Optimized control method and circuit for multi-bridge-arm switching power amplifier circuit

Abstract

The invention belongs to the technical field of electromagnetic bearing control, and discloses an optimal control method and circuit for a multi-bridge-arm switching power amplifier circuit, and the method comprises the steps: collecting circuit data, building a single-cycle control mathematical model of a multi-bridge-arm switching power amplifier, and calculating the duty ratio of a single cycle; setting a state switching criterion of a charging and discharging period, and judging a charging and discharging state of a single period; calculating a duty ratio value d, and outputting the duty ratio to a corresponding switch tube; acquiring an actual current i in the coil, and subtracting the actual current i from the reference current; and calculating the conduction state and the duty ratio of a load bridge arm switch tube according to the difference value, and generating a PWM wave corresponding to the switch tube. According to the method, accurate control is achieved through feedback calculation of the cycle average value. Through the combination of the methods, the multi-bridge-arm switching power amplifier system can play an important role in multi-degree-of-freedom magnetic suspension control, and has relatively high integration level, stability and control precision.

Description

Technical Field

[0001] The present invention belongs to the technical field of electromagnetic bearing control, and in particular relates to an optimization control method and circuit for a multi-bridge arm switching power amplifier circuit. Background Art

[0002] When the rotor is offset due to external disturbances, the power amplifier needs to switch the current polarity and adjust the amplitude within microseconds so that the direction of the electromagnetic force is opposite to the displacement deviation, forming a closed-loop suppression effect. This process requires the amplifier to have a high bandwidth to match the controller's adjustment frequency, while also ensuring high linearity and low ripple in the current output to prevent electromagnetic force pulsations from causing high-frequency oscillations in the rotor. Under single-cycle control, traditional switching power amplifiers are usually implemented using analog circuits. Although analog control can meet the working requirements of switching power amplifiers to a certain extent, the five-degree-of-freedom magnetic bearing system usually requires five independent switching power amplifiers, which makes the application of analog circuits more complex and large. In addition, analog control faces many challenges, such as inconvenient parameter adjustment, difficult hardware structure modification, difficulty in implementing advanced control algorithms, and aging of components.

[0003] Chinese patent publication number CN111894979A, titled "A multi-arm switching power amplifier circuit with fault tolerance," comprises a main circuit structure and a functional module structure, the main circuit structure being electrically connected to the functional module structure. The main circuit structure includes a common bridge arm, five-phase load bridge arms, a load bridge arm fault switching circuit, a backup bridge arm, and a common bridge arm fault switching circuit, all electrically connected in sequence. This patent application fails to address the issues of difficult parameter adjustment and poor control accuracy associated with multi-arm switching power amplifier circuits. Summary of the Invention

[0004] To overcome the aforementioned problems in the prior art, the present invention provides an optimized control method and circuit for a multi-arm switching power amplifier circuit, achieving precise control through feedback calculation of periodic average values. The combination of these methods enables multi-arm switching power amplifier systems to play an important role in magnetic levitation control with multiple degrees of freedom, achieving high integration, stability, and control accuracy.

[0005] To achieve the above object, the technical solution adopted by the present invention is: In a first aspect, the present invention provides an optimization control method for a multi-arm switching power amplifier circuit, comprising the following steps: Collect circuit data, including: coil current i0 at the initial moment of a single cycle, current reference value iref, bus voltage Udc, period Ts, load R, and inductance L; Establish a single-cycle control mathematical model for a multi-arm switching power amplifier and calculate the duty cycle of a single cycle; Set the state switching criteria of the charge and discharge cycle to determine the charge and discharge state of a single cycle; Calculate the duty cycle value d and output the duty cycle to the corresponding switch tube; Collect the actual current i in the coil and make the difference between the actual current i and the reference current; The conduction state and duty cycle of the load bridge arm switch tube are calculated based on the difference, and a PWM wave of the corresponding switch tube is generated; the PWM wave is output to the switch tube in the magnetic bearing switch power amplifier.

[0006] Optionally, the actual current i in the coil is collected by a current sensor.

[0007] Optionally, the difference between the actual current i and the reference current is input to a controller, and a PWM wave of a corresponding switching tube is generated by the controller.

[0008] Optionally, the mathematical model of the single-cycle control duty cycle d is: ; Where: L is the inductance of the magnetic bearing coil; R is the resistance of the magnetic bearing coil; iref is the current reference value; i(t0) is the initial value of the single-cycle coil feedback current; Ts is the sampling period, and Udc is the bus voltage.

[0009] Optionally, the state switching criterion of the charge and discharge cycle is: when Δi(k)≥0, the coil should be in the charging state in this cycle; when Δi(k)<0, the coil should be in the discharging state in this cycle; where Δi(k) is the difference between the input current and the output current. Optionally, the formula for calculating the duty cycle value d is: When Δi(k)≥0,

[0010] When Δi(k)<0,

[0011] Where: i(t0) is the initial value of the single-cycle coil feedback current; iref is the current reference value; L is the magnetic bearing coil inductance; R is the magnetic bearing coil resistance; Ts is the sampling period.

[0012] In a second aspect, the present invention provides a multi-arm switching power amplifier circuit, which is controlled by the optimization control method of a multi-arm switching power amplifier circuit. The circuit includes: a power supply, the power supply is electrically connected to a common bridge arm, the common bridge arm is connected in parallel with multiple load bridge arms, each load bridge arm and the common bridge arm has two upper and lower switching tubes connected in series; the upper switching tube and the lower switching tube of the common bridge arm are respectively connected between the upper switching tube and the lower switching tube of each load bridge arm through a capacitor.

[0013] Optionally, the duty cycle of the common bridge arm is fixed at 0.5.

[0014] Optionally, the number of the load bridge arms is five.

[0015] Optionally, the switch tubes of the load bridge arm and the common bridge arm are both IGBT switch tubes or MOSFET switch tubes.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This paper proposes a fixed duty cycle control method that adapts to current polarity changes and a method for achieving precise control through feedback calculation of periodic average values. The combination of these methods enables a multi-arm switching power amplifier system to play a vital role in magnetic levitation control with multiple degrees of freedom, achieving high integration, stability, and control accuracy.

[0017] The control method of the present invention employs a control mode that directly tracks periodic current variables, resulting in a fast response. It also eliminates the need for a separate control algorithm for the common bridge arm, simplifying the control strategy. This control method significantly improves computational efficiency, shortens controller operation time, and provides a more efficient and simplified control solution for the system.

[0018] Furthermore, to more precisely control each current path, the present invention calculates the switching value of each bridge arm switch in real time by sampling the cycle-averaged value of each output current and the cycle-averaged value of the desired current. This feedback control mechanism ensures the precision of current regulation in the multi-arm switching amplifier, ultimately achieving precise decoupling control of the five current paths. This precise control method effectively avoids the multi-current coupling problem present in traditional full-bridge structures, resulting in a more efficient and stable magnetic levitation control system. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings described herein are for illustrative purposes only and are not intended to limit the scope of the present invention in any way. In addition, the shapes and proportional dimensions of the components in the drawings are only schematic and are used to help understand the present invention, and are not intended to specifically limit the shapes and proportional dimensions of the components of the present invention. In the drawings: Figure 1 This is the block diagram of the single-degree-of-freedom magnetic bearing switching power amplifier control system.

[0020] Figure 2 This is a schematic diagram of a five-phase six-bridge arm main power circuit according to an embodiment of the present invention; Figure 3 Schematic diagram of the circuit topology structure of the load bridge arm and the common bridge arm of phase A according to an embodiment of the present invention; Figure 4 This is a schematic diagram of a charging cycle according to an embodiment of the present invention; Figure 5This is a schematic diagram of a discharge cycle according to an embodiment of the present invention; Figure 6 Schematic diagram of step response simulation waveforms under different bus voltage conditions according to an embodiment of the present invention; Figure 7 Schematic diagram of the sinusoidal current output of phase A and its partial enlargement in an embodiment of the present invention; Figure 8 Schematic diagram of five asymmetric sinusoidal current outputs according to an embodiment of the present invention. DETAILED DESCRIPTION

[0021] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0022] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are intended to fall within the scope of protection of the present invention.

[0023] In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. appear, the orientation or position relationship indicated is based on the orientation or position relationship shown in the accompanying drawings, or is the orientation or position relationship in which the product of the invention is usually placed when in use. It is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention.

[0024] When an element is referred to as being "disposed on" another element, it may be directly on the other element or there may also be an intermediate element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may also be an intermediate element. The terms "vertical", "horizontal", "left", "right" and similar expressions used in the present invention are for illustrative purposes only and are not intended to be the only embodiment. If the term "horizontal" appears, it does not mean that the component is required to be absolutely horizontal, but it can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", which does not mean that the structure must be completely horizontal, but it can be slightly tilted.

[0025] It should be noted that similar reference numerals and letters denote similar items in the following figures. Therefore, once an item is defined in one figure, it does not need to be further defined or explained in subsequent figures. In the description of the present invention, it should be understood that the terms "comprise" and "include" indicate the presence of the described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or their combinations.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the art to which this invention pertains. The terms used in the present specification are for the purpose of describing specific embodiments only and are not intended to limit the present invention. As used in the present specification and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms unless the context clearly indicates otherwise.

[0027] The present invention will be described in detail below with reference to the accompanying drawings.

[0028] An optimization control method for a multi-arm switching power amplifier circuit of the present invention comprises the following steps: Collect circuit data, including: coil current i0 at the initial moment of a single cycle, current reference value iref, bus voltage Udc, period Ts, load R, and inductance L; Establish a single-cycle control mathematical model for a multi-arm switching power amplifier and calculate the duty cycle of a single cycle; Set the state switching criteria of the charge and discharge cycle to determine the charge and discharge state of a single cycle; Calculate the duty cycle value d and output the duty cycle to the corresponding switch tube; Collect the actual current i in the coil and make the difference between the actual current i and the reference current; The conduction state and duty cycle of the load bridge arm switch tube are calculated based on the difference, and a PWM wave of the corresponding switch tube is generated; the PWM wave is output to the switch tube in the magnetic bearing switch power amplifier.

[0029] A multi-bridge-arm switching power amplifier circuit according to the present invention comprises: a power supply electrically connected to a common bridge arm, the common bridge arm being connected in parallel to multiple load bridge arms, each load bridge arm and the common bridge arm each having two upper and lower switching transistors connected in series; the upper and lower switching transistors of the common bridge arm being connected to the upper and lower switching transistors of each load bridge arm via capacitors. The duty cycle of the common bridge arm is fixed at 0.5.

[0030] The circuit of the present invention uses a multi-bridge switching amplifier to replace the traditional full-bridge switching amplifier. It can output five independent currents, and each current must be able to track the current control signal generated by five displacement regulators in real time. In this way, the system can achieve suspension control in the five degrees of freedom of the magnetic bearing, thereby improving the flexibility and precision of the system. Specifically, this method fixes the duty cycle of the switching tube of the common bridge arm to 0.5. By utilizing this stable duty cycle characteristic, it can effectively adapt to the needs of changing the polarity of the five currents, thereby avoiding cross-coupling between the currents.

[0031] Example 1 Figure 1 This is a framework diagram of the control system for a single-degree-of-freedom magnetic bearing switching power amplifier. The system primarily consists of a controller, a switching power amplifier, and a current sensor. The current sensor detects and samples the actual current in the coil. The result is subtracted from the reference current and fed into the controller. The controller uses interpolation and single-cycle control principles to calculate the turn-on timing and duration of the four switches, generating corresponding switching signals. The switching power amplifier, serving as the main circuit, controls the corresponding switches based on these switching signals, thereby dynamically regulating the magnetic bearing coil current.

[0032] The topology of the main power is a five-phase six-bridge switching power amplifier topology. The specific topology is as follows: Figure 2 shown.

[0033] The main power circuit of a five-phase, six-leg switching power amplifier utilizes a multiphase topology, driving five independent phases through six half-legs, achieving a balance between high power output and low ripple. Its core consists of 12 power switching devices (such as IGBTs or MOSFETs) forming six pairs of half-legs. The midpoint outputs of each leg pair are connected in a specific manner to synthesize a five-phase voltage. The DC bus input is filtered by capacitors before powering the legs. Inductors are typically connected in series with each phase output to suppress switching harmonics. This topology significantly reduces current harmonics and torque ripple through five-phase phase-shift modulation, making it suitable for applications requiring stringent smoothness. The six-leg design allows system reconfiguration to degraded operation in the event of a single leg failure. The control system typically utilizes a five-phase space vector modulation algorithm, combined with current closed-loop feedback for dynamic PWM control, achieving high efficiency and reliability in applications such as motor drives and precision power supplies. While this topology is more complex than traditional three-phase topologies, it offers superior output quality.

[0034] The five load bridge arms—A, B, C, D, and E—are used to control five independent currents corresponding to the magnetic bearing system's degrees of freedom. Each phase has its own independent control circuit, ensuring that the currents in each phase can be adjusted independently without interfering with each other.

[0035] Among them, the common bridge arm N includes the common bridge arm upper switch tube Q1 and the common bridge arm lower switch tube Q2; the A phase load bridge arm includes the A phase bridge arm upper switch tube Q3 and the A phase bridge arm lower switch tube Q4, the B load bridge arm includes the B phase bridge arm upper switch tube Q5 and the B phase bridge arm lower switch tube Q6, the C load bridge arm includes the C phase bridge arm upper switch tube Q7 and the C phase bridge arm lower switch tube Q8, the D load bridge arm includes the D phase bridge arm upper switch tube Q9 and the common bridge arm upper switch tube D phase bridge arm lower switch tube Q10, and the E load bridge arm includes the E phase bridge arm upper switch tube Q11 and the E phase bridge arm lower switch tube Q12.

[0036] The common bridge arm upper switch tube Q1 and the common bridge arm lower switch tube Q2 of the common bridge arm N are connected between the A-phase bridge arm upper switch tube Q3 and the A-phase bridge arm lower switch tube Q4 through the A-phase capacitor x; connected between the B-phase bridge arm upper switch tube Q5 and the B-phase bridge arm lower switch tube Q6 through the B-phase capacitor y; the C-phase capacitor z is connected between the C-phase bridge arm upper switch tube Q7 and the C-phase bridge arm lower switch tube Q8; the D-phase capacitor u is connected between the D-phase bridge arm upper switch tube Q9 and the common bridge arm upper switch tube D-phase bridge arm lower switch tube Q10; and the E-phase capacitor z is connected between the E-phase bridge arm upper switch tube Q11 and the E-phase bridge arm lower switch tube Q12.

[0037] The common bridge arm, N, connects to the load bridge arm and plays a key role in maintaining overall system balance, ensuring the coordination of all currents. It works in conjunction with the load bridge arm to manage switching states and maintain current flow. In this structure, the output current of each bridge arm can be independently controlled, which is crucial for the precision required by magnetic levitation systems. The advantage of a five-phase configuration is that it reduces the amount of switching equipment required compared to traditional multi-bridge configurations, thereby reducing system complexity and cost.

[0038] In actual operation, since the working principle of each circuit is the same, phase A is taken as an example for derivation and analysis. Figure 3 The circuit topology of the load bridge arm and the common bridge arm is shown in Figure 1. The upper and lower switches in the A-phase bridge arm are Q3 (the upper switch) and Q4 (the lower switch), respectively. Their duty cycle is d, and they conduct in a complementary manner. The upper and lower switches in the common bridge arm, N, are Q1 (the upper switch) and Q2 (the lower switch), respectively. Their duty cycle is 0.5, and they conduct in a complementary manner.

[0039] The waveform when Δi(k)≥0 under the single-cycle unipolar algorithm control is as follows: Figure 4 As shown in the figure, from top to bottom are the trigger pulse of the switching cycle, the triangle wave, the conduction duty cycle waveform of the switch tube Q3 on the A-phase bridge arm, the conduction duty cycle waveform of the switch tube Q1 on the common bridge arm, and the current waveform in the coil. s is the switching period of digital single-cycle control, T offis the duration of the forward off state in each cycle, d is the duty cycle of the coil on state, and i is the current in the magnetic bearing control coil.

[0040] From t0 to t1, within a switching cycle, the upper switch Q1 on the common bridge arm and the upper switch Q3 on the A-phase bridge arm are turned on, while the lower switch Q2 on the common bridge arm and the lower switch Q4 on the A-phase bridge arm are turned off. The load coil current is in the freewheeling state, and the state equation of the coil current is: Formula 1 Where L is the inductance of the magnetic bearing coil; R is the resistance of the magnetic bearing coil; and i is the current of the magnetic bearing coil.

[0041] By solving the state equation, the time domain expression of the coil current can be obtained: Formula 2 Then there is Formula 3 L'Hôpital's rule Formula 4 Depend on Figure 4 , Formula 5 Substituting Equation 5 into Equation 3 and combining it with Equation 4, we can obtain Formula 6 Then the current change during the time period t0 to t1 is Formula 7 At time t1~t2, at time t1, the upper and lower switch tubes of the A-phase bridge arm flip the switch state, the upper switch tube Q3 of the A-phase bridge arm is turned off, and the lower switch tube Q4 of the A-phase bridge arm is turned on. At this time, the switch tube Q1 on the common bridge arm is still turned on, and the inductor current is in an increasing state. Then the incremental equation of the inductor current between t1 and t2 is Formula 8 At t2~t3, at t2, the upper and lower switch tubes of the common bridge arm flip the switch state, the upper switch tube Q1 of the common bridge arm is turned off, and the lower switch tube Q2 of the common bridge arm is turned on. At this time, the upper switch tube Q3 of the A phase bridge arm is still turned off, and the load coil current is in the freewheeling state. Formula 9 Substituting Equation 9 into Equation 3 and combining it with Equation 4, we can get Formula 10 Then the current change during the time period t2~t3 is Formula 11 At time t3~t4, at time t3, the upper and lower switch tubes of the common bridge arm flip the switch state, the upper switch tube Q1 of the common bridge arm is turned on, and the lower switch tube Q2 of the common bridge arm is turned off. At this time, the upper switch tube Q3 of the A phase bridge arm is still turned off, and the inductor current is in an increasing state. Then the incremental equation of the inductor current between t3 and t4 is Formula 12 At time t4~t5, at time t4, the switch tube Q1 on the common bridge arm is turned on, the switch tube Q3 on the A phase bridge arm is turned on, and the load coil current is in the freewheeling state. The current change in the time period from t4 to t5 is Formula 13 Therefore, when the switching cycle is a charging cycle, the change in coil current within one cycle is Formula 14 Assuming that the goal is to track the final value, the actual current value at the end of each switching cycle is required to accurately track the current given in the previous cycle. The actual current change in one switching cycle is Formula 15 Since the time constant of the current inner loop is much smaller than the time constant of the displacement outer loop, it can be considered that i(t0), i(t1), i(t2), i(t3), i(t4) are approximately equal to the average current value within one switching cycle, that is, Formula 16 Substituting Equations 15 and 16 into Equation 14, we can solve for the duty cycle d: Formula 17 The waveform when Δi(k)<0 under the single-cycle unipolar algorithm control is as follows Figure 5 As shown in the figure. From top to bottom, they are the trigger pulse of the switching cycle, the triangle wave, the conduction duty cycle waveform of the switch tube Q3 on the A-phase bridge arm, the conduction duty cycle waveform of the switch tube Q1 on the common bridge arm, and the current waveform in the coil. In the figure, T s is the switching period of digital single-cycle control, T off is the duration of the forward off state in each cycle, d is the duty cycle of the coil on state, and i is the current in the magnetic bearing control coil.

[0042] At t0~t1, at t0, the upper switch tube Q1 of the common bridge arm and the upper switch tube Q3 of the A phase bridge arm are turned on, the lower switch tube Q2 of the common bridge arm and the lower switch tube Q4 of the A phase bridge arm are turned off, and the load coil current is in the freewheeling state. Figure 5 Available Formula 18 Substituting Equation 18 into Equation 3 and combining it with Equation 4, we can obtain Formula 19 Then the current change during the time period t0 to t1 is Formula 20 At time t1~t2, at time t1, the switch states of the upper and lower switches of the common bridge arm are reversed, the upper switch Q1 of the common bridge arm is turned off, and the lower switch Q2 of the common bridge arm is turned on. At this time, the upper switch Q3 of the A phase bridge arm is still turned on, and the inductor current is in a decreasing state. The incremental equation of the inductor current between t2 and t3 is: Formula 21 At t2~t3, the switch tube Q3 on the A-phase bridge arm is turned off, the switch tube Q1 on the common bridge arm is turned off, and the load coil current is in the freewheeling state. Formula 22 Substituting Equation 22 into Equation 3 and combining it with Equation 4, we can obtain Formula 23 Then the current change during the time period t2~t3 is Formula 24 At time t3~t4, at time t3, the switch states of the upper and lower switches of the A-phase bridge arm are reversed, the upper switch Q3 of the A-phase bridge arm is turned on, and the lower switch Q4 of the A-phase bridge arm is turned off. At this time, the lower switch Q2 of the common bridge arm is still turned on, and the inductor current is in a decreasing state. The incremental equation of the inductor current between t3 and t4 is: Formula 25 At t4~t5, the switch tube Q1 on the common bridge arm is turned on, the switch tube Q3 on the A phase bridge arm is turned on, and the load coil current is in the freewheeling state. Formula 26 Therefore, when the switching cycle is a discharge cycle, the change in coil current within one cycle is Formula 27 Assuming that the goal is to track the final value, the actual current value at the end of each switching cycle is required to accurately track the current given in the previous cycle, and the duty cycle d can be solved as Formula 28 Equation 17 is the same as Equation 28, which means that regardless of the polarity of the load current, the duty cycle formula can simultaneously meet the polarity changes of different load currents.

[0043] In a practical circuit, as long as the sampling period, average current, initial output current, and average bus voltage are given, the duty cycle of each load bridge arm can be calculated, so that the output current in each cycle tracks the given current, achieving independent control of the five output currents. Under this control method, the five output currents are not restricted by the switching state of the common bridge arm, and current changes are not mutually constrained, achieving complete decoupled control of the five output currents.

[0044] Example 2 The unipolar single-cycle control mathematical model is used to input the coil current i0 at the initial moment of the single cycle and the current reference value i ref , bus voltage U dc , period T s , load R and inductor L, calculate the duty cycle of a single cycle; The state switching criteria of the charge and discharge cycle are used to input the coil current i0 at the initial moment of a single cycle and the current reference value i ref , load R and inductor L are used to determine the charge and discharge status of a single cycle; The actual current in the current sensor detection and sampling coil is i, and the result is the same as the reference current i ref The difference is input into the controller, and the controller uses the single-cycle control principle to calculate the conduction state and duty cycle of the four switching tubes based on the difference, generates the PWM wave of the corresponding switching tube, and then outputs it to the switching tube in the magnetic bearing switching amplifier.

[0045] The five-phase six-bridge-arm switching power amplifier of the magnetic suspension bearing of the present invention is simulated and analyzed. Table 1 shows the specific parameters of the power amplifier.

[0046] Table 1

[0047] Since the floating waveform of the magnetic bearing is similar to the step response, its step response characteristics are analyzed. In the actual experiment, the current is close to 3A, and the step wave amplitude is set to 3A. Taking phase A as an example, Figure 6 The waveform of the step response of phase A is shown in Figure 1, where ia1 and ia2 are the output currents when the bus voltage is 20V and 40V respectively. After the step response, the output current quickly tracks the given current ira. Figure 6 It can be seen that the response speed is affected by the bus voltage. The larger the bus voltage is, the faster the rise speed is. After reaching the steady state, there is almost no steady-state error. Figure 7 It is the output current of phase A and the local enlarged diagram, ira is the given current of phase A, ia is the output current of phase A, and the output current tracks the given current well.

[0048] Then perform sinusoidal analysis. The simulation parameters of the five sinusoidal currents are as follows: the bus voltage is 80V, and the five given current parameters are shown in Table 2.

[0049] Table 2

[0050] Figure 8 Figure 2 shows the simulation results of five asymmetric sinusoidal output currents. As can be seen from the figure, the five output currents ib, ic, id, and ie can track their respective given currents without obvious distortion or phase lag.

[0051] Compared with the traditional five-phase six-leg switching power amplifier, the improved single-cycle five-phase six-leg switching power amplifier algorithm has the following advantages: 1) The tracking target can be achieved under all static conditions without steady-state error.

[0052] 2) Under dynamic conditions, the improved algorithm can effectively improve the current control accuracy and dynamic response capability of the system.

[0053] Unless otherwise specified, the device components involved in the above embodiments are all conventional device components, and the structural settings, working modes or control modes involved are all conventional settings, working modes or control modes in the art unless otherwise specified.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention and are not limiting. Other modifications or equivalent substitutions made to the technical solution of the present invention by ordinary technicians in this field should be included in the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for optimizing and controlling a multi-arm switching power amplifier circuit, characterized in that: The following steps are involved: Collect circuit data, including: coil current i0 at the initial moment of a single cycle, current reference value iref, bus voltage Udc, period Ts, load R, and inductance L; Establish a single-cycle control mathematical model for a multi-arm switching power amplifier and calculate the duty cycle of a single cycle; Set the state switching criteria of the charge and discharge cycle to determine the charge and discharge state of a single cycle; Calculate the duty cycle value d and output the duty cycle to the corresponding switch tube; Collect the actual current i in the coil and make the difference between the actual current i and the reference current; The conduction state and duty cycle of the load bridge arm switch tube are calculated based on the difference, and a PWM wave of the corresponding switch tube is generated; the PWM wave is output to the switch tube in the magnetic bearing switch power amplifier.

2. The optimization control method of a multi-arm switching power amplifier circuit according to claim 1, characterized in that: The actual current i in the coil is collected by the current sensor.

3. The optimization control method for a multi-arm switching power amplifier circuit according to claim 1, characterized in that: The difference between the actual current i and the reference current is input to the controller, which generates the PWM wave of the corresponding switch tube.

4. The optimization control method for a multi-arm switching power amplifier circuit according to claim 1, characterized in that: The mathematical model of the single-cycle control duty cycle d is: ； Where: L is the inductance of the magnetic bearing coil; R is the resistance of the magnetic bearing coil; iref is the current reference value; i(t0) is the initial value of the single-cycle coil feedback current; Ts is the sampling period, and Udc is the bus voltage.

5. The optimization control method for a multi-arm switching power amplifier circuit according to claim 1, characterized in that: The state switching criteria of the charge and discharge cycle are: when Δi(k) ≥ 0, the coil should be in the charging state in this cycle; when Δi(k) < 0, the coil should be in the discharging state in this cycle; where Δi(k) is the difference between the input current and the output current.

6. The optimization control method for a multi-arm switching power amplifier circuit according to claim 5, characterized in that: The formula for calculating the duty cycle value d is: When Δi(k)≥0, When Δi(k)<0, Where: i(t0) is the initial value of the single-cycle coil feedback current; iref is the current reference value; L is the magnetic bearing coil inductance; R is the magnetic bearing coil resistance; Ts is the sampling period.

7. A multi-bridge switching power amplifier circuit, characterized in that: An optimization control method for a multi-bridge arm switching power amplifier circuit as described in any one of claims 1 to 6 is used for control, and the circuit includes: a power supply, the power supply is electrically connected to a common bridge arm, the common bridge arm is connected in parallel with multiple load bridge arms, each load bridge arm and the common bridge arm has two upper and lower switching tubes connected in series; the upper switching tube and the lower switching tube of the common bridge arm are respectively connected between the upper switching tube and the lower switching tube of each load bridge arm through a capacitor.

8. The multi-arm switching power amplifier circuit according to claim 7, characterized in that: The duty cycle of the common bridge arm is fixed at 0.

5.

9. The multi-arm switching power amplifier circuit according to claim 7, characterized in that: The number of the load bridge arms is five.

10. The multi-arm switching power amplifier circuit according to claim 7, characterized in that: The switch tubes of the load bridge arm and the common bridge arm are both IGBT switch tubes or MOSFET switch tubes.

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