Busbar voltage balancing circuit of optical storage direct-flexible system and control method

Abstract

The invention discloses a bus voltage balancing circuit of an optical storage direct-flexible system and a control method. The balancing circuit designed by the invention can effectively improve the voltage stability of the system and reduce the influence caused by voltage fluctuation. By adopting the virtual capacitor controller and the current inner loop / PWM generator, the working mode of the bidirectional DC converter can be accurately controlled, so that efficient bidirectional flow of energy between the super capacitor and the DC bus is realized. Besides, according to the control method, different operation conditions can be flexibly coped with through a preset working mode and an applicable scene, and it is ensured that the bus voltage can be kept stable in various scenes.

Description

Technical Field

[0001] The present invention relates to the field of electrical engineering technology, and in particular to a bus voltage balancing circuit and control method for a photovoltaic storage direct-flexible system. Background Art

[0002] The photovoltaic storage direct-flexible system refers to a new energy system that combines photovoltaic power generation, energy storage system and DC distribution technology. The main components of the system include photovoltaic power generation components, energy storage batteries, low-voltage AC loads, etc. The stability of the bus voltage is crucial to the reliable operation of the photovoltaic storage direct-flexible system. However, since the output of the photovoltaic array is affected by the weather / sunshine intensity, the charging and discharging of the energy storage battery is affected by the health status / temperature and charge status, and the system load fluctuates violently, the bus voltage of the photovoltaic storage direct-flexible system usually fluctuates within a certain range. The instability of the DC bus voltage may cause equipment damage, reduced system efficiency, reduced power supply quality, and reduced energy storage battery life.

[0003] How to balance the bus voltage of the photovoltaic storage direct-flexible system is an important issue for the high-reliability and large-scale application of the photovoltaic storage direct-flexible system. In engineering, the commonly used methods include designing a new DC bus voltage stability control method. In view of the fact that the outer loop of the bus voltage is easily affected by parameter perturbations and load disturbances, a composite controller combining an extended state disturbance observer and a sliding mode controller with a new reaching law is proposed to achieve stable control of the bus voltage under load disturbances; and by coordinating the control of multiple inverters in the system, a solution is proposed to reduce the total ripple current amplitude by controlling the phase difference, reducing the bus secondary ripple voltage by 95%. Among the above methods, although the first method has good anti-interference and load disturbance suppression capabilities, it is extremely sensitive to system parameters. When there are errors in the system parameters, it will seriously affect the control effect; the second method requires the coordinated control of multiple inverters in the system, and requires compatibility and adjustment of the control strategies and control methods of multiple inverters, which is difficult to achieve in real time. Summary of the invention

[0004] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0005] In view of the above existing problems, the present invention is proposed.

[0006] Therefore, the present invention provides a bus voltage balancing circuit for a photovoltaic-storage-direct-flexible system, which can solve the problems mentioned in the background technology.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0008] In a first aspect, the present invention provides a bus voltage balancing circuit of a photovoltaic-storage-direct-flexible system, comprising: a bidirectional DC converter, a virtual capacitor controller and a current inner loop / PWM generator;

[0009] The bidirectional DC converter is an electric energy converter connecting the supercapacitor and the DC bus of the target photovoltaic storage and flexible system;

[0010] The bidirectional DC converter includes a plurality of power tubes, a plurality of resistors, a plurality of inductors, a plurality of capacitors and a plurality of current sensors.

[0011] As a preferred solution of the bus voltage balancing circuit of the photovoltaic storage direct-current flexible system described in the present invention, the current inner loop / PWM generator is used to control several power tubes in the bidirectional DC converter to perform working mode conversion.

[0012] As a preferred solution of the bus voltage balancing circuit of the photovoltaic storage direct-flexible system described in the present invention, there are several working modes, and each working mode corresponds to an applicable scenario;

[0013] The number of the working modes depends on the number of control methods of the current inner loop / PWM generator.

[0014] As a preferred solution of the bus voltage balancing circuit of the photovoltaic storage direct-flexible system described in the present invention, wherein: the left side of the bidirectional DC converter is connected to a physical supercapacitor and the right side is connected to the DC bus of the photovoltaic storage direct-flexible system, and the current inner loop / PWM generator controls several power tubes in the bidirectional DC converter to perform working mode conversion, and controls the bidirectional energy flow between the supercapacitor and the DC bus of the photovoltaic storage direct-flexible system through the working mode conversion.

[0015] As a preferred solution of the bus voltage balancing circuit of the photovoltaic storage direct-flexible system described in the present invention, wherein: the operating modes include boost mode 1, boost mode 2, buck mode 1 and buck mode 2.

[0016] As a preferred solution of the bus voltage balancing circuit of the photovoltaic storage direct-flexible system described in the present invention, the working mode also includes:

[0017] Boost mode 1 corresponds to the first applicable scenario, and at this time the supercapacitor is in a boost discharge state;

[0018] Boost mode 2 corresponds to the second applicable scenario, and at this time the DC bus of the target PV-storage DC-flexible system is in a boost charging state;

[0019] Buck mode 1 corresponds to the third applicable scenario, and at this time the supercapacitor is in a buck discharge state;

[0020] Buck mode 2 corresponds to the fourth applicable scenario, and at this time the DC bus of the target photovoltaic storage direct-flexible system is in a buck charging state.

[0021] As a preferred solution of the bus voltage balancing circuit of the photovoltaic storage direct-flexible system described in the present invention, the applicable scenarios include:

[0022] When in the first scenario, the DC bus voltage of the target PV-storage DC-flexible system is not less than the supercapacitor voltage;

[0023] When in the second scenario, the DC bus voltage of the target PV-storage DC-flexible system is less than the supercapacitor voltage;

[0024] When in the third scenario, the DC bus voltage of the target photovoltaic storage direct-flexible system is less than the supercapacitor voltage;

[0025] When in the fourth scenario, the target DC bus voltage of the photovoltaic storage direct-flexible system is not less than the supercapacitor voltage.

[0026] In a second aspect, the present invention provides a control method for a bus voltage balancing circuit of a photovoltaic storage direct-flexible system, comprising:

[0027] Establish a voltage balancing circuit based on the busbar of the target PV-storage direct-flexible system;

[0028] Several working modes and applicable scenarios are preset, the working modes include boost mode 1, boost mode 2, buck mode 1 and buck mode 2, and each working mode corresponds to an applicable scenario;

[0029] The control switches in the control voltage balancing circuit are used to switch the working mode. The control voltage balancing circuit includes four control switches. The working mode is switched through the logic operation of the control switches.

[0030] In a third aspect, the present invention provides a computer device, comprising a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the above-mentioned method when executing the computer program.

[0031] In a fourth aspect, the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program implements the steps of the method described above when executed by a processor.

[0032] Compared with the prior art, the present invention has the following beneficial effects: The present invention proposes a bus voltage balancing circuit and control method for a photovoltaic storage direct-flexible system. The balancing circuit designed in the present application can effectively improve the voltage stability of the system and reduce the impact caused by voltage fluctuations. By adopting a virtual capacitor controller and a current inner loop / PWM generator, the present application can accurately control the working mode of the bidirectional DC converter, thereby realizing efficient bidirectional energy flow between the supercapacitor and the DC bus. In addition, the control method of the present application can flexibly respond to different operating conditions through preset working modes and applicable scenarios, ensuring that the bus voltage can be kept stable in various scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0034] Figure 1 A structural diagram of a bus voltage balancing circuit and control method for a photovoltaic-storage-direct-flexible system provided by an embodiment of the present invention;

[0035] Figure 2 A schematic diagram of a photovoltaic-storage-direct-flexible system and a voltage balancing device of a photovoltaic-storage-direct-flexible system bus voltage balancing circuit and control method provided in one embodiment of the present invention;

[0036] Figure 3 A schematic diagram of boost mode 1 operation of a bus voltage balancing circuit and control method for a photovoltaic-storage-direct-flexible system provided by an embodiment of the present invention;

[0037] Figure 4 A waveform diagram of boost mode 1 of a bus voltage balancing circuit and control method of a photovoltaic storage direct-flexible system provided by an embodiment of the present invention;

[0038] Figure 5 A schematic diagram of boost mode 2 operation of a bus voltage balancing circuit and control method for a photovoltaic-storage direct-flexible system provided by an embodiment of the present invention;

[0039] Figure 6 A boost mode 2 waveform diagram of a bus voltage balancing circuit and control method of a photovoltaic storage direct-flexible system provided by an embodiment of the present invention;

[0040] Figure 7 A schematic diagram of a buck mode 1 operation of a bus voltage balancing circuit and control method for a photovoltaic-storage-direct-flexible system provided by an embodiment of the present invention;

[0041] Figure 8 A waveform diagram of buck mode 1 of a bus voltage balancing circuit and control method of a photovoltaic storage direct-flexible system provided by an embodiment of the present invention;

[0042] Fig. 9 A schematic diagram of a buck mode 2 operation of a bus voltage balancing circuit and control method for a PV-storage direct-flexible system provided by an embodiment of the present invention;

[0043] Fig.10 A voltage reduction mode 2 waveform diagram of a bus voltage balancing circuit and control method of a photovoltaic storage direct-flexible system provided by an embodiment of the present invention;

[0044] Fig.11 A solar-storage direct-current-flexible system bus voltage balancing circuit and control method provided by an embodiment of the present invention provides a law of variation of the direct current bus voltage of a solar-storage direct-current-flexible system;

[0045] Fig.12 A long-term DC bus voltage result of a bus voltage balancing circuit and control method of a photovoltaic storage DC-flexible system provided by an embodiment of the present invention;

[0046] Fig.13 A supercapacitor output / absorption current curve when the system step load changes in a bus voltage balancing circuit and control method of a photovoltaic storage direct-flexible system provided by an embodiment of the present invention;

[0047] Fig.14 An internal structural diagram of a computer device for a bus voltage balancing circuit and control method of a photovoltaic-storage-direct-flexible system provided in accordance with an embodiment of the present invention. DETAILED DESCRIPTION

[0048] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0049] Example 1

[0050] Reference Figure 1-Figure 14 , which is the first embodiment of the present invention, provides a bus voltage balancing circuit and control method for a photovoltaic-storage-direct-flexible system, including:

[0051] In the existing related technologies, there are some problems, such as insufficient system voltage stability and difficulty in maintaining the stability of the DC bus voltage under different operating conditions.

[0052] This application provides a circuit and a control method that can effectively solve the above-mentioned problems. Next, we will combine multiple embodiments to explain in detail how to implement the design of the bus voltage balancing circuit of the solar-storage direct-flexible system;

[0053] Figure 1 The structure diagram of a bus voltage balancing circuit and control method of a solar-storage direct-flexible system is shown, including:

[0054] In the embodiment of the present application, a bidirectional DC converter, a virtual capacitor controller and a current inner loop / PWM generator;

[0055] The bidirectional DC converter is an energy converter that connects the supercapacitor and the DC bus of the target photovoltaic storage and flexible system;

[0056] The bidirectional DC converter includes a plurality of power tubes, a plurality of resistors, a plurality of inductors, a plurality of capacitors and a plurality of current sensors.

[0057] In an optional embodiment, the bidirectional DC converter can be composed of multiple power tubes in parallel to improve the current carrying capacity. Each power tube is equipped with a corresponding drive circuit to ensure that it can respond to the control signal quickly and accurately. The current sensor is used to monitor the current size in the bidirectional DC converter in real time and provide necessary feedback information for the virtual capacitor controller. The virtual capacitor controller dynamically adjusts the switching state of the power tube according to the preset control strategy, combined with the real-time data of the DC bus voltage and the supercapacitor voltage, so as to control the direction and size of energy flow. The current inner loop / PWM generator is responsible for generating accurate pulse width modulation waveforms to drive the power tube to work in the best state and ensure the efficient and stable operation of the converter. Through this design, the bus voltage balancing circuit of the photovoltaic storage direct-flexible system of the present invention can adapt to different load changes, achieve rapid voltage balancing, and improve the stability and reliability of the entire system.

[0058] In an optional embodiment, the design of the bidirectional DC converter may also include a temperature sensor for monitoring the operating temperature of the converter to ensure that the power output can be automatically adjusted in a high temperature environment to avoid equipment damage caused by overheating. In addition, in order to further improve the response speed and control accuracy of the system, the current inner loop / PWM generator can use advanced digital signal processor (DSP) or field programmable gate array (FPGA) technology to achieve fast signal processing and accurate PWM waveform output. In terms of control strategy, the virtual capacitor controller can integrate artificial intelligence algorithms and continuously optimize control parameters through machine learning to adapt to various changes in the system operation process, thereby achieving a more intelligent and automated voltage balancing effect.

[0059] It should be noted that many different bidirectional DC converters can be created by using a number of power tubes, a number of resistors, a number of inductors, a number of capacitors and a number of current sensors, but the purpose is to connect the supercapacitor and the target photovoltaic storage direct-flexible system DC bus and realize electric energy conversion. Power tubes, resistors, inductors, capacitors and current sensors are the relevant components summarized in this application that the relevant technical personnel cannot escape using when designing a bidirectional DC converter for the purpose of connecting the supercapacitor and the target photovoltaic storage direct-flexible system DC bus and realizing electric energy conversion. Therefore, any type of bidirectional DC converter created by the relevant technical personnel using a number of power tubes, a number of resistors, a number of inductors, a number of capacitors and a number of current sensors for the purpose of connecting the supercapacitor and the target photovoltaic storage direct-flexible system DC bus and realizing electric energy conversion should be within the protection scope of this application.

[0060] In the embodiment of the present application, the current inner loop / PWM generator is used to control a plurality of power tubes in the bidirectional DC converter to perform operating mode conversion.

[0061] In an optional embodiment, the current inner loop / PWM generator may include a feedback control module and a PWM waveform generation module. The feedback control module is responsible for receiving instructions from the virtual capacitor controller and adjusting the output of the PWM waveform generation module according to these instructions. The PWM waveform generation module generates a corresponding pulse width modulation waveform according to the instructions of the feedback control module to control the switching state of the power tube. Through this structure, the current inner loop / PWM generator can accurately control the operation of the bidirectional DC converter to ensure the efficiency and stability of energy conversion.

[0062] In an optional embodiment, the design of the current inner loop / PWM generator can also integrate advanced control algorithms, such as proportional integral derivative (PID) control, to further improve the dynamic response performance and steady-state accuracy of the system. In practical applications, the performance of the current inner loop / PWM generator directly affects the performance of the entire photovoltaic storage direct-flexible system, so its design and optimization are crucial to achieving efficient and stable energy conversion.

[0063] In the embodiment of the present application, the following is designed: Figure 1 The balancing circuit shown in the figure, the bus voltage balancing device and control method of the photovoltaic storage direct-flexible system of the present application mainly include two parts: a bidirectional DC converter and a control method. Among them, the bidirectional DC converter is an energy converter connecting the supercapacitor and the system bus voltage, which is used to realize the bidirectional energy flow of electric energy at both ends of the converter; the control method mainly includes a virtual capacitor controller and a current inner loop / PWM generator.

[0064] In the embodiment of the present application, there are several working modes, and each working mode corresponds to an applicable scenario;

[0065] The number of operating modes depends on the number of control methods of the current inner loop / PWM generator.

[0066] In an optional embodiment, the controller of the current inner loop / PWM generator is determined according to the power tubes contained in the current inner loop / PWM generator. Several power tubes will result in different control methods. For example, when the current inner loop / PWM generator contains three power tubes, there may be several different control methods, namely, one is turned on and the others are turned off, two are turned on and the others are turned off, three are all turned on, three are all turned off, etc. The specific number is not limited in this application, and technical personnel need to obtain it according to actual needs.

[0067] In an optional embodiment, when high-efficiency energy conversion is required, the controller may select a mode in which all three power tubes are fully turned on to achieve minimum switching loss and maximum energy conversion efficiency.

[0068] In an optional embodiment, when fine adjustment is required, the controller may select a mode in which a single power tube is turned on to achieve precise control of the current.

[0069] In an optional embodiment, the current inner loop / PWM generator can also be designed to automatically switch the working mode according to the system operating status to adapt to different load and voltage conditions to ensure stable operation of the system.

[0070] In an embodiment of the present application, the left side of the bidirectional DC converter is connected to a physical supercapacitor and the right side is connected to the DC bus of the photovoltaic storage and direct-flexible system. The current inner loop / PWM generator controls several power tubes in the bidirectional DC converter to perform working mode conversion, and the bidirectional energy flow between the supercapacitor and the DC bus of the photovoltaic storage and direct-flexible system is controlled through the working mode conversion.

[0071] In an embodiment of the present application, a bidirectional DC converter is used to realize bidirectional energy flow between the two ends of the converter, and at the same time, an auxiliary circuit on the bidirectional DC converter is used to measure the system operating voltage and current.

[0072] like Figure 1 As shown in the figure, the left side of the bidirectional DC converter is connected to the physical supercapacitor SC, and the right side is connected to the DC bus BUS of the photovoltaic storage and flexible system. Let the supercapacitor voltage be V sc , the current is I sc ; DC bus voltage is V bus .

[0073] In the present embodiment, R vsns1 and R vsns2 series connection to achieve V sc The measured V sc1Access to the virtual capacitor controller.

[0074] In the present embodiment, C in As the input capacitor, an aluminum electrolytic capacitor is selected in this example to smooth the high-frequency voltage fluctuation of the supercapacitor SC.

[0075] In the present embodiment, R isns1 As a current sensor, a shunt or a Hall / fluxgate current sensor can be used. In this example, a shunt is used to measure the input / output current of the supercapacitor SC. The measured value I discharge Connect to the current inner loop / PWM generator.

[0076] In the embodiment of the present application, M1-M4 are four power tubes (four power MOSFETs in this example), which realize the bidirectional energy flow between the supercapacitor SC and the DC bus BUS of the photovoltaic storage and flexible system through switch control. Its switch signals PWM1-PWM4 are controlled by the current inner loop / PWM generator.

[0077] In the embodiment of the present application, L is an energy storage inductor, which is used to cooperate with M1-M4 to realize the storage and release of electric energy, thereby achieving step-up and step-down conversion.

[0078] In the present embodiment, C out As the output capacitor, an aluminum electrolytic capacitor is selected in this example to smooth the high-frequency voltage fluctuation of the DC bus BUS.

[0079] In the present embodiment, R vsns3 and R vsns4 series, used to achieve the V bus Measure, the measured V bus1 Access to the virtual capacitor controller.

[0080] In the present embodiment, R isns2 The current sensor can be a shunt or a Hall / fluxgate current sensor. In this example, a shunt is used to measure the input / output current of the DC bus BUS. The measured value I charge Connect to the current inner loop / PWM generator.

[0081] In the embodiment of the present application, the working modes include boost mode 1, boost mode 2, buck mode 1 and buck mode 2.

[0082] In the embodiment of the present application, the working mode also includes:

[0083] Boost mode 1 corresponds to the first applicable scenario, and at this time the supercapacitor is in a boost discharge state;

[0084] Boost mode 2 corresponds to the second applicable scenario, and at this time the DC bus of the target PV-storage DC-flexible system is in a boost charging state;

[0085] Buck mode 1 corresponds to the third applicable scenario, and at this time the supercapacitor is in a buck discharge state;

[0086] Buck mode 2 corresponds to the fourth applicable scenario, and at this time the DC bus of the target photovoltaic storage direct-flexible system is in a buck charging state.

[0087] In the embodiments of the present application, applicable scenarios include:

[0088] When in the first scenario, the DC bus voltage of the target PV-storage DC-flexible system is not less than the supercapacitor voltage;

[0089] When in the second scenario, the DC bus voltage of the target PV-storage DC-flexible system is less than the supercapacitor voltage;

[0090] When in the third scenario, the DC bus voltage of the target photovoltaic storage direct-flexible system is less than the supercapacitor voltage;

[0091] When in the fourth scenario, the target DC bus voltage of the photovoltaic storage direct-flexible system is not less than the supercapacitor voltage.

[0092] In the embodiment of the present application, the current inner loop / PWM generator is used to provide and absorb current I between the super capacitor SC and the DC bus BUS. bus Table 1 shows the four working modes and applicable scenarios of the bidirectional DC converter, as follows.

[0093] Table 1 Bidirectional DC converter operating modes and applicable scenarios

[0094]

[0095] In an optional embodiment, in boost mode 1, when the bus voltage is higher than the supercapacitor voltage and the supercapacitor is required to provide power to the bus, that is, V bus ≥V sc And I bus ≥0, at this time, MOS tube M1 remains on, M2 remains off, and MOS tubes M3 and M4 operate alternately. Figure 3 As shown, the waveform is Figure 4 shown.

[0096] When M4 is turned on, M3 is turned off. At this time, the super capacitor SC charges L through M4 to generate current i1; when M4 is turned off, M3 is turned on. At this time, the current in the inductor L discharges through the body diode of M3 to generate current i2.

[0097] Let α = t offT represents the duty cycle, where T is the switching period; t off is the M4 off time. Figure 4 Medium d is the dead time of M3 delaying on after M4 is turned off, or M4 delaying on after M3 is turned off. At this time, in steady state,

[0098]

[0099] In an optional embodiment, in boost mode 2, when the bus voltage is lower than the supercapacitor voltage and the bus needs to provide power to the supercapacitor, that is, V bus <V sc And I bus <0, at this time, MOS tube M3 remains on, M4 remains off, MOS tubes M1 and M2 operate alternately, and their conduction states are as follows: Figure 5 As shown, the waveform is Figure 6 shown.

[0100] When M2 is turned on, M1 is turned off, and the DC bus charges the inductor L to generate current i1; when M1 is turned off, the current in L is continued through the body diode of M1 to generate current i2. At this time, the current i in the inductor L is L is negative, in steady state,

[0101]

[0102] In an optional embodiment, in step-down mode 1, when the bus voltage is lower than the supercapacitor voltage and the supercapacitor is required to provide power to the bus, that is, V bus <V sc And I bus ≥0, at this time, MOS tube M3 remains on, M4 remains off, MOS tubes M1 and M2 operate alternately, and their conduction states are as follows: Figure 7 As shown, the waveform is Figure 8 shown.

[0103] When M1 is turned on, M2 is turned off, and the super capacitor SC charges the inductor L to generate current i1; when M2 is turned off, the current in L is continued through the body diode of M2 to generate current i2. At this time, in the steady state,

[0104] V bus =αV sc

[0105] In an optional embodiment, in step-down mode 2, when the bus voltage is higher than the supercapacitor voltage and the bus needs to provide power to the supercapacitor, that is, V bus ≥V sc And I bus<0, at this time, MOS tube M1 remains on, M2 remains off, and MOS tubes M3 and M4 operate alternately. Fig. 9 As shown, the waveform is Fig.10 shown.

[0106] When M3 is turned on, M4 is turned off, and the DC bus charges the inductor L to generate current i1; when M3 is turned off, the current in L flows through the body diode of M4 to generate current i2. At this time, the current i in the inductor L is L is negative, in steady state,

[0107] αV bus =V sc

[0108] In an optional embodiment, the virtual capacitor controller is an outer control algorithm for realizing voltage balance control of the solar-storage direct-flexible system, and its main functions are as follows:

[0109] (1) When the bus voltage balancing device of the PV-storage direct-flexible system is started, an enable signal EN is sent to the current inner loop / PWM generator to enable the device;

[0110] (2) According to V shown in Table 1 bus With V sc The size relationship of I bus The relationship between the magnitude of and 0 determines the working mode of the bidirectional DC converter;

[0111] (3) Real-time monitoring of V sc1 、V bus1 to avoid over-voltage or under-voltage operation of the system.

[0112] (4) According to the invented method for vacating the bus voltage virtual capacitor of the photovoltaic storage and direct current flexible system, the working current I of the bidirectional DC converter is set. set .

[0113] In the embodiment of the present application, the specific setting process is as follows:

[0114] First, according to Fig.11 The voltage deviation ΔV in the DC bus voltage variation law of the typical PV-storage DC-flexible system shown in the figure bus The size and its temporal trend The state is divided into 4 intervals: 1, 2, 3, and 4, as shown in Table 2.

[0115] Table 2 DC bus voltage change trend and virtual capacitor demand

[0116]

[0117] Furthermore, a unified expression for the DC bus voltage change of the PV-storage DC-flexible system is defined:

[0118]

[0119] It can be seen that when λ≥0, it corresponds to interval 1 and interval 3, at which time the demand for virtual capacitance is large; when λ<0, it corresponds to interval 2 and interval 3, at which time the demand for virtual capacitance is small.

[0120] Furthermore, a unified expression for virtual capacitance is defined,

[0121]

[0122] Among them, C0 is a virtual capacitance constant, which is set according to the specific photovoltaic storage direct flexibility; k1 and k2 are virtual capacitance variation constants, which are set by empirical values.

[0123] Furthermore, according to the capacitor current voltage formula, the working current of the bidirectional DC converter is calculated:

[0124]

[0125] Among them, I setmax It is the maximum operating current of the bidirectional DC converter.

[0126] In summary, the present invention proposes a bus voltage balancing circuit and control method for a photovoltaic storage direct-flexible system. The balancing circuit designed in the present application can effectively improve the voltage stability of the system and reduce the impact caused by voltage fluctuations. By adopting a virtual capacitor controller and a current inner loop / PWM generator, the present application can accurately control the working mode of the bidirectional DC converter, thereby realizing efficient bidirectional energy flow between the supercapacitor and the DC bus. In addition, the control method of the present application can flexibly respond to different operating conditions through preset working modes and applicable scenarios, ensuring that the bus voltage can be kept stable in various scenarios.

[0127] This embodiment also provides a control method for a bus voltage balancing circuit of a photovoltaic storage direct-flexible system, including:

[0128] Establish a voltage balancing circuit based on the busbar of the target PV-storage direct-flexible system;

[0129] Several working modes and applicable scenarios are preset, and the working modes include boost mode 1, boost mode 2, buck mode 1 and buck mode 2, and each working mode corresponds to an applicable scenario;

[0130] The control switches in the control voltage balancing circuit are used to switch the working mode. The control voltage balancing circuit includes four control switches. The working mode is switched through the logic operation of the control switches.

[0131] The above-mentioned unit modules may be embedded in or independent of a processor in a computer device in the form of hardware, or may be stored in a memory in a computer device in the form of software, so that the processor can call and execute operations corresponding to the above-mentioned modules.

[0132] This embodiment also provides a computer device, which may be a terminal, and its internal structure diagram may be as shown in FIG. Fig.14 As shown. The computer device includes a processor, a memory, a communication interface, a display screen and an input device connected through a system bus. Among them, the processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The communication interface of the computer device is used to communicate with an external terminal in a wired or wireless manner, and the wireless manner can be achieved through WIFI, an operator network, NFC (near field communication) or other technologies. When the computer program is executed by the processor, a control method for the bus voltage balancing circuit of a photovoltaic storage direct-flexible system is implemented. The display screen of the computer device can be a liquid crystal display screen or an electronic ink display screen, and the input device of the computer device can be a touch layer covered on the display screen, or a button, trackball or touchpad set on the computer device housing, or an external keyboard, touchpad or mouse.

[0133] This embodiment further provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the following steps are implemented:

[0134] Establish a voltage balancing circuit based on the busbar of the target PV-storage direct-flexible system;

[0135] Several working modes and applicable scenarios are preset, and the working modes include boost mode 1, boost mode 2, buck mode 1 and buck mode 2, and each working mode corresponds to an applicable scenario;

[0136] The control switches in the control voltage balancing circuit are used to switch the working mode. The control voltage balancing circuit includes four control switches. The working mode is switched through the logic operation of the control switches.

[0137] Example 2

[0138] Reference Figure 12-13 , which is an embodiment of the present invention, provides a bus voltage balancing circuit and control method for a photovoltaic storage direct-flexible system. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through experiments.

[0139] In one embodiment provided in the present application, Figure 2The photovoltaic storage direct-flexible system shown in the figure is a new energy system that combines photovoltaic power generation, energy storage system and DC power distribution technology. The main components of the system include photovoltaic power generation components, energy storage batteries, low-voltage AC loads, etc. Figure 2 In the photovoltaic storage direct-flexible system shown, AC / DC bidirectional converter 1 connects the DC bus and low-voltage station area 1, DC / DC bidirectional converter 1 connects the DC bus and the photovoltaic array, DC / DC bidirectional converter 2 connects the DC bus and the lithium iron phosphate energy storage battery pack, and AC / DC bidirectional converter 2 connects the DC bus and low-voltage station area 2.

[0140] The stability of bus voltage is crucial for the reliable operation of the photovoltaic storage direct-flexible system. However, due to factors such as the influence of weather / sunshine intensity on the output of the photovoltaic array, the influence of health status / temperature and charge status on the charging and discharging of the energy storage battery, and the drastic fluctuations in the system load, the bus voltage of the photovoltaic storage direct-flexible system usually fluctuates within a certain range. The instability of the DC bus voltage may cause equipment damage, reduced system efficiency, reduced power supply quality, and reduced energy storage battery life.

[0141] The long-term DC bus voltage results obtained by using the invented PV-storage DC-flexible system bus voltage balancing device and control method are as follows: Fig.12 As shown in the figure, it can be seen that the DC bus voltage is stable around the set value of 565V, and the maximum deviation is only 1.68V.

[0142] like Fig.13 The figure shows the supercapacitor output current curve when the load power of the solar-storage direct-flexible system undergoes a step change. It can be seen that the virtual capacitor control designed in the present invention can achieve fast current output / absorption of the supercapacitor, which has a positive effect on stabilizing the bus DC voltage.

[0143] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

[0144] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of complete hardware embodiments, complete software embodiments, or embodiments in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code. The scheme in the embodiments of the present application can be implemented in various computer languages, for example, object-oriented programming language Java and literal scripting language JavaScript, etc.

[0145] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0146] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0147] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process in the computer or other programmable device. Figure 1 A process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0148] Although the preferred embodiments of the present application have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0149] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A bus voltage balancing circuit for a photovoltaic storage direct-flexible system, characterized in that: include: Bidirectional DC converter, virtual capacitor controller and current inner loop / PWM generator; The bidirectional DC converter is an electric energy converter connecting the supercapacitor and the DC bus of the target photovoltaic storage and flexible system; The bidirectional DC converter includes a plurality of power tubes, a plurality of resistors, a plurality of inductors, a plurality of capacitors and a plurality of current sensors.

2. The bus voltage balancing circuit of the photovoltaic energy storage direct-flexible system according to claim 1, characterized in that: The current inner loop / PWM generator is used to control a plurality of power tubes in the bidirectional DC converter to switch working modes.

3. The bus voltage balancing circuit of the photovoltaic energy storage direct-flexible system as claimed in claim 2, characterized in that: There are several working modes, and each working mode corresponds to an applicable scenario; The number of the working modes depends on the number of control methods of the current inner loop / PWM generator.

4. The bus voltage balancing circuit of the photovoltaic energy storage direct-flexible system as claimed in claim 3, characterized in that: The left side of the bidirectional DC converter is connected to a physical supercapacitor and the right side is connected to the DC bus of the photovoltaic storage and direct-flexible system. The current inner loop / PWM generator controls several power tubes in the bidirectional DC converter to perform working mode conversion, and controls the bidirectional energy flow between the supercapacitor and the DC bus of the photovoltaic storage and direct-flexible system through the working mode conversion.

5. The bus voltage balancing circuit of the photovoltaic energy storage direct-flexible system as claimed in claim 4, characterized in that: The working modes include boost mode 1, boost mode 2, buck mode 1 and buck mode 2.

6. The bus voltage balancing circuit of the photovoltaic energy storage direct-flexible system as claimed in claim 5, characterized in that: The working mode also includes: Boost mode 1 corresponds to the first applicable scenario, and at this time the supercapacitor is in a boost discharge state; Boost mode 2 corresponds to the second applicable scenario, and at this time the DC bus of the target PV-storage DC-flexible system is in a boost charging state; Buck mode 1 corresponds to the third applicable scenario, and at this time the supercapacitor is in a buck discharge state; Buck mode 2 corresponds to the fourth applicable scenario, and at this time the DC bus of the target photovoltaic storage direct-flexible system is in a buck charging state.

7. The bus voltage balancing circuit of the photovoltaic energy storage direct-flexible system as claimed in claim 6, characterized in that: The applicable scenarios include: When in the first scenario, the DC bus voltage of the target PV-storage DC-flexible system is not less than the supercapacitor voltage; When in the second scenario, the DC bus voltage of the target PV-storage DC-flexible system is less than the supercapacitor voltage; When in the third scenario, the DC bus voltage of the target photovoltaic storage direct-flexible system is less than the supercapacitor voltage; When in the fourth scenario, the target DC bus voltage of the photovoltaic storage direct-flexible system is not less than the supercapacitor voltage.

8. A control method for a bus voltage balancing circuit of a solar-storage direct-flexible system, characterized in that: include: Establish a voltage balancing circuit based on the busbar of the target PV-storage direct-flexible system; Several working modes and applicable scenarios are preset, the working modes include boost mode 1, boost mode 2, buck mode 1 and buck mode 2, and each working mode corresponds to an applicable scenario; The control switches in the control voltage balancing circuit are used to switch the working mode. The control voltage balancing circuit includes four control switches. The working mode is switched through the logic operation of the control switches.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the method according to claim 8 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to claim 8 are implemented.

Images