter or the motor in a predetermined period according to the operating conditions of the motor. The real-time processing unit and the batch processing unit are realized by separate CPU cores (or CPUs). That is, in the present embodiment, the load distribution is achieved by sharing the processing of the real-time processing unit and the processing of the batch processing unit by the two CPU cores. The contents of the processing executed by each of the inverter loss calculation unit 410 and the motor loss calculation unit 420 are not particularly changed except for the types of loss and power consumption that are the calculation targets, and the inverter loss calculation unit 410 will be mainly described below. The function of the power calculator 40 will be described below.

  The inverter real-time processing unit 411 acquires the current detection value and the frequency command value. Then, the inverter real-time processing unit 411 calculates the output frequency of the inverter main circuit and the torque of the motor based on each value of the frequency command value and the detected current value each time. Various calculation methods can be considered as a method for calculating the torque of the motor. For example, the inverter real-time processing unit 411 decomposes the detected current value into each current value of a q-axis current iq that is a q-axis component and a d-axis current id that is a d-axis component. Here, since the current value of the d-axis current id of the motor is constant, the torque of the motor is proportional to the current value of the q-axis current iq. Therefore, it becomes possible to calculate the torque of the motor based on the current value of the q-axis current iq. When the inverter real-time processing unit 411 calculates each value of the output frequency of the inverter main circuit and the torque of the motor, the inverter real-time processing unit 411 reads the inverter loss table 411a stored in advance in the storage unit (not shown).

  The inverter loss table 411a is associated with the output frequency of the inverter main circuit and each value of the torque of the motor (that is, data indicating the operating condition of the motor) in the inverter main circuit when the motor is driven under the operating condition. Stores the loss value. Hereinafter, a point on the two-dimensional coordinates that has the output frequency of the inverter main circuit and the torque of the motor as variables is called a "loss point". In IEC, the loss value in the inverter main circuit at a predetermined loss point is standardized, and the manufacturer of the inverter main circuit is requested to disclose the loss value of the inverter main circuit at the loss point. This also applies to motor manufacturers, and disclosure of motor loss values at predetermined loss points is required. FIG. 3 is a diagram showing the loss points defined by the IEC standard. In FIG. 3, the horizontal axis represents the ratio (20 to 90%) of the output frequency (speed) of the inverter main circuit to the maximum output frequency (maximum speed), and the vertical axis represents the ratio of the motor torque to the maximum torque (25 to 100). %) Is shown. As shown in FIG. 3, regarding the seven loss points shown in (1) to (7), disclosure of loss values in the inverter main circuit is requested by the IEC.

  The manufacturer of the inverter main circuit obtains the loss values at the seven loss points shown in FIG. 3 in the format test of the manufactured inverter main circuit, and stores the loss values at each loss point in the inverter loss table 411a. To provide. That is, the inverter loss table 411a stores the loss values of the inverter main circuit at the seven loss points defined by the IEC standard. Various modes are conceivable as to when to store the inverter loss table 411a and the motor loss table 421a (see FIG. 2) in the storage means (not shown). For example, when the manufacturers of the inverter main circuit and the motor are the same, the inverter loss table 411a and the motor loss table 421a may be stored in the storage means (not shown) and shipped from the factory. When the manufacturers of the inverter main circuit and the motor are different, for example, only the inverter loss table 411a is stored in the storage means at the time of factory shipment, and the motor loss table 421a is shipped from the factory by the user via a PC (Personal Computer) or the like. A mode in which the data is stored after the storage means is conceivable.

  FIG. 4 is a diagram showing the loss value of the inverter main circuit at each loss point. In FIG. 4, the axis orthogonal to the two-dimensional plane having the output frequency of the inverter main circuit and the torque of the motor as variables indicates the loss value of the main inverter. In FIG. 4, the loss value calculated by the manufacturer of the inverter main circuit for each of the seven loss points defined by the IEC standard is represented by a bar graph.

  When the inverter real-time processing unit 411 reads out the inverter loss table 411a from the storage means (not shown), the inverter real-time processing unit 411 refers to the stored contents of the inverter loss table 411a to refer to each of the output frequency of the inverter main circuit and the motor torque described above. For the loss point determined from the calculated value, the instantaneous value of the loss in the inverter main circuit is calculated.

  Here, the inverter loss table 411a stores only the loss values in the inverter main circuit at seven loss points. Therefore, when the loss point determined from the output frequency of the inverter main circuit and the calculated value of the motor torque does not match any of the above seven loss points, the inverter real-time processing unit 411 causes the inverter main circuit to output the output of the inverter main circuit. The instantaneous value of the loss at the loss point determined from the calculated values of the frequency and the motor torque is calculated by interpolation. More specifically, the real-time processing unit 411 for the inverter has one or more of the seven loss points located near the loss point determined from the calculated values of the output frequency of the inverter main circuit and the torque of the motor. Interpolation processing is performed according to a known interpolation method such as a linear interpolation method or a weighted average method (bicubic method) from the loss value at the point and the inverter interpolating arithmetic expression 411a (interpolation algorithm) read from the storage means (not shown). Run. FIG. 5 is a diagram showing loss values obtained by interpolation processing for loss points other than the seven loss points shown in FIG. As shown in FIG. 5, by performing the interpolation process, it is possible to calculate the loss value in the inverter main circuit at an arbitrary loss point.

  The inverter real-time processing unit 411 calculates the instantaneous value of the loss in the inverter main circuit with reference to the loss value in the inverter main circuit after the interpolation processing shown in FIG. Then, the inverter real-time processing unit 411 gives the calculation result to the inverter batch processing unit 412 and transmits it to an external device (for example, a display device included in a higher-level management system). As a result, the user can confirm the instantaneous value of the loss in the inverter main circuit output to the external device.

  The inverter batch processing unit 412 acquires the current detection value and the instantaneous value of the loss in the inverter main circuit, and also acquires the operating time information about the inverter main circuit (or motor) from an external host device or the like. Here, the operating time information is information indicating a predetermined period (for example, one day or one year) defined by the IEC standard, and is, for example, measuring means (timer or the like) provided in the VCU or the control device 1. Sent from. The inverter batch processing unit 412 integrates the instantaneous value of the loss in the inverter main circuit with the time indicated by the operating time information as an integration range, and calculates the loss value in the inverter main circuit during a predetermined period (the time indicated by the operating time information). To do.

Next, the inverter batch processing unit 412 calculates the output power amount of the inverter main circuit according to the operating condition of the motor in a predetermined period (time indicated by the operating time information) based on the detected current value. Next, the inverter batch processing unit 412 adds the calculation result and the calculation result of the loss value in the inverter main circuit in a predetermined period, and inputs the amount of input power (consumption of the inverter main circuit according to the operating condition of the motor in the predetermined period (consumption Power amount) is calculated. Then, the inverter batch processing unit 412 gives the input power amount (power consumption amount) to the system loss calculation unit 430 and transmits it to an external device. As a result, the user can confirm the power consumption of the inverter main circuit according to the operating condition of the motor during the predetermined period output to the external device.
The above is the details of the processing executed by the inverter loss calculation unit 410.

  As described above, when calculating the loss in the entire control system, it is necessary to calculate the loss in the motor as well as the inverter main circuit. In order to realize this, in the present embodiment, the following processing is performed by the motor loss calculation unit 420.

  The motor loss calculation unit 420 calculates the instantaneous value of the loss in the motor according to the operating conditions of the motor based on the stored contents of the motor loss table 421a (see FIG. 6) and that the motor loss calculation unit 420 executes the interpolation process. It differs from the inverter loss calculation unit 410 only in that the interpolation calculation formula 421b (interpolation algorithm) is executed. The motor loss table 421a associates the output frequency of the inverter main circuit and each value of the motor torque (that is, data indicating the operating condition of the motor) with the loss of the motor when the motor is driven under the operating condition. The value is stored.

  The motor real-time processing unit 421 provides the motor batch processing unit 422 with an instantaneous value of the loss in the motor according to the operating conditions of the motor, and also transmits it to an external device. The motor batch processing unit 422 provides the system power consumption calculation unit 430 with the amount of power consumption of the motor according to the operating conditions of the motor in a predetermined period, and also transmits it to an external device. As a result, the user can confirm the instantaneous value of the loss in the motor output to the external device and the power consumption of the motor during the predetermined period.

  When the system loss calculation unit 430 acquires each value of the power consumption amount of the inverter main circuit and the power consumption amount of the motor in a predetermined period from the inverter batch processing unit 412 and the motor batch processing unit 422, the system loss calculation unit 430 adds each value, The calculation result is output to an external device. As a result, the user can confirm the total amount of power consumption of the inverter main circuit and the motor during the predetermined period output to the external device according to the operating conditions of the motor.

  As described above, according to the present embodiment, the real-time processing unit executes the process of calculating the instantaneous value of the loss in the inverter main circuit, and the calculation result of the real-time processing unit is integrated over a predetermined integration period, that is, the predetermined period. The batch processing unit executes the process of calculating the loss in the inverter main circuit in. In this way, the real-time processing unit and the batch processing unit execute the respective processes while sharing the respective processes, whereby the load can be distributed. Therefore, it is possible to calculate the loss in the inverter main circuit in a predetermined period without using a high-performance CPU that can withstand an excessive calculation load. Therefore, it is possible to calculate the loss in the inverter main circuit for a predetermined period without increasing the cost.

  Further, according to the present embodiment, the motor loss table is stored in the power calculation unit 40, and the instantaneous value of the loss in the motor is calculated based on this motor loss table. Therefore, it is possible to calculate the instantaneous value of the loss in the motor without separately providing a device for measuring the mechanical output of the motor. Therefore, it is possible to calculate the loss in the motor without increasing the cost.

  Although the respective embodiments of the present invention have been described above, other embodiments can be considered for the present invention. For example,

(1) In the above embodiment, either one of the inverter loss calculation unit 410 and the motor loss calculation unit 420 may be omitted. When leaving the motor loss calculation unit 420, the motor batch processing unit 422 may be omitted. Even in such a mode, it is possible to grasp the instantaneous value of the loss in the motor according to the operating conditions of the motor. According to this aspect, the calculation load of the control device 1 (CPU) can be further reduced.

(2) In the above embodiment, the real-time processing unit and the batch processing unit may be configured by separate CPUs. According to this aspect, the calculation load of the control device 1 can be further reduced.

(3) In the above embodiment, the control device 1 may be provided with a transmission unit for transmitting the calculation results of the respective units of the real-time processing unit, the batch processing unit, and the system loss calculation unit 430 to an external device.

(4) In the above embodiment, the interpolation process may be executed using the loss values at some loss points stored in the inverter loss table 411a. For example, when the load to be driven by the inverter main circuit is a squared reduction torque load such as a fan, among the loss points (1) to (7) shown in FIG. 3, (1), (5) and (7) are included. The interpolation process may be executed by using only the loss point of). Further, when the load is a low torque load such as a conveyor, among the loss points (1) to (7) shown in FIG. (3), only the loss points (1), (2) and (3) are The interpolation process may be executed by using this. Thus, by omitting the interpolation points according to the type of load, the calculation load of the control device 1 can be further reduced.

DESCRIPTION OF SYMBOLS 1 ... Control device, 10 ... Voltage command generation part, 20 ... PWM signal generation part, 30 ... Current detection part, 40 ... Electric power calculation part, 410 ... Inverter loss calculation part, 420 ... Motor loss calculation part, 411 ... Inverter real time Processing unit, 412 ... Inverter batch processing unit, 421 ... Motor real-time processing unit, 422 ... Motor batch processing unit, 430 ... System loss calculation unit.

Claims (3)

A storage unit that stores an inverter loss table that associates a set of information indicating the output frequency from the inverter main circuit to the motor that is the driving target and information indicating the torque of the motor with the loss value of the inverter main circuit,
A frequency command value designating the output frequency during operation and a current detection value indicating the output current of the inverter main circuit are acquired, and the output frequency indicated by the frequency command value and the current detection value are calculated. First power calculation means for calculating an instantaneous value of the loss in the inverter main circuit based on the torque of the motor and the inverter loss table stored in the storage means, and outputting the calculation result;
And a second power calculation means for receiving the calculation result of the first power calculation means and integrating the calculation result over a predetermined integration period. The inverter loss table associates a set of a ratio of an output frequency from the inverter main circuit to a motor which is a driving target thereof with respect to a maximum output frequency and a ratio of a torque of the motor with respect to a maximum torque to a loss value of the inverter main circuit. The power calculation device according to claim 1, wherein The first power calculation means calculates a loss value corresponding to an output frequency from the inverter main circuit to the motor indicated by the frequency command value and a torque of the motor calculated from the detected current value by interpolation calculation. The power calculation device according to claim 1 or 2, wherein

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