A four-switch circuit with bipolarity based on partial power conversion

Abstract

The present invention discloses a bipolar four-switch circuit based on partial power conversion, and relates to the technical field of power electronics application. The four-switch circuit includes a first half-bridge circuit, a second half-bridge circuit, an inductor, a port capacitor, a capacitor and a relay; the two ends of the inductor are respectively connected to the midpoint of the bridge arm of the first half-bridge circuit and the midpoint of the bridge arm of the second half-bridge circuit; the bridge arm of the first half-bridge circuit is connected in parallel with the port capacitor, and the bridge arm of the first half-bridge circuit is used to connect an energy storage battery, and the bridge arm of the second half-bridge circuit is connected to the capacitor through a relay, and the relay is used to switch the polarity of the voltage on the capacitor; the two ends of the capacitor are also respectively used to connect the positive pole of the DC bus and the positive pole of a preset battery, and the negative pole of the preset battery is connected to the negative pole of the DC bus. The present invention enables the power of the power converter to flow in both directions, and can realize the mutual conversion between the positive polarity voltage and the bipolar voltage, and can widen the voltage range of the power converter.

Description

Technical Field

[0001] The invention relates to the technical field of power electronic applications, and in particular to a four-switch circuit with bipolarity based on partial power conversion. Background Art

[0002] The research background of the four-switch circuit is as follows:

[0003] 1) New energy development needs: Developing low-carbon, clean, and renewable new energy has become a key measure. Four-switch converters have attracted attention due to their wide application in new energy power generation and energy storage units.

[0004] 2) Microgrid structure optimization: In order to improve the reliability and energy conversion efficiency of distributed generation units, the microgrid structure has developed rapidly, and the four-switch converter plays an important role in it.

[0005] 3) Wide voltage conversion range: The four-switch Buck-Boost converter has many advantages such as wide voltage conversion range, same input and output polarity, and bidirectional power transmission, which makes it attract much attention in DC microgrids.

[0006] 4) Control strategy research: There are various control strategies for four-switch converters, including single-mode control, dual-mode control and triple-mode control. The research on these control strategies helps to improve the efficiency and stability of the converter.

[0007] 5) Efficiency optimization goal: The two main optimization goals of the four-switch Buck-Boost converter are to achieve smooth mode switching and optimal conversion efficiency. The research on mode switching optimization control and efficiency optimization control helps to achieve the goals of high efficiency, high power density and high reliability of the converter.

[0008] 6) Soft switching control research: In order to obtain higher efficiency and frequency, the soft switching control of the four-switch Buck-Boost converter is studied. By directly reducing the switching frequency or using soft switching to reduce switching losses, the efficiency optimization is achieved to adapt to applications with increasingly higher power density and efficiency indicators. Multi-mode control strategy: Multi-mode control is simple to implement and has high energy transmission efficiency.

[0009] For systems with variable output demands, the traditional approach is to treat the required output as a whole. All transmitted energy flows through the power converter and is adjusted according to the real-time demand of the load. It is converted by switching devices and electrical isolation devices, including voltage and current processing, and then supplied to the load. This process of processing all transmitted power is called full-power conversion, and the converter built based on this idea is called a full-power converter. Partial power processing is a concept proposed relative to full-power processing. The idea of ​​partial power processing is to divide the output, transmit a part of it at a constant value, without passing through the conversion device, and flow directly to the load only under the influence of the port parameters. The rest of the non-constant part is converted and dynamically adjusted through the control quantity to meet the load demand. Since there is only a part of the quantity that changes with the output, this processing method is called partial power processing, and the converter built for partial power processing is a partial power converter.

[0010] The four-switch circuit can be generally considered as a power converter, but the current four-switch circuit cannot realize the bidirectional flow of power, and cannot realize the mutual conversion between positive polarity voltage and bipolar voltage, and cannot widen the voltage range of the power converter, limiting the scope of application of the power converter. Summary of the invention

[0011] The technical problem to be solved by the present invention is to address the deficiencies of the prior art and specifically provide the following technical solutions, which are as follows:

[0012] 1) In the first aspect, the present invention provides a four-switch circuit with bipolarity based on partial power conversion, and the specific technical solution is as follows:

[0013] It includes a first half-bridge circuit, a second half-bridge circuit, an inductor, a terminal capacitor, a capacitor and a relay;

[0014] Two ends of the inductor are respectively connected to the midpoint of the bridge arm of the first half-bridge circuit and the midpoint of the bridge arm of the second half-bridge circuit;

[0015] The bridge arm of the first half-bridge circuit is connected in parallel with the port capacitor, and the bridge arm of the first half-bridge circuit is used to connect the energy storage battery, and the bridge arm of the second half-bridge circuit is connected to the capacitor through a relay, and the relay is used to switch the polarity of the voltage on the capacitor;

[0016] The two ends of the capacitor are also used to connect the positive electrode of the DC bus and the positive electrode of the preset battery respectively, and the negative electrode of the preset battery is connected to the negative electrode of the DC bus.

[0017] The beneficial effects of a four-switch circuit with bipolarity based on partial power conversion provided by the present invention are as follows:

[0018] By switching the polarity of the voltage on the capacitor through the relay, the four-switch circuit exhibits bipolar characteristics, realizing the mutual conversion between positive polarity voltage and bipolar voltage, doubling the voltage variation range of the capacitor, broadening the voltage variation range of the power converter, and partially converting the power of the preset battery through the capacitor, which can make full use of the power of the preset battery and enable the power of the power converter to flow bidirectionally.

[0019] On the basis of the above scheme, the four-switch circuit with bipolarity based on partial power conversion of the present invention can also be improved as follows.

[0020] Further, the relay is a double-pole double-throw type relay;

[0021] The first half-bridge circuit includes: a first power tube and a second power tube;

[0022] The second half-bridge circuit includes: a third power tube and a fourth power tube;

[0023] The positive electrode of the energy storage battery is connected to the drain electrode of the first power tube and the positive electrode of the terminal capacitor;

[0024] The negative electrode of the energy storage battery is connected to the source electrode of the second power tube, the source electrode of the fourth power tube, the negative electrode of the terminal capacitor and the 4 contacts of the relay;

[0025] One end of the inductor is connected to the source of the first power tube and the drain of the second power tube, and the other end of the inductor is connected to the source of the third power tube and the drain of the fourth power tube;

[0026] The drain of the third power tube is connected to contact 1 of the relay;

[0027] The source of the fourth power tube is connected to the 4th contact of the relay;

[0028] The 2nd and 6th contacts of the relay are both connected to one end of the capacitor and the positive pole of the DC bus; the 3rd and 5th contacts of the relay are both connected to the other end of the capacitor and the positive pole of the preset battery.

[0029] Furthermore, a relay control circuit is included, and the relay control circuit is used to control the polarity of the voltage on the relay switching capacitor.

[0030] Further, the relay control circuit includes: a diode and a transistor;

[0031] One end of the relay coil and the cathode of the diode are used to apply the working voltage of the relay, the other end of the relay coil is connected to the anode of the diode and the collector of the transistor, the emitter of the transistor is grounded, and the base of the transistor is used to apply a control signal to control the on and off of the transistor.

[0032] Furthermore, the relay control circuit also includes: a first resistor, the base of the transistor is connected to one end of the first resistor, and the other end of the first resistor is used to apply a control signal for controlling the transistor to be turned on or off.

[0033] Furthermore, the relay control circuit also includes a second resistor, and two ends of the second resistor are respectively connected to the base of the transistor and the emitter of the transistor.

[0034] Furthermore, the transistor is of NPN type. When the control signal applied to the transistor is at a high level, the transistor is saturated and turned on, the coil of the relay is energized, and the voltage on the capacitor is a negative polarity voltage;

[0035] When the control signal applied to the transistor is at a low level, the transistor is cut off, the coil of the relay is de-energized, and the voltage on the capacitor is a positive polarity voltage.

[0036] Furthermore, the voltage gain is controlled by controlling the duty cycle of the driving waveforms of the first half-bridge circuit and the second half-bridge circuit and the phase shift angle between the first half-bridge circuit and the second half-bridge circuit.

[0037] 2) In a second aspect, the present invention further provides an electrical device with a power conversion function, comprising any of the above-mentioned four-switch circuits with bipolarity based on partial power conversion.

[0038] 3) In a third aspect, the present invention further provides a power grid system, comprising any of the above-mentioned four-switch circuits with bipolarity based on partial power conversion.

[0039] It should be noted that the beneficial effects achieved by the technical solutions of the second to third aspects of the present invention and the corresponding possible implementation methods can be found in the above-mentioned technical effects of the first aspect and its corresponding possible implementation methods, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments of the present invention:

[0041] Figure 1 Schematic diagram of a structure of a four-switch circuit with bipolarity based on partial power conversion according to an embodiment of the present invention;

[0042] Figure 2 A schematic diagram of a closed-loop control scheme of a four-switch circuit with bipolarity based on partial power conversion according to an embodiment of the present invention;

[0043] Figure 3 The main waveform scheme of a four-switch circuit with bipolarity based on partial power conversion according to an embodiment of the present invention is a schematic diagram;

[0044] Figure 4 A schematic diagram of a bipolar control scheme of a four-switch circuit with bipolarity based on partial power conversion according to an embodiment of the present invention;

[0045] Figure 5 One of the schematic diagrams of a transient analysis process of a four-switch circuit with bipolarity based on partial power conversion according to an embodiment of the present invention;

[0046] Figure 6 The second schematic diagram of the transient analysis process of a four-switch circuit with bipolarity based on partial power conversion according to an embodiment of the present invention;

[0047] Figure 7 The third schematic diagram of the transient analysis process of a four-switch circuit with bipolarity based on partial power conversion according to an embodiment of the present invention;

[0048] Figure 8 The fourth schematic diagram of the transient analysis process of a four-switch circuit with bipolarity based on partial power conversion according to an embodiment of the present invention;

[0049] Fig. 9 FIG5 is a fifth schematic diagram of a transient analysis process of a four-switch circuit with bipolarity based on partial power conversion according to an embodiment of the present invention;

[0050] Fig.10 Schematic diagram No. 6 of a transient analysis process of a four-switch circuit with bipolarity based on partial power conversion according to an embodiment of the present invention;

[0051] Fig.11 FIG7 is a schematic diagram of a transient analysis process of a four-switch circuit with bipolarity based on partial power conversion according to an embodiment of the present invention;

[0052] Fig.12 This is an eighth schematic diagram of a transient analysis process of a four-switch circuit with bipolarity based on partial power conversion according to an embodiment of the present invention. DETAILED DESCRIPTION

[0053] The principles and features of the present invention are described below. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0054] The technical solution of the present invention and how the technical solution of the present invention solves the above-mentioned technical problems are described in detail below with specific embodiments. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of the present invention will be described below in conjunction with the accompanying drawings.

[0055] like Figure 1As shown, a four-switch circuit with bipolarity based on partial power conversion according to an embodiment of the present invention includes a first half-bridge circuit, a second half-bridge circuit, an inductor L, a port capacitor C1, a capacitor C2 and a relay K;

[0056] Two ends of the inductor L are respectively connected to the midpoint of the bridge arm of the first half-bridge circuit and the midpoint of the bridge arm of the second half-bridge circuit;

[0057] The bridge arm of the first half-bridge circuit is connected in parallel with the port capacitor C1, and the bridge arm of the first half-bridge circuit is used to connect the energy storage battery, and the bridge arm of the second half-bridge circuit is connected to the capacitor through the relay K, and the relay K is used to switch the polarity of the voltage on the capacitor C2;

[0058] Among them, the output voltage of the energy storage battery can be 48V, and can also be set according to actual conditions.

[0059] The two ends of the capacitor C2 are also used to connect the positive electrode of the DC bus and the positive electrode of the preset battery respectively, and the negative electrode of the preset battery is connected to the negative electrode of the DC bus.

[0060] Optionally, in the above technical solution, the relay K is a double-pole double-throw type relay;

[0061] The first half-bridge circuit includes: a first power tube S1 and a second power tube S2;

[0062] The second half-bridge circuit includes: a third power tube S3 and a fourth power tube S4;

[0063] The positive electrode of the energy storage battery is connected to the drain of the first power tube S1 and the positive electrode of the terminal capacitor C1;

[0064] The negative electrode of the energy storage battery is connected to the source electrode of the second power tube S2, the source electrode of the fourth power tube S4, the negative electrode of the terminal capacitor C1 and the 4 contacts of the relay K;

[0065] One end of the inductor L is connected to the source of the first power tube S1 and the drain of the second power tube S2, and the other end of the inductor L is connected to the source of the third power tube S3 and the drain of the fourth power tube S4;

[0066] The drain of the third power tube S3 is connected to the contact 1 of the relay K;

[0067] The source of the fourth power tube S4 is connected to the 4th contact of the relay K;

[0068] Contacts 2 and 6 of relay K are both connected to one end of capacitor C2 and the positive electrode of the DC bus; contacts 3 and 5 of relay K are both connected to the other end of capacitor C2 and the positive electrode of the preset battery.

[0069] Among them, the DC bus is a 220V DC bus.

[0070] Optionally, in the above technical solution, a relay control circuit is further included, and the relay control circuit is used to control the polarity of the voltage on the relay switching capacitor C2.

[0071] Optionally, in the above technical solution, the relay control circuit includes: a diode D and a transistor Q;

[0072] One end of the coil of relay K and the cathode of diode D are used to apply the working voltage of relay K. The other end of the coil of relay K is connected to the anode of diode D and the collector of transistor Q. The emitter of transistor Q is grounded. The base of transistor Q is used to apply a control signal to control the on and off of transistor Q. That is to say, the relay control circuit realizes the closing or opening of the relay by controlling the on and off of transistor Q. Figure 1 In, V cc Represents the voltage required for relay K to work, that is, the working voltage of relay K, V b Indicates the control signal that controls the on and off of transistor Q.

[0073] Optionally, in the above technical solution, the relay control circuit further includes: a first resistor R1, the base of the transistor Q is connected to one end of the first resistor R1, and the other end of the first resistor R1 is used to apply a control signal to control the transistor Q to turn on or off.

[0074] Optionally, in the above technical solution, the relay control circuit further includes a second resistor R2, and two ends of the second resistor R2 are respectively connected to the base of the transistor Q and the emitter of the transistor Q.

[0075] Optionally, the preset battery can be a fuel cell or a photovoltaic cell. The four-switch circuit and the preset battery constitute a partial power structure. The power of the preset battery is adjusted by changing the voltage on capacitor C2. When the preset battery is a fuel cell, it can absorb power and emit power; when the preset battery is a photovoltaic cell, it only emits power.

[0076] Optionally, in the above technical solution, the transistor Q is of NPN type. When the control signal applied to the transistor Q is at a high level, the transistor Q is saturated and turned on, the coil of the relay K is energized, and the voltage on the capacitor C2 is a negative polarity voltage; when the control signal applied to the transistor Q is at a low level, the transistor Q is cut off, the coil of the relay K is de-energized, and the voltage on the capacitor C2 is a positive polarity voltage. Specifically:

[0077] When V b When the input is high level, transistor Q is saturated and turned on, the coil of relay K is energized, and the contacts are closed; when V bWhen the input is low level, transistor Q is turned off, the coil of relay K is powered off, and the contact is disconnected; the first resistor R1 mainly plays a current limiting role, which can reduce the power consumption of transistor Q; the second resistor R2 enables transistor Q to maintain a stable working state under different temperatures or power supply voltage changes, thereby avoiding the operating point drift caused by factors such as temperature fluctuations, and the diode D reverses the current, which can provide a release path for the coil of relay K when transistor Q turns from on to off, and clamp the voltage on the coil of relay K at V cc superior.

[0078] That is to say, the transistor Q is turned on and off by high and low levels, so that the relay K is actuated to change the polarity of the voltage on the capacitor C2. Specifically:

[0079] When a positive output is required, a low level is input to cut off the transistor Q, the relay K does not operate, and the voltage on the output capacitor C2 is a positive voltage; when a negative output is required, a high level is input to saturate and conduct the transistor Q, the relay K operates, and the voltage on the capacitor C2 is a negative voltage.

[0080] Optionally, in the above technical solution, the voltage gain is controlled by controlling the duty cycle of the driving waveforms of the first half-bridge circuit and the second half-bridge circuit and the phase shift angle between the first half-bridge circuit and the second half-bridge circuit.

[0081] When the power converter with the four-switch circuit of the present invention works in bidirectional operation, each power tube is controlled by a variable duty cycle and a phase shift angle, and the voltage gain is controlled by controlling the duty cycle of the two half-bridge driving waveforms and the phase shift angle between the two half-bridges; in order to achieve soft switching, a certain dead zone is designed, and the soft switching range is controlled by controlling the size of the dead zone.

[0082] According to the specific parameters of the power converter and the characteristics of the switching elements, a fixed dead zone is pre-set, and the size of the dead zone is dynamically adjusted by real-time monitoring of the circuit's working status and load changes.

[0083] The present invention is described by the following embodiment. A four-switch circuit with bipolarity based on partial power conversion in the embodiment includes a first half-bridge circuit, a second half-bridge circuit, an inductor, a port capacitor, a capacitor and a relay;

[0084] The first half-bridge circuit includes: a first power tube S1 and a second power tube S2;

[0085] The second half-bridge circuit includes: a third power tube S3 and a fourth power tube S4;

[0086] One end of the inductor is connected to the source of the first power tube S1 of the first half-bridge circuit and the drain of the second power tube S2 of the first half-bridge circuit; the other end is connected to the source of the third power tube S3 of the second half-bridge circuit and the drain of the fourth power tube S4 of the second half-bridge circuit;

[0087] The bridge arm of the first half-bridge circuit is connected in parallel with the port capacitor C1, and the drain of the first power tube S1 of the first half-bridge circuit is used to connect the positive electrode of the energy storage battery and the positive electrode of the port capacitor C1, the source of the second power tube S2 of the first half-bridge circuit is used to connect the negative electrode of the energy storage battery, the negative electrode of the port capacitor C1, the source of the fourth power tube S4 of the second half-bridge circuit and the 4th contact of the relay K, the source of the first power tube S1 of the first half-bridge circuit and the drain of the second power tube S2 of the first half-bridge circuit; the drain of the third power tube S3 of the second half-bridge circuit is used to connect the 1st contact of the relay, the source of the third power tube S3 of the second half-bridge circuit and the drain of the fourth power tube S4 of the second half-bridge circuit;

[0088] Among them, the output voltage of the energy storage battery can be 48V, and can also be set according to actual conditions, and the DC bus is a 220V DC bus; V1 represents the voltage of the energy storage battery, and V2 represents the voltage after conversion by the four-switch circuit but not after relay level conversion.

[0089] Optionally, in the above technical solution, the relay is a double-pole double-throw type relay;

[0090] Contacts 2 and 6 of relay K are connected to one end of capacitor C2 and the positive pole of the DC bus; contacts 3 and 5 of relay K are connected to the other end of capacitor C2 and the positive pole of the preset battery. When the relay is not in operation, the double poles of the relay are placed between contacts 2 and 5, so that contacts 1 are connected to contacts 2, contacts 4 are connected to contacts 5, and the voltage polarity of the port capacitor C1 is positive at the top and negative at the bottom. When the relay is in operation, the double poles of the relay are placed between contacts 3 and 6, so that contacts 1 are connected to contacts 3, contacts 4 are connected to contacts 6, and the voltage polarity of the port capacitor C1 is negative at the top and positive at the bottom.

[0091] One end of the port capacitor C1 is connected to the 2nd and 6th contacts of the relay and the positive pole of the DC bus 220V; the other end of the port capacitor C1 is connected to the 3rd and 5th contacts of the relay and the positive pole of the preset battery; the negative pole of the preset battery and the negative pole of the DC bus 220V.

[0092] Optionally, in the above technical solution, a relay control circuit is further included, and the relay control circuit is used to control the polarity of the voltage on the relay switching capacitor C2.

[0093] Optionally, in the above technical solution, the relay control circuit includes: a diode D and a transistor Q;

[0094] One end of the coil of relay K and the cathode of diode D are used to apply the working voltage of relay K. The other end of the coil of relay K is connected to the anode of diode D and the collector of transistor Q. The emitter of transistor Q is grounded. The base of transistor Q is used to apply a control signal to control the on and off of transistor Q. That is to say, the relay control circuit realizes the closing or opening of the relay by controlling the on and off of transistor Q. Figure 1 In, V cc Represents the voltage required for relay K to work, that is, the working voltage of relay K, V b Indicates the control signal that controls the on and off of transistor Q.

[0095] Optionally, in the above technical solution, the relay control circuit further includes: a first resistor R1, the base of the transistor Q is connected to one end of the first resistor R1, and the other end of the first resistor R1 is used to apply a control signal to control the transistor Q to turn on or off.

[0096] Optionally, in the above technical solution, the relay control circuit further includes a second resistor R2, and two ends of the second resistor R2 are respectively connected to the base of the transistor Q and the emitter of the transistor Q.

[0097] Optionally, in the above technical solution, the transistor Q is of NPN type. When the control signal V applied to the transistor Q b When the control signal V applied to transistor Q is high, transistor Q is saturated and turned on, the coil of relay K is energized, and the voltage on capacitor C2 is negative. b When it is low level, transistor Q is cut off, the coil of relay K is de-energized, and the voltage on capacitor C2 is positive polarity voltage. Specifically:

[0098] When V b When the input is high level, transistor Q is saturated and turned on, the coil of relay K is energized, and the contacts are closed; when V b When the input is low level, transistor Q is turned off, the coil of relay K is powered off, and the contact is disconnected; the first resistor R1 mainly plays a current limiting role, which can reduce the power consumption of transistor Q; the second resistor R2 enables transistor Q to maintain a stable working state under different temperatures or power supply voltage changes, thereby avoiding the operating point drift caused by factors such as temperature fluctuations, and the diode D reverses the current, which can provide a release path for the coil of relay K when transistor Q turns from on to off, and clamp the voltage on the coil of relay K at V cc superior.

[0099] That is to say, the transistor Q is turned on and off by high and low levels, so that the relay K is actuated to change the polarity of the voltage on the capacitor C2. Specifically:

[0100] When the port capacitor C1 is required to output positive polarity (i.e. positive at the top and negative at the bottom), V b The voltage signal is at a low level, which turns off the transistor Q, and the relay K does not work. The voltage on the output capacitor C2 is a positive polarity voltage. When the port capacitor C1 is required to output a negative polarity (i.e., negative on the top and positive on the bottom), V b The voltage signal is at a high level, which makes the transistor Q saturated and turned on, the relay K is activated, and the voltage on the capacitor C2 is a negative polarity voltage.

[0101] Optionally, in the above technical solution, the voltage gain is controlled by controlling the duty cycle of the driving waveforms of the first power tube S1 of the first half bridge, the first power tube S2, the third power tube S3 of the second half bridge, and the fourth power tube S4, and the phase shift angle between the first power tube S1 of the first half bridge and the fourth power tube S4 of the second half bridge.

[0102] Optionally, the preset battery can be a fuel cell or a photovoltaic cell. The four-switch circuit and the preset battery constitute a partial power structure. The power of the preset battery is adjusted by changing the voltage on capacitor C2. When the preset battery is a fuel cell, it can absorb power and emit power; when the preset battery is a photovoltaic cell, it only emits power.

[0103] When the power converter with the four-switch circuit of the present invention works in bidirectional operation, each power tube is controlled by a variable duty cycle and a phase shift angle, and the voltage gain is controlled by controlling the duty cycle of the two half-bridge driving waveforms and the phase shift angle between the two half-bridges; in order to achieve soft switching, a certain dead zone is designed, and the soft switching range is controlled by controlling the size of the dead zone.

[0104] According to the specific parameters of the power converter and the characteristics of the switching elements, a fixed dead zone is pre-set, and the size of the dead zone is dynamically adjusted by real-time monitoring of the circuit's working status and load changes.

[0105] like Figure 2 As shown, the voltage sampling and current sampling of the preset battery can be understood as sampling the voltage on the capacitor C2 to obtain the voltage U on the capacitor C2. C2 The reference voltage value U of capacitor C2 ref The voltage difference ε v , and use the PI controller to obtain the required duty cycle D2 through the mode switching strategy, the voltage U of the port capacitor C1 C1 is the voltage on the energy storage battery, and the reference voltage value U of the terminal capacitor C1 is ref , current value i C2 and the voltage U of the energy storage battery C1 Substituting into the optimal duty cycle scheme of the four switches, the phase shift angle D is calculated. φAnd duty cycle D1; D1 is the duty cycle of the first power tube S1 drive signal, 1-D1 is the duty cycle of the second power tube S2 drive signal, D2 is the duty cycle of the third power tube S3 drive signal, 1-D2 is the duty cycle of the fourth power tube S4 drive signal, D φ is the phase shift duty ratio between the first power tube S1 and the third power tube S3. The driving voltage obtained by the driving circuit controls the on and off of the corresponding power tube, where: U S1 The voltage controls the on and off of the power tube S1; U S2 The voltage controls the on and off of the power tube S2; U S3 The voltage controls the on and off of the power tube S3; U S4 The voltage controls the on and off of the power tube S4.

[0106] like Figure 3 As shown, waveforms u1, u2, u3 and u4 are control signals of the first power tube S1, the second power tube S2, the third power tube S3 and the fourth power tube S4 respectively, wherein waveform u1 leads the phase angle D compared to waveform u3 φ T p ;u ds1 、u ds2 、u ds3 、u ds4 is the drain-source voltage of the first power tube S1, the second power tube S2, the third power tube S3 and the fourth power tube S4; u L is the voltage on the inductor L; i L is the current on the inductor in the four-switch circuit; T p The time required for one switching cycle.

[0107] like Figure 4 As shown, the voltage and current of the preset battery are sampled. When the product power P of the sampled voltage U and current I is greater than the reference power P ref When V b is low level, transistor Q works in cut-off mode, relay K does not work, and the voltage on capacitor C2 is positive polarity voltage; when the product power P of the sampled voltage U and current I is less than the reference power P ref When V b is high level, transistor Q works in saturation conduction mode, relay K is activated, and the voltage on capacitor C2 is negative polarity voltage.

[0108] according to Figure 3 The waveform shown is used to perform transient analysis on a four-switch circuit with bipolarity based on partial power conversion of the present invention, and the results are as follows:

[0109] 1) Between t0 and t1, such as Figure 5As shown, the current direction on the inductor L is from right to left, and the current is freewheeling through the diode of the fourth power tube S4 to charge the parasitic capacitance of the first power tube S1 and the parasitic capacitance of the second power tube S2, and the current does not pass through the third power tube S3;

[0110] 2) Between t1 and t2, such as Figure 6 As shown, the direction of the current on the inductor L is from left to right, the first power tube S1 and the fourth power tube S4 are turned on, and the current does not pass through the second power tube S2 and the third power tube S3;

[0111] 3) Between t2 and t3, such as Figure 7 As shown, the current direction on the inductor L is from left to right, the first power tube S1 is turned on, and the parasitic capacitance of the third power tube S3 and the parasitic capacitance of the fourth power tube S4 are charged, and the current does not pass through the second power tube S2; Figure 8 As shown, the current direction on the inductor L is from left to right, the first power tube S1 is turned on, the current flows through the parasitic diode of the third power tube S3, and the current does not flow through the second power tube S2 and the fourth power tube S4;

[0112] 4) Between t3 and t4, such as Fig. 9 As shown, the direction of the current on the inductor L is from left to right, the parasitic capacitance of the first power tube S1 and the parasitic capacitance of the second power tube S2 are discharged, the current is continued through the parasitic diode of the third power tube S3, and the current does not pass through the fourth power tube S4; Fig.10 As shown, the direction of the current on the inductor is from left to right, the current is freewheeling through the parasitic diodes of the second power tube S2 and the third power tube S3, and the current does not pass through the first power tube S1 and the fourth power tube S4;

[0113] 5) At t4-t p Between, such as Fig.11 As shown, the current direction on the inductor L is from right to left, the second power tube S2 is turned on, the parasitic capacitance of the third power tube S3 and the parasitic capacitance of the fourth power tube S4 are discharged, and the current does not pass through the first power tube S1; Fig.12 As shown, the current direction on the inductor L is from right to left, the second power tube S2 is turned on, the current flows through the diode of the fourth power tube S4, and the current does not pass through the first power tube S1 and the third power tube S3.

[0114] The beneficial effects of the present invention are as follows:

[0115] The bipolar four-switch circuit based on partial power conversion of the present invention realizes bidirectional energy transmission, realizes the bipolar characteristics of capacitor voltage through a double-pole double-throw relay, broadens the voltage variation range, and is suitable for occasions requiring bipolar voltage distribution and a wide voltage range. The voltage gain is controlled by controlling the duty cycle of the driving waveforms of the two half-bridge circuits and the phase shift angle between the two half-bridge circuits. In order to realize soft switching, a certain dead zone is designed, and the soft switching range is controlled by controlling the size of the dead zone. The power conversion of the capacitor C2 and the photovoltaic cell or fuel cell components can fully utilize the power of the photovoltaic cell or fuel cell.

[0116] An electrical device with a power conversion function according to an embodiment of the present invention comprises any one of the above-mentioned four-switch circuits with bipolarity based on partial power conversion.

[0117] A power grid system according to an embodiment of the present invention comprises any one of the above-mentioned four-switch circuits with bipolarity based on partial power conversion. The power grid system may specifically be a microgrid system and may be configured according to actual conditions.

[0118] The above description is only a preferred embodiment of the present invention and an explanation of the technical principles used. Those skilled in the art should understand that the disclosure scope involved in the present invention is not limited to the technical solution formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the above disclosed concept. For example, the above features are replaced with the technical features with similar functions disclosed in the present invention (but not limited to) by each other.

[0119] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects and represent the definition of a specific order or sequence. The order of use of similar objects can be interchanged where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than the order shown or described.

[0120] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A four-switch circuit with bipolarity based on partial power conversion, characterized in that: It includes a first half-bridge circuit, a second half-bridge circuit, an inductor, a terminal capacitor, a capacitor and a relay; Two ends of the inductor are respectively connected to the midpoint of the bridge arm of the first half-bridge circuit and the midpoint of the bridge arm of the second half-bridge circuit; The bridge arm of the first half-bridge circuit is connected in parallel with the port capacitor, and the bridge arm of the first half-bridge circuit is used to connect the energy storage battery, and the bridge arm of the second half-bridge circuit is connected to the capacitor through the relay, and the relay is used to switch the polarity of the voltage on the capacitor; The two ends of the capacitor are also used to connect the positive electrode of the DC bus and the positive electrode of the preset battery respectively, and the negative electrode of the preset battery is connected to the negative electrode of the DC bus.

2. A four-switch circuit with bipolarity based on partial power conversion according to claim 1, characterized in that: The relay is a double-pole double-throw type relay; The first half-bridge circuit includes: a first power tube and a second power tube; The second half-bridge circuit includes: a third power tube and a fourth power tube; The positive electrode of the energy storage battery is connected to the drain of the first power tube and the positive electrode of the port capacitor; The negative electrode of the energy storage battery is connected to the source electrode of the second power tube, the source electrode of the fourth power tube, the negative electrode of the port capacitor and the four contacts of the relay; One end of the inductor is connected to the source of the first power tube and the drain of the second power tube, and the other end of the inductor is connected to the source of the third power tube and the drain of the fourth power tube; The drain of the third power tube is connected to the contact 1 of the relay; The source of the fourth power tube is connected to the 4th contact of the relay; Contacts 2 and 6 of the relay are both connected to one end of the capacitor and the positive pole of the DC bus; contacts 3 and 5 of the relay are both connected to the other end of the capacitor and the positive pole of the preset battery.

3. A four-switch circuit with bipolarity based on partial power conversion according to claim 2, characterized in that: It also includes a relay control circuit, and the relay control circuit is used to control the relay to switch the polarity of the voltage on the capacitor.

4. A four-switch circuit with bipolarity based on partial power conversion according to claim 3, characterized in that: The relay control circuit comprises: a diode and a transistor; One end of the coil of the relay and the cathode of the diode are used to apply the working voltage of the relay, the other end of the coil of the relay is connected to the anode of the diode and the collector of the transistor, the emitter of the transistor is grounded, and the base of the transistor is used to apply a control signal to control the on and off of the transistor.

5. A four-switch circuit with bipolarity based on partial power conversion according to claim 4, characterized in that: The relay control circuit further includes: a first resistor, the base of the transistor is connected to one end of the first resistor, and the other end of the first resistor is used to apply a control signal for controlling the on and off of the transistor.

6. A four-switch circuit with bipolarity based on partial power conversion according to claim 4, characterized in that: The relay control circuit further includes a second resistor, and two ends of the second resistor are respectively connected to the base of the transistor and the emitter of the transistor.

7. A four-switch circuit with bipolarity based on partial power conversion according to claim 4, characterized in that: The transistor is of NPN type. When the control signal applied to the transistor is at a high level, the transistor is saturated and turned on, the coil of the relay is energized, and the voltage on the capacitor is a negative polarity voltage; When the control signal applied to the transistor is at a low level, the transistor is turned off, the coil of the relay is de-energized, and the voltage on the capacitor is a positive polarity voltage.

8. A four-switch circuit with bipolarity based on partial power conversion according to any one of claims 1 to 7, characterized in that: The voltage gain is controlled by controlling the duty ratio of the driving waveforms of the first half-bridge circuit and the second half-bridge circuit and the phase shift angle between the first half-bridge circuit and the second half-bridge circuit.

9. An electrical device with power conversion function, characterized in that: A four-switch circuit with bipolarity based on partial power conversion as described in any one of claims 1 to 8.

10. A power grid system, characterized in that: A four-switch circuit with bipolarity based on partial power conversion as described in any one of claims 1 to 8.

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