阅读说明：本技术 电梯变频器pwm调制方法 (PWM modulation method for elevator frequency converter ) 是由 丁习兵 高建涛 于 2019-09-09 设计创作，主要内容包括：本发明涉及变频器驱动控制领域,提出了一种电梯变频器PWM调制方法,旨在解决电梯在低速启动及在需要持续长时间的过载力矩时,当前使用的PWM调制方式使得IGBT模块开关存在结温比较高,过载能力有限的问题。该方法包括：获取待调制电路波的三相调制矢量,确定上述三相调制矢量中各相调制矢量占空比的最大值和最小值；根据上述各相调制矢量占空比的最大值和最小值,确定上述待调制电路波的连续零矢量波；在上述连续零矢量波中注入低频调制波,生成基础矢量波；将上述基础矢量波与上述三项调制矢量中所述各相调制矢量进行调制,得到电梯变频器PWM调制矢量波。本发明减少了开关器件导通损耗及开关损耗,降低了开关器件的结温,提高了IGBT模块的过载能力。(The invention relates to the field of frequency converter drive control, provides a PWM (pulse-width modulation) method for an elevator frequency converter, and aims to solve the problems that an IGBT (insulated gate bipolar translator) module switch has higher junction temperature and limited overload capacity due to the currently used PWM method when an elevator is started at a low speed and overload torque needs to be continued for a long time. The method comprises the following steps: acquiring a three-phase modulation vector of a circuit wave to be modulated, and determining the maximum value and the minimum value of the duty ratio of each phase modulation vector in the three-phase modulation vector; determining continuous zero vector waves of the circuit waves to be modulated according to the maximum value and the minimum value of the duty ratio of the modulation vectors of each phase; injecting a low-frequency modulation wave into the continuous zero vector wave to generate a basic vector wave; and modulating the basic vector wave and each phase modulation vector in the three modulation vectors to obtain a PWM (pulse-width modulation) vector wave of the elevator frequency converter. The invention reduces the conduction loss and the switching loss of the switching device, reduces the junction temperature of the switching device and improves the overload capacity of the IGBT module.)

1. A PWM modulation method of an elevator frequency converter is characterized by comprising the following steps:

acquiring a three-phase modulation vector of a circuit wave to be modulated, and determining the maximum value and the minimum value of the duty ratio of each phase modulation vector in the three-phase modulation vector;

determining continuous zero vector waves of the circuit waves to be modulated according to the maximum value and the minimum value of the duty ratio of each phase of modulation vector;

injecting a low-frequency modulation wave into the continuous zero vector wave to generate a basic vector wave, wherein the low-frequency modulation wave is a low-frequency cosine wave;

and modulating the basic vector wave and each phase modulation vector in the three modulation vectors to obtain a PWM (pulse-width modulation) vector wave of the elevator frequency converter.

2. The elevator frequency converter PWM modulation method according to claim 1, characterized in that the three-phase modulation vector duty cycle of the circuit wave to be modulated is determined by the following formula:

d_u＝m cosθ

d_v＝mcos(θ-120°)

d_w＝mcos(θ+120°)

m＝2*V_m/V_dc

wherein d is_u、d_v、d_wAre respectively threeU-phase duty ratio, V-phase duty ratio, W-phase duty ratio, and V of phase power supply_m、V_dcRespectively an output phase voltage effective value and a direct current bus voltage.

3. Elevator frequency converter PWM modulation method according to claim 2, characterized in that said low frequency modulation wave is kcos (2 π f)₀t), where k is a low frequency coefficient, f)₀To output frequency, t is time.

4. The elevator inverter PWM modulation method according to claim 3, wherein said "injecting a low frequency modulation wave in said continuous zero vector wave to generate a base vector wave" comprises generating a base vector wave by the following formula:

wherein d is_0，SDPWMBased on vector waves, d_minIs the maximum small value of the three-phase duty ratio, d_maxAt the maximum value of the three-phase duty ratio, k cos (2 π f)₀t) is a low frequency modulation wave.

5. The elevator frequency converter PWM method according to claim 4, wherein said modulating said fundamental vector wave with each of said three modulation vectors to obtain an elevator frequency converter PWM vector wave comprises obtaining an elevator frequency converter PWM vector wave by the following formula:

d_x，SDPWM＝d_0，SDPWM+d_{x＝u、v、w}

wherein d is_x，SDPWMFor PWM modulation vector wave of elevator frequency converter, x is one phase of u, v and w, d_0，SDPWMBased on vector waves, d_{x＝u、v、w}The duty ratio of the U phase, the V phase or the W phase in the three-phase power supply.

Technical Field

The invention relates to the field of frequency converter drive control, in particular to a PWM (pulse-width modulation) method for an elevator frequency converter.

Background

When the elevator is started at a low speed or self-learns in a hoistway, overload torque with low frequency of a frequency converter and long duration is needed, wherein 150-180% of the overload torque is needed, and the duration is about 3-5 s; in the slip test, the frequency converter is 200%, and the overload torque is 0 HZ. In low-speed, high-torque operation, the switching devices (IGBT modules) of the frequency converter become hot and increase the power losses associated with the operation of the IGBT modules. The overload capability of the IGBT module of the frequency converter is limited by the junction temperature, and thus the overload capability of the frequency converter can be increased by reducing the over-junction temperature of the IGBT switches.

The heating value of the chip can be reduced in a PWM (pulse-width modulation) mode, and the junction temperature can be reduced by adopting a traditional continuous SVPWM (space vector pulse-width modulation) algorithm, so that the IGBT module has the defects of large loss, high junction temperature and limited overload capacity in the low-speed running and slipping test process of the elevator; by adopting the traditional discontinuous DPWM (digital pulse width modulation) algorithm, the switching loss of an IGBT (insulated gate bipolar translator) module can be effectively reduced in the low-speed running and slipping test process of an elevator, but the conduction loss can not be reduced, and the reduction amplitude of the junction temperature is limited because the proportion of the conduction loss is large.

Therefore, a PWM modulation method is needed to effectively reduce the conduction loss, further effectively reduce the heat productivity of the chip, reduce the temperature of the chip, and increase the overload capability of the frequency converter.

Disclosure of Invention

In order to solve the problems in the prior art, namely, to solve the problem that the overload torque with low frequency and long duration of the frequency converter is needed when the elevator is started at low speed or self-learns in a hoistway, the currently used PWM modulation mode causes the problems of high junction temperature and limited overload capacity of an IGBT module switch. The invention adopts the following technical scheme to solve the problems:

the application provides a PWM (pulse-width modulation) method of an elevator frequency converter, which comprises the following steps: acquiring a three-phase modulation vector of a circuit wave to be modulated, and determining the maximum value and the minimum value of the duty ratio of each phase modulation vector in the three-phase modulation vector; determining continuous zero vector waves of the circuit waves to be modulated according to the maximum value and the minimum value of the duty ratio of the modulation vectors of each phase; injecting a low-frequency modulation wave into the continuous zero vector wave to generate a basic vector wave, wherein the low-frequency modulation wave is a low-frequency cosine wave; and modulating the basic vector wave and each phase modulation vector wave in the three modulation vectors to obtain a PWM modulation vector wave of the elevator frequency converter.

In some examples, the three-phase modulation vector duty cycle of the circuit wave to be modulated is determined by the following formula:

d_u＝mcosθ

d_v＝mcos(θ-120°)

d_w＝mcos(θ+120°)

m＝2*V_m/V_dc

wherein d is as defined above_u、d_v、d_wThe U-phase duty ratio, the V-phase duty ratio, the W-phase duty ratio and the V-phase duty ratio of a three-phase power supply are respectively_m、V_dcRespectively an output phase voltage effective value and a direct current bus voltage.

In some examples, the low frequency modulation wave is k cos (2 π f)₀t), where k is a low frequency coefficient, f)₀To output frequency, t is time.

In some examples, the "injecting a low-frequency modulation wave into the continuous zero vector wave and generating a base vector wave" includes generating the base vector wave by the following formula:

wherein d is_0，SDPWMBased on vector waves, d_minIs the maximum small value of the three-phase duty ratio, d_maxAt the maximum of the three-phase duty cycle, kcos (2 π f)₀t) is a low-frequency modulated wave

In some examples, the "modulating the basic vector wave with each vector wave in the three modulation vectors to obtain the elevator frequency converter PWM modulation vector wave" includes obtaining the elevator frequency converter PWM modulation vector wave by the following formula:

d_x，SDPWM＝d_0，SDPWM+d_{x＝u、v、w}

wherein d is_x，SDPWMFor PWM modulation vector wave of elevator frequency converter, x is one phase of u, v and w, d_0，SDPWMBased on vector waves, d_{x＝u、v、w}The duty ratio of the U phase, the V phase or the W phase in the three-phase power supply.

According to the elevator frequency converter PWM method, the low-frequency modulation wave is injected into the continuous zero vector wave to generate the basic vector wave, and then the basic vector wave and each phase modulation vector wave in the three modulation vectors are modulated to obtain the elevator frequency converter PWM vector wave. The PWM modulation signal applied to the IGBT module is more regular and compact, the conduction loss and the switching loss of the switching device are reduced, the heat productivity of a chip is reduced, the junction temperature of the switching device in working is reduced, and the overload capacity and the overload time are improved.

Drawings

FIG. 1 is a schematic diagram of an exemplary system architecture to which embodiments of the present application may be applied;

fig. 2 is a schematic flow chart of an implementation of a PWM modulation method of an elevator inverter according to the present application;

FIG. 3 is a schematic diagram of a PWM modulation waveform generated by a prior art SVPWM modulation method;

FIG. 4 is a schematic diagram of a PWM modulation waveform generated based on the DPWM modulation method;

fig. 5 is a schematic waveform diagram of a PWM modulation wave generated by a PWM modulation method of an elevator frequency converter in an embodiment of the present application;

fig. 6 is a schematic diagram of losses of switching devices in a conventional frequency converter driven by a PWM modulated wave generated based on an SVPWM modulation method;

FIG. 7 is a schematic diagram of losses of switching devices in a prior art fundamental DPWM modulation method generated PWM modulated wave driven frequency converter;

fig. 8 is a schematic diagram of losses of switching devices in a frequency converter driven by a PWM modulated wave generated based on a PWM modulation method of an elevator frequency converter in the present application;

fig. 9 is a schematic diagram of junction temperatures of switching devices in a prior art PWM-modulated wave-driven frequency converter generated based on the SVPWM modulation method;

fig. 10 is a schematic diagram of junction temperatures of switching devices in a prior art PWM-modulated wave-driven frequency converter generated based on a DPWM modulation method;

fig. 11 is a schematic diagram of junction temperatures of switching devices in a frequency converter driven by a PWM-modulated wave generated based on a PWM modulation method of an elevator frequency converter in the present application.

Detailed Description

Preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only for explaining the technical principle of the present invention, and are not intended to limit the scope of the present invention.

It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present application will be described in detail below with reference to the embodiments with reference to the attached drawings.

FIG. 1 illustrates an exemplary system block diagram to which embodiments of the present application may be applied.

As shown in fig. 1, the system applied to the PWM modulation method of the elevator frequency converter includes: a filtering unit 101, a rectifying unit 102, an inverting unit 103, and a PWM generator unit 104. The rectifying unit is connected with a power grid through a filtering unit 101, rectifies alternating current provided by the power grid into direct current, and the filtering unit 101 performs smoothing filtering processing on power provided by the power grid. The inverter unit 103 inverts the dc power output from the rectifier unit 102 into ac power with variable frequency and voltage for the load. The PWM generator unit 104 generates a PWM signal to drive the controllable switching device of the inverter unit 103, thereby controlling the voltage and/or frequency of the output power of the inverter unit 103.

The filtering unit 101, the rectifying unit 102 and the inverting unit 103 are main components of the frequency converter, and realize the adjustment of voltage or frequency of a power supply provided by a power grid. The PWM generator unit 104 generates a driving signal for modulating the inverter unit 103 according to a preset program or logic and sensing data collected by various sensing devices associated with the inverter system. The PWM generator unit 104 may include a signal generating unit and a controller having logic operation and storage functions, such as various micro control chips.

With continuing reference to fig. 2, fig. 2 illustrates a flow of one embodiment of an elevator inverter PWM modulation method according to the present application. The PWM method of the elevator frequency converter comprises the following steps:

step 201, obtaining three-phase modulation vectors of a circuit wave to be modulated, and determining the maximum value and the minimum value of the duty ratio of each phase modulation vector in the three-phase modulation vectors.

In this embodiment, the PWM signal generator unit 104 in the inverter control system applied to the elevator inverter PWM modulation method receives various types of information, and generates a PWM signal for driving and controlling the on/off of the switching device in the inverter according to the received various types of information. The information received by the PWM signal generator 104 may be information collected by various sensing devices connected thereto, or information extracted from the PWM signal applied to the rectifying unit or the inverting unit generated by the PWM generator unit 104. Here, the PWM generator unit 104 obtains the three-phase modulation vectors of the circuit waves to be modulated, and determines the maximum value and the minimum value of the duty ratio of the modulation vectors of each phase in the three-phase modulation vectors, which may be obtained by obtaining the duty ratios of the PWM modulation circuits of each phase of the three-phase circuit, respectively, and determining the maximum value and the minimum value of the duty ratio of the modulation vectors of the three phases by comparison. Specifically, the initial three-phase modulation vector duty cycle may be preset values, such as 90% and 10%, or may be a randomly generated duty cycle.

In some specific designs of the present embodiment, the three-phase modulation vector duty ratio of the circuit wave to be modulated is determined by the following formula:

d_u＝mcosθ (1)

d_v＝mcos(θ-120°) (2)

d_w＝mcos(θ+120°) (3)

m＝2*V_m/V_dc(4)

wherein, in the above formulas (1) - (4), d_u、d_v、d_wThe U-phase duty ratio, the V-phase duty ratio, the W-phase duty ratio and the V-phase duty ratio of a three-phase power supply are respectively_m、V_dcRespectively an effective value of the output phase voltage and a DC bus voltage

Selecting the U-phase duty ratio, the V-phase duty ratio and the W-phase duty ratio based on the U-phase duty ratio, the V-phase duty ratio and the W-phase duty ratio, wherein the maximum value and the minimum value of the W-phase duty ratio are the maximum value and the minimum value of the three-phase modulation vector duty ratio, and the method specifically comprises the following steps:

d_min＝min(d_u,d_v,d_w) (5)

d_max＝max(d_u,d_v,d_w) (6)

in the above equations (5) and (6), min is the minimum value operation, max is the maximum value operation, and d_minAnd is d_maxThe maximum value and the minimum value of the duty ratio of the three-phase modulation vector.

Step 202, determining continuous zero vector wave of the circuit wave to be modulated according to the maximum value and the minimum value of the duty ratio of the modulation vector of each phase.

In the present embodiment, the maximum value d of the three-phase duty ratio obtained in step 201 is used as the basis_maxAnd a minimum value d_minThe PWM signal generator unit 104 obtains a continuous zero vector wave d by using a discontinuous DPWM modulation method₀And the switching loss can be effectively reduced. Wherein, the continuous vector wave d₀Comprises the following steps:

wherein d is₀Is a continuous vector wave.

And step 203, injecting a low-frequency modulation wave into the continuous zero vector wave to generate a basic vector wave.

In some specific designs of this embodiment, a low-frequency modulation wave is injected into the continuous zero vector wave to generate a basic vector wave, where the low-frequency modulation wave is a low-frequency cosine wave. Specifically, the low-frequency modulation wave may be kcos (2 π f)₀t), where k is a low frequency coefficient, f)₀To output frequency, t is time.

Specifically, the "injecting a low-frequency modulation wave into the continuous zero vector wave to generate a base vector wave" includes generating the base vector wave by the following formula:

in the formula (8) d_0，SDPWMBased on vector waves, d_minIs the maximum small value of the three-phase duty ratio, d_maxBeing said three-phase duty cycleMaximum value, k cos (2 π f)₀t) is a low frequency modulation wave.

And 204, modulating the basic vector wave and each phase modulation vector in the three modulation vectors to obtain a PWM (pulse-width modulation) vector wave of the elevator frequency converter.

In this embodiment, based on the basic vector wave determined in step 203, each vector wave in the three modulation vectors is added to the basic vector wave to obtain a PWM modulation vector wave for driving the elevator frequency converter. Here, each of the phasor vectors added to the basic phasor wave may be each of the phasors obtained in step 1. In this embodiment, each vector wave of each phase added to the basic vector wave is: d_u,d_v,d_w. Specifically, the PWM modulation vector wave of the elevator frequency converter is obtained through the following formula:

d_x，SDPWM＝d_0，SDPWM+d_{x＝u、v、w}(9)

in the above formula (9), d_{x＝u、v、w}Duty ratio of U-phase, V-phase or W-phase in three-phase power supply, d_x，SDPWMFor PWM modulation vector wave of elevator frequency converter, x is one phase of u, v and w, d_0，SDPWMIs a basic vector wave. Equation (9) can be specifically decomposed into:

d_u，SDPWM＝d_0，SDPWM+d_u(9-1)

d_v，SDPWM＝d_0，SDPWM+d_v(9-2)

d_w，SDPWM＝d_0，SDPWM+d_w(9-3)

d in the above formulae (9-1) to (9-3)_u，SDPWM、d_v，SDPWM、d_w，SDPWMRespectively represents the U-phase, V-phase and W-phase PWM vector waves in the PWM vector waves of the elevator frequency converter. The PWM signal generator unit 104 generates a PWM modulation vector wave shown by the above equation (9) to drive the inverter.

In the embodiment of the application, continuous zero vector waves are determined through the maximum value and the minimum value of the duty ratio of the three-phase modulation vector with the modulation circuit, then the low-frequency modulation zero vector is added to generate basic vector waves, each phase of modulation vector waves are injected into the basic vector waves, and the PWM vector waves of the elevator frequency converter are obtained through modulation. Compared with the prior art, the method has the following beneficial effects:

effectively reduce conduction loss, and then reduce chip calorific capacity, reduce chip temperature, increase the overload capacity of converter.

Referring to fig. 3-5, fig. 3-5 show graphs comparing a PWM modulated wave generated based on the PWM modulation method of the elevator inverter in the present application with a PWM modulated wave generated based on the prior SVPWM and DPWM modulation methods. The PWM modulation wave generated by the PWM modulation method of the elevator frequency converter is more regular and compact, and distribution of IGBT loss can be optimized.

Further, the output current i can be output according to the frequency converter_u、i_v、i_wAnd calculating the loss of the switching device IGBT and the DIODE DIODE by the duty ratio of the PWM signal for driving the frequency converter.

The turn-on losses (for example, U-phase) of the IGBTs and DIODEs are:

wherein P in the formulas (10) and (11)_con(IGBT) and P_con(diode) is the conduction loss, V, of the IGBT and diode_dRated conduction voltage drop, R, of IGBT_dThe rated on-resistance of the IGBT. V can be referred to in the specification of the IGBT module_dAnd R_dThe data of (1).

Switching losses (for example, U-phase) of the IGBTs and DIODEs are:

wherein, in the formulas (12) and (13), P_S(IGBT) and P_S(diode) switching losses of IGBT and diode, E_onFor the rated turn-on voltage drop of the IGBT, E_offFor the rated turn-off voltage of the IGBT, in particular, the parameter E can be consulted in the specification of the IGBT module_onAnd E_offThe data of (1). V_nAnd I_nThe rated voltage and rated current of the IGBT module, which define the switching losses, are provided with corresponding data on the specification of the IGBT module.

Based on the conduction loss and the switching loss of the IGBT and the diode, the total loss of the IGBT and the diode is calculated as follows:

P(IGBT)＝P_s(IGBT)+P_con(IGBT) (14)

P(diode)＝P_s(diode)+P_con(diode (15)

in the above formulas (14) and (15), p (IGBT) and p (diode) are the total loss of the IGBT as the switching device and the total loss of the diode in the frequency converter, respectively.

Referring to fig. 6-8, fig. 6-8 show graphs comparing the losses of switching devices in a PWM-modulated wave driven inverter generated based on the PWM modulation method of an elevator inverter in the present application with the losses of switching devices in a PWM-modulated wave driven inverter generated based on the SVPWM and DPWM modulation methods of the related art. The switching device in the application can be determined to have the lowest loss in operation, and the rise of the loss can be timely restrained through the regular and compact modulation wave, so that the loss in the whole operation period is reduced.

And the controller in the frequency converter can calculate the junction temperatures of the IGBT and the diode according to the total loss and the thermal resistance parameters of the IGBT and the diode. Referring to fig. 9 to 11, fig. 9 to 11 show comparison graphs of junction temperatures of switching devices in a PWM-modulated wave-driven frequency converter generated by a PWM modulation method for an elevator frequency converter in the present application and junction temperatures of switching devices in a PWM-modulated wave-driven frequency converter generated by an existing SVPWM and DPWM modulation method, it can be determined that in the method shown in the present application, the temperature of an IGBT chip is 77 ° lower by about 10 ° than that of an existing DPWM, and 8 ° lower by SVPWM, and the temperature of junction temperature is reduced. The overload time can be determined by using the junction temperature threshold, and the reduction of the junction temperature can further improve the overload multiple under the low-speed condition.

So far, the technical solutions of the present invention have been described in connection with the preferred embodiments shown in the drawings, but it is easily understood by those skilled in the art that the scope of the present invention is obviously not limited to these specific embodiments. Equivalent changes or substitutions of related technical features can be made by those skilled in the art without departing from the principle of the invention, and the technical scheme after the changes or substitutions can fall into the protection scope of the invention.