TWI390835B - Dead-time compensation apparatus of pwm inverter and method thereof - Google Patents

Description

Pulse wave width modulation dead zone compensation device of frequency converter and method thereof

The invention relates to a pulse width modulation dead zone compensation device and a method thereof for a frequency converter, in particular to a pulse width modulation dead zone compensation device of a frequency converter which uses a software table lookup method to calculate a dead zone compensation voltage value and method.

Inverter control technology, which is the most commonly used and commercially available in industrial applications, can be broadly classified into two types: scalar control and vector control. Although the scalar control compares the vector control to poor speed dynamic response, speed control ratio and control accuracy, the control system of scalar control is simple, easy to implement and less prone to divergence. Therefore, in some industries with non-servo purposes. Applications are still widely used. The scalar control is also the voltage/frequency control (V/f control), also known as the variable voltage variable frequency control (VVVF). In general, scalar control is an open loop control method that does not require feedback of the motor speed. The basic principle is to adjust the frequency of the motor supply power according to the speed command, that is, the output frequency of the inverter. Because the magnetic flux size of the motor is proportional to the ratio of the voltage to the frequency, the output voltage of the inverter must also be adjusted so that the ratio of the voltage to the operating frequency of the motor is maintained at a constant value, thereby maintaining the magnitude of the magnetic flux and controlling it. The purpose of the speed.

Although the voltage/frequency control is quite easy to implement, at low frequency and light load, due to the extremely small output voltage of the inverter, plus the voltage drop on the switch, etc., the error in the output voltage of the inverter is increased. Therefore, the control performance of the motor running at low frequency and light load becomes poor.

In addition, in the inverter driving circuit, since the power crystal has a non-ideal phenomenon of turn-on delay and turn-off delay, in reality, the power crystal does not arrive at the input command. Turn on or off immediately afterwards. In order to avoid the short circuit of the two crystals on the same arm in the non-completely on or off state, it is necessary to stagger in the middle of the upper and lower arm crystal conduction and cutoff, and delay for a period of time, which is called dead time or short circuit. Prevent time.

The short-circuit prevention time is to delay each power crystal (switch) from the moment of turn-off to the turn-on time, and the delay time must match the switching speed of the switch. However, after the short-circuit prevention time is added, the fundamental wave component of the output voltage of the inverter will decrease and the low-frequency harmonic component will increase. When the motor runs at a low speed, the influence of the low-frequency harmonics on the motor will be more obvious, especially under the open loop control. The output current will have a zero-crossing dead band phenomenon, causing distortion when the actual current crosses at zero.

Please refer to the block diagram of the circuit diagram for the dead zone compensation of the inverter in the first figure A. The dead zone compensation mode of this inverter is one of the commonly used compensation methods. As shown in the figure, the dead zone compensation mode of the inverter 20A calculates the required dead zone compensation amount by detecting the three-phase current of a motor 30A. That is, a current detecting circuit 40A is used to detect the input power supply current of the motor 30A, that is, the three-phase output current of the frequency converter 20A. The three-phase output current is received by a dead zone compensation module 50A for the three-phase output current of the frequency converter 20A, and according to the polarity of the three-phase current, the pulse width modulation (PWM) reference command value of each phase is Add or subtract (depending on the polarity of the current) a repair The positive amount is such that the generated dead zone compensation amount is a trapezoidal compensation curve in phase with the current. The dead zone compensation mode of such a frequency converter has the advantages of simple calculation, but the disadvantage is that the voltage compensation amount and the trapezoidal slope will deviate from the ideal value, resulting in a sudden change of the output current waveform, so that the motor will generate a rapid and slow speed when rotating. Continuous phenomenon, this distortion phenomenon is particularly noticeable at low frequency and light load (especially light load or even no load operation below 1 Hz).

In order to improve the above-mentioned motor output excitation waveform waveform excitation phenomenon at low frequency and light load, the other is one of the commonly used compensation methods, as follows: Please refer to Figure 1B for the known inverter dead zone compensation. Circuit block diagram. The dead zone compensation mode of such a frequency converter is a dead zone compensation mode using voltage feedback. That is to say, the dead zone compensation mode of the inverter is in addition to the above compensation mode, and a voltage detecting circuit 60A is additionally added. The voltage detecting circuit 60A is configured to detect the three-phase output voltage of the frequency converter 20A and determine the instantaneous voltage output difference. And according to the voltage output difference and the detected three-phase current polarity, the direction of the voltage compensation amount and the compensation amount thereof are obtained. In such a way that the dead zone compensation is performed by voltage feedback, the waveform of the output current is close to a pure sine wave, which is a smooth compensation curve. Compared with the first type of inverter dead zone compensation mode (such as the first figure A), the compensation amount is a trapezoid, which causes the current to be excited at the turning point of the trapezoid at the high voltage output, and also due to the trapezoidal compensation. The amount is inconsistent with the true compensation amount, which will cause a problem of excessive voltage compensation. Therefore, in addition to the advantages of high accuracy compensation, the dead zone compensation method of such a frequency converter can obtain a sinusoidal current with almost no distortion, so as to improve the output current waveform stimuli when the motor operates at low frequency and light load. But its disadvantage is In order to directly detect the voltage output difference, the voltage detecting circuit 60A must be additionally added. Therefore, compared with the first type of inverter dead zone compensation mode (such as the first figure A), it is necessary to add extra hard. The cost of the body circuit.

Therefore, how to design a pulse width modulation dead zone compensation device and method for a frequency converter can improve the problem of low frequency current excitation when the motor is running at low frequency and light load without adding additional hardware circuits. Faster output and instant response is a major issue that the creators of this case have to overcome and solve.

In order to solve the above problems, the present invention provides a pulse width modulation dead zone compensation device for a frequency converter. The on and off states of the internal switching components of the inverter are driven by a gate driving circuit for driving an induction motor controlled by variable voltage (V/f), and the three-phase output current of the inverter is It is detected by a current detecting circuit as an analog current. The pulse width modulation dead zone compensation device of the frequency converter comprises an analog digital conversion unit, a voltage frequency control unit, a dead zone compensation logic unit and a pulse width modulation generation unit.

The analog-to-digital conversion unit is connected to the current detecting circuit for receiving the analog detecting current and converting the analog detecting current into a digital detecting current; wherein, in the speed closed loop architecture, the analog digital converting unit The system is configured to receive an output frequency of the induction motor and convert the output frequency to a digital detection frequency. The voltage frequency control unit is connected to the analog digital conversion unit for receiving the digital detection frequency, wherein in the speed closed loop architecture, an external frequency command is also received, and the digital detection frequency is combined with the frequency command. Error value and according to the electricity The voltage frequency conversion relationship of the voltage frequency control unit outputs a corresponding reference voltage. The dead zone compensation logic unit is connected to the analog digital conversion unit and the voltage frequency control unit for receiving the digital detection current and the reference voltage, and outputting a voltage command. The pulse width modulation generating unit is coupled to the dead zone compensation logic unit for receiving and converting the voltage command, and outputting a pulse width modulation voltage command to the gate driving circuit.

The dead zone compensation logic unit comprises a root mean square value calculation unit, a divider, a first current voltage conversion unit, a second current voltage conversion unit, a multiplier and an adder. The rms calculation unit receives the digital detection current for calculating a rms value of the digital detection current as a substrate current. The divider is connected to the rms value calculation unit for calculating a ratio of the digital detection current to the substrate current as a standard current. The first current voltage conversion unit is connected to the rms value calculation unit for receiving the base current, and outputs a corresponding base compensation voltage according to the current voltage conversion relationship of the first current voltage conversion unit. The second current voltage conversion unit is connected to the divider for receiving the standard current, and outputs a corresponding compensation voltage according to the current voltage conversion relationship of the second current voltage conversion unit. The multiplier is connected to the first current voltage conversion unit and the second current voltage conversion unit for calculating a product of the standard compensation voltage and the base compensation voltage as a compensation voltage. The adder is coupled to the multiplier for summing up the compensation voltage and the reference voltage output by the voltage frequency control unit as the voltage command.

In order to solve the above problems, the present invention provides a pulse width of a frequency converter. Degree modulation dead zone compensation method. The frequency converter is used to drive an induction motor with variable voltage variable frequency control (V/f). The step of the pulse width modulation dead zone compensation method of the frequency converter includes: first, calculating the instantaneous value of the three-phase current output by the frequency converter as a three-phase current rms value. Then, using a look-up table method for a first current-voltage conversion relationship, a dead-band compensation voltage reference value is obtained. Then, the ratio of the instantaneous value of the three-phase current to the rms value of the three-phase current is calculated as a three-phase current value. Then, a second current-voltage conversion relationship is used to obtain a dead zone compensation voltage standard value by using a look-up table. Finally, the product of the dead zone compensation voltage reference value and the dead zone compensation voltage value is calculated as a dead zone compensation voltage value.

In order to further understand the technology, the means and the effect of the present invention in order to achieve the intended purpose, refer to the following detailed description of the invention and the accompanying drawings. The detailed description is to be understood as illustrative and not restrictive.

The technical content and detailed description of the creation are as follows: Please refer to the second figure. Figure A is the structural diagram of the induction motor drive system of the present invention under the control of the closed loop of the speed. As shown in FIG. A, a three-phase AC power source Vs is rectified into a DC voltage by a rectifier 10 composed of a plurality of diodes (not shown). Then, in order to eliminate the voltage chopping of the DC voltage after rectification, a capacitor (not labeled) is added after the rectifier 10 for voltage stabilization filtering to generate a rectified and filtered DC voltage Vd. At last, The DC voltage Vd is converted into a pulse voltage form by an inverter 20 to control an induction motor 30. The frequency converter 20 converts the alternating current source Vs of a fixed voltage and frequency into a variable frequency, variable voltage or variable current AC power source suitable for driving the variable speed operation of the induction motor 30.

In this creation, although the concepts and embodiments disclosed in the three-phase current and voltage component descriptions are used, the coordinate axicon transformation can be used to convert the abc three-axis coordinates into dq two-axis orthogonal coordinates, and the concept and implementation disclosed in this creation are implemented. The example is based on the dq two-axis orthogonal coordinates to achieve the same technical means. As for the technology of the coordinate axis conversion, the prior art is well known to those skilled in the art, and therefore will not be described in detail in this creation.

The invention further discloses a pulse width modulation dead zone compensation device for a frequency converter. The on and off states of the internal switching elements of the inverter 20 are driven by a gate driving circuit 40 for driving an induction motor 30 controlled by variable voltage (V/f), and the three phases of the inverter 20 The magnitude of the output current is detected by a current detecting circuit 50 as an analog current. Among them, the internal switching component of the inverter 20 can be an insulated gate bipolar transistor (IGBT) with high current, high voltage application and fast voltage gate full control function or other power that can achieve the same function. A transistor, such as a metal oxide semiconductor field effect transistor (MOSFET). In addition, the speed of the motor 30 can be detected by an encoder 32 mounted on the shaft of the motor 30 to provide speed feedback under the control of the closed loop of the speed. And, since the rotation speed of the motor 30 is proportional to the output frequency of the motor 30, Fi Therefore, the output frequency Fi of the motor 30 can be obtained according to the rotation speed of the motor 30 detected by the encoder 32.

The pulse width modulation dead zone compensation device of the frequency converter comprises an analog digital conversion unit 60, a voltage frequency control unit 70, a dead zone compensation logic unit 80 and a pulse width modulation generation unit 90.

The analog-to-digital conversion unit 60 is connected to the current detecting circuit 50 for receiving the analog detecting current Ia and converting the analog detecting current Ia to a digital detecting current Im. In addition, the analog digital converting unit 60 It is configured to receive the output frequency Fi of the induction motor 30, and convert the output frequency Fi to a digital detection frequency Fm. In the speed closed loop control architecture, the voltage frequency control unit 70 is coupled to the analog digital conversion unit 60 for receiving the digital detection frequency Fm and also receiving an external frequency command Fc. Therefore, the voltage frequency control unit 70 is configured to output a corresponding value according to the voltage frequency conversion relationship of the voltage frequency control unit 70 according to the error frequency (ie, the frequency difference) between the digital detection frequency Fm and the frequency command Fc. Reference voltage Vr. The dead zone compensation logic unit 80 is connected to the analog digital conversion unit 60 and the voltage frequency control unit 70 for receiving the digital detection current Im and the reference voltage Vr and outputting a voltage command Vc. The pulse width modulation generating unit 90 is connected to the dead zone compensation logic unit 80 for receiving and converting the voltage command Vc, and outputs a pulse width modulation voltage command Vp to the gate driving circuit 40. Additionally, the dead zone compensation logic unit 80 will be described in greater detail in conjunction with the third diagram.

Please refer to FIG. 2B, which is a structural diagram of the induction motor drive system of the present invention under the control of the speed open circuit. The principle of the speed open loop control is similar to the aforementioned speed closed loop control. However, the biggest difference between the two is: Under the speed open loop control architecture, the encoder 32 for speed feedback is not required. Therefore, the voltage frequency control unit 70 directly receives the external frequency command Fc, and outputs a corresponding reference voltage Vr according to the voltage frequency conversion relationship of the voltage frequency control unit 70. The subsequent signal processing is the same as the aforementioned speed closed loop control, and will not be described herein.

Please refer to the third figure for an internal block diagram of a dead zone compensation logic unit of the pulse width modulation dead zone compensation device of the present invention. As shown, the dead zone compensation logic unit 80 includes a root mean square value calculation unit 802, a divider 804, a first current voltage conversion unit 806, a second current voltage conversion unit 808, a multiplier 810, and An adder 812. The rms calculation unit 802 receives the digital detection current Im for calculating the rms value of the digital detection current Im as a base current Ib. The divider 804 is connected to the rms value calculation unit 802 for calculating a ratio of the digital detection current Im to the base current Ib as a standard current Ipu. The first current voltage conversion unit 806 is connected to the rms value calculation unit 802 for receiving the base current Ib, and outputs a corresponding base compensation voltage Vb according to the current voltage conversion relationship of the first current voltage conversion unit 806. . The second current-voltage conversion unit 808 is connected to the divider 804 for receiving the standard current Ipu, and outputs a corresponding compensation voltage Vpu according to the current-voltage conversion relationship of the second current-voltage conversion unit 808. The multiplier 810 is connected to the first current voltage conversion unit 806 and the second current voltage conversion unit 808 for calculating a product of the standard compensation voltage Vpu and the base compensation voltage Vb as a compensation voltage Vcom. The adder 812 is connected to the multiplier 810 for calculating the compensation voltage Vcom and the reference voltage Vr output by the voltage frequency control unit 70 as the voltage. Command Vc. It is worth mentioning that the dead zone compensation logic unit 80 further includes a current polarity unit (not shown), and the current polarity unit detects the polarity of the three-phase output current of the frequency converter 20 according to the current detecting circuit 50. The increase and decrease direction of the compensation voltage Vcom is generated to provide a correct voltage compensation amount.

Please refer to FIG. 4A and FIG. 4B respectively for current-voltage conversion relationship curves of the first current voltage conversion unit and the second current voltage conversion unit, wherein the two curves are a function curve of substantially monotonically increasing. As shown in FIG. 4A, the abscissa is the base current Ib (in amps) calculated by the digital detection current Im obtained by the root mean square value calculation unit 802, and the ordinate is the ordinate. The base compensation voltage Vb (in volts) obtained by the current-voltage conversion relationship of the first current-voltage conversion unit 806. It is worth mentioning that the current-voltage conversion relationship of the first current-voltage conversion unit 806 is used to measure the on and off times of the internal switching elements of the inverter 20, and the conversion relationship between the base current Ib and the base compensation voltage Vb is obtained. . In addition, the current-voltage conversion relationship of the first current-voltage conversion unit 806 is also performed by using a software for DC injection, and the difference between the theoretical voltage output and the actual voltage output is used to obtain the base current Ib and the base compensation voltage Vb. Conversion relationship. It is worth mentioning that the discrete data of the current-voltage conversion relationship of the first current-voltage conversion unit 806 is fitted to a continuous function by an interpolation method or a predetermined numerical analysis method to provide a complete instantaneous sampling current and Corresponding voltage relationship.

As shown in the fourth figure A, an example is illustrated. When the rms value calculation unit 802 calculates that the base current Ib is 5 amps, the table lookup method is used. The base compensation voltage Vb can be directly obtained by the current-voltage conversion relationship of the first current-voltage conversion unit 806 to be 5.06 volts; or when the substrate current Ib is 10 amps, the base compensation voltage Vb can be directly obtained as 5.75 tex. . However, if the rms calculation unit 802 calculates that the base current Ib is 7.3 amps (the base compensation voltage Vb does not correspond exactly), the method may be fitted by interpolation or predetermined numerical analysis to calculate the base. The current Ib is approximately 5.39 volts.

As shown in FIG. 4B, the abscissa is the digital current Ipu (the unit is the standard) calculated by the ratio of the digital detection current Im to the base current Ib, and the ordinate is the first The current-voltage conversion relationship of the two current-voltage conversion units 808 is obtained by the calibration voltage Vpu (in units of the standard). It is worth mentioning that the current-voltage conversion relationship of the second current-voltage conversion unit 808 is obtained by measuring the conduction and the off-time of the internal switching elements of the inverter 20 to obtain the conversion of the standard current Ipu and the standard compensation voltage Vpu. relationship. In addition, the current-voltage conversion relationship of the second current-voltage conversion unit 808 is also performed by using a software for DC injection, and the difference between the theoretical voltage output and the actual voltage output is used to obtain the standard current Ipu and the standard compensation voltage. Vpu conversion relationship. It is worth mentioning that the discrete data of the current-voltage conversion relationship of the second current-voltage conversion unit 808 is fitted to a continuous function by an interpolation method or a predetermined numerical analysis method to provide a complete instantaneous sampling current and Corresponding voltage relationship.

As shown in the fourth figure B, an example is illustrated. When the divider 804 calculates that the standard current Ipu is 0.2, it can directly obtain the current-voltage conversion relationship of the second current-voltage conversion unit 808 by using the look-up table. The standard compensation voltage Vpu is 0.8 standard; or when the standard current Ipu is 0.4 standard, then the standard compensation voltage Vpu is 0.93 standard. However, if the divider 804 calculates that the current Ipu is 0.35 (does not correspond to the standard compensation voltage Vpu), it can be fitted by interpolation or predetermined numerical analysis to calculate the standard. The current Ipu is about 0.89.

Please refer to the fifth figure for the flow chart of the pulse width modulation dead zone compensation method of the present invention. The frequency converter is used to drive an induction motor controlled by variable voltage (V/f). Moreover, the steps of the pulse width modulation dead zone compensation method of the frequency converter are as follows.

Firstly, the first current-current voltage conversion relationship and a second current-voltage conversion relationship are established by measuring the on and off times of the internal switching elements of the inverter. In addition, a soft body is used for DC injection, and the difference between the theoretical voltage output and the actual voltage output is used to establish a relationship between the first current voltage conversion relationship and the second current voltage conversion relationship. Then, the instantaneous value of the three-phase current outputted by the inverter is calculated as a three-phase current rms value (S10). Then, using the look-up table method for the first current-voltage conversion relationship, a dead zone compensation voltage reference value is obtained (S20). Then, calculating a ratio of the instantaneous value of the three-phase current to the rms value of the three-phase current is a three-phase current value (S30). Then, the second current-voltage conversion relationship is obtained by using a look-up table method to obtain a dead zone compensation voltage value (S40). Then, the product of the dead zone compensation voltage reference value and the dead zone compensation voltage value is calculated as a dead zone compensation voltage value (S50). Finally, the dead zone compensation voltage value and one of the reference voltages generated by the variable voltage variable frequency control are summed to generate a pulse width modulation voltage command and pushed through a gate drive circuit. The internal switching element of the inverter is turned on and off to control the operation of the motor.

It is worth mentioning that in the step (S20) and the step (S40), since the first current voltage conversion relationship and the second current voltage conversion relationship are not continuous functions, when the first current voltage conversion relationship is utilized, When the second current-voltage conversion relationship is the basis for the look-up table, since not all of the instantaneous sampling currents can obtain the corresponding voltage (please refer to the fourth figure A and the fourth figure B), the interpolation method is used. (interpolation method) or a method of predetermined numerical analysis fitting the discrete data of the first current-voltage conversion relationship and the second current-voltage conversion relationship as a continuous function to provide a complete instantaneous sampling current and a corresponding voltage relationship.

In addition, the above steps are processed by a digital signal processor (DSP).

In summary, the present invention has the following advantages:

1. Using the measurement to measure the on and off time of the internal switching component of the inverter or DC injection using the software, and establishing the first current voltage conversion unit and the second current voltage conversion according to the difference between the theoretical voltage output and the actual voltage output. The current-voltage conversion relationship of the unit, and using the lookup table method, only need to cooperate with the interpolation method or the predetermined numerical analysis method, thereby eliminating the complicated current-voltage conversion calculation and greatly reducing The computational complexity, as such, will provide faster output and immediate response in instant control applications. That is, as long as the three-phase instantaneous current is obtained After calculating the rms current value of the three-phase current, the compensation amount of the dead zone compensation voltage can be adjusted instantly.

2. Using the software look-up table method, the dead-band compensation method of analog voltage feedback mode can not only obtain the advantage of high-accuracy compensation amount, but also obtain the sinusoidal current with almost no distortion to improve the motor operation at low frequency and light load. The output current waveform is violent.

3. Using the software table look-up method, the inverter is driven to drive an induction motor with variable voltage frequency conversion (V/f) control, and is suitable for speed closed loop and speed open loop control. Only the current feedback can be used to output the correct voltage value without using an additional voltage detection circuit, which can achieve a more accurate voltage compensation without increasing the hardware cost.

However, the above description is only for the detailed description and the drawings of the preferred embodiments of the present invention, and the present invention is not limited thereto, and is not intended to limit the present invention. The scope of the patent application is intended to be included in the scope of the present invention, and any one skilled in the art can readily appreciate it in the field of the present invention. Variations or modifications may be covered by the patents in this case below.

[technical technology]

20A‧‧‧Inverter

30A‧‧‧Motor

40A‧‧‧current detection circuit

50A‧‧‧ Dead Zone Compensation Module

60A‧‧‧Voltage detection circuit

〔this invention〕

Vs‧‧‧AC power supply

10‧‧‧Rectifier

20‧‧‧Inverter

30‧‧‧Induction motor

32‧‧‧Encoder

40‧‧‧ gate drive circuit

50‧‧‧ Current detection circuit

60‧‧‧ analog digital conversion unit

70‧‧‧Voltage frequency control unit

80‧‧‧ Dead Zone Compensation Logic Unit

802‧‧‧ rms calculation unit

804‧‧‧ divider

806‧‧‧First current voltage conversion unit

808‧‧‧Second current voltage conversion unit

810‧‧‧Multiplier

812‧‧‧Adder

90‧‧‧ Pulse width modulation generating unit

Ia‧‧‧ analog detection current

Im‧‧‧ digital detection current

Fc‧‧‧ frequency life

Fi‧‧‧ output frequency

Fm‧‧‧ digital detection frequency

Vr‧‧‧reference voltage

Vc‧‧‧voltage command

Vp‧‧‧ pulse width modulation voltage command

Ib‧‧‧Base current

Ipu‧‧‧ standard current

Vb‧‧‧base compensation voltage

Vpu‧‧‧ standard compensation voltage

Vcom‧‧‧compensation voltage

S10~S50‧‧‧Steps

The first figure A is a circuit block diagram of the conventional inverter dead zone compensation; the first figure B is a circuit block diagram of the conventional inverter dead zone compensation; the second figure A is the induction motor drive system of the present invention at the speed closed circuit Under the control of the architecture diagram; the second diagram B is the induction motor drive system of the present invention in the open loop control The third diagram is the internal block diagram of the pulse width modulation dead zone compensation device of the present invention, a dead zone compensation logic unit; and the fourth diagram A is a current-voltage conversion relationship diagram of the first current voltage conversion unit. FIG. 4B is a current-voltage conversion relationship diagram of a second current-voltage conversion unit; and a fifth diagram is a flowchart of the pulse width modulation dead-band compensation method of the present invention.

S10~S50‧‧‧Steps

Claims (18)

The pulse width modulation dead zone compensation device of the frequency converter, wherein the on and off states of the internal switching components of the frequency converter are driven by a gate driving circuit for driving an induction motor controlled by variable voltage frequency conversion, and The three-phase output current of the frequency converter is detected by a current detecting circuit as an analog current; the pulse width modulation dead zone compensation device of the frequency converter includes: an analog-to-digital conversion unit that is connected to the current The detecting circuit is configured to receive the analog detecting current and convert the analog detecting current into a digital detecting current; wherein, in the speed closed loop architecture, the analog digital converting unit is configured to receive the output of the induction motor Frequency, and converting the output frequency to a digital detection frequency; a voltage frequency control unit is connected to the analog digital conversion unit for receiving the digital detection frequency; wherein, in the speed closed loop architecture, a receiving frequency is also received An external frequency command, and the error value of the digital detection frequency and the frequency command is converted according to the voltage frequency of the voltage frequency control unit And outputting a corresponding reference voltage; a dead zone compensation logic unit is connected to the analog digital conversion unit and the voltage frequency control unit for receiving the digital detection current and the reference voltage, and outputting a voltage command; the dead zone compensation The logic unit includes: a rms calculation unit that receives the digital detection current for calculating a rms value of the digital detection current as a base current; and a divider connecting the rms value a calculation unit, configured to calculate a ratio of the digital detection current to the substrate current as a standard current; a first current voltage conversion unit is connected to the rms calculation unit for receiving the base current, and according to The first current voltage conversion unit a current-voltage conversion relationship, outputting a corresponding base compensation voltage; a second current-voltage conversion unit is connected to the divider for receiving the standard current, and according to the current-voltage conversion relationship of the second current-voltage conversion unit, Outputting a corresponding compensation voltage; a multiplier connecting the first current voltage conversion unit and the second current voltage conversion unit for calculating a product of the standard compensation voltage and the base compensation voltage as a compensation voltage And an adder connected to the multiplier for summing up the compensation voltage and the reference voltage output by the voltage frequency control unit as the voltage command; and a pulse width modulation generating unit connecting the dead zone And a compensation logic unit for receiving and converting the voltage command and outputting a pulse width modulation voltage command to the gate driving circuit. For example, the pulse width modulation dead zone compensation device of the frequency converter of claim 1 is, wherein, in the speed open loop control, the voltage frequency control unit directly receives the external frequency command, and according to the voltage frequency control unit The voltage-frequency conversion relationship outputs a corresponding reference voltage. For example, the pulse width modulation dead zone compensation device of the frequency converter of claim 1 , wherein the current voltage conversion relationship of the first current voltage conversion unit is a monotonically increasing curve. For example, the pulse width modulation dead zone compensation device of the frequency converter of claim 1 , wherein the current voltage conversion relationship of the second current voltage conversion unit is a monotonically increasing curve. For example, the pulse width modulation dead zone compensation device of the frequency converter of claim 1 wherein the current voltage conversion relationship of the first current voltage conversion unit is used to measure the conduction and cutoff time of the internal switching component of the frequency converter. The conversion relationship of the substrate current to the substrate compensation voltage is obtained. For example, the pulse width modulation dead zone compensation device of the frequency converter of claim 1 wherein the current voltage conversion relationship of the second current voltage conversion unit is used to measure the conduction and cutoff time of the internal switching component of the frequency converter. Find the conversion relationship between the standard current and the compensation voltage. For example, the pulse width modulation dead zone compensation device of the frequency converter of the first application patent scope, wherein the current voltage conversion relationship of the first current voltage conversion unit is a DC injection using a software, and the theoretical voltage output and the actual voltage are matched. The difference between the outputs is used to determine the conversion relationship of the substrate current to the substrate compensation voltage. For example, the pulse width modulation dead zone compensation device of the frequency converter of the first application patent scope, wherein the current voltage conversion relationship of the second current voltage conversion unit is a DC injection using a software, and the theoretical voltage output and the actual voltage are matched. The difference between the outputs and the conversion relationship of the standard current to the standard compensation voltage. The pulse width modulation dead zone compensation device of the frequency converter of claim 1 , wherein the discrete data of the current-voltage conversion relationship between the first current voltage conversion unit and the second current voltage conversion unit is performed by interpolation The interpolation method is fitted as a continuous function. The pulse width modulation dead zone compensation device of the frequency converter of claim 1, wherein the discrete data of the current-voltage conversion relationship between the first current voltage conversion unit and the second current voltage conversion unit utilizes a predetermined value The method of analysis is fitted as a continuous function. For example, the pulse width modulation dead zone compensation device of the frequency converter of claim 1 is characterized in that the internal switching component of the inverter is an insulated gate bipolar transistor (IGBT). A pulse width modulation dead zone compensation method for a frequency converter, the frequency converter is used The driving motor is driven by a variable voltage variable frequency control; the step of the pulse width modulation dead zone compensation method of the frequency converter comprises: (a) calculating the instantaneous value of the three-phase current outputted by the frequency converter The square root value; (b) using a look-up table for a first current-voltage conversion relationship to obtain a dead zone compensation voltage reference value; (c) calculating a ratio of the instantaneous value of the three-phase current to the rms value of the three-phase current a three-phase current standard value; (d) a second current-voltage conversion relationship using a look-up table method to obtain a dead zone compensation voltage standard value; and (e) calculating the dead zone compensation voltage reference value and the dead zone compensation voltage standard The product of the value is a dead zone compensation voltage value. For example, in the method of claim 12, after the step (e), the method further comprises: (f) summing the dead zone compensation voltage value and one of the reference voltages generated by the variable voltage frequency conversion control to generate a pulse wave. Width modulation voltage command. For example, in the method of claim 13, the step (a) to the step (f) are processed by a digital signal processor (DSP). For example, in the method of claim 12, before the step (a), the on-and-off time of the internal switching component of the inverter is measured, and the relationship between the first current-voltage conversion relationship and the second current-voltage conversion relationship is established. . For example, in the method of claim 12, before the step (a), the DC injection is performed by using the software, and the first current-voltage conversion relationship and the second current are established according to the difference between the theoretical voltage output and the actual voltage output. Voltage conversion relationship. In the method of claim 12, in the step (a) and the step (d), the first current-voltage conversion relationship is converted into the second current-voltage relationship by an interpolation method. The discrete data is fitted as a continuous function. In the method of claim 12, in the step (a) and the step (d), the relationship between the first current-voltage conversion relationship and the second current-voltage conversion relationship is separated by a predetermined numerical analysis method. The data is fitted as a continuous function.