AC priority switch device for AC and DC dual-loop power supply of middle-low voltage system
By employing a DC battery switching circuit, an AC power isolation circuit, and an AC detection circuit in a medium- and low-voltage system, combined with a sample-and-hold circuit, the introduction of high DC voltage into the AC side is prevented, thus achieving AC power priority and solving the problem of reliable and free switching between AC and DC power supply. It has the advantages of fast switching, low cost, and small size.
Patent Information
- Application Number
- CN202521575079.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-25
- Publication Date
- 2026-08-25
- Estimated Expiration
- 2035-07-25
AI Technical Summary
Existing technologies suffer from problems such as AC-side risks, common-loop interference, power loss, and poor switching reliability due to DC priority, especially in medium and low voltage systems where reliable and free switching between AC and DC power supply is difficult to achieve.
It employs a DC battery switching circuit, an AC power isolation circuit, an AC switching circuit, and an AC detection circuit, combined with a sample-and-hold circuit. A combination of high-voltage diodes prevents DC high voltage from being introduced into the AC side and quickly controls the relay to ensure AC power supply priority.
It enables rapid switching between AC and DC dual-circuit power supply in medium and low voltage systems, and has the advantages of fast switching speed, wide voltage difference range, low cost and small size. It is suitable for energy storage converters, household appliances and industrial and commercial energy storage.
Smart Images
Figure CN224683878U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of power electronics, in particular to an alternating current priority switch device suitable for alternating current-direct current dual-loop power supply of a medium-low voltage system. BACKGROUND
[0002] The power conversion system (PCS) is the core equipment of the power storage system, responsible for bidirectional conversion of energy between the alternating current power grid and the direct current battery. The battery storage is applied to the power system, and needs reliable operation conditions. The power conversion system (PCS) as an important component of the power storage system plays a key role in shortening the construction period of the energy storage power station, ensuring the operation reliability, and considering the power grid grid connection and the electrical requirements of the direct current battery side.
[0003] The medium-low voltage system (1500V / 1000V) is widely used in industrial and commercial energy storage scenarios, and needs to be compatible with alternating current power grid power supply and direct current battery power supply, and to realize seamless switching of dual-loop. With the development of energy storage technology, the auxiliary power supply of the energy storage converter not only needs battery power supply but also needs alternating current power supply. When the energy storage converter operates, the two need to be powered simultaneously, and reliable and free switching needs to be realized to ensure stable operation of the PCS. SUMMARY
[0004] In order to solve the problems of alternating current side risk, common loop interference, power loss and poor switching reliability caused by direct current priority in the prior art, the present application provides an alternating current priority switch device suitable for alternating current-direct current dual-loop power supply of a medium-low voltage system.
[0005] Embodiments of the present application are implemented as follows:
[0006] In a first aspect, the present application provides an alternating current priority switch device suitable for alternating current-direct current dual-loop power supply of a medium-low voltage system, comprising:
[0007] A direct current battery switching circuit for switching to battery power supply when alternating current power supply fails;
[0008] An alternating current power supply isolation circuit for isolating the power grid and the auxiliary power supply through an isolation transformer;
[0009] An alternating current switching circuit for preventing high voltage on the direct current side from being introduced into the alternating current side through a rectifier bridge and a high voltage diode group;
[0010] An alternating current detection circuit for detecting alternating current rectified voltage and generating a control signal;
[0011] A sample and hold circuit for controlling the action of a relay to realize alternating current priority power supply according to the detection signal.
[0012] In a possible implementation manner, the direct current battery switching circuit comprises:
[0013] Triode Q2, whose base is connected to the output control signal S1 of the sample and hold circuit through resistor R1, and whose emitter is grounded;
[0014] Normally closed relay K1, whose control coil is connected to the collector of triode Q2, and whose normally closed contact is connected in parallel with discharge diode D3;
[0015] High-voltage diodes D1 and D2, whose anodes are connected to the normally closed contact output side of relay K1, whose cathodes are connected to the positive input of the target power supply, and whose anodes are connected to the negative input of the target power supply, and whose cathodes are connected to the negative pole of the battery.
[0016] In a possible implementation, the AC power supply isolation circuit comprises an isolation transformer T1, whose input is connected to the AC power grid, and whose output is connected to a rectifier bridge D8, for isolating the power grid from the low-voltage control loop, improving electromagnetic compatibility and insulation performance.
[0017] In a possible implementation, the AC switching circuit comprises:
[0018] The rectifier bridge D8 is connected across the bus capacitor C1, and the filtered voltage forms a stable DC bus voltage.
[0019] High-voltage diodes D4, D5, D6, and D7, wherein the anode of D4 is connected to node A1, the cathode of D4 is connected to the anode of D5, the cathode of D6 is connected to node A2, and the anode of D6 is connected to the cathode of D7, forming a bidirectional blocking structure to prevent high-voltage reverse flow from the DC side to the AC side.
[0020] In a possible implementation, the AC detection circuit comprises:
[0021] Current-limiting resistors R3-R8 and voltage stabilizing tube D9, and parallel capacitors C2 and C3, are connected across nodes A1 and A2 of the AC switching circuit.
[0022] Optocoupler U1, whose anode is connected to node A3 (the node where D9 and R8 are connected in series) through voltage dividing resistor R9, and whose cathode is grounded, is used to convert the AC voltage signal into an isolated control signal.
[0023] In a possible implementation, the sample and hold circuit comprises:
[0024] Comparator U2, whose inverting input is connected to a reference voltage obtained by voltage dividing resistors R12 and R13, and whose non-inverting input is connected to node A4, i.e., the cathode of feedback diode D10.
[0025] Triode Q1, whose base is connected to the output of comparator U2 through resistor R15, and whose emitter outputs control signal S1, is used to drive triode Q2 in the DC battery switching circuit.
[0026] In a possible implementation, the anode of the bleed diode D3 is connected to the relay K1 control coil in the same node, and the cathode is connected to a 24V auxiliary power supply, which is used to absorb the reverse electromotive force generated when the relay coil is powered off, and protect the triode Q2.
[0027] In a possible implementation, the anode of the high-voltage diode D5 is connected to the cathode of D4, and the cathode of D7 is connected to the negative electrode of the target power supply, forming an independent loop and ensuring electrical isolation between the AC side and the DC side.
[0028] In a possible implementation, the breakdown voltage of the voltage stabilizing tube D9 is set as the threshold of the AC rectified voltage. When the AC voltage is normal, D9 is turned on and generates a high-level signal through the optocoupler U1, triggering the subsequent switching action.
[0029] In a possible implementation, the output end of the comparator U2 is pulled up to a 5V power supply through a resistor R14, and a positive feedback loop is formed through a feedback diode D10, ensuring that the control signal S1 remains stable during switching.
[0030] The technical scheme provided in the application can at least achieve the following beneficial effects:
[0031] The AC priority switch device for the AC / DC dual-loop power supply of a medium / low voltage system provided in the application prevents the introduction of DC high voltage into the AC side through a high-voltage diode combination, and quickly controls the action of a relay in combination with a sample-and-hold circuit, thereby ensuring that AC power supply is prioritized. The device has the advantages of fast switching speed, wide voltage difference range, low cost, small size, and the like, and is suitable for the fields of energy storage converters, household appliances, industrial and commercial energy storage, and the like. BRIEF DESCRIPTION OF DRAWINGS
[0032] In order to more clearly illustrate the technical schemes in the embodiments of the application or the prior art, a brief introduction will be given below to the drawings needed to be used in the embodiment or prior art description. Obviously, the drawings in the following description are some embodiments of the application, and other drawings can also be obtained by those skilled in the art without creative labor.
[0033] Figure 1 is a structural schematic diagram of an AC priority switch device for the AC / DC dual-loop power supply of a medium / low voltage system according to an exemplary embodiment of the application.
[0034] REFERENCE NUMERALS:
[0035] 1, DC battery switching circuit; 2, AC power supply isolation circuit; 3, AC switching circuit; 4, AC detection circuit; 5, sample-and-hold circuit. DETAILED DESCRIPTION
[0036] In order to make the purposes, embodiments and advantages of the present application more clear, the following will combine the drawings in the exemplary embodiments of the present application to clearly and completely describe the exemplary embodiments of the present application. Obviously, the described exemplary embodiments are only a part of the embodiments of the present application, not all the embodiments of the present application. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not intended to limit the present application.
[0037] It should be noted that the brief description of the terms in the present application is only for the convenience of understanding the subsequently described embodiments, and is not intended to limit the embodiments of the present application. Unless otherwise specified, these terms should be understood according to their ordinary and general meanings.
[0038] The terms "first", "second", "third" and the like in the specification and claims of the present application and the above drawings are used to distinguish similar or similar objects or entities, and do not necessarily mean to limit the specific order or sequence, unless otherwise specified. It should be understood that the terms used in this way can be interchanged under appropriate circumstances.
[0039] The terms "include" and "have" and any variations thereof are intended to cover but not exclusive inclusion, for example, a product or device including a series of components does not necessarily limit to all the components clearly listed, but can include other components not clearly listed or inherent to these products or devices.
[0040] Before explaining the AC priority switch device for low-voltage system AC / DC dual-circuit power supply provided by the embodiments of the present application, the application scenarios and implementation environments of the embodiments of the present application are introduced.
[0041] The power conversion system (PCS) is the core equipment of the power storage system, which is responsible for bidirectional conversion of energy between AC power grid and DC battery. Battery energy storage is applied to power system, which requires reliable operating conditions. The power conversion system (PCS) as an important component of the power storage system plays a key role in shortening the construction period of energy storage power station, ensuring the reliability of operation, and considering the electrical requirements of grid connection and DC battery side.
[0042] The medium and low voltage system (1500V / 1000V) is widely used in industrial and commercial energy storage scenarios, which needs to be compatible with AC power grid power supply and DC battery power supply, and realizes seamless switching of dual-circuit. With the development of energy storage technology, the auxiliary power supply of energy storage converter not only needs battery power supply but also needs AC power supply. When the energy storage converter is running, both power supplies need to be switched reliably and freely, and the PCS needs to be stable.
[0043] Based on this, the application provides an AC priority switch device suitable for AC and DC dual-loop power supply of a medium and low voltage system, adopts an isolation transformer to enhance the insulation performance of a power grid and a low voltage control loop, prevents DC high voltage from being introduced into an AC side through a high voltage diode combination, combines a sample and hold circuit to quickly control relay action, ensures AC power supply priority, has the advantages of fast switching speed, wide voltage difference range, low cost, small size and the like, and is suitable for fields of energy storage converters, household appliances, industrial and commercial energy storage and the like.
[0044] Next, the technical solutions of the application and how the technical solutions solve the above technical problems will be described in detail through embodiments and in combination with the drawings, and each embodiment can be combined with each other, and the same or similar concepts or processes can not be described again in some embodiments. Obviously, the described embodiments are part of the embodiments of the application, not all.
[0045] Figure 1 is a structural schematic diagram of an AC priority switch device suitable for AC and DC dual-loop power supply of a medium and low voltage system according to an example embodiment of the application.
[0046] In an example embodiment, as shown in Figure 1 , an AC priority switch device suitable for AC and DC dual-loop power supply of a medium and low voltage system is provided, in this embodiment, the device includes:
[0047] DC battery switching circuit 1: used for switching to battery power supply when AC power supply fails;
[0048] AC power supply isolation circuit 2: isolates a power grid and an auxiliary power supply through an isolation transformer;
[0049] AC switching circuit 3: prevents DC side high voltage from being introduced into an AC side through a rectifier bridge and a high voltage diode combination;
[0050] AC detection circuit 4: detects an AC rectified voltage and generates a control signal;
[0051] Sample and hold circuit 5: controls relay action according to a detection signal to realize AC priority power supply.
[0052] In a possible implementation manner, the specific structures of each circuit are as follows:
[0053] I. The DC battery switching circuit 1 includes a triode Q2, the base of the triode Q2 is connected with a resistor R1, the other end of the resistor R1 is connected with an AC detection and hold circuit output control signal S1, and the emitter of the triode Q2 is connected with a low voltage reference ground.
[0054] Triode Q2 collector connects the normally closed relay K1 control coil, normally closed relay K1 control coil parallel to the discharge diode D3, diode D3 anode and normally closed relay K1 control coil triode Q2 collector common node, diode D3 cathode and coil common node connected to the auxiliary control power 24V.
[0055] Normally closed relay K1 normally closed contact output side connects the high voltage diode D1 anode, D1 cathode connects the target power input positive, target power negative connects the high voltage diode D2 anode, D2 cathode connects the negative electrode of the battery.
[0056] Two, AC power isolation circuit 2 includes isolation transformer T1, the purpose of isolation transformer is to isolate the power grid and the application of auxiliary power supply, to ensure its electromagnetic compatibility, enhance the insulation performance of the grid side and PCS low voltage control loop.
[0057] Three, AC switching circuit 3 includes rectifier bridge D8, bus capacitor C1, capacitor C1 across the AC rectifier output side node A1 A2, A1 connects the high voltage diode D4 anode, D4 cathode connects D5 anode.
[0058] Rectifier bridge D8 return side connects node A2, A2 connects the high voltage diode D6 cathode, D6 anode connects D7 cathode, D7 cathode connects the target power negative.
[0059] D4, D5, D6, D7 combination application purpose is to prevent the introduction of high voltage DC side to AC side, so that the AC side becomes an independent loop.
[0060] Four, AC detection circuit 4 includes; current limiting resistor R3, R4, R5, R6, R7, R8, voltage stabilizing tube D9, current limiting resistor detects AC rectified voltage, across the AC switching circuit node A1, A2 between C2, C3 and voltage stabilizing tube D9 in parallel, voltage stabilizing tube D9 cathode in series with R8 anode connects node A2.
[0061] Voltage stabilizing tube D9 and R8 in series form node A3, one end of the voltage dividing resistor R9 connects node A3, the other end connects U1 optocoupler diode anode, U1 optocoupler diode cathode connects node A2.
[0062] C2, C3, D9 in parallel can form a reliable voltage sampling circuit, resistor R9 can limit the current protection optocoupler U1, to prevent the damage of optocoupler U1.
[0063] Five, sample and hold circuit 5 includes comparator U2, the inverting input terminal of comparator U2 connects R12, R13, the other end of R12 is connected to 5V power supply, the other end of R13 is connected to low voltage reference ground.
[0064] The output terminal of comparator U2 and the power supply are connected across resistor R14, and R14 serves as the pull-up resistor of the comparator output.
[0065] U2 same phase input terminal connection node A4, node A4 and feedback diode D10 cathode connection, D10 anode connection comparator U1 output terminal node A5, R15 connected between node A4 and triode Q1 base, triode Q1 collector 5V power supply.
[0066] Triode Q1 base and low voltage reference ground between the connection resistance R16, emitter resistance R17 triode Q1 emitter and low voltage reference ground, triode emitter as control signal S1 output.
[0067] Working principle:
[0068] When AC side AC / DC and DC side battery Bat / DC power supply at the same time, has the function of AC priority power supply.
[0069] AC power supply:
[0070] When the DC side is not powered, the AC side is connected to the grid, the grid voltage is output to the rectifier bridge D8 through the AC isolation transformer T1, and the power supply is completed after the bus capacitor C1 filtering, and the diodes D4, D5, D6 and D7 form an output to the load.
[0071] Battery power supply:
[0072] When the AC side is not powered, the battery is powered, the battery voltage is output to the load through the normally closed contact of the normally closed relay K1 and D1 and D2.
[0073] AC grid and battery power supply:
[0074] When the AC grid and battery power supply, the AC detection circuit charges the capacitors C2 and C3 through the current limiting resistor, when the optocoupler is turned on, the level at node A3 changes from low to high, the comparator U2 output terminal level changes from low to high, and the positive feedback through D10 forms a sample and hold. After the comparator output terminal (A5) becomes high, the control triode Q1 is turned on, the triode Q1 emitter potential changes from low to high, the control triode Q2 is turned on, the normally closed relay K1 control coil is powered on, and the normally closed contact is disconnected, blocking the battery side to continue to power the load, forming the function of AC priority power supply in the AC and DC dual loop power supply.
[0075] It can be seen that some embodiments of the present application have the advantages of high efficiency and fast switching, large dual input voltage difference range, high output power, low product cost, small size, and can be applied in many fields, such as household appliances, military electronics, industrial and commercial energy storage, flywheel energy storage, building energy storage, etc. The application of the power supply system with AC and DC dual power supply is more extensive, the advantage is more obvious, and it has good reliability and economic benefit.
[0076] Any combination of the technical features in the above embodiments can be made, and for the sake of brevity, not all possible combinations are described above, however, as long as the combination of the technical features does not exist in contradiction, it shall be considered within the scope of the present disclosure.
[0077] The above embodiments only express several implementation manners of the present application, and the description is relatively specific and detailed, but it shall not be understood as a limitation on the patent scope of the present application. It shall be pointed out that, for ordinary skilled persons in the art, several modifications and improvements can be made without departing from the concept of the present application, and these shall be within the protection scope of the present application. Therefore, the patent protection scope of the present application shall be subject to the appended claims.
Claims
1. An AC priority switch device suitable for AC / DC dual-circuit power supply in medium and low voltage systems, characterized in that, include: DC battery switching circuit: used to switch to battery power when AC power fails; AC power isolation circuit: isolates the mains power supply from the auxiliary power supply through an isolation transformer; AC switching circuit: prevents high voltage from the DC side from being introduced into the AC side through a rectifier bridge and a high-voltage diode group; AC detection circuit: detects the AC rectified voltage and generates a control signal; Sample and hold circuit: Controls the relay to operate based on the detected signal to achieve AC priority power supply.
2. The AC priority switch device for AC / DC dual-circuit power supply in medium and low voltage systems as described in claim 1, characterized in that, The DC battery switching circuit includes: Transistor Q2 has its base connected to the output control signal S1 of the sample-and-hold circuit through resistor R1, and its emitter grounded. Normally closed relay K1 has its control coil connected to the collector of transistor Q2 and connected in parallel with discharge diode D3; High voltage diodes D1 and D2 are connected as follows: the anode of D1 is connected to the normally closed contact output side of relay K1, the cathode of D1 is connected to the positive terminal of the target power input, the anode of D2 is connected to the negative terminal of the target power supply, and the cathode of D2 is connected to the negative terminal of the battery.
3. The AC priority switch device for AC / DC dual-circuit power supply in medium and low voltage systems as described in claim 2, characterized in that, The AC power isolation circuit includes an isolation transformer T1, whose input end is connected to the AC power grid and whose output end is connected to the rectifier bridge D8. It is used to isolate the power grid from the low-voltage control circuit and improve electromagnetic compatibility and insulation performance.
4. The AC priority switch device for AC / DC dual-circuit power supply in medium and low voltage systems as described in claim 3, characterized in that, The AC switching circuit includes: The rectifier bridge D8 has a bus capacitor C1 connected across its output side, which filters the voltage to form a stable DC bus voltage. High-voltage diodes D4, D5, D6, and D7 are used, with the anode of D4 connected to node A1, the cathode of D4 connected to the anode of D5, the cathode of D6 connected to node A2, and the anode of D6 connected to the cathode of D7, forming a bidirectional blocking structure to prevent high voltage from the DC side from flowing back to the AC side.
5. The AC priority switch device for AC / DC dual-circuit power supply in medium and low voltage systems as described in claim 1, characterized in that, The AC detection circuit includes: The current-limiting resistors R3-R8 and the Zener diode D9, along with parallel capacitors C2 and C3, are connected across nodes A1 and A2 of the AC switching circuit. Optocoupler U1, whose anode is connected to node A3 through voltage divider resistor R9 and whose cathode is grounded, is used to convert AC voltage signals into isolated control signals.
6. The AC priority switch device for AC / DC dual-circuit power supply in medium and low voltage systems as described in claim 5, characterized in that, The sample-and-hold circuit includes: Comparator U2 obtains the reference voltage through a voltage divider between resistors R12 and R13 at its inverting input terminal, and connects to node A4, which is the cathode of feedback diode D10, at its non-inverting input terminal. Transistor Q1 has its base connected to the output of comparator U2 via resistor R15, and its emitter outputs control signal S1 to drive transistor Q2 in the DC battery switching circuit.
7. The AC priority switch device for AC / DC dual-circuit power supply in medium and low voltage systems as described in claim 2, characterized in that, The anode of the discharge diode D3 shares a common node with the control coil of the relay K1, and the cathode is connected to a 24V auxiliary power supply. It is used to absorb the reverse electromotive force generated when the relay coil is de-energized, thus protecting the transistor Q2.
8. The AC priority switch device for AC / DC dual-circuit power supply in medium and low voltage systems as described in claim 4, characterized in that, The anode of the high-voltage diode D5 is connected to the cathode of D4, and the cathode of D7 is connected to the negative terminal of the target power supply, forming an independent circuit to ensure electrical isolation between the AC side and the DC side.
9. The AC priority switch device for AC / DC dual-circuit power supply in medium and low voltage systems as described in claim 5, characterized in that, The breakdown voltage of the Zener diode D9 is set to the threshold of the AC rectified voltage. When the AC voltage is normal, D9 conducts and generates a high-level signal through the optocoupler U1, triggering subsequent switching actions.
10. The AC priority switch device for AC / DC dual-circuit power supply in medium and low voltage systems as described in claim 6, characterized in that, The output of the comparator U2 is pulled up to the 5V power supply through resistor R14, and a positive feedback loop is formed through feedback diode D10 to ensure that the control signal S1 remains stable during the switching process.