Variable frequency load power supply system based on optical storage direct flexible mode

Abstract

The utility model discloses a variable-frequency load power supply system based on an optical storage direct-flexible mode. The variable-frequency load power supply system comprises a large power grid, a variable-frequency load unit, a photovoltaic power generation unit, a voltage sag treatment unit and an alternating-current load A powered by the variable-frequency load unit, wherein three-phase alternating current output by a large power grid is connected to the frequency conversion load unit and the voltage sag treatment unit through an alternating current bus; direct current output by the photovoltaic power generation unit is connected to the variable frequency load unit through a first direct current bus; the voltage sag treatment unit comprises an energy storage module, three-phase alternating current output to the voltage sag treatment unit by a large power grid is converted into direct current and then stored in the energy storage module, and output current of the energy storage module is boosted and then connected to the frequency conversion load unit through a first direct current bus. The power supply system can solve the problem of non-planned shutdown of equipment caused by voltage sag, and meanwhile, photovoltaic power generation is connected to supply power to a variable-frequency load, so that the power supply energy structure is optimized, and the purposes of energy conservation and emission reduction are achieved.

Description

Technical Field

[0001] The utility model relates to the technical field of power supply, in particular to a variable frequency load power supply system based on a photovoltaic storage direct-flexible mode. Background Art

[0002] In order to respond to the new energy development policy of energy conservation and emission reduction, power stations should not only focus on the efficiency and stability of power production in terms of operation and management, but also pay special attention to its environmental impact and carbon emissions. Power stations need to actively introduce clean energy and renewable energy technologies to reduce carbon emissions in the power generation process. The photovoltaic storage direct flexible distribution system combines four technologies: photovoltaic, energy storage, DC distribution and flexible power consumption. It is an innovative system based on the DC distribution network, which is of great significance to the zero-carbon transformation of the power industry.

[0003] At the same time, with the improvement of the automation level of power stations, variable frequency loads have been widely used. Variable frequency loads are mainly responsible for power conversion and power distribution. Specifically, they adjust the voltage and frequency of the output power supply by opening and closing its internal semiconductor devices, thereby ensuring that the most appropriate voltage can be provided according to the real-time needs of the load motor to achieve the purpose of energy saving and speed regulation. Therefore, variable frequency loads have high requirements for power quality. In the existing technology, variable frequency loads are directly powered by large power grids. If a voltage drop fault occurs in the power supply circuit, the variable frequency load will activate the low voltage protection mechanism to protect the equipment from damage, but it also causes the problem of unplanned equipment shutdown.

[0004] Therefore, there is a need for a power supply system that meets the requirements of low carbon emissions and can solve the problem of unplanned equipment downtime caused by voltage sag. Utility Model Content

[0005] Purpose of the utility model: The purpose of the utility model is to provide a variable frequency load power supply system based on the photovoltaic storage direct-flexible mode, which can optimize the power supply energy structure, reduce carbon emissions, and has the function of controlling voltage sags.

[0006] Technical solution: To achieve the above-mentioned purpose, the utility model discloses a variable frequency load power supply system based on a photovoltaic storage direct-flexible mode, comprising a large power grid, a variable frequency load unit, a photovoltaic power generation unit, a voltage sag control unit, and an AC load A powered by the variable frequency load unit; wherein, the three-phase AC power output by the large power grid is respectively connected to the variable frequency load unit and the voltage sag control unit through an AC bus; the DC power output by the photovoltaic power generation unit is connected to the variable frequency load unit through a first DC bus; the voltage sag control unit comprises an energy storage module, and the three-phase AC power output by the large power grid to the voltage sag control unit is converted into DC power and stored in the energy storage module, and the output current of the energy storage module is connected to the variable frequency load unit through the first DC bus after being boosted.

[0007] The system further includes a UPS and an important AC load B powered by the UPS, wherein the UPS is powered by a large power grid and an energy storage module.

[0008] Wherein, the UPS is an isolated online uninterruptible power supply.

[0009] The energy storage module uses a supercapacitor as a battery. When a voltage drop or short interruption occurs in the large power grid, the supercapacitor battery starts, and the UPS inverts the DC power output by the supercapacitor into AC power to enable the important AC load B to work normally.

[0010] The variable frequency load unit includes a second DC bus, an AC / DC rectifier converter A and a DC / AC inverter connected at both ends of the second DC bus. The three-phase AC power output from the large power grid to the variable frequency load unit is converted into DC power by the AC / DC rectifier converter A and then connected to the DC / AC inverter through the second DC bus and converted into AC power again, thereby supplying power to the AC load A.

[0011] The photovoltaic power generation unit comprises a photovoltaic power generation component and a photovoltaic boost DC / DC converter A connected to the current output end of the photovoltaic power generation component. The output end of the photovoltaic boost DC / DC converter A is connected to a first DC bus. After the output voltage of the photovoltaic power generation component is boosted and converted by the photovoltaic boost DC / DC converter A, it is connected to the second DC bus on the variable frequency load unit through the first DC bus.

[0012] Among them, the voltage sag management unit includes a boost DC / DC converter B, the input end of the boost DC / DC converter B is connected to the energy storage module, and the output end is connected to the first DC bus. The DC power of the energy storage module is connected to the first DC bus after being boosted by the boost DC / DC converter B; the first DC bus is connected to the second DC bus.

[0013] Among them, the boost DC / DC converter B is a parallel interleaved Boost boost circuit structure, and the output end of the circuit is a diode that is turned on by the voltage difference. When the voltage of the second DC bus drops to the voltage difference setting value, the diode is turned on, so that the energy storage module supplies power to the second DC bus of the variable frequency load unit.

[0014] Among them, the voltage sag management unit includes an AC / DC rectifier converter B, the input end of the AC / DC rectifier converter B is connected to the large power grid, and the output end is connected to the energy storage module. The three-phase alternating current output from the large power grid to the voltage sag management unit is converted into direct current by the AC / DC rectifier converter B and then stored in the energy storage module.

[0015] Beneficial effects: The utility model has the following advantages:

[0016] 1. In this system, the variable frequency load that drives the load is not only directly powered by the large power grid, but also connected to the photovoltaic power generation unit and the energy storage module. This can effectively prevent the problem of unplanned shutdown of the load caused by the activation of the low voltage protection mechanism of the variable frequency load when a voltage sag occurs in the power supply circuit under a single power supply mode.

[0017] 2. In this system, the variable frequency load is first powered by direct current from the photovoltaic power generation unit. This method not only reduces the current conversion link, simplifies the rectification design of the power supply branch, and improves energy efficiency, but also ensures that the system can maximize the use of photovoltaic power generation energy, thereby reducing the power supply system's dependence on fossil energy, promoting the development of the new energy industry, and achieving the goal of energy conservation and emission reduction;

[0018] 3. In this system, the energy storage module is connected to the variable frequency load through a boost DC / DC converter with a staggered parallel BOOST circuit topology. The circuit has high stability due to the characteristics of staggered inductor current and reduced ripple current. At the same time, the output end of the circuit is a diode that is turned on by a voltage difference. When the DC bus voltage in the variable frequency load drops to the set value of the diode voltage difference, the diode automatically turns on. Compared with a mechanical switch, it has a faster turn-on response, thereby reducing the delay time for the energy storage module to supply power to the variable frequency load;

[0019] 4. This system uses an isolated online uninterruptible power supply UPS to provide power protection for important loads. The UPS is powered by the large power grid and the energy storage module. Its built-in fault isolation function ensures that when there is a problem with the power quality of the large power grid, the important loads can still obtain uninterrupted power supply, effectively isolating the negative impact of grid voltage fluctuations on important loads;

[0020] 5. The energy storage module in this system uses supercapacitors as backup batteries. The batteries have fast charging speed, long service life and little pollution to the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the schematic diagram of the system structure;

[0022] Figure 2 The principle of high reliability power supply system for variable frequency load based on photovoltaic storage direct-flexible mode;

[0023] Figure 3 This is the working flow chart of the voltage sag management unit. DETAILED DESCRIPTION

[0024] The technical solution of the utility model is described in detail below in conjunction with the embodiments and drawings.

[0025] Photovoltaic storage direct current flexible technology is a new type of energy conversion and distribution technology, which integrates solar photovoltaic (photovoltaic), energy storage, DC distribution (direct) and flexible load (flexible) to improve energy efficiency and flexibility. Based on this technology, this system provides power to loads, which helps to achieve efficient use of energy, reduce the power supply system's dependence on fossil energy, and promote the development of the new energy industry. The specific structure of this system is as follows.

[0026] like Figure 1 As shown, the system includes a large power grid, a voltage sag control unit, a photovoltaic power generation unit, a variable frequency load unit, a UPS, an AC load A powered by the variable frequency load unit, and an important AC load B powered by the UPS.

[0027] The three three-phase AC power output from the large power grid is connected to the voltage sag control unit, variable frequency load unit and UPS through the AC bus.

[0028] The UPS uses an isolated online uninterruptible power supply. The UPS has a built-in transformer and can output different voltage levels to power the important AC load B as needed, including direct output of AC220V and output of AC110V through a transformer.

[0029] The photovoltaic power generation unit includes a photovoltaic power generation component and a photovoltaic boost DC / DC converter A. The output voltage of the photovoltaic power generation component is connected to the first DC bus after being boosted and converted by the photovoltaic boost DC / DC converter A, and supplies power to the second DC bus of the variable frequency load unit. The variable frequency load unit also includes an AC / DC rectifier converter A and a DC / AC inverter. The DC power on the second DC bus is converted into AC power by the DC / AC inverter to supply power to the AC load A. The DC / AC inverter is equipped with semiconductor devices for adjusting the voltage and frequency of the output power supply, thereby ensuring that the most suitable voltage can be provided according to the real-time needs of the AC load motor A, so as to achieve the purpose of energy saving and speed regulation.

[0030] The three-phase alternating current outputted from the large power grid is converted into direct current through the AC / DC rectifier converter A of the variable frequency load unit to supply power to the second direct current bus.

[0031] The voltage sag control unit includes an AC / DC rectifier converter B, a boost DC / DC converter B, and an energy storage module. The other three-phase AC power output from the large power grid is converted into DC power by the AC / DC rectifier converter B and stored in the energy storage module. The DC power of the energy storage module is boosted by the boost DC / DC converter B and then connected to the second DC bus of the variable frequency load unit through the first DC bus, thereby supplying power to the second DC bus.

[0032] At the same time, the energy storage module also supplies power to the UPS. The UPS has a built-in inverter that converts the DC power output by the energy storage module into AC power to supply power to the important AC load B.

[0033] The power supply system described in this scheme also includes a control system for controlling the operation of each unit device. When the variable frequency load unit is working normally, it is first powered by the photovoltaic power generation unit. When the photovoltaic power generation unit is insufficiently powered, it is powered by the large power grid. If the photovoltaic power generation unit is insufficiently powered and the three-phase AC voltage provided by the large power grid drops, the voltage on the second DC bus of the variable frequency load will also decrease. When the voltage drops below the set value, the energy storage module supplies power to the second DC bus of the variable frequency load through the boost DC / DC converter B to ensure that the variable frequency load is powered normally and the AC load A can work normally, thereby avoiding the load stopping due to temporary voltage drop.

[0034] In this method, supercapacitors are used as batteries for the energy storage module. When the voltage of the large power grid drops or is interrupted for a short time, the supercapacitor starts up. At the same time, the built-in inverter of the UPS converts the DC power output by the supercapacitor into AC power, thereby ensuring that the UPS can provide stable power supply to the important AC load B and enable it to work normally.

[0035] like Figure 2 As shown, it is a schematic diagram of a high-reliability power supply system for variable frequency loads based on a photovoltaic-storage-direct-flexible mode, wherein in the voltage sag management unit, the boost DC / DC converter B adopts a parallel interleaved Boost boost circuit, and its output end adopts a diode voltage difference conduction mode. When the second DC bus voltage drops to the voltage difference setting value and meets the diode conduction condition, the diode automatically turns on and the Boost boost circuit works. At this time, the voltage in the energy storage module is boosted by the boost DC / DC converter B, and then supplies power to the second DC bus of the variable frequency load through the first DC bus.

[0036] When the Boost circuit is working, the control system sends PWM waves to the S2 and S4 switches to control the switch tube to open and close. During the conduction period of S2 and S4, the inductors L1 and L2 store energy, and during the disconnection period of S2 and S4, the inductors L1 and L2 discharge. Photovoltaic boost DC / DC converter A is a unidirectional DC / DC converter. It adopts the maximum power point tracking control method to work with the Boost circuit to complete the power generation and boost of the photovoltaic power generation component, thereby supplying power to the second DC bus of the variable frequency load.

[0037] The specific work flow in the voltage sag management unit is as follows: Figure 3 As shown, the voltage sag management unit (i.e. Figure 3The control system monitors the voltage of the second DC bus of the variable frequency load in real time and feeds back the monitoring result to the control system. When the control system determines that the voltage of the second DC bus is less than the set value and meets the diode conduction condition, the step-up DC / DC converter B turns on the PWM signal to turn on the Boost circuit switch in the step-up DC / DC converter B. At this time, the diode is automatically turned on, and the voltage sag management unit is put into operation, thereby connecting with the second DC bus. After the voltage sag management unit supports the set time, the circuit switch of the step-up DC / DC converter B is disconnected, and the voltage sag management unit is on standby. If the voltage of the second DC bus is not less than the set value, the control system sends a PWM shutdown signal, the voltage sag management unit is on standby and continues to monitor the bus voltage of the variable frequency load in real time.

Claims

1. A variable frequency load power supply system based on a photovoltaic storage direct-flexible mode, characterized by: The system includes a large power grid, a variable frequency load unit, a photovoltaic power generation unit, a voltage sag control unit, and an AC load A powered by the variable frequency load unit; wherein the three-phase AC power output by the large power grid is respectively connected to the variable frequency load unit and the voltage sag control unit through an AC bus; the DC power output by the photovoltaic power generation unit is connected to the variable frequency load unit through a first DC bus; the voltage sag control unit includes an energy storage module, the three-phase AC power output by the large power grid to the voltage sag control unit is converted into DC power and then stored in the energy storage module, and the output current of the energy storage module is connected to the variable frequency load unit through the first DC bus after being boosted; The system further includes a UPS and an important AC load B powered by the UPS, wherein the UPS is powered by a large power grid and an energy storage module.

2. The variable frequency load power supply system based on the photovoltaic storage direct-flexible mode according to claim 1 is characterized in that: The UPS is an isolated online uninterruptible power supply.

3. The variable frequency load power supply system based on the photovoltaic storage direct-flexible mode according to claim 1 is characterized in that: The energy storage module uses a supercapacitor as a battery. When a voltage drop or short-term interruption occurs in the large power grid, the supercapacitor battery starts, and the UPS inverts the DC power output by the supercapacitor into AC power to enable the important AC load B to work normally.

4. The variable frequency load power supply system based on the photovoltaic storage direct-flexible mode according to claim 1 is characterized in that: The variable frequency load unit includes a second DC bus, an AC / DC rectifier converter A connected at both ends of the second DC bus, and a DC / AC inverter. The three-phase AC power output from the large power grid to the variable frequency load unit is converted into DC power by the AC / DC rectifier converter A, and then connected to the DC / AC inverter through the second DC bus and converted into AC power again, thereby supplying power to the AC load A.

5. The variable frequency load power supply system based on the photovoltaic storage direct-flexible mode according to claim 4 is characterized in that: The photovoltaic power generation unit includes a photovoltaic power generation component and a photovoltaic boost DC / DC converter A connected to the current output end of the photovoltaic power generation component. The output end of the photovoltaic boost DC / DC converter A is connected to a first DC bus. After the output voltage of the photovoltaic power generation component is boosted and converted by the photovoltaic boost DC / DC converter A, it is connected to a second DC bus on the variable frequency load unit through the first DC bus.

6. The variable frequency load power supply system based on the photovoltaic storage direct-flexible mode according to claim 4 is characterized in that: The voltage sag management unit includes a boost DC / DC converter B, the input end of the boost DC / DC converter B is connected to the energy storage module, and the output end is connected to the first DC bus. The DC power of the energy storage module is connected to the first DC bus after being boosted by the boost DC / DC converter B; the first DC bus is connected to the second DC bus.

7. The variable frequency load power supply system based on the photovoltaic storage direct-flexible mode according to claim 6 is characterized in that: The boost DC / DC converter B is a parallel interleaved Boost boost circuit structure, and the output end of the circuit is a diode that is turned on by the voltage difference. When the voltage of the second DC bus drops to the voltage difference setting value, the diode is turned on, and the energy storage module supplies power to the second DC bus of the variable frequency load unit.

8. The variable frequency load power supply system based on the photovoltaic storage direct-flexible mode according to claim 1 is characterized in that: The voltage sag management unit includes an AC / DC rectifier converter B, the input end of the AC / DC rectifier converter B is connected to the large power grid, and the output end is connected to the energy storage module. The three-phase alternating current output from the large power grid to the voltage sag management unit is converted into direct current by the AC / DC rectifier converter B and then stored in the energy storage module.

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