CN115395777A - Boost converter dynamic performance index optimization method based on hierarchical switching control - Google Patents
Boost converter dynamic performance index optimization method based on hierarchical switching control Download PDFInfo
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- CN115395777A CN115395777A CN202210853760.1A CN202210853760A CN115395777A CN 115395777 A CN115395777 A CN 115395777A CN 202210853760 A CN202210853760 A CN 202210853760A CN 115395777 A CN115395777 A CN 115395777A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
- H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
- H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
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Abstract
The invention aims to provide a method for optimizing dynamic performance indexes of a Boost converter based on hierarchical switching control for the Boost converter, and belongs to the technical field of power electronics. The method divides the working state of the Boost converter into two conditions for different control: during the transient period, adopting an HSC method for control, namely calculating the on-off running time of a switching tube by using a state plane track, and after obtaining the total running time of the dynamic process, respectively carrying out two on-off operations to realize the balance between recovery time and voltage deviation; and after the output voltage reaches the desired voltage, switching to the conventional PI control.
Description
Technical Field
The invention belongs to the technical field of power electronics, and particularly relates to a dynamic performance index optimization method of a boost converter based on hierarchical switching control.
Background
In recent years, research on power conversion has been rapidly developed due to energy crisis. The power conversion has four basic conversion methods, i.e., an alternating current-to-direct current conversion (AC/DC), a direct current-to-direct current conversion (DC/DC), a direct current-to-alternating current conversion (DC/AC), and an alternating current-to-alternating current conversion (AC/AC). Among them, the DCDC converter is a power processing device that changes the voltage level of a direct current power supply, and is present in most power conversion systems or devices, such as: consumer electronics, high voltage direct current systems, and direct current micro-grids. The Boost converter is a typical topology of a DCDC converter, and is not only an important component of a switching power supply, but also the core of most battery-powered applications.
The boost of the boost converter is achieved by switching between two linear circuits each switching cycle. When the switch is on, the inductance in the circuit stores energy and transfers the stored energy to the load during off, resulting in a phase lag phenomenon commonly referred to as non-minimum phase (NMP) behavior, which is reflected by the presence of the right half-plane zero point (RHPZ) in the transfer function controlling the input duty cycle to the output voltage. This non-minimum phase (NMP) characteristic limits the closed loop bandwidth of the system complicating the control task and increasing the difficulty of boost converter control. Other difficulties in controlling boost converters are their non-linearity, the interdependent state variables in the boost converter topology, input and load disturbances, and parameter uncertainty. Therefore, from the viewpoint of control, the boost converter is much more difficult to control than other DCDC converters.
In the past decades, various control schemes have been developed to enhance the regulation performance of Boost converters in response to the increasing need to obtain a stable output voltage under large load variations and input disturbances. Common analytical methods are the mean model method (AMM) and the Geometric Graph Method (GGM).
Aiming at the fact that a Boost converter is a nonlinear time-varying system, a small signal model is obtained through linearization around an accurate working point of a state space average model, and a classical control theory is introduced on the basis of the small signal model to design a controller. The linear controller is simple and convenient in design and easy to implement, but cannot process system parameter changes and large-signal transient changes; whereas multi-loop current mode control uses the input inductor current for inner current loop regulation with high crossover frequency, and the output voltage is regulated by the slower outer voltage loop. The design of such controllers considers different loop gains and specific target operating points to evaluate the system performance, greatly improving the dynamic response of the system, but designing a dual-loop controller has great challenges, especially for the topology of high-order converters.
The controller is designed based on an average model method regardless of a small signal model or a multi-loop mode, and the controller has excellent performance only at a certain operating point, and once the system deviates from a balance point, the interference suppression capability of the designed controller is reduced. In order to effectively cope with the changes of the input power supply voltage of the Boost converter and the system parameters, a geometric figure method (GGM) is considered.
Boundary control is a geometry-based control method, and a commonly used boundary control method is Sliding Mode Control (SMC). SMC exhibits stable output voltage regulation in the presence of input voltage and output load disturbances, with faster dynamic response and less overshoot and undershoot than conventional PI control. However, the regulated output voltage of the SMC has high frequency ripple due to the slip-mode plane crossing. In addition, high-frequency vibration caused by the vibration on the switch surface is difficult to eliminate, and unmodeled dynamics of the system is easy to excite.
Most of the controllers designed above, whether using the Average Model Method (AMM) or the Geometric Graph Method (GGM), can achieve the minimum recovery time, but unfortunately, the minimum output voltage deviation and the minimum recovery time cannot be achieved at the same time for the Boost converter as for the buck converter, and therefore, it is meaningful to take the minimum voltage deviation and the minimum recovery time into consideration.
Disclosure of Invention
The dynamic performance index optimization method of the boost converter based on the hierarchical switching control is provided by comprehensively considering the voltage deviation and the recovery time. Different from the traditional boundary control based on a natural track as a switch surface, a transient working point is selected in the dynamic process from light load to heavy load jump, the opening track of the working point is a secant of the turn-off track of the transient working point, and the balance of voltage deviation and recovery time is realized through Hierarchical switching control. And in the steady-state process, a double-loop PI is introduced, and the control structure block diagram of the double-loop PI is shown in figure 1.
1. Hierarchical switching control based on equalization between boost converter output voltage undershoot and response time, comprising the steps of:
and 2, when the load jumps from light load to heavy load, selecting a transient working point in a dynamic process to comprehensively consider two indexes of output voltage undershoot and recovery time, and calculating the total time of switching on and off of each stage of MOSFET switching tube and combining a natural track to reach a target working point, so that the system can reach a steady state theoretically only by two switching actions.
And 3, when the circuit is in a stable state, using a double-loop PI to control.
Further, the topology of the Boost converter includes: the circuit comprises an inductor (L), a capacitor (C), a switching tube (S1) and a diode (D1); the drain electrode of the switching tube (S1) is connected with one end of the inductor, and the source electrode of the switching tube (S1) is connected with the negative electrode of the input power supply; the anode of the diode (D1) is connected with one end of the inductor and the drain of the switch tube (S1), the cathode of the diode (D1) is connected with one end of the output capacitor (C), and the other end of the output capacitor (C) is connected with the negative electrode of the power supply.
Further, the output voltage of the Boost converter cannot be negative due to the presence of diodes in the circuit topology.
Further, the operation mode of the Boost converter during the steady state is a Continuous Conduction Mode (CCM).
Further, the control method is suitable for the condition that the load disturbance is small, namely the disturbance enables the output voltage of the converter not to be 0.
In summary, due to the adoption of the technical scheme, the invention has the beneficial effects that:
1. the transient control method based on the natural track provided by the invention is switched to the proposed control method when the load is disturbed, the on-off time of each level of switching tube is calculated by using state plane analysis, and the state variable reaches the target working point in the shortest time on the basis of reducing the stress of the component by combining the natural track of the boost converter.
Drawings
Fig. 1 is a block diagram of the control method of the present invention.
FIG. 2 is a simplified circuit schematic of a Boost converter;
wherein, (a) is a topological structure chart; (b) turning on an equivalent circuit diagram for the switching tube; and (c) is an equivalent circuit diagram of the switch tube.
Fig. 3 is a normalized trace diagram of the turn-on and turn-off of the MOSFET in the Boost converter.
FIG. 4 is a simplified optimal time dynamics control diagram of the present invention when the load is from light load to heavy load;
wherein, (a) is a phase trace diagram of output voltage and inductive current, (b) is an output voltage waveform, and (c) is an inductive current waveform.
FIG. 5 is a simulation diagram of the variation of the waveform of the inductive current when the control method of the present invention is used during the jump of the load;
wherein, (a) is an inductive current simulation diagram; and (b) is an output voltage simulation graph.
Fig. 6 is a simulation waveform diagram of PI control.
Wherein, (a) is an inductive current simulation diagram; and (b) is an output voltage simulation graph.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the following embodiments and accompanying drawings.
The control method of the invention is designed for a Boost converter with a non-minimum phase (NMP) system, and the simplified circuit schematic diagram of the Boost converter is shown in fig. 1. The circuit topology structure is as shown in fig. 1 (a), and includes: the circuit comprises an inductor (L), a capacitor (C), a switching tube (S1) and a diode (D1); the drain electrode of the switching tube (S1) is connected with one end of the inductor, and the source electrode of the switching tube (S1) is connected with the cathode of the input power supply; the anode of the diode (D1) is connected with one end of the inductor and the drain of the switching tube (S1), the cathode of the diode (D1) is connected with one end of the output capacitor (C), and the other end of the output capacitor (C) is connected with the negative electrode of the power supply; the output capacitor (C) is connected with the load (R) in parallel. Fig. 1 (b) and fig. 1 (c) are equivalent circuit diagrams of switching on or off of the switching tube MOSFET, respectively. When the switch tube MOSFET is switched on, the inductor current stores energy, and when the switch tube MOSFET is switched off, the energy stored in the inductor is transmitted to the load.
For the above-described transformer, in order to eliminate the dimension of the state variable to obtain generality, the variable is subjected to normalization processing,
wherein, V r Is a reference voltage, f o In order to be the natural frequency of the frequency,
l and C are respectively inductance and capacitance, Z o In order to be the characteristic impedance,
when the switching tube is turned on (u = 1) and turned off (u = 0) (u refers to the state of the MOSFET switching tube and is also the control input of the system), according to KCL and KVL laws, the state equations of the inductor current and the output voltage are as follows,
wherein, V cc Is the input voltage, i L Is the inductive current, v o Is the output voltage;
assuming that no power loss occurs during the operation of the Boost converter, the input power is equal to the output power, and the load line is defined as follows:
when the target operating voltage (output voltage equal to desired voltage) is normalized, the result is v on,target ＝1，
The target operating point of the converter is (v) on , target ,i Ln,target ) The determination can be made according to (3) and (4).
Obtaining the phase tracks of the normalized inductive current and the output voltage by the ordinary differential equation when the switching tube is switched on and off at the target working point:
wherein, when u =0, the phase locus of the inductor current and the output voltage is (V) ccn ,i on ) As a circle center, with a desired working point
To the center of a circle (V) ccn ,i on ) A circle with a radius; and when u =1, the phase locus of the inductor current and the output voltage is a passing point
Has a slope of
Is measured. As shown in fig. 2, the switching-on and switching-off tracks of the Boost converter are tangent at the target working point, and ideally, when the system reaches a steady state, the Boost converter performs high-frequency switching-on and switching-off near the target working point.
If the output voltage cannot be negative, and the Boost converter operates in Continuous Conduction Mode (CCM) during steady state.
A phase plane secant trajectory control method of a Boost converter is shown in a structural block diagram of FIG. 3 and comprises the following steps:
and 2, when the load jumps from light load to heavy load, selecting a transient working point in a dynamic process to comprehensively consider two indexes of output voltage undershoot and recovery time, and reaching a target working point based on a natural track of the on and off of the MOSFET switching tube. Therefore, theoretically, only two switches are operated to make the system reach a steady state, and the specific process is shown in fig. 4.
As shown in fig. 4.A, when the load changes from light load to heavy load, the operating point 3 is the steady-state point at the next moment, and the operating point 1 is the initial state point of the load jump process and is also the steady-state operating point at the last moment. To comprehensively consider the two indicators of voltage undershoot and recovery time, a transient operating point 2' is selected from the operating points 1 and 3. According to the derived on-off trajectories of the boost converter in the previous section, we can obtain that the on-off trajectories at the working point 3 are respectively:
wherein i on3 Is the load current at operating point 3.
Since the transient operating point 2 'is the middle point between the operating points 1 and 3, the transient operating point 2' has the coordinates of
The on and off trajectories at the transient point 2' are respectively:
according to the formula 6,8, by comparing the slope magnitudes of the open traces at the working point 3 and the transient point 2, the relationship between the slope magnitudes is:
so, taking the transient operating point 2' as the initial point, the straight line of the slope of the on-trace at the operating point 3 intersects the off-trace at the transient operating point 2, i.e.: line 2'5 is a secant of the shutdown trajectory at transient operating point 2'.
Fig. 4.a shows a phase trace of the inductor current and output voltage for the proposed two-stage switching control, and fig. 4.b and 4.c show the output voltage and inductor current, respectively, as a function of time. From fig. 4, we can calculate the theoretical dynamic response time. The specific calculation is as follows:
the turn-on trajectory from the initial operating point 1 to the transient point 4 is:
the turn-off trajectory from the transient point 4 to the transient operating point 2' is given by equation 9, and the coordinates of the transient point 4 obtained by combining equations 9 and 11 are:
wherein:
the on-time from the initial operating point 1 to the transient point 4 is therefore:
wherein
Similarly, the turn-on trajectory from the transient operating point 2' to the transient point 5 is:
the turn-off trajectory from the transient point 5 to the operating point 3 is equation 7. Simultaneous equations 7 and 15 yield the coordinates of the transient point 5 as:
wherein:
the on-time from transient point 2 to transient point 5 is therefore:
according to geometric analysis, the turn-off time from transient point 4 to transient point 2 is:
similarly, the turn-off time from the transient point 5 to the steady-state point 3 is:
the total time of switching on and off of the first stage and second stage switching control is:
the dynamic response time after the proposed two-stage switching control normalization when the load jumps from light load to heavy load is obtained by combining the formulas 14,20,21 and 22 as follows:
t n ＝t on14 +t offn42 +t on25 +t offn53 (23)
based on the analysis of the above theory, we give the following two-stage switching control law:
where T is the switching period of the PWM waveform.
And 3, when the circuit is in a stable state, using a double-ring PI to control.
Example 1
When the control method is adopted to carry out control simulation on the Boost converter, when the circuit parameters of the converter are shown in the table 1, the changes of the inductive current and the output voltage in the dynamic process of the resistance from 2A to 4A (light load to heavy load) are shown in the figure 5. As can be seen from the above figures, the output voltage dynamic recovery time is about 40.276us when the load transitions from 2A to 4A. The desired operating point of the output voltage is reached and the voltage undershoot maximum is about 29.8V with a voltage deviation of about 0.2V. After reaching the operating point, the system switches to the dual-loop PI controller, and the whole dynamic process is about 10ms due to switching oscillation.
FIG. 6 is a graph of output voltage and inductor current based on a dual loop PI with a load from 15 Ω To 7.5 Ω When the change is carried out, the expected working point is reached in about 15ms, the voltage undershoot maximum value is about 26.5V, and the voltage deviation is about 3.5V.
In combination with the above analytical methods, we have found that the hierarchical switching control proposed herein better reflects the balance between recovery time and voltage deviation.
TABLE 1
| Parameter(s) | Value of |
| V cc | 15V |
| V o | 30V |
| f s | 200KHz |
| L | 22 μ H |
| C | 330 μ F |
| D | 0.5 |
| R | 15Ω |
While the invention has been described with reference to specific embodiments, any feature disclosed in this specification may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise; all of the disclosed features, or all of the method or process steps, may be combined in any combination, except mutually exclusive features and/or steps.
Claims (5)
1. A dynamic performance index optimization method of a boost converter based on hierarchical switching control is characterized by comprising the following steps:
step 1, judging whether a circuit of a Boost converter is in a steady state or a transient state, and if the circuit is in the transient state, entering a step 2; otherwise, entering step 3;
and 2, when the load jumps from light load to heavy load, selecting a transient working point in a dynamic process to comprehensively consider two indexes of output voltage undershoot and recovery time, and calculating the total time of switching on and switching off of each stage of MOSFET switching tube and combining a natural track to reach a target working point, so that the system can reach a steady state theoretically only by two switching actions.
And 3, when the circuit is in a stable state, using a double-ring PI to control.
2. The hierarchical switching control method according to claim 1, wherein the topology of the Boost converter comprises: an inductor, a capacitor, a switching tube and a diode; the drain electrode of the switching tube is connected with one end of the inductor, and the source electrode of the switching tube is connected with the negative electrode of the input power supply; the anode of the diode is connected with one end of the inductor and the drain of the switching tube, the cathode of the diode is connected with one end of the output capacitor, and the other end of the output capacitor is connected with the negative electrode of the power supply.
3. The hierarchical switching control method according to claim 1, wherein an output voltage of the Boost converter cannot be negative.
4. The hierarchical switching control method according to claim 1, wherein an operation mode of the Boost converter during a steady state is a continuous conduction mode.
5. The hierarchical switching control method according to claim 1, wherein the load disturbance causes the output voltage of the converter to be other than 0.
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