CN115940652B - Variable circle center average geometric control phase-shifting soft start system and method - Google Patents
Variable circle center average geometric control phase-shifting soft start system and method Download PDFInfo
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Abstract
The invention provides a variable center average geometric control phase-shifting soft start system and a variable center average geometric control phase-shifting soft start method. The controller calculates the current average value of the output capacitor in the first half period of the starting process of the LLC resonant converter through a time domain analysis method, and further calculates the equivalent inductance and the equivalent angular frequency; constructing a track plane coordinate system by taking the voltage of the output capacitor and the current average value thereof as an X axis and a Y axis, setting a limit value of the current average value of the output capacitor, and calculating the number of arcs of the starting track, the circle center of each arc and the running time; and sequentially assigning the X-axis coordinates of the circle centers of all the sections of the circular arcs to voltage gain, calculating the phase shift angle of each section of the circular arcs through a time domain analysis method, and generating a switch control signal of the inverter by combining the running time of each section of the circular arcs to perform inversion control. The arc track is positioned in a section in which the average value of the output capacitance current is close to the limit value and the voltage rises quickly, so that the starting efficiency is high; and the running time of the arc tracks is equal, so that the calculated amount is greatly reduced, and high-speed sampling is not needed.
Description
Technical Field
The invention belongs to the technical field of control of resonant converters in power electronic devices, and particularly relates to a variable circle center average geometric control phase-shifting soft start system and method.
Background
With the continuous development of new energy technology, the LLC resonance type converter becomes a high-efficiency DC-DC converter due to the soft switching characteristic and higher power density which are easy to realize, and has wide application in the fields of power electronic energy storage devices, electric automobile charging, switching power supplies and the like. However, the input impedance of the resonant cavity of the resonant converter is very small, and the voltages at two ends of the filter capacitor are very low during starting, which is equivalent to short circuit, so that the phenomenon of inrush current and output voltage overshoot exists during the power-on starting process, and especially the problem of inrush current in a high-power converter is more remarkable, and serious problems such as circuit burning and the like can be caused.
In order to reduce the starting rush current and simultaneously enable the output voltage to reach the rated value smoothly as soon as possible, three types of soft start control methods appear: the method comprises the steps of frequency-reducing soft start, phase-shifting soft start and optimal track control soft start.
The characteristics that the output voltage of the LLC resonant converter is reduced along with the increase of the switching frequency of the primary side inverter and the increase of the phase shift angle between the left bridge arm and the right bridge arm are respectively utilized in the frequency-reducing soft start and the phase shift soft start, the operation is started at the initial stage of starting at a phase shift angle (fixed switching frequency) which is several times the rated frequency or larger, and then the frequency-reducing or phase shift angle is gradually reduced until the rated steady state is reached. However, the high switching frequency of the soft start of the down-conversion is inconvenient for the digital controller to realize, resulting in over-design of the magnetic element and the switching tube and increased cost; and because the voltage is slow to decrease with increasing frequency, the voltage reducing capacity of increasing frequency is limited, so that a larger starting current still exists. The phase-shifting soft start repeatedly tests the phase-shifting angle meeting the current limit on a switch-by-switch cycle basis according to the time domain equivalent model of the converter, and the calculated amount is large. The optimal track soft start is also to calculate the moment of switching the switching frequency or the switching on and off time of each switch according to the time domain equivalent model of the converter, so the switching frequency is not fixed, the track exceeding control is caused by the delay of the control loop, high-speed sampling and control are needed, and the cost is high.
In order to achieve a low cost soft start at a fixed switching frequency, the prior art proposes an average geometry control method for a half-bridge LLC converter. The method equivalent the resonant network of the primary side of the converter to an average inductance L AM Forms a second-order equivalent circuit with the output capacitor C, and controls the average current i of the C in the starting process CAM And output voltage V o Limiting the start-up surge current. After all parameter variables are processed by per unit, when the half-bridge inverter outputs at resonance frequency and zero phase shift angle, V o 、i CAM Is a circular arc with (1, 0) as a center and the distance between the initial state coordinates and (1, 0) as a radius, to i CAM Ending when the current limit is reached; when the half-bridge inverter stops outputting, V o 、i CAM Is a circular arc with (-1, 0) as the center and the distance between the initial state coordinates and (-1, 0) as the radius, to i CAM Ending when the drop reaches 0. Track circular arcs of output and stop of the half-bridge inverter are alternately switched, and the time of normal output and stop is calculated and controlled section by section, so that i is achieved CAM Continuously rising and falling but the peak value does not exceed the limit value, V o Continuously rising. However, this method has the following drawbacks:
the running track is in dV with more running tracks in the starting process o /di CAM In a very small interval, the charging current average value of the output capacitor repeatedly oscillates between zero and the current limit value, V o The rise is slower, the efficiency of the start-up process is lower and the fluctuation is larger.
The running time of each section of arc in the starting process is a variable quantity, the calculation is needed one by one, and the calculated quantity is large; the output and stop time calculation error of the inverter is easy to cause current overrun, and the requirements on circuit parameter accuracy and calculation precision are high.
The invention provides an average geometric control phase-shifting soft start method which is applicable to a full-bridge LLC resonant converter and has the advantages of rapider speed and smaller calculated quantity.
Disclosure of Invention
The invention aims to provide an average geometry soft start method with fixed switching frequency, low cost and small calculated amount for a full-bridge LLC resonant converter. The method adopts fixed frequency phase shift control to the primary side inverter, establishes a second-order equivalent circuit of the converter, and indirectly controls the peak value of the primary side input current by controlling the average value of the output capacitance current. And constructing a track plane coordinate system by taking the voltage of the output capacitor and the current average value thereof as an X axis and a Y axis, wherein the starting track consists of a plurality of sections of circular arcs which are close to the current limit value, and the circle center of each section of circular arc corresponds to a phase shift angle. The circle center of the arc gradually approaches to the steady state (1, 0) from the vicinity of the (0, 0) in starting, the radius does not exceed the current limit, and the phase shift angle is reduced; until the end of startThe transition to the steady state is completed by adopting a section of arc track with (-1, 0) as the center and the radius of 2. The running track of the method is mostly in the range of |dV o /di CAM The interval with large I, so the voltage rising speed is faster; meanwhile, the operation time of most of arcs of the first section and the last section is equal, the calculated amount is greatly reduced, high-speed sampling is not needed, and the method is easy to realize.
In addition, it is known to analyze the switching state of an LLC resonant converter using time domain analysis, write a circuit state equation, derive a calculation model, calculate the voltage and current of the circuit from the phase shift angle, and calculate the phase shift angle from the voltage gain.
The technical scheme of the system of the invention is a variable center average geometric control phase-shifting soft start system, which comprises:
the device comprises a controller, an inverter, a resonant capacitor, a resonant inductor, a transformer, a rectifier, an output capacitor and a load resistor;
the resonant capacitor, the resonant inductor and the primary winding of the transformer are connected in series and further connected to the alternating current output end of the inverter;
an ac input terminal of the rectifier is connected to a secondary winding of the transformer;
the output capacitor is connected with the load resistor in parallel and then connected to a direct current output terminal of the rectifier.
The technical scheme of the system of the invention is a variable center average geometric control phase-shifting soft start method, which comprises the following specific steps:
step 1: the controller calculates the resonant frequency, builds a voltage gain model, sets the switching frequency of the inverter as the resonant frequency, sets the phase shift angle as zero, calculates a plurality of instant current instantaneous values of the output capacitor in the first half period of the starting process through a time domain analysis method, and further calculates the current average value of the output capacitor in the first half period of the starting process;
step 2: calculating equivalent inductance, equivalent angular frequency, reference voltage, reference impedance and reference current;
step 3: constructing a track plane coordinate system by taking the direct current voltage of the output capacitor as an X axis and the current average value of the output capacitor as a Y axis, selecting zero direct current voltage of the output capacitor and zero current average value of the output capacitor as an origin of the track plane coordinate system, setting a limiting value of the current average value of the output capacitor, calculating the initial number of circular arcs, the circle center of each circular arc and the central angle of each circular arc in the track plane coordinate system, and further calculating the running time of each circular arc;
step 4: adding a final arc track according to an arc distance judging model by combining a plurality of sections of arcs, calculating the total number of the arcs and the running time of each section of the final arc track, and updating the running time of the last section of the arcs in the plurality of sections of arcs;
step 5: sequentially assigning X-axis coordinates of the circle centers of all the sections of arcs to voltage gain, calculating phase shift angles of all the sections of arcs through a time domain analysis method, setting the phase shift angles of all the sections of arcs of the tail section of arc track to be 0, and generating a switch control signal of the inverter in the starting process by a controller in combination with the running time of all the sections of arcs and the running time of all the sections of arcs of the tail section of arc track, and performing inversion control of the inverter in combination with the switch control signal of the inverter in the starting process; after the running time of the last section of arc track is finished, the controller controls the inverter to output in a stable state;
preferably, the resonance frequency in step 1 is:
wherein f r Represent the resonant frequency, C r Representing the capacitance value of the resonant capacitor, L r An inductance value representing the resonance inductance;
the switching frequency in step 1 is:
f s ＝f r
wherein f s Representing the switching frequency;
the voltage gain model in step 1 is:
M＝nV o /V in
wherein M represents voltage gain, n represents transformation ratio of transformer, V o Representing the DC voltage of the output capacitor, V in Representing an input dc voltage;
the current average value of the output capacitor in the first half period of the starting process is calculated in the step 1, and the current average value is specifically as follows:
where h is the number of evenly distributed time points in the first half period, i Cj Representing the instantaneous value of the output capacitor current at the j-th instant in the first half cycle.
Preferably, the calculating the equivalent inductance in the step 2 is:
T s ＝1/f s
wherein L is AM Represents equivalent inductance, n represents transformation ratio of transformer, T s Represents the switching period of the inverter, C represents the capacitance value of the output capacitor, I CAM0 Representing the average value of the current of the output capacitor, V, during the first half period of the start-up procedure in Representing the input dc voltage, arccosis represents an arccosine calculation, f s Representing the switching frequency of the inverter;
and step 2, calculating equivalent angular frequency as follows:
wherein omega AM Represents the equivalent angular frequency, L AM Representing equivalent inductance, C representing the capacitance value of the output capacitor, and n representing the transformation ratio of the transformer;
and step 2, calculating a reference voltage, which is specifically as follows:
V base ＝V in /n；
wherein V is base Represents the reference voltage, n represents the transformation ratio of the transformer, V in Representing an input dc voltage;
the reference impedance is calculated in the step 2, and the reference impedance is specifically as follows:
wherein Z is base Represents the reference impedance, C represents the capacitance value of the output capacitor, L AM Representing the equivalent inductance;
and step 2, calculating a reference current, which is specifically as follows:
I base ＝V in /Z base
wherein I is base Representing a reference current;
preferably, the limiting value of the average value of the current of the output capacitor in the step 3 is defined as: i th ；
And 3, calculating the initial number of the circular arcs, wherein the initial number of the circular arcs is specifically as follows:
wherein k represents the adjacent circle center spacing coefficient, and m represents the initial number of circular arcs;
and 3, calculating the circle center of each section of arc, wherein the circle center is as follows:
((ki-k+1)I th ,0)
i∈[1,m]
wherein, ((ki-k+1) I th 0) represents a coordinate point of the circle center of the ith arc in the track plane coordinate system, (ki-k+1) I th The X-axis coordinate of the circle center of the ith arc in the track plane coordinate system is represented, 0 represents the Y-axis coordinate of the circle center of the ith arc in the track plane coordinate system, k represents the adjacent circle center interval coefficient, and m represents the initial number of the arcs;
and 3, calculating the central angle of each section of arc, wherein the central angle is specifically as follows:
wherein θ i The central angle of the ith arc is represented, k represents a central distance coefficient, arccosis (x) represents an inverse cosine calculation; and 3, calculating the running time of each section of arc, wherein the running time is specifically as follows:
t i ＝θ i /ω AM
wherein t is i Run time of ith arc, θ i Represents the central angle omega of the ith arc AM Is equivalent angular frequency;
preferably, the step 4 specifically includes the following steps:
if it isThe tail arc track consists of an (m+1) th arc and an (m+2) th arc;
wherein I is th K is the spacing coefficient of adjacent circle centers, and m is the initial number of circular arcs;
the coordinates of the circle center of the (m+1) th arc in the track plane coordinate system are (1, 0);
the coordinates of the circle center of the (m+2) th arc in the track plane coordinate system are (-1, 0);
the total number of the circular arcs is calculated as follows:
N＝m+2
wherein N represents the total number of circular arcs, and m is the initial number of circular arcs;
the operation time of the final arc is calculated as follows:
wherein ρ is m+1 Radius of the (m+1) th arc, t m+1 Run time, t, for the m+1th segment of arc m+2 For run time of the (m+2) th arc, arccosis (x) represents an arccosine calculation, arctg (x) representsArctangent calculation, I th For limiting the current average value of the output capacitor, k is the adjacent center distance coefficient, m is the initial number of circular arcs, omega AM Representing the equivalent angular frequency;
t m the running time of the mth section of arc is kept unchanged;
if it isThe tail arc track is formed by an (m+1) th arc;
the coordinates of the circle center of the (m+1) th arc in the track plane coordinate system are (-1, 0);
the total number of the circular arcs is calculated as follows:
N＝m+1
wherein N represents the total number of circular arcs, and m is the initial number of circular arcs;
the operation time of the final arc is calculated as follows:
wherein t is m Run time of mth arc, t m+1 For the running time of the (m+1) th arc, k is the adjacent center distance coefficient, arccos (x) represents the arccosine calculation, m is the initial number of arcs, I th For limiting the current average value of the output capacitance omega AM Representing the equivalent angular frequency;
preferably, the generating the switch control signal for starting the process inverter in step 5 is specifically as follows:
the upper switch of the left bridge arm of the inverter is defined as S 1 ；
The lower switch of the left bridge arm of the inverter is defined as S 2 ；
The switch on the right bridge arm of the inverter is defined as S 3 ；
The lower switch of the right bridge arm of the inverter is defined as S 4 ；
The controller starts from the running time of the 1 st arcUntil the running time of the N-1 th arc is over, S is in the running time of each arc 1 、S 2 、S 3 、S 4 The duty ratio of the switch control signals of the circuit is 50%;
the angle of the switch control signal of S4 lagging behind the switch control signal of S1 is equal to the phase shift angle of each arc, S 2 Switch control signal and S of (2) 1 Is inverted by the switch control signal S 3 Switch control signal and S of (2) 4 Is inverted with respect to the switch control signal of (a);
the controller controls S in the running time of the Nth arc 1 、S 2 、S 3 、S 4 All are turned off;
n represents the total number of the circular arcs obtained in the step 4;
and 5, the controller controls the steady-state output of the inverter, and the steady-state output is specifically as follows:
s of controller output 1 、S 2 、S 3 、S 4 The duty ratio of the switch control signals of (a) is 50%;
wherein S is 1 Switch control signal and S of (2) 4 Switch control signals of the same phase S 2 Switch control signal and S of (2) 1 Is inverted by the switch control signal S 3 Switch control signal and S of (2) 4 Is inverted with respect to the switching control signal of (a).
The beneficial effects of the invention are as follows:
a variable circle center average geometric control phase-shifting soft start method is characterized in that the circle center of a phase-shifting angle control track is changed to gradually move from a zero point to an end point (1, 0), the radius of each section of arc track does not exceed the current limit, and the situation that excessive current does not occur even if calculation time is deviated in operation is ensured, so that starting impact current is limited;
the track is basically positioned on an arc close to the current limit value in starting, the average value of the capacitor charging current is always larger, and the capacitor charging current does not repeatedly oscillate between zero and the current limit value, so that the charging speed is high; as long as the central angle of each middle section arc is smaller than 90 degrees, most of time |dV o /di CAM I is very large, and the output voltage is fast increased under a large capacitor charging currentLifting, and enabling the starting process to be more stable and rapid;
the inverter has fixed switching frequency, is convenient for digital control realization, and avoids over-design of a switching tube and a magnetic element caused by large-scale frequency conversion.
Obtaining the equivalent resonant angular frequency omega of the converter by using an equivalent second-order circuit AM Due to omega AM Much lower than the switching angular frequency 2 pi f of the resonant converter s The operation frequency of a core algorithm of the controller is reduced; as the central angles and the radiuses of all the circular arc tracks of the middle section are the same, only the tracks of the first section and the last section need special calculation, so that the calculated amount is greatly reduced, and the soft start can be quickly realized.
Drawings
Fig. 1: the LLC resonant converter topology structure schematic diagram of the embodiment of the invention.
Fig. 2: the embodiment of the invention discloses a variable center average geometric control phase-shifting soft start flow chart.
Fig. 3: the second-order equivalent circuit model of the embodiment of the invention.
Fig. 4: the 1 st arc calculation track diagram in the starting process of the embodiment of the invention.
Fig. 5: the ith arc of the starting process of the embodiment of the invention calculates a track diagram.
Fig. 6: the end arc calculation track diagram of the first condition in the starting process of the embodiment of the invention.
Fig. 7: the end arc calculation track diagram in the second condition of the starting process of the embodiment of the invention.
Fig. 8: the embodiment of the invention provides a phase-shifting dynamic circular track schematic diagram.
Fig. 9: the starting process simulation result of the embodiment of the invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In particular, the method according to the technical solution of the present invention may be implemented by those skilled in the art using computer software technology to implement an automatic operation flow, and a system apparatus for implementing the method, such as a computer readable storage medium storing a corresponding computer program according to the technical solution of the present invention, and a computer device including the operation of the corresponding computer program, should also fall within the protection scope of the present invention.
The technical scheme of the system of the embodiment of the invention is a variable center average geometric control phase-shifting soft start system, which comprises the following components:
the device comprises a controller, an inverter, a resonant capacitor, a resonant inductor, a transformer, a rectifier, an output capacitor and a load resistor;
the resonant capacitor, the resonant inductor and the primary winding of the transformer are connected in series and further connected to the alternating current output end of the inverter;
an ac input terminal of the rectifier is connected to a secondary winding of the transformer;
the output capacitor is connected with the load resistor in parallel and then connected to a direct current output terminal of the rectifier.
The model of the controller is NIPXIe-7846R;
the inverter is composed of 4 field effect transistors with the model number of 042N 10N;
the resonance capacitor is formed by connecting 2 capacitors with the model of PPS104J1000V in parallel;
the inductance of the resonant inductor is 12.9 mu H;
the parameters of the transformer are as follows: the transformation ratio is 1:2, and the excitation inductance is 56 mu H;
the rectifier is composed of 4 diodes with the model number of 1N 4007;
the output capacitor is formed by connecting 2 capacitors with the model SLPX121M400A3P3 in parallel;
the model of the load resistor is TE400B100RJ;
the following describes a variable center average geometry control phase shift soft start method provided by the embodiment of the invention with reference to fig. 1 to 9;
a schematic diagram of the LLC resonant converter topology of the embodiment of the invention is shown in FIG. 1, wherein S 1 S is the upper switch of the left bridge arm of the inverter 2 Is a left bridge arm lower switch of the inverter, S 3 S is the upper switch of the right bridge arm of the inverter 4 L is the lower switch of the right bridge arm of the inverter r Is resonant inductance, C r Is a resonant capacitor L m Is the excitation inductance of the transformer, n is the transformation ratio of the transformer, and VD 1 Is the upper switch of the left bridge arm of the rectifier, VD 2 Is the lower switch of the left bridge arm of the rectifier, VD 3 Is the upper switch of the right bridge arm of the rectifier, VD 4 The lower switch of the right bridge arm of the rectifier is adopted, C is an output capacitor, and R is a direct current load;
the variable circle center average geometric control phase-shifting soft start flow chart of the embodiment of the invention is shown in fig. 2, and comprises the following steps:
step 1: the controller calculates the resonant frequency, builds a voltage gain model, sets the switching frequency of the inverter as the resonant frequency, sets the phase shift angle as zero, calculates a plurality of instant current instantaneous values of the output capacitor in the first half period of the starting process through a time domain analysis method, and further calculates the current average value of the output capacitor in the first half period of the starting process;
the resonant frequency in step 1 is:
wherein f r ＝100kHz，C r ＝196nF，L r ＝12.9μH；
The switching frequency in step 1 is:
f s ＝f r
wherein f s ＝100kHz；
The voltage gain model in step 1 is:
M＝nV o /V in
wherein M represents voltage gain, n represents transformation ratio of transformer, V o Representing the DC voltage of the output capacitor, V in Representing an input dc voltage;
the current average value of the output capacitor in the first half period of the starting process is calculated in the step 1, and the current average value is specifically as follows:
where h is the number of evenly distributed time points in the first half period, i Cj Representing the instantaneous value of the output capacitor current at the j-th instant in the first half cycle.
Step 2: calculating equivalent inductance, equivalent angular frequency, reference voltage, reference impedance and reference current;
and step 2, calculating equivalent inductance as follows:
T s ＝1/f s
wherein L is AM ＝31.89μH，n＝0.5，f s ＝f r ＝100kHz，T s ＝10μs，C＝200μF，I CAM0 ＝0.9016，V in =23v, arccos (x) represents an arccosine calculation;
and step 2, calculating equivalent angular frequency as follows:
wherein omega AM ＝6260.8rad/s，L AM ＝31.89μH，n＝0.5，C＝200μF；
And step 2, calculating a reference voltage, which is specifically as follows:
V base ＝V in /n；
wherein V is base ＝46V，V in ＝23V，n＝0.5；
The reference impedance is calculated in the step 2, and the reference impedance is specifically as follows:
wherein Z is base ＝0.799Ω，C＝200μF，L AM ＝31.89μH，n＝0.5；
And step 2, calculating a reference current, which is specifically as follows:
I base ＝V base /Z base
wherein I is base ＝57.60A，V base ＝46V，Z base ＝0.799Ω；
Primary equivalent inductance L AM And the capacitor C form a second-order equivalent circuit model shown in figure 3, wherein n is the transformation ratio of the transformer, MV in Representing the input voltage of the equivalent model, the current source I o Stage I of start-up for load current o Smaller and can be considered as constant.
Step 3: constructing a track plane coordinate system by taking the direct current voltage of the output capacitor as an X axis and the current average value of the output capacitor as a Y axis, selecting the direct current voltage of the output capacitor as 0 and the current average value of the output capacitor as an origin of the track plane coordinate system, setting a limiting value of the current average value of the output capacitor, calculating the initial number of circular arcs, the circle center of each circular arc and the central angle of each circular arc in the track plane coordinate system, and further calculating the running time corresponding to each circular arc;
and 3, defining a limiting value of the current average value of the output capacitor as: i th =0.0408 (per unit value);
and 3, calculating the initial number of the circular arcs, wherein the initial number of the circular arcs is specifically as follows:
wherein k=1, m=25;
and 3, calculating the circle center of each section of arc, wherein the circle center is as follows:
((ki-k+1)I th ,0)
i∈[1,25]
wherein, (0.0408 i, 0) represents a coordinate point of the circle center of the ith arc in the track plane coordinate system;
and 3, calculating the central angle of each section of arc, wherein the central angle is specifically as follows:
wherein,arccosis (x) denotes an arccosine calculation, k=1;
and 3, calculating the running time corresponding to each section of arc, wherein the running time is specifically as follows:
t i ＝θ i /ω AM
wherein,ω AM ＝6260.8rad/s；
the 1 st arc track in the step 3 is shown in FIG. 4, wherein i CAM To output the current average value of the capacitor, I th For limiting the average value of the current of the output capacitor, V o To output voltage, kM 1 For the distance of each arc, theta 1 Is the central angle of the first section of arc;
the ith arc track in step 3 is shown in FIG. 5, wherein i is as follows CAM To output the current average value of the capacitor, I th For limiting the average value of the current of the output capacitor, V o For output voltage, ((ki-k+1) I) th 0) is the center of each arc, θ i Is the central angle of each arc.
Step 4: adding the last-segment arc track according to the arc distance judging model by combining the multiple segments of arcs in the step 3, calculating the total number of the arcs and the running time of each segment of the last-segment arc track, and updating the running time of the last segment of the multiple segments of arcs;
the step 4 specifically comprises the following steps:
due toThe tail arc track is formed by an (m+1) th arc;
wherein I is th ＝0.0408，k＝1，m＝25；
The coordinates of the circle center of the (m+1) th arc in the track plane coordinate system are (-1, 0);
the total number of the circular arcs is calculated as follows:
N＝m+1＝26
the operation time of the final arc is calculated as follows:
wherein t is m ＝3.929×10 -7 s，t m+1 ＝2.826×10 -6 s, arccosis (x) represents an arccosine calculation;
the final arc track in step 4 is shown in FIG. 7, wherein i CAM To output the current average value of the capacitor, I th For limiting the average value of the current of the output capacitor, V o To output voltage M m Is the center of the m-th arc; and if the step 4 meets the criterion, the tail end arc track is shown in fig. 6.
Step 5: sequentially assigning the X-axis coordinates of the circle center of each section of arc in the step 3 to voltage gain, calculating to obtain the phase shift angle of each section of arc through a time domain analysis method, setting the phase shift angle of each section of arc of the final section of arc track in the step 4 to 0, and generating a switch control signal of the inverter in the starting process by the controller in combination with the running time of each section of arc in the step 3 and the running time of each section of arc of the final section of arc track in the step 4, and performing inversion control of the inverter in combination with the switch control signal of the inverter in the starting process; after the running time of the last section of arc track is finished, the controller controls the inverter to output in a stable state;
FIG. 8 shows a practical embodiment of the inventionPhase-shifting dynamic circular trace schematic of the embodiment. Wherein i is CAM To output the current average value of the capacitor, I th For limiting the average value of the current of the output capacitor, V o To output voltage M 1 Is the center of the 1 st arc, θ 1 Is the central angle theta of the first section of arc i The central angle of each section of arc;
and 5, generating a switch control signal for starting the process inverter, wherein the switch control signal is specifically as follows:
the upper switch of the left bridge arm of the inverter is defined as S 1 ；
The lower switch of the left bridge arm of the inverter is defined as S 2 ；
The switch on the right bridge arm of the inverter is defined as S 3 ；
The lower switch of the right bridge arm of the inverter is defined as S 4 ；
The controller starts from the running time of the 1 st section of arc to the running time of the N-1 st section of arc to finish, S is in the running time of each section of arc 1 、S 2 、S 3 、S 4 The duty ratio of the switch control signals of the circuit is 50%;
S 4 the switch control signal of (2) lags behind S 1 The angle of the switch control signal of (2) is equal to the phase shift angle of each arc, S 2 、S 3 Switch control signals of (2) are respectively with S 1 、S 4 Is inverted with respect to the switch control signal of (a);
the controller controls S in the running time of the Nth arc 1 、S 2 、S 3 、S 4 All are turned off;
n represents the total number of the circular arcs obtained in the step 4;
and 5, the controller controls the steady-state output of the inverter, and the steady-state output is specifically as follows:
s of controller output 1 、S 2 、S 3 、S 4 The duty ratio of the switch control signals of (a) is 50%;
wherein S is 1 Switch control signal and S of (2) 4 Switch control signals of the same phase S 2 Switch control signals of (2) are respectively with S 1 Is inverted by the switch control signal S 3 Switch control signals of (2) are respectively with S 4 Is inverted with respect to the switching control signal of (a).
FIG. 9 is a simulation waveform of the start-up process according to an embodiment of the present invention, in which the output voltage V o Rising process and output capacitance charging current average value i CAM Input current i of resonant cavity Lr The change trend of the soft start method is basically consistent with the arc track, and the soft start method can verify that the resonant converter can be started quickly and stably.
It should be understood that parts of the specification not specifically set forth herein are all prior art.
Although terms such as controller, inverter, resonant capacitor, resonant inductor, transformer, rectifier, output capacitor, load resistor, etc. are used more herein, the possibility of using other terms is not precluded. These terms are only used to facilitate a more complete description of the nature of the invention and should be construed as requiring no additional limitations whatsoever.
It should be understood that the foregoing description of the preferred embodiments is not intended to limit the scope of the invention, but rather to limit the scope of the claims, and that those skilled in the art can make substitutions or modifications without departing from the scope of the invention as set forth in the appended claims.
Claims (8)
1. The utility model provides a become centre of a circle average geometry control and shift phase soft start system which characterized in that includes:
the device comprises a controller, an inverter, a resonant capacitor, a resonant inductor, a transformer, a rectifier, an output capacitor and a load resistor;
the resonant capacitor, the resonant inductor and the primary winding of the transformer are connected in series and further connected to the alternating current output end of the inverter;
an ac input terminal of the rectifier is connected to a secondary winding of the transformer;
the output capacitor is connected with the load resistor in parallel and then connected to a direct current output terminal of the rectifier;
the controller calculates the resonant frequency, constructs a voltage gain model, and calculates equivalent inductance, equivalent angular frequency, reference voltage, reference impedance and reference current; constructing a track plane coordinate system, calculating the initial number of the circular arcs, the circle center of each section of circular arc and the central angle of each section of circular arc in the track plane coordinate system, and further calculating the running time of each section of circular arc; adding a final arc track according to an arc distance judging model by combining a plurality of sections of arcs, calculating the total number of the arcs and the running time of each section of the final arc track, and updating the running time of the last section of the arcs in the plurality of sections of arcs; the controller generates a switch control signal of the inverter in the starting process according to the running time of each section of arc and the running time of each section of arc of the tail section of arc track, and performs inverter control of the inverter according to the switch control signal of the inverter in the starting process; and after the running time of the last section of arc track is finished, the controller controls the inverter to output in a stable state.
2. A method for performing variable center average geometry controlled phase shift soft start by using the variable center average geometry controlled phase shift soft start system of claim 1, comprising the steps of:
step 1: the controller calculates the resonant frequency, builds a voltage gain model, sets the switching frequency of the inverter as the resonant frequency, sets the phase shift angle as zero, calculates a plurality of instant current instantaneous values of the output capacitor in the first half period of the starting process through a time domain analysis method, and further calculates the current average value of the output capacitor in the first half period of the starting process;
step 2: calculating equivalent inductance, equivalent angular frequency, reference voltage, reference impedance and reference current;
step 3: constructing a track plane coordinate system by taking the direct current voltage of the output capacitor as an X axis and the current average value of the output capacitor as a Y axis, selecting zero direct current voltage of the output capacitor and zero current average value of the output capacitor as an origin of the track plane coordinate system, setting a limiting value of the current average value of the output capacitor, calculating the initial number of circular arcs, the circle center of each circular arc and the central angle of each circular arc in the track plane coordinate system, and further calculating the running time of each circular arc;
step 4: adding a final arc track according to an arc distance judging model by combining a plurality of sections of arcs, calculating the total number of the arcs and the running time of each section of the final arc track, and updating the running time of the last section of the arcs in the plurality of sections of arcs;
step 5: sequentially assigning X-axis coordinates of the circle centers of all the sections of arcs to voltage gain, calculating phase shift angles of all the sections of arcs through a time domain analysis method, setting the phase shift angles of all the sections of arcs of the tail section of arc track to be 0, and generating a switch control signal of the inverter in the starting process by a controller in combination with the running time of all the sections of arcs and the running time of all the sections of arcs of the tail section of arc track, and performing inversion control of the inverter in combination with the switch control signal of the inverter in the starting process; and after the running time of the last section of arc track is finished, the controller controls the inverter to output in a stable state.
3. The variable center average geometry control phase shift soft start method according to claim 2, wherein the method comprises the following steps:
the resonant frequency in step 1 is:
wherein f r Represent the resonant frequency, C r Representing the capacitance value of the resonant capacitor, L r An inductance value representing the resonance inductance;
the switching frequency in step 1 is:
f s ＝f r
wherein f s Representing the switching frequency;
the voltage gain model in step 1 is:
M＝nV o /V in
wherein M represents voltage gain, n represents transformation ratio of transformer, V o Representing the DC voltage of the output capacitor, V in Representing an input dc voltage;
the current average value of the output capacitor in the first half period of the starting process is calculated in the step 1, and the current average value is specifically as follows:
where h is the number of evenly distributed time points in the first half period, i Cj Representing the instantaneous value of the output capacitor current at the j-th instant in the first half cycle.
4. The variable center average geometry control phase shift soft start method according to claim 3, wherein the method comprises the following steps:
and step 2, calculating equivalent inductance as follows:
T s ＝1/f s
wherein L is AM Represents equivalent inductance, n represents transformation ratio of transformer, T s Represents the switching period of the inverter, C represents the capacitance value of the output capacitor, I CAM0 Representing the average value of the current of the output capacitor, V, during the first half period of the start-up procedure in Representing the input dc voltage, arccosis represents an arccosine calculation, f s Representing the switching frequency of the inverter;
and step 2, calculating equivalent angular frequency as follows:
wherein omega AM Represents the equivalent angular frequency, L AM Representing equivalent inductance, C representing the capacitance of the output capacitorN represents the transformation ratio of the transformer;
and step 2, calculating a reference voltage, which is specifically as follows:
V base ＝V in /n；
wherein V is base Represents the reference voltage, n represents the transformation ratio of the transformer, V in Representing an input dc voltage;
the reference impedance is calculated in the step 2, and the reference impedance is specifically as follows:
wherein Z is base Represents the reference impedance, C represents the capacitance value of the output capacitor, L AM Representing the equivalent inductance;
and step 2, calculating a reference current, which is specifically as follows:
I base ＝V in /Z base
wherein I is base Representing the reference current.
5. The variable center average geometry control phase shift soft start method according to claim 4, wherein the method comprises the following steps:
and 3, defining a limiting value of the current average value of the output capacitor as: i th ；
And 3, calculating the initial number of the circular arcs, wherein the initial number of the circular arcs is specifically as follows:
wherein k represents the adjacent circle center spacing coefficient, and m represents the initial number of circular arcs;
and 3, calculating the circle center of each section of arc, wherein the circle center is as follows:
((ki-k+1)I th ,0)
i∈[1,m]
wherein, ((ki-k+1) I th 0) the circle center of the ith arc is in the track plane coordinate systemCoordinate point, (ki-k+1) I th The X-axis coordinate of the circle center of the ith arc in the track plane coordinate system is represented, 0 represents the Y-axis coordinate of the circle center of the ith arc in the track plane coordinate system, k represents the adjacent circle center interval coefficient, and m represents the initial number of the arcs;
and 3, calculating the central angle of each section of arc, wherein the central angle is specifically as follows:
wherein θ i The central angle of the ith arc is represented, k represents a central distance coefficient, arccosis (x) represents an inverse cosine calculation;
and 3, calculating the running time of each section of arc, wherein the running time is specifically as follows:
t i ＝θ i /ω AM
wherein t is i Run time of ith arc, θ i Represents the central angle omega of the ith arc AM Is the equivalent angular frequency.
6. The variable center average geometry control phase shift soft start method according to claim 5, wherein the method comprises the following steps:
the step 4 specifically comprises the following steps:
if it isThe tail arc track consists of an (m+1) th arc and an (m+2) th arc;
wherein I is th K is the spacing coefficient of adjacent circle centers, and m is the initial number of circular arcs;
the coordinates of the circle center of the (m+1) th arc in the track plane coordinate system are (1, 0);
the coordinates of the circle center of the (m+2) th arc in the track plane coordinate system are (-1, 0);
the total number of the circular arcs is calculated as follows:
N＝m+2
wherein N represents the total number of circular arcs, and m is the initial number of circular arcs;
the running time of each section of arc of the final section of arc track is calculated, and the running time is specifically as follows:
wherein ρ is m+1 Radius of the (m+1) th arc, t m+1 Run time, t, for the m+1th segment of arc m+2 For the run time of the m+2-th arc, arccosis (x) represents arccosine calculation, arctg (x) represents arctangent calculation, I th For limiting the current average value of the output capacitor, k is the adjacent center distance coefficient, m is the initial number of circular arcs, omega AM Representing the equivalent angular frequency;
t m the running time of the mth section of arc is kept unchanged;
if it isThe tail arc track is formed by an (m+1) th arc;
the coordinates of the circle center of the (m+1) th arc in the track plane coordinate system are (-1, 0);
the total number of the circular arcs is calculated as follows:
N＝m+1
wherein N represents the total number of circular arcs, and m is the initial number of circular arcs;
the operation time of the final arc is calculated as follows:
wherein t is m Run time of mth arc, t m+1 For the running time of the (m+1) th arc, k is the adjacent center distance coefficient, arccos (x) represents the arccosine calculation, m is the initial number of arcs, I th For limiting the current average value of the output capacitance omega AM Representing the equivalent angular frequency.
7. The variable center average geometry control phase shift soft start method according to claim 6, wherein the method comprises the following steps:
and 5, generating a switch control signal for starting the process inverter, wherein the switch control signal is specifically as follows:
the upper switch of the left bridge arm of the inverter is defined as S 1 ；
The lower switch of the left bridge arm of the inverter is defined as S 2 ；
The switch on the right bridge arm of the inverter is defined as S 3 ；
The lower switch of the right bridge arm of the inverter is defined as S 4 ；
The controller starts from the running time of the 1 st section of arc to the running time of the N-1 st section of arc to finish, S is in the running time of each section of arc 1 、S 2 、S 3 、S 4 The duty ratio of the switch control signals of the circuit is 50%;
the angle of the switch control signal of S4 lagging behind the switch control signal of S1 is equal to the phase shift angle of each arc, S 2 Switch control signal and S of (2) 1 Is inverted by the switch control signal S 3 Switch control signal and S of (2) 4 Is inverted with respect to the switch control signal of (a);
the controller controls S in the running time of the Nth arc 1 、S 2 、S 3 、S 4 All are turned off;
n represents the total number of arcs.
8. The variable center average geometry control phase shift soft start method according to claim 7, wherein the method comprises the following steps:
and 5, the controller controls the steady-state output of the inverter, and the steady-state output is specifically as follows:
s of controller output 1 、S 2 、S 3 、S 4 The duty ratio of the switch control signals of (a) is 50%;
wherein S is 1 Switch control signal and S of (2) 4 Switch control signals of the same phase S 2 Switch control signal and S of (2) 1 Is inverted by the switch control signal S 3 Switch control signal and S of (2) 4 Is inverted with respect to the switching control signal of (a).
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