CN115940652B - Variable circle center average geometric control phase-shifting soft start system and method - Google Patents

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

A variable circle center average geometric control phase shift soft start system and method

Technical field

The invention belongs to the technical field of control of resonant converters in power electronic devices, and in particular relates to a variable center average geometric control phase-shifting soft start system and method.

Background technique

With the continuous development of new energy technology, the LLC resonant converter has become an efficient DC-DC converter due to its easy-to-implement soft switching characteristics and high power density. It is widely used in power electronic energy storage devices and electric vehicle charging. It is widely used in switching power supply and other fields. However, the input impedance of the resonant cavity of the resonant converter is very small, and the voltage across the filter capacitor is very low during startup, which is equivalent to a short circuit, resulting in inrush current and output voltage overshoot during power-on and startup, especially in high-power converters. The inrush current problem is more prominent and may cause serious problems such as burned circuits.

In order to reduce the starting inrush current and make the output voltage reach the rated value smoothly as soon as possible, three types of soft start control methods have emerged: frequency reduction soft start, phase shift soft start and optimal trajectory control soft start.

Among them, frequency reduction soft start and phase shift soft start respectively take advantage of the characteristics that the output voltage of the LLC resonant converter decreases as the switching frequency of the primary inverter increases and the phase shift angle between the left and right bridge arms increases. It starts working at several times the rated frequency or a larger phase shift angle (fixed switching frequency), and then gradually reduces the frequency or phase shift angle until it reaches the rated steady state. However, the high switching frequency of frequency reduction soft start is not convenient for digital controller implementation, leading to over-design of magnetic components and switching tubes, increasing costs; and because the voltage decreases slowly with increasing frequency, increasing the frequency is detrimental to reducing the voltage. The adjustment capability is limited, so there is still a large starting current. Phase-shifted soft start repeatedly tests the phase-shift angle that meets the current limit based on the time-domain equivalent model of the converter switching cycle by switching cycle, which requires a large amount of calculation. The optimal trajectory soft start is also based on the time domain equivalent model of the converter, calculating the moment when the switching frequency is switched or the turn-on and off time of each switch. Therefore, the switching frequency is not fixed, and the delay of the control loop will cause the trajectory to exceed the control, which requires High-speed sampling and control are relatively expensive.

In order to achieve low-cost soft start at a fixed switching frequency, the existing technology proposes an average geometry control method for the half-bridge LLC converter. This method equates the resonant network on the primary side of the converter to an average inductor L _AM , which forms a second-order equivalent circuit with the output capacitor C. During the startup process, the plane trajectory of the average current i _CAM of C and the output voltage _Vo is controlled. Limit starting inrush current. After all parameter variables are normalized, when the half-bridge inverter outputs at the resonant frequency and zero phase shift angle, the trajectory of V _o and i _CAM is centered on (1,0), with the initial state coordinates and (1 ,0) is an arc with a radius, and ends when i _CAM reaches the current limit; when the half-bridge inverter stops output, the trajectories of V _o and i _CAM are with (-1,0) as the center and the initial The distance between the state coordinate and (-1,0) is an arc with a radius, and ends when i _CAM drops to 0. The half-bridge inverter output and stop arcs alternately switch. By calculating and controlling the normal output and stop time step by step, i _CAM continues to rise and fall but the peak value does not exceed the limit, while V _o continues to rise. However, this method has the following shortcomings:

During the startup process, most of the operating trajectories are in the small range of dV _o /di _CAM . The average value of the output capacitor charging current oscillates repeatedly between zero and the current limit. V _o rises slowly, and the startup process efficiency is low and fluctuates. larger.

During the start-up process, the running time of each arc is a variable amount, which needs to be calculated one by one, which requires a large amount of calculation. The calculation error between the inverter output and stop time can easily cause the current to exceed the limit, which requires greater accuracy of circuit parameters and calculation accuracy. high.

The present invention proposes a faster and less computationally intensive average geometry control phase-shifting soft start method suitable for full-bridge LLC resonant converters.

Contents of the invention

The purpose of the present invention is to propose an average geometric soft-start method with fixed switching frequency, low cost and small calculation amount for the full-bridge LLC resonant converter. This method adopts fixed-frequency phase-shift control for the primary-side inverter, establishes the 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 capacitor current. The trajectory plane coordinate system is constructed using the voltage of the output capacitor and its average current value as the X-axis and Y-axis. The starting trajectory consists of multiple arcs close to the current limit value. The center of each arc corresponds to a phase shift angle. During startup, the center of the arc gradually approaches from near (0,0) to the steady state (1,0). The radius does not exceed the current limit, and the phase shift angle decreases accordingly. It is not until the end of startup that a section with the length of (-1, 0) completes the transition to the steady state for the arc trajectory with the center of the circle and a radius of 2. Most of the running trajectories of this method are in a large range of |dV _o /di _CAM |, so the voltage rises faster; at the same time, except for the first and last sections of most arcs, the running time is equal, and the amount of calculation is greatly reduced. No need for high-speed sampling, easy to implement.

In addition, it is a known technology to use the time domain analysis method to analyze the switching state of the LLC resonant converter, write the circuit state equation, derive the calculation model, calculate the voltage and current of the circuit based on the phase shift angle, and calculate the phase shift angle based on the voltage gain.

The technical solution of the system of the present invention is a variable center average geometric control phase-shifting soft start system, which includes:

Controller, inverter, resonant capacitor, resonant inductor, transformer, rectifier, output capacitor, load resistor;

The resonant capacitor, resonant inductor and primary winding of the transformer are connected in series and further connected to the AC output end of the inverter;

The AC input terminal of the rectifier is connected to the secondary winding of the transformer;

The output capacitor is connected in parallel with the load resistor and then connected to the DC output terminal of the rectifier.

The technical solution of the system of the present invention is a phase-shifting soft start method with variable center average geometry control. The specific steps are as follows:

Step 1: The controller calculates the resonant frequency and constructs a voltage gain model, sets the switching frequency of the inverter to the resonant frequency, sets the phase shift angle to zero, and calculates the first half of the startup process through time domain analysis. The instantaneous current values of the output capacitor at multiple times during the cycle are further calculated to calculate the average current value of the output capacitor during the first half cycle of the startup process;

Step 2: Calculate equivalent inductance, equivalent angular frequency, reference voltage, reference impedance, and reference current;

Step 3: Use the DC voltage of the output capacitor as the X-axis and the average current of the output capacitor as the Y-axis to construct a trajectory plane coordinate system. Select the DC voltage of the output capacitor to be zero and the average current value of the output capacitor to be zero as the trajectory plane coordinate system. The origin of , set the limit value of the average current of the output capacitor, calculate the initial number of arcs, the center of each arc, and the central angle of each arc in the trajectory plane coordinate system, and further calculate the operation hours;

Step 4: Combine multiple arcs and add the final arc trajectory based on the arc distance determination model, and calculate the total number of arcs, the running time of each arc in the final arc trajectory, and update the last segment of the multiple arcs. arc running time;

Step 5: Assign the X-axis coordinate of the center of each arc to the voltage gain in turn, calculate the phase shift angle of each arc through time domain analysis, and then shift the phase of each arc in the final arc trajectory. The angles are all set to 0. The controller combines the running time of each arc segment and the running time of each arc segment of the final arc trajectory to generate the switching control signal of the inverter during the starting process, combined with the switching control of the inverter during the starting process. The signal performs inversion control of the inverter; after the last arc trajectory ends with a segment of arc running time, the controller controls the steady-state output of the inverter;

Preferably, the resonant frequency in step 1 is:

Among them, f _r represents the resonant frequency, C _r represents the capacitance of the resonant capacitor, and L _r represents the inductance of the resonant inductor;

The switching frequency mentioned in step 1 is:

f _s = f _r

Among them, f _s represents the switching frequency;

The voltage gain model described in step 1 is:

M＝nV _o /V _in

Among them, M represents the voltage gain, n represents the transformation ratio of the transformer, V _o represents the DC voltage of the output capacitor, and V _in represents the input DC voltage;

Calculate the average current of the output capacitor during the first half cycle of the startup process as described in step 1, as follows:

Among them, h is the number of uniformly distributed time points in the first half cycle, and i _Cj represents the instantaneous value of the output capacitor current at the jth time point in the first half cycle.

Preferably, the equivalent inductance calculated in step 2 is:

T _s =1/f _s

Among them, L _AM represents the equivalent inductance, n represents the transformation ratio of the transformer, T _s represents the switching period of the inverter, C represents the capacitance of the output capacitor, and I _CAM0 represents the average current of the output capacitor in the first half cycle of the startup process. value, V _in represents the input DC voltage, arccos(*) represents the inverse cosine calculation, and f _s represents the switching frequency of the inverter;

The equivalent angular frequency calculated in step 2 is:

Among them, ω _AM represents the equivalent angular frequency, L _AM represents the equivalent inductance, C represents the capacitance of the output capacitor, and n represents the transformation ratio of the transformer;

Calculate the reference voltage as described in step 2, as follows:

V _base =V _in /n;

Among them, V _base represents the reference voltage, n represents the transformation ratio of the transformer, and V _in represents the input DC voltage;

Calculate the reference impedance as described in step 2, as follows:

Among them, Z _base represents the base impedance, C represents the capacitance of the output capacitor, and L _AM represents the equivalent inductance;

Calculate the reference current as described in step 2, as follows:

I _base =V _in /Z _base

Among them, I _base represents the base current;

Preferably, the limit value of the average current of the output capacitor in step 3 is defined as: I _th ;

Calculate the initial number of arcs as described in step 3, as follows:

Among them, k represents the distance coefficient between adjacent circle centers, and m represents the initial number of arcs;

Calculate the center point of each arc as described in step 3, as follows:

((ki-k+1)I _th ,0)

i∈[1,m]

Among them, ((ki-k+1)I _th ,0) represents the center point of the i-th arc segment at the coordinate point of the trajectory plane coordinate system, (ki-k+1)I _th represents the center point of the i-th arc segment at The X-axis coordinate of the trajectory plane coordinate system, 0 represents the Y-axis coordinate of the center of the i-th arc in the trajectory plane coordinate system, k represents the spacing coefficient between adjacent circle centers, and m represents the initial number of arcs;

Calculate the central angle of each arc as described in step 3, as follows:

Among them, θ _i represents the central angle of the i-th arc, k represents the center distance coefficient, arccos(*) represents the inverse cosine calculation; the running time of each arc is calculated as described in step 3, specifically:

t _i =θ _i /ω _AM

Among them, t _i is the running time of the i-th arc, θ _i represents the central angle of the i-th arc, and ω _AM is the equivalent angular frequency;

Preferably, the step 4 is as follows:

like The final arc trajectory consists of the m+1 arc segment and the m+2 arc segment;

Among them, I _th is the limit value of the average current of the output capacitor, k is the spacing coefficient between adjacent circle centers, and m is the initial number of arcs;

The coordinates of the center of the m+1 arc in the trajectory plane coordinate system are (1,0);

The coordinates of the center of the m+2 arc in the trajectory plane coordinate system are (-1,0);

The total number of arcs is calculated as follows:

N＝m+2

Among them, N represents the total number of arcs, and m is the initial number of arcs;

The calculation of the running time of the last arc is as follows:

Among them, ρ _m+1 is the radius of the m+1 arc, t _m+1 is the running time of the m+1 arc, t _m+2 is the running time of the m+2 arc, arccos (*) represents arc cosine calculation, arctg (*) represents arc tangent calculation, I _th is the limit value of the average current of the output capacitor, k is the spacing coefficient between adjacent circle centers, m is the initial number of arcs, ω _AM represents etc. Effective angular frequency;

t _m is the running time of the m-th arc and remains unchanged;

like The final arc trajectory is composed of the m+1th arc segment;

The coordinates of the center of the m+1 arc in the trajectory plane coordinate system are (-1,0);

The total number of arcs is calculated as follows:

N＝m+1

Among them, N represents the total number of arcs, and m is the initial number of arcs;

The calculation of the final arc running time is as follows:

Among them, t _m is the running time of the m-th arc segment, t _m+1 is the running time of the m+1-th arc segment, k is the spacing coefficient between adjacent circle centers, arccos(*) represents the inverse cosine calculation, and m is the circle The initial number of arcs, I _th is the limit value of the average current of the output capacitor, ω _AM represents the equivalent angular frequency;

Preferably, the switching control signal of the inverter during the startup process is generated as described in step 5, specifically as follows:

The switch on the left arm of the inverter is defined as S ₁ ;

The switch under the left arm of the inverter is defined as S ₂ ;

The switch on the right arm of the inverter is defined as S ₃ ;

The switch under the right bridge arm of the inverter is defined as S ₄ ;

The controller starts from the running time of the first arc segment to the end of the running time of the N-1 arc segment. During the running time of each arc segment, the switch control signals of S ₁ , S ₂ , S ₃ and S ₄ account for The empty ratio is 50%;

The angle by which the switch control signal of S4 lags behind the switch control signal of S1 is equal to the phase shift angle of each arc. The switch control signal of _S2 is inverse phase with the switch control signal of _S1 . The switch control signal of _S3 is in phase with the switch control signal of _S4 . The switch control signal is inverted;

The controller controls all S ₁ , S ₂ , S ₃ and S ₄ to turn off during the running time of the Nth arc;

N represents the total number of arcs obtained in step 4;

The controller described in step 5 controls the steady-state output of the inverter, as follows:

The duty cycle of the switch control signals of S ₁ , S ₂ , S ₃ and S ₄ output by the controller is all 50%;

Among them, the switch control signal of _S1 is in the same phase as the switch control signal of _S4 , the switch control signal of _S2 is inverted with the switch control signal of _S1 , and the switch control signal of _S3 is inverted with the switch control signal of _S4 .

The beneficial effects of the present invention are:

A method of phase-shift soft start with variable center average geometric control. By changing the phase-shift angle, the center of the trajectory is gradually moved from the zero point to the end point (1,0). The radius of each arc trajectory does not exceed the current limit, ensuring that even during operation Even if the calculation time deviates, excessive current will not occur, thus limiting the starting inrush current;

During startup, the trajectory is basically on an arc close to the current limit. The average value of the capacitor charging current is always larger, instead of repeatedly oscillating between zero and the current limit, so the charging speed is fast; as long as the central angle of each middle arc is If it is less than 90°, |dV _o /di _CAM | is very large most of the time, the output voltage rises rapidly under the larger capacitor charging current, and the startup process is smoother and faster;

The switching frequency of the inverter is fixed, which facilitates digital control implementation and avoids over-design of switching tubes and magnetic components due to large-scale frequency conversion.

The equivalent resonant angular frequency ω _AM of the converter is obtained by using the equivalent second-order circuit. Since ω _AM is far lower than the switching angular frequency 2πf _s of the resonant converter, the operating frequency of the core algorithm of the controller is reduced; since all the intermediate arcs The central angle and radius of the trajectory are the same, and only the first and last sections of the trajectory require special calculations, which greatly reduces the amount of calculation and can quickly achieve soft start.

Description of drawings

Figure 1: Schematic diagram of the LLC resonant converter topology according to the embodiment of the present invention.

Figure 2: Flow chart of variable circle center average geometry control phase-shifting soft start according to the embodiment of the present invention.

Figure 3: Second-order equivalent circuit model of the embodiment of the present invention.

Figure 4: The arc calculation trajectory diagram of the first section of the startup process according to the embodiment of the present invention.

Figure 5: Calculation trajectory diagram of the i-th arc during the startup process of the embodiment of the present invention.

Figure 6: The final arc calculation trajectory diagram in the first case of the startup process of the embodiment of the present invention.

Figure 7: The final arc calculation trajectory diagram in the second case of the startup process according to the embodiment of the present invention.

Figure 8: Schematic diagram of phase-shifting dynamic circular trajectory according to the embodiment of the present invention.

Figure 9: Simulation results of the startup process according to the embodiment of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

During specific implementation, the method proposed by the technical solution of the present invention can be realized by those skilled in the art using computer software technology to realize the automatic operation process. The system device for implementing the method is, for example, a computer-readable storage medium that stores the computer program corresponding to the technical solution of the present invention and a computer that runs the corresponding Program computer equipment should also be within the protection scope of the present invention.

The technical solution of the system of the embodiment of the present invention is a variable center average geometric control phase-shifting soft start system, which includes:

Controller, inverter, resonant capacitor, resonant inductor, transformer, rectifier, output capacitor, load resistor;

The resonant capacitor, resonant inductor and primary winding of the transformer are connected in series and further connected to the AC output end of the inverter;

The AC input terminal of the rectifier is connected to the secondary winding of the transformer;

The output capacitor is connected in parallel with the load resistor and then connected to the DC output terminal of the rectifier.

The model of the controller is NIPXIe-7846R;

The inverter is composed of 4 field effect transistors of model 042N10N;

The resonant capacitor is composed of two capacitors of model PPS104J1000V connected in parallel;

The inductance of the resonant inductor is 12.9μH;

The parameters of the transformer are: transformation ratio 1:2, excitation inductance 56μH;

The rectifier is composed of 4 diodes of model 1N4007;

The output capacitor is composed of two capacitors of model SLPX121M400A3P3 connected in parallel;

The model of the load resistor is TE400B100RJ;

The following describes a variable circle center average geometric control phase-shifting soft start method provided by an embodiment of the present invention with reference to Figures 1-9;

The schematic diagram of the LLC resonant converter topology according to the embodiment of the present invention is shown in Figure 1, where S ₁ is the upper switch on the left arm of the inverter, S ₂ is the lower switch on the left arm of the inverter, and S ₃ is the upper switch on the right arm of the inverter, S ₄ is the lower switch on the right arm of the inverter, L _r is the resonant inductance, C _r is the resonant capacitor, L _m is the excitation inductance of the transformer, n is the transformer ratio, VD ₁ is the upper switch on the left bridge arm of the rectifier, VD ₂ is the lower switch on the left bridge arm of the rectifier, VD ₃ is the upper switch on the right bridge arm of the rectifier, VD ₄ is the lower switch on the right bridge arm of the rectifier, C is the output capacitance, R is the DC load;

The variable circle center average geometric control phase-shifting soft start flow chart of the embodiment of the present invention is shown in Figure 2, which includes the following steps:

Step 1: The controller calculates the resonant frequency and constructs a voltage gain model, sets the switching frequency of the inverter to the resonant frequency, sets the phase shift angle to zero, and calculates the first half of the startup process through time domain analysis. The instantaneous current values of the output capacitor at multiple times during the cycle are further calculated to calculate the average current value of the output capacitor during the first half cycle of the startup process;

The resonant frequency mentioned in step 1 is:

Among them, f _r =100kHz, C _r =196nF, L _r =12.9μH;

The switching frequency mentioned in step 1 is:

f _s = f _r

Among them, f _s =100kHz;

The voltage gain model described in step 1 is:

M＝nV _o /V _in

Among them, M represents the voltage gain, n represents the transformation ratio of the transformer, V _o represents the DC voltage of the output capacitor, and V _in represents the input DC voltage;

Calculate the average current of the output capacitor during the first half cycle of the startup process as described in step 1, as follows:

Among them, h is the number of uniformly distributed time points in the first half cycle, and i _Cj represents the instantaneous value of the output capacitor current at the jth time point in the first half cycle.

Step 2: Calculate equivalent inductance, equivalent angular frequency, reference voltage, reference impedance, and reference current;

The equivalent inductance calculated in step 2 is:

T _s =1/f _s

Among them, L _AM =31.89μH, n=0.5, _fs = _fr =100kHz, _Ts =10μs, C=200μF, _ICAM0 =0.9016, V _in =23V, arccos(*) represents inverse cosine calculation;

The equivalent angular frequency calculated in step 2 is:

Among them, ω _AM =6260.8rad/s, L _AM =31.89μH, n=0.5, C=200μF;

Calculate the reference voltage as described in step 2, as follows:

V _base =V _in /n;

Among them, V _base =46V, V _in =23V, n =0.5;

Calculate the reference impedance as described in step 2, as follows:

Among them, Z _base =0.799Ω, C=200μF, L _AM =31.89μH, n=0.5;

Calculate the reference current as described in step 2, as follows:

I _base = V _base /Z _base

Among them, I _base =57.60A, V _base =46V, Z _base =0.799Ω;

The primary side equivalent inductance L _AM and the capacitance C constitute the second-order equivalent circuit model as shown in Figure 3, where n is the transformation ratio of the transformer, MV _in represents the equivalent model input voltage, and the current source I _o is the load current. The startup phase I _o is small and can be regarded as a constant.

Step 3: Use the DC voltage of the output capacitor as the X-axis and the average current of the output capacitor as the Y-axis to construct a trajectory plane coordinate system. Select the DC voltage of the output capacitor as 0 and the average current of the output capacitor as 0 as the trajectory plane coordinate system. The origin of running time;

The limit value of the average current value of the output capacitor described in step 3 is defined as: I _th =0.0408 (unit value);

Calculate the initial number of arcs as described in step 3, as follows:

Among them, k=1, m=25;

Calculate the center point of each arc as described in step 3, as follows:

((ki-k+1)I _th ,0)

i∈[1,25]

Among them, (0.0408i,0) represents the coordinate point of the center of the i-th arc in the trajectory plane coordinate system;

Calculate the central angle of each arc as described in step 3, as follows:

in, arccos(*) represents arccosine calculation, k=1;

Calculate the running time corresponding to each arc as described in step 3, specifically:

t _i =θ _i /ω _AM

in, ω _AM =6260.8rad/s;

The first arc trajectory described in step 3 is shown in Figure 4, where i _CAM is the average current of the output capacitor, I _th is the limit value of the average current of the output capacitor, V _o is the output voltage, and kM ₁ is The distance between each arc segment, θ ₁ is the central angle of the first arc segment;

The i-th arc trajectory described in step 3 is shown in Figure 5, where i _CAM is the average current of the output capacitor, I _th is the limit value of the average current of the output capacitor, V _o is the 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: Combine the multi-segment arc described in step 3 and add the final arc trajectory according to the arc distance determination model, and calculate the total number of arcs, the running time of each arc segment of the final arc trajectory, and update the multi-segment arc The running time of the last arc in the arc;

The details of step 4 are as follows:

because The final arc trajectory is composed of the m+1th arc segment;

Among them, I _th =0.0408, k = 1, m = 25;

The coordinates of the center of the m+1 arc in the trajectory plane coordinate system are (-1,0);

The total number of arcs is calculated as follows:

N＝m+1＝26

The calculation of the final arc running time is as follows:

Among them, t _m =3.929×10 ^-7 s, t _m+1 =2.826×10 ^-6 s, arccos(*) represents arccosine calculation;

The final arc trajectory in step 4 is shown in Figure 7, where i _CAM is the average current of the output capacitor, I _th is the limit value of the average current of the output capacitor, V _o is the output voltage, and M _m is the th The centers of m arcs; if step 4 satisfies the criteria, the end arc trajectory is shown in Figure 6.

Step 5: Assign the X-axis coordinates of the center of each arc described in Step 3 to the voltage gain in turn, calculate the phase shift angle of each arc through time domain analysis, and convert the final arc described in Step 4 The phase shift angle of each arc segment of the arc trajectory is set to 0. The controller combines the running time of each arc segment described in step 3 and the running time of each arc segment of the final arc trajectory described in step 4. Generate the switch control signal of the inverter during the startup process, and perform inversion control of the inverter based on the switch control signal of the inverter during the startup process; after the end of the arc trajectory ends with a period of arc running time, the controller controls Inverter steady-state output;

Figure 8 shows a schematic diagram of a phase-shifted dynamic circular trajectory according to an embodiment of the present invention. Among them, i _CAM is the average current of the output capacitor, I _th is the limit value of the average current of the output capacitor, _Vo is the output voltage, M ₁ is the center of the first arc, and θ ₁ is the first arc. The central angle of , θ _i is the central angle of each arc;

The switching control signal of the inverter during the startup process is generated as described in step 5, as follows:

The switch on the left arm of the inverter is defined as S ₁ ;

The switch under the left arm of the inverter is defined as S ₂ ;

The switch on the right arm of the inverter is defined as S ₃ ;

The switch under the right bridge arm of the inverter is defined as S ₄ ;

The controller starts from the running time of the first arc segment to the end of the running time of the N-1 arc segment. During the running time of each arc segment, the switch control signals of S ₁ , S ₂ , S ₃ and S ₄ account for The empty ratio is 50%;

The angle by which the switch control signal of S ₄ lags behind the switch control signal of S ₁ is equal to the phase shift angle of each arc segment. The switch control signals of S ₂ and S ₃ are in phase with the switch control signals of S ₁ and S ₄ respectively;

The controller controls all S ₁ , S ₂ , S ₃ and S ₄ to turn off during the running time of the Nth arc;

N represents the total number of arcs obtained in step 4;

The controller described in step 5 controls the steady-state output of the inverter, as follows:

The duty cycle of the switch control signals of S ₁ , S ₂ , S ₃ and S ₄ output by the controller is all 50%;

Among them, the switch control signal of S ₁ is in the same phase as the switch control signal of S ₄ , the switch control signal of S ₂ is inverse phase with the switch control signal of S ₁ , and the switch control signal of S ₃ is inverse phase with the switch control signal of S ₄ respectively. Mutually.

Figure 9 is a simulation waveform of the startup process of the embodiment of the present invention. In the waveform, the rising process of the output voltage V _o , the average value of the output capacitor charging current i _CAM and the input current i _Lr of the resonant cavity are basically the same as the arc trajectory of the present invention. Consistent, it can be verified that the soft start method of the present invention can realize the rapid and smooth start of the resonant converter.

It should be understood that parts not elaborated in this specification belong to the prior art.

Although this article uses terms such as controller, inverter, resonant capacitor, resonant inductor, transformer, rectifier, output capacitor, load resistor, etc., it does not exclude the possibility of using other terms. The use of these terms is only for the purpose of describing the essence of the present invention more conveniently. Interpreting them as any additional limitations is contrary to the spirit of the present invention.

It should be understood that the above description of the preferred embodiments is relatively detailed and cannot therefore be considered to limit the scope of patent protection of the present invention. Those of ordinary skill in the art, under the inspiration of the present invention, may not deviate from the claims of the present invention. Within the scope of protection, substitutions or modifications can be made, all of which fall within the scope of protection of the present invention. The scope of protection claimed by the present invention shall be determined by the appended claims.

Claims (8)

1. A variable circle center average geometric control phase-shifting soft start system, which is characterized by including: Controller, inverter, resonant capacitor, resonant inductor, transformer, rectifier, output capacitor, load resistor; The resonant capacitor, resonant inductor and primary winding of the transformer are connected in series and further connected to the AC output end of the inverter; The AC input terminal of the rectifier is connected to the secondary winding of the transformer; The output capacitor is connected in parallel with the load resistor and then connected to the DC output terminal of the rectifier; The controller calculates the resonant frequency and builds a voltage gain model, calculates equivalent inductance, equivalent angular frequency, reference voltage, reference impedance, and reference current; constructs a trajectory plane coordinate system, and calculates the initial number of arcs, each arc in the trajectory plane coordinate system The center point of the arc segment and the central angle of each arc segment are further calculated to calculate the running time of each arc segment; the trajectory of the last arc segment is added based on the arc distance determination model based on the arc distance determination model, and the total number of arcs and the final arc are calculated. The running time of each arc segment of the arc trajectory is updated, and the running time of the last arc segment among the multiple arc segments is updated; the controller combines the running time of each arc segment and the running time of each arc segment of the final arc trajectory. The time generates the switching control signal of the inverter during the starting process, and combines the switching control signal of the inverter during the starting process to perform inversion control of the inverter; after the end of the arc trajectory ends with a period of arc running time, the controller Control the steady-state output of the inverter. 2. A method for performing variable circle center average geometry control phase-shifting soft start using the variable circle center average geometry control phase-shifting soft start system according to claim 1, characterized in that it includes the following steps: Step 1: The controller calculates the resonant frequency and constructs a voltage gain model, sets the switching frequency of the inverter to the resonant frequency, sets the phase shift angle to zero, and calculates the first half of the startup process through time domain analysis. The instantaneous current values of the output capacitor at multiple times during the cycle are further calculated to calculate the average current value of the output capacitor during the first half cycle of the startup process; Step 2: Calculate equivalent inductance, equivalent angular frequency, reference voltage, reference impedance, and reference current; Step 3: Use the DC voltage of the output capacitor as the X-axis and the average current of the output capacitor as the Y-axis to construct a trajectory plane coordinate system. Select the DC voltage of the output capacitor to be zero and the average current value of the output capacitor to be zero as the trajectory plane coordinate system. The origin of , set the limit value of the average current of the output capacitor, calculate the initial number of arcs, the center of each arc, and the central angle of each arc in the trajectory plane coordinate system, and further calculate the operation hours; Step 4: Combine multiple arcs and add the final arc trajectory based on the arc distance determination model, and calculate the total number of arcs, the running time of each arc in the final arc trajectory, and update the last segment of the multiple arcs. arc running time; Step 5: Assign the X-axis coordinate of the center of each arc to the voltage gain in turn, calculate the phase shift angle of each arc through time domain analysis, and then shift the phase of each arc in the final arc trajectory. The angles are all set to 0. The controller combines the running time of each arc segment and the running time of each arc segment of the final arc trajectory to generate the switching control signal of the inverter during the starting process, combined with the switching control of the inverter during the starting process. The signal performs inversion control of the inverter; after the last arc trajectory ends with a segment of arc running time, the controller controls the steady-state output of the inverter. 3. The variable circle center average geometric control phase-shifting soft start method according to claim 2, characterized in that: The resonant frequency mentioned in step 1 is: Among them, f _r represents the resonant frequency, C _r represents the capacitance of the resonant capacitor, and L _r represents the inductance of the resonant inductor; The switching frequency mentioned in step 1 is: f _s = f _r Among them, f _s represents the switching frequency; The voltage gain model described in step 1 is: M＝nV _o /V _in Among them, M represents the voltage gain, n represents the transformation ratio of the transformer, V _o represents the DC voltage of the output capacitor, and V _in represents the input DC voltage; Calculate the average current of the output capacitor during the first half cycle of the startup process as described in step 1, as follows: Among them, h is the number of uniformly distributed time points in the first half cycle, and i _Cj represents the instantaneous value of the output capacitor current at the jth time point in the first half cycle. 4. The variable center average geometric control phase-shifting soft start method according to claim 3, characterized in that: The equivalent inductance calculated in step 2 is: T _s =1/f _s Among them, L _AM represents the equivalent inductance, n represents the transformation ratio of the transformer, T _s represents the switching period of the inverter, C represents the capacitance of the output capacitor, and I _CAM0 represents the average current of the output capacitor in the first half cycle of the startup process. value, V _in represents the input DC voltage, arccos(*) represents the inverse cosine calculation, and f _s represents the switching frequency of the inverter; The equivalent angular frequency calculated in step 2 is: Among them, ω _AM represents the equivalent angular frequency, L _AM represents the equivalent inductance, C represents the capacitance of the output capacitor, and n represents the transformation ratio of the transformer; Calculate the reference voltage as described in step 2, as follows: V _base =V _in /n; Among them, V _base represents the reference voltage, n represents the transformation ratio of the transformer, and V _in represents the input DC voltage; Calculate the reference impedance as described in step 2, as follows: Among them, Z _base represents the base impedance, C represents the capacitance of the output capacitor, and L _AM represents the equivalent inductance; Calculate the reference current as described in step 2, as follows: I _base =V _in /Z _base Among them, I _base represents the base current. 5. The variable center average geometric control phase-shifting soft start method according to claim 4, characterized in that: The limit value of the average current of the output capacitor in step 3 is defined as: I _th ; Calculate the initial number of arcs as described in step 3, as follows: Among them, k represents the distance coefficient between adjacent circle centers, and m represents the initial number of arcs; Calculate the center point of each arc as described in step 3, as follows: ((ki-k+1)I _th ,0) i∈[1,m] Among them, ((ki-k+1)I _th ,0) represents the center point of the i-th arc segment at the coordinate point of the trajectory plane coordinate system, (ki-k+1)I _th represents the center point of the i-th arc segment at The X-axis coordinate of the trajectory plane coordinate system, 0 represents the Y-axis coordinate of the center of the i-th arc in the trajectory plane coordinate system, k represents the spacing coefficient between adjacent circle centers, and m represents the initial number of arcs; Calculate the central angle of each arc as described in step 3, as follows: Among them, θ _i represents the central angle of the i-th arc, k represents the center distance coefficient, and arccos(*) represents the inverse cosine calculation; Calculate the running time of each arc as described in step 3, specifically: t _i =θ _i /ω _AM Among them, t _i is the running time of the i-th arc, θ _i represents the central angle of the i-th arc, and ω _AM is the equivalent angular frequency. 6. The variable center average geometric control phase-shifting soft start method according to claim 5, characterized in that: The details of step 4 are as follows: like The final arc trajectory consists of the m+1 arc segment and the m+2 arc segment; Among them, I _th is the limit value of the average current of the output capacitor, k is the spacing coefficient between adjacent circle centers, and m is the initial number of arcs; The coordinates of the center of the m+1 arc in the trajectory plane coordinate system are (1,0); The coordinates of the center of the m+2 arc in the trajectory plane coordinate system are (-1,0); The total number of arcs is calculated as follows: N＝m+2 Among them, N represents the total number of arcs, and m is the initial number of arcs; The calculation of the running time of each arc segment of the final arc trajectory is as follows: Among them, ρ _m+1 is the radius of the m+1 arc, t _m+1 is the running time of the m+1 arc, t _m+2 is the running time of the m+2 arc, arccos (*) represents arc cosine calculation, arctg (*) represents arc tangent calculation, I _th is the limit value of the average current of the output capacitor, k is the spacing coefficient between adjacent circle centers, m is the initial number of arcs, ω _AM represents etc. Effective angular frequency; t _m is the running time of the m-th arc and remains unchanged; like The final arc trajectory is composed of the m+1th arc segment; The coordinates of the center of the m+1 arc in the trajectory plane coordinate system are (-1,0); The total number of arcs is calculated as follows: N＝m+1 Among them, N represents the total number of arcs, and m is the initial number of arcs; The calculation of the final arc running time is as follows: Among them, t _m is the running time of the m-th arc segment, t _m+1 is the running time of the m+1-th arc segment, k is the spacing coefficient between adjacent circle centers, arccos(*) represents the inverse cosine calculation, and m is the circle The initial number of arcs, I _th is the limit value of the average current of the output capacitor, and ω _AM represents the equivalent angular frequency. 7. The variable circle center average geometric control phase-shifting soft start method according to claim 6, characterized in that: The switching control signal of the inverter during the startup process is generated as described in step 5, as follows: The switch on the left arm of the inverter is defined as S ₁ ; The switch under the left arm of the inverter is defined as S ₂ ; The switch on the right arm of the inverter is defined as S ₃ ; The switch under the right bridge arm of the inverter is defined as S ₄ ; The controller starts from the running time of the first arc segment to the end of the running time of the N-1 arc segment. During the running time of each arc segment, the switch control signals of S ₁ , S ₂ , S ₃ and S ₄ account for The empty ratio is 50%; The angle by which the switch control signal of S4 lags behind the switch control signal of S1 is equal to the phase shift angle of each arc. The switch control signal of _S2 is inverse phase with the switch control signal of _S1 . The switch control signal of _S3 is in phase with the switch control signal of _S4 . The switch control signal is inverted; The controller controls all S ₁ , S ₂ , S ₃ and S ₄ to turn off during the running time of the Nth arc; N represents the total number of arcs. 8. The variable circle center average geometric control phase-shifting soft start method according to claim 7, characterized in that: The controller described in step 5 controls the steady-state output of the inverter, as follows: The duty cycle of the switch control signals of S ₁ , S ₂ , S ₃ and S ₄ output by the controller is all 50%; Among them, the switch control signal of _S1 is in the same phase as the switch control signal of _S4 , the switch control signal of _S2 is inverted with the switch control signal of _S1 , and the switch control signal of _S3 is inverted with the switch control signal of _S4 .