A control method of resonant converter parallel connection with adaptive droop coefficient

Abstract

The application discloses a control method of parallel connection of resonant converters with adaptive droop coefficients, and by adjusting the droop coefficients, the IPOP type direct current converter parallel connection control system can be switched between a current source mode CC and a voltage source mode CV, and the problem that the LLC resonant converters cannot realize the current source mode CC under the traditional droop control is solved. Meanwhile, based on the adaptive load change of the droop coefficients, the load switching between the current source mode CC and the voltage source mode CV can be realized with the characteristics of low output voltage adjustment rate and output current, and the advantages of the output current balance of the LLC resonant converters under the droop control are retained, and the method is suitable for the current balance control of the IPOP type resonant converter and other direct current converter parallel connection control systems.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of parallel technology of resonant converter, and particularly relates to a control method of parallel resonant converter with adaptive droop coefficient. BACKGROUND

[0002] With the development of economy, the demand for power supply capacity and function is increasing, such as electric vehicle charging and server base station construction. For example, the electric vehicle charging technology requires multiple charging modes such as constant current, constant voltage and constant power for power supply. The emergence of distributed system architecture has accelerated the development of modular technology of direct current power supply and the expansion and iterative update of power supply products. Compared with the centralized power supply system with poor safety and reliability, the distributed power supply system based on the combination of standard power supply modules in series and parallel has more outstanding advantages, which are as follows:

[0003] (1) Safety and reliability: the series-parallel system reduces the requirements for the withstand voltage, current and thermal stress of power devices. Compared with the centralized power supply system, the power of each module in the multi-module series-parallel combination system is small, which can prolong the service life of each module and improve the safety and reliability of the entire system.

[0004] (2) Redundancy: the redundancy technology between series-parallel combination modules can enhance the stability of the entire power supply system and avoid system paralysis and direct economic loss caused by single module failure in high-power application scenarios.

[0005] (3) Flexibility: the series-parallel combination method facilitates the standardization of direct current power supply modules and is more flexible in configuring system capacity according to load demand.

[0006] (4) Volume and weight: the upgrade of switching power devices makes the single-module direct current power supply gradually high-frequency, effectively reducing the size of the filter in the circuit topology, reducing the volume of the direct current power supply module and the weight of the direct current power supply.

[0007] Among the many methods of parallel power supply control technology, droop control has been widely studied by scholars due to its characteristics of achieving power sharing among LLC resonant converters without sharing current sharing information. However, the complex application environment in modern industrial environment requires more functions of power supply, which means that droop control needs to be improved to adapt to these new functions.

[0008] Although the current source mode CC and the current source mode CC have been realized in a single converter and master-slave control or other interconnected type converters, there are few applications of design in the mode of droop control. This is because the droop control is based on the improvement of the single closed loop of output voltage, and it is not easy to realize the working mode of current source. And the droop control itself will bring the instability of the output external characteristics caused by the change of load, which leads to the less application of the droop control in some occasions which require higher output voltage and need to realize constant current and constant power charging. If multiple sets of control programs are adopted to realize different functions, the difficulty of digital control and software design will be increased. SUMMARY

[0009] (I) The technical problems solved

[0010] In view of the defects of the prior art, the application discloses a control method of parallel LLC resonant converters with adaptive droop coefficient, which can realize the switching of LLC resonant converters in current source mode CC and voltage source mode CV by adjusting the droop coefficient, and solve the problem that the traditional LLC resonant converter cannot realize the current source mode CC under the control of the droop control. At the same time, based on the adaptive droop coefficient under the condition of load change, the load switching in the current source mode CC and the voltage source mode CV can have the characteristics of low output voltage regulation rate and output current, and the advantages of the output current balance of each LLC resonant converter under the control of the droop control are retained, which is suitable for the current sharing control of the IPOP type resonant converter and other DC converter parallel control system.

[0011] (II) Technical solutions

[0012] In order to realize the above purpose, the application provides a control method of parallel LLC resonant converters with adaptive droop coefficient, so as to solve the problem that the traditional LLC resonant converter cannot realize the current source mode CC under the control of the droop control.

[0013] The application discloses a control method of parallelly connected resonant converters with adaptive droop coefficients, and is designed for an IPOP type DC converter parallel control system, and comprises the following steps: a plurality of LLC resonant converters, a mode hysteresis comparator, input parallel connection and output parallel connection of each LLC resonant converter are connected to form the IPOP type DC converter parallel control system, the LLC resonant converters are switched between a current source mode CC and a voltage source mode CV by adjusting the droop coefficients, the output currents of the LLC resonant converters are compared by the mode hysteresis comparator to determine the conditions for the power supply to enter the current source mode CC and the voltage source mode CV, and the mode switching edge is prevented from oscillating to cause instability of the parallel system, meanwhile, the LLC resonant converters are controlled by using a frequency modulation mode, the zero voltage switching (ZVS) of the primary side switch tube of each LLC resonant converter is ensured by setting a proper frequency modulation interval and a dead time of the upper and lower tubes on the same bridge arm, and the efficiency of the system is ensured.

[0014] The application judges whether each LLC resonant converter works in the current source mode CC or the voltage source mode CV by the output current of the IPOP type DC converter parallel control system, adjusts the droop coefficients to make the output current-voltage characteristic of the IPOP type DC converter parallel control system work in the current source mode CC or the voltage source mode CV, and the specific steps are as follows:

[0015] S1: inputting the output current value of the IPOP type DC converter parallel control system into the mode hysteresis comparator to determine the current working state.

[0016] The output current value of the IPOP type DC converter parallel control system is input into the mode hysteresis comparator, if the output current is greater than the upper threshold value of the mode hysteresis comparator, the droop coefficient k is adjusted according to the criterion of the current source mode CC to make the system work in the current source mode CC, if the output current is less than the lower threshold value of the mode hysteresis comparator, the droop coefficient k is adjusted according to the criterion of the voltage source mode CV to make the system work in the voltage source mode CV, and if the output current is between the upper and lower threshold values of the mode hysteresis comparator, the working mode is determined according to the last working state.

[0017] S2: in the voltage source mode CV, the output voltage of the IPOP type DC converter parallel control system is used to adjust the droop coefficient to realize low output voltage regulation rate when the load is switched in the voltage source mode CV.

[0018] The initial reference value Vr of the outer loop output voltage of all LLC resonant converters is obtained. ef An increment AV is superimposed to obtain the reference voltage V of the new droop control loop. ref *The output voltage V of the control system is connected in parallel with the current IPOP type DC converter. o and the droop coefficient k and the current I of the current LLC resonant converter n on The difference between the products of (n = 1, 2, 3, ..., n) is used as the increment for the droop control loop. When the system is stable, we have:

[0019]

[0020] An adaptive droop adjustment loop is introduced to adjust the droop coefficient k, and k is used to stabilize the output voltage at the reference value V. ref The expression for k is:

[0021]

[0022] Where M CV It is the compensation coefficient of the droop coefficient adaptive adjustment stage under voltage source mode (CV).

[0023] Through these two adjustment loops, the output voltage V of the IPOP-type DC-DC converter can be controlled by the parallel control system. o Adjust to reference value V ref Simultaneously, by utilizing the current-sharing characteristics of droop control, the output current of each LLC resonant converter can be balanced, and the droop coefficient adaptively adjusts with load changes to achieve a low voltage regulation rate under voltage source mode CV load range. In steady state, we have:

[0024]

[0025]

[0026] S3: In current source mode CC, the output voltage of the parallel control system of the IPOP type DC converter is used to adjust the droop coefficient, thereby achieving a low output current regulation rate when switching loads in current source mode CC.

[0027] Initial reference value V for the outer loop output voltage of all LLC resonant converters ref By superimposing an increment ΔV, a new reference voltage V for the droop control loop is obtained. ref * The output voltage V of the control system is connected in parallel with the current IPOP type DC converter. o and the droop coefficient k and the current I of the current LLC resonant converter n on The difference between the products of (n = 1, 2, 3, ..., n) is used as the increment for the droop control loop. When the system is stable, we have:

[0028]

[0029] The droop coefficient adaptive adjustment loop is introduced to adjust the droop coefficient k, and the output current is stabilized at the reference value I by using k ref The expression of k is:

[0030]

[0031] Wherein M CC is the compensation coefficient of the droop coefficient adaptive adjustment link under the current source mode CC.

[0032] Through the two adjustment loops, the output current I o is adjusted to the reference value I ref , and the current balance of the LLC resonant converters can be realized by using the current balance feature of the droop control, and the low current regulation rate under the load range of the current source mode CC is realized by adaptively adjusting the droop coefficient with the load change, and the steady-state has:

[0033]

[0034] The application discloses a kind of resonant converter parallel control methods of adaptive droop coefficient, it has beneficial effects as follows:

[0035] (1) realize the parallel current sharing control between converter units of LLC resonant converter system, reduce the influence of system instability caused by communication, and the accumulation of output error between resonant converters caused by communication bandwidth;Through parallel current sharing control, the stress of current device between single LLC resonant converter is reduced, and the method is simple, easy to realize, shortens the development cycle of high-power power supply.

[0036] (2) realize the switching control of current source mode CC and voltage source mode CV to each LLC resonant converter of IPOP type resonant converter parallel system by droop control under no interconnection control, expand current source mode CC, solve the problem that each LLC resonant converter cannot enter current source mode CC under droop control.

[0037] (3) realize that control loop will not repeatedly determine control mode problem when current source mode CC or voltage source mode CV boundary switches. Meanwhile, this method can limit the maximum output power of power supply, switch to another control method when overload, protect power supply, improve the reliability of power supply. DETAILED DESCRIPTION

[0038] Figure 1 It is the structure schematic view of IPOP type direct current converter parallel control system of the control method of the application of adaptive droop coefficient resonant converter parallel;

[0039] Figure 2This is a flowchart of a parallel control method for resonant converters with adaptive droop coefficient according to the present invention;

[0040] Figure 3 This is a control block diagram of a parallel control method for a resonant converter with adaptive droop coefficient according to the present invention.

[0041] Figure 4 The output current-voltage characteristic curves of the parallel control method of the resonant converter with adaptive droop coefficient of the present invention are shown in current source mode CC and voltage source mode CV.

[0042] Figure 5 The present invention provides a control method for parallel resonant converters with adaptive droop coefficients. In voltage source mode (CV), the output current of each LLC resonant converter and the output voltage and current of the parallel control system of the IPOP DC converter are controlled when the load changes abruptly.

[0043] Figure 6 The present invention provides a control method for parallel resonant converters with adaptive droop coefficient. In current source mode CC, the output current of each LLC resonant converter and the output voltage and current of the parallel control system of the IPOP DC converter are controlled when the load changes abruptly.

[0044] Figure 7 The present invention provides a control method for parallel operation of resonant converters with adaptive droop coefficients. In voltage source mode (CV), when the load suddenly exceeds the output current limit of voltage source mode (CV) and automatically switches to current source mode (CC), the output current of each LLC resonant converter and the output voltage and current of the parallel control system of IPOP DC converters are controlled. Detailed Implementation

[0045] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments:

[0046] Please see Figures 1 to 7 The diagram illustrates a parallel control method for resonant converters with adaptive droop coefficients according to the present invention, comprising: multiple LLC resonant converters and a mode hysteresis comparator.

[0047] like Figure 1As shown, the LLC resonant converter includes a full-bridge switching circuit, a resonant capacitor Cr1, a resonant inductor Lr1, a magnetizing inductor Lrm1, a transformer T1, and a rectifier. The full-bridge switching circuit consists of a first switch Q11, a second switch Q12, a third switch Q13, and a fourth switch Q14. The first switch Q11 and the third switch Q13 are connected in series, and the second switch Q12 and the fourth switch Q14 are connected in series. They are then connected in parallel with the first capacitor Cr1 at the power input terminal. The magnetizing inductor Lrm1 is connected in parallel with the transformer T1. The resonant inductor Lrm1 is connected in parallel with the transformer T1. The inductor Lr1 is connected in series between the magnetizing inductor Lrm1 and the first switching transistor Q11. The resonant capacitor Cr1 is connected in series between the magnetizing inductor Lrm1 and the fourth switching transistor Q14. The rectifier consists of the first rectifier diode D11, the second rectifier diode D12, the third rectifier diode D13, and the fourth rectifier diode D14. The first rectifier diode D11 and the third rectifier diode D13 are connected in series, and the second rectifier diode D12 and the fourth rectifier diode D14 are connected in series. Then, they are connected in parallel with the second capacitor C01 at the power output terminal, and the output terminal is connected to the load RL.

[0048] like Figure 1 As shown, each LLC resonant converter is connected in parallel at both the input and output to form an IPOP-type DC-DC converter parallel control system. By adjusting the droop coefficient, each LLC resonant converter switches between current source mode (CC) and voltage source mode (CV), solving the problem that traditional droop control cannot achieve current source mode (CC). Furthermore, based on the adaptive load change of the droop coefficient, it can achieve low output voltage regulation and low output current during load switching between current source mode (CC) and voltage source mode (CV), while retaining the advantage of balanced output current across modules under droop control. This system is suitable for current sharing control of IPOP-type resonant converters and other IPOP-type DC-DC converter parallel control systems. In the IPOP-type DC-DC converter parallel control system, the output currents of multiple LLC resonant converters are compared using hysteresis. This is used to determine the conditions for the power supply to enter current source mode (CC) and voltage source mode (CV), preventing oscillations at the mode switching edge that could cause instability in the parallel system. For the parallel control system of IPOP-type DC-DC converters, phase-shifting and frequency-modulation control methods can be used for current sharing control. However, phase-shifting control has a large return power and cannot achieve zero-current switching of the secondary rectifier unit, resulting in low conversion efficiency of each LLC resonant converter. Therefore, frequency modulation is used to control each LLC resonant converter. By setting an appropriate frequency modulation range and the dead time of the upper and lower transistors in the same bridge arm, the zero-voltage turn-on (zvs) of the primary-side switching transistors of each LLC resonant converter is ensured, thus guaranteeing system efficiency. Setting an appropriate frequency modulation range allows each LLC resonant converter to operate in a state where the primary-side switching transistor is turned on at zero voltage and the secondary-side rectifier diode is turned off at zero current, improving the system's operating efficiency.

[0049] The primary side switch tube comprises a first switch tube Q11, a second switch tube Q12, a third switch tube Q13 and a fourth switch tube Q14.

[0050] The secondary side rectifier diode comprises a first rectifier diode D11, a second rectifier diode D12, a third rectifier diode D13 and a fourth rectifier diode D14.

[0051] As shown in the mode hysteresis comparator, the input end is connected to the power output end of the LLC resonant converter, and is used for sampling the total output current of the IPOP type DC converter parallel control system, and determines whether to adopt the current source mode CC or the voltage source mode CV through the output of 0 and 1, when the mode hysteresis comparator outputs 1, the current source mode CC is adopted, and when the mode hysteresis comparator outputs 0, the voltage source mode CV is adopted. Figure 1

[0052] As shown in the mode hysteresis comparator, the input end is connected to the power output end of the LLC resonant converter, and is used for sampling the total output current of the IPOP type DC converter parallel control system, and determines whether to adopt the current source mode CC or the voltage source mode CV through the output of 0 and 1, when the mode hysteresis comparator outputs 1, the current source mode CC is adopted, and when the mode hysteresis comparator outputs 0, the voltage source mode CV is adopted. Figure 2

[0053] S1: the output current value of the IPOP type DC converter parallel control system is input to the mode hysteresis comparator to determine the current working state:

[0054] The output current value of the IPOP type DC converter parallel control system is input to the mode hysteresis comparator, if the output current is greater than the upper threshold value of the mode hysteresis comparator, the droop coefficient k is adjusted according to the criterion of the current source mode CC, so that the system works in the current source mode CC, if the output current is less than the lower threshold value of the mode hysteresis comparator, the droop coefficient k is adjusted according to the criterion of the voltage source mode CV, so that the system works in the voltage source mode CV, and if the output current is between the upper and lower threshold values of the mode hysteresis comparator, the working mode is determined according to the last working state;

[0055] S2: in the voltage source mode CV, the droop coefficient is adjusted through the output voltage of the IPOP type DC converter parallel control system, so as to realize the low output voltage adjustment rate when the load is switched in the voltage source mode CV:

[0056] The initial reference value Vr of the outer ring output voltage of all LLC resonant converters is obtained. ef An increment△V is superimposed to obtain the reference voltage V of the new droop control loop. ref * ​​The output voltage V of the control system is connected in parallel with the current IPOP type DC converter. o and the droop coefficient k and the current I of the current LLC resonant converter n on The difference between the products of (n = 1, 2, 3, ..., n) is used as the increment for the droop control loop. When the system is stable, we have:

[0057]

[0058] An adaptive droop adjustment loop is introduced to adjust the droop coefficient k, and k is used to stabilize the output voltage at the reference value V. ref The expression for k is:

[0059]

[0060] Where M CV It is the compensation coefficient of the droop coefficient adaptive adjustment stage under voltage source mode (CV).

[0061] Through these two adjustment loops, the output voltage V of the IPOP-type DC-DC converter can be controlled by the parallel control system. o Adjust to reference value V ref Simultaneously, by utilizing the current-sharing characteristics of droop control, the output current of each LLC resonant converter can be balanced, and the droop coefficient adaptively adjusts with load changes to achieve a low voltage regulation rate under voltage source mode CV load range. In steady state, we have:

[0062]

[0063]

[0064] S3: In current source mode CC, the output voltage of the parallel control system of the IPOP type DC converter is used to adjust the droop coefficient, thereby achieving a low output current regulation rate when switching loads in current source mode CC.

[0065] Initial reference value V for the outer loop output voltage of all LLC resonant converters ref By superimposing an increment ΔV, a new reference voltage V for the droop control loop is obtained. ref * The output voltage V of the control system is connected in parallel with the current IPOP type DC converter. o and the droop coefficient k and the current I of the current LLC resonant converter n on The difference between the products of (n = 1, 2, 3, ..., n) is used as the increment for the droop control loop. When the system is stable, we have:

[0066]

[0067] The droop coefficient adaptive adjustment loop is introduced to adjust the droop coefficient k, and the output current is stabilized at the reference value I ref , and the expression of k is:

[0068]

[0069] where M CC is the compensation coefficient of the droop coefficient adaptive adjustment link under the current source mode CC.

[0070] Through the two adjustment loops, the output current I o is adjusted to the reference value I ref . Meanwhile, the current sharing characteristics of the droop control can be used to achieve the balance of the output currents of the LLC resonant converters, and the low current regulation rate under the load range of the current source mode CC is achieved through the adaptive adjustment of the droop coefficient with the load change, and the steady-state has:

[0071]

[0072] As shown in Figure 3 , the control method used by each resonant converter in the IPOP type DC converter parallel control system has two sets of control loops built-in, the mode selection loop determines the working mode of the IPOP type DC converter parallel control system, and the value of the updated droop coefficient is used to meet the current-voltage characteristics of the IPOP type DC converter parallel control system under the current mode, and the droop control loop is used to update the frequency of the primary side switch tube square wave signal, and the current sharing characteristics of each LLC resonant converter under various working modes and various load conditions are ensured by using the current sharing characteristics of the droop control.

[0073] As shown in Figure 4 , the current-voltage characteristic curve of the output port of the IPOP type DC converter parallel control system, under the voltage source mode CV, as the load increases, the droop coefficient is adaptively reduced, and the output voltage is stabilized at the preset value V ref When the mode switching point, i.e. the maximum power point, is crossed, the power supply is switched to the current source mode CC, and as the load increases, the droop coefficient is adaptively increased, and the output current I o is stabilized at the preset value I ref when the load changes under the current source mode CC.

[0074] As shown in Figure 5As shown in the voltage source mode CV, the load suddenly increases, the output current of each LLC resonant converter and the output voltage and current of the IPOP type DC converter parallel control system change, in the working condition of coping with the load step of the voltage source mode CV, the output current of each LLC resonant converter can be balanced, and the problem that the output voltage cannot reach the preset value under the traditional droop control when the load changes is overcome.

[0075] As shown in the voltage source mode CV, the load suddenly increases, the output current of each LLC resonant converter and the output voltage and current of the IPOP type DC converter parallel control system change, in the working condition of coping with the load step of the voltage source mode CV, the output current of each LLC resonant converter can be balanced, and the problem that the output voltage cannot reach the preset value under the traditional droop control when the load changes is overcome. Figure 6 As shown in the voltage source mode CV, the load suddenly increases, the output current of each LLC resonant converter and the output voltage and current of the IPOP type DC converter parallel control system change, in the working condition of coping with the load step of the voltage source mode CV, the output current of each LLC resonant converter can be balanced, and the problem that the output voltage cannot reach the preset value under the traditional droop control when the load changes is overcome.

[0076] As shown in the voltage source mode CV, the load suddenly increases, the output current of each LLC resonant converter and the output voltage and current of the IPOP type DC converter parallel control system change, in the working condition of coping with the load step of the voltage source mode CV, the output current of each LLC resonant converter can be balanced, and the problem that the output voltage cannot reach the preset value under the traditional droop control when the load changes is overcome. Figure 7 As shown in the voltage source mode CV, the load suddenly increases, the output current of each LLC resonant converter and the output voltage and current of the IPOP type DC converter parallel control system change, in the working condition of coping with the load step of the voltage source mode CV, the output current of each LLC resonant converter can be balanced, and the problem that the output voltage cannot reach the preset value under the traditional droop control when the load changes is overcome.

[0077] The working principle and process of the application are as follows:

[0078] By adjusting the droop coefficient, the IPOP type DC converter parallel control system can be switched between the current source mode CC and the voltage source mode CV, solving the problem that each LLC resonant converter cannot realize the current source mode CC under the traditional droop control. At the same time, based on the adaptive load change of the droop coefficient, the characteristics of low output voltage adjustment rate and output current can be realized when the load is switched between the current source mode CC and the voltage source mode CV, and the advantages of balanced output current of each LLC resonant converter under the droop control are retained, which is suitable for the demand of the LLC resonant converter and other resonant converters in the IPOP type DC converter parallel control system requiring to realize the current source mode CC and the voltage source mode CV.

Claims

1. A control method for parallel resonant converters with adaptive droop coefficient, characterized in that: This system includes multiple LLC resonant converters and mode hysteresis comparators. Each LLC resonant converter is connected in parallel at both the input and output sides to form an IPOP-type DC-DC converter parallel control system. The switching between current source mode (CC) and voltage source mode (CV) is achieved by adjusting the droop coefficient. In the IPOP-type DC-DC converter parallel control system, the output currents of multiple LLC resonant converters are compared using hysteresis to determine the conditions for the power supply to enter current source mode (CC) and voltage source mode (CV), preventing oscillations at the mode switching edges that could cause instability in the parallel system. Frequency modulation is used to control each LLC resonant converter. By setting appropriate frequency modulation intervals and dead time for the upper and lower transistors of the same bridge arm, zero-voltage turn-on (ZVS) of the primary-side switches of each LLC resonant converter is ensured, guaranteeing system efficiency. Setting appropriate frequency modulation intervals allows each LLC resonant converter to operate in a state where the primary-side switches are turned on at zero voltage and the secondary-side rectifier diodes are turned off at zero current, improving system operating efficiency. The output current of the parallel control system of the IPOP DC-DC converter is used to determine whether each LLC resonant converter operates in current source mode (CC) or voltage source mode (CV). The droop coefficient is then adjusted to make the output current-voltage characteristic of the parallel control system of the IPOP DC-DC converter operate in either current source mode (CC) or voltage source mode (CV). The specific steps are as follows: S1: Input the output current value of the parallel control system of the IPOP type DC converter to the mode hysteresis comparator to determine the current operating state: The output current value of the parallel control system of the IPOP type DC converter is used as the input of the mode hysteresis comparator. If the output current is greater than the upper threshold of the mode hysteresis comparator, the droop coefficient k is adjusted according to the current source mode CC criterion so that the system works in the current source mode CC. If the output current is less than the lower threshold of the mode hysteresis comparator, the droop coefficient k is adjusted according to the voltage source mode CV criterion to make the system work in voltage source mode CV; if the output current is between the upper and lower thresholds of the mode hysteresis comparator, the operating mode is determined according to the previous operating state. S2: In voltage source mode (CV), the output voltage of the parallel control system of the IPOP-type DC converter is used to adjust the droop coefficient, thereby achieving a low output voltage regulation rate when switching loads in voltage source mode (CV). Initial reference value V for the outer loop output voltage of all LLC resonant converters ref By superimposing an increment ΔV, a new reference voltage V for the droop control loop is obtained. ref * The output voltage V of the control system is connected in parallel with the current IPOP type DC converter. o and the droop coefficient k and the current I of the current LLC resonant converter n on The difference between the products (n=1,2,3......n) is used as the increment for the droop control loop. When the system is stable, we have: （1） An adaptive droop adjustment loop is introduced to adjust the droop coefficient k, and k is used to stabilize the output voltage at the reference value V. ref The expression for k is: （2） Where M CV It is the compensation coefficient of the droop coefficient adaptive adjustment stage under voltage source mode (CV). Through these two adjustment loops, the output voltage V of the IPOP-type DC-DC converter can be controlled by the parallel control system. o Adjust to reference value V ref Simultaneously, by utilizing the current-sharing characteristics of droop control, the output current of each LLC resonant converter can be balanced, and the droop coefficient adaptively adjusts with load changes to achieve a low voltage regulation rate under voltage source mode CV load range. In steady state, we have: （3） S3: In current source mode CC, the output voltage of the parallel control system of the IPOP type DC converter is used to adjust the droop coefficient, thereby achieving a low output current regulation rate when switching loads in current source mode CC. Initial reference value V for the outer loop output voltage of all LLC resonant converters ref By superimposing an increment ΔV, a new reference voltage V for the droop control loop is obtained. ref * The output voltage V of the control system is connected in parallel with the current IPOP type DC converter. o and the droop coefficient k and the current I of the current LLC resonant converter n on The difference between the products (n=1,2,3......n) is used as the increment for the droop control loop. When the system is stable, we have: （4） An adaptive droop coefficient adjustment loop is introduced to adjust the droop coefficient k, and k is used to stabilize the output current at the reference value I. ref The expression for k is: （5） Where M CC It is the compensation coefficient of the droop coefficient adaptive adjustment stage under current source mode CC; Through these two adjustment loops, the output current I can be adjusted. o Adjust to reference value I ref Simultaneously, by utilizing the current-sharing characteristics of droop control, the output current of each LLC resonant converter can be balanced. Furthermore, the droop coefficient is adaptively adjusted with load changes to achieve a low current regulation rate within the load range of the current source mode CC. In steady state, we have: （6）。 2. The control method for parallel operation of resonant converters with adaptive droop coefficient according to claim 1, characterized in that: The input terminal of the mode hysteresis comparator is connected to the power output terminal of the LLC resonant converter. It is used to sample the total output current of the parallel control system of the IPOP DC converter. The output 0 and 1 determine whether to use the current source mode CC or the voltage source mode CV. When the mode hysteresis comparator outputs 1, the current source mode CC is used. When the mode hysteresis comparator outputs 0, the voltage source mode CV is used.

Images