Converter suitable for direct current and alternating current power grid energy conversion and control method thereof

Abstract

The invention discloses a converter adapting to direct current and alternating current power grid energy conversion and a control method thereof. The converter comprises a primary side control unit, a primary side switch unit, a secondary side control unit, a secondary side switch unit and a transformer. The secondary side of the transformer is provided with a tap; the power supply input end of the primary side switch unit is used for connecting a power supply, and the output end of the primary side switch unit is connected with the first acquisition end of the primary side control unit and the primary side of the transformer; the control input end of the primary side switch unit is connected with the first output end of the primary side control unit; the input end of the secondary side switch unit is connected with the secondary side of the transformer, and the output end of the secondary side switch unit and a tap of the transformer are respectively connected with two ends of a load to form a loop; a second acquisition end of the primary side control unit is used for being connected with a load and acquiring load electric signals; the control input end of the secondary side switch unit is connected with the data output end of the primary side control unit or the primary side of the transformer in a gating mode, and direct-current direct-current conversion and direct-current alternating-current conversion are achieved.

Description

Technical Field

[0001] This invention relates to the field of inverter technology, and in particular to a converter and its control method adapted to the energy conversion of DC and AC power grids. Background Technology

[0002] In existing technologies, to enable a power supply to connect to either AC or DC power grids simultaneously, two independent conversion devices (DC / DC and DC / AC) are typically required. However, configuring two independent systems not only increases configuration costs but also complicates system control. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a converter and its control method that can adapt to the energy conversion of DC and AC power grids, so as to realize DC-DC conversion and DC-AC conversion based on a set of equipment under different output demand scenarios.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A converter adaptable to DC and AC grid energy conversion includes a primary-side control unit, a primary-side switching unit, a secondary-side control unit, a secondary-side switching unit, and a transformer. The secondary side of the transformer has taps. The power input terminal of the primary-side switching unit is connected to a power source, and the output terminal of the primary-side switching unit is connected to both the first acquisition terminal of the primary-side control unit and the primary side of the transformer. The control input terminal of the primary-side switching unit is connected to the first output terminal of the primary-side control unit. The input terminal of the secondary-side switching unit is connected to the secondary side of the transformer, and the output terminal of the secondary-side switching unit and the taps of the transformer are used to connect to both ends of a load to form a loop. The second acquisition terminal of the primary-side control unit is connected to the load to acquire load electrical signals. The control input terminal of the secondary-side switching unit is selectively connected to either the data output terminal of the primary-side control unit or the primary side of the transformer.

[0005] To solve the above-mentioned technical problems, another technical solution adopted by the present invention is as follows: A control method for a converter adaptable to DC and AC grid energy conversion, applied to a converter as described above, the method comprising: Command to obtain output status; If the output status command is AC output, the control input terminal of the secondary-side switch unit is connected to the data output terminal of the primary-side control unit; the primary-side control unit generates a first switch signal based on the acquired load electrical signal and sends the first switch signal to the primary-side switch unit; and the secondary-side control unit generates a second switch signal based on the load electrical signal and sends the second switch signal to the secondary-side switch unit. If the output status command is a DC output, the control input terminal of the secondary-side switching unit is connected to the primary side of the transformer; the primary-side control unit generates a third switching signal based on the acquired load electrical signal and the current sampling value acquired by the first acquisition terminal, and sends the third switching signal to the primary-side switching unit; the secondary-side control unit acquires the primary-side signal, generates a fourth switching signal based on the primary-side signal, and sends the fourth switching signal to the secondary-side switching unit.

[0006] The principle of this invention is as follows: When the output status command is AC output, the control input terminal of the secondary-side switching unit is connected to the data output terminal of the primary-side control unit. At this time, the primary-side control unit generates a first switching signal (differential frequency control) based on the load electrical signal to control the primary-side switching unit. Through differential frequency control, the primary-side switching unit transforms the input DC current into a high-frequency AC current with a low-frequency envelope on the primary side of the transformer. The secondary-side control unit generates a second switching signal based on the load electrical signal to control the secondary-side switching unit, enabling the secondary-side switching unit to achieve synchronous rectification and polarity switching, thereby enabling the converter to achieve DC-AC conversion control.

[0007] When the output status command is DC output, the control input terminal of the secondary-side switching unit is connected to the primary side of the transformer. At this time, the primary-side control unit generates a third switching signal based on the load electrical signal and the signal acquired by the first acquisition terminal to control the primary-side switching unit, so that the primary-side switching unit forms a high-frequency AC current on the primary side of the transformer from the input DC power. The secondary-side control unit generates a fourth switching signal based on the acquired primary-side signal to control the secondary-side switching unit, so that the secondary-side switching unit rectifies the secondary side of the transformer to achieve DC power output, thereby enabling the converter to achieve DC-DC conversion control.

[0008] Thus, a single set of equipment can achieve DC-DC conversion and DC-AC conversion under different output demand scenarios.

[0009] The beneficial effects of this invention are as follows: By setting a primary-side control unit and a primary-side switching unit on the primary side of the transformer, and setting a secondary-side control unit and a secondary-side switching unit on the secondary side, and by setting taps on the secondary side of the transformer, the primary-side control unit collects primary-side data and load data, and generates corresponding control signals to instruct the primary-side switching unit to operate according to the corresponding switching mode, so that the primary side inputs the required electrical signal; and by selectively connecting the secondary-side control unit to the data output terminal of the primary-side control unit or the primary side of the transformer under different output conditions, the secondary-side control unit is connected to the primary side when outputting DC, and autonomously generates corresponding switching signals to control the secondary-side switching unit; when outputting AC, it is connected to the primary-side control unit, and the primary-side control unit inputs control signals to further generate switching signals to control the secondary-side switching unit, so that the primary and secondary sides of the transformer change in synergy, thereby realizing DC-DC conversion and DC-AC conversion based on a single device under different output demand scenarios. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of the module connection of a converter adapted to the energy conversion of DC and AC power grids according to an embodiment of the present invention; Figure 2 This is a topology diagram of a converter adapted to the energy conversion of DC and AC power grids according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the circuit topology of a control method for a converter adapted to DC and AC grid energy conversion according to an embodiment of the present invention when the output is AC. Figure 4 This is a schematic diagram of the control connection when the output of a converter adapted to the energy conversion of DC and AC power grids is AC, according to an embodiment of the present invention. Figure 5 This is a schematic diagram of the circuit topology of a control method for a converter adapted to DC and AC grid energy conversion according to an embodiment of the present invention when the output is DC. Figure 6 This is a schematic diagram of the control connection when the output of a converter adapted to DC and AC power grid energy conversion is DC, according to an embodiment of the present invention. Label Explanation: 1. Primary-side control unit; 2. Primary-side switching unit; 3. Secondary-side control unit; 4. Secondary-side switching unit; 5. Transformer. Detailed Implementation

[0011] To explain in detail the technical content, objectives, and effects of the present invention, the following description is provided in conjunction with the embodiments and accompanying drawings.

[0012] Definitions:

[0013] In related technologies, most converters, especially grid-connected inverters, are designed primarily to convert direct current (DC) into alternating current (AC) for transmission to the traditional AC power grid. That is, most converters are typically "unidirectional" or "single-mode," with one set of equipment serving only one type of grid. To enable a distributed power source to connect to both AC and DC grids simultaneously, two independent conversion devices are required: a DC / DC system and a DC / AC system. However, setting up two systems leads to overall system redundancy, increasing investment costs and floor space. Furthermore, the coordinated operation of the two systems introduces additional complexity, adding more components and connection points, potentially reducing overall system reliability.

[0014] To address the aforementioned technical problems, this invention proposes a universal isolated converter that can connect to renewable energy sources, energy storage, and different grid types. Through a single circuit structure and output interface, the converter can be connected to both DC microgrids and single-phase AC microgrids, adapting to both DC and AC grid energy conversion simultaneously via the same port. This significantly improves operational flexibility and reduces equipment redundancy.

[0015] A converter adapted to DC and AC power grid energy conversion includes a primary-side control unit, a primary-side switching unit, a secondary-side control unit, a secondary-side switching unit, and a transformer; the secondary side of the transformer is provided with taps. The power input terminal of the primary-side switching unit is used to connect to the power supply, and the output terminal of the primary-side switching unit is connected to the first acquisition terminal of the primary-side control unit and the primary side of the transformer, respectively; the control input terminal of the primary-side switching unit is connected to the first output terminal of the primary-side control unit. The input terminal of the secondary-side switching unit is connected to the secondary side of the transformer, and the output terminal of the secondary-side switching unit and the taps of the transformer are respectively used to connect to the two ends of the load to form a circuit. The second acquisition terminal of the primary-side control unit is used to connect to the load and acquire the load electrical signal; The control input terminal of the secondary-side switching unit is connected to the data output terminal of the secondary-side control unit or the primary-side gate of the transformer.

[0016] As described above, by setting a primary-side control unit and a primary-side switching unit on the primary side of the transformer, and setting a secondary-side control unit and a secondary-side switching unit on the secondary side, and by setting taps on the secondary side of the transformer, the primary-side control unit collects primary-side data and load data, and generates corresponding control signals to instruct the primary-side switching unit to operate according to the corresponding switching mode, so that the primary side inputs the required electrical signal; and by selectively connecting the secondary-side control unit to the data output terminal of the primary-side control unit or the primary side of the transformer under different output conditions, the secondary-side control unit is connected to the primary side when outputting DC, and autonomously generates corresponding switching signals to control the secondary-side switching unit; when outputting AC, it is connected to the primary-side control unit, and the primary-side control unit inputs control signals to further generate switching signals to control the secondary-side switching unit, so that the primary and secondary sides of the transformer change in tandem, thereby realizing DC-DC conversion and DC-AC conversion based on a single set of equipment under different output demand scenarios.

[0017] Another embodiment of the present invention provides a control method for a converter adapted to DC and AC grid energy conversion, applied to a converter adapted to DC and AC grid energy conversion as described above, the method comprising: Command to obtain output status; If the output status command is AC output, the control input terminal of the secondary-side switch unit is connected to the data output terminal of the primary-side control unit; the primary-side control unit generates a first switch signal based on the acquired load electrical signal and sends the first switch signal to the primary-side switch unit; and the secondary-side control unit generates a second switch signal based on the load electrical signal and sends the second switch signal to the secondary-side switch unit. If the output status command is a DC output, the control input terminal of the secondary-side switching unit is connected to the primary side of the transformer; the primary-side control unit generates a third switching signal based on the acquired load electrical signal and sends the third switching signal to the primary-side switching unit; the secondary-side control unit acquires the primary-side signal, generates a fourth switching signal based on the primary-side signal, and sends the fourth switching signal to the secondary-side switching unit.

[0018] As described above, after receiving the output status command, if the output status command is AC output, the control input terminal of the secondary-side switching unit is connected to the data output terminal of the primary-side control unit. The primary-side control unit and the secondary-side control unit generate the first and second switching signals according to the load electrical signal, respectively, and send them to the primary-side switching unit and the secondary-side switching unit, respectively, so that the converter can realize DC-AC conversion control. If the output status command is DC output, the control input terminal of the secondary-side switching unit is connected to the primary side of the transformer. The primary-side control unit generates the third switching signal according to the load electrical signal and sends it to the primary-side switching unit, and the secondary-side control unit generates the fourth switching signal according to the primary-side signal and sends it to the secondary-side switching unit, so that the converter can realize DC-DC conversion control. Thus, a single device can realize DC-DC conversion and DC-AC conversion under different output demand scenarios.

[0019] In one embodiment of this application, the primary-side control unit generates a first switching signal based on the load electrical signal, comprising: The primary control unit acquires the current signal in the load electrical signal, performs orthogonal signal processing on the current signal to obtain the static current orthogonal component corresponding to the current signal; and acquires the grid angle, grid frequency and rotating voltage orthogonal component in the load electrical signal according to the phase-locked loop. The first switching signal is generated based on the orthogonal component of the quiescent current, the grid angle, the grid frequency, and the voltage component.

[0020] As described above, by extracting the quiescent current quadrature component of the current signal and obtaining the grid angle, grid frequency, and rotating voltage quadrature components through a phase-locked loop, the first switching signal for the next moment can be obtained based on the current output state, thereby achieving dynamic adjustment of the output state.

[0021] In one embodiment of this application, generating the first switching signal based on the orthogonal component of the quiescent current, the grid angle, the grid frequency, and the rotating voltage component includes: The orthogonal component of the stationary current is synchronized to the coordinates of the rotating voltage component based on the grid angle to obtain the rotating current component; The first regulating voltage component is obtained by proportional integration of the rotating current component; The second regulated voltage component is obtained by varying the voltage of the rotating current component. The first regulating voltage component and the second regulating voltage component are superimposed to obtain the orthogonal regulating voltage component; The primary control unit acquires the resonant frequency and generates the first switching signal based on the orthogonal component of the adjustment voltage, the resonant frequency, and the rotating voltage component.

[0022] As described above, by performing proportional integration on the rotating current component and voltage change respectively, the first and second regulating voltage components are obtained, and then superimposed to obtain the regulating voltage quadrature component, which can accurately describe the change of the current output voltage. Then, by obtaining the resonant frequency, the first switching signal is obtained by combining the regulating voltage quadrature component, the resonant frequency, and the rotating voltage component, thereby realizing precise control of the primary-side switching unit.

[0023] In one embodiment of this application, the step of proportionally integrating the rotating current component to obtain the first regulated voltage component includes: The primary control unit acquires a reference current component; calculates the current deviation between the reference current component and the rotating current component, and performs proportional-integral processing on the current deviation to obtain the first regulating voltage component.

[0024] As described above, by obtaining the reference current component and calculating the current deviation between the reference current component and the rotating current component, the change in the current output can be obtained. Then, the first regulating voltage component is generated based on the current deviation, making the obtained first regulating voltage component more accurate.

[0025] In one embodiment of this application, obtaining a second regulated voltage component by voltage variation of the rotating current component includes: The primary control unit acquires the grid angular velocity and the load inductance value; The second regulating voltage component is obtained by varying the voltage of the rotating current component based on the grid angular velocity and inductance value.

[0026] As described above, by obtaining the grid angular velocity and the load inductance, i.e., by changing the voltage of the rotating current component based on the characteristics of the device hardware, a precise second regulating voltage component can be obtained.

[0027] In one embodiment of this application, the secondary-side control unit generates a second switching signal based on the load electrical signal, comprising: The secondary control unit acquires the quadrature component of the regulating voltage and the grid angle, and calculates the phase angle based on the quadrature component of the regulating voltage; the grid angle and the phase angle are superimposed and processed by a sine function to obtain a modulation wave; the modulation wave is input to the positive terminal of the comparator to obtain the second switching signal.

[0028] As described above, after calculating the phase angle by adjusting the voltage quadrature component, the grid angle and the phase angle are superimposed and then processed by a sine function to obtain the modulation wave. The modulation wave is then input to the positive terminal of the comparator to obtain a precise second switching signal.

[0029] In one embodiment of this application, the primary-side control unit generates a third switching signal based on the acquired load electrical signal and the current sampling value acquired by the first acquisition terminal, including: The primary control unit obtains the voltage sample value and voltage reference value based on the load electrical signal; The third switching signal is obtained based on the voltage sample value, the voltage reference value, and the current sample value.

[0030] As described above, by obtaining the current output voltage sample value and voltage reference value from the load electrical signal, as well as the current sample value of the primary side, the third switching signal is obtained based on the current state of the primary side and the current state of the output, making the output third switching signal more in line with the current requirements.

[0031] In one embodiment of this application, obtaining the third switching signal based on the voltage sample value, the voltage reference value, and the current sample value includes: The primary-side control unit performs proportional-integral conversion on the deviation between the voltage sample value and the voltage reference value to obtain the current reference value; Calculate the current deviation between the current reference value and the current sample value, and perform proportional-integral conversion on the current deviation to obtain the generated modulation voltage; The modulation voltage is converted into a switching frequency by a voltage-controlled oscillator within the primary-side control unit. The third switching signal is generated by the switching frequency through the PWM module in the primary control unit.

[0032] As described above, the current reference value is obtained by calculating the deviation between the voltage sample value and the voltage reference value and performing proportional-integral conversion, thereby converting the voltage at the load end into current. Then, the current deviation between the current reference value and the realized current sample value is calculated and performed proportional-integral conversion to generate the modulation voltage, thereby realizing the conversion from current to modulation signal. Finally, the signal is processed by a voltage-controlled oscillator and a PWM module to output a precise third switching signal.

[0033] In one embodiment of this application, the secondary-side control unit acquires the primary-side signal and generates a fourth switching signal based on the primary-side signal, including: The secondary control unit acquires the primary current signal, inputs the primary current signal into the positive terminal of the comparator, and then the comparator outputs the fourth switching signal.

[0034] As described above, the secondary control unit collects the primary current signal and generates a fourth switching signal to control the secondary switching unit. That is, the secondary control unit obtains the current output state of the primary side and controls the secondary switching unit on the load side, thereby achieving coordination between the primary and secondary sides.

[0035] One embodiment of the present invention is as follows: Please refer to Figure 1 as well as Figure 2 A converter adaptable to DC and AC grid energy conversion includes a primary-side control unit 1, a primary-side switching unit 2, a secondary-side control unit 3, a secondary-side switching unit 4, and a transformer 5; the secondary side of the transformer 5 is provided with taps; the converter as a whole is based on an LLC resonant topology, and the primary-side switching unit 2 includes MOSFETs. -MOS transistor The full-bridge structure consists of secondary-side switching unit 4, which includes MOSFETs. -MOS transistor Combined with a tap structure, a "back-to-back" MOSFET bridge arm structure is formed. The topology achieves DC / AC or DC / DC energy conversion by changing the control method of the primary and secondary side switches. The specific connection method is as follows: The power input terminal of the primary side switch unit 2 is used to connect the power supply ( Figure 2 The output of the primary-side switching unit 2 (DC on the left) is connected to the first acquisition terminal (inductor L) of the primary-side control unit 1. m Keep away from capacitor C r One end) and the primary side connection of transformer 5; the control input terminal of primary side switching unit 2 (MOS transistor S1-MOS transistor) The gate of the primary-side control unit 1 is connected to the first output terminal of the primary-side control unit 1; the input terminal of the secondary-side switching unit 4 is connected to the secondary side of the transformer 5, and the output terminal of the secondary-side switching unit 4 and the tap of the transformer 5 are respectively used to connect to the two ends of the load to form a circuit; the second acquisition terminal of the primary-side control unit 1 is used to connect to the load ( Figure 2 The DC input terminal on the right side of the secondary switch unit 4 is connected to the data output terminal of the primary control unit 1 or the primary side of the transformer 5 (inductor L). m Close to capacitor C r (One end) is selected for connection.

[0036] This embodiment provides a control method for a converter adapted to DC and AC grid energy conversion, applied to the aforementioned converter adapted to DC and AC grid energy conversion. The method includes: The system acquires an output status command. If the output status command is AC output, the control input terminal of the secondary-side switching unit 4 is connected to the data output terminal of the primary-side control unit 1. The primary-side control unit 1 generates a first switching signal based on the acquired load electrical signal and sends the first switching signal to the primary-side switching unit 2. The secondary-side control unit 3 generates a second switching signal based on the load electrical signal and sends the second switching signal to the secondary-side switching unit 4. If the output status command is DC output, the control input terminal of the secondary-side switching unit 4 is connected to the primary side of the transformer 5. The primary-side control unit 1 generates a third switching signal based on the acquired load electrical signal and sends the third switching signal to the primary-side switching unit 2. The secondary-side control unit 3 acquires the primary-side signal, generates a fourth switching signal based on the primary-side signal, and sends the fourth switching signal to the secondary-side switching unit 4. The specific control principle is as follows: (1) When the output is AC, the primary side generates a high-frequency AC current with a low-frequency envelope through differential frequency control. At this time, the secondary side bridge arm, as the core part of the single-stage inverter, realizes synchronous rectification and polarity switching through precise switching control.

[0037] like Figure 3 As shown, this implements the control switch if the primary current direction is detected to be positive during the positive half-wave of the output current. Conductive, with switch The body diode forms a forward current path, keeping the load current in the positive direction; if a negative primary current is detected, the control switch is activated. Conductive, with switch The body diode forms a circuit, maintaining the load current in the positive direction. During the negative half-wave of the output current, if the primary current direction is detected to be positive, the control switch is activated. Conductive, with switch The body diode works in conjunction with the circuit to establish a reverse path, causing the load current to turn negative; if the primary current direction is detected to be negative, the control switch is activated. Conductive, with switch The body diode completes the circuit, ensuring that the load current is in the negative direction. Through this segmented control mechanism, the system dynamically adjusts the switching state according to the direction of the primary current and the output half-cycle requirements, and finally obtains a smooth and stable AC output after processing by the filter circuit; at the same time, this operating mode makes the switching loss extremely low and supports bidirectional flow of electrical energy.

[0038] Please refer to Figure 4 The primary control unit 1 generates a first switching signal based on the load electrical signal, including: This system employs a current control strategy based on a single-phase DQ coordinate system and introduces orthogonal signal generation technology to obtain the grid current in... Virtual orthogonal components in the axis; output current of the microinverter ( Synchronization with the grid voltage is achieved through a phase-locked loop (PLL) unit. Details are as follows: Primary control unit 1 acquires the current signal from the load electrical signal ( ), By introducing OSG technology, a current signal is generated that is equal to the original single-phase current signal but 90 degrees out of phase. The original signal is considered as the α-axis component, and the signal that lags by 90 degrees is considered as the β-axis component, i.e., the orthogonal components of the quiescent current. ; ; At the same time, the current signal ( Synchronization with the grid voltage is achieved through a PLL unit, thereby accurately extracting the grid frequency from the PLL unit. From the perspective of the power grid and the d-axis component of the grid voltage and q-axis components (Orthogonal components of rotating voltage); Obtain the current in the two-phase stationary coordinate system (α-β). and Then, the grid angle is input into the Park transform. The orthogonal components of the stationary current are synchronized to the coordinate system (dq axis) of the rotating voltage component to ensure that the dq coordinate system rotates synchronously with the fundamental positive sequence component of the grid voltage; thus, the rotating current component is obtained. and : ; The first regulating voltage component is obtained by proportional integration of the rotating current component, and the primary-side control unit 1 obtains the reference current component. and ( and (These are the d-axis and q-axis components of the output current reference value, respectively). In this embodiment... and These are preset current reference values, corresponding to the d-axis and q-axis components of the output current in the rotating coordinate system, respectively; for example, if the required active current amplitude to be output to the grid is 10A, then set... =10A, =0A; Calculate the current deviation between the reference current component and the rotating current component, and perform proportional-integral (PI) processing on the current deviation to obtain the first regulating voltage component. The second regulating voltage component is obtained by varying the voltage of the rotating current component, and the primary control unit 1 acquires the grid angular velocity. ( (This refers to the angular velocity corresponding to the grid frequency) and the inductance of the load. ( (It is the output filter inductor). The second regulating voltage component is obtained by changing the voltage of the rotating current component according to the grid angular velocity and the inductance value. The first regulating voltage component and the second regulating voltage component are superimposed to obtain the quadrature regulating voltage component. and ;like Figure 4 As shown in (a).

[0039] Primary control unit 1 obtains the resonant frequency The first switching signal is generated based on the quadrature component of the regulating voltage, the resonant frequency, and the rotating voltage component. ;like Figure 4 As shown in (b), and Each component is multiplied and then superimposed, followed by processing with the square root module. The deviation is calculated, and then passed through the proportional module (gain K) and compared with... The deviation is calculated, and the final output is the high-frequency switching frequency. Ultimately, through high-frequency switching frequency and grid frequency A high-frequency sine wave with a low-frequency envelope is generated by differential frequency modulation of the primary-side switching unit 2: ; ; For ease of calculation, let By superimposing these two signals and using the trigonometric function sum-to-product formula, we can obtain: ; Therefore, the frequency of the high-frequency sine wave is After filtering out high-frequency components with a low-pass filter, the frequency can be obtained. Low-frequency signals; if and Controlled by the modulated signal, it can also achieve the effects of frequency modulation and phase modulation; the principle of difference frequency modulation is applied in converters, that is, the two frequencies differ in phase. The high-frequency square wave drive signals are applied to the two primary arms of the bridge, respectively. After these two signals act on the LLC resonant cavity, they excite two waves with the same amplitude but different frequencies in the resonant circuit. The sinusoidal resonant current makes Its synthesized current is exactly a high-frequency sine wave with a sinusoidal envelope of twice the power frequency. Through the synchronous demodulation of the push-pull full-bridge expander and the action of the filter, the power frequency AC voltage is output.

[0040] At the same time, Figure 4 In the PI controller shown in (a) Select the PI sensor based on the actual output current collected. and This makes the open-loop object poles Zero point of compensator To cancel each other out, we get: ; Where i(t) is the output signal of the PI controller. It is the integral coefficient. It is the proportionality coefficient.

[0041] Please refer to Figure 4 (c) The secondary control unit 3 generates a second switching signal based on the load electrical signal, including: the secondary control unit 3 acquires the quadrature component of the regulating voltage and the grid angle, and calculates the phase angle based on the quadrature component of the regulating voltage. : ; The modulated wave is obtained by superimposing the grid angle and the phase angle and then processing it with a sine function; the modulated wave is input to the positive terminal of the comparator to obtain the second switching signal. - ).

[0042] High frequency switching frequency Directly applied to the LLC resonant circuit, the voltage gain of the resonant cavity can be changed by adjusting this frequency, and the switching frequency can be adjusted accordingly. Changing the impedance of the resonant network affects the voltage gain. The gain characteristics of the LLC converter depend on the switching frequency. With resonant frequency The ratio of the switching frequency to the resonant frequency; when the switching frequency is less than the resonant frequency, the resonant cavity impedance (circuit) is inductive, the gain M is greater than 1, and it operates in boost mode; when the switching frequency equals the resonant frequency, the resonant cavity impedance is resistive, and the gain M equals 1; when the switching frequency is greater than the resonant frequency, the resonant cavity impedance is capacitive, the gain M is less than 1, and it operates in buck mode. Through feedback regulation by the PI controller, the switching frequency is automatically adjusted to control the voltage (when the output voltage is too low, the frequency is reduced to increase the gain; when it is too high, the frequency is increased to decrease the gain), thereby achieving control of the output current amplitude. Finally, the calculated phase angle is... From the perspective of the power grid The signals are superimposed and input into a sine function to generate a modulation wave. This modulation wave is then passed through a comparator to generate a drive signal for the secondary-side switch, thereby completing the closed-loop control of the entire power conversion process.

[0043] Among them, the above-mentioned PLL unit extracts the power grid frequency. From the perspective of the power grid and the d-axis component of the grid voltage and q-axis components The method is as follows: The phase-locked loop first transforms the grid voltage in the three-phase stationary coordinate system (abc) into components in the two-phase stationary coordinate system (αβ). The transformation matrix is: ; The voltage components in the two-phase stationary coordinate system (αβ) are then transformed into components in the two-phase rotating coordinate system (dq). This transformation requires the phase angle estimated by the PLL itself, and the transformation matrix is ​​as follows: ; Transform to estimate angle Rotated dq coordinate system: ; like Phase error If it is very small, then: ; therefore Proportional to the phase error, it serves as the PLL loop control signal. When the PLL achieves precise phase locking, the q-axis voltage component... The voltage is zero, while the d-axis voltage component is zero. This reflects the amplitude information of the grid voltage. The PLL then outputs the estimated instantaneous grid angular frequency after phase detection and PI control, and the estimated grid voltage phase angle is obtained by integration. and grid frequency Park transform output This refers to the D-axis component of the grid voltage.

[0044] like Figure 3 As shown, based on the above control method, this system can achieve four-quadrant operation. The system incorporates the ability to actively adjust the phase relationship between output voltage and current. During the positive half-cycle of the grid voltage, it can not only output a forward current in phase with the voltage (positive active power), but also output a current lagging or leading the voltage through phase shift control (reactive power compensation), and even output a current out of phase with the voltage (energy feedback to the DC side). During the negative half-cycle of the voltage, current control in the corresponding quadrant can also be achieved. By adjusting the phase shift angle and frequency difference relationship between the bridge arms, the system can achieve current flow in any direction under any output voltage polarity, thus covering any combination of active and reactive power, and fully supporting four-quadrant operation modes including rectification, inversion, capacitive reactive power, and inductive reactive power.

[0045] (2) When the output is DC, the system controls the secondary bridge arm to work in rectification mode.

[0046] Please refer to Figure 5 When the direction of the primary current is detected to be positive, the control switch is activated. and The circuit is turned on, ensuring the current flowing into the load remains in the positive direction. When a negative primary current is detected, the control switch is activated. and The conduction process also ensures that the current flowing into the load is positive. This achieves consistency in current direction, and after smoothing by the filter circuit, a stable DC output is obtained. At this point, the back-to-back MOSFET bridge arms transform the entire secondary-side rectifier circuit into a controllable DC port. The center tap becomes the negative terminal of the DC output, and the midpoints of the two bridge arms are connected in parallel to become the positive terminal of the DC output. A high-frequency gate drive signal synchronized with the primary-side frequency is used, and the MOSFETs in the same bridge arm use the same signal. By precisely controlling the timing of the secondary-side switches, conditions can be created for the primary-side switches to achieve zero-voltage turn-on (ZVS), which can greatly reduce switching losses. Especially in high-frequency applications, this can significantly improve overall efficiency and allow for the use of higher switching frequencies to reduce the size of magnetic components.

[0047] Please refer to Figure 6 The primary-side control unit 1 generates a third switching signal based on the acquired load electrical signal and the current sampling value acquired by the first acquisition terminal, including: the primary-side control unit 1 obtains the voltage sampling value based on the load electrical signal. (DC bus voltage sample value) and voltage reference value ; and acquire the current sampling value collected by the first acquisition terminal. Primary control unit 1 samples voltage values. With voltage reference value The deviation is then converted using a proportional-integral (PI) converter to obtain the current reference value. ; Calculate the reference value of the current Current deviation from current sampling value The modulation voltage is obtained by performing a proportional-integral (PI) conversion on the current deviation. The modulation voltage is converted into a switching frequency by the voltage-controlled oscillator (VCO) within the primary-side control unit 1. The switching frequency is controlled by the PWM module within the primary-side control unit 1. Generate a third switch signal ( For example, using chips such as NCP1399 and L6599, etc., LLC controllers contain a similar internal structure: the output of the error amplifier is connected to the input of the VCO, the output of the VCO is used as the clock of the PWM generator, and the PWM generator finally generates two complementary switching signals ( The output DC voltage is stabilized by adjusting the switching frequency to change the gain of the LLC resonant network.

[0048] Among them, the VCO is the core device for modern frequency modulation, and its output frequency is directly determined by the input control voltage, as shown in the following formula: ; in, It is the center frequency, and K is the sensitivity of the VCO, which indicates "how much the frequency can be changed per volt". It is the control voltage, which is the modulation signal.

[0049] Secondary side control unit 3 acquires primary side signals After the primary current signal is input to the positive terminal of the comparator, the comparator outputs the fourth switching signal. That is, the system is based on The real-time direction and magnitude of the MOSFET dynamically control the switch. The switching mechanism enables the diode to turn on and off, providing a low-impedance path for the output current at appropriate times. This replaces traditional diode rectification, reducing conduction losses and improving overall efficiency. Ultimately, through a switching strategy that synchronizes with the primary current in real time, efficient and controllable rectification operation is achieved on the secondary side.

[0050] In actual control processes, when the output is AC, differential frequency modulation can generate a high-frequency square wave with an automatically changing duty cycle over time. When the output is DC, VCO modulation can generate a high-frequency square wave with a constant duty cycle of 0.5. This square wave is applied to an LLC resonant network. The LLC network utilizes the resonance principle to enable the primary-side switch to conduct under ZVS conditions, essentially eliminating conduction losses and achieving high-efficiency energy transfer. Simultaneously, the gain characteristics of the LLC network allow for voltage regulation by adjusting the switching frequency, and the magnetized inductor provides a wider soft-switching range for photovoltaic applications with a wide input voltage range. Furthermore, high-frequency operation can significantly reduce the size of the transformer and filter, resulting in higher power density for the entire device.

[0051] In summary, this invention provides a converter and its control method adapted to energy conversion between DC and AC power grids. This allows the converter to be used in both DC and single-phase AC power grids using the same circuit structure, requiring only adjustments to the control strategy. Only one product needs to be designed and manufactured, offering flexibility, fewer components, simplified protection devices and system wiring, significantly reducing overall R&D and maintenance costs, and improving the reliability and integration of the entire system. Simultaneously, the system supports bidirectional energy flow, and the center-tapped transformer provides electrical isolation, ensuring high system safety and effectively suppressing noise and matching different voltage levels.

[0052] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent modifications made based on the content of the present invention specification and drawings, or direct or indirect applications in related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A converter adapted to DC and AC power grid energy conversion, characterized in that, The transformer includes a primary-side control unit, a primary-side switching unit, a secondary-side control unit, a secondary-side switching unit, and a transformer; the secondary side of the transformer is provided with taps. The power input terminal of the primary-side switching unit is used to connect to the power supply, and the output terminal of the primary-side switching unit is connected to the first acquisition terminal of the primary-side control unit and the primary side of the transformer, respectively; the control input terminal of the primary-side switching unit is connected to the first output terminal of the primary-side control unit. The input terminal of the secondary-side switching unit is connected to the secondary side of the transformer, and the output terminal of the secondary-side switching unit and the taps of the transformer are respectively used to connect to the two ends of the load to form a circuit. The second acquisition terminal of the primary-side control unit is used to connect to the load and acquire the load electrical signal; The control input terminal of the secondary-side switching unit is connected to the data output terminal of the primary-side control unit or the primary-side gate of the transformer.

2. A control method for a converter adaptable to DC and AC power grid energy conversion, characterized in that, The method, applied to a converter adaptable to DC and AC grid energy conversion as described in claim 1, comprises: Command to obtain output status; If the output status command is AC output, the control input terminal of the secondary-side switch unit is connected to the data output terminal of the primary-side control unit; the primary-side control unit generates a first switch signal based on the acquired load electrical signal and sends the first switch signal to the primary-side switch unit; and the secondary-side control unit generates a second switch signal based on the load electrical signal and sends the second switch signal to the secondary-side switch unit. If the output status command is a DC output, the control input terminal of the secondary-side switching unit is connected to the primary side of the transformer; the primary-side control unit generates a third switching signal based on the acquired load electrical signal and the current sampling value acquired by the first acquisition terminal, and sends the third switching signal to the primary-side switching unit; the secondary-side control unit acquires the primary-side signal, generates a fourth switching signal based on the primary-side signal, and sends the fourth switching signal to the secondary-side switching unit.

3. The control method for a converter adaptable to DC and AC power grid energy conversion according to claim 2, characterized in that, The primary-side control unit generates a first switching signal based on the load electrical signal, including: The primary control unit acquires the current signal in the load electrical signal, performs orthogonal signal processing on the current signal to obtain the static current orthogonal component corresponding to the current signal; and acquires the grid angle, grid frequency and rotating voltage orthogonal component in the load electrical signal according to the phase-locked loop. The first switching signal is generated based on the orthogonal component of the quiescent current, the grid angle, the grid frequency, and the voltage component.

4. The control method for a converter adaptable to DC and AC power grid energy conversion according to claim 3, characterized in that, The step of generating the first switching signal based on the orthogonal component of the quiescent current, the grid angle, the grid frequency, and the rotating voltage component includes: The orthogonal component of the stationary current is synchronized to the coordinates of the rotating voltage component based on the grid angle to obtain the rotating current component; The first regulating voltage component is obtained by proportional integration of the rotating current component; The second regulated voltage component is obtained by varying the voltage of the rotating current component. The first regulating voltage component and the second regulating voltage component are superimposed to obtain the orthogonal regulating voltage component; The primary control unit acquires the resonant frequency and generates the first switching signal based on the orthogonal component of the adjustment voltage, the resonant frequency, and the rotating voltage component.

5. The control method for a converter adaptable to DC and AC power grid energy conversion according to claim 4, characterized in that, The step of proportionally integrating the rotating current component to obtain the first regulating voltage component includes: The primary control unit acquires a reference current component; calculates the current deviation between the reference current component and the rotating current component, and performs proportional-integral processing on the current deviation to obtain the first regulating voltage component.

6. The control method for a converter adaptable to DC and AC power grid energy conversion according to claim 4, characterized in that, The step of changing the voltage of the rotating current component to obtain the second regulated voltage component includes: The primary control unit acquires the grid angular velocity and the load inductance value; The second regulating voltage component is obtained by varying the voltage of the rotating current component based on the grid angular velocity and inductance value.

7. The control method for a converter adaptable to DC and AC power grid energy conversion according to claim 2, characterized in that, The secondary control unit generates a second switching signal based on the load electrical signal, including: The secondary control unit acquires the quadrature component of the regulating voltage and the grid angle, and calculates the phase angle based on the quadrature component of the regulating voltage; the grid angle and the phase angle are superimposed and processed by a sine function to obtain a modulation wave; the modulation wave is input to the positive terminal of the comparator to obtain the second switching signal.

8. The control method for a converter adaptable to DC and AC power grid energy conversion according to claim 2, characterized in that, The primary-side control unit generates a third switching signal based on the acquired load electrical signal and the current sampling value acquired by the first acquisition terminal, including: The primary control unit obtains the voltage sample value and voltage reference value based on the load electrical signal; The third switching signal is obtained based on the voltage sample value, the voltage reference value, and the current sample value.

9. The control method for a converter adaptable to DC and AC power grid energy conversion according to claim 8, characterized in that, The process of obtaining the third switching signal based on the voltage sample value, the voltage reference value, and the current sample value includes: The primary-side control unit performs proportional-integral conversion on the deviation between the voltage sample value and the voltage reference value to obtain the current reference value; Calculate the current deviation between the current reference value and the current sample value, and perform proportional-integral conversion on the current deviation to obtain the generated modulation voltage; The modulation voltage is converted into a switching frequency by a voltage-controlled oscillator within the primary-side control unit. The third switching signal is generated by the switching frequency through the PWM module in the primary control unit.

10. The control method for a converter adaptable to DC and AC power grid energy conversion according to claim 2, characterized in that, The secondary-side control unit acquires the primary-side signal and generates a fourth switching signal based on the primary-side signal, including: The secondary control unit acquires the primary current signal, inputs the primary current signal into the positive terminal of the comparator, and then the comparator outputs the fourth switching signal.

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