A limit management control method for hybrid energy storage system

Abstract

The present invention is based on a hybrid energy storage system limit management and control method, including a battery module, a supercapacitor module, a power distribution module, a limit management module, a battery charge and discharge control module and a supercapacitor charge and discharge control module; the system compensates for the system's shortfall or surplus power through the supercapacitor module and the battery module; the limit management module can control the battery module power limit and the supercapacitor module to operate in a set state of charge interval, the power distribution module controls the battery module to bear the low-frequency power component, and the supercapacitor module to bear the high-frequency power component; when the supercapacitor state of charge exceeds the limit and continues to charge and discharge, the battery only emits or absorbs the low-frequency power component, avoiding the battery from bearing too much high-frequency components, damaging the internal structure, and avoiding spike changes in voltage and current at the beginning. The system can control the charging and discharging of batteries and supercapacitors to meet their storage and release characteristics, and can extend the service life of the energy storage system.

Description

Technical Field

[0001] The present invention relates to the technical field of electric energy storage systems, and in particular to a hybrid energy storage system limit management and control method. Background Art

[0002] With the development of economy, traditional energy is becoming increasingly scarce, and environmental pollution is becoming more and more serious. Countries have begun to turn their attention to the development of new clean energy. The development of renewable energy power (REP) technology has become an inevitable choice to solve the problems brought by traditional energy. Microgrid technology is an important form of effective utilization of distributed renewable energy. However, distributed power generation is very different from traditional power sources. Its main characteristics are the randomness and intermittency of distributed power generation output such as wind and light, which will have a great impact on the safety and stability of microgrids. Distributed power sources represented by photovoltaic power generation have received widespread attention. The unstable power generation characteristics of distributed power sources themselves lead to intermittent fluctuations in the system, so corresponding energy storage units are needed to compensate for the system's shortage or surplus power to maintain the stability of the DC bus voltage. In order to ensure the safe and stable operation of the system, energy storage devices have become an important part of the microgrid system. Energy storage devices can be divided into power-type energy storage and energy-type energy storage. Power-type energy storage devices have the characteristics of fast response speed, long cycle charge and discharge life, and fast charge and discharge rate, and can generally be used to smooth the power output of distributed power generation; energy-type energy storage devices have the characteristics of long energy storage time and large energy storage capacity, and are suitable for peak load shaving and valley filling of system loads. Lead-acid batteries are widely used in energy storage systems due to their high energy density and economy; however, batteries have low power density and short service life, and are not suitable for high-power charging and discharging. Supercapacitors have higher power density and cycle life than batteries, and are complementary to batteries in performance. The hybrid energy storage system composed of these two devices can make full use of the advantages of both to achieve good system performance. Therefore, the optimal configuration of the energy storage system is of great significance to the economy and power supply reliability of the microgrid.

[0003] The current status of domestic research is as follows: some early literature mainly studies based on a single energy storage configuration and mainly considers the impact of photovoltaic output. Some literature reviews write that energy storage systems can be composed of a single energy storage form and multiple energy storage forms respectively; in the process of controlling the power of new energy grid-connected power, comprehensive consideration of system cost, volume and other factors requires the energy storage system to have the characteristics of high power, high energy density, and long life; in large-scale grid-connected systems of new energy power generation such as wind power and photovoltaic power generation, both energy storage structures are used; in small-scale connected microgrids, due to the intermittent nature of new energy power generation, the energy storage unit must have a high energy density, and at the same time, the rapid fluctuation of load requires the energy storage unit to have a high power density. Therefore, a composite energy storage system composed of energy storage units with high power density and high energy density has broad application prospects in microgrids; some literature shows that in isolated photovoltaic power generation systems, the performance of battery-supercapacitor hybrid energy storage systems is better than that of single battery energy storage systems; some literature shows that battery-supercapacitor hybrid energy storage systems not only have the characteristics of high energy density and high power density, but also can extend the use of batteries life; some literature qualitatively analyzes the role of the hybrid energy storage system in extending the power and service life of the battery; some literature considers that the current cost of energy storage devices is high, and its power generation cost is higher than the grid price, and the economic efficiency of the microgrid is obviously insufficient; some literature proposes a stability criterion derivation method based on the mixed potential function theory, which is suitable for the droop control system, and obtains the stability criterion of the DC microgrid; the criterion shows that the large disturbance stability of the DC microgrid with droop control is related to the system parameters of each converter and the proportion of the output power of each power supply to the load power, and the simulation verifies the accuracy of the proposed method and stability criterion; some literature adopts an energy storage system different from that composed of a single energy storage medium, namely the hybrid energy storage system (HESS); HESS takes into account the characteristics of high power density, high energy density and long operating life, and has received widespread attention in recent years; some literature proposes a hybrid microgrid segmented coordination control strategy to solve the power fluctuation problem caused by the output change of micro-sources, load changes and the change of charging and discharging power of the energy storage device due to the state of charge in the AC / DC hybrid microgrid.

[0004] The current status of foreign research is as follows: some related literature proposes a dual-active full-bridge DC / DC converter, which uses a high-frequency transformer to achieve electrical isolation and increase the safety of the system. The structure has high symmetry, simple control method, and a wide adjustable range of voltage ratio, but the components are relatively high in cost; the DC microgrid can operate in two modes: grid-connected and off-grid; the stability of the DC bus voltage is the most important indicator for measuring power balance; when the DC microgrid is in the grid-connected operation mode, the DC microgrid exchanges energy with the public grid through the grid-connected inverter, and the DC bus voltage is maintained by the grid-connected inverter; when the AC grid or the grid-connected inverter fails, the DC microgrid switches to the off-grid operation mode, and the DC bus voltage is mainly maintained stable by the distributed power supply and the hybrid energy storage system; some literature proposes a decentralized HESS control method, in which the battery and supercapacitor use virtual resistance and virtual capacitor droop control respectively, and the power distribution between different and the same energy storage media is realized according to different virtual parameters; some literature adopts a control method including supercapacitor SOC self-recovery, and the supercapacitor SOC can be restored to the starting value after a step change. Although this method can ensure that the supercapacitor operates in a safe range, it reduces the capacity utilization of the supercapacitor and is a passive control.

[0005] In a hybrid energy storage system, different types of energy storage devices can exchange energy with the DC bus through different connection methods. Considering the performance and economy of the system, an effective energy management strategy is needed to reasonably configure each energy storage device so that the advantages of the energy storage devices complement each other and the system operates reliably and economically. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a limit management and control method based on a hybrid energy storage system. The hybrid energy storage system includes a supercapacitor and a battery. When the supercapacitor's state of charge is lower than a lower limit and continues to discharge, and when the supercapacitor's state of charge is higher than an upper limit and continues to charge, it is proposed to control the power borne by the battery during this period, so that the battery still only bears the low-frequency component during this period, thereby avoiding damage to the battery caused by the supercapacitor not operating during this period due to the entire power being borne by the battery, thereby extending the battery life and improving economic benefits.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0008] Based on a hybrid energy storage system limit management and control method, including a wind power generation module, a photovoltaic power generation module, a hybrid energy storage system, and an AC load and a DC load, the wind power generation module and the photovoltaic power generation module are connected to the AC load and the DC load through a DC bus, and are used to provide working voltage for the AC load and the DC load, and the hybrid energy storage system is used to compensate for the system's shortfall or surplus power and thus maintain the DC bus voltage at a set value, characterized in that: the hybrid energy storage system includes a battery module and a supercapacitor module, a power distribution module, a battery power and supercapacitor limit management module, and a battery charge and discharge control module and a supercapacitor charge and discharge control module;

[0009] The power distribution module is used to obtain the power of the supercapacitor module and the battery module and the corresponding current value when compensating for the shortage or surplus power of the system;

[0010] The battery power and supercapacitor limit management module is used to control the supercapacitor charge state to reach the limit value, and then redistribute the power borne by the supercapacitor and the battery. The battery module bears the low-frequency power component, and the supercapacitor stops charging and discharging during its limit period, and bears the high-frequency component during the rest of the normal operation period;

[0011] The battery charge and discharge control module is used to control the battery module to be in any working state of charging, discharging and inaction, and the supercapacitor charge and discharge control module is used to control the supercapacitor module to be in any working state of charging, discharging and inaction.

[0012] The method by which the power distribution module obtains the deficit or surplus power of the compensation system is as follows:

[0013] Obtain the DC bus voltage power Pdc, AC load power PLS, DC load power PLC, wind power Power_Wind, and photovoltaic power Ppv. The remaining power Phess is calculated as follows:

[0014] Phess=Pdc+(PLC+PLS)-Ppv-Power_Wind;

[0015] Since the battery module bears the low-frequency power component, the remaining power is distributed through low-pass filtering to obtain the battery reference power Pb_ref. The battery reference power is divided by the battery voltage Ubatt to obtain the battery reference current ib_ref. Similarly, the supercapacitor reference power Psc_ref, supercapacitor voltage Ucs and supercapacitor reference current isc_ref are obtained.

[0016] The wind power generation module includes a wind turbine and a permanent magnet synchronous motor. The output end of the permanent magnet synchronous motor is converted from AC to DC through a universal bridge and realizes DC output. The maximum power tracking algorithm is used to realize the maximum power tracking of the wind power generation module through IGBT gate-level control.

[0017] The photovoltaic power generation module includes a photovoltaic panel, the output end of the photovoltaic panel is connected to the IGBT gate level, and the maximum power tracking algorithm is adopted to realize the maximum power tracking of the photovoltaic power generation module through the IGBT gate level control.

[0018] The AC load input terminal is connected to the DC bus through a DC / AC inverter.

[0019] The battery charge and discharge control module includes an IGBT gate level S2 and an IGBT gate level S3. The positive electrode of the battery module output end is connected to one end of the inductor L1, the other end of the inductor L1 is connected to the D end of the IGBT gate level S2, the S end of the IGBT gate level S2 is connected to the negative electrode of the battery module output end, the other end of the inductor L1 is connected to the S end of the IGBT gate level S3, the D end of the IGBT gate level S3 is connected to the positive electrode of the DC bus, and the negative electrode of the battery module output end is connected to the negative electrode of the DC bus;

[0020] The supercapacitor charge and discharge control module includes an IGBT gate level S4 and an IGBT gate level S5. The positive electrode of the output end of the supercapacitor module is connected to one end of the inductor L3, the other end of the inductor L3 is connected to the D end of the IGBT gate level S4, the S end of the IGBT gate level S4 is connected to the negative electrode of the output end of the supercapacitor module, the other end of the inductor L3 is connected to the S end of the IGBT gate level S5, the D end of the IGBT gate level S5 is connected to the positive electrode of the DC bus, and the negative electrode of the output end of the supercapacitor module is connected to the negative electrode of the DC bus.

[0021] The g-end of the IGBT gate level S2 and the g-end of the IGBT gate level S3 are connected to the battery trigger pulse module, which is used to send a battery charging trigger signal or a battery discharging trigger signal, thereby controlling the battery module to be in a charging or discharging state; the m-end of the IGBT gate level S2 and the m-end of the IGBT gate level S3 are both connected to the ground terminal;

[0022] The g-end of IGBT gate level S4 and the g-end of IGBT gate level S5 are connected to the supercapacitor trigger pulse module, which is used to send a supercapacitor charging trigger signal or a supercapacitor discharging trigger signal, thereby controlling the supercapacitor module to be in a charging or discharging state; the m-end of IGBT gate level S4 and the m-end of IGBT gate level S5 are both connected to the ground terminal.

[0023] The battery power and supercapacitor limit management module controls the battery and supercapacitor to operate within the set state of charge range, and each bears the corresponding power component to operate; when the battery state of charge is operating normally, due to the fast charging and discharging speed of the supercapacitor, if the supercapacitor state of charge is lower than the set lower limit and is still in the discharging state, the supercapacitor discharge is restricted; if the supercapacitor state of charge is higher than the set upper limit and is still in the charging state, the supercapacitor charging is restricted; when the supercapacitor is limited to charge, the battery only bears the low-frequency component.

[0024] The beneficial effects that can be achieved by this method based on a hybrid energy storage system limit management are as follows: supercapacitor charge state limit management can be well applied to AC / DC hybrid energy storage microgrids containing wind power and photovoltaics to avoid the impact of excessive charging and discharging of supercapacitors on their life due to their fast reaction speed; when the supercapacitor charge state is lower than the lower limit and continues to discharge and exceeds the upper limit and continues to charge, a battery charge and discharge power control management strategy is proposed to enable it to only emit or absorb low-frequency power components, which can prevent spike changes in the battery voltage and current at the beginning, and at the same time avoid damage to the battery caused by frequent voltage and current fluctuations during the above-mentioned supercapacitor charge state limit period, thereby extending the battery service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a structural schematic diagram of a hybrid energy storage system limit management control method based on the present invention.

[0026] Figure 2 It is a flow chart of a hybrid energy storage system limit management control method based on the present invention.

[0027] Figure 3 It is a schematic diagram of a wind power generation module in a hybrid energy storage system limit management control method according to the present invention.

[0028] Figure 4 It is a schematic diagram of a photovoltaic power generation module in a hybrid energy storage system limit management control method based on the present invention.

[0029] Figure 5 It is a schematic diagram of a power distribution module in a hybrid energy storage system limit management control method according to the present invention.

[0030] Figure 6 It is a schematic diagram of a battery power and supercapacitor limit management module in a hybrid energy storage system limit management control method based on the present invention.

[0031] Figure 7 It is a schematic diagram of a battery trigger pulse module in a hybrid energy storage system limit management control method based on the present invention.

[0032] Figure 8 It is a schematic diagram of a supercapacitor trigger pulse module in a hybrid energy storage system limit management control method based on the present invention.

[0033] Fig. 9 It is a schematic diagram of a battery charging and discharging control module in a hybrid energy storage system limit management control method according to the present invention.

[0034] Fig.10 It is a schematic diagram of a supercapacitor charging and discharging control module in a hybrid energy storage system limit management control method according to the present invention.

[0035] Fig.11 It is a schematic diagram of battery trigger pulses during the simulation process of the present invention.

[0036] Fig.12 It is a schematic diagram of supercapacitor trigger pulse during the simulation process of the present invention.

[0037] Fig.13 It is a schematic diagram of the maximum power tracking output power curve of the wind turbine and photovoltaic during the simulation process of the present invention.

[0038] Fig.14 It is a schematic diagram of power curves of DC load and AC load during the simulation process of the present invention.

[0039] Fig.15 It is a schematic diagram of hybrid energy storage power during the simulation process of the present invention.

[0040] Fig.16 It is a schematic diagram of power distribution between batteries and supercapacitors during the simulation process of the present invention.

[0041] Fig.17 It is a schematic diagram of the charge state curve of the supercapacitor without using limit management during the simulation process of the present invention.

[0042] Fig.18 It is a schematic diagram of the charge state curve of the supercapacitor using limit management during the simulation process of the present invention.

[0043] Fig.19 It is a schematic diagram of voltage, current and power curves when the battery is not managed by limit value during the simulation process of the present invention.

[0044] Fig. 20 It is a schematic diagram of voltage, current and power curves when the battery adopts limit value management during the simulation process of the present invention.

[0045] Fig.21 It is a schematic diagram of the residual power curve during the simulation process of the independent photovoltaic DC microgrid hybrid energy storage operation of the present invention.

[0046] Fig. 22It is a schematic diagram of the reference power curves of batteries and supercapacitors during the simulation of the operation of the independent photovoltaic DC microgrid hybrid energy storage system of the present invention.

[0047] Fig.23 It is a schematic diagram of voltage, current and power curves when the battery does not adopt limit management during the independent photovoltaic DC microgrid hybrid energy storage operation simulation process of the present invention.

[0048] Fig.24 It is a schematic diagram of voltage, current and power curves when the battery adopts limit management during the independent photovoltaic DC microgrid hybrid energy storage operation simulation process of the present invention. DETAILED DESCRIPTION

[0049] The present invention is further described below in conjunction with the accompanying drawings and specific preferred embodiments.

[0050] like Figure 1 and Figure 2 As shown, based on a hybrid energy storage system limit management and control method, it includes a wind power generation module, a photovoltaic power generation module, a hybrid energy storage system, and an AC load and a DC load. The wind power generation module and the photovoltaic power generation module are connected to the AC load and the DC load through a DC bus to provide a working voltage for the AC load and the DC load. The hybrid energy storage system is used to compensate for the system's shortfall or surplus power and thus keep the DC bus voltage at a set value. The hybrid energy storage system includes a battery module and a supercapacitor module, a power distribution module, a battery power and supercapacitor limit management module, and a battery charge and discharge control module and a supercapacitor charge and discharge control module;

[0051] The power distribution module is used to obtain the power of the supercapacitor module and the battery module and the corresponding current value when compensating for the shortage or surplus power of the system;

[0052] The battery power and supercapacitor limit management module is used to control the supercapacitor charge state to reach the limit value, and then redistribute the power borne by the supercapacitor and the battery. The battery module bears the low-frequency power component, and the supercapacitor stops charging and discharging during its limit period, and bears the high-frequency component during the rest of the normal operation period;

[0053] The battery charge and discharge control module is used to control the battery module to be in any working state of charging, discharging and inaction, and the supercapacitor charge and discharge control module is used to control the supercapacitor module to be in any working state of charging, discharging and inaction.

[0054] In this embodiment, the AC load input terminal is connected to the DC bus through a DC / AC inverter. Figure 1Inver_Control in is used to convert and connect DC and AC loads. The line parameters of AC and DC loads, power generation and circuit breakers can be set according to the power generated by wind power and photovoltaic new energy.

[0055] In this embodiment, Figure 5 As shown, 600V represents the reference value of the reference DC bus voltage, Udc represents the bus voltage value measured in the main circuit, and the difference between the two is used for proportional integral PI control to obtain the DC bus current idc_ref. The product of this result and the DC bus voltage is used as the power Pdc required to maintain the stability of the DC bus voltage; the remaining power Phess is distributed through the low-pass filter Analog Filter Design to obtain the low-frequency component Pb_ref ​​and the high-frequency component Psc_ref in the remaining power, and the low-frequency power is divided by the battery voltage Ubatt to obtain the battery reference current Ib_ref. Figure 5 The medium load power PL = PLC + PLS. The method by which the power distribution module obtains the deficit or surplus power of the compensation system is:

[0056] Obtain the DC bus voltage power Pdc, AC load power PLS, DC load power PLC, wind power Power_Wind, and photovoltaic power Ppv. The remaining power Phess is calculated as follows:

[0057] Phess=Pdc+(PLC+PLS)-Ppv-Power_Wind;

[0058] Since the battery module bears the low-frequency power component, the remaining power is distributed through low-pass filtering to obtain the battery reference power Pb_ref. The battery reference power is divided by the battery voltage Ubatt to obtain the battery reference current ib_ref. Similarly, the supercapacitor reference power Psc_ref, supercapacitor voltage Ucs and supercapacitor reference current isc_ref are obtained.

[0059] In this embodiment, Figure 3 As shown, the wind power generation module includes a wind turbine wind_turbine and a permanent magnet synchronous motor PMGM. The output end of the permanent magnet synchronous motor performs AC-DC conversion and realizes DC output through a universal bridge Universal Bridge; IGBT is an insulated gate bipolar transistor, which is used to control the output power; the S-Function function is a maximum power tracking algorithm, which generates a trigger pulse through a PWM generator to control the IGBT gate-level g end to achieve maximum power tracking.

[0060] like Figure 4As shown, the photovoltaic power generation module includes a photovoltaic panel, the output end of the photovoltaic panel is connected to the IGBT gate level, and the maximum power tracking algorithm is adopted to realize the maximum power tracking of the photovoltaic power generation module through the IGBT gate level control.

[0061] Furthermore, the battery m port outputs the battery voltage, current and state of charge data; the supercapacitor m port outputs the supercapacitor voltage, current and state of charge data. After passing through BusSelector, the m port outputs the battery and supercapacitor's respective voltage (Ubatt (battery) / Usc (supercapacitor)), current (Ibatt (battery) / Isc (supercapacitor)), and state of charge (SOC1 (battery) / SOC2 (supercapacitor)).

[0062] In this embodiment, Fig. 9 As shown, the battery charge and discharge control module includes an IGBT gate level S2 and an IGBT gate level S3, the positive electrode of the battery module output end is connected to one end of the inductor L1, the other end of the inductor L1 is connected to the D end of the IGBT gate level S2, the S end of the IGBT gate level S2 is connected to the negative electrode of the battery module output end, the other end of the inductor L1 is connected to the S end of the IGBT gate level S3, the D end of the IGBT gate level S3 is connected to the positive electrode of the DC bus, and the negative electrode of the battery module output end is connected to the negative electrode of the DC bus;

[0063] like Fig.10 As shown, the supercapacitor charge and discharge control module includes an IGBT gate level S4 and an IGBT gate level S5, the positive electrode of the output end of the supercapacitor module is connected to one end of the inductor L3, the other end of the inductor L3 is connected to the D end of the IGBT gate level S4, the S end of the IGBT gate level S4 is connected to the negative electrode of the output end of the supercapacitor module, the other end of the inductor L3 is connected to the S end of the IGBT gate level S5, the D end of the IGBT gate level S5 is connected to the positive electrode of the DC bus, and the negative electrode of the output end of the supercapacitor module is connected to the negative electrode of the DC bus.

[0064] Further, the g-end of the IGBT gate level S2 and the g-end of the IGBT gate level S3 are connected to the battery trigger pulse module, and the battery trigger pulse module is used to send a battery charging trigger signal or a battery discharging trigger signal, thereby controlling the battery module to be in a charging or discharging state; the m-end of the IGBT gate level S2 and the m-end of the IGBT gate level S3 are both connected to the ground terminal;

[0065] The g-end of IGBT gate level S4 and the g-end of IGBT gate level S5 are connected to the supercapacitor trigger pulse module, which is used to send a supercapacitor charging trigger signal or a supercapacitor discharging trigger signal, thereby controlling the supercapacitor module to be in a charging or discharging state; the m-end of IGBT gate level S4 and the m-end of IGBT gate level S5 are both connected to the ground terminal.

[0066] Fig. 9 In the figure, G1 represents the discharge trigger signal of the battery, and G2 represents the charge trigger signal of the battery. By controlling the IGBT gate level or the power MOSFET gate level, the battery charge and discharge are controlled. Fig.10 In FIG. 1 , G3 represents the discharge trigger signal of the supercapacitor, and G4 represents the charge trigger signal of the supercapacitor. The charging and discharging of the supercapacitor are controlled by controlling the IGBT gate level or the power MOSFET gate level.

[0067] In this embodiment, the battery power and supercapacitor limit management module controls the battery and the supercapacitor to operate within the set state of charge range, and each bears the corresponding power component to operate; when the battery state of charge operates normally, due to the fast charging and discharging speed of the supercapacitor, if the supercapacitor state of charge is lower than the set lower limit and is still in the discharging state, the supercapacitor is restricted from discharging; if the supercapacitor state of charge is higher than the set upper limit and is still in the charging state, the supercapacitor is restricted from charging; when the supercapacitor is restricted from charging, the battery only bears the low-frequency component.

[0068] The battery limit is based on the supercapacitor state of charge limit. During the supercapacitor limit period, the supercapacitor no longer operates, but still needs to be charged and discharged. At this moment, the charging and discharging power should not be borne entirely by the battery. If it is borne, it will seriously damage the battery life. Therefore, it is necessary to limit the battery charging and discharging so that it only bears the low-frequency component. During the supercapacitor state of charge limit period, its high-frequency component can be transmitted to the large power grid for smoothing. The specific method is the existing technology and will not be discussed in detail in this application.

[0069] Battery power and supercapacitor limit management module such as Figure 6 As shown, the remaining power Phess, supercapacitor state of charge SOC2, battery reference power Pb_ref ​​and supercapacitor reference power Psc_ref are used as system inputs. The constants represent the upper and lower limits of the supercapacitor state of charge setting, which are usually set to [20 80]. In this embodiment, [39.33 39.36] is used to prove the effectiveness of the control model, which is convenient for analysis. After being processed by the limit management function, the new battery reference power Pb_ref_1 and supercapacitor reference power Psc_ref_1 are obtained; the battery reference current Ib_ref_1 and supercapacitor reference current Isc_ref_1 are obtained.

[0070] In this embodiment, the battery trigger pulse module is as follows: Figure 7As shown, the difference between the battery reference current Ib_ref_1 output by the battery power and supercapacitor limit management module and the main circuit battery current Ibatt is used for PI control. The output result passes through the Saturation module to limit the input signal between the saturation upper and lower limits. After PWM control, the output high / low potential is output. Then, through the Switch module, the high and low levels of the batteries G1 and G2 are judged based on the newly obtained Ib_ref_1 as the control input, that is, 1 indicates that the high level triggers the IGBT gate level, and 0 indicates that the low level IGBT does not act, thereby controlling the battery charging and discharging. Fig.11 As shown, Fig.11 The upper middle part is the G1 trigger signal, and the lower part is the G2 trigger signal. The high and low levels of G1 and G2 are complementary. A high level of G1 indicates that the battery is discharging, and a high level of G2 indicates that the battery is charging.

[0071] Supercapacitor trigger pulse module such as Figure 8 As shown, its principle is the same as that of the battery trigger pulse module. The high and low levels of G3 and G4 are controlled by the supercapacitor trigger pulse module, thereby controlling the charging and discharging of the supercapacitor. Fig.12 As shown, Fig.12 The upper middle part is the G3 trigger signal, and the lower part is the G4 trigger signal. The high and low levels of G3 and G4 are complementary. A high level of G3 indicates that the supercapacitor is discharging, and a high level of G4 indicates that the supercapacitor is charging.

[0072] In summary, after the battery power and supercapacitor limit management module is used, the supercapacitor trigger pulse and the battery trigger pulse are controlled, so that the supercapacitor will not be easily overcharged and over-discharged due to its fast reaction speed, thereby extending the service life of the supercapacitor; at the same time, when the supercapacitor charge state is lower than the lower limit and continues to discharge and exceeds the upper limit and continues to charge, a battery charge and discharge power control management strategy is proposed, so that it only emits or absorbs low-frequency power components, avoiding damage to the battery caused by frequent oscillations of the battery voltage and current during the above-mentioned limit period and rapid changes in the battery voltage and current at the startup time, thereby extending the battery service life and thus improving the economic benefits of the entire system.

[0073] This method based on the limit management control of a hybrid energy storage system is simulated. During the simulation process, a simulink model is built according to the mathematical models of photovoltaic power generation and wind power generation, and the maximum power tracking control of each is realized. According to the above-mentioned supercapacitor module and battery module control method, the simulation results are as follows:

[0074] Wind turbine and photovoltaic maximum power tracking output power Fig.13 As shown in the figure, the upper part is the wind turbine output power. When the wind speed increases at 2 seconds, the output power increases. The lower part is the photovoltaic output power. When the light intensity decreases at 1 second, the output power decreases. Fig.14As shown, the upper part is the DC load power, and the lower part is the AC load power. Both the DC load and the AC load power suddenly increase at 1 second and suddenly decrease at 2 seconds. When photovoltaic and wind power generation are connected to the AC / DC hybrid energy storage system, the DC bus voltage is stable.

[0075] During the simulation, the hybrid energy storage power Phess is as follows: Fig.15 As shown, the battery and supercapacitor power distribution is as follows Fig.16 As shown in the figure, it can be seen that the power borne by the battery is relatively smooth, and the power borne by the supercapacitor has a large variation range, which meets the characteristics of their respective power storage.

[0076] Take the simulation running time of 3 seconds as an example. Fig.17 To manage the supercapacitor state of charge SOC2 curve for unused limit values, Fig.18 In order to use the limit value to manage the supercapacitor state of charge SOC2 curve, the simulation sets the lower limit value to 39.33% and the upper limit value to 39.36%. Fig.17 , Fig.18 The supercapacitor state of charge limit management is below the lower limit and the supercapacitor still needs to discharge. At this time, the supercapacitor no longer discharges and the state of charge remains unchanged. According to actual needs, the lower limit of the supercapacitor state of charge can be set to 20% and the upper limit can be set to 80%.

[0077] at the same time, Fig.19 This is the curve of voltage, current and power when the battery is not managed by limit value. Fig. 20 The voltage, current and power curves for battery usage limit management are shown below. Fig.19 and Fig. 20 From top to bottom are the curves of voltage, current and power. Fig.19 and Fig. 20 By comparison, it can be seen that after the start-up, the battery voltage and current initially change slowly from rapid changes, reducing the impact on the battery. The residual power variation in the above simulation process is small. When the residual power fluctuates greatly, the battery voltage and current fluctuate sharply during the period when the supercapacitor state of charge is lower than the lower limit and continues to discharge and the supercapacitor state of charge is higher than the upper limit and continues to charge.

[0078] The independent photovoltaic DC microgrid hybrid energy storage operation simulation is now used to verify the correctness of the above conclusions. During the independent photovoltaic DC microgrid hybrid energy storage operation simulation, the residual power curve is as follows Fig.21 As shown, the reference power curves of batteries and supercapacitors are as follows Fig. 22 As shown, the curve with smooth fluctuation amplitude is the battery reference power curve, and the curve with large fluctuation amplitude is the supercapacitor reference power curve. Fig.23The voltage and current curves when the battery does not use power limit. Fig.24 The voltage and current curves when the battery uses power limit; Fig.23 and Fig.24 By comparison, it can be seen that after the battery adopts power limit, its voltage and current change from rapid to slow after starting, reducing the impact on the battery. During the period of 0.15-0.25 seconds, the supercapacitor SOC is lower than the lower limit and is limited. During the period of 2.5-3 seconds, the supercapacitor SOC exceeds the upper limit and is limited. When the battery does not adopt power limit Fig.23 As shown, the voltage and current fluctuate sharply during this period, affecting the battery life; using power limit as Fig.24 As shown, the curve is relatively smooth, indicating the effectiveness and rationality of battery power limitation.

[0079] The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims

1. A hybrid energy storage system limit management and control method is based on a wind power generation module, a photovoltaic power generation module, a hybrid energy storage system, and an AC load and a DC load. The wind power generation module and the photovoltaic power generation module are connected to the AC load and the DC load through a DC bus to provide a working voltage for the AC load and the DC load. The hybrid energy storage system is used to compensate for the system's shortfall or surplus power and thereby maintain the DC bus voltage at a set value, characterized in that: The hybrid energy storage system includes a battery module and a supercapacitor module, a power distribution module, a battery power and supercapacitor limit management module, and a battery charge and discharge control module and a supercapacitor charge and discharge control module; When the power distribution module is used to obtain the shortfall or surplus power of the compensation system, the power of the supercapacitor module and the battery module and the corresponding current value are obtained respectively; the method for the power distribution module to obtain the shortfall or surplus power of the compensation system is: Obtain the DC bus voltage power Pdc, AC load power PLS, DC load power PLC, wind power Power_Wind, and photovoltaic power Ppv. The remaining power Phess is calculated as follows: Phess=Pdc+(PLC+PLS)-Ppv-Power_Wind; Since the battery module bears the low-frequency power component, the remaining power is distributed through low-pass filtering to obtain the battery reference power Pb_ref. The battery reference power is divided by the battery voltage Ubatt to obtain the battery reference current ib_ref. Similarly, the supercapacitor reference power Psc_ref, supercapacitor voltage Ucs and supercapacitor reference current isc_ref are obtained. The battery power and supercapacitor limit management module is used to control the supercapacitor charge state to reach the limit value, and then redistribute the power borne by the supercapacitor and the battery, and the battery module bears the low-frequency power component; The supercapacitor module stops charging and discharging during its limit period, and bears the high-frequency component during the rest of the normal operation period; when the supercapacitor limits charging, the battery only bears the low-frequency component; The battery charge and discharge control module is used to control the battery module to be in any working state of charging, discharging and inaction, and the supercapacitor charge and discharge control module is used to control the supercapacitor module to be in any working state of charging, discharging and inaction.

2. The limit management and control method based on a hybrid energy storage system according to claim 1, characterized in that: The wind power generation module includes a wind turbine and a permanent magnet synchronous motor. The output end of the permanent magnet synchronous motor is converted from AC to DC through a universal bridge and realizes DC output. The maximum power tracking algorithm is used to realize the maximum power tracking of the wind power generation module through IGBT gate-level control. The photovoltaic power generation module includes a photovoltaic panel, the output end of the photovoltaic panel is connected to the IGBT gate level, and the maximum power tracking algorithm is adopted to realize the maximum power tracking of the photovoltaic power generation module through the IGBT gate level control.

3. The limit management and control method based on a hybrid energy storage system according to claim 1, characterized in that: The AC load input terminal is connected to the DC bus through a DC / AC inverter.

4. The limit management and control method based on a hybrid energy storage system according to claim 1, characterized in that: The battery charge and discharge control module includes an IGBT gate level S2 and an IGBT gate level S3. The positive electrode of the battery module output end is connected to one end of the inductor L1, the other end of the inductor L1 is connected to the D end of the IGBT gate level S2, the S end of the IGBT gate level S2 is connected to the negative electrode of the battery module output end, the other end of the inductor L1 is connected to the S end of the IGBT gate level S3, the D end of the IGBT gate level S3 is connected to the positive electrode of the DC bus, and the negative electrode of the battery module output end is connected to the negative electrode of the DC bus; The supercapacitor charge and discharge control module includes an IGBT gate level S4 and an IGBT gate level S5. The positive electrode of the output end of the supercapacitor module is connected to one end of the inductor L3, the other end of the inductor L3 is connected to the D end of the IGBT gate level S4, the S end of the IGBT gate level S4 is connected to the negative electrode of the output end of the supercapacitor module, the other end of the inductor L3 is connected to the S end of the IGBT gate level S5, the D end of the IGBT gate level S5 is connected to the positive electrode of the DC bus, and the negative electrode of the output end of the supercapacitor module is connected to the negative electrode of the DC bus.

5. The limit management and control method based on a hybrid energy storage system according to claim 4, characterized in that: The g-end of the IGBT gate level S2 and the g-end of the IGBT gate level S3 are connected to the battery trigger pulse module, which is used to send a battery charging trigger signal or a battery discharging trigger signal, thereby controlling the battery module to be in a charging or discharging state; the m-end of the IGBT gate level S2 and the m-end of the IGBT gate level S3 are both connected to the ground terminal; The g-end of IGBT gate level S4 and the g-end of IGBT gate level S5 are connected to the supercapacitor trigger pulse module, which is used to send a supercapacitor charging trigger signal or a supercapacitor discharging trigger signal, thereby controlling the supercapacitor module to be in a charging or discharging state; the m-end of IGBT gate level S4 and the m-end of IGBT gate level S5 are both connected to the ground terminal.

6. The limit management and control method based on a hybrid energy storage system according to claim 5, characterized in that: The battery power and supercapacitor limit management module controls the battery and supercapacitor to operate within the set state of charge range, and each bears the corresponding power component to operate; when the battery state of charge is operating normally, due to the fast charging and discharging speed of the supercapacitor, if the supercapacitor state of charge is lower than the set lower limit and is still in the discharging state, the supercapacitor discharge is restricted; if the supercapacitor state of charge is higher than the set upper limit and is still in the charging state, the supercapacitor charging is restricted; when the supercapacitor is limited to charge, the battery only bears the low-frequency component.

Images