DC microgrid based on hybrid energy storage and power supply method thereof

Abstract

A DC microgrid based on hybrid energy storage and a power supply method thereof, the DC microgrid includes a photovoltaic power generation unit, a battery, a supercapacitor, a bidirectional DC / DC converter, a DC bus L0, and a load; the photovoltaic power generation unit is connected to the DC bus L0, and the DC bus L0 is connected to the load; the DC bus L0 is connected to the bidirectional DC / DC converter, the bidirectional DC / DC converter is connected to the supercapacitor, and the supercapacitor is connected to the battery. The present invention is based on a DC microgrid and a power supply method thereof based on hybrid energy storage, adopts a multi-power supply mode, uses renewable clean energy as the main power supply, and uses hybrid energy storage as a backup. The data center microgrid can also be connected to the power grid, which can greatly improve the reliability of DC power supply.

Description

Technical Field

[0001] The present invention relates to the technical field of hybrid energy storage power supply, and in particular to a direct current microgrid based on hybrid energy storage and a power supply method thereof. Background Art

[0002] With the development of emerging industries such as big data, 5G, and artificial intelligence, massive amounts of data need to be processed, stored, and calculated, so the number of data center construction around the world has also increased. Operating data center servers and substation equipment consumes a lot of energy, and the trend of reducing energy consumption in data centers is becoming more and more obvious. Therefore, how to reduce data center energy consumption is an urgent problem to be solved.

[0003] The existing data center power supply is basically in the form of AC power supply. Considering the wide application of renewable energy in the power grid, photovoltaic power generation has the characteristics of flexibility, low pollution and safety, and has become the clean energy with the greatest development potential. Photovoltaic power generation will be affected by the environment, making it have certain volatility and intermittency, resulting in photovoltaic power generation access to microgrids affecting stability and safety. For this reason, relevant researchers have added energy storage systems to microgrids to solve the disturbances caused by photovoltaic grid connection. Considering the different characteristics of energy storage, appropriate control strategies are applied to energy storage to coordinate and control the balance of microgrid power. Summary of the invention

[0004] Considering that photovoltaic power generation units are easily affected by the environment and prone to power fluctuations, the present invention provides a DC microgrid based on hybrid energy storage and a power supply method thereof, which combines hybrid energy storage with photovoltaics to improve the reliability and safety of power supply.

[0005] The technical solution adopted by the present invention is:

[0006] A DC microgrid based on hybrid energy storage, including: photovoltaic power generation unit, battery, supercapacitor, bidirectional DC / DC converter, DC bus L0, and load;

[0007] The photovoltaic power generation unit is connected to the DC bus L0, and the DC bus L0 is connected to the load;

[0008] The DC bus L0 is connected to a bidirectional DC / DC converter, the bidirectional DC / DC converter is connected to a supercapacitor, and the supercapacitor is connected to a battery.

[0009] The storage battery is composed of a lithium battery pack composed of multiple lithium batteries, wherein the positive electrode of the lithium battery pack is connected to the positive electrode of the supercapacitor through the MOSFET tube Q3, and the negative electrode of the lithium battery pack is connected to the negative electrode of the supercapacitor;

[0010] MOSFET tube Q1 and MOSFET tube Q2 are connected to form a series branch, the positive electrode of the supercapacitor is connected to one end of the inductor L, the other end of the inductor L is connected to the series node of the series branch, the capacitor C is connected in parallel with the series branch, and the two ends of the capacitor C are respectively connected to the positive terminal and the negative terminal of the DC bus L0;

[0011] The positive electrode of the photovoltaic power generation unit is connected to the positive terminal of the DC bus L0, and the negative electrode of the photovoltaic power generation unit is connected to the negative terminal of the DC bus L0.

[0012] The battery, super capacitor and MOSFET tube Q3 constitute a hybrid energy storage unit.

[0013] The hybrid energy storage unit SOC is set to 5 ranges:

[0014]

[0015] The present invention provides a DC microgrid based on hybrid energy storage and a power supply method thereof, and the technical effects are as follows:

[0016] 1) The present invention subdivides the SOC capacity of batteries and supercapacitors into five operating states, thereby ensuring the reliability of hybrid energy storage in power supply and reducing the number of times the hybrid energy storage is charged and discharged.

[0017] 2) Taking into account that photovoltaic power generation units are easily affected by the environment and prone to power fluctuations, the present invention combines hybrid energy storage with photovoltaics to improve the reliability of power supply in data centers.

[0018] 3) The present invention takes into account the charging and discharging safety issues of batteries and supercapacitors, and sets a slow strategy for hybrid energy storage to further improve the safety of power supply in data centers.

[0019] 4) The hybrid energy storage power supply architecture of the present invention reduces the number of control switches of the battery to one, further reducing the number of hybrid energy storage converters used, thereby improving the economy to a certain extent.

[0020] 5) The hybrid energy storage power supply architecture and hybrid energy storage energy state division mentioned in the present invention take into account the energy consumption problem of the data center and the number of times the hybrid energy storage is charged and discharged, and subdivides the capacity operation state, which is beneficial to the safe operation of the data center.

[0021] 6) The present invention adopts a multi-power supply mode, using renewable clean energy as the main power supply and hybrid energy storage as a backup. The data center microgrid can also be connected to the power grid, which can greatly improve the reliability of DC power supply. Considering the data center load, the present invention can work in multiple modes to further improve the flexibility of power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the topology diagram of the DC microgrid based on hybrid energy storage.

[0023] Figure 2 This is the SOC division diagram of hybrid energy storage.

[0024] Figure 3 This is a flow chart of the energy management strategy.

[0025] Figure 4 This is the control diagram of hybrid energy storage.

[0026] Figure 5 This is a schematic diagram of voltage / current control. DETAILED DESCRIPTION

[0027] like Figure 1 As shown, the DC microgrid based on hybrid energy storage includes: a photovoltaic power generation unit 1, a battery 5, a super capacitor 4, a bidirectional DC / DC converter 3, a DC bus L0, and a load 2; wherein the photovoltaic power generation unit 1, the hybrid energy storage unit, and the load 2 are connected via the DC bus L0. The photovoltaic power generation unit 1 and the hybrid energy storage unit are connected to the positive and negative poles of the DC bus L0 respectively at the same time.

[0028] Load 2 is connected in the opposite way to the above, and the potential of the access point is the same. The specific connection method is as follows:

[0029] Photovoltaic power generation unit 1 is connected to DC bus L0, and DC bus L0 is connected to load 2;

[0030] The DC bus L0 is connected to the bidirectional DC / DC converter 3 , the bidirectional DC / DC converter 3 is connected to the super capacitor 4 , and the super capacitor 4 is connected to the battery 5 .

[0031] The storage battery 5 is composed of a lithium battery pack composed of multiple lithium batteries, wherein the positive electrode of the lithium battery pack is connected to the positive electrode of the super capacitor 4 through the MOSFET tube Q3, and the negative electrode of the lithium battery pack is connected to the negative electrode of the super capacitor 4;

[0032] MOSFET tube Q1 and MOSFET tube Q2 are connected to form a series branch, the positive electrode of the super capacitor 4 is connected to one end of the inductor L, the other end of the inductor L is connected to the series node of the series branch, the capacitor C is connected in parallel with the series branch, and the two ends of the capacitor C are respectively connected to the positive terminal and the negative terminal of the DC bus L0;

[0033] The positive electrode of the photovoltaic power generation unit 1 composed of a single photovoltaic panel is connected to the positive terminal of the DC bus L0, and the negative electrode of the photovoltaic power generation unit 1 is connected to the negative terminal of the DC bus L0.

[0034] The battery 5, super capacitor 4 and MOSFET tube Q3 constitute a hybrid energy storage unit.

[0035] Photovoltaic power generation power Ppv The hybrid energy storage power P flows into the microgrid through the DC bus L0. hess >0, the hybrid energy storage discharges and its energy flows into the microgrid; when P hess <0, hybrid energy storage charging, absorbing energy from the microgrid.

[0036] Working principle:

[0037] The present invention firstly performs the state of charge SOC of the battery 5 and the super capacitor 4 as follows: Figure 2 Divide and set the hybrid energy storage SOC into 5 ranges:

[0038]

[0039] The method is used to reasonably divide the SOC in detail, which can reduce the phenomenon of overcharge and overdischarge of hybrid energy storage. Compared with the battery 5, the supercapacitor 4 has high energy density, fast charging rate, and many rated charge and discharge times, so the supercapacitor 4 is more suitable for frequent charging. Figure 2 The energy management strategy of the DC microgrid power supply mode based on hybrid energy storage proposed in this invention is as follows: Figure 3 shown.

[0040] First, calculate the hybrid energy storage P hess ,

[0041] If P hess <0, indicating that the hybrid energy storage unit absorbs power when the supercapacitor SOC sc ≥85%, the super capacitor 4 enters the standby state, at which time the MOSFET tubes Q1 and Q2 are disconnected; when 75%≤SOC SC <85%, the supercapacitor 4 is charged slowly, at this time the MOSFET tube Q1 is turned on and Q2 is turned off; when the supercapacitor SOC SC <75%, the supercapacitor 4 is charged, at this time the MOSFET tube Q1 is turned on and Q2 is turned off; when the battery SOC bat ≥85%, the battery 5 enters the standby state, at which time the MOSFET tube Q3 is disconnected; when 75%≤SOC bat <85%, the battery 5 is slowly charged, and the MOSFET tube Q3 is turned on; when the battery SOC bat When the voltage is less than 75%, the battery 5 is charged and the MOSFET tube Q3 is turned on.

[0042] If P hess >0, indicating that the hybrid energy storage unit releases power when the supercapacitor SOC sc <15%, the super capacitor 4 enters the standby state, at which time the MOSFET tubes Q1 and Q2 are disconnected; when 15% ≤ SOC SC<25%, the supercapacitor 4 discharges slowly, at which time the MOSFET tube Q2 is turned on and Q1 is turned off; when the supercapacitor SOC SC ≥25%, the supercapacitor 4 discharges, at this time the MOSFET tube Q1 is turned on and Q2 is turned off; when the battery SOC bat <15%, the battery 5 enters the standby state, and the MOSFET tube Q3 is disconnected; when 15% ≤ SOC bat <25%, the battery 5 is slowly discharged, and the MOSFET tube Q3 is turned on; when the battery SOC bat When ≥25%, the battery 5 is discharged, and the MOSFET tube Q3 is turned on.

[0043] Figure 4 The hybrid energy storage control diagram is shown in Figure 1. First, the hybrid energy storage power P is allocated hess Through the low-pass filter, the supercapacitor distribution power Psc and the battery distribution power P are obtained respectively. bat , and then the supercapacitor SOC sc , Battery SOC bat Input to the energy management module: low-pass filter to obtain the power of the hybrid energy storage, and then through Figure 4 The connection mode of the energy management module is as follows: Figure 3 shown.

[0044] (1) If the hybrid energy storage distribution power P hess <0,

[0045] When the supercapacitor SOC sc ≥85%, battery SOC bat ≥85%, at this time, the battery reference control power P is obtained bat_ref , supercapacitor reference control power P sc_ref All are zero, and then, the MOSFET tube Q1, Q2 turn-off signal S1 and the MOSFET tube Q3 turn-off signal S7 are obtained through voltage / current control;

[0046] When supercapacitor 75%≤SOC SC <85%, battery 75%≤SOC bat <85%, at this time, the battery reference control power P′ is obtained bat_ref , supercapacitor reference control power P′ sc_ref Then, the voltage / current controller obtains the MOSFET tube Q1 turn-on signal S3, the MOSFET tube Q3 turn-on signal S5, and the hybrid energy storage is slowly charged, where:

[0047] P' sc_rd =k1×P' sc_ref

[0048] P' bat_ref =k1×P' sc_ref

[0049] SOC(t) is the state of charge of the supercapacitor / battery at a certain moment during slow charging;

[0050] When the supercapacitor SOC SC <75%, supercapacitor SOC SC <75%, at this time, the battery reference control power Pbat_ref and the supercapacitor reference control power Psc_ref are obtained, and then, through voltage / current control, the MOSFET tube Q1 turn-on signal S2 and the MOSFET tube Q3 turn-on signal S6 are obtained, and the hybrid energy storage is charged normally.

[0051] (2) If the hybrid energy storage distribution power P hess >0,

[0052] When the supercapacitor SOCsc<15% and the battery SOCbat<15%, the battery reference control power Pbat_ref and the supercapacitor reference control power Psc_ref are both zero, and then the MOSFET tube Q1, Q2 shutdown signal S1 and the MOSFET tube Q3 shutdown signal S7 are obtained through voltage / current control;

[0053] When supercapacitor 15%≤SOC SC <25%, battery 15%≤SOC bat <25%, then the battery reference control power P′ is obtained bat_ref , supercapacitor reference control power P′ sc_ref Then, the MOSFET tube Q2 turn-on signal S4 and the MOSFET tube Q3 turn-on signal S6 are obtained through voltage / current control, and the super capacitor and the battery are discharged slowly, wherein:

[0054] P' sc_ref =k2×P' sc_ref

[0055] P' sc_ref =k2×P' sc_ref

[0056] SOC(t) is the state of charge of the supercapacitor / battery at a certain moment during slow charging;

[0057] When the supercapacitor SOC SC >25%, supercapacitor SOC SC >25%, at this time, the battery reference control power P is obtainedbat_ref , supercapacitor reference control power P sc_ref Then, the MOSFET tube Q2 turn-on signal S2 and the MOSFET tube Q3 turn-on signal S8 are obtained through the voltage / current controller.

Claims

1. A DC microgrid based on hybrid energy storage, characterized by include: Photovoltaic power generation unit (1), battery (5), super capacitor (4), bidirectional DC / DC converter (3), DC bus (L0), load (2); The photovoltaic power generation unit (1) is connected to a DC bus (L0), and the DC bus (L0) is connected to a load (2); The DC bus (L0) is connected to a bidirectional DC / DC converter (3), the bidirectional DC / DC converter (3) is connected to a super capacitor (4), and the super capacitor (4) is connected to a battery (5); The storage battery (5) is composed of a lithium battery pack composed of a plurality of lithium batteries, wherein the positive electrode of the lithium battery pack is connected to the positive electrode of the super capacitor (4) through a MOSFET tube Q3, and the negative electrode of the lithium battery pack is connected to the negative electrode of the super capacitor (4); The MOSFET tube Q1 and the MOSFET tube Q2 are connected to form a series branch, the positive electrode of the super capacitor (4) is connected to one end of the inductor L, the other end of the inductor L is connected to the series node of the series branch, the capacitor C is connected in parallel with the series branch, and the two ends of the capacitor C are respectively connected to the positive terminal and the negative terminal of the DC bus (L0); The positive pole of the photovoltaic power generation unit (1) is connected to the positive terminal of the DC bus (L0), and the negative pole of the photovoltaic power generation unit (1) is connected to the negative terminal of the DC bus (L0); The energy management method of the DC microgrid power supply mode based on hybrid energy storage includes the following methods: First, calculate the hybrid energy storage P hess , If P hess <0, indicating that the hybrid energy storage unit absorbs power when the supercapacitor SOC sc ≥85%, the supercapacitor (4) enters the standby state, at which time the MOSFET tubes Q1 and Q2 are disconnected; when 75%≤SOC SC <85%, the supercapacitor (4) is slowly charged, at which time the MOSFET tube Q1 is turned on and Q2 is turned off; when the supercapacitor SOC SC <75%, the supercapacitor (4) is charged, at which time the MOSFET tube Q1 is turned on and Q2 is turned off; when the battery SOC bat ≥85%, the battery (5) enters the standby state, at which time the MOSFET tube Q3 is disconnected; when 75%≤SOC bat <85%, the battery (5) is slowly charged, and the MOSFET tube Q3 is turned on; when the battery SOC bat When the voltage is less than 75%, the battery (5) is charged and the MOSFET tube Q3 is turned on; If P hess >0, indicating that the hybrid energy storage unit releases power when the supercapacitor SOC sc <15%, the supercapacitor (4) enters the standby state, at which time the MOSFET tubes Q1 and Q2 are disconnected; when 15% ≤ SOC SC <25%, the supercapacitor (4) discharges slowly, at which time the MOSFET tube Q2 is turned on and Q1 is turned off; when the supercapacitor SOC SC ≥25%, the supercapacitor (4) discharges, at which time the MOSFET tube Q1 is turned on and Q2 is turned off; when the battery SOC bat <15%, the battery (5) enters the standby state, and the MOSFET tube Q3 is disconnected; when 15% ≤ SOC bat <25%, the battery (5) is slowly discharged, and the MOSFET tube Q3 is turned on; when the battery SOC bat When the value is ≥25%, the storage battery (5) is discharged, and the MOSFET tube Q3 is turned on.

2. The DC microgrid based on hybrid energy storage according to claim 1 is characterized in that: The storage battery (5), the super capacitor (4), and the MOSFET tube Q3 constitute a hybrid energy storage unit.

3. The DC microgrid based on hybrid energy storage according to claim 2 is characterized in that: The hybrid energy storage unit SOC is set to 5 ranges:

4. The energy management method of the DC microgrid power supply mode based on hybrid energy storage as claimed in claim 1, characterized in that: (1) If the hybrid energy storage distribution power P hess <0, When the supercapacitor SOC sc ≥85%, battery SOC bat ≥85%, at this time, the battery reference control power P is obtained bat_ref , supercapacitor reference control power P sc_ref All are zero, and then, through voltage / current control, the MOSFET tube Q1, Q2 turn-off signal S1 and the MOSFET tube Q3 turn-off signal S7 are obtained; When supercapacitor 75%≤SOC SC <85%, battery 75%≤SOC bat <85%, at this time, the battery reference control power P′ is obtained bat_ref , supercapacitor reference control power P′ sc_ref Then, the voltage / current controller obtains the MOSFET tube Q1 turn-on signal S3, the MOSFET tube Q3 turn-on signal S5, and the hybrid energy storage is slowly charged, where: SOC(t) is the state of charge of the supercapacitor / battery at a certain moment during slow charging; When the supercapacitor SOC SC <75%, supercapacitor SOC SC <75%, at this time, the battery reference control power P is obtained bat_ref , supercapacitor reference control power P sc_ref Then, through voltage / current control, the MOSFET tube Q1 turn-on signal S2 and the MOSFET tube Q3 turn-on signal S6 are obtained, and the hybrid energy storage is charged normally; (2) If the hybrid energy storage distribution power P hess >0, When the supercapacitor SOC SC <15%, battery SOC bat <15%, then the battery reference control power P is obtained bat_ref , supercapacitor reference control power P sc_ref All are zero, and then, the MOSFET tube Q1, Q2 turn-off signal S1 and the MOSFET tube Q3 turn-off signal S7 are obtained through voltage / current control; When supercapacitor 15%≤SOC SC <25%, battery 15%≤SOC bat <25%, then the battery reference control power P′ is obtained bat_ref , supercapacitor reference control power P′ sc_ref Then, the MOSFET tube Q2 turn-on signal S4 and the MOSFET tube Q3 turn-on signal S6 are obtained through voltage / current control, and the super capacitor and the battery are discharged slowly, wherein: SOC(t) is the state of charge of the supercapacitor / battery at a certain moment during slow charging; When the supercapacitor SOC SC >25%, supercapacitor SOC SC >25%, at this time, the battery reference control power P is obtained bat_ref , supercapacitor reference control power P sc_ref Then, the MOSFET tube Q2 turn-on signal S2 and the MOSFET tube Q3 turn-on signal S8 are obtained through the voltage / current controller.

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