Current control method of resonance circuit, resonance circuit and energy storage inversion equipment

Abstract

The invention discloses a current control method of a resonant circuit, the resonant circuit and energy storage inversion equipment, the resonant circuit comprises a primary circuit, a secondary circuit, a resonant inductor and a resonant capacitor, the primary circuit is connected to the secondary circuit through the resonant inductor, the resonant capacitor is connected in parallel with the secondary circuit, the primary circuit is used for connecting a DC side, and the secondary circuit is used for connecting a DC side. The secondary circuit is used for connecting an AC side; the current control method comprises the steps of obtaining a first gain ratio according to a power grid voltage and a voltage gain ratio; obtaining a second gain ratio of the resonance current of the resonance circuit at a zero crossing point according to the voltage gain ratio, the resonance impedance and a preset maximum limit value of the resonance frequency; obtaining a target gain ratio according to the first gain ratio and the second gain ratio; obtaining a corresponding value of the resonance current amplitude based on the target gain ratio as a target current effective value; and adjusting working parameters of the primary circuit and the secondary circuit according to the target current effective value. The service life of the resonant circuit can be prolonged, and the quality of output electric energy of the resonant circuit is improved.

Description

Technical Field

[0001] The present application relates to the technical field of power conversion circuits, and in particular to a current control method of a resonant circuit, a resonant circuit, and an energy storage inverter device. Background Art

[0002] At present, resonant circuits are widely used in various devices with power conversion functions, such as energy storage inverter devices. In the existing resonant circuit, the secondary voltage is a time-varying quantity when working, which causes the current in the resonant inductor to also be a time-varying quantity. However, the prior art lacks means to optimize the current in the resonant inductor, which causes the output current in the resonant circuit to be distorted when crossing the zero point and generate a peak current, thereby affecting the life of the resonant circuit and the quality of its output power. Summary of the invention

[0003] In view of this, the present application provides a current control method of a resonant circuit, a resonant circuit and an energy storage inverter device, which are used to reduce the peak current caused by distortion when crossing the zero point, increase the life of the resonant circuit and improve the quality of the output power of the resonant circuit. The technical solution of the present application is as follows:

[0004] In a first aspect, the present application provides a current control method for a resonant circuit, wherein the resonant circuit comprises a primary circuit, a secondary circuit, a resonant inductor and a resonant capacitor, wherein the primary circuit is connected to the secondary circuit via the resonant inductor, the resonant capacitor is connected in parallel with the secondary circuit, the primary circuit is used to connect to a DC side, and the secondary circuit is used to connect to a power grid via an AC side; the current control method comprises: obtaining a resonant current amplitude of the resonant circuit, a resonant impedance, a power grid voltage of the power grid, and a voltage gain ratio between the primary circuit and the secondary circuit; obtaining a first gain ratio according to the power grid voltage and the voltage gain ratio; obtaining a second gain ratio of the resonant current of the resonant circuit at a zero-crossing point according to the voltage gain ratio, the resonant impedance and a preset maximum limit value of the resonant frequency; obtaining a target gain ratio according to the first gain ratio and the second gain ratio; obtaining a corresponding value of the resonant current amplitude based on the target gain ratio as a target current effective value under preset soft switching constraints; and adjusting the operating parameters of the primary circuit and the secondary circuit according to the target current effective value.

[0005] In one embodiment of the present application, obtaining the first gain ratio according to the grid voltage and the voltage gain ratio includes: constructing a first coefficient equation according to the grid voltage and a preset algorithm; and obtaining the first gain ratio according to the first coefficient equation and the voltage gain ratio.

[0006] In one embodiment of the present application, the second gain ratio of the resonant current of the resonant circuit at the zero-crossing point is obtained according to the voltage gain ratio, the resonant impedance and the preset maximum limit value of the resonant frequency, including: constructing a relationship between the resonant impedance and the resonant frequency of the resonant circuit; obtaining the corresponding inner phase shift angle and outer phase shift angle according to the relationship and the maximum limit value of the resonant frequency; constructing a second coefficient equation according to the inner phase shift angle and the outer phase shift angle; and obtaining the second gain ratio according to the second coefficient equation and the voltage gain ratio.

[0007] In one embodiment of the present application, obtaining the target gain ratio based on the first gain ratio and the second gain ratio includes: using the first gain ratio in the non-zero-crossing region of the resonant current and using the second gain ratio in the zero-crossing region of the resonant current to obtain the target gain ratio.

[0008] In one embodiment of the present application, obtaining the resonant current amplitude of the resonant circuit includes: obtaining an inner phase shift angle of the primary circuit, and an outer phase shift angle between the primary circuit and the secondary circuit; obtaining a DC voltage on the DC side, and an AC voltage on the AC side; obtaining a primary voltage based on the inner phase shift angle and the DC voltage, and obtaining a secondary voltage based on the outer phase shift angle and the AC voltage; and calculating and obtaining the resonant current amplitude of the resonant circuit based on the primary voltage and the secondary voltage.

[0009] In one embodiment of the present application, the primary voltage is obtained according to the inner phase shift angle and the DC voltage, and the secondary voltage is obtained according to the outer phase shift angle and the AC voltage, including: using the inner phase shift angle and the DC voltage to obtain an expression for the primary voltage based on the fundamental wave analysis method; using the outer phase shift angle and the AC voltage to obtain an expression for the secondary voltage based on the fundamental wave analysis method.

[0010] In one embodiment of the present application, obtaining the resonant current amplitude of the resonant circuit according to the primary voltage and the secondary voltage includes: obtaining a resonant current expression according to an expression of the primary voltage, an expression of the secondary voltage and the resonant impedance, wherein the resonant impedance is obtained based on the resonant inductor and the resonant capacitor; obtaining a current amplitude expression according to the resonant current expression, which is the resonant current amplitude.

[0011] In a second aspect, the present application provides a resonant circuit, including a primary circuit, a secondary circuit, a transformer, a resonant inductor, a resonant capacitor, and a controller, wherein the primary circuit is connected to the secondary circuit through the transformer and the resonant inductor, the resonant inductor is connected in series with the secondary circuit, the resonant capacitor is connected in parallel with the secondary circuit, the primary circuit is used to connect to a DC side, and the secondary circuit is used to connect to a power grid through an AC side; the controller is connected to the primary circuit and the secondary circuit, and the controller is used to obtain a resonant current amplitude, a resonant impedance, a power grid voltage of the power grid, and a voltage gain ratio between the primary circuit and the secondary circuit of the resonant circuit, obtain a first gain ratio according to the power grid voltage and the voltage gain ratio, obtain a second gain ratio of the resonant current of the resonant circuit at a zero crossing point according to the voltage gain ratio, the resonant impedance, and a preset maximum limit value of the resonant frequency, obtain a target gain ratio according to the first gain ratio and the second gain ratio, obtain a corresponding value of the resonant current amplitude based on the target gain ratio as a target current effective value under a preset soft switching constraint, and adjust the operating parameters of the primary circuit and the secondary circuit according to the target current effective value.

[0012] In one embodiment of the present application, the primary circuit is a full-bridge circuit, including a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a primary inductor and a primary capacitor; the first end of the first switch tube is used to connect the positive electrode of the DC side, and the second end of the first switch tube is connected to the first end of the second switch tube; the second end of the second switch tube is used to connect the negative electrode of the DC side; the first end of the third switch tube is connected to the first end of the first switch tube, and the second end of the third switch tube is connected to the first end of the fourth switch tube; the second end of the fourth switch tube is connected to the second end of the second switch tube; the first input end of the transformer is connected to the second end of the first switch tube, and the transformer The second input end of the transformer is connected to the second end of the third switch tube; the primary inductor is connected in parallel with the input end of the transformer; the primary capacitor is connected in parallel with the DC side; the secondary circuit is a half-bridge circuit, including a fifth switch tube, a sixth switch tube, a seventh switch tube and an eighth switch tube, and the resonant capacitor includes a first capacitor and a second capacitor; the fifth switch tube, the sixth switch tube, the seventh switch tube, the eighth switch tube, the second capacitor and the first capacitor are connected in series in sequence; the first output end of the transformer is connected between the sixth switch tube and the seventh switch tube through the resonant inductor, and the second output end of the transformer is connected between the first capacitor and the second capacitor.

[0013] A third aspect of the present application provides an energy storage inverter device, comprising the resonant circuit.

[0014] The present application obtains the resonant current amplitude of the resonant inductor in the resonant circuit, the grid voltage of the grid, and the voltage gain ratio of the primary circuit and the secondary circuit, obtains a first gain ratio according to the grid voltage and the voltage gain ratio, obtains a second gain ratio of the resonant current of the resonant circuit at the zero crossing point according to the voltage gain ratio, the resonant impedance and the preset maximum limit value of the resonant frequency, obtains a target gain ratio according to the first gain ratio and the second gain ratio, and then obtains the target current effective value corresponding to the target gain ratio based on the resonant current amplitude according to the soft switching constraint condition, and then adjusts the actual inductor current of the resonant inductor according to the target current effective value. Since the target gain ratio includes the first gain ratio, the harmonic distortion of the resonant current waveform can be reduced while reducing the conduction loss of each switch tube. Since the target gain ratio includes the second gain ratio, the peak current generated by the distortion at the zero crossing point can be reduced while reducing the harmonic distortion, thereby improving the quality of the output power of the resonant circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is an equivalent schematic block diagram of a resonant circuit provided in an embodiment of the present application.

[0016] Figure 2 It is a flow chart of a current control method of a resonant circuit provided in an embodiment of the present application.

[0017] Figure 3 It is a schematic diagram of a flow chart of obtaining the resonant current amplitude provided in an embodiment of the present application.

[0018] Figure 4 It is a schematic diagram of a flow chart for obtaining a primary voltage and a secondary voltage provided in an embodiment of the present application.

[0019] Figure 5 It is a schematic diagram of a flow chart of obtaining the resonant current amplitude provided in an embodiment of the present application.

[0020] Figure 6 It is a schematic diagram of a flow chart for obtaining a first gain ratio provided in an embodiment of the present application.

[0021] Figure 7 It is a schematic diagram of a flow chart for obtaining a second gain ratio provided in an embodiment of the present application.

[0022] Figure 8 It is a schematic block diagram of a resonant circuit provided in an embodiment of the present application.

[0023] Fig. 9 It is a circuit diagram of a resonant circuit provided in an embodiment of the present application. DETAILED DESCRIPTION

[0024] It should be noted that in the embodiments of the present application, "at least one" refers to one or more, and "more than one" refers to two or more than two. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: the existence of A alone, the existence of A and B at the same time, and the existence of B alone, where A and B can be singular or plural. The terms "first", "second", "third", "fourth", etc. (if any) in the specification, claims and drawings of this application are used to distinguish similar objects, rather than to describe a specific order or sequence.

[0025] It should also be noted that the method disclosed in the embodiments of the present application or the method shown in the flowchart includes one or more steps for implementing the method. Without departing from the scope of the claims, the execution order of multiple steps can be interchanged with each other, and some of the steps can also be deleted.

[0026] At present, resonant circuits are widely used in various devices with power conversion functions, such as energy storage inverter devices. In the existing resonant circuit, the secondary voltage is a time-varying quantity when working, which causes the current in the resonant inductor to also be a time-varying quantity. However, the prior art lacks means to optimize the current in the resonant inductor, which leads to high conduction loss of each switch tube in the resonant circuit, thereby affecting the working efficiency of the resonant circuit.

[0027] The embodiments of the present application provide a resonant circuit and a current control method thereof, which are used to reduce the peak current generated by distortion when crossing the zero point, increase the life of the resonant circuit, and improve the quality of the electrical energy output by the resonant circuit.

[0028] Please refer to Figure 1 , Figure 1 An equivalent schematic block diagram of a resonant circuit provided in an embodiment of the present application, wherein the resonant circuit 100 includes a primary circuit 110 , a secondary circuit 120 , a resonant inductor 130 and a resonant capacitor 140 .

[0029] In the embodiment of the present application, the primary circuit 110 is connected to the secondary circuit 120 via the resonant inductor 130, the resonant capacitor 140 is connected in parallel with the secondary circuit 120, the primary circuit 110 is used to connect the DC side, and the secondary circuit 120 is used to connect the AC side.

[0030] It can be understood that when the resonant circuit 100 is working, the DC voltage on the DC side is received through the primary circuit 110, and the DC voltage can be converted into a primary AC voltage and then transmitted to the secondary circuit 120 through the resonant inductor 130, and then the secondary circuit 120 adjusts the waveform of the primary AC voltage, and finally outputs the AC voltage to the AC side. Alternatively, the AC voltage on the AC side is received through the secondary circuit 120, and the AC voltage can be converted into a primary DC voltage and then transmitted to the primary circuit 110 through the resonant inductor 130, and then the primary circuit 110 adjusts the waveform of the primary DC voltage, and finally outputs the DC voltage to the DC side.

[0031] Next, combine Figure 1 A current control method for a resonant circuit provided in an embodiment of the present application is described. Please refer to Figure 2 , specifically including the following steps:

[0032] Step S21: obtaining the resonant current amplitude, the resonant impedance, the grid voltage of the grid, and the voltage gain ratio between the primary circuit and the secondary circuit of the resonant circuit.

[0033] In the embodiment of the present application, the resonant circuit can also be connected to a controller, which controls it to work and executes the various steps in the present embodiment. For example, in an energy storage inverter device provided with a resonant circuit, the primary circuit and the secondary circuit of the resonant circuit can be connected to the main controller of the energy storage inverter device, and the main controller of the energy storage inverter device controls the switching parameters of the primary circuit and the secondary circuit, thereby controlling them to work, and the main controller also executes the various steps in the present embodiment.

[0034] After controlling the resonant circuit to work, the controller can obtain the resonant current amplitude in the resonant inductor, the grid voltage, and the voltage gain ratio of the primary circuit and the secondary circuit. For example, a voltage sampling circuit can be provided in the resonant circuit to collect the grid voltage, the primary voltage, and the secondary voltage and transmit them to the controller. The controller calculates the resonant voltage based on the primary voltage and the secondary voltage, obtains the resonant current based on the resonant voltage and the impedance of the resonant circuit to obtain the resonant current amplitude, and the control circuit also obtains the above-mentioned voltage gain ratio based on the primary voltage and the secondary voltage.

[0035] Step S22: Obtain a first gain ratio according to the grid voltage and the voltage gain ratio.

[0036] Step S23: obtaining a second gain ratio of the resonant current of the resonant circuit at the zero-crossing point according to the voltage gain ratio, the resonant impedance and the preset maximum limit value of the resonant frequency.

[0037] Step S24: Obtain a target gain ratio according to the first gain ratio and the second gain ratio.

[0038] It can be understood that in the target gain ratio, the first gain ratio can be used in the non-zero-crossing region of the resonant current, so as to avoid the harmonic distortion of the calculated target current amplitude, and the second gain ratio can be used in the zero-crossing region of the resonant current, so as to avoid the distortion caused by the target current amplitude jumping and oscillating in the zero-crossing region.

[0039] Step S25: Under the preset soft switching constraint condition, a corresponding value of the resonant current amplitude based on the target gain ratio is obtained as a target current effective value.

[0040] It can be understood that the effective value of the current of the resonant inductor is positively correlated with the conduction loss of each switch tube in the resonant circuit. Therefore, under the soft switching condition constraint of the resonant circuit, a smaller target effective value of the current of the resonant inductor based on the target gain ratio is obtained. The actual inductor current of the resonant inductor is adjusted according to the target current effective value, which can reduce the conduction loss of each switch tube, thereby improving the working efficiency of the resonant circuit. In addition, the target gain ratio is composed of a first gain ratio and a second gain ratio. The first gain ratio can be used in the non-zero crossing region of the resonant current, and the second gain ratio can be used in the zero crossing region. While reducing harmonic distortion, the peak current generated by distortion at the zero crossing can also be reduced.

[0041] Step S26: adjusting the operating parameters of the primary circuit and the secondary circuit according to the target current effective value.

[0042] In an embodiment of the present application, after the controller obtains the target current effective value of the resonant inductor according to a preset current effective value algorithm, it can adjust the operating parameters of the primary circuit and the secondary circuit according to the target current effective value so that the current value of the resonant inductor gradually becomes equal to the target current effective value, thereby reducing the conduction loss of each switching tube, thereby improving the working efficiency of the resonant circuit.

[0043] In some embodiments, the controller can adjust the duty cycle and frequency of each switch tube in the primary circuit and the secondary circuit when they are turned on and off, thereby adjusting the current value of the resonant inductor. For example, when the controller outputs a PWM signal to each switch tube in the primary circuit and the secondary circuit for control, the controller can adjust the duty cycle and frequency of the PWM signal. When adjusting the duty cycle of the primary circuit and the secondary circuit, the controller can calculate the corresponding inner phase shift angle and outer phase shift angle according to the above target current effective value, and then control the above duty cycle according to the inner phase shift angle and the outer phase shift angle.

[0044] It can be understood that the present application obtains the resonant current amplitude of the resonant inductor in the resonant circuit, the grid voltage of the grid, and the voltage gain ratio of the primary circuit and the secondary circuit, obtains the first gain ratio according to the grid voltage and the voltage gain ratio, obtains the second gain ratio of the resonant current of the resonant circuit at the zero crossing point according to the voltage gain ratio, the resonant impedance and the preset maximum limit value of the resonant frequency, obtains the target gain ratio according to the first gain ratio and the second gain ratio, and then obtains the target current effective value corresponding to the target gain ratio based on the resonant current amplitude according to the soft switching constraint condition, and then adjusts the actual inductor current of the resonant inductor according to the target current effective value. Since the target gain ratio includes the first gain ratio, the harmonic distortion of the resonant current waveform can be reduced while reducing the conduction loss of each switching tube. Since the target gain ratio includes the second gain ratio, the peak current generated by the distortion when crossing the zero point can be reduced while reducing the harmonic distortion, thereby improving the quality of the output power of the resonant circuit.

[0045] In some embodiments, Figure 3 As shown, the above step S21 of obtaining the resonant current amplitude of the resonant circuit may also include the following steps:

[0046] Step S31: obtaining an inner phase shift angle of the primary circuit and an outer phase shift angle between the primary circuit and the secondary circuit.

[0047] In an embodiment of the present application, after controlling the resonant circuit to work, the controller can define a variable of the inner phase shift angle of the primary circuit and a variable of the outer phase shift angle between the primary circuit and the secondary circuit, so that after subsequently calculating the target current effective value of the resonant circuit, the corresponding inner phase shift angle and the corresponding outer phase shift angle can be obtained according to the target current effective value as working parameters to adjust the resonant circuit.

[0048] Step S32: obtaining the DC voltage on the DC side and the AC voltage on the AC side.

[0049] In the implementation of the present application, the controller may also be connected to the DC side and the AC side of the resonant circuit to obtain the DC voltage on the DC side and the AC voltage on the AC side. In some embodiments, a DC voltage sampling circuit may be provided on the DC side, and an AC voltage sampling circuit may be provided on the AC side, the DC voltage sampling circuit is used to collect the DC voltage on the DC side and transmit it to the controller, and the AC voltage sampling circuit is used to collect the AC voltage on the AC side and transmit it to the controller.

[0050] Step S33: obtaining the primary voltage according to the inner phase shift angle and the DC voltage, and obtaining the secondary voltage according to the outer phase shift angle and the AC voltage.

[0051] In an embodiment of the present application, after obtaining the inner phase shift angle and the DC voltage, the controller of the resonant circuit can calculate the primary voltage of the primary circuit based on the inner phase shift angle and the DC voltage; and after obtaining the outer phase shift angle and the AC voltage, the controller can calculate the secondary voltage of the secondary circuit based on the outer phase shift angle and the AC voltage.

[0052] Step S34: obtaining the resonant current amplitude of the resonant circuit according to the primary voltage and the secondary voltage.

[0053] It can be understood that both the primary voltage and the secondary voltage are AC voltages. In some embodiments, after calculating and obtaining the primary voltage and the secondary voltage, the controller can further obtain the resonant current amplitude of the resonant circuit according to the primary voltage and the secondary voltage. For example, the controller can calculate and obtain the resonant voltage of the resonant inductor according to the primary voltage and the secondary voltage, obtain the resonant current according to the resonant voltage and the impedance of the resonant inductor, and finally obtain the above-mentioned resonant current amplitude.

[0054] In some embodiments, Figure 4 As shown, the above step S33 of obtaining the primary voltage and the secondary voltage may also include the following steps:

[0055] Step S41: using the internal phase shift angle and the DC voltage to obtain an expression for the primary voltage based on the fundamental wave analysis method.

[0056] In the embodiment of the present application, the expression of the primary voltage constructed based on the fundamental wave analysis method can be:

[0057]

[0058] In the formula, v p is the primary voltage, V dc is the DC voltage on the DC side, n is the turns ratio of the transformer between the primary voltage and the transformed voltage, and D1 is the internal phase shift angle.

[0059] Step S42: using the external phase shift angle and the AC voltage to obtain an expression for the secondary voltage based on the fundamental wave analysis method.

[0060] In the embodiment of the present application, the expression of the secondary voltage constructed based on the fundamental wave analysis method can be:

[0061]

[0062] In the formula, v s is the secondary voltage, U g is the AC voltage on the AC side, and D2 is the external shift phase angle.

[0063] In some embodiments, Figure 5 As shown, the above step S34 of obtaining the resonant current amplitude may also include the following steps:

[0064] Step S51: obtaining a resonant current expression according to an expression of the primary voltage, an expression of the secondary voltage and the resonant impedance, wherein the resonant impedance is obtained based on the resonant inductance and the resonant capacitance.

[0065] In the embodiment of the present application, the resonant current expression based on the fundamental wave analysis method can be:

[0066]

[0067] Where i is the resonant current, X eq is the above-mentioned resonant impedance.

[0068] Step S52: Obtain a current amplitude expression according to the resonant current expression, which is the resonant current amplitude.

[0069] In the embodiment of the present application, the above formula can be written The current amplitude expression can be obtained as That is the above-mentioned resonant current amplitude.

[0070] In the present application embodiment, Figure 6 As shown, the above step S22 of obtaining the first gain ratio may further include the following steps:

[0071] Step S61: construct a first coefficient equation according to the grid voltage and a preset algorithm.

[0072] Step S62: Obtain a first gain ratio according to the first coefficient equation and the voltage gain ratio.

[0073] In the embodiment of the present application, the first coefficient equation k m Can be:

[0074]

[0075] Where m is the voltage gain ratio between the primary circuit and the secondary circuit.

[0076] like Figure 7 As shown, the above step S23 of obtaining the second gain ratio may further include the following steps:

[0077] Step S71: constructing a relationship between the resonant impedance and the resonant frequency of the resonant circuit.

[0078] In the embodiment of the present application, the relationship between the resonant impedance and the resonant frequency can be:

[0079]

[0080] Among them, X eq is the resonant impedance, I refis the resonant current, f is the resonant frequency, L k is the resonant inductor, C r is the resonant capacitor.

[0081] Step S72: Obtain corresponding inner phase shift angle and outer phase shift angle according to the relational expression and the maximum limit value of the resonant frequency.

[0082] Step S73: construct a second coefficient equation according to the inner phase shift angle and the outer phase shift angle.

[0083] Step S74: Obtain a second gain ratio according to the second coefficient equation and the voltage gain ratio.

[0084] The above-mentioned method of obtaining the target gain ratio based on the first gain ratio and the second gain ratio includes: using the first gain ratio in the non-zero-crossing region of the resonant current and using the second gain ratio in the zero-crossing region of the resonant current to obtain the target gain ratio. It can be understood that according to the resonant current expression The part of the resonant current related to the inner phase shift angle and the outer phase shift angle can be obtained, that is, the part related to the control amount is obtained as: Then we know that the soft switching condition is From the above, we can know that the resonant current amplitude is The part of the resonant current amplitude related to the inner phase shift angle and the outer phase shift angle is obtained, that is, the part related to the control amount is obtained as follows: Where m is the voltage gain ratio of the primary voltage to the secondary voltage.

[0085] Then in the non-zero crossing region of the resonant current, the soft switching constraint condition is satisfied. The resonant current amplitude corresponding to the minimum G value is A, which is the target current effective value. Among them, the maximum value of cos(πD1)cos(b) is 1, and through the target coefficient equation k m Can be constrained Not greater than 1, thereby avoiding harmonic distortion caused by oscillation of the calculated target current effective value.

[0086] It can be understood that in the non-zero crossing region of the resonant current, the above constraints In the equation, since the maximum value of cos(πD1)cos(b) is 1, There is a case where it is greater than 1. Greater than 1 and without the above coefficient k m The equation of the constraint condition has no solution, and this scheme is constructed and introduced into the coefficient k in the non-zero crossing area m , you can When greater than 1, the limit Equal to 1, thereby avoiding the constraint equation having no solution, causing the calculated target current effective value to generate harmonic distortion due to oscillation in the non-zero crossing area.

[0087] In the zero-crossing region of the resonant current, The optimal G value can be obtained, and the corresponding resonant current amplitude is A, which is the effective value of the target current, where h a That is, the second coefficient equation is constructed by the inner phase shift angle and the outer phase shift angle corresponding to the maximum limit value of the resonant frequency, so as to avoid the calculated target current effective value from generating a peak current due to a zero-crossing jump.

[0088] It can be understood that when the resonant current crosses the zero point region, the formula as well as It can be seen that the resonant impedance and the resonant frequency tend to infinity, which causes the current output by the resonant circuit to be unequal before and after the zero crossing, resulting in distortion and peak current. This scheme constructs and introduces the coefficient h in the zero crossing area. a , through the coefficient h a Transition to coefficient k m , due to the coefficient h a The method is constructed based on limiting the resonant frequency f to a maximum value, thereby preventing the calculated target current effective value from generating a peak current in the zero-crossing region due to a zero-crossing jump.

[0089] Please refer to Figure 8 An embodiment of the present application provides a schematic block diagram of a resonant circuit, wherein the resonant circuit 800 includes: a primary circuit 810, a secondary circuit 820, a transformer 830, a resonant inductor 840, a resonant capacitor 850 and a controller 860.

[0090] In the embodiment of the present application, the primary circuit 810 is connected to the secondary circuit 820 through the transformer 830 and the resonant inductor 840, the resonant inductor 840 is connected in series with the secondary circuit 820, the resonant capacitor 850 is connected in parallel with the secondary circuit 820, the primary circuit 810 is used to connect the DC side, and the secondary circuit 820 is used to connect the AC side;

[0091] The controller 860 is connected to the primary circuit 810 and the secondary circuit 820. The controller 860 is used to obtain the resonant current amplitude of the resonant inductor 840, the grid voltage of the power grid, and the voltage gain ratio between the primary circuit 810 and the secondary circuit 820. According to the grid voltage and the voltage gain ratio, the target gain ratio is obtained. Under the preset soft switching constraint conditions, the corresponding value of the resonant current amplitude based on the target gain ratio is obtained as the target current effective value, and the operating parameters of the primary circuit 810 and the secondary circuit 820 are adjusted according to the target current effective value.

[0092] In some embodiments, the controller 860 is further used to construct a first coefficient equation according to the grid voltage and a preset algorithm, and obtain a first gain ratio according to the first coefficient equation and the voltage gain ratio.

[0093] In some embodiments, the controller 860 is also used to construct a relationship between the resonant impedance and the resonant frequency of the resonant circuit, obtain the corresponding inner phase shift angle and outer phase shift angle according to the relationship and the maximum limit value of the resonant frequency, construct a second coefficient equation according to the inner phase shift angle and the outer phase shift angle, and obtain a second gain ratio according to the second coefficient equation and the voltage gain ratio.

[0094] In some embodiments, the controller 860 is further configured to adopt a first gain ratio in a non-zero-crossing region of the resonant current and a second gain ratio in a zero-crossing region of the resonant current to obtain a target gain ratio.

[0095] In some embodiments, the controller 860 is also used to: obtain the inner phase shift angle of the primary circuit 810, and the outer phase shift angle between the primary circuit 810 and the secondary circuit 820, obtain the DC voltage on the DC side, and the AC voltage on the AC side, obtain the primary voltage according to the inner phase shift angle and the DC voltage, obtain the secondary voltage according to the outer phase shift angle and the AC voltage, and obtain the resonant current amplitude of the resonant circuit according to the primary voltage and the secondary voltage.

[0096] In some embodiments, the controller 860 is further used to: obtain an expression of the primary voltage based on the fundamental wave analysis method using the inner phase shift angle and the DC voltage, and obtain an expression of the secondary voltage based on the fundamental wave analysis method using the outer phase shift angle and the AC voltage.

[0097] In some embodiments, the controller 860 is also used to: obtain a resonant current expression based on an expression of the primary voltage, an expression of the secondary voltage, and the resonant impedance, wherein the resonant impedance is obtained based on the resonant inductance and the resonant capacitance, and obtain a current amplitude expression based on the resonant current expression, which is the resonant current amplitude.

[0098] Please refer to Fig. 9 , Fig. 9 A circuit diagram of a resonant circuit 800 provided in an embodiment of the present application is shown in FIG. 810 , wherein the primary circuit 810 is a full-bridge circuit, including a first switch tube S1 , a second switch tube S2 , a third switch tube S3 , a fourth switch tube S4 , a primary inductor Lm and a primary capacitor Cdc.

[0099] In the embodiment of the present application, the first end of the first switch tube S1 is used to connect to the positive electrode of the DC side Vdc, and the second end of the first switch tube S1 is connected to the first end of the second switch tube S2; the second end of the second switch tube S2 is used to connect to the negative electrode of the DC side Vdc; the first end of the third switch tube S3 is connected to the first end of the first switch tube S1, and the second end of the third switch tube is connected to the first end of the fourth switch tube S4; the second end of the fourth switch tube S4 is connected to the second end of the second switch tube S2.

[0100] The first input end of the transformer 830 is connected to the second end of the first switch tube S1, and the second input end of the transformer 630 is connected to the second end of the third switch tube; the primary inductor Lm is connected in parallel with the input end of the transformer 830; and the primary capacitor Cdc is connected in parallel with the DC side Vdc.

[0101] Among them, the secondary circuit 820 is a half-bridge circuit, including a fifth switch tube S5, a sixth switch tube S6, a seventh switch tube S7 and an eighth switch tube S8, and the resonant capacitor 650 includes a first capacitor Cr1 and a second capacitor Cr2; the fifth switch tube S5, the sixth switch tube S6, the seventh switch tube S7, the eighth switch tube S8, the second capacitor Cr2 and the first capacitor Cr1 are connected in series in sequence; the first output end of the transformer 830 is connected between the sixth switch tube S6 and the seventh switch tube S7 through the resonant inductor 840, and the second output end of the transformer 830 is connected between the first capacitor Cr1 and the second capacitor Cr2.

[0102] It can be understood that the beneficial effects that can be achieved by the resonant circuit 800 of the embodiment of the present application can refer to the beneficial effects of the current control method of any of the aforementioned embodiments, and will not be repeated here.

[0103] In the embodiment of the present application, a more detailed functional description of each of the above modules can be referred to the corresponding content of the aforementioned part, which will not be repeated here.

[0104] An embodiment of the present application further provides a computer storage medium, which stores a computer program. When the computer program is executed by a processor, the processor executes the above-mentioned current control method.

[0105] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware or any combination thereof. When implemented using software, it can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, the process or function described in the embodiment of the present application is generated in whole or in part. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable devices. The computer instructions can be stored in a computer storage medium or transmitted through the computer storage medium. The computer instructions can be transmitted from a website site, computer, server or data center to another website site, computer, server or data center by wired (e.g., coaxial cable, optical fiber, digital subscriber line (Digital Subscriber Line, DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) mode. The computer storage medium can be any available medium that a computer can access or a data storage device such as a server, data center, etc. that contains one or more available media integrated. The available medium may be a magnetic medium (eg, a floppy disk, a hard disk, a magnetic tape), an optical medium (eg, a digital versatile disc (DVD)), or a semiconductor medium (eg, a solid state disk (SSD)).

[0106] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiments can be implemented by instructing the relevant hardware through a computer program, and the program can be stored in a computer-readable storage medium. When the program is executed, it can include the processes of the embodiments of the above-mentioned methods. The aforementioned storage medium includes: ROM, RAM, magnetic disk or optical disk and other media that can store program codes. In the absence of conflict, the technical features in this embodiment and the implementation scheme can be combined arbitrarily.

[0107] The embodiments described above are merely preferred embodiments of the present application and are not intended to limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements made to the technical solutions of the present application by ordinary technicians in this field should fall within the protection scope determined by the claims of the present application.

Claims

1. A current control method for a resonant circuit, characterized in that: The resonant circuit comprises a primary circuit, a secondary circuit, a resonant inductor and a resonant capacitor, the primary circuit is connected to the secondary circuit via the resonant inductor, the resonant capacitor is connected in parallel with the secondary circuit, the primary circuit is used to connect to the DC side, and the secondary circuit is used to connect to the power grid via the AC side; The current control method comprises: Acquiring a resonant current amplitude of the resonant circuit, a resonant impedance, a grid voltage of the grid, and a voltage gain ratio between the primary circuit and the secondary circuit; Obtaining a first gain ratio according to the grid voltage and the voltage gain ratio; Obtaining a second gain ratio of the resonant current of the resonant circuit at a zero-crossing point according to the voltage gain ratio, the resonant impedance and a preset maximum limit value of the resonant frequency; Obtaining a target gain ratio according to the first gain ratio and the second gain ratio; Under the preset soft switching constraint condition, obtaining the corresponding value of the resonant current amplitude based on the target gain ratio as the target current effective value; The operating parameters of the primary circuit and the secondary circuit are adjusted according to the target current effective value.

2. The control method according to claim 1, characterized in that: The step of obtaining a first gain ratio according to the grid voltage and the voltage gain ratio includes: Constructing a first coefficient equation according to the grid voltage and a preset algorithm; The first gain ratio is obtained according to the first coefficient equation and the voltage gain ratio.

3. The control method according to claim 2, characterized in that: The step of obtaining a second gain ratio of the resonant current of the resonant circuit at a zero-crossing point according to the voltage gain ratio, the resonant impedance and a preset maximum limit value of the resonant frequency includes: Constructing a relationship between the resonant impedance and the resonant frequency of the resonant circuit according to the resonant impedance; According to the relational expression and the maximum limit value of the resonant frequency, a corresponding inner phase shift angle and an outer phase shift angle are obtained; Constructing a second coefficient equation according to the inner phase shift angle and the outer phase shift angle; The second gain ratio is obtained according to the second coefficient equation and the voltage gain ratio.

4. The control method according to claim 1, characterized in that: The obtaining a target gain ratio according to the first gain ratio and the second gain ratio includes: The target gain ratio is obtained by adopting a first gain ratio in a non-zero-crossing region of the resonant current and a second gain ratio in a zero-crossing region of the resonant current.

5. The control method according to claim 1, characterized in that: The obtaining the resonant current amplitude of the resonant circuit includes: Acquire an inner phase shift angle of the primary circuit and an outer phase shift angle between the primary circuit and the secondary circuit; Acquiring a DC voltage on the DC side and an AC voltage on the AC side; Obtaining a primary voltage according to the inner phase shift angle and the DC voltage, and obtaining a secondary voltage according to the outer phase shift angle and the AC voltage; The resonant current amplitude of the resonant circuit is calculated based on the primary voltage and the secondary voltage.

6. The control method according to claim 5, characterized in that: The step of obtaining the primary voltage according to the inner phase shift angle and the DC voltage, and obtaining the secondary voltage according to the outer phase shift angle and the AC voltage, comprises: Obtaining an expression of the primary voltage based on a fundamental wave analysis method using the inner phase shift angle and the DC voltage; The external phase shift angle and the AC voltage are used to obtain an expression for the secondary voltage based on a fundamental wave analysis method.

7. The control method according to claim 6, characterized in that: The obtaining the resonant current amplitude of the resonant circuit according to the primary voltage and the secondary voltage comprises: Obtaining a resonant current expression according to the expression of the primary voltage, the expression of the secondary voltage and the resonant impedance, wherein the resonant impedance is obtained based on the resonant inductance and the resonant capacitance; The current amplitude expression is obtained according to the resonant current expression, which is the resonant current amplitude.

8. A resonant circuit, characterized in that: It includes a primary circuit, a secondary circuit, a transformer, a resonant inductor, a resonant capacitor and a controller, wherein the primary circuit is connected to the secondary circuit through the transformer and the resonant inductor, the resonant inductor is connected in series with the secondary circuit, the resonant capacitor is connected in parallel with the secondary circuit, the primary circuit is used to connect to the DC side, and the secondary circuit is used to connect to the power grid through the AC side; The controller is connected to the primary circuit and the secondary circuit, and is used to obtain the resonant current amplitude, resonant impedance, grid voltage of the grid, and voltage gain ratio of the primary circuit to the secondary circuit of the resonant circuit, obtain a first gain ratio according to the grid voltage and the voltage gain ratio, obtain a second gain ratio of the resonant current of the resonant circuit at a zero-crossing point according to the voltage gain ratio, the resonant impedance, and a preset maximum limit value of the resonant frequency, obtain a target gain ratio according to the first gain ratio and the second gain ratio, obtain the resonant current amplitude based on the target gain ratio as a target current effective value under preset soft switching constraints, and adjust the operating parameters of the primary circuit and the secondary circuit according to the target current effective value.

9. The resonant circuit according to claim 8, characterized in that The primary circuit is a full-bridge circuit, including a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a primary inductor and a primary capacitor; The first end of the first switch tube is used to connect the positive electrode of the DC side, and the second end of the first switch tube is connected to the first end of the second switch tube; the second end of the second switch tube is used to connect the negative electrode of the DC side; the first end of the third switch tube is connected to the first end of the first switch tube, and the second end of the third switch tube is connected to the first end of the fourth switch tube; the second end of the fourth switch tube is connected to the second end of the second switch tube; The first input end of the transformer is connected to the second end of the first switch tube, and the second input end of the transformer is connected to the second end of the third switch tube; the primary inductor is connected in parallel with the input end of the transformer; and the primary capacitor is connected in parallel with the DC side; The secondary circuit is a half-bridge circuit, including a fifth switch tube, a sixth switch tube, a seventh switch tube and an eighth switch tube, and the resonant capacitor includes a first capacitor and a second capacitor; The fifth switch tube, the sixth switch tube, the seventh switch tube, the eighth switch tube, the second capacitor and the first capacitor are connected in series in sequence; the first output end of the transformer is connected between the sixth switch tube and the seventh switch tube through the resonant inductor, and the second output end of the transformer is connected between the first capacitor and the second capacitor.

10. An energy storage inverter device, characterized in that: Comprising a resonant circuit as claimed in any one of claims 8 and 9.

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