CN105084179A - Elevator system using parallel power converter - Google Patents

Abstract

The invention discloses an elevator system using a parallel power converter; the elevator comprises a no.1 power converter, a no.2 power converter, a controller and a motor; the no.1 power converter and the no.2 power converter are connected in parallel between an AC voltage source and the motor, thus completing power conversion work, and driving a motor rotor to rotate; the controller can control the parallelly connected no.1 power converter and no.2 power converter. A work mode selection module is added in the controller so as to select the work mode according to a motor current order and a power source current order in an elevator running process, i.e., the parallel power converters can simultaneously work, or individually work; a current order distribution module distributes the current order for parallel inverters according to a work mode selection result.

Description

Elevator system using parallel power converters

Technical Field

The present invention relates to an elevator system, and more particularly, to an elevator system using parallel power converters.

Background

As the building floor height continues to increase, the operating speed of elevators needs to be increased correspondingly, while the load capacity also increases progressively, which results in an increasing electrical capacity of the elevator power converter. An increase in electrical capacity results in an increase in current with a constant input/output voltage. The current capacity of a single power converter is a bottleneck for increasing the capacity of the power converter due to factors such as the manufacturing process and cost of the power module. For this reason, having two power converters operating in parallel is a viable solution, as shown in fig. 1.

Although parallel power converters can provide greater current capacity, they also suffer from the following problems:

first, when the parallel power converters are operated simultaneously, the existence of the circulating current cannot be thoroughly avoided. Although the circulation can be controlled by the circulation suppression algorithm, on the one hand, it is impossible to control the circulation to be zero at all times; on the other hand, the circulating current having a frequency higher than the PWM carrier frequency is not suppressed. These unavoidable circulations are not useful for elevator systems, which reduce the efficiency of the power converter. Circulating currents make power converters particularly inefficient when the fundamental magnitude of the current of the motor or power supply is much less than the rated current value of the power converter.

Second, parallel power converters, when operating simultaneously, produce greater electromagnetic interference than a single power converter. On the one hand, operation of two power converters will generate double the harmonic content compared to operation of a single power converter; on the other hand, high frequency circulating currents between the two power converters will result in additional harmonic content.

Third, when the parallel power converters are operated simultaneously, the driving circuit and the protection circuit of the parallel power converters also need to be operated, so that more energy is consumed compared with a single power converter.

The rated current of the parallel power converters is selected according to the maximum current value that may be required for normal operation of the elevator system, which typically occurs when the car is fully loaded and acceleration is up, or when the car is empty and acceleration is down; in other cases, the current required for the operation of the elevator system is small, for example, when the car operates at a constant speed and the load in the car is close to half load; it is obvious that during one run of an elevator system there is often a partial time period during which the current required by the elevator system is sufficient to be supplied by only one power converter; even in certain time periods, the current values required by the elevator system are much smaller than the rated current values of the individual power converters.

In the existing elevator system using the parallel power converters, the working mode of the parallel power converters is not changed in one running process, namely, the parallel power converters are always operated in parallel or are always operated singly until the running process is finished. When the parallel-connection type inverter works in parallel, the time period which is enough for only one power converter is always existed in the operation process; however, during this period, the parallel power converters still simultaneously undertake the power conversion operation, which brings about the above-mentioned problems of unavoidable circulating currents, greater electromagnetic interference and greater energy consumption.

Disclosure of Invention

The technical problem to be solved by the invention is to provide an elevator system using parallel power converters, which can select a working mode according to a motor current instruction and a power supply current instruction.

In order to solve the technical problems, the technical solution of the elevator system using the parallel power converters of the present invention is:

the system comprises a No. 1 power converter, a No. 2 power converter, a controller and a motor; the No. 1 power converter and the No. 2 power converter are connected between the alternating current voltage source and the motor in parallel, so that the power conversion work between the alternating current voltage source and the motor is completed, and a rotor of the motor is driven to rotate; the controller controls the power converter No. 1 and the power converter No. 2 which are connected in parallel; the No. 1 power converter comprises a No. 1 network side reactor, a No. 1 rectifier, a No. 1 inverter and a No. 1 machine side reactor, wherein the No. 1 network side reactor is connected in series between an alternating current voltage source and the alternating current side of the No. 1 rectifier; the No. 1 rectifier converts an alternating current voltage source into No. 1 direct current voltage; the No. 1 inverter converts the No. 1 direct-current voltage into alternating-current voltage; the No. 1 machine side reactor is connected in series between the alternating current side of the No. 1 inverter and the motor; the No. 2 power converter comprises a No. 2 network side reactor, a No. 2 rectifier, a No. 2 inverter and a No. 2 machine side reactor, wherein the No. 2 network side reactor is connected in series between an alternating current voltage source and the alternating current side of the No. 2 rectifier; the No. 2 rectifier converts an alternating current voltage source into No. 2 direct current voltage; the No. 2 inverter converts the No. 2 direct-current voltage into alternating-current voltage; the No. 2 machine side reactor is connected between the alternating current side of the No. 2 inverter and the motor in series; the controller comprises a control module, a speed instruction following module, a rectifying module, a current instruction distribution module, a working mode selection module, a current instruction following module and a PWM module, wherein the control module is responsible for the operation of starting and stopping of the elevator system and generation of a car speed instruction and sends the generated car speed instruction to the speed instruction following module; the speed instruction following module is responsible for following operation of the speed instruction of the lift car, generating a motor current instruction and sending the generated motor current instruction to the working mode selection module and the current instruction distribution module; the rectification module is responsible for generating a current instruction of the No. 1 rectifier and a current instruction of the No. 2 rectifier and generating and operating an output voltage instruction, and sends an instruction signal to the working mode selection module and the PWM module; the working mode selection module calculates the working mode of the parallel power converter according to the motor current instruction, the No. 1 rectifier current instruction and the No. 2 rectifier current instruction, so that the working mode is selected, and a selection result is sent to the current instruction distribution module; the current instruction distribution module divides the motor current instruction according to the working mode, assigns the motor current instruction to a No. 1 inverter and a No. 2 inverter respectively, and sends an instruction signal to the current instruction following module; meanwhile, grid driving enabling signals of the No. 1 power converter and the No. 2 power converter are generated and sent to the PWM module; the current instruction following module is responsible for following operation of a current instruction of the No. 1 inverter and a current instruction of the No. 2 inverter, generates a corresponding output voltage instruction, and sends the generated output voltage instruction to the PWM module; the PWM module is responsible for the operation of the trigger signal of the No. 1 rectifier, the trigger signal of the No. 1 inverter, the trigger signal of the No. 2 rectifier and the trigger signal of the No. 2 inverter.

The method for calculating the working mode of the parallel power converter by the working mode selection module is as follows:

in a first operation period in the running process of the elevator, if the current instruction amplitude of the motor is greater than or equal to a first preset value, setting a mark 1 as true; otherwise, setting the flag 1 to false; and,

in other operation periods in the running process of the elevator, if the current instruction amplitude of the motor is greater than or equal to a second preset value, setting the mark 1 as true; if the motor current instruction value is smaller than the third preset value, setting the mark 1 as false; otherwise, the value of flag 1 is unchanged; and,

in a first operation period in the running process of the elevator, if the sum of the current instruction amplitude of the No. 1 rectifier and the current instruction amplitude of the No. 2 rectifier is greater than or equal to a fourth preset value, setting the sign 2 to be true; otherwise, setting the flag 2 to false; and,

in other operation periods in the running process of the elevator, if the sum of the current instruction amplitude of the No. 1 rectifier and the current instruction amplitude of the No. 2 rectifier is greater than or equal to a fifth preset value, setting the sign 2 to be true; if the sum of the current instruction amplitude of the rectifier No. 1 and the current instruction amplitude of the rectifier No. 2 is smaller than a sixth preset value, setting the mark 2 as false; otherwise, the value of flag 2 is unchanged; and,

selecting a single working mode if and only if the mark 1 and the mark 2 are both false; otherwise, selecting a parallel working mode; and,

the first preset value is less than or equal to the second preset value and greater than or equal to the third preset value; and,

the third preset value is greater than zero; and,

the second preset value is less than or equal to the rated current value of the No. 1 inverter and less than or equal to the rated current value of the No. 2 inverter; and,

the fourth preset value is less than or equal to the fifth preset value and greater than or equal to the sixth preset value; and,

the sixth preset value is greater than zero; and,

the fifth preset value is less than or equal to the rated current value of the No. 1 rectifier and less than or equal to the rated current value of the No. 2 rectifier; and,

the operation logic of the current instruction distribution module is that current instructions are distributed to the No. 1 inverter and the No. 2 inverter according to the following formula:

$I_{\mathrm{ref}1}^k=\frac{1}{2}(I_{\mathrm{ref}}^k+I_{\mathrm{rfes}}^k)$

$I_{\mathrm{ref}2}^k=\frac{1}{2}(I_{\mathrm{ref}}^k-I_{\mathrm{rfes}}^k)$

wherein,andthe current instruction of the No. 1 inverter and the current instruction of the No. 2 inverter in the kth operation period are respectively set;is the motor current command in the kth operation period;the method of (a) is that,

starting from the first operation period to the previous operation period with the first change of the working mode in the running process of the elevator, and if the working mode is parallel operation, then

$I_{\mathrm{refs}}^k=0$

Otherwise, if the working mode is single working and only the No. 1 power converter works, then

$I_{\mathrm{refs}}^k=I_{\mathrm{ref}}^k$

Otherwise, if the working mode is single working and only the No. 2 power converter works, then

$I_{\mathrm{refs}}^k={-I}_{\mathrm{ref}}^k$

If the working mode is changed from single working to parallel working from the ith calculation period, starting from the ith calculation period to the previous calculation period when the working mode is changed again,

<math> <mrow> <msubsup> <mi>I</mi> <mi>refs</mi> <mi>k</mi> </msubsup> <mo>=</mo> <mfenced open='{' close=''> <mtable> <mtr> <mtd> <msubsup> <mi>I</mi> <mi>refs</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>-</mo> <mi>dI</mi> <mo>,</mo> <mrow> <mo>(</mo> <msubsup> <mi>I</mi> <mi>refs</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>-</mo> <mi>dI</mi> <mo>&GreaterEqual;</mo> <mn>0</mn> <mo>)</mo> </mrow> </mtd> </mtr> <mtr> <mtd> <msubsup> <mi>I</mi> <mi>refs</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>+</mo> <mi>dI</mi> <mo>,</mo> <mrow> <mo>(</mo> <msubsup> <mi>I</mi> <mi>refs</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>+</mo> <mi>dI</mi> <mo>&le;</mo> <mn>0</mn> <mo>)</mo> </mrow> </mtd> </mtr> <mtr> <mtd> <mn>0</mn> <mo>,</mo> <mrow> <mo>(</mo> <mo>-</mo> <mi>dI</mi> <mo>&lt;</mo> <msubsup> <mi>I</mi> <mi>refs</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>&lt;</mo> <mi>dI</mi> <mo>)</mo> </mrow> </mtd> </mtr> </mtable> </mfenced> </mrow> </math>

if the work mode is changed from the parallel work to the single work from the j operation period and only the No. 1 power converter works, from the j operation period to the previous operation period when the work mode is changed again,

<math> <mrow> <msubsup> <mi>I</mi> <mi>refs</mi> <mi>k</mi> </msubsup> <mo>=</mo> <mfenced open='{' close=''> <mtable> <mtr> <mtd> <msubsup> <mi>I</mi> <mi>refs</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>-</mo> <mi>dI</mi> <mo>,</mo> <mrow> <mo>(</mo> <msubsup> <mi>I</mi> <mi>refs</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>-</mo> <mi>dI</mi> <mo>&GreaterEqual;</mo> <msubsup> <mi>I</mi> <mi>ref</mi> <mi>k</mi> </msubsup> <mo>)</mo> </mrow> </mtd> </mtr> <mtr> <mtd> <msubsup> <mi>I</mi> <mi>refs</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>+</mo> <mi>dI</mi> <mo>,</mo> <mrow> <mo>(</mo> <msubsup> <mi>I</mi> <mi>refs</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>+</mo> <mi>dI</mi> <mo>&le;</mo> <msubsup> <mi>I</mi> <mi>ref</mi> <mi>k</mi> </msubsup> <mo>)</mo> </mrow> </mtd> </mtr> <mtr> <mtd> <msubsup> <mi>I</mi> <mi>ref</mi> <mi>k</mi> </msubsup> <mo>,</mo> <mrow> <mo>(</mo> <msubsup> <mi>I</mi> <mi>ref</mi> <mi>k</mi> </msubsup> <mo>-</mo> <mi>dI</mi> <mo>&lt;</mo> <msubsup> <mi>I</mi> <mi>refs</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>&lt;</mo> <msubsup> <mi>I</mi> <mi>ref</mi> <mi>k</mi> </msubsup> <mo>+</mo> <mi>dI</mi> <mo>)</mo> </mrow> </mtd> </mtr> </mtable> </mfenced> </mrow> </math>

if the working mode is changed from the parallel operation to the single operation from the l-th operation period and only the No. 2 power converter works, from the l-th operation period to the previous operation period when the working mode is changed again,

<math> <mrow> <msubsup> <mi>I</mi> <mi>refs</mi> <mi>k</mi> </msubsup> <mo>=</mo> <mfenced open='{' close=''> <mtable> <mtr> <mtd> <msubsup> <mi>I</mi> <mi>refs</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>-</mo> <mi>dI</mi> <mo>,</mo> <mrow> <mo>(</mo> <msubsup> <mi>I</mi> <mi>refs</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>-</mo> <mi>dI</mi> <mo>&GreaterEqual;</mo> <msubsup> <mrow> <mo>-</mo> <mi>I</mi> </mrow> <mi>ref</mi> <mi>k</mi> </msubsup> <mo>)</mo> </mrow> </mtd> </mtr> <mtr> <mtd> <msubsup> <mi>I</mi> <mi>refs</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>+</mo> <mi>dI</mi> <mo>,</mo> <mrow> <mo>(</mo> <msubsup> <mi>I</mi> <mi>refs</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>+</mo> <mi>dI</mi> <mo>&le;</mo> <msubsup> <mrow> <mo>-</mo> <mi>I</mi> </mrow> <mi>ref</mi> <mi>k</mi> </msubsup> <mo>)</mo> </mrow> </mtd> </mtr> <mtr> <mtd> <msubsup> <mrow> <mo>-</mo> <mi>I</mi> </mrow> <mi>ref</mi> <mi>k</mi> </msubsup> <mo>,</mo> <mrow> <mo>(</mo> <mo>-</mo> <msubsup> <mi>I</mi> <mi>ref</mi> <mi>k</mi> </msubsup> <mo>-</mo> <mi>dI</mi> <mo>&lt;</mo> <msubsup> <mi>I</mi> <mi>refs</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>&lt;</mo> <msubsup> <mrow> <mo>-</mo> <mi>I</mi> </mrow> <mi>ref</mi> <mi>k</mi> </msubsup> <mo>+</mo> <mi>dI</mi> <mo>)</mo> </mrow> </mtd> </mtr> </mtable> </mfenced> </mrow> </math>

the dI is calculated in such a way that dI is equal to Delta I₁And Δ I₂The larger the size;

wherein if said flag 1 is true, andis greater thanThen Δ I₁Is equal toAnd Δ I_preGreater in between, otherwise Δ I₁Is equal to DeltaI_pre；

If the flag 2 is true, and | CI_refx| is greater than | I_pre5I, then Δ I₂Is equal toAnd Δ I_preGreater in between, otherwise Δ I₂Is equal to DeltaI_pre；

The above CI_refxEqual to CI_ref1And CI_ref2Greater amplitude value between, CI_ref1And CI_ref2The current instruction of the No. 1 rectifier and the current instruction of the No. 2 rectifier are respectively; i is_pre5Is the fifth preset value; u shape_sIs thatVoltage of voltage source, U_refxIs CI_refxAn inverter output voltage command of the targeted power converter; delta I_preIs a constant greater than zero.

Or, the first preset value is smaller than the second preset value and larger than the third preset value.

Or, the fourth preset value is smaller than the fifth preset value and larger than the sixth preset value.

Preferably, the rectifier module consists of a No. 1 direct-current voltage control module, a No. 2 direct-current voltage control module, a No. 1 rectifier current instruction following module and a No. 2 rectifier current instruction following module, wherein the No. 1 direct-current voltage control module and the No. 2 direct-current voltage control module are respectively responsible for controlling a No. 1 direct-current voltage value and a No. 2 direct-current voltage value and generating a phase current amplitude and a phase instruction of the No. 1 rectifier and a phase current amplitude and a phase instruction of the No. 2 rectifier; the No. 1 rectifier current instruction following module and the No. 2 rectifier current instruction following module are respectively responsible for the current instruction following operation of the No. 1 rectifier and the current instruction following operation of the No. 2 rectifier, generate corresponding output voltage instructions and send the generated output voltage instructions to the working mode selection module and the PWM module.

And when the working mode needs to be switched to single working, selecting a power converter which is different from the power converter used in the last single working to be put into operation until the working mode is changed again.

The invention can achieve the technical effects that:

compared with the traditional elevator system using the parallel power converters, the elevator control system is additionally provided with the working mode selection module in the controller, and the working mode selection module is used for selecting the working mode according to the motor current instruction and the power supply current instruction in the elevator running process, namely the parallel power converters work simultaneously or only work singly; and the current instruction distribution module distributes current instructions to the inverters connected in parallel according to the selection result of the working mode.

Therefore, the elevator system based on the invention can switch the working mode during the running of the elevator, i.e. the power converter is allowed to work only singly when the current required by the elevator system is provided by only a single power converter, namely enough time period; during other time periods, the power converters are operated in parallel.

Accordingly, when the power converter operates only singly, the problems as described above can be solved, that is:

first, there is no circulating current; since the switching device of one power converter is always off, a circulating current cannot be generated between the power converters connected in parallel;

second, less electromagnetic interference; since the non-operating power converter does not induce sudden current change, no electromagnetic interference is generated;

third, less energy consumption; when the power converter does not operate, the drive circuit and the protection circuit do not operate, so that energy is not consumed.

Drawings

The invention is described in further detail below with reference to the following figures and detailed description:

fig. 1 is a waveform schematic of a motor side current command for a prior art elevator system using parallel power converters;

fig. 2 is a schematic diagram of an elevator system of the present invention using parallel power converters;

FIG. 3 is a schematic diagram of the controller of the present invention;

FIG. 4 is a schematic diagram of the operating state of the operating mode selection module of the controller of the present invention;

FIG. 5 is a schematic diagram of the operating state of the current command distribution module of the controller of the present invention;

FIG. 6 is a schematic diagram of the operating state of the PWM module of the controller of the present invention;

fig. 7 is a waveform diagram illustrating a motor-side current command according to a second embodiment of the present invention;

fig. 8 is a waveform diagram illustrating a motor-side current command according to a third embodiment of the present invention.

Detailed Description

As shown in fig. 2, the elevator system using the parallel power converter of the present invention includes a No. 1 power converter, a No. 2 power converter, a controller, a motor, a traction sheave, a suspension device, a car, and a counterweight; the No. 1 power converter and the No. 2 power converter are connected in parallel between the alternating current voltage source and the motor to complete power conversion work between the alternating current voltage source and the motor, a rotor of the motor is driven to rotate, the rotor of the motor drives the traction wheel to rotate and drives the suspension device with the two ends connected with the lift car and the counterweight to work; the controller controls the power converter No. 1 and the power converter No. 2 which are connected in parallel, so that the control of an elevator system is realized;

the No. 1 power converter comprises a No. 1 network side reactor, a No. 1 rectifier, a No. 1 inverter and a No. 1 machine side reactor, wherein the No. 1 network side reactor is connected in series between an alternating current voltage source and the alternating current side of the No. 1 rectifier; the No. 1 rectifier converts an alternating current voltage source into No. 1 direct current voltage; the No. 1 inverter converts the No. 1 direct-current voltage into alternating-current voltage; the No. 1 machine side reactor is connected in series between the alternating current side of the No. 1 inverter and the motor;

the No. 2 power converter comprises a No. 2 network side reactor, a No. 2 rectifier, a No. 2 inverter and a No. 2 machine side reactor, wherein the No. 2 network side reactor is connected in series between an alternating current voltage source and the alternating current side of the No. 2 rectifier; the No. 2 rectifier converts an alternating current voltage source into No. 2 direct current voltage; the No. 2 inverter converts the No. 2 direct-current voltage into alternating-current voltage; the No. 2 machine side reactor is connected between the alternating current side of the No. 2 inverter and the motor in series;

as shown in fig. 3, the controller includes a control module, a speed instruction following module, a rectification module, a current instruction allocation module, a working mode selection module, a current instruction following module, and a PWM (pulse width modulation) module, where the control module is responsible for the operation of starting and stopping the elevator system and generating a car speed instruction Vref, and sends the generated car speed instruction Vref to the speed instruction following module; the speed instruction following module is responsible for following operation of the speed instruction of the lift car, generating a motor current instruction Iref and sending the generated motor current instruction Iref to the working mode selection module and the current instruction distribution module;

the rectification module is responsible for generating a current instruction of the No. 1 rectifier and a current instruction of the No. 2 rectifier and generating and operating an output voltage instruction, and sends an instruction signal to the working mode selection module; the current instruction of the No. 1 rectifier and the current instruction of the No. 2 rectifier respectively refer to the current instruction of the No. 1 rectifier and the current instruction of the No. 2 rectifier which are needed for keeping the No. 1 direct-current voltage value and the No. 2 direct-current voltage value;

the working mode selection module calculates a working mode (namely one of a parallel working mode or a single working mode) of the parallel power converter according to the motor current instruction Iref, the No. 1 rectifier current instruction CIref1 and the No. 2 rectifier current instruction CIref2, so that the working mode is selected, and a selection result is sent to the current instruction distribution module; the working mode is one of a parallel working mode or a single working mode, wherein the parallel working mode refers to that the No. 1 power converter and the No. 2 power converter simultaneously undertake power conversion work between the alternating current voltage source and the motor, and the single working mode refers to that only the No. 1 power converter or only the No. 2 power converter undertakes power conversion work between the alternating current voltage source and the motor; the Iref, the CIref2, and the CIref2 are phase current commands;

the operation method of the working mode selection module is as follows:

in a first operation period in the running process of the elevator, if the current instruction amplitude of the motor is greater than or equal to a first preset value, setting a mark 1 as true; otherwise, setting the flag 1 to false; and,

in other operation periods in the running process of the elevator, if the current instruction amplitude of the motor is greater than or equal to a second preset value, setting the mark 1 as true; if the motor current instruction value is smaller than the third preset value, setting the mark 1 as false; otherwise, the value of flag 1 is unchanged; and,

in a first operation period in the running process of the elevator, if the sum of the current instruction amplitude of the No. 1 rectifier and the current instruction amplitude of the No. 2 rectifier is greater than or equal to a fourth preset value, setting the sign 2 to be true; otherwise, setting the flag 2 to false; and,

in other operation periods in the running process of the elevator, if the sum of the current instruction amplitude of the No. 1 rectifier and the current instruction amplitude of the No. 2 rectifier is greater than or equal to a fifth preset value, setting the sign 2 to be true; if the sum of the current instruction amplitude of the rectifier No. 1 and the current instruction amplitude of the rectifier No. 2 is smaller than a sixth preset value, setting the mark 2 as false; otherwise, the value of flag 2 is unchanged; and,

selecting a single working mode if and only if the mark 1 and the mark 2 are both false; otherwise, selecting a parallel working mode; and,

the first preset value is less than or equal to the second preset value and greater than or equal to the third preset value; and,

the third preset value is greater than zero; and,

the second preset value is less than or equal to the rated current value of the No. 1 inverter and less than or equal to the rated current value of the No. 2 inverter; and,

the fourth preset value is less than or equal to the fifth preset value and greater than or equal to the sixth preset value; and,

the sixth preset value is greater than zero; and,

the fifth preset value is less than or equal to the rated current value of the No. 1 rectifier and less than or equal to the rated current value of the No. 2 rectifier; and,

the operation logic of the current instruction distribution module is that current instructions are distributed to the No. 1 inverter and the No. 2 inverter according to the following formula:

$I_{\mathrm{ref}1}^k=\frac{1}{2}(I_{\mathrm{ref}}^k+I_{\mathrm{rfes}}^k)$

$I_{\mathrm{ref}2}^k=\frac{1}{2}(I_{\mathrm{ref}}^k-I_{\mathrm{rfes}}^k)$

wherein,andthe current instruction of the No. 1 inverter and the current instruction of the No. 2 inverter in the kth operation period are respectively set;is the motor current command in the kth operation period;the method of (a) is that,

starting from the first operation period to the previous operation period with the first change of the working mode in the running process of the elevator, and if the working mode is parallel operation, then

$I_{\mathrm{refs}}^k=0$

Otherwise, if the working mode is single working and only the No. 1 power converter works, then

$I_{\mathrm{refs}}^k=I_{\mathrm{ref}}^k$

Otherwise, if the working mode is single working and only the No. 2 power converter works, then

$I_{\mathrm{refs}}^k={-I}_{\mathrm{ref}}^k$

If the working mode is changed from single working to parallel working from the ith calculation period, starting from the ith calculation period to the previous calculation period when the working mode is changed again,

<math> <mrow> <msubsup> <mi>I</mi> <mi>refs</mi> <mi>k</mi> </msubsup> <mo>=</mo> <mfenced open='{' close=''> <mtable> <mtr> <mtd> <msubsup> <mi>I</mi> <mi>refs</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>-</mo> <mi>dI</mi> <mo>,</mo> <mrow> <mo>(</mo> <msubsup> <mi>I</mi> <mi>refs</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>-</mo> <mi>dI</mi> <mo>&GreaterEqual;</mo> <mn>0</mn> <mo>)</mo> </mrow> </mtd> </mtr> <mtr> <mtd> <msubsup> <mi>I</mi> <mi>refs</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>+</mo> <mi>dI</mi> <mo>,</mo> <mrow> <mo>(</mo> <msubsup> <mi>I</mi> <mi>refs</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>+</mo> <mi>dI</mi> <mo>&le;</mo> <mn>0</mn> <mo>)</mo> </mrow> </mtd> </mtr> <mtr> <mtd> <mn>0</mn> <mo>,</mo> <mrow> <mo>(</mo> <mo>-</mo> <mi>dI</mi> <mo>&lt;</mo> <msubsup> <mi>I</mi> <mi>refs</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>&lt;</mo> <mi>dI</mi> <mo>)</mo> </mrow> </mtd> </mtr> </mtable> </mfenced> </mrow> </math>

if the work mode is changed from the parallel work to the single work from the j operation period and only the No. 1 power converter works, from the j operation period to the previous operation period when the work mode is changed again,

<math> <mrow> <msubsup> <mi>I</mi> <mi>refs</mi> <mi>k</mi> </msubsup> <mo>=</mo> <mfenced open='{' close=''> <mtable> <mtr> <mtd> <msubsup> <mi>I</mi> <mi>refs</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>-</mo> <mi>dI</mi> <mo>,</mo> <mrow> <mo>(</mo> <msubsup> <mi>I</mi> <mi>refs</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>-</mo> <mi>dI</mi> <mo>&GreaterEqual;</mo> <msubsup> <mi>I</mi> <mi>ref</mi> <mi>k</mi> </msubsup> <mo>)</mo> </mrow> </mtd> </mtr> <mtr> <mtd> <msubsup> <mi>I</mi> <mi>refs</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>+</mo> <mi>dI</mi> <mo>,</mo> <mrow> <mo>(</mo> <msubsup> <mi>I</mi> <mi>refs</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>+</mo> <mi>dI</mi> <mo>&le;</mo> <msubsup> <mi>I</mi> <mi>ref</mi> <mi>k</mi> </msubsup> <mo>)</mo> </mrow> </mtd> </mtr> <mtr> <mtd> <msubsup> <mi>I</mi> <mi>ref</mi> <mi>k</mi> </msubsup> <mo>,</mo> <mrow> <mo>(</mo> <msubsup> <mi>I</mi> <mi>ref</mi> <mi>k</mi> </msubsup> <mo>-</mo> <mi>dI</mi> <mo>&lt;</mo> <msubsup> <mi>I</mi> <mi>refs</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>&lt;</mo> <msubsup> <mi>I</mi> <mi>ref</mi> <mi>k</mi> </msubsup> <mo>+</mo> <mi>dI</mi> <mo>)</mo> </mrow> </mtd> </mtr> </mtable> </mfenced> </mrow> </math>

if the working mode is changed from the parallel operation to the single operation from the l-th operation period and only the No. 2 power converter works, from the l-th operation period to the previous operation period when the working mode is changed again,

<math> <mrow> <msubsup> <mi>I</mi> <mi>refs</mi> <mi>k</mi> </msubsup> <mo>=</mo> <mfenced open='{' close=''> <mtable> <mtr> <mtd> <msubsup> <mi>I</mi> <mi>refs</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>-</mo> <mi>dI</mi> <mo>,</mo> <mrow> <mo>(</mo> <msubsup> <mi>I</mi> <mi>refs</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>-</mo> <mi>dI</mi> <mo>&GreaterEqual;</mo> <msubsup> <mrow> <mo>-</mo> <mi>I</mi> </mrow> <mi>ref</mi> <mi>k</mi> </msubsup> <mo>)</mo> </mrow> </mtd> </mtr> <mtr> <mtd> <msubsup> <mi>I</mi> <mi>refs</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>+</mo> <mi>dI</mi> <mo>,</mo> <mrow> <mo>(</mo> <msubsup> <mi>I</mi> <mi>refs</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>+</mo> <mi>dI</mi> <mo>&le;</mo> <msubsup> <mrow> <mo>-</mo> <mi>I</mi> </mrow> <mi>ref</mi> <mi>k</mi> </msubsup> <mo>)</mo> </mrow> </mtd> </mtr> <mtr> <mtd> <msubsup> <mrow> <mo>-</mo> <mi>I</mi> </mrow> <mi>ref</mi> <mi>k</mi> </msubsup> <mo>,</mo> <mrow> <mo>(</mo> <mo>-</mo> <msubsup> <mi>I</mi> <mi>ref</mi> <mi>k</mi> </msubsup> <mo>-</mo> <mi>dI</mi> <mo>&lt;</mo> <msubsup> <mi>I</mi> <mi>refs</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>&lt;</mo> <msubsup> <mrow> <mo>-</mo> <mi>I</mi> </mrow> <mi>ref</mi> <mi>k</mi> </msubsup> <mo>+</mo> <mi>dI</mi> <mo>)</mo> </mrow> </mtd> </mtr> </mtable> </mfenced> </mrow> </math>

the dI is calculated in such a way that dI is equal to Delta I₁And Δ I₂The larger the size;

wherein if said flag 1 is true, andis greater thanThen Δ I₁Is equal toAnd Δ I_preGreater in between, otherwise Δ I₁Is equal to DeltaI_pre；

If the flag 2 is true, and | CI_refx| is greater than | I_pre5I, then Δ I₂Is equal toAnd Δ I_preThe larger of the two groups is,otherwise Δ I₂Is equal to DeltaI_pre；

The above CI_refxEqual to CI_ref1And CI_ref2Greater amplitude value between, CI_ref1And CI_ref2The current instruction of the No. 1 rectifier and the current instruction of the No. 2 rectifier are respectively; i is_pre5Is the fifth preset value; u shape_sIs the voltage of said voltage source, U_refxIs CI_refxAn inverter output voltage command of the targeted power converter; delta I_preIs a constant greater than zero;

the current instruction distribution module divides the motor current instruction into Iref1 and Iref2 according to the working mode, assigns the Iref1 and the Iref2 to the inverter No. 1 and the inverter No. 2 respectively, and sends an instruction signal to the current instruction following module; meanwhile, grid driving enable signals EN1 and EN2 of the No. 1 power converter and the No. 2 power converter are generated and sent to the PWM module;

the current instruction following module is responsible for following operation of a current instruction Iref1 of the inverter No. 1 and a current instruction Iref2 of the inverter No. 2, generates corresponding output voltage instructions Uref1 and Uref2, and sends the generated output voltage instructions Uref1 and Uref2 to the PWM module;

the rectifier module consists of a No. 1 direct-current voltage control module, a No. 2 direct-current voltage control module, a No. 1 rectifier current instruction following module and a No. 2 rectifier current instruction following module, wherein the No. 1 direct-current voltage control module and the No. 2 direct-current voltage control module are respectively responsible for controlling the No. 1 direct-current voltage value and the No. 2 direct-current voltage value and generating a phase current amplitude and a phase instruction of the No. 1 rectifier and a phase current amplitude and a phase instruction of the No. 2 rectifier; the No. 1 rectifier current instruction following module and the No. 2 rectifier current instruction following module are respectively responsible for the current instruction following operation of the No. 1 rectifier and the current instruction following operation of the No. 2 rectifier, generate corresponding output voltage instructions CUref1 and CUref2, and send the generated output voltage instructions CUref1 and CUref2 to the PWM module;

the PWM module is responsible for the operation of the rectifier trigger signal TRconv1 # 1, the inverter trigger signal TRinv1 # 1, the rectifier trigger signal TRconv2 # 2 and the inverter trigger signal TRinv2 # 2.

As shown in fig. 4, the operation mode selection module of the controller has two states in common:

(1) a default state of "stop", and

(2) the state "driving";

if the elevator is started, the state is changed from 'stop' to 'running'; if the elevator stops, the state changes from "traveling" to "stopped". And the process from the elevator entering the running state to the elevator exiting the running state is an elevator running process.

The tasks that each state needs to perform are explained separately below:

in the "stop" state: no task is performed;

the "driving" state includes two sub-states:

(a) default state "first operation cycle", and

(b) state "other operation cycle";

if the value of the variable flgT is more than or equal to 2, the state is changed from the first operation period to other operation periods; the variable flgT is positioned in a non-stack area in the memory;

when entering the state "first operation cycle", the following steps are sequentially executed:

1. setting a variable flgT to 0;

2. if the Iref is larger than or equal to Ipre1, setting flg1 as TRUE; otherwise, setting the flg1 as FALSE;

3. calculating the sum of the absolute values of CIref1 and CIref2, and assigning the result to a variable CIref;

4. if CIref is greater than or equal to Ipre4, setting flg2 as TRUE; otherwise, set flg2 to FALSE.

When the state is 'first operation cycle', the following steps are executed:

the value of the variable flgT is increased by 1.

When the state is in the 'other operation period', the following steps are sequentially executed:

1. if the Iref is larger than or equal to Ipre2, setting flg1 as TRUE; otherwise, if the Iref is smaller than the Ipre3, setting the flg1 as FALSE; otherwise the value of flg1 remains unchanged;

2. calculating the sum of the absolute values of CIref1 and CIref2, and assigning the result to a variable CIref;

3. if CIref is greater than or equal to Ipre5, setting flg2 as TRUE; otherwise, if CIref is less than Ipre6, set flg2 to FALSE, otherwise the value of flg2 remains unchanged.

The TRUE and FALSE are predefined constants that are not equal to each other.

The first preset value is Ipre1, the second preset value is Ipre2, the third preset value is Ipre3, Ipre2 is greater than or equal to Ipre1, and Ipre3 is less than or equal to Ipre 1.

The Ipre4 is a fourth preset value, Ipre5 is a fifth preset value, 5, Ipre6 is a sixth preset value, Ipre5 is greater than or equal to Ipre4, and Ipre6 is less than or equal to Ipre 4.

Finally, in the state "driving", it is necessary to carry out:

if both flg1 and flg2 equal FALSE, then mode is assigned to ONLY 1; otherwise, mode is assigned to BOTH.

The BOTH, ONLY1 are predefined constants that are not equal to each other.

As shown in fig. 5, the current command distribution module of the controller has two states in common:

(1) a default state of "stop", and

(2) the state "driving";

if the elevator is started, the state is changed from 'stop' to 'running'; if the elevator stops, the state is changed from 'running' to 'stopping';

the tasks that each state needs to perform are explained separately below:

when the system is in a stop state, the following steps are sequentially executed:

1. iref1 is set to 0; iref2 is set to 0;

2. setting EN1 to FALSE; EN2 is set to FALSE.

While the "drive" state contains four sub-states:

(a) the default state "initial", and

(b) the state "number 1 only", and

(c) the state "No. 2 only", and

(d) state "parallel operation"

If the mode value changes, the state exits from "initial"; and if mode becomes ONLY1, the state becomes "No. 1 ONLY"; if mode changes to ONLY2, the state changes to "No. 2 ONLY"; if the mode is changed into BOTH, the state is changed into parallel operation; the NONE, BOTH, ONLY1, ONLY2 are predefined constants that are not equal to each other;

in the state "initial", it is performed:

if mode equals BOTH, Irefs is assigned to 0;

otherwise if mode equals ONLY1, then Irefs is assigned as Iref;

otherwise if mode equals ONLY2, Irefs is assigned as Iref.

The Irefs is a difference between inverter current command No. 1 and inverter current command No. 2.

In the state "number 1 only", it is performed:

if Irefs is larger than or equal to Iref + dI, reducing the value of Irefs by dI;

otherwise, if the Irefs is less than or equal to Iref-dI, increasing the value of the Irefs by dI;

otherwise Iref is assigned to Irefs.

In the state "number 2 only", it is performed:

if Irefs is larger than or equal to-Iref + dI, reducing the value of Irefs by dI;

otherwise, if the Irefs is less than or equal to-Iref-dI, increasing the value of the Irefs by dI;

otherwise-Iref is assigned to Irefs.

When the system is in the state of parallel operation, the following steps are carried out:

if Irefs is larger than or equal to dI, reducing the value of Irefs by dI;

otherwise, if the Irefs is less than or equal to dI, increasing the value of the Irefs by dI;

otherwise Irefs is assigned a value of 0.

Finally, in the state "driving", it is necessary to perform in sequence:

1. calculating the value of the variable dI;

2. calculating Iref1, i.e. Iref1 ═ 0.5 × (Iref + Irefs);

3. calculating Iref2, i.e. Iref2 ═ 0.5 × (Iref-Irefs);

4. if mode equals BOTH, then BOTH EN1 and EN2 are assigned TRUE;

otherwise if mode equals ONLY1 and Iref2 equals 0, then EN1 is assigned TRUE and EN2 is assigned FALSE;

otherwise if mode equals ONLY2 and Iref1 equals 0, then EN1 is assigned FALSE and EN2 is assigned TRUE;

dI is calculated by the method that dI is equal to DeltaI₁And Δ I₂The larger the size;

whereinIf flg1 is equal to TRUE and the absolute value of Iref in the current calculation cycle is greater than the absolute value of Iref in the previous calculation cycle, Δ I₁Equal to the absolute value of the difference between Iref of the current operation period and Iref of the previous operation period and_pre"greater therebetween, otherwise Δ I₁Is equal to DeltaI_pre；

If flg2 equals TRUE, and | CI_refxIf | is greater than | Ipre5|, then Δ I₂Is equal toAnd Δ I_preGreater in between, otherwise Δ I₂Is equal to DeltaI_pre；

The above CI_refxEqual to the greater of the absolute values between CIref1 and CIref 2; u shape_sIs the voltage of an AC voltage source, U_refxIs CI_refxAn inverter output voltage command of the targeted power converter; delta I_preIs a constant greater than zero.

The NONE, BOTH, ONLY1, ONLY2 are predefined constants that are not equal to each other.

As shown in fig. 6, the PWM module of the controller is composed of two orthogonal intervals, namely, power converter No. 1 and power converter No. 2, which means that states in different orthogonal intervals are independent of each other;

there are two states in common in the section "power converter No. 1":

(1) a default state of "disabled", an

(2) State "enable";

if EN1 equals TRUE, the status changes from "disabled" to "enabled"; if EN1 equals FALSE, the state changes from "ENABLE" to "DEABLE";

the tasks that each state needs to perform are explained separately below:

in the "disabled" state, it is performed:

the trigger commands of TRconv1, namely all the switching devices of the No. 1 rectifier are set to be OFF, namely turned OFF;

the trigger command of the TRinv1, namely all the switching devices of the No. 1 inverter, is set to OFF, namely turned OFF.

The OFF is a predefined constant whose value represents the switching device turn-OFF logic.

When the state is in the 'enabling' state, the following steps are executed:

calculating TRconv1 according to the CUref 1;

TRinv1 was calculated from Uref 1.

The above task, namely, generating the trigger logic of the switching device of the power converter according to the voltage command, is implemented by a method that belongs to the well-known technology in the field of power converters, and is not described herein again.

The case of the section "power converter No. 2" is similar to the case of the section "power converter No. 1", and is not described herein again.

In another embodiment of the present invention, the constraint conditions for Ipre1, Ipre2, Ipre3, Ipre4, Ipre5, and Ipre6 are different from those of the first embodiment, and the constraint conditions are completely the same in other aspects; in a second embodiment, the Ipre3 is smaller than Ipre 1; also, the Ipre6 is smaller than Ipre 4;

fig. 7 is a waveform diagram of the motor-side current command with a changed operation mode, which shows a motor current command Iref, an inverter current command Iref1 No. 1, and an inverter current command Iref2 No. 2, respectively; it can be seen that the operating mode goes through ONLY1, BOTH, ONLY1 in sequence. Moreover, the current instruction threshold value for switching from single work to parallel work is larger than the current instruction threshold value for switching from parallel work to single work, and the current instruction fluctuation in the difference interval cannot cause the switching of the working modes; moreover, when the operation mode is switched, the current command of inverter No. 1 and the current command of inverter No. 2 gradually transit to the target value, and therefore, abrupt changes in the current commands are suppressed.

Compared to the prior art motor side current command waveform for elevator systems using parallel power converters as shown in fig. 1, it can be seen that whenever the motor current command is taken in half by inverter No. 1 and inverter No. 2, respectively.

The invention can also adopt a third implementation mode, compared with the second implementation mode, the operation logic of the working mode selection module is different, and other aspects are completely consistent;

the difference between the third embodiment and the operation mode selection module of the second embodiment is that when the state "driving" is performed, the following steps are sequentially performed:

1. in the case where both flg1 and flg2 equal FALSE:

if the variable Zmode equals ONLY1, then mode is assigned to ONLY 2;

otherwise, assigning mode as ONLY 1;

in the case where both flg1 and flg2 are not equal to FALSE:

assigning mode as BOTH;

2. if mode changes and the current value is ONLY1 or ONLY2, then Zmode is assigned as mode.

The Zmode is the power converter code used when the last single unit was run.

As shown in fig. 8, when the operation mode is single operation, the inverter No. 1 and the inverter No. 2 alternately receive a motor current command.

According to the invention, a current instruction distribution module, a rectification module and a PWM module of a controller drive a No. 1 power converter and a No. 2 power converter which are connected in parallel to each other to work according to a selection result of a working mode selection module.

It should be noted that the present invention does not intend to ensure that the parallel power converters are in a single operation mode for all "provided by a single power converter, i.e. for a sufficient period of time"; the object of the invention is to make the parallel power converter in a single operation mode during a part of such a period.

Although switching the operation mode during the operation of the elevator increases the complexity of the operation of the power converter, thereby possibly reducing the reliability of the elevator system, the operation mode selection module according to the invention allows the use of different current thresholds for the determination conditions for switching between the two operation modes in different directions, i.e. the current threshold for switching from single operation to parallel operation may be greater than the current threshold for switching from parallel operation to single operation, thereby avoiding the too frequent switching of the operation modes. Further, the elevator system based on the invention can switch the working mode only when the acceleration command of the elevator car changes in one running process.

In consideration of current fluctuation which may occur when the working mode is switched, the current instruction distribution module calculates the difference instruction of the two paths of current firstly when dividing the current instruction, and then calculates the two paths of current instructions according to the current difference instruction and by combining the motor current instruction. The method has the advantages that the following two aims can be simultaneously achieved: firstly, the sum of the two paths of current instructions is always equal to the motor current instruction from the speed instruction following module, and no additional fluctuation is introduced due to the switching of the working mode; secondly, the current instruction distribution module enables the difference instruction of the two paths of current to gradually change along with time, so that the two paths of current instructions gradually change just after the working modes are switched, and severe fluctuation of the two paths of inverter current is avoided. In addition, the current instruction distribution module sets a lower limit for the change rate of the two paths of current difference instructions, so that the two paths of current instructions can be ensured to gradually change and cannot exceed the rated current range of the power converter.

The invention also uses different power converters to work in turn when entering a single working mode each time; the parallel power converters are enabled to bear the same power cycle times, so that the overlarge fatigue damage degree among the parallel power converters is avoided, and the total service life of the parallel power converters is prolonged.

Claims (6)

1. An elevator system using parallel power converters, characterized by: the system comprises a No. 1 power converter, a No. 2 power converter, a controller and a motor; the No. 1 power converter and the No. 2 power converter are connected between the alternating current voltage source and the motor in parallel, so that the power conversion work between the alternating current voltage source and the motor is completed, and a rotor of the motor is driven to rotate; the controller controls the power converter No. 1 and the power converter No. 2 which are connected in parallel;

the No. 1 power converter comprises a No. 1 network side reactor, a No. 1 rectifier, a No. 1 inverter and a No. 1 machine side reactor, wherein the No. 1 network side reactor is connected in series between an alternating current voltage source and the alternating current side of the No. 1 rectifier; the No. 1 rectifier converts an alternating current voltage source into No. 1 direct current voltage; the No. 1 inverter converts the No. 1 direct-current voltage into alternating-current voltage; the No. 1 machine side reactor is connected in series between the alternating current side of the No. 1 inverter and the motor;

the No. 2 power converter comprises a No. 2 network side reactor, a No. 2 rectifier, a No. 2 inverter and a No. 2 machine side reactor, wherein the No. 2 network side reactor is connected in series between an alternating current voltage source and the alternating current side of the No. 2 rectifier; the No. 2 rectifier converts an alternating current voltage source into No. 2 direct current voltage; the No. 2 inverter converts the No. 2 direct-current voltage into alternating-current voltage; the No. 2 machine side reactor is connected between the alternating current side of the No. 2 inverter and the motor in series;

the controller comprises a control module, a speed instruction following module, a rectifying module, a current instruction distribution module, a working mode selection module, a current instruction following module and a PWM module, wherein the control module is responsible for the operation of starting and stopping of the elevator system and generation of a car speed instruction and sends the generated car speed instruction to the speed instruction following module; the speed instruction following module is responsible for following operation of the speed instruction of the lift car, generating a motor current instruction and sending the generated motor current instruction to the working mode selection module and the current instruction distribution module;

the rectification module is responsible for generating a current instruction of the No. 1 rectifier and a current instruction of the No. 2 rectifier and generating and operating an output voltage instruction, and sends an instruction signal to the working mode selection module and the PWM module;

the working mode selection module calculates the working mode of the parallel power converter according to the motor current instruction, the No. 1 rectifier current instruction and the No. 2 rectifier current instruction, so that the working mode is selected, and a selection result is sent to the current instruction distribution module;

the current instruction distribution module divides the motor current instruction according to the working mode, assigns the motor current instruction to a No. 1 inverter and a No. 2 inverter respectively, and sends an instruction signal to the current instruction following module; meanwhile, grid driving enabling signals of the No. 1 power converter and the No. 2 power converter are generated and sent to the PWM module;

the current instruction following module is responsible for following operation of a current instruction of the No. 1 inverter and a current instruction of the No. 2 inverter, generates a corresponding output voltage instruction, and sends the generated output voltage instruction to the PWM module;

the PWM module is responsible for the operation of the trigger signal of the No. 1 rectifier, the trigger signal of the No. 1 inverter, the trigger signal of the No. 2 rectifier and the trigger signal of the No. 2 inverter.

2. The elevator system using parallel power converters of claim 1, wherein: the method for calculating the working mode of the parallel power converter by the working mode selection module is as follows:

in a first operation period in the running process of the elevator, if the current instruction amplitude of the motor is greater than or equal to a first preset value, setting a mark 1 as true; otherwise, setting the flag 1 to false; and,

in other operation periods in the running process of the elevator, if the current instruction amplitude of the motor is greater than or equal to a second preset value, setting the mark 1 as true; if the motor current instruction value is smaller than the third preset value, setting the mark 1 as false; otherwise, the value of flag 1 is unchanged; and,

in a first operation period in the running process of the elevator, if the sum of the current instruction amplitude of the No. 1 rectifier and the current instruction amplitude of the No. 2 rectifier is greater than or equal to a fourth preset value, setting the sign 2 to be true; otherwise, setting the flag 2 to false; and,

in other operation periods in the running process of the elevator, if the sum of the current instruction amplitude of the No. 1 rectifier and the current instruction amplitude of the No. 2 rectifier is greater than or equal to a fifth preset value, setting the sign 2 to be true; if the sum of the current instruction amplitude of the rectifier No. 1 and the current instruction amplitude of the rectifier No. 2 is smaller than a sixth preset value, setting the mark 2 as false; otherwise, the value of flag 2 is unchanged; and,

selecting a single working mode if and only if the mark 1 and the mark 2 are both false; otherwise, selecting a parallel working mode; and,

the first preset value is less than or equal to the second preset value and greater than or equal to the third preset value; and,

the third preset value is greater than zero; and,

the second preset value is less than or equal to the rated current value of the No. 1 inverter and less than or equal to the rated current value of the No. 2 inverter; and,

the fourth preset value is less than or equal to the fifth preset value and greater than or equal to the sixth preset value; and,

the sixth preset value is greater than zero; and,

the fifth preset value is less than or equal to the rated current value of the No. 1 rectifier and less than or equal to the rated current value of the No. 2 rectifier; and,

the operation logic of the current instruction distribution module is that current instructions are distributed to the No. 1 inverter and the No. 2 inverter according to the following formula:

$I_{\mathrm{ref}1}^k=\frac{1}{2}(I_{\mathrm{ref}}^k+I_{\mathrm{rfes}}^k)$

$I_{\mathrm{ref}2}^k=\frac{1}{2}(I_{\mathrm{ref}}^k-I_{\mathrm{rfes}}^k)$

wherein,andthe current instruction of the No. 1 inverter and the current instruction of the No. 2 inverter in the kth operation period are respectively set;is the motor current command in the kth operation period;the method of (a) is that,

starting from the first operation period to the previous operation period with the first change of the working mode in the running process of the elevator, and if the working mode is parallel operation, then

$I_{\mathrm{refs}}^k=0$

Otherwise, if the working mode is single working and only the No. 1 power converter works, then

$I_{\mathrm{refs}}^k=I_{\mathrm{ref}}^k$

Otherwise, if the working mode is single working and only the No. 2 power converter works, then

$I_{\mathrm{refs}}^k={-I}_{\mathrm{ref}}^k$

If the working mode is changed from single working to parallel working from the ith calculation period, starting from the ith calculation period to the previous calculation period when the working mode is changed again,

<math> <mrow> <msubsup> <mi>I</mi> <mi>refs</mi> <mi>k</mi> </msubsup> <mo>=</mo> <mfenced open='{' close=''> <mtable> <mtr> <mtd> <msubsup> <mi>I</mi> <mi>refs</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>-</mo> <mi>dI</mi> <mo>,</mo> <mrow> <mo>(</mo> <msubsup> <mi>I</mi> <mi>refs</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>-</mo> <mi>dI</mi> <mo>&GreaterEqual;</mo> <mn>0</mn> <mo>)</mo> </mrow> </mtd> </mtr> <mtr> <mtd> <msubsup> <mi>I</mi> <mi>refs</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>+</mo> <mi>dI</mi> <mo>,</mo> <mrow> <mo>(</mo> <msubsup> <mi>I</mi> <mi>refs</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>+</mo> <mi>dI</mi> <mo>&le;</mo> <mn>0</mn> <mo>)</mo> </mrow> </mtd> </mtr> <mtr> <mtd> <mn>0</mn> <mo>,</mo> <mrow> <mo>(</mo> <mo>-</mo> <mi>dI</mi> <mo>&lt;</mo> <msubsup> <mi>I</mi> <mi>refs</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>&lt;</mo> <mi>dI</mi> <mo>)</mo> </mrow> </mtd> </mtr> </mtable> </mfenced> </mrow> </math>

if the work mode is changed from the parallel work to the single work from the j operation period and only the No. 1 power converter works, from the j operation period to the previous operation period when the work mode is changed again,

<math> <mrow> <msubsup> <mi>I</mi> <mi>refs</mi> <mi>k</mi> </msubsup> <mo>=</mo> <mfenced open='{' close=''> <mtable> <mtr> <mtd> <msubsup> <mi>I</mi> <mi>refs</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>-</mo> <mi>dI</mi> <mo>,</mo> <mrow> <mo>(</mo> <msubsup> <mi>I</mi> <mi>refs</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>-</mo> <mi>dI</mi> <mo>&GreaterEqual;</mo> <msubsup> <mi>I</mi> <mi>ref</mi> <mi>k</mi> </msubsup> <mo>)</mo> </mrow> </mtd> </mtr> <mtr> <mtd> <msubsup> <mi>I</mi> <mi>refs</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>+</mo> <mi>dI</mi> <mo>,</mo> <mrow> <mo>(</mo> <msubsup> <mi>I</mi> <mi>refs</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>+</mo> <mi>dI</mi> <mo>&le;</mo> <msubsup> <mi>I</mi> <mi>ref</mi> <mi>k</mi> </msubsup> <mo>)</mo> </mrow> </mtd> </mtr> <mtr> <mtd> <msubsup> <mi>I</mi> <mi>ref</mi> <mi>k</mi> </msubsup> <mo>,</mo> <mrow> <mo>(</mo> <msubsup> <mi>I</mi> <mi>ref</mi> <mi>k</mi> </msubsup> <mo>-</mo> <mi>dI</mi> <mo>&lt;</mo> <msubsup> <mi>I</mi> <mi>refs</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>&lt;</mo> <msubsup> <mi>I</mi> <mi>ref</mi> <mi>k</mi> </msubsup> <mo>+</mo> <mi>dI</mi> <mo>)</mo> </mrow> </mtd> </mtr> </mtable> </mfenced> </mrow> </math>

if the working mode is changed from the parallel operation to the single operation from the l-th operation period and only the No. 2 power converter works, from the l-th operation period to the previous operation period when the working mode is changed again,

<math> <mrow> <msubsup> <mi>I</mi> <mi>refs</mi> <mi>k</mi> </msubsup> <mo>=</mo> <mfenced open='{' close=''> <mtable> <mtr> <mtd> <msubsup> <mi>I</mi> <mi>refs</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>-</mo> <mi>dI</mi> <mo>,</mo> <mrow> <mo>(</mo> <msubsup> <mi>I</mi> <mi>refs</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>-</mo> <mi>dI</mi> <mo>&GreaterEqual;</mo> <msubsup> <mrow> <mo>-</mo> <mi>I</mi> </mrow> <mi>ref</mi> <mi>k</mi> </msubsup> <mo>)</mo> </mrow> </mtd> </mtr> <mtr> <mtd> <msubsup> <mi>I</mi> <mi>refs</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>+</mo> <mi>dI</mi> <mo>,</mo> <mrow> <mo>(</mo> <msubsup> <mi>I</mi> <mi>refs</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>+</mo> <mi>dI</mi> <mo>&le;</mo> <msubsup> <mrow> <mo>-</mo> <mi>I</mi> </mrow> <mi>ref</mi> <mi>k</mi> </msubsup> <mo>)</mo> </mrow> </mtd> </mtr> <mtr> <mtd> <msubsup> <mrow> <mo>-</mo> <mi>I</mi> </mrow> <mi>ref</mi> <mi>k</mi> </msubsup> <mo>,</mo> <mrow> <mo>(</mo> <mo>-</mo> <msubsup> <mi>I</mi> <mi>ref</mi> <mi>k</mi> </msubsup> <mo>-</mo> <mi>dI</mi> <mo>&lt;</mo> <msubsup> <mi>I</mi> <mi>refs</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>&lt;</mo> <msubsup> <mrow> <mo>-</mo> <mi>I</mi> </mrow> <mi>ref</mi> <mi>k</mi> </msubsup> <mo>+</mo> <mi>dI</mi> <mo>)</mo> </mrow> </mtd> </mtr> </mtable> </mfenced> </mrow> </math>

the dI is calculated in such a way that dI is equal to Delta I₁And Δ I₂The larger the size;

wherein if said flag 1 is true, andis greater thanThen Δ I₁Is equal toAnd Δ I_preGreater in between, otherwise Δ I₁Is equal to DeltaI_pre；

If the flag 2 is true, and | CI_refxI bigAt | I_pre5I, then Δ I₂Is equal toAnd Δ I_preGreater in between, otherwise Δ I₂Is equal to DeltaI_pre；

The above CI_refxEqual to CI_ref1And CI_ref2Greater amplitude value between, CI_ref1And CI_ref2The current instruction of the No. 1 rectifier and the current instruction of the No. 2 rectifier are respectively; i is_pre5Is the fifth preset value; u shape_sIs the voltage of said voltage source, U_refxIs CI_refxAn inverter output voltage command of the targeted power converter; delta I_preIs a constant greater than zero.

3. The elevator system using parallel power converters of claim 2, wherein: the first preset value is smaller than the second preset value and larger than the third preset value.

4. The elevator system using parallel power converters of claim 2, wherein: the fourth preset value is smaller than the fifth preset value and larger than the sixth preset value.

5. The elevator system using parallel power converters of claim 1, wherein: the rectifier module consists of a No. 1 direct-current voltage control module, a No. 2 direct-current voltage control module, a No. 1 rectifier current instruction following module and a No. 2 rectifier current instruction following module, wherein the No. 1 direct-current voltage control module and the No. 2 direct-current voltage control module are respectively responsible for controlling the No. 1 direct-current voltage value and the No. 2 direct-current voltage value and generating a phase current amplitude and a phase instruction of the No. 1 rectifier and a phase current amplitude and a phase instruction of the No. 2 rectifier; the No. 1 rectifier current instruction following module and the No. 2 rectifier current instruction following module are respectively responsible for the current instruction following operation of the No. 1 rectifier and the current instruction following operation of the No. 2 rectifier, generate corresponding output voltage instructions and send the generated output voltage instructions to the working mode selection module and the PWM module.

6. The elevator system using parallel power converters of claim 1, wherein: and when the working mode needs to be switched to single working, selecting a power converter which is different from the power converter used in the last single working to be put into operation until the working mode is changed again.