A control method and control system of a chopper converter

Abstract

The application provides a control method and a control system of a chopper converter, the chopper converter comprising a Buck converter and a Boost converter connected in series, the control method comprises the following steps: sampling an output voltage value and an output current value of the Buck converter, performing closed-loop adjustment based on the collected output voltage value and the output current value, outputting a control duty ratio of the Buck converter, and calculating a control duty ratio of the Boost converter based on the control duty ratio of the Buck converter, so as to control the output of the chopper converter; the application has the beneficial effects that the traditional four-order control system is changed into a two-order control system, the difficulty of control parameter adjustment is reduced, the calculation and configuration of the control margin are improved, the system response speed is improved, and the front-stage Boost converter and the rear-stage Buck converter are synchronously controlled in a closed loop, so that the output ripple and the EMI influence are effectively reduced.

Description

Technical Field

[0001] This invention belongs to the field of power electronics technology, and in particular relates to a control method and control system for a chopper converter. Background Technology

[0002] Chopper converters are widely used in the power electronics industry, with Buck converters and Boost converters being the most common. A single-stage Buck or Boost converter can only be used for buck or boost conversion. For applications where the input and output voltage ranges overlap, a Buck-Boost buck-boost converter or two Buck and Boost converters connected in series is required. The former is less commonly used in practical engineering due to issues such as opposite output polarity, complex inductor design, and discontinuous input and output current. The latter, using a Boost+Buck converter in series, effectively avoids these problems and is widely used in fields with high ripple and electromagnetic compatibility requirements.

[0003] In existing technologies, the two-stage series connection of converters leads to complex control methods. The two voltage and current loops form a fourth-order control system, with coupling between the two stages, resulting in complex control algorithms, difficult parameter tuning, slow dynamic response, and high hardware and software resource consumption. Therefore, it is necessary to design a simplified and optimized control method for the two-stage series converter. Summary of the Invention

[0004] The technical problem to be solved by this invention is to provide a control method and control system for a chopper converter, which aims to solve the problems of complex control algorithms, difficult parameter tuning, slow dynamic response, and high hardware and software resource consumption of traditional chopper converters formed by series connection of Buck and Boost converters.

[0005] To solve the above-mentioned technical problems, the present invention is implemented as follows:

[0006] The first aspect of this invention provides a control method for a chopper converter, the chopper converter including a front-stage Boost converter and a rear-stage Buck converter, the front-stage Boost converter and the rear-stage Buck converter being connected in series, the control method comprising:

[0007] The output voltage and output current values ​​of the subsequent Buck circuit are acquired in real time.

[0008] Based on the output voltage value, voltage outer loop control is performed to obtain the current inner loop setpoint;

[0009] According to the current inner loop given value and the output current value, the control duty ratio of the post-stage Buck converter is obtained, and the control duty ratio of the post-stage Buck converter is sent to the control end of the post-stage Buck converter;

[0010] According to the control duty ratio of the post-stage Buck converter, the control duty ratio of the pre-stage Boost converter is obtained, and the control duty ratio of the pre-stage Boost converter is sent to the control end of the pre-stage Boost converter.

[0011] Further, the voltage outer loop control according to the output voltage value includes:

[0012] The output voltage value is subtracted from the target voltage value to obtain a voltage deviation value;

[0013] The voltage deviation value is input into a voltage PI controller for proportional integral adjustment to obtain a first adjustment output value;

[0014] The first adjustment value is summed with the product of the target voltage value and a first proportional coefficient to obtain the current inner loop given value.

[0015] Further, the control duty ratio of the post-stage Buck converter according to the current inner loop given value and the output current value includes:

[0016] The current inner loop given value is subtracted from the output current value to obtain a current deviation value;

[0017] The current deviation value is input into a current PI controller for proportional integral adjustment to obtain a second adjustment output value;

[0018] The second adjustment value is summed with the product of the current inner loop given value and a second proportional coefficient to obtain the control duty ratio of the post-stage Buck converter.

[0019] Further, the control duty ratio of the pre-stage Boost converter according to the control duty ratio of the post-stage Buck converter includes:

[0020] The product of the control duty ratio of the Buck converter and a third proportional coefficient is calculated to obtain the control duty ratio of the pre-stage Boost converter.

[0021] The second aspect of the present application provides a control system of a chopper converter for realizing the control method as described above, characterized in that the control system comprises:

[0022] A voltage and current sampling circuit is used to obtain the output voltage value and the output current value of the post-stage Buck circuit in real time.

[0023] a voltage inner loop control circuit configured to perform voltage outer loop control according to the output voltage value to obtain a current inner loop given value;

[0024] a current outer loop control circuit configured to perform current outer loop control according to the current inner loop given value and the output current value to obtain a control duty ratio of the post-stage Buck converter and transmit the control duty ratio of the post-stage Buck converter to a control end of the post-stage Buck converter;

[0025] a multiplication circuit configured to obtain a control duty ratio of the pre-stage Boost converter according to the control duty ratio of the post-stage Buck converter and transmit the control duty ratio of the pre-stage Boost converter to a control end of the pre-stage Boost converter.

[0026] Further, the voltage inner loop control circuit further comprises a first subtractor, a voltage PI controller and a first adder, wherein,

[0027] the first subtractor is configured to subtract the output voltage value from the target voltage value to obtain a voltage deviation value;

[0028] the voltage PI controller is configured to receive the voltage deviation value, and perform proportional integral adjustment on the voltage deviation value to obtain a first adjustment output value;

[0029] the first adder is configured to sum the first adjustment value and a product of the target voltage value and a first proportional coefficient to obtain the current inner loop given value.

[0030] Further, the current outer loop control circuit further comprises a second subtractor, a current PI controller and a second adder, wherein,

[0031] the second subtractor is configured to subtract the output current value from the current inner loop given value to obtain a current deviation value;

[0032] the current PI controller is configured to receive the current deviation value and perform proportional integral adjustment on the current deviation value to obtain a second adjustment output value;

[0033] the second adder is configured to sum the second adjustment value and a product of the current inner loop given value and a second proportional coefficient to obtain the control duty ratio of the post-stage Buck converter.

[0034] Further, the multiplication circuit is specifically configured to calculate a product of the control duty ratio of the Buck converter and a third proportional coefficient to obtain the control duty ratio of the pre-stage Boost converter.

[0035] The control method and control system of the chopper converter provided in the application have the beneficial effects that, compared with the prior art,

[0036] (1) The whole system only needs to sample the output voltage and current, and only needs to output two closed loops, thereby greatly saving the resources of the control system;

[0037] (2) The fourth-order control system is reduced to a second-order control system, thereby effectively reducing the difficulty of control parameter adjustment and the calculation and configuration of the control margin;

[0038] (3) The front-stage BOOST converter and the rear-stage BUCK converter are synchronously closed-loop controlled, thereby effectively reducing the output ripple and EMI influence;

[0039] (4) Meanwhile, the fourth-order system is reduced to a second-order system through proportional adjustment of the duty cycle, thereby accelerating the system response and reducing the parameter adjustment difficulty. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 is a topological structure schematic diagram of the chopper converter in the embodiment of the application;

[0041] Figure 2 is a flowchart of the control method of the chopper converter in the embodiment of the application;

[0042] Figure 3 is a principle block diagram of the control system of the chopper converter in the embodiment of the application. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical scheme and advantages of the application more clear, the application is further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the application and do not limit the application.

[0044] In the related art, in the control process of the chopper converter composed of the front-stage Boost converter and the rear-stage Buck converter in series, the following problems mainly exist:

[0045] 1) The output voltage and current of the front-stage and rear-stage converters need to be sampled respectively, four feedback quantities and four groups of proportional integral adjusters need to be used, and the control system resource occupation is large;

[0046] 2) In order to ensure the stable output of the rear-stage converter, the output of the front-stage converter is generally fixed voltage output and does not change with the system output requirement, and the energy storage proportion of the inductor changes with the power output, so the design requirement of the inductor is high and the ripple is large;

[0047] 3) The front-stage and rear-stage PWMs are not synchronized, and problems such as high-frequency ripple and EMI are easily generated;

[0048] 4) The four-stage control system is composed of two stages in series, four poles exist, control parameter adjustment is difficult, and stable margin is not easy to calculate and control;

[0049] 5) When multiple converters are used in series and parallel, the control quantity and control difficulty increase sharply, and extension use is inconvenient.

[0050] The first embodiment of the present application provides a control method of a chopper converter, which is used for controlling front and rear stage converters of the chopper converter. Figure 1 As shown in the figure, the circuit topology structure schematic diagram of the chopper converter provided by the present application is shown, and the Boost converter and the Buck converter are connected in series between the voltage input end Uref and the voltage output end Uout; the Buck converter, also known as the voltage reducing chopper, has an output average voltage smaller than the input voltage, and the output voltage and the input voltage have the same polarity. The Boost circuit, also known as the voltage increasing chopper, has an output average voltage greater than the input voltage, and the output voltage and the input voltage have the same polarity. The Buck converter and the Boost converter shown in the figure both include basic switching tubes, inductors, diodes, capacitors and other components.

[0051] As shown in the figure, the control flow schematic diagram provided by the present application includes; Figure 2

[0052] Step 201, real-time acquisition of the output voltage value and the output current value of the rear stage Buck circuit.

[0053] Among them, the output voltage value and the output current value of the rear stage Buck circuit are system representation output values of the chopper circuit, and the voltage sampling circuit and the current sampling circuit can be established respectively to acquire the output voltage value and the output current value in real time. Compared with the traditional voltage and current sampling circuits established for the Buck converter and the Boost converter respectively, the present embodiment reduces the four-stage control system to two-stage control, which can effectively reduce the difficulty of control parameter adjustment and the calculation and configuration of control margin.

[0054] Step 202, voltage outer loop control according to the output voltage value, and output current inner loop given value.

[0055] Among them, after sampling the output voltage value Uout, the output voltage value Uout and the target voltage value are input into the first subtracter to obtain the voltage deviation value; the target voltage value is the chopper input voltage Uref, and the first subtracter includes a positive input end and a negative input end. The positive input end of the first subtracter is used for receiving the target voltage value Uref, and the negative input end is used for receiving the output voltage value Uout. The calculation formula of the voltage deviation value is:

[0056] Voltage deviation value = target voltage value Uref - output voltage value Uout;​

[0057] Further, the output end of the first subtractor is connected with the input end of the voltage PI controller; the voltage deviation value is taken as the input of the voltage PI controller. The PI controller is a proportional-integral regulator, and the integral action means that the output of the regulator is proportional to the integral of the deviation of the input over time. The integral regulation has two characteristics: one is that the output of the regulation is related to the time when the deviation exists, and the output of the integral regulator will increase with time as long as the deviation exists, until the deviation is eliminated. The other is that the integral action is slow, and when the deviation just appears, the regulation is weak and cannot overcome the influence of the disturbance in time, so that the dynamic deviation of the regulated parameter increases. The first regulation output value is obtained through the voltage PI controller.

[0058] After the voltage PI controller obtains the first regulation output value, the current inner loop given value is calculated according to the first regulation output value. The present application provides a first adder, the first input end of the first adder is connected with the output end of the voltage PI controller, for receiving the first regulation output value, the second input end of the first adder is used for receiving the product of the target voltage value and the first proportional coefficient, and the value obtained by summing the first regulation output value and the product of the target voltage value and the first proportional coefficient through the first adder is the output current inner loop given value, which is further taken as the reference value of the output current value. The calculation formula of the current inner loop given value provided by the present application is:

[0059] Iref=Uref·K1+PI_out1

[0060] Wherein, Iref is the current inner loop given value, Uref is the target voltage value, K1 is the first proportional coefficient, the first proportional coefficient K1 has the function of reducing the regulation range of the PI controller and accelerating the response speed, and the range is 0-1. After increasing the value range of K1, the response speed of the voltage PI controller is fast and the regulation range is small. After reducing the value range of K1, the response speed of the voltage PI controller is slow and the regulation range is large.

[0061] Step 203, according to the current inner loop given value and the output current value, the control duty ratio of the rear-stage Buck converter is outputted, and the control duty ratio of the rear-stage Buck converter is delivered to the control end of the rear-stage Buck converter.

[0062] Wherein, the current inner loop given value and the output current value are inputted into the second subtractor, and the current inner loop given value and the output current value are subtracted by the second subtractor to obtain the current deviation value. Specifically, the second subtractor includes a positive input end and a negative input end, the positive input end of the second subtractor is connected with the output end of the first adder, for receiving the current inner loop given value, and the negative input end of the second subtractor is connected with the current sampling circuit, for receiving the output current value. Wherein, the calculation formula of the current deviation value is:

[0063] The current deviation value = the current inner loop given value Iref - the current output value Iout

[0064] Further, the output end of the second subtractor is connected to the input end of the current PI controller, and the obtained current deviation value is taken as the input of the current PI controller, and the current PI controller outputs a second adjustment output value after proportional integral adjustment.

[0065] After the current PI controller obtains the second adjustment output value, the control duty cycle of the post-stage Buck converter is calculated according to the second adjustment output value, and the duty cycle refers to the proportion of the energization time to the total time in one pulse cycle. The output of the Buck converter is controlled by adjusting the size of the control duty cycle.

[0066] In the embodiment, a second adder is further provided, the first input end of the second adder is connected to the output end of the voltage PI controller, and is used for receiving the first adjustment output value, the second input end of the second adder is used for receiving the product of the current inner loop given value and the second proportional coefficient, and the value obtained by summing the first adjustment output value and the product of the target voltage value and the first proportional coefficient through the second adder is the control duty cycle of the Buck converter. The calculation formula of the control duty cycle of the post-stage Buck converter provided by the application is as follows:

[0067] D2 = Iref K2 + PI_out2

[0068] Wherein, D2 is the control duty cycle of the post-stage Buck converter, Iref is the current inner loop given value, Uref is the target voltage value, and K2 is the second proportional coefficient. Similarly, the second proportional coefficient K2 has the function of reducing the adjustment range of the current PI controller and accelerating the response speed, and the range is 0-1. After increasing the value range of K2, the response speed of the current PI controller is fast, and the adjustment range is small. After reducing the value range of K2, the response speed of the current PI controller is slow, and the adjustment range is large.

[0069] Step 204, according to the control duty cycle of the post-stage Buck converter, the control duty cycle of the pre-stage Boost converter is obtained, and the control duty cycle of the pre-stage Boost converter is sent to the control end of the pre-stage Boost converter.

[0070] In the embodiment, the control duty cycle of the front-stage Boost converter is obtained by using the control duty cycle of the rear-stage Buck converter. Since the control duty cycle of the front-stage Boost converter is obtained based on the control duty cycle of the rear-stage Buck converter, the front-stage BOOST converter and the rear-stage BUCK converter are synchronous closed-loop controlled (voltage outer loop and current inner loop control), and the output ripple and EMI influence can be effectively reduced. The calculation formula of the control duty cycle of the front-stage Boost converter is:

[0071] D3=D2*K3

[0072] wherein D3 is the control duty cycle of the front-stage Boost, D2 is the control duty cycle of the rear-stage Buck converter, and K3 is the third proportional coefficient. The K3 coefficient is adjusted to reduce the size of the inductance and capacitance energy storage. When the K3 coefficient is relatively small, the front-stage Boost inductance energy storage is small, and more energy is provided by the input battery, so that the inductance design difficulty can be reduced, and the ripple is small.

[0073] The control method of the chopper converter provided in the embodiment changes the traditional four-order control system into a two-order control system, reduces the difficulty of control parameter adjustment, and improves the system response speed. Moreover, the front-stage BOOST converter and the rear-stage BUCK converter are synchronous closed-loop controlled, and the output ripple and EMI influence can be effectively reduced.

[0074] The second embodiment of the application provides a control system for implementing the control method provided in the first embodiment.

[0075] The voltage and current sampling circuit is used for acquiring the output voltage value and the output current value of the rear-stage Buck circuit in real time.

[0076] The voltage inner loop control circuit is used for performing voltage outer loop control according to the output voltage value, and outputting a current inner loop given value.

[0077] The current outer loop control circuit is used for outputting the control duty cycle of the rear-stage Buck converter according to the current inner loop given value and the output current value, and delivering the control duty cycle of the rear-stage Buck converter to the control end of the rear-stage Buck converter.

[0078] The multiplication circuit is used for obtaining the control duty cycle of the front-stage Boost converter according to the control duty cycle of the rear-stage Buck converter, and delivering the control duty cycle of the front-stage Boost converter to the control end of the front-stage Boost converter.

[0079] The voltage inner loop control circuit further includes a first subtractor 10, a voltage PI controller 20 and a second adder 60, wherein,

[0080] The first subtractor 10 is used to subtract the output voltage value from the target voltage value to obtain the voltage deviation value;

[0081] The voltage PI controller 20 is used to receive the voltage deviation value, perform proportional-integral regulation on the voltage deviation value, and obtain the first regulated output value.

[0082] The second adder 60 is used to sum the product of the first adjustment value, the target voltage value, and the first proportional coefficient to obtain the current inner loop setpoint.

[0083] The outer current control circuit further includes: a second subtractor 40, a current PI controller 50, and a second adder 60.

[0084] The second subtractor 40 is used to subtract the current inner loop setpoint from the output current value to obtain the current deviation value.

[0085] The current PI controller 50 is used to receive the current deviation value and perform proportional-integral adjustment on the current deviation value to obtain the second regulated output value.

[0086] The second adder 60 is used to sum the product of the second adjustment value, the current inner loop setpoint, and the second proportional coefficient to obtain the control duty cycle.

[0087] Specifically, the multiplication circuit is used to calculate the product of the control duty cycle of the Buck converter and the third proportional coefficient to obtain the control duty cycle of the preceding Boost converter.

[0088] In summary, the specific structural relationship of the control system can be obtained. The control system includes: a current sampling circuit, a voltage sampling circuit, a first subtractor 10, a voltage PI controller 20, a second adder 6030, a second subtractor 40, a current PI controller 50, a second adder 60, and a multiplication circuit.

[0089] The voltage sampling circuit has its input connected to the output of the Buck converter, and its output connected to the negative input of the first subtractor 10. The positive input of the first subtractor 10 receives the target voltage value. The output of the first subtractor 10 is connected to the input of the voltage PI controller 20. The output of the voltage PI controller 20 is connected to the first input of the second adder 6030, and its second input receives the product of the target voltage value and the first proportional coefficient. The output of the second adder 6030 is connected to the positive input of the second subtractor 40. The input of the current sampling circuit is connected to the output of the Buck converter. The output of the current sampling circuit is connected to the negative input of the second subtractor 40. The output of the second subtractor 40 is connected to the input of the current PI controller 50. The output of the current PI controller circuit is connected to the first input of the second adder 60. The second input of the second adder 60 is used to receive the product of the inner current loop setpoint and the second proportional coefficient. The output of the second adder 60 is connected to the control terminal of the subsequent Buck circuit and, through the product circuit, to the control terminal of the preceding Boost circuit. See Appendix for details. Figure 3 The schematic diagram shown.

[0090] The control system of the chopper circuit provided in this embodiment can realize the control method in the first embodiment, thereby changing the control of the chopper from a traditional fourth-order control system to a second-order control system. This reduces the difficulty of control parameter tuning, as well as the calculation and configuration of control margin, and improves the system response speed. Furthermore, the synchronous closed-loop control of the front-end BOOST converter and the rear-end BUCK converter effectively reduces the output ripple and EMI impact.

[0091] The terms "first," "second," etc., used here only indicate the distinction in their names and do not imply any difference in their importance or position.

[0092] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A control method for a chopper converter, characterized in that, The chopper converter is used to construct a second-order control system, and includes a front-stage Boost converter and a rear-stage Buck converter, wherein the front-stage Boost converter and the rear-stage Buck converter are connected in series, and the control method includes: The output voltage and output current values ​​of the subsequent Buck converter are acquired in real time. The voltage deviation value is obtained by subtracting the output voltage value from the target voltage value. The voltage deviation value is input into a voltage PI controller for proportional-integral adjustment to obtain a first regulated output value. The product of the first regulated output value and the target voltage value and the first proportional coefficient is summed to obtain the current inner loop setpoint. The difference between the inner current loop setpoint and the output current value is used to obtain the current deviation value; The current deviation value is input into a current PI controller for proportional-integral adjustment to obtain a second adjusted output value. The control duty cycle of the subsequent Buck converter is calculated by summing the product of the second regulated output value and the product of the current inner loop setpoint and the second proportional coefficient, and the control duty cycle of the subsequent Buck converter is sent to the control terminal of the subsequent Buck converter. The control duty cycle of the preceding Buck converter is calculated by multiplying the control duty cycle of the preceding Buck converter by the third proportional coefficient, and the control duty cycle of the preceding Buck converter is then sent to the control terminal of the preceding Buck converter.

2. A control system for a chopper converter, used to implement the control method as described in claim 1, characterized in that, The control system includes: A sampling circuit is used to acquire the output voltage and output current values ​​of the subsequent Buck converter in real time. The voltage outer loop control circuit is used to perform voltage outer loop control based on the output voltage value to obtain the current inner loop setpoint; The current inner loop control circuit is used to obtain the control duty cycle of the subsequent Buck converter according to the current inner loop setpoint and the output current value, and to send the control duty cycle of the subsequent Buck converter to the control terminal of the subsequent Buck converter. The multiplication circuit is used to obtain the control duty cycle of the preceding Boost converter based on the control duty cycle of the following Buck converter, and to send the control duty cycle of the preceding Boost converter to the control terminal of the preceding Boost converter.

3. The control system for the chopper converter according to claim 2, characterized in that, The voltage outer loop control circuit further includes a first subtractor, a voltage PI controller, and a first adder, wherein... The first subtractor is used to subtract the output voltage value from the target voltage value to obtain a voltage deviation value; The voltage PI controller is used to receive the voltage deviation value, perform proportional-integral adjustment on the voltage deviation value, and obtain a first adjusted output value; The first adder is used to sum the product of the first regulated output value, the target voltage value, and the first proportional coefficient to obtain the current inner loop setpoint.

4. The control system for the chopper converter according to claim 3, characterized in that, The current inner loop control circuit further includes: a second subtractor, a current PI controller, and a second adder, wherein... The second subtractor is used to subtract the given value of the inner current loop from the value of the output current to obtain the current deviation value; The current PI controller is used to receive the current deviation value and perform proportional-integral adjustment on the current deviation value to obtain a second adjusted output value; The second adder is used to sum the product of the second regulated output value and the product of the current inner loop setpoint and the second proportional coefficient to obtain the control duty cycle of the subsequent Buck converter.

5. The control system for the chopper converter according to claim 4, characterized in that... The multiplication circuit is specifically used for: The control duty cycle of the preceding Boost converter is obtained by multiplying the control duty cycle of the subsequent Buck converter by the third proportional coefficient.

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