Control circuit, inverter, and energy storage device

Abstract

A control circuit (123) of an inverter (12), comprising: a control signal generator (1232g), configured to output a first control signal, such that a DC-DC converter (121) outputs a second direct current voltage, and update the first control signal to a second control signal, so as to reduce the magnitude of the ripple current of the second direct current voltage.

Description

Control circuits, inverters and energy storage devices

[0001] Priority information

[0002] This application claims priority and benefits of patent application No. 202311141339.9 filed with the State Intellectual Property Office of China on September 5, 2023, and the entire text of which is incorporated herein by reference. Technical Field

[0003] The present application relates to the technical field of inverters, and in particular to a control circuit, an inverter, and an energy storage device. Background Art

[0004] With the development of new energy technologies, inverters have become more widely used. Bidirectional inverters can receive electricity from the grid and output it to energy storage batteries to charge them, or receive electricity from energy storage batteries and feed it back into the grid. However, bidirectional inverters typically include an AC-DC converter and a DC-DC converter. When the bidirectional inverter charges the energy storage battery, current ripple is generated at the DC output of the AC-DC converter. After further conversion by the DC-DC converter, the charging current provided to the energy storage battery by the DC-DC converter also generates current ripple, resulting in a lower charging current for the energy storage battery and reducing its charging efficiency. Furthermore, external devices connected to the battery will be affected by the current ripple and may malfunction.

[0005] Summary of the Invention

[0006] In view of the above problems, the present application provides a control circuit, an inverter and an energy storage device, which can reduce the amplitude of the current ripple output by the DC-DC converter, thereby improving the charging efficiency of the energy storage battery and enhancing the safety and stability of electrical equipment.

[0007] In a first aspect, the present application provides a control circuit for an inverter. The inverter includes an AC-DC converter and a DC-DC converter. The AC-DC converter is used to receive an input voltage and convert the input voltage into a first DC voltage. The DC-DC converter is used to convert the first DC voltage into a second DC voltage and charge a battery via the second DC voltage. The AC-DC converter includes at least four switching tubes, and the DC-DC converter includes at least two switching tubes. The control circuit includes: a main controller, which is used to output a DC-DC startup signal in response to the first DC voltage being greater than or equal to a preset value. A PR controller, which is used to output a ripple suppression indication signal based on a parameter of the input voltage in response to the DC-DC startup signal. A control signal generator is connected to the PR controller and the main controller. The control signal generator is used to output a first control signal in response to the DC-DC startup signal. The first control signal is used to control the on and off of at least two switching tubes in the DC-DC converter so that the DC-DC converter outputs a second DC voltage. The control circuit provided herein can update the first control signal used to control the DC-DC converter based on grid parameters, thereby effectively reducing the current ripple amplitude in the second DC voltage while the DC-DC converter normally outputs the second DC voltage, thereby reducing the impact of current ripple on battery charging and electrical appliances.

[0008] In one possible implementation, the control circuit further includes a zero-crossing signal controller connected to the main controller and the control signal generator. The zero-crossing signal controller is configured to respond to a DC-DC startup signal and output a zero-crossing indication signal based on input voltage parameters. The control signal generator is further configured to update the first control signal to a third control signal in response to the zero-crossing indication signal. The third control signal is configured to control the on / off switching of at least two switching transistors in the DC-DC converter and reduce the peak-to-peak value of the current ripple of the second DC voltage.

[0009] In one possible implementation, the resonant frequency of the PR controller is an integer multiple of the frequency of the input voltage.

[0010] In one possible implementation, the zero-crossing indication signal is used to indicate that a zero-crossing signal is superimposed on the second DC voltage, the frequency of the zero-crossing signal is the same as the frequency of the current ripple, the zero-crossing point of the zero-crossing signal partially coincides with the zero-crossing point of the current ripple, and the control signal generator updates the first control signal to a third control signal, including: adjusting the duty cycle of the first control signal according to the zero-crossing signal to update the first control signal to the third control signal.

[0011] In one possible implementation, the control circuit further includes a PI controller, connected to the control signal generator, configured to output a voltage adjustment signal based on the second DC voltage and a preset reference voltage, the voltage adjustment signal being used to adjust the amplitude of the second DC voltage. The control signal generator is further configured to update the first control signal to a fourth control signal in response to the voltage adjustment signal, the fourth control signal being used to adjust the amplitude of the second DC voltage.

[0012] In one possible implementation, the master controller is further configured to output an AC-DC startup signal in response to input voltage parameters satisfying battery charging parameters. The control signal generator is further configured to output an AC-DC control signal in response to the AC-DC startup signal. The AC-DC control signal is configured to control the on / off switching of at least two switching transistors in the AC-DC converter, causing the AC-DC converter to output a first DC voltage. The battery charging parameters include at least one of the battery's charging voltage, charging current, and charging power.

[0013] In one possible implementation, the master controller is further configured to output a shutdown signal in response to the battery charging to a state of charge greater than or equal to a threshold. The control signal generator is further configured to control at least two switching transistors in the AC-DC converter and the DC-DC converter to be continuously disconnected in response to the shutdown signal.

[0014] In one possible implementation, the inverter further includes bus capacitors and filter capacitors, and the control circuit further includes an acquisition circuit configured to acquire input voltage parameters. The acquisition circuit acquires a first DC voltage via the bus capacitors and a second DC voltage via the filter capacitors. The input voltage parameters include at least one of a frequency, a phase, and an angle of the power grid.

[0015] In a second aspect, the present application provides an inverter, which includes an AC-DC converter, a DC-DC converter, and a control circuit provided by any possible implementation of the first aspect.

[0016] In a third aspect, the present application provides an energy storage device, which includes a battery and an inverter such as any possible implementation of the second aspect, wherein the inverter is used to receive an input voltage and perform voltage conversion on the input voltage to charge the battery.

[0017] In addition, the beneficial effects obtained by each possible implementation method in the second and third aspects can refer to the beneficial effects obtained by the corresponding implementation method in the first aspect, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0019] FIG1 is a schematic diagram of the energy storage device provided in this application.

[0020] FIG2 is a schematic diagram of the inverter provided in this application.

[0021] FIG3 is a circuit diagram of a DC-DC converter and an AC-DC unit provided in this application.

[0022] FIG4 is a schematic diagram of a control circuit provided in this application.

[0023] FIG5 is a waveform diagram of the zero-crossing signal provided in this application.

[0024] FIG6 is a Bode diagram of a controller and a PR controller provided in this application.

[0025] FIG7 is a diagram of an output current waveform of the DC-DC converter provided in this application.

[0026] FIG8 is another output current waveform diagram of the DC-DC converter provided in this application. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present application will be clearly described below in conjunction with the drawings in the embodiments of the present application.

[0028] It is understood that the connection relationships described in this application refer to direct or indirect connections. For example, the connection between A and B can be either a direct connection between A and B or an indirect connection between A and B via one or more other electrical components. For example, A and C can be directly connected, and C can be directly connected to B, so that A and B are connected through C. It is also understood that the description of "A connecting to B" in this application can be a direct connection between A and B or an indirect connection between A and B via one or more other electrical components.

[0029] In the description of this application, unless otherwise specified, " / " means "or". For example, A / B can mean A or B. "And / or" in this document is simply a description of the association relationship between related objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone.

[0030] In the description of this application, words such as "first" and "second" are used only to distinguish different objects and do not limit the quantity or execution order. In addition, words such as "first" and "second" do not necessarily mean different. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions.

[0031] Please refer to FIG1 , which is a schematic diagram of an energy storage device 10 provided in this application. The energy storage device 10 includes a battery 11 and an inverter 12 .

[0032] The battery 11 is connected to the inverter 12. The battery 11 is used to receive electric energy output by other power sources through the inverter 12 for charging, or output the stored electric energy to other devices through the inverter 12 for discharging.

[0033] The inverter 12 is connected to an external device. The inverter 12 may be a bidirectional inverter circuit, and the external device may be an AC load, other energy storage devices, a power supply device, a power grid, etc. For example, when the inverter 12 is connected to an AC load, the inverter 12 may output the electric energy provided by the battery 11 to the AC load to provide AC power to the AC load. For another example, when the inverter 12 is connected to other energy storage devices, the inverter 12 may provide the electric energy output by the battery 11 to other energy storage devices, or output the electric energy stored in other energy storage devices to the battery 11 to realize the transfer of electric energy between different energy storage devices. For another example, when the inverter 12 is connected to the power grid, the inverter 12 may output the electric energy provided by the power grid 14 to the battery 11 to charge the battery 11, or incorporate the electric energy output by the battery 11 into the power grid.

[0034] In some embodiments, the energy storage device 10 further includes an electromagnetic compatibility (EMC) circuit 13, which is electrically connected between the inverter 12 and the power grid 14. The EMC circuit 13 is configured to receive the voltage and current provided by the power grid 14, perform signal processing such as filtering on the voltage and current provided by the power grid 14, and then output the results to the inverter 12. The EMC circuit 13 is also configured to receive the voltage and current output by the inverter 12, perform signal processing such as filtering on the voltage and current output by the inverter 12, and then incorporate the results into the power grid 14.

[0035] In some embodiments, the battery 11 may be a photovoltaic (PV) panel, a charging station, a charging base station, other energy storage equipment, or other equipment with a battery module, such as a car with a battery module. The AC load may also be an air conditioner, a refrigerator, a self-propelled device, etc., and the self-propelled device may be a lawn mower, a self-propelled vehicle, a cleaning robot, etc. The battery 11 in this application may be any suitable power supply device, and the AC load may also be any suitable load device, and this application does not specifically limit this.

[0036] Please refer to FIG2 , which is a schematic diagram of an inverter 12 provided in this application. The inverter 12 includes a DC-DC converter 121 , an AC-DC converter 122 , and a control circuit 123 .

[0037] The DC-DC converter 121 is connected between the battery 11 and the AC-DC converter 122. The DC-DC converter 121 is configured to receive the DC voltage output by the battery 11, perform voltage conversion on the DC voltage output by the battery 11, and output it to the AC-DC converter 122. The DC-DC converter 121 is also configured to receive the DC voltage output by the AC-DC converter 122, perform voltage conversion on the DC voltage output by the AC-DC converter 122, and output it to the battery 11 to charge the battery 11.

[0038] AC-DC converter 122 is connected to an external device or to the power grid 14 via the EMC circuit 13. AC-DC converter 122 is configured to receive the direct current (DC) output from DC-DC converter 121 and convert it into alternating current (AC) to provide AC power to an external device or to incorporate the AC power into the power grid 14 via the EMC circuit 13. AC-DC converter 122 is also configured to receive AC power from an external device or the power grid 14 via the EMC circuit 13 and convert the AC power into DC power for output to DC-DC converter 121.

[0039] In some embodiments, the external device may be a photovoltaic inverter or other device, and the AC-DC converter 122 may receive the AC voltage output by the photovoltaic inverter or the AC voltage provided by the power grid 14 as the input voltage of the AC-DC converter 122. The following embodiments are described using the AC voltage provided by the power grid 14 as an example of the input voltage. It should be understood that the AC voltage of the power grid 14 involved in the following embodiments can be replaced with an AC voltage provided by an external device, such as the output AC voltage of a photovoltaic inverter.

[0040] The control circuit 123 is connected to the DC-DC converter 121 and the AC-DC converter 122. The control circuit 123 is used to output a DC-DC control signal to the DC-DC converter 121 to control the on / off of the switch in the DC-DC converter 121, and to output an AC-DC control signal to the AC-DC converter 122 to control the on / off of the switch in the AC-DC converter 122.

[0041] Specifically, please refer to Figure 3, which is a circuit diagram of the DC-DC converter 121 and AC-DC converter 122 provided in this application. The DC-DC converter 121 includes switches Q1-Q8, a primary winding T1, and a secondary winding T2. The switches Q5-Q8, the primary winding, the secondary winding, and the capacitor connected to the switch Q5 constitute a full-bridge drive transformer. The switches Q1-Q4 constitute a synchronous rectification circuit. The AC-DC converter 122 includes switches Q9-Q12, a first inductor L1, a second inductor L2, and a filter capacitor C3. The switches Q9-Q12, the first inductor L1, the second inductor L2, and the filter capacitor C3 constitute a single-phase converter. Specifically, the switches Q9 and Q10 constitute a first bridge arm, with the switch Q9 being the upper arm switch of the first bridge arm and the switch Q10 being the lower arm switch of the first bridge arm. Switching tubes Q11 and Q12 form the second bridge arm. Switching tube Q11 is the upper arm switching tube of the second bridge arm, and switching tube Q12 is the lower arm switching tube of the second bridge arm. The midpoint of the first bridge arm is connected to an external device or to the power grid 14 via the first inductor L1 or the EMC circuit 13. The midpoint of the second bridge arm is connected to an external device or to the power grid 14 via the second inductor L2 or the EMC circuit 13. The ends of the first and second bridge arms are respectively connected to the ends of the DC bus. The ends of the DC bus are also connected to the bus capacitor C2.

[0042] The following describes the working principle of the inverter 12 by taking the inverter 12 receiving the voltage and current provided by the power grid 14 and charging the battery 11 as an example.

[0043] First, the voltage and current provided by the power grid 14 are transmitted to the AC-DC converter 122 via the EMC circuit 13. The EMC circuit 13 includes two output terminals. Through filter inductors L3 and L4, respectively provided at the two output terminals, and filter capacitor C4 connected to both ends of the power grid 14, the EMC circuit 13 filters and processes the voltage and current provided by the power grid 14 before transmitting the signals to the AC-DC converter 122.

[0044] Next, AC-DC converter 122, a single-phase converter consisting of switches Q9-Q12, a first inductor L1, a second inductor L2, and a filter capacitor C3, rectifies the AC power from EMC circuit 13, converting it into DC power before outputting it to DC-DC converter 121. The upper and lower switching transistors in the first arm, as well as the upper and lower switching transistors in the second arm, are connected to control circuit 123 and are turned on or off by AC-DC control signals output by control circuit 123. Specifically, the upper and lower switching transistors in the first arm are always turned on alternately, while the upper and lower switching transistors in the second arm are always turned on alternately, to convert the AC voltage into the first DC voltage. The control circuit 123 can update and adjust the duty cycle of the AC-DC control signal according to the power parameters such as voltage, phase, angle, current, etc. of the electrical signal output by the power grid 14, thereby adjusting the voltage of the direct current output by the AC-DC converter 122.

[0045] In some embodiments, the AC-DC converter 122 can implement a power factor correction (PFC) function, that is, the AC-DC converter 122 can be a PFC circuit. Specifically, the control circuit 123 can adjust the duty cycle of the AC-DC control signal based on power parameters such as the angle and frequency of the electrical signal output by the power grid 14, so that the input voltage and input current of the AC-DC converter 122 maintain a high degree of phase synchronization, thereby improving the power factor of the AC-DC converter 122, improving the energy conversion efficiency of the inverter 12, reducing the power consumption caused by the AC side voltage and current being out of sync with each other, and improving the energy utilization of the inverter 12.

[0046] In some embodiments, the AC-DC converter 122 may further include a rectifier bridge circuit, or include a larger number of switching tubes. For example, the AC-DC converter 122 may include six switching tubes, which form three switching tube bridge arms. The midpoint of each switching tube bridge arm receives one phase of the input voltage and outputs the voltage to the DC-DC converter 121 through the ends of the switching tube bridge arm. For another example, the AC-DC converter 122 may include eight switching tubes, which form four switching tube bridge arms. The midpoint of each switching tube bridge arm receives one phase of the input voltage and outputs the voltage to the DC-DC converter 121 through the ends of the switching tube bridge arm.

[0047] In some embodiments, the working state of the AC-DC converter 122 includes a normal working state and a stopped working state. Correspondingly, the type of the AC-DC control signal includes a first control sub-signal and a second control sub-signal. Among them, the first control sub-signal is used to control the AC-DC converter 122 to be in a normal working state, and the second control sub-signal is used to control the AC-DC converter 122 to be in a stopped working state. Among them, when the AC-DC converter 122 is in a normal working state, the switch tubes Q9-Q12 are turned on and off according to the preset switching frequency to achieve conversion between AC and DC. When the AC-DC converter 122 is in a stopped working state, the switch tubes Q9-Q12 are all continuously turned off to reduce the power consumption of the inverter 12. Specifically, the control circuit 123 can output the first control sub-signal or the second control sub-signal according to the power parameters such as voltage, current, phase, angle, etc. of the electrical signal output by the power grid 14. For example, in response to the voltage, current, phase, angle, and other power parameters of the electrical signal output by the power grid 14 meeting the charging parameters of the battery 11, the control circuit 123 outputs a first control sub-signal to the AC-DC converter 122 to control the AC-DC converter 122 to operate normally, thereby converting the alternating current from the EMC circuit 13 into direct current for output to the DC-DC converter 121. For another example, in response to the voltage, current, phase, angle, and other power parameters of the electrical signal output by the power grid 14 not meeting the charging parameters of the battery 11, the control circuit 123 outputs a second control sub-signal to the AC-DC converter 122 to control the AC-DC converter 122 to stop operating, thereby saving power used by the inverter 12. The charging parameters of the battery 11 may include at least one of the charging voltage, charging current, and charging power of the battery 11, and this application does not impose any limitations thereon.

[0048] Next, the DC-DC converter 121 converts the DC voltage output by the AC-DC converter 122 into a DC voltage through a full-bridge drive transformer and a synchronous rectification circuit formed by switches Q1-Q4, and outputs the converted voltage to both ends of the battery 11, thereby charging the battery 11. For example, the DC-DC converter 121 can convert the first DC voltage output by the AC-DC converter 122 into a second DC voltage, and charge the battery 11 with the second DC voltage.

[0049] In some embodiments, the DC-DC converter 121 may include a smaller number of switching tubes. For example, the DC-DC converter 121 may include two switching tubes, and the two switching tubes constitute a switching bridge arm. The midpoint of the switching bridge arm receives the output voltage of the AC-DC converter 122 and outputs direct current to the battery 11 through the two ends of the bridge arm of the switching tube.

[0050] In some embodiments, the working state of the DC-DC converter 121 includes a normal working state and a stopped working state. Correspondingly, the type of the DC-DC control signal includes a third control sub-signal and a fourth control sub-signal. Among them, the third control sub-signal is used to control the DC-DC converter 121 to be in a normal working state, and the fourth control sub-signal is used to control the DC-DC converter 121 to be in a stopped working state. Among them, when the DC-DC converter 121 is in a normal working state, the switch tubes Q1-Q8 are turned on and off according to the preset switching frequency to achieve conversion between different DC voltages. When the DC-DC converter 121 is in a stopped working state, all the switch tubes Q1-Q8 are continuously turned off to reduce the power consumption of the inverter 12.

[0051] Specifically, the control circuit 123 can change the type of DC-DC control signal based on the bus voltage. The bus voltage is the voltage across the bus capacitor C2. For example, in response to the bus voltage reaching a preset voltage value, the control circuit 123 outputs a third control sub-signal to the DC-DC converter 121 to control the DC-DC converter 121 to be in a normal operating state, thereby converting the DC voltage from the AC-DC converter 122 to provide DC power to the battery 11. For another example, in response to the bus voltage not reaching the preset voltage value, the control circuit 123 outputs a fourth control sub-signal to the DC-DC converter 121 to control the DC-DC converter 121 to be in a stopped state, thereby saving power usage of the inverter 12.

[0052] Specifically, in response to the first DC voltage output by the AC-DC converter 122 being greater than or equal to a preset value, the control circuit 123 may output a third control sub-signal to the DC-DC converter 121 to control the DC-DC converter 121 to operate normally, thereby converting the DC voltage from the AC-DC converter 122 to provide DC power to the battery 11. For another example, in response to the first DC voltage being less than a preset value, the control circuit 123 may output a fourth control sub-signal to the DC-DC converter 121 to control the DC-DC converter 121 to stop operating.

[0053] Specifically, the control circuit 123 may further output a third control sub-signal or a fourth control sub-signal to the DC-DC converter 121 based on the charging state of the battery 11. The charging state of the battery 11 includes the state of charge (SOC) of the battery 11 during the charging process. For example, in response to the battery 11 being charged to a SOC greater than or equal to a threshold, the control circuit 123 may output a fourth control sub-signal to the DC-DC converter 121 to control the DC-DC converter 121 to be in a stopped state.

[0054] In some embodiments, the control circuit 123 may further adjust parameters such as the duty cycle of the DC-DC control signal based on the output voltage of the DC-DC converter 121 to further adjust the output voltage of the DC-DC converter 121 through feedback. For example, in response to the output voltage of the DC-DC converter 121 not meeting the charging voltage of the battery 11, the control circuit 123 changes the duty cycle of the DC-DC control signal to adjust the output voltage of the DC-DC converter 121 until it meets the charging voltage of the battery 11.

[0055] However, based on the basic properties of the PFC circuit, the input power and output power of the AC-DC converter 122 are equal, wherein the input power P of the AC-DC converter 122 satisfies the following formula (1):

[0056] Among them, V max The peak voltage provided to the grid 14, I max is the peak current supplied by grid 14, and θ is the frequency of the electrical signal supplied by grid 14. It can be seen that the input power P of AC-DC converter 122 includes a power component at twice the frequency of the electrical signal supplied by grid 14. In other words, the DC output of AC-DC converter 122 includes current ripple at twice the power frequency. After further conversion by DC-DC converter 121, the charging current supplied to battery 11 by DC-DC converter 121 also generates current ripple, resulting in a lower charging current for battery 11 and reduced charging efficiency. Furthermore, external devices connected to battery 11 will be affected by the current ripple and may malfunction.

[0057] In view of the above problems, the present application provides a control circuit, an inverter and an energy storage device, which can generate a ripple suppression signal for partially offsetting the current ripple by setting a PR controller, so that the current ripple output by the DC-DC converter 121 can be effectively suppressed, thereby improving the charging efficiency of the battery 11 and enhancing the safety and stability of the electrical equipment.

[0058] Specifically, please refer to Figure 4, which is a schematic diagram of the control circuit 123 provided in this application. The control circuit 123 includes an AC-DC controller 1231, a DC-DC controller 1232, a master controller 1233, and an acquisition circuit 1234. The AC-DC controller 1231 is connected to the switch tubes Q9-Q12 in the AC-DC converter 122. The DC-DC controller 1232 is connected to the switch tubes Q1-Q8 in the DC-DC converter 121. The DC-DC controller 1232 is used to output a DC-DC control signal to the switch tubes Q1-Q8 in the DC-DC converter 121. The DC-DC control signal is used to control the on and off of the switch tubes Q1-Q8 in the DC-DC converter, so that the DC-DC converter 121 outputs a second DC voltage; the AC-DC controller 1231 is used to output the AC-DC control signal to the switch tubes Q9-Q12 in the AC-DC converter 122. The AC-DC control signal is used to control the on / off of the switches Q9 - Q12 in the AC-DC converter 122 , so that the AC-DC converter 122 outputs a first DC voltage.

[0059] The AC-DC controller 1231 includes an adder 1231a, a controller 1231b, an adder 1231c, a controller 1231d, and an AC-DC control signal generator 1231e. The adder 1231a is connected to the controller 1231b.

[0060] The adder 1231a receives the output voltage of the DC output side of the AC-DC converter 122 and the first voltage reference value, and subtracts the output voltage of the DC output side of the AC-DC converter 122 from the first voltage reference value to obtain a first voltage difference signal, and then outputs the first voltage difference signal to the controller 1231b.

[0061] The controller 1231b is connected to the adder 1231c and is configured to output a first current reference signal to the adder 1231c according to the first voltage difference signal.

[0062] Adder 1231c is connected to controller 1231d. Adder 1231c is configured to receive the first current reference signal and the input current from the AC input side of AC-DC converter 122, perform a subtraction operation on the first current reference signal and the input current from the AC input side of AC-DC converter 122, generate a first current difference signal, and output the first current difference signal to controller 1231d.

[0063] The controller 1231d is connected to the AC-DC control signal generator 1231e and is configured to output a first control instruction signal to the AC-DC control signal generator 1231e according to the first current difference signal.

[0064] The main controller 1233 is connected to the AC-DC control signal generator 1231e and the data acquisition circuit 1234. In response to the parameters of the power grid 14 meeting the charging parameters of the battery 11, the main controller 1233 is configured to output an AC-DC startup signal to the AC-DC control signal generator 1231e. The parameters of the power grid 14 may include power parameters such as the phase, angle, and frequency of the electrical signal provided by the power grid 14. The charging parameters of the battery 11 may include at least one of the charging voltage, charging current, and charging power of the battery 11. The data acquisition circuit 1234 may include sensors such as current sensors and voltage sensors to acquire the parameters of the power grid 14 and transmit the acquired parameters to the main controller 1233.

[0065] The AC-DC control signal generator 1231e can output an AC-DC control signal in response to the AC-DC start signal. The AC-DC control signal is used to control the on and off of the switch tubes Q9-Q12, so that the AC-DC converter 122 outputs the first DC voltage.

[0066] In some embodiments, the input end of the adder 1231a can be connected to the bus capacitor C2 via a voltage sensor to obtain the voltage across the bus capacitor C2 as the output voltage of the DC output side of the AC-DC converter 122. The input end of the adder 1231c can be connected to the first inductor L1 and / or the second inductor L2 via a current sensor to obtain the current value of the first inductor L1 and / or the second inductor L2 as the input current of the AC input side of the AC-DC converter 122.

[0067] In some embodiments, controller 1231b and controller 1231d may be proportional integral (PI) regulators. Thus, adder 1231a and controller 1231b form the voltage outer loop of a dual-loop control loop, while adder 1231c and controller 1231d form the current inner loop of the dual-loop control loop. The current difference signal indicates the current setpoint of the inner loop output by the voltage outer loop. This reduces the number of circuit components and simplifies the circuit structure and control strategy.

[0068] The DC-DC controller 1232 includes an adder 1232a, a controller 1232b, an adder 1232c, a controller 1232d, a proportional resonant (PR) controller 1232e, a zero-crossing signal controller 1232f, and a DC-DC control signal generator 1232g.

[0069] Adder 1232a is connected to controller 1232b. Adder 1232a receives the output voltage of DC-DC converter 121 and a second voltage reference value, performs a subtraction operation on the output voltage of DC-DC converter 121 and the second voltage reference value to obtain a second voltage difference signal, and then outputs the second voltage difference signal to controller 1232b.

[0070] The controller 1232b is connected to the adder 1232c and is configured to output a second current reference signal to the adder 1232c according to the second voltage difference signal.

[0071] Adder 1232c is connected to controller 1232d. Adder 1232c is configured to receive the second current reference signal and the input current from the input side of DC-DC converter 121, perform a subtraction operation on the second current reference signal from the output current from the output side of DC-DC converter 121, generate a second current difference signal, and output the second current difference signal to controller 1232d.

[0072] The controller 1232d is connected to the DC-DC control signal generator 1232g. The controller 1232d is configured to output a voltage adjustment signal according to the second current difference signal. The voltage adjustment signal is configured to adjust the amplitude of the second DC voltage.

[0073] The PR controller 1232e is connected to the DC-DC control signal generator 1232g. The PR controller 1232e can be configured to have a large signal gain property at the resonance point. Specifically, by configuring the resonant frequency and gain parameters of the PR controller 1232e, the PR controller 1232e can perform signal processing such as amplitude amplification on the signal near the resonant frequency, thereby suppressing the current ripple at twice the power frequency output by the DC-DC converter 121. For example, the resonant frequency of the PR controller 1232e can be configured as an integer multiple (e.g., twice) of the frequency of the electrical signal provided by the power grid 14, so that the PR controller 1232e can generate a ripple suppression indication signal and output the ripple suppression indication signal to the DC-DC control signal generator 1232g. The ripple suppression indication signal is used to adjust the duty cycle of the DC-DC control signal so that the current ripple at twice the power frequency in the output voltage of DC-DC converter 121 is subtracted from the ripple suppression signal indicated by the ripple suppression indication signal. As a result, the ripple suppression signal can partially offset the current ripple at twice the power frequency in the output voltage of DC-DC converter 121, thereby reducing the current ripple amplitude in the second DC voltage. Specifically, the ripple suppression signal has a larger amplitude at a frequency twice that of the electrical signal provided by power grid 14. Therefore, after the ripple suppression signal is subtracted from the current ripple at twice the power frequency, the current ripple amplitude at twice the power frequency in the output voltage of DC-DC converter 121 can be effectively reduced.

[0074] The zero-crossing signal controller 1232f is connected to the DC-DC control signal generator 1232g. The zero-crossing signal controller 1232f is used to generate a zero-crossing indication signal according to the power parameters such as the phase, angle, and frequency of the electric signal provided by the power grid 14. Wherein, the zero-crossing indication signal is used to adjust the duty cycle of the DC-DC control signal so that the second DC voltage output by the DC-DC converter 121 is superimposed on the zero-crossing signal to reduce the peak-to-peak value of the current ripple of twice the power frequency in the output voltage of the DC-DC converter 121. Specifically, the frequency of the zero-crossing signal is the same as the frequency of the current ripple, and the zero-crossing point of the zero-crossing signal partially overlaps with the zero-crossing point of the current ripple, so that the zero-crossing signal can be superimposed on the current ripple of twice the power frequency, so that the zero-crossing signal can partially offset the current ripple of twice the power frequency, and the peak-to-peak value of the current ripple of twice the power frequency is reduced.

[0075] The main controller 1233 is also connected to a DC-DC control signal generator 1232g, a PR controller 1232e, and a zero-crossing signal controller 1232f. The main controller 1233 is also configured to output a DC-DC startup signal to the DC-DC control signal generator 1232g in response to the first DC voltage being greater than or equal to a preset value. At this time, the PR controller 1232e outputs a ripple suppression indication signal based on the parameters of the power grid 14. The zero-crossing signal controller 1232f outputs a zero-crossing indication signal based on the parameters of the power grid 14. In this way, the main controller 1233 can start the PR controller 1232e, the DC-DC control signal generator 1232g, and the zero-crossing signal controller 1232f after the first DC voltage output by the AC-DC converter 122 meets the voltage requirements of the battery 11 and the DC-DC converter 121.

[0076] The DC-DC control signal generator 1232g is used to respond to the DC-DC start signal and output a DC-DC control signal to the switch tubes Q1-Q8 in the DC-DC converter 121 to control the switch tubes Q1-Q8 in the DC-DC converter 121 to be turned on and off according to a preset switching frequency, so that the DC-DC converter 121 outputs a second DC voltage to charge the battery 11.

[0077] DC-DC control signal generator 1232g is further configured to update the DC-DC control signal in response to the DC-DC startup signal and the ripple suppression indication signal. Specifically, if the DC-DC control signal is a first control signal, the DC-DC control signal updated according to the DC-DC startup signal and the ripple suppression indication signal is a second control signal. The second control signal is used to control the switching transistors Q1-Q8 in DC-DC converter 121 to switch on and off according to a preset switching frequency and to reduce the amplitude of the current ripple in the second DC voltage.

[0078] DC-DC control signal generator 1232g is further configured to update the DC-DC control signal in response to the DC-DC startup signal and the zero-crossing indication signal. Specifically, if the DC-DC control signal is the first control signal, the DC-DC control signal updated according to the DC-DC startup signal and the zero-crossing indication signal is the third control signal. The third control signal is used to control the switching transistors Q1-Q8 in DC-DC converter 121 to switch on and off according to a preset switching frequency and to reduce the peak-to-peak value of the current ripple in the second DC voltage.

[0079] In some embodiments, after the zero-crossing signal is superimposed on the current ripple at twice the power frequency, the frequency of the current ripple may change from twice the power frequency to four times the power frequency. At this time, the resonant frequency of the PR controller 1232e can be adjusted to four times the power frequency to better suppress the current ripple in the output voltage of the DC-DC converter 121.

[0080] In some embodiments, the DC-DC control signal generator 1232g can specifically calculate the duty cycle of the third control signal to be output based on the frequency, phase, amplitude and other power parameters of the zero-crossing signal indicated by the zero-crossing indication signal, thereby adjusting the duty cycle of the first control signal to update the first control signal to the third control signal.

[0081] In some embodiments, the DC-DC control signal generator 1232g is further configured to update the DC-DC control signal in response to the DC-DC startup signal and the voltage regulation signal. Specifically, if the DC-DC control signal is the first control signal, the DC-DC control signal updated according to the DC-DC startup signal and the voltage regulation signal is the fourth control signal. The fourth control signal is used to control the switching transistors Q1-Q8 in the DC-DC converter 121 to turn on and off according to a preset switching frequency and to adjust the amplitude of the second DC voltage.

[0082] In some embodiments, the main controller 1233 can also output a shutdown signal to the DC-DC control signal generator 1232g and the AC-DC control signal generator 1231e in response to the battery 11 being charged to a state of charge greater than or equal to a threshold, so that the DC-DC control signal generator 1232g and the AC-DC control signal generator 1231e respectively control the switch tubes Q1-Q8 and the switch tubes Q9-Q12 to be continuously disconnected to save power consumption of the inverter 12.

[0083] In some embodiments, the master controller 1233 may obtain power parameters such as the first DC voltage and the second DC voltage through the acquisition circuit 1234. The acquisition circuit 1234 may obtain the first DC voltage by measuring the voltage of the bus capacitor C2 through a voltage sensor, and may obtain the second DC voltage by measuring the voltage of the filter capacitor C1 through a voltage sensor.

[0084] Please refer to FIG5 , which is a waveform diagram of the zero-crossing signal provided by the present application. Taking 60A as the preset output current of the DC-DC converter 121, 27A as the ripple value of the current ripple, and f as the input voltage frequency of the AC-DC converter 122 as an example, the current ripple I of the output voltage of the DC-DC converter 121 at twice the power frequency is DC (f) satisfies formula (2) as follows: I DC (f)=60A+27sin(2f) (2)

[0085] Current value of zero-crossing signal I ADJ (f) satisfies formula (3) as follows: I ADJ (f) = -27sin(2f) (3)

[0086] However, after the input voltage has been converted by the AC-DC converter 122 and the DC-DC converter 121, and after filtering by components such as the inductor and capacitor, the angle of the current ripple at twice the power frequency in the output voltage of the DC-DC converter 121 will have a certain phase difference compared to the original input voltage, and the waveform will also be distorted to a certain extent. Therefore, the current ripple at twice the power frequency in the output voltage of the DC-DC converter 121 is not completely offset by the zero-crossing signal after being superimposed. In fact, the current ripple at twice the power frequency in the output voltage of the DC-DC converter 121 is superimposed by the zero-crossing signal to produce a ripple approximately four times the power frequency. The current value of the four times the power frequency ripple is I OUT (f) satisfies formula (4) as follows: I OUT (f) = I DC (f)+I ADJ (f)+6.6sin(4f+0.2) (4)

[0087] Among them, 0.2 is the phase difference between the angle of the current ripple at twice the industrial frequency in the output voltage of the DC-DC converter 121 and the original input voltage. This is only an example, and the phase difference can also be other values. This application does not impose any limitation.

[0088] It can be understood that after the current ripple at twice the power frequency in the output voltage of the DC-DC converter 121 is superimposed on the zero-crossing signal, although a ripple at four times the power frequency is generated, the peak-to-peak value of the ripple at four times the power frequency is 6.6 A, which is significantly lower than the peak-to-peak value of the current ripple at twice the power frequency before superposition.

[0089] Please refer to Figure 6, which is a Bode diagram of the controller 1232d and the PR controller 1232e provided in this application. Taking the controller 1232d as a PI controller and the resonant frequency of the PR controller 1232e as 100Hz as an example, it can be seen from Figure 7 that the controller 1232d and the PR controller 1232e have good gain as a whole in the low frequency band and the resonant frequency. For example, when the signal frequency is 1Hz, the overall gain of the controller 1232d and the PR controller 1232e to the signal is about 55dB, and when the signal frequency is 100Hz, the overall gain of the controller 1232d and the PR controller 1232e to the signal is about 40dB. Therefore, after the controller 1232d and the PR controller 1232e are combined, they have a good low-frequency gain effect and a good gain effect on DC signals, which can widen the output voltage range of the AC-DC converter 122 and adapt to the DC output voltage required by more application scenarios. Furthermore, the resonant frequency of the PR controller 1232 e can be set to indicate and generate a ripple suppression signal, thereby effectively suppressing the current ripple amplitude of twice the power frequency in the output voltage of the DC-DC converter 121 .

[0090] Please refer to Figure 7, which is an output current waveform diagram of the DC-DC converter 121 provided in this application. The solid line represents the DC component of the output current of the DC-DC converter 121, and the dotted line represents the current ripple when the zero-crossing signal is not superimposed and the ripple suppression signal is not subtracted.

[0091] As shown by the dotted line, when the output current of the DC-DC converter 121 is not superimposed with the zero-crossing signal and the ripple suppression signal is not subtracted, the frequency of the current ripple is twice the power frequency, and the amplitude is approximately 90A, and the peak-to-peak value is approximately 27.7A. Therefore, the amplitude and peak-to-peak value of the current ripple are both large, resulting in an increased charge and discharge depth of the filter capacitor C1, increased heat generation, and a shortened service life.

[0092] Please refer to Figure 8, which is another output current waveform diagram of the DC-DC converter 121 provided by the present application. The solid line represents the DC component of the output current of the DC-DC converter 121, and the dotted line represents the current ripple after superimposing the zero-crossing signal and subtracting the ripple suppression signal.

[0093] As shown by the dotted line, after time T1, the frequency of the current ripple changes from twice the power frequency to four times the power frequency after the output current of the DC-DC converter 121 is superimposed with the zero-crossing signal. When the ripple suppression signal is subtracted, the peak-to-peak value of the current ripple is reduced to 4 A, and the amplitude of the current ripple is further reduced.

[0094] Thus, the control circuit 123 provided by the present application can be provided with a PR controller 1232e and a zero-crossing signal controller 1232f to generate a ripple suppression indication signal and a zero-crossing indication signal respectively according to the parameters of the power grid 14, to respectively indicate the second DC voltage output by the DC-DC converter 121 minus the ripple suppression signal, and to superimpose the zero-crossing signal, thereby respectively reducing the amplitude and peak-to-peak value of the current ripple, so as to reduce the impact of the current ripple on the charging of the battery 11 and the impact on the electrical appliances connected to both ends of the battery 11, so that the current ripple can be suppressed without adding additional hardware equipment. At the same time, since the current ripple is effectively suppressed, the charging current of the battery 11 can be close to the maximum charging current, improving the charging safety and speed of the battery 11, and improving the charging efficiency of the battery 11. Moreover, while the current ripple is suppressed, the voltage ripple will also be suppressed synchronously, so that the electrical appliances connected to both ends of the battery 11 can obtain a more stable voltage, thereby improving the working stability of the electrical appliances. Similarly, the charge and discharge depth of the filter capacitor C1 connected to both ends of the battery 11 will also be reduced, heat will be reduced, and the service life will be further improved.

[0095] Those skilled in the art should recognize that the above embodiments are merely intended to illustrate the present application and are not intended to limit the present application. As long as they are within the spirit of the present application, appropriate changes and modifications to the above embodiments are within the scope of protection claimed in the present application.

Claims

1. A control circuit of an inverter, the inverter comprising an AC-DC converter and a DC-DC converter, the AC-DC converter is used to receive an input voltage and convert the input voltage into a first DC voltage, the DC-DC converter is used to convert the first DC voltage into a second DC voltage, and charge a battery through the second DC voltage, the AC-DC converter comprises at least four switch tubes, the DC-DC converter comprises at least two switch tubes, wherein: The control circuit comprises: A main controller, configured to output a DC-DC start signal in response to the first DC voltage being greater than or equal to a preset value; A PR controller, configured to respond to the DC-DC startup signal and output a ripple suppression indication signal according to a parameter of the input voltage; A control signal generator is connected to the PR controller and the master controller, and the control signal generator is used to: In response to the DC-DC start signal, output a first control signal, wherein the first control signal is used to control the on and off of the at least two switch tubes in the DC-DC converter so that the DC-DC converter outputs the second DC voltage; and In response to the ripple suppression indication signal, the first control signal is updated to a second control signal, wherein the second control signal is used to control the on and off of the at least two switching tubes in the DC-DC converter and reduce the amplitude of the current ripple of the second DC voltage.

2. The control circuit according to claim 1, wherein: The control circuit further comprises: A zero-crossing signal controller connected to the master controller and the control signal generator, the zero-crossing signal controller being used to respond to the DC-DC start signal and output a zero-crossing indication signal according to a parameter of the input voltage; The control signal generator is also used for: In response to the zero-crossing indication signal, the first control signal is updated to a third control signal, and the third control signal is used to control the on and off of the at least two switching tubes in the DC-DC converter and reduce the peak-to-peak value of the current ripple of the second DC voltage.

3. The control circuit according to claim 1 or 2, wherein: The resonant frequency of the PR controller is an integer multiple of the input voltage frequency.

4. The control circuit according to claim 2, wherein: The zero-crossing indication signal is used to indicate that a zero-crossing signal is superimposed on the second DC voltage, the frequency of the zero-crossing signal is the same as the frequency of the current ripple, the zero-crossing point of the zero-crossing signal partially coincides with the zero-crossing point of the current ripple, and the control signal generator updates the first control signal to a third control signal, including: The duty cycle of the first control signal is adjusted according to the zero-crossing signal to update the first control signal to the third control signal.

5. The control circuit according to any one of claims 1 to 4, wherein: The control circuit further comprises: a PI controller, connected to the control signal generator, and configured to output a voltage regulation signal according to the second DC voltage and a preset reference voltage, wherein the voltage regulation signal is used to adjust the amplitude of the second DC voltage; The control signal generator is also used for: In response to the voltage adjustment signal, the first control signal is updated to a fourth control signal, and the fourth control signal is used to adjust the amplitude of the second DC voltage.

6. The control circuit according to any one of claims 1 to 5, wherein: The master controller is also used for: In response to the input voltage parameter satisfying the battery charging parameter, outputting an AC-DC start signal; The control signal generator is also used for: In response to the AC-DC start signal, output an AC-DC control signal, wherein the AC-DC control signal is used to control the on and off of the at least two switch tubes in the AC-DC converter, so that the AC-DC converter outputs the first DC voltage; The charging parameters of the battery include at least one of the charging voltage, charging current and charging power of the battery.

7. The control circuit according to any one of claims 1 to 6, wherein: The master controller is also used for: In response to the battery being charged to a state of charge greater than or equal to a threshold, outputting a shutdown signal; The control signal generator is also used for: In response to the shutdown signal, the at least two switch tubes in the AC-DC converter and the DC-DC converter are controlled to be continuously disconnected.

8. The control circuit according to any one of claims 1 to 7, wherein: The inverter further includes a bus capacitor and a filter capacitor, and the control circuit further includes a collection circuit, which is used for: Obtaining parameters of the input voltage; collecting the first DC voltage through the bus capacitor; collecting the second DC voltage through the filter capacitor; The parameter of the input voltage includes at least one of the frequency, phase and angle of the input voltage.

9. An inverter, wherein: The inverter includes an AC-DC converter, a DC-DC converter and the control circuit according to any one of claims 1 to 8.

10. An energy storage device, wherein: The energy storage device comprises a battery and the inverter according to claim 9, wherein the inverter is used to receive an input voltage and perform voltage conversion on the input voltage to charge the battery.

Images