Motor system based on single power circuit and control method thereof

Abstract

The present disclosure provides a kind of motor system based on single power circuit and its control method, it is related to motor system technical field.The circuit includes: three-phase motor and multiple power output units, each phase of three-phase motor is connected to different power output unit respectively;Wherein, each power output unit includes: at least one single power circuit, each single power circuit includes: two energy storage modules, two energy storage modules alternately carry out charge-discharge operation;Each energy storage module includes: multiple switch components and multiple capacitors, by adjusting the on-off state of multiple switch components, the charge-discharge state and connection relationship of multiple capacitors can be changed.The embodiment of the present disclosure fundamentally discards electromagnetic coupling element, so that the volume of motor system is reduced by more than 50% compared with traditional scheme, meet the needs of compact equipment of distributed energy, while being able to improve the stability of three-phase motor.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of motor system, and in particular to a motor system based on a single power circuit and a control method thereof. BACKGROUND

[0002] In a new energy power system, the performance of a frequency / stabilization energy storage phase-modulating motor is crucial to the stability of the power grid and the consumption of renewable energy, but the traditional scheme relies on an electromagnetic coupling transformer and an LC filter device, which is large in size and poor in stability. SUMMARY

[0003] To overcome the problems in the related art, the present disclosure provides a motor system based on a single power circuit and a control method thereof.

[0004] According to a first aspect of the embodiments of the present disclosure, a motor system based on a single power circuit is provided, comprising: a three-phase motor and a plurality of power output units, each phase of the three-phase motor being connected to a different power output unit;

[0005] Each power output unit comprises:

[0006] at least one single power circuit, each single power circuit comprising: two energy storage modules, the two energy storage modules alternately performing charging and discharging operations;

[0007] Each energy storage module comprises: a plurality of switching components and a plurality of capacitors, by adjusting the on-off state of the plurality of switching components, the charging and discharging state and the connection relationship of the plurality of capacitors can be changed; in the case that the energy storage module is in a discharging state, the plurality of capacitors in the energy storage module are connected in series with each other to generate a voltage for driving the three-phase motor; in the case that the energy storage module is in a charging state, the plurality of capacitors in the energy storage module are sequentially charged by the same power supply.

[0008] In some embodiments, the plurality of capacitors comprises: a first capacitor and a second capacitor;

[0009] The plurality of switching components comprises: a first switching component, a second switching component, a third switching component, a fourth switching component, and a fifth switching component;

[0010] The first switching component and the second switching component are respectively connected to two ends of the first capacitor, and the ends of the first switching component and the second switching component that are not connected to the first capacitor are connected to each other;

[0011] The third switching component and the fourth switching component are respectively connected to two ends of the second capacitor, and the ends of the third switching component and the fourth switching component that are not connected to the second capacitor are connected to each other;

[0012] The first end of the fifth switch assembly is a power output end, and the second end is connected to a first contact between the first switch assembly and the first capacitor;

[0013] A second contact between the first switch assembly and the second switch assembly is connected to the power supply;

[0014] A third contact between the first capacitor and the second switch assembly is connected to a fourth contact between the third switch assembly and the fourth switch assembly;

[0015] A fifth contact between the second capacitor and the fourth switch assembly is grounded.

[0016] In some embodiments, when the energy storage module is in a charging state, the first capacitor and the second capacitor of the energy storage module are alternately connected in series with the power supply to charge the first capacitor and the second capacitor, respectively;

[0017] When the energy storage module is in a discharging state, the first capacitor and the second capacitor of the energy storage module are connected in series with each other and to the power output end to boost the output of the three-phase motor.

[0018] In some embodiments, when the energy storage module is in a charging state, the first switch assembly and the fourth switch assembly of the energy storage module are in a conducting state, or the second switch assembly and the third switch assembly are in a conducting state;

[0019] When the energy storage module is in a discharging state, the fifth switch assembly and the third switch assembly of the energy storage module are in a conducting state.

[0020] In some embodiments, when there are multiple single power circuits, the multiple single power circuits are connected in series with each other, and the power output end of the last single power circuit is connected to one phase of the three-phase motor.

[0021] In some embodiments, the voltage signals output by any two power output units are 120° out of phase.

[0022] In some embodiments, the switch assembly is a bidirectional switch tube.

[0023] According to a second aspect of the embodiments of the present disclosure, a motor system control method is provided for controlling the motor system of the first aspect, and the method comprises:

[0024] determining a frequency deviation between an actual frequency of the three-phase motor and a rated frequency;

[0025] input the frequency deviation into a pre-constructed proportional-integral controller to obtain a frequency adjustment amount of the switching assembly, so as to adjust a switching frequency of the switching assembly, wherein a proportional coefficient in the proportional-integral controller is positively correlated with real-time power of the three-phase motor.

[0026] In some embodiments, the method further comprises:

[0027] collecting a voltage mean value of the capacitor in each switching cycle;

[0028] determining a voltage deviation between the power supply voltage and the capacitor according to the voltage mean value;

[0029] inputting the voltage deviation into a pre-constructed duty cycle adjustment model to obtain a charging duty cycle adjustment amount of the capacitor, so as to adjust the charging duty cycle of the capacitor, wherein the adjustment amount of the charging duty cycle is positively correlated with the voltage deviation.

[0030] In some embodiments, the duty cycle adjustment model takes the voltage deviation as input and outputs a product of the voltage deviation and a duty cycle adjustment coefficient.

[0031] Before the step of inputting the voltage deviation into the pre-constructed duty cycle adjustment model to obtain the charging duty cycle adjustment amount of the capacitor, the method further comprises:

[0032] determining the duty cycle adjustment coefficient and an adjustment step according to a power interval to which the real-time power of the three-phase motor belongs;

[0033] wherein the greater the power contained in the power interval, the greater the duty cycle adjustment coefficient and the adjustment step corresponding to the power interval.

[0034] The technical solution provided by the embodiments of the present disclosure can have the following beneficial effects:

[0035] The motor system provided by the embodiments of the present disclosure can drive the three-phase motor through the power output unit. The power output unit includes at least one single-power circuit, and each single-power circuit includes two energy storage modules. The two energy storage modules alternately perform charging and discharging operations to realize voltage boosting output of the input voltage, fundamentally abandoning electromagnetic coupling elements, reducing the volume of the motor system by more than 50% compared with the conventional scheme, meeting the needs of distributed energy for compact equipment, and improving the stability of the three-phase motor.

[0036] It should be understood that the foregoing general description and the following detailed description are only exemplary and explanatory, and cannot limit the present disclosure. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1Fig. 1 shows a schematic diagram of an architecture of a motor system based on a single power circuit according to an embodiment of the present disclosure.

[0038] Figure 2 Fig. 2 shows a schematic diagram of a structure of a single power circuit according to an embodiment of the present disclosure.

[0039] Figure 3 Fig. 3 shows a schematic diagram of state changes of a single power circuit according to an embodiment of the present disclosure.

[0040] Figure 4 Fig. 4 shows a schematic diagram of state changes of a single power circuit according to another embodiment of the present disclosure.

[0041] Figure 5 Fig. 5 shows a schematic diagram of a control method of a motor system according to an embodiment of the present disclosure.

[0042] Figure 6 Fig. 6 shows a schematic diagram of a control method of a motor system according to another embodiment of the present disclosure.

[0043] Reference Signs:

[0044] 100 - three-phase motor; 200 - power output unit; 300 - single power circuit; 400 - energy storage module; 411 - first capacitor; 412 - second capacitor; 421 - first switching assembly; 422 - second switching assembly; 423 - third switching assembly; 424 - fourth switching assembly; 425 - fifth switching assembly; 431 - power output terminal; 432 - power supply. DETAILED DESCRIPTION

[0045] The exemplary embodiments will be described in detail herein below with reference to the drawings. In the following description, unless otherwise indicated, like numbers in the figures indicate contact elements or features having the same or similar function. The following detailed description of the exemplary embodiments is not representative of all embodiments consistent with the present disclosure. Rather, they are merely examples of apparatuses and methods consistent with some aspects of the present disclosure as detailed in the appended claims.

[0046] The terminology used in the present disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used in the present disclosure and the appended claims, the singular forms "a," "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that the term "and / or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.

[0047] In addition, the terms "first", "second", etc. are used herein only to distinguish one element from another, and do not imply a relative importance.

[0048] Next, exemplary embodiments of the present disclosure will be described in detail.

[0049] First, refer to Figure 1 , Figure 1 A schematic diagram of an architecture of a motor system based on a single power circuit in an embodiment of the present disclosure is shown.

[0050] Specifically, as Figure 1 shown, the motor system provided by the embodiment of the present disclosure includes a three-phase motor 100 and a plurality of power output units 200. Each phase of the three-phase motor 100 is connected to a different power output unit 200.

[0051] Each power output unit 200 includes:

[0052] At least one single power circuit 300, each single power circuit 300 including two energy storage modules 400, the two energy storage modules 400 alternately performing charging and discharging operations.

[0053] Each energy storage module 400 includes a plurality of switching components and a plurality of capacitors. By adjusting the on-off state of the plurality of switching components, the charging and discharging state and connection relationship of the plurality of capacitors can be changed. In the case that the energy storage module 400 is in a discharging state, the plurality of capacitors in the energy storage module 400 are connected in series with each other to generate a voltage for driving the three-phase motor 100; in the case that the energy storage module 400 is in a charging state, the plurality of capacitors in the energy storage module 400 are sequentially charged by the same power supply 432.

[0054] It can be understood that the single power circuit 300 can provide a voltage for driving the three-phase motor 100. For the two energy storage modules 400 in each single power circuit, in the case that one of the energy storage modules 400 is in a charging state, the other energy storage module 400 will be in a discharging state. And at any moment, there is always one energy storage module 400 in a discharging state to supply power to the three-phase motor 100.

[0055] Exemplarily, for the energy storage module 400 in a charging state, by adjusting the switching components in the energy storage module 400, the plurality of capacitors in the energy storage module 400 can be sequentially connected in series with the power supply 432, so that the plurality of capacitors in the energy storage module 400 are respectively charged to the voltage of the power supply 432. Next, in the case that the energy storage module 400 is in a discharging state, by adjusting the switching components in the energy storage module 400, the plurality of capacitors in the energy storage module 400 can be connected in series with each other. At this time, since each capacitor can individually provide an output voltage close to the voltage of the power supply 432 after charging, the plurality of capacitors connected in series can provide an output voltage N times the voltage of the power supply 432, where N is the number of capacitors in a single energy storage module 400.

[0056] In some embodiments, the power output units 200 are connected to the three-phase motor 100 in a star or delta connection, each power output unit 200 independently provides an input voltage for one phase of the three-phase motor 100, and the voltage signals output by any two power output units 200 are 120° out of phase to meet the input requirements of the three-phase motor 100. The 120° phase difference control can be realized by a DSP controller, which can generate three sets of timing pulses that are 120° out of phase to drive the switching components in each power output unit 200, and in combination with a phase-locked loop chip (for example, ADF4351) to achieve a phase accuracy of ≤0.1°, thereby ensuring the symmetry of the three-phase voltage.

[0057] Therefore, the scheme provided by the embodiments of the present disclosure can omit the electromagnetic coupling element in the traditional transformer, and realize voltage boosting by adjusting the connection relationship of the capacitors in the energy storage module 400, so that the single power circuit 300 can provide voltage for driving the three-phase motor 100 through the energy storage module 400.

[0058] Next, please refer to Figure 2 , Figure 2 The structure of the single power circuit 300 in the embodiments of the present disclosure is shown. As Figure 2 shown, each single power circuit 300 includes two energy storage modules 400, and the two energy storage modules 400 are symmetrically designed in structure and share the same power supply 432, the same ground wire and the same power output end 431.

[0059] Among them, the plurality of capacitors in each energy storage module 400 can include a first capacitor 411 and a second capacitor 412; and the plurality of switching components in each energy storage module 400 can include a first switching component 421, a second switching component 422, a third switching component 423, a fourth switching component 424 and a fifth switching component 425.

[0060] Exemplarily, one of the energy storage modules 400 will be taken as an example below to illustrate the circuit structure of the energy storage module 400 in detail.

[0061] Please refer to Figure 2The first switch assembly 421 and the second switch assembly 422 in the energy storage module 400 are respectively connected to two ends of the first capacitor 411, and the ends of the first switch assembly 421 and the second switch assembly 422 not connected to the first capacitor 411 are connected to each other. The third switch assembly 423 and the fourth switch assembly 424 are respectively connected to two ends of the second capacitor 412, and the ends of the third switch assembly 423 and the fourth switch assembly 424 not connected to the second capacitor 412 are connected to each other. The first end of the fifth switch assembly 425 is the power output end 431, and the second end is connected to the first contact between the first switch assembly 421 and the first capacitor 411. The second contact between the first switch assembly 421 and the second switch assembly 422 is connected to the power supply 432. The third contact between the first capacitor 411 and the second switch assembly 422 is connected to the fourth contact between the third switch assembly 423 and the fourth switch assembly 424. The fifth contact between the second capacitor 412 and the fourth switch assembly 424 is grounded.

[0062] Exemplarily, the switch assemblies in the energy storage module 400 are bidirectional switch tubes. For example, the bidirectional switch tubes can be SiC devices and / or IGBT devices combined.

[0063] Based on the arrangement of the bidirectional switch tubes, four-quadrant operation of the three-phase motor 100 can be realized. When the three-phase motor 100 is in the motoring mode (energy flows forward), direct current energy can be transmitted to the motor by controlling the conduction direction of the switch assemblies. When the three-phase motor 100 is in the generating mode (energy flows reversely), energy can be fed back to the capacitor and the direct current side by controlling the conduction direction of the switch assemblies, thereby supporting seamless switching of the motor between the motoring / generating states.

[0064] The following refers to Figure 3 and Figure 4 , Figure 3 and Figure 4 shows a state change schematic diagram of a single power circuit 300 in an embodiment of the present disclosure. In Figure 3 and Figure 4 , the left side energy storage module 400 is in the charging state, and the right side energy storage module 400 is in the discharging state. The charging and discharging states of the two energy storage modules 400 can be switched alternately. That is, when the energy storage module 400 on one side is charged, the energy storage module 400 on the other side is discharged.

[0065] Specifically, refer to Figure 3 and Figure 4 , in the case that the energy storage module 400 is in the charging state, the first capacitor 411 and the second capacitor 412 of the energy storage module 400 are alternately connected in series with the power supply 432, so as to charge the first capacitor 411 and the second capacitor 412 respectively.

[0066] That is, when the energy storage module 400 is in the charging state, the first switch assembly 421 and the fourth switch assembly 424 of the energy storage module 400 can be made to be in the on state, so that the power supply 432 is connected in series with the first capacitor 411 in the energy storage module 400, thereby charging the first capacitor 411. Alternatively, the second switch assembly 422 and the third switch assembly 423 of the energy storage module 400 can be made to be in the on state, so that the power supply 432 is connected in series with the second capacitor 412 in the energy storage module 400, thereby charging the second capacitor 412.

[0067] Exemplarily, the first capacitor 411 can be charged first, and the second capacitor 412 can be charged after the first capacitor 411 is fully charged. Alternatively, the second capacitor 412 can be charged first, and the first capacitor 411 can be charged after the second capacitor 412 is fully charged.

[0068] It can be understood that, when the charging of the first capacitor 411 is switched to the charging of the second capacitor 412, the current flowing through the first switch assembly 421 and the fourth switch assembly 424 gradually decreases to 0 as the first capacitor 411 is gradually charged to the voltage of the power supply 432, and at this time, the second switch assembly 422 is on and the fourth switch assembly 424 is off. The first switch assembly 421 is off due to the reverse voltage formed by the first capacitor 411, the second capacitor 412 and the power supply 432 connected in series, the third switch assembly 423 is on due to the forward voltage formed by the second capacitor 412 and the power supply 432 connected in series, and the switching is completed. The first switch assembly 421 and the fourth switch assembly 424 are close to soft off in this process, the second switch assembly 422 and the third switch assembly 423 are close to soft on due to the forward voltage of almost 0, so the loss in the switching process is small.

[0069] Next, please refer to the energy storage module 400 on the right side of the single-power circuit 300 in Figure 3 and Figure 4 When the energy storage module 400 is in the discharging state, the first capacitor 411 and the second capacitor 412 of the energy storage module 400 are connected in series with each other and connected to the power output end 431, so as to boost the output of the three-phase motor 100.

[0070] That is, when the energy storage module 400 is in the discharging state, the fifth switch assembly 425 and the third switch assembly 423 of the energy storage module 400 can be made to be in the on state, so that the first capacitor 411 and the second capacitor 412 are connected in series with each other, thereby providing the three-phase motor 100 with an output voltage twice the voltage of the power supply 432 through the power output end 431.

[0071] It can be understood that, Figure 2 , Figure 3 and Figure 4is taken as an example, the specific structure of the single power circuit 300 is exemplarily illustrated. Based on the single power circuit 300 provided by Figure 2 、 Figure 3 and Figure 4 , an output voltage twice as high as the input voltage can be provided. Based on the same technical concept, those skilled in the art can also make the number of capacitors in each energy storage module 400 greater than two, and by adaptively designing the switching assembly, these capacitors can be respectively charged to the voltage of the power supply 432 and then connected in series with each other, so that the energy storage module 400 outputs more than twice the voltage of the power supply 432.

[0072] Exemplarily, in the case where the number of single power circuits 300 is multiple, the multiple single power circuits 300 can be connected in series with each other, and the power output end 431 of the last single power circuit 300 is connected to one phase of the three-phase motor 100. Specifically, each single power circuit 300 can be assumed as a DC power supply with positive and negative electrodes, and by connecting the positive electrode of the previous stage DC power supply to the negative electrode of the next stage DC power supply, the voltage of the last output end can be increased by connecting the DC power supplies in series.

[0073] Specifically, among the single power circuits 300 connected in series, the energy storage modules 400 in the discharging state in different single power circuits 300 can be connected in series with each other by increasing the switching tube or directly connecting, so as to supply power to the outside together; and the energy storage modules 400 in the charging state are independently grounded, so that the capacitors therein are respectively charged to the voltage of the power supply 432.

[0074] It can be understood that the cascade mode of connecting the output end of the previous stage single power circuit to the input end of the next stage single power circuit is adopted. The output side of the DC voltage booster integrated by M single power circuits obtains a stable DC voltage about N times M times the input voltage in the steady state, where N is the number of capacitors of an energy storage module in a single power circuit, and M is the number of single power circuits connected in series.

[0075] The embodiment of the disclosure makes the power supply side of the three-phase motor abandon the traditional transformer, and the volume is reduced by more than 50%, the weight is reduced by 40%, and the stability of the three-phase motor can be improved.

[0076] In some embodiments, Figure 5 a flowchart of a motor system control method in an embodiment of the disclosure is shown, and the method is used for controlling the motor system as shown in Figure 1 to Figure 4 . As shown in Figure 5 , the method comprises the following steps.

[0077] S501, determining the frequency deviation between the actual frequency of the three-phase motor and the rated frequency.

[0078] S502, input the frequency deviation into the pre-constructed proportional-integral controller to obtain a frequency adjustment amount of the switching assembly, so as to adjust the switching frequency of the switching assembly.

[0079] The proportional coefficient in the proportional-integral controller is positively correlated with the real-time power of the three-phase motor.

[0080] Exemplarily, Figure 6 A flowchart of another motor system control method in the embodiment of the present disclosure is shown. As shown in the figure, Figure 6 The method includes the following steps.

[0081] S601, collect the voltage average of the capacitor in each switching cycle.

[0082] S602, determine the voltage deviation between the power supply voltage and the capacitor according to the voltage average.

[0083] S603, input the voltage deviation into the pre-constructed duty cycle adjustment model to obtain the charging duty cycle adjustment amount of the capacitor, so as to adjust the charging duty cycle of the capacitor.

[0084] The adjustment amount of the charging duty cycle is positively correlated with the voltage deviation.

[0085] In some embodiments, the duty cycle adjustment model takes the voltage deviation as input and takes the product of the voltage deviation and the duty cycle adjustment coefficient as output. When performing the above S603, the duty cycle adjustment coefficient and the adjustment step can be determined according to the power interval to which the real-time power of the three-phase motor belongs. The greater the power contained in the power interval, the greater the duty cycle adjustment coefficient and the adjustment step corresponding to the power interval.

[0086] It can be understood that, Figure 5 The method shown is used to realize the frequency stabilization control of the three-phase motor, and Figure 6 The method shown is used to realize the voltage stabilization control. The specific principles and implementation manners of the above frequency stabilization control and voltage stabilization control will be introduced in detail below in combination with the following steps 1 to step 6.

[0087] Step 1: multi-scale frequency detection and noise suppression

[0088] Hardware implementation: main control chip: TI TMS320F28335 DSP, integrated 16-bit ADC (sampling rate 20kSPS);

[0089] Frequency detection circuit: based on ADF4351 phase-locked loop chip, capture voltage zero-crossing error ≤0.1° electrical angle.

[0090] 1) Voltage signal preprocessing: 50μs period sampling, through a second-order Butterworth low-pass filter (cutoff frequency 100Hz);

[0091] 2) Period calculation: 10 consecutive voltage periods are detected, and the sliding average is obtained:

[0092] (1)

[0093] where, is the voltage period, and the high-frequency noise is suppressed by the sliding average filtering algorithm to improve the stability of frequency detection; represents the i th detected voltage period (unit: s), i.e. the period of the i-th voltage waveform in the 10 consecutive detections (i = 1, 2, …, 10). i

[0094] 3) Frequency calculation:

[0095] (2)

[0096] where: is the real-time frequency at the motor end, with a resolution of 0.01 Hz;

[0097] 4) Deviation calculation:

[0098] (3)

[0099] where, is the frequency deviation, is the rated frequency (50 Hz), and the trigger threshold .

[0100] Detection results As the input signal of step 2, the drive switching frequency adjustment, and the detection noise suppression ensure the accuracy of subsequent control.

[0101] Step 2: Frequency-capacitor voltage coupling modeling and regulation logic

[0102] Based on the law of conservation of capacitive power, the relationship between switching frequency and capacitor voltage is derived:

[0103] (4)

[0104] where, is the capacitor voltage fluctuation amplitude (design nominal value 200V); is the charging duty ratio, defined as the ratio of charging time to switching period; P is the transmission power (W), calculated in real time by the motor load.

[0105] Positive frequency deviation ( >0): increase =10Hz every 0.1ms, until ≤0.1Hz, and decrease simultaneously​ =0.01 / time, reducing the stored energy;

[0106] negative frequency deviation ( <0: Decreases every 0.1ms =10Hz, until ≥-0.1Hz, synchronous increase =0.01 / time, increasing energy storage capacity.

[0107] The adjustment result determines the switching cycle. T =1 / This provides a time reference for voltage detection in step 4. The adjustment affects the duty cycle calculation in step 5.

[0108] Step 3: Adaptive PI frequency closed-loop control

[0109] Controller design:

[0110] Scale factor: (Light load) ~ 1.2Hz (Heavy load), automatically switching according to real-time power;

[0111] Integral coefficient: Integral saturation threshold ±5Hz;

[0112] Output formula:

[0113] (5)

[0114] in, To adjust the switching frequency, To adjust the switching frequency.

[0115] Hardware implementation:

[0116] PWM drive circuit: TC4427 chip, supporting frequencies from 1.16kHz to 11.6kHz, with a duty cycle resolution of 0.1%;

[0117] Protection mechanism: Frequency over-limit ( >11.6kHz or When the frequency is <1.16kHz, a hardware interlock is triggered, shutting down all switching transistors.

[0118] Output The detection cycle of step 1 is directly controlled to form a closed loop of "detection-adjustment-feedback".

[0119] Step 4: High-precision capacitor voltage average detection

[0120] Hardware solution:

[0121] Voltage sensor: LEM LV25-P Hall sensor, measurement range 0~500V, linearity ±0.15%;

[0122] Peak holding circuit: RC network (R=10kΩ, C=10μF) combined with LM339 voltage comparator, locking the peak value of capacitor voltage in each switching cycle U max And U min , first defined: U max Capacitor voltage peak, U min Capacitor voltage valley.

[0123] Software implementation:

[0124] Median filter: take the middle value after sorting the last 5 sampling values, suppress sharp peak noise;

[0125] Mean value calculation:

[0126] (6)

[0127] Where, Capacitor voltage mean value, detection period synchronized with switching period T.

[0128] As the input parameter of step 5, its detection accuracy directly affects the accuracy of duty cycle adjustment.

[0129] Step 5: segmented proportional duty cycle adjustment strategy

[0130] Model and algorithm of step 1-4 are engineered, through the closed loop process of "data collection-computation-verification-execution", to realize real-time frequency control.

[0131] Deviation definition:

[0132] (7)

[0133] Where, Rated voltage of DC excitation source, allowable fluctuation range ±2%, first defined: Capacitor voltage mean value deviation.

[0134] Adaptive adjustment:

[0135] Light load ( ): , each adjustment step ;

[0136] Rated load ( ): , each adjustment step ;

[0137] Heavy load ( ): , each adjustment step ;

[0138] Adjustment formula:

[0139] (8)

[0140] Where, is the charging duty ratio after adjustment, is the charging duty ratio before adjustment, duty ratio limit 0.1≤ D 0≤0.8.

[0141] D The adjustment of 0 changes the charging time in step 2, thereby affecting the energy storage energy of the capacitor, forming a negative feedback control on Uc.

[0142] Step 6: Energy balance and frequency pressure cooperative control

[0143] Energy equation:

[0144] (9)

[0145] Where, is the single charging energy, which is proportional to the average value of the capacitor voltage , fluctuation amplitude .

[0146] Cooperative mechanism:

[0147] Feedforward control: the adjustment of in step 3 quickly responds to frequency disturbances, ensuring stable motor speed;

[0148] Feedback control: the adjustment of D 0 in step 5 slowly adjusts the energy storage energy to suppress voltage fluctuations;

[0149] Parameter coupling: through:

[0150] (10)

[0151] Where, is the higher voltage value of the bridge arm capacitor at a certain moment; is the lower voltage value of the bridge arm capacitor at a certain moment.

[0152] So far, the present disclosure aims at the problems of large volume, low efficiency and poor stability of traditional motor systems, and proposes a capacitive power transfer technology based on single power circuit cascade. Through the "H-bridge" topology design without transformer, the bidirectional switch tube and the symmetric bridge arm capacitor are used to realize the bidirectional flow of energy, and the multi-stage cascade structure is used to expand the output voltage to 2N times of the input voltage (in the case of two bridge arm capacitors in the energy storage module), which fundamentally eliminates the electromagnetic coupling elements, reduces the device volume by more than 50% compared with the traditional scheme, and meets the needs of distributed energy for compact equipment. The frequency-energy double closed loop strategy is adopted in the control layer, and the switching frequency and charging duty cycle are dynamically adjusted by real-time detection of motor terminal frequency and capacitor voltage average, to realize wide frequency stabilization, dynamic voltage stabilization and high efficiency phase compensation, and comprehensively improve the motor operation performance.

[0153] The system core of the present disclosure is a symmetrically designed single power circuit, which integrates silicon carbide switch tubes and metalized film capacitors, supports high frequency operation of 1.16 kHz to 11.6 kHz, and has a withstand voltage level of 2.5 kV. The multi-stage single power circuit realizes voltage gain through rigid cascade, and the last stage output adopts star connection or delta connection to connect the motor, and the neutral point is configured with a zero sequence filter to suppress interference. The frequency stabilization control accurately captures the frequency deviation by means of phase-locked loop and sliding average filter, and quickly adjusts the switching frequency by adaptive PI algorithm, to ensure that the frequency fluctuation is ≤±0.2 Hz; the voltage stabilization control uses Hall sensors and peak holding circuits to monitor the capacitor voltage in real time, and adjusts the duty cycle according to the load, to form a coordinated closed loop of "fast frequency response-accurate energy balance", and the voltage ripple can be controlled within 1%. The two are deeply coupled through the capacitor voltage fluctuation amplitude, to realize bidirectional linkage control of frequency and voltage.

[0154] The present disclosure realizes breakthroughs in key indicators such as volume, efficiency and stability through dual innovation of topology and control: the transformerless design makes the volume of a 500 kW prototype only half of that of the traditional scheme, the application of high-frequency silicon carbide devices reduces the switching loss by 60%, and the system efficiency is improved to 99.4%; the frequency stabilization accuracy is 0.01 Hz, the frequency regulation time is ≤50 ms, and it can effectively respond to the frequency fluctuation of 47~53 Hz of new energy power grid; the voltage recovery time is ≤120 ms when the load suddenly changes, the power factor is corrected to more than 0.95, and the motor four-quadrant operation and bidirectional energy efficient flow are supported. Through prototype verification, all performance indicators are better than existing schemes, providing a high reliability and high integration solution for motor control in wind power, photovoltaic and other fields, and having broad engineering application prospects.

[0155] The preferred embodiments of the present disclosure are described in detail above with reference to the drawings, but the present disclosure is not limited to the specific details in the above-described embodiments. Various simple modifications can be made to the technical solutions of the present disclosure within the technical concept of the present disclosure, and these simple modifications all belong to the protection scope of the present disclosure.

[0156] In addition, it should be noted that each specific technical feature described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, various possible combinations are not described again in the present disclosure.

[0157] In addition, various different embodiments of the present disclosure can also be combined in any appropriate manner, as long as they do not deviate from the idea of the present disclosure, and they should also be considered as disclosed in the present disclosure.

Claims

1. A single power circuit based motor system, characterized by, The motor system comprises: a three-phase motor and a plurality of power output units, each phase of the three-phase motor being connected to a different power output unit; each power output unit comprises: at least one single-power circuit, each single-power circuit comprising: two energy storage modules, which alternately perform charging and discharging operations; 2. The electric machine system of claim 1, wherein, each energy storage module comprises: a plurality of switch components and a plurality of capacitors, by adjusting the on-off state of the plurality of switch components, the charging and discharging state and the connection relationship of the plurality of capacitors can be changed; in the case that the energy storage module is in the discharging state, the plurality of capacitors in the energy storage module are connected in series with each other to generate a voltage for driving the three-phase motor; in the case that the energy storage module is in the charging state, the plurality of capacitors in the energy storage module are sequentially charged by the same power supply. The plurality of capacitors comprises: a first capacitor and a second capacitor; The plurality of switch components comprises: a first switch component, a second switch component, a third switch component, a fourth switch component and a fifth switch component; The first switch component and the second switch component are respectively connected to two ends of the first capacitor, and the ends of the first switch component and the second switch component not connected to the first capacitor are connected to each other; The third switch component and the fourth switch component are respectively connected to two ends of the second capacitor, and the ends of the third switch component and the fourth switch component not connected to the second capacitor are connected to each other; 3. The electric machine system of claim 2, wherein, The first end of the fifth switch component is a power output end, and the second end is connected to a first contact between the first switch component and the first capacitor; A second contact between the first switch component and the second switch component is connected to the power supply; 4. The electric machine system of claim 2, wherein, A third contact between the first capacitor and the second switch component is connected to a fourth contact between the third switch component and the fourth switch component; A fifth contact between the second capacitor and the fourth switch component is grounded.

5. The electric machine system of claim 1, wherein, In the case that the energy storage module is in the charging state, the first capacitor and the second capacitor of the energy storage module are alternately connected in series with the power supply to charge the first capacitor and the second capacitor, respectively; 6. The electric machine system of claim 1, wherein, In the case that the energy storage module is in the discharging state, the first capacitor and the second capacitor of the energy storage module are connected in series with each other and to the power output end to boost the output of the three-phase motor.

7. The electric machine system according to any one of claims 1 to 6, characterized by In the case that the energy storage module is in the charging state, the first switch component and the fourth switch component of the energy storage module are in the on state, or the second switch component and the third switch component are in the on state; 8. A motor system control method characterized by comprising: In the case that the energy storage module is in the discharging state, the fifth switch component and the third switch component of the energy storage module are in the on state. In the case that there are a plurality of single-power circuits, the plurality of single-power circuits are connected in series with each other, and the power output end of the last single-power circuit is connected to one phase of the three-phase motor. The voltage signals output by any two power output units are 120° out of phase. The switch component is a bidirectional switch tube. The method for controlling the motor system as claimed in any one of claims 1 to 7 comprises: determining the frequency deviation between the actual frequency and the rated frequency of the three-phase motor; The frequency deviation is input into a pre-constructed proportional-integral controller to obtain a frequency adjustment amount of the switching assembly, so as to adjust the switching frequency of the switching assembly, wherein a proportional coefficient in the proportional-integral controller is positively correlated with the real-time power of the three-phase motor.

9. The method of claim 8, wherein, The method further comprises: collecting a voltage average of the capacitor in each switching cycle; determining a voltage deviation between the power supply voltage and the capacitor according to the voltage average; inputting the voltage deviation into a pre-constructed duty cycle adjustment model to obtain a charging duty cycle adjustment amount of the capacitor, so as to adjust the charging duty cycle of the capacitor, wherein the adjustment amount of the charging duty cycle is positively correlated with the voltage deviation.

10. The method of claim 9, wherein, The duty cycle adjustment model takes the voltage deviation as input and takes the product of the voltage deviation and a duty cycle adjustment coefficient as output; Before the step of inputting the voltage deviation into the pre-constructed duty cycle adjustment model to obtain the charging duty cycle adjustment amount of the capacitor, the method further comprises: determining the duty cycle adjustment coefficient and an adjustment step according to a power interval to which the real-time power of the three-phase motor belongs; wherein the greater the power contained in the power interval, the greater the duty cycle adjustment coefficient and the adjustment step corresponding to the power interval.

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