Series-parallel modular energy storage system and flexible electric energy routing method thereof

Abstract

The invention provides a series-parallel modular energy storage system and a flexible electric energy routing method thereof, the series-parallel modular energy storage system comprises three phases of series-parallel modular energy storage electric energy routers with identical structures, and each phase of series-parallel modular energy storage electric energy router comprises two hybrid power modules HPM1 and HPM2 with identical structures, one end of the hybrid power module HPM1 and one end of the hybrid power module HPM2 are connected with an alternating current power grid 1 and an alternating current power grid 2 respectively, and the other end of the hybrid power module HPM1 and the other end of the hybrid power module HPM2 are connected to a direct current bus in parallel. According to the hierarchical energy management strategy, an upper layer selects a proper working mode according to an actual power value and executes segmented droop energy management, a lower layer control strategy is respectively borne by different power conversion units according to port distribution conditions, and two layers of control are combined so as to realize autonomous power distribution among different ports; and stable switching of the four working modes is facilitated.

Description

Technical Field

[0001] The present invention relates to an energy storage system, and in particular to a hybrid modular energy storage system and a flexible electric energy routing method thereof. Background Art

[0002] Distributed power integrated energy systems can provide efficient and reliable interfaces for power generation, energy storage and electricity consumption through specific power topology networks and terminal power equipment. With the introduction of the concept of new power systems, various types of distributed interactive energy systems have developed rapidly. As renewable energy is vigorously developed and quickly penetrated into traditional power networks, the power grid is affected by power flow changes and voltage / frequency fluctuations. Therefore, the Flexible Interconnection System (FIS) with power flow management and power quality control functions has received widespread attention. The topology, control strategy and functional implementation of FIS have gradually become research hotspots. In addition to traditional transformer functions, it also provides functions such as AC power quality control, plug-and-play energy ports for low-voltage power units, and fault isolation to improve system reliability. In addition, FIS can realize efficient power collection and scheduling between distributed power grids, renewable energy, local energy storage / consumption, etc.

[0003] FIS needs to have basic isolation and transformation functions. Most existing FIS are based on solid-state transformers or power electronic transformers, and their power routing performance depends largely on the degree of port power decoupling and the flexibility of power paths. Sudden changes in port power and poor local power mobility will pose a great threat to the stability and economy of distributed port smart transformers. Summary of the invention

[0004] The present invention proposes a hybrid modular energy storage system.

[0005] The technical solution for achieving the purpose of the present invention is: a hybrid modular energy storage system, comprising: a three-phase hybrid modular energy storage power router with exactly the same structure, each phase of the hybrid modular energy storage power router comprises: two hybrid power modules HPM1 and HPM2 with exactly the same structure, one end of the hybrid power modules HPM1 and HPM2 are respectively connected to the AC power grid 1 and the AC power grid 2, and the other end of the hybrid power modules HPM1 and HPM2 are connected in parallel to the DC bus.

[0006] Preferably, each hybrid power module includes a distributed power supply unit, a battery energy storage unit, a first H-bridge H pvi 、Second H bridge H bi , the first dual active bridge DAB pvi , the second dual active bridge DAB di , the third dual active bridge DAB bi 、Electrolytic capacitor Cpi1 、Electrolytic capacitor C pi2 ;

[0007] The first H bridge H pvi The positive and negative electrodes of the electrolytic capacitor C pi1 The positive and negative poles, the first dual active bridge DAB pvi , the second dual active bridge DAB di One end of the first dual active bridge DAB pvi The other end of the electrolytic capacitor C pi2 The positive and negative electrodes of the distributed power supply unit are connected; the second dual active bridge DAB di The other port is connected to the electrolytic capacitor C di Connect the positive and negative poles of the low voltage DC bus;

[0008] The first H bridge H pvi The first branch of the AC output terminal is connected to the AC grid 1, and the second branch is connected to the second H bridge H bi The first branch of the AC output terminal is connected; the second H bridge H bi The positive and negative electrodes of the electrolytic capacitor C bi1 The positive and negative poles and the third dual active bridge DAB bi The third dual active bridge DAB bi The other end of the electrolytic capacitor C bi2 The positive and negative electrodes of the battery energy storage unit are connected to the positive and negative electrodes of the battery energy storage unit voltage output terminal; the second H bridge H bi The second branch of the AC output terminal is connected to the AC grid 2

[0009] The present invention also proposes a flexible power routing method for a hybrid modular energy storage system, the specific steps of which are:

[0010] Get the AC grid voltage v g , AC grid current i g , H pvi DC side voltage v dcpi , H bi DC side voltage v dcbi , Photovoltaic output voltage v pvi , Photovoltaic output current i pvi , DC bus voltage v o , DC bus current i o 、Battery voltage v bi , battery current i bi , and calculate the AC grid power P based on the obtained value gi , Photovoltaic output power P pvi , DC bus power P o 、Battery power P bi ;

[0011] According to the relationship between load power, maximum photovoltaic output power, grid power, and battery power, determine the working mode of the hybrid modular energy storage system and calculate the droop coefficient under different working modes;

[0012] Calculate the reference value of the photovoltaic output voltage and the reference value of the AC grid power fed back by the hybrid power module;

[0013] The photovoltaic output voltage reference value v pviref The actual value of the photovoltaic output voltage v pvi The difference is passed through PI controller 1 to obtain the reference value i of the photovoltaic output current. pviref , and then compared with the actual current value i pvi Subtract the phase and obtain the modulated wave signal through the PI controller 2, and the modulated wave signal is modulated by the carrier phase shift modulation to control the first dual active bridge DAB pvi The switching angle is turned on;

[0014] The total DC voltage reference value v dcref With the first H bridge H pvi Actual voltage on DC side v dcpi and the second H-bridge H bi Actual voltage on DC side v dcbi The average value of is subtracted, and after passing through PI controller 3, the third dual active bridge DAB is obtained. bi The current reference value i biref , and then with the third dual active bridge DAB bi The actual value of the current i bi Subtract the phase and obtain the modulated wave signal through the PI controller 4, and the modulated wave signal is modulated by the carrier phase shift modulation to control the third dual active bridge DAB bi The switching angle is turned on;

[0015] The actual value of the DC bus current i oi Multiply by the droop coefficient d i The voltage disturbance Δv is obtained oi , the disturbance value and the DC bus voltage reference value v oref Subtract the difference and the actual value of the DC bus voltage v oi After the difference is made, the reference value i of the DC bus current is obtained through the PI controller 5. oiref , and then compared with the actual current value i oi Subtract the phase and get the modulated wave signal through PI controller 6, which is modulated by carrier phase shift to control the second dual active bridge DAB di The switching angle is turned on;

[0016] Grid voltage v gsi The phase signal θ of the AC power grid is obtained by phase tracking through a phase-locked loop;

[0017] According to the AC power grid phase signal θ, the grid-connected voltage v gsi And grid-connected current i gsi Perform αβ / dq coordinate transformation to obtain the grid-connected voltage v gsi And grid-connected current i gsi The active and reactive components u dsi 、u qsi and dsi 、i qsi ; Voltage active component u dsi Add the reactive component i qsi Multiply the value after the AC grid angular frequency ω and the AC grid inductance L, and then add it to the reference value i of the current active component dsiref with i dsi After subtraction, the value of the PI controller is subtracted to obtain the first H bridge pvi AC terminal voltage u ab_di ;

[0018] Voltage reactive component u qsi With the active component of current i dsi The value after multiplying by ωL is subtracted and then compared with the reference value i of the reactive component of the current. qsiref with i qsi After subtraction, the value of the PI controller is subtracted to obtain the second H bridge H bi AC terminal voltage u ab_qi ;

[0019] First H Bridge pvi AC terminal voltage u ab_di After multiplying by 1 / 2, we get u ab_pid As the first H bridge H pvi The d-axis component for dq / αβ coordinate transformation and the second H-bridge H bi The q-axis component of the dq / αβ coordinate transformation is taken as the second H bridge H bi AC terminal voltage u ab_qi After multiplying by 1 / 2, we get u ab_biq As the second H bridge H bi The d-axis component of the dq / αβ coordinate transformation and the first H bridge H pvi The q-axis component of the dq / αβ coordinate transformation is used to transform the first H bridge according to the obtained component. pvi Second H Bridge H bi Perform dq / αβ coordinate transformation to output voltage modulation wave signal u ab_pi 、u ab_di , the voltage modulation wave signal is modulated by PWM to control the first H bridge H pvi and the second H-bridge H bi The switching angle of

[0020] Compared with the prior art, the present invention has the following significant advantages: the present invention combines battery energy storage (ES), distributed power source (PV), low-voltage DC power output and AC grid connection to form a modular hybrid power port flexible interconnection system. Each module has the same structure, with various types of ports such as medium-voltage AC, medium-voltage DC and low-voltage DC. The low-voltage DC port of the module presents a distributed structure, accesses power generation, energy storage and load terminals, and has higher hardware flexibility than the traditional structure; the AC side of the module directly exchanges power with the medium-voltage distribution network through a multi-level power conversion stage, and the power generation unit and the load unit directly exchange power through the medium-voltage DC bus, thereby effectively reducing losses and improving operating efficiency; the hierarchical energy management strategy based on segmented droop proposed in the present invention, the upper layer selects the appropriate working mode according to the actual power value and performs segmented droop energy management, and the lower layer control strategy is undertaken by different power conversion units according to the port distribution. The two layers of control are combined to realize autonomous power distribution between different ports, which is conducive to the smooth switching of the four working modes proposed.

[0021] The present invention is described in further detail below in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a topological diagram of a hybrid modular energy storage system.

[0023] Figure 2 It is a schematic diagram of the overall hierarchical control structure of the hybrid modular energy storage system.

[0024] Figure 3 This is a diagram of the four operating modes of the flexible interconnection system.

[0025] Figure 4 It is a block diagram of the calculation of the expected value of the output voltage.

[0026] Figure 5 It is a schematic diagram of the VP segmented droop curve.

[0027] Figure 6 Yes H pvi and H bi Power allocation control diagram (a)i di and i qi Control loop (b) H pvi and H bi control loop.

[0028] Figure 7 It's DAB pvi Schematic diagram of the phase-shift control loop.

[0029] Figure 8 It's DAB bi Schematic diagram of the control circuit.

[0030] Fig. 9 It's DAB di Schematic diagram of the control circuit.

[0031] Fig.10 The following is a schematic diagram of the curves of the power and DC voltage of each unit changing with the load in modes 1 and 2: (a) P L (pu); (b)P pvi (pu)(i=1,2…,4); (c)P gi (pu); (d)P bi (pu); (e)v o ; (f) HPM1 DC link voltage; (g) HPM2 DC link voltage; (h) HPM3 DC link voltage; (i) HPM4 DC link voltage. DETAILED DESCRIPTION

[0032] A hybrid modular energy storage system includes: a three-phase hybrid modular energy storage power router with completely identical structures, each phase of the hybrid modular energy storage power router includes: two hybrid power modules HPM1 and HPM2 with completely identical structures, one end of the hybrid power modules HPM1 and HPM2 is respectively connected to an AC power grid 1 and an AC power grid 2, and the other end of the hybrid power modules HPM1 and HPM2 is connected in parallel to a DC bus.

[0033] In a further embodiment, each hybrid power module includes a distributed power supply unit, a battery energy storage unit, a first H-bridge H pvi 、Second H bridge H bi , the first dual active bridge DAB pvi , the second dual active bridge DAB di , the third dual active bridge DAB bi ;

[0034] The first H bridge H pvi The positive and negative electrodes of the electrolytic capacitor C pi1 The positive and negative poles, the first dual active bridge DAB pvi , the second dual active bridge DAB di One of the ports is connected; the first dual active bridge DAB pvi The other port is connected to the electrolytic capacitor C pi2 The positive and negative electrodes of the distributed power supply unit are connected to the positive and negative electrodes of the distributed power supply unit output terminal. The second dual active bridge DAB di The other port is connected to the electrolytic capacitor C di Connect the positive and negative poles of the low voltage DC bus;

[0035] The first H bridge H pvi The first branch of the AC output terminal is connected to the AC grid, and the second branch is connected to the second H bridge Hbi The AC output terminal of the second H bridge H bi The positive and negative electrodes of the electrolytic capacitor C bi1 The positive and negative poles and the third dual active bridge DAB bi One of the ports is connected; the third dual active bridge DAB bi The other port is connected to the electrolytic capacitor C bi2 The positive and negative electrodes of the battery energy storage unit are connected to the positive and negative electrodes of the battery energy storage unit voltage output terminal; the first H bridge H pvi With the second H bridge H bi The other AC output end is connected to the medium voltage AC grid 1 and the medium voltage AC grid 2 respectively.

[0036] The first H bridge H pvi Including H pvi Switch tube No. 1 pi1 , H pvi Switch tube No. 2 S pi2 , H pvi Switch tube S pi3 , H pvi Switch tube S pi4 ;

[0037] The first dual active bridge DAB pvi DAB included pvi Resonant inductor L pi 、DAB pvi Transformer pi 、DAB pvi Input side capacitor C pi1 、DAB pvi Output side capacitor C pi2 、DAB pvi Switch tube No. 1 pi5 、DAB pvi Switch tube No. 2 S pi6 、DAB pvi Switch tube S pi7 、DAB pvi Switch tube S pi8 、DAB pvi No. 5 switch tube S pi9 、DAB pvi No. 6 switch tube S pi10 、DAB pvi No. 7 switch tube S pi11 、DAB pvi No. 8 switch tube S pi12 , distributed power supply units, battery energy storage units;

[0038] Second dual active bridge DAB di DAB included di Resonant inductor Ldi 、DAB di Transformer di 、DAB pvi Output side capacitor C di 、DAB di Switch tube No. 1 di1 、DAB di Switch tube No. 2 S di2 、DAB di Switch tube S di3 、DAB di Switch tube S di4 、DAB di No. 5 switch tube S di5 、DAB di No. 6 switch tube S di6 、DAB di No. 7 switch tube S di7 、DAB di No. 8 switch tube S di8 . The second H bridge H bi , H bi Switch tube No. 1 bi1 , H bi Switch tube No. 2 S bi2 , H bi Switch tube S bi3 , H bi Switch tube S bi4 .

[0039] Second H bridge H bi Including H bi Switch tube No. 1 bi1 , H bi Switch tube No. 2 S bi2 , H bi Switch tube S bi3 , H bi Switch tube S bi4 , the third dual active bridge DAB bi 、DAB bi Resonant inductor L bi 、DAB bi Transformer bi 、DAB bi Input side capacitor C bi1 、DAB bi Output side capacitor C bi2 、DAB bi Switch tube No. 1 bi5 、DAB bi Switch tube No. 2 S bi6 、DAB bi Switch tube S bi7 、DAB bi Switch tube Sbi8 、DAB bi No. 5 switch tube S bi9 、DAB bi No. 6 switch tube S bi10 、DAB bi No. 7 switch tube S bi11 、DAB bi No. 8 switch tube S bi12 .

[0040] The hybrid modular energy storage system of the present invention has various types of ports, including medium-voltage AC, medium-voltage DC and low-voltage DC. The low-voltage DC port of the module presents a distributed structure and is connected to the power generation, energy storage and load terminals, which has higher hardware flexibility than the traditional structure; the AC side of the module directly exchanges power with the medium-voltage distribution network through a multi-level power conversion stage, and the power generation unit and the load unit directly exchange power through the medium-voltage DC bus, thereby effectively reducing losses and improving operating efficiency.

[0041] A flexible power routing method for a hybrid modular energy storage system. The energy management strategy is divided into two layers: upper and lower. The upper layer calculates the actual power value based on the measured voltage and current, selects the appropriate working mode based on the actual power and formula, and performs segmented droop energy management to transmit the generated photovoltaic power reference value, grid power reference value, and segmented droop coefficient to the lower layer. The lower layer control strategy generates an on-off signal based on the reference value of the top layer strategy and sends it to each H-bridge and DAB bridge switch tube. The specific steps are as follows:

[0042] The specific steps of upper-level control are as follows:

[0043] 1) For AC grid voltage v g , AC grid current i g , H pvi DC side voltage v dcpi , H bi DC side voltage v dcbi , Photovoltaic output voltage v pvi , Photovoltaic output current i pvi , DC bus voltage v o , DC bus current i o 、Battery voltage v bi , battery current i bi Measure the same electrical value.

[0044] 2) Calculate the AC grid power P based on the measured value gi , Photovoltaic output power P pvi , DC bus power P o 、Battery power P bi .

[0045] P gi =v g ig cosθ,P pvi =v pvi i pvi ,P o =v o i o ,P bi =v bi i bi

[0046] 3) According to the load and battery energy storage charging and discharging conditions, determine the basic operating mode and calculate the droop coefficient under different modes:

[0047] When the relationship between load power, maximum photovoltaic output power, grid power, and battery power satisfies formula (1), the system operates in mode 1. At this time, the load is light, and the distributed power source injects power into the AC grid, load, and energy storage battery at the same time. The AC grid absorbs active power, and the battery is in a charging state. L is the load power, P pvimax For HPM i The maximum output power of photovoltaic power, P chiref For HPM i Medium battery charging power reference, P gaimax For HPM i The maximum power that can be fed back to the AC grid.

[0048]

[0049] When the power relationship satisfies formula (2), the system operates in mode 2. At this time, the power provided by photovoltaic power can only meet the load demand, the distributed power supply directly supplies power to the load, and the battery is charged by the distributed power supply and the AC grid. Photovoltaic power provides power to the load and the battery, while the AC grid only provides power to the battery. gdimax For HPM i The maximum power that can be drawn from the AC grid.

[0050]

[0051] When the power relationship satisfies formula (3), the system operates in mode 3. At this time, the load increases, and the photovoltaic power generation is insufficient to provide the power required by the load. The distributed power supply and the AC grid both supply power to the load, and the AC grid charges the energy storage battery.

[0052]

[0053] When the power relationship satisfies formula (4), it operates in mode 4. At this time, the load is overloaded or the solar power is insufficient. The photovoltaic, AC grid and battery jointly supply power to the load. The grid provides active power and the battery is in a discharging state.

[0054]

[0055] 4) Photovoltaic output voltage reference value v pviref According to the battery state of charge and battery charging curve, the battery charging power reference P is obtained. chiref , the reference and actual power P bi The difference is calculated and the optimal voltage increment Δv is obtained after the difference passes through the proportional integral controller. MPP , whose lower limit is zero. If the battery power is less than the reference value of the battery charging power, the controller outputs Δv MPP =0, the maximum power point tracking (MPPT) is enabled after logical judgment, otherwise the maximum power point tracking (MPPT) is disabled. pviref Calculated by formula (5)

[0056] v pviref =v MPP -Δv MPP (5)

[0057] HPM i Feedback AC grid power reference value P giref The calculation based on power conservation is as follows:

[0058]

[0059] like Figure 5 As shown, taking the two hybrid power modules HPM1 and HPM2 of phase A as an example, segmented droop control is adopted according to different control mode switching to determine the segmented droop coefficient corresponding to each mode.

[0060] Assume that the maximum photovoltaic power generation power P in HPM1 pv1max Less than the maximum photovoltaic power generation power P in HPM2 pv2max , the maximum absorbed (or provided) power of AC grid 1 is equal to the maximum absorbed (or provided) power of AC grid 2. Under no-load conditions, HPM1 operates at A1 of droop curve 1 and A2 of droop curve 3, while HPM2 operates at A1 of curve 2 and A4 of curve 4. The power transmitted from photovoltaic to AC grid by each HPM is P gamax The battery charging powers of the two modules are P ch1 and P ch2 .

[0061] When the load power consumption increases to P L1 When the DC port operating point of HPM1 and HPM2 moves to B1 and B3, the AC port operating point moves to B2 and B4 accordingly. gamax Absorbing electric energy, HPM1 works at the maximum power point of the distributed power source, and the distributed power source emits power P pv1max . HPMi The droop coefficient d i Determined by the following formula

[0062]

[0063] Among them, P pv_max is the larger of the two distributed power sources. L2 When the DC port operating point of HPM1 and HPM2 moves to C1 and C3, the AC grid absorption power remains at P gamax , the operating point moves to C2 and C4. In the B1-C1 interval, the increase in load power is provided by the distributed power in HPM2 until C3 reaches its maximum power point. At points C1 and C3, the power generated by the distributed power of the two modules is P pv1max and P pv2max . HPM i The droop coefficient d i Determined by the following formula

[0064]

[0065]

[0066] When the load power increases to P L3 , the DC port operating points of HPM1 and HPM2 move to D1 and D3. In the C1-D1 (or C3-D3) operating range, the increase in load power will limit the power injected into the AC grid, that is, the power fed back to the AC grid by HPM1 and HPM2 is reduced, and the total power of the distributed power source reaches the limit and is insufficient to maintain the AC grid power. Therefore, the AC port curves of the two modules turn at the same time, and the operating points move to D2 and D4.

[0067] In the above four cases, the power flow direction of all ports does not change, and the two HPMs always work in mode 1. L4 When the power output of the distributed generation is less than the sum of the load consumption and the battery charging power, the grid needs to participate in providing the remaining power. The working points of HPM1 and HPM2 become E2 and E4, working in mode 2.

[0068] When the load power increases to P L5 When the maximum power of the distributed power source is less than the load power, the AC grid provides power to the load and the battery at the same time. At this time, HPM1 and HPM2 work at points F1 and F3, and the output power of AC grid 1 and AC grid 2 reaches the maximum value P gdmax . HPM i The droop coefficient d i Determined by the following formula

[0069]

[0070]

[0071] If the load power continues to increase to P L6 When the battery charging power is reduced to 0, the DC ports of HPM1 and HPM2 operate at points G1 and G3, and the AC ports operate at points G2 and G4, respectively. The working mode of the two modules is mode 3.

[0072] When the load power increases to P L7 When the distributed power supply, AC grid and battery supply power to the load at the same time, the DC ports of HPM1 and HPM2 work at H1 and H3, and the working point of the AC port changes to H2 and H4. At this time, the battery discharge power reaches the upper limit, and each HPM module works in mode 4. i The droop coefficient d i Determined by the following formula

[0073]

[0074]

[0075] Lower cascade H-bridge and dual active bridge DAB control:

[0076] like Figure 7 As shown, the photovoltaic output voltage reference value v pviref With the actual value v pvi The difference is passed through PI controller 1 to obtain the reference value i of the photovoltaic output current. pviref , and then compared with the actual current value i pvi Subtraction is performed through PI controller 2 to obtain a modulated wave signal, which is then modulated by carrier phase shift modulation to control DAB pvi The switching angle is turned on.

[0077] like Figure 8 As shown, the total DC voltage reference value v dcref With H pvi Actual voltage on DC side v dcpi and H bi Actual voltage on DC side v dcbi The average value of is subtracted and DAB is obtained after passing through PI controller 1 bi The current reference value i biref , and then compared with the actual current value i bi Subtraction is performed through PI controller 2 to obtain a modulated wave signal, which is then modulated by carrier phase shift modulation to control DAB bi The switching angle is turned on.

[0078] like Fig. 9As shown, the actual value of the DC bus current i oi Multiply by the droop coefficient d i The voltage disturbance Δv is obtained oi , disturbance and DC bus voltage v oref Subtract to get the output voltage reference, the reference value and the actual value v oi The difference is passed through PI controller 1 to obtain the reference value i of the DC bus current oiref , and then compared with the actual current value i oi Subtraction is performed through PI controller 2 to obtain a modulated wave signal, which is then modulated by carrier phase shift modulation to control DAB di The switching angle is turned on.

[0079] like Figure 6 As shown, the grid voltage v gsi The phase is tracked by the phase-locked loop to obtain the AC power grid phase signal θ. Use θ for v gsi And grid-connected current i gsi Perform αβ / dq coordinate transformation to obtain v gsi and gsi The active and reactive components u dsi 、u qsi and dsi 、i qsi . Voltage active component u dsi The reactive component of current i qsi The value multiplied by ωL is added to the reference value i of the active component of the current. dsiref with i dsi After subtraction, the value of the PI controller is subtracted to obtain the H bridge H pvi AC terminal voltage u ab_di .

[0080] Voltage reactive component u qsi With the active component of current i dsi The value after multiplying by ωL is subtracted and then compared with the reference value i of the reactive component of the current. qsiref with i qsi After subtraction, the value of the PI controller is subtracted to obtain the H bridge H bi AC terminal voltage u ab_q i.

[0081] Take u ab_di After multiplying by 1 / 2, we get u ab_pid As H pvi The d-axis component and H for dq / αβ coordinate transformation bi The q-axis component of the dq / αβ coordinate transformation is taken as u ab_qi After multiplying by 1 / 2, we get u ab_biq As H bi The d-axis component and H for dq / αβ coordinate transformationpvi The q-axis component of the dq / αβ coordinate transformation is respectively transformed into the output voltage modulation wave signal u ab_pi 、u ab_di , PWM modulation is used to control H pvi and H bi The switching angle is turned on.

[0082] Example 1

[0083] The simulation parameters are designed as follows: AC voltage v g is 2200V; DC link voltage v dc is 4000V; DC bus voltage v o is 500V; the MPPT power P of the 1a-phase photovoltaic power grid pv1max is 49000W; the MPPT power P of the 1b phase photovoltaic power of the AC grid pv2max 50000W; AC grid 1c phase photovoltaic MPPT power P pv3max is 44000W; the MPPT power P of the 2a / b / c phase photovoltaic power of the AC grid is pv4max is 54000W; the maximum power P that the AC grid can absorb from photovoltaic gamax / The maximum power P that AC grid 1 can provide gd1max / The maximum power P that AC grid 2 can provide gd2max is 20000W; load power base value P L_basw 18000W; photovoltaic power base value P pv_base is 54000W; AC grid power reference value P g_base 20000W; battery power base value P bi_base It is 16000W.

[0084] Working condition 1: P L (pu) = 35.5%. chiref (i=1,2…,4) is 1p.u., the power P absorbed by the AC grid from the system gi (i=1,2…,4) is -1p.u. By setting the droop coefficients of phases A, B, C of AC grid 1 and AC grid 2 to 1.31, 1.27, 2.14, and 1, respectively, the power provided by the hybrid power module HPM to the load is 5.33%, 5.5%, 3.22%, and 7%, respectively. The photovoltaic output power P of HPM1 pv1 (pu) is 84.9%, and the photovoltaic output power P of HPM2 pv2 (pu) is 85.1%, and the photovoltaic output power P of HPM3 pv3 (pu) is 77.1%, and the photovoltaic output power P of HPM4 pv4(pu) is 89.3% (see Fig.10 (b)). At this time, HPM is running in mode 1 and not running in MPP. gi With P chi stabilized at its reference value, such as Fig.10 (c) and (d). 1-3 They are the power modules of phases A, B, and C in the AC power grid 1, and HPM4 is the power module in the AC power grid 2.

[0085] Working condition 2: P L (pu) = 73.8%. chiref (i=1,2…,4) is 1p.u., the AC grid absorbs active power P gi (pu)(i=1,2…,4) is -65%. The droop coefficients are set to 1.24, 1.19, 1.65 and 1 respectively. After the load increases, the power provided by HPM to the load is 11.1%, 11.6%, 8.5% and 13.7% respectively. Photovoltaic output power P pvi (pu)(i=1,2…,4) increased to 93.2%, 95.6%, 83.9% and 100% respectively. All HPM PVs are operated at MPP. Fig.10 (e) As shown, v o The DC side voltage decreases slightly and stabilizes at the reference value.

[0086] Working condition three: P L (pu) = 151.4%. chiref (i=1,2…,4)(pu) does not change. The AC grid starts to generate power, P gi (pu)(i=1,2…4) is 52.5%. The droop coefficients are set to 1.11, 1.09, 1.26 and 1 respectively. At this time, the HPM operates in mode 2.

[0087] Working condition 4: P L (pu) = 212.9%. The maximum power provided by AC grids 1 and 2 is 107.1% and 108.5% respectively. The droop coefficients are 1.09, 1.07, 1.18 and 1 respectively, and all photovoltaic units operate at MPPT. Battery charging power P chi (pu)(i=1,2…,4) is 49.4%, such as Fig.10 (d) At this time, all HPMs operate in mode 3.

[0088] Working condition 5: P L (pu) = 267.3%. The maximum power provided by AC grid 1 and 2 is 107.1% and 108.5% respectively. The total power provided by the AC grid and the photovoltaic unit is less than the load power PL , so the battery needs to provide power to the load, P chi (pu)(i=1,2…,4) is -56.3%. The droop coefficients are 1.07, 1.06, 1.14 and 1 respectively, and the PV unit operates at MPP. At this time, all HPMs operate in mode 4.

[0089] From working condition 1 to working condition 5, as the load changes, the DC bus voltage v o The voltage of each HPM DC link is slightly reduced, and its range is 464V~494.8V. dci All are stable at the reference value.

Claims

1. A hybrid modular energy storage system, characterized in that: include: A three-phase hybrid modular energy storage power router with exactly the same structure, each phase of the hybrid modular energy storage power router includes: two hybrid power modules HPM1 and HPM2 with exactly the same structure, one end of the hybrid power modules HPM1 and HPM2 is connected to the AC power grid 1 and the AC power grid 2 respectively, and the other end of the hybrid power modules HPM1 and HPM2 is connected in parallel to the DC bus.

2. The hybrid modular energy storage system according to claim 1, characterized in that: Each hybrid power module includes a distributed power supply unit, a battery energy storage unit, a first H-bridge H pvi 、Second H bridge H bi , the first dual active bridge DAB pvi , the second dual active bridge DAB di , the third dual active bridge DAB bi 、Electrolytic capacitor C pi1 、Electrolytic capacitor C pi2 ; The first H bridge H pvi The positive and negative electrodes of the electrolytic capacitor C pi1 The positive and negative poles, the first dual active bridge DAB pvi , the second dual active bridge DAB di One end of the first dual active bridge DAB pvi The other end of the electrolytic capacitor C pi2 The positive and negative electrodes of the distributed power supply unit are connected; the second dual active bridge DAB di The other port is connected to the electrolytic capacitor C di Connect the positive and negative poles of the low voltage DC bus; The first H bridge H pvi The first branch of the AC output terminal is connected to the AC grid 1, and the second branch is connected to the second H bridge H bi The first branch of the AC output terminal is connected; the second H bridge H bi The positive and negative electrodes of the electrolytic capacitor C bi1 The positive and negative poles and the third dual active bridge DAB bi The third dual active bridge DAB bi The other end of the electrolytic capacitor C bi2 The positive and negative electrodes of the battery energy storage unit are connected to the positive and negative electrodes of the battery energy storage unit voltage output terminal; the second H bridge H bi The second branch of the AC output end is connected to the AC power grid 2.

3. A flexible power routing method of the system as claimed in claim 1 or 2, characterized in that: The specific steps are: Get the AC grid voltage v g , AC grid current i g , H pvi DC side voltage v dcpi , H bi DC side voltage v dcbi , Photovoltaic output voltage v pvi , Photovoltaic output current i pvi , DC bus voltage v o , DC bus current i o 、Battery voltage v bi , battery current i bi , and calculate the AC grid power P based on the obtained value gi , Photovoltaic output power P pvi , DC bus power P o 、Battery power P bi ; According to the relationship between load power, maximum photovoltaic output power, grid power, and battery power, determine the working mode of the hybrid modular energy storage system and calculate the droop coefficient under different working modes; Calculate the reference value of the photovoltaic output voltage and the reference value of the AC grid power fed back by the hybrid power module; The photovoltaic output voltage reference value v pviref The actual value of the photovoltaic output voltage v pvi The difference is passed through PI controller 1 to obtain the reference value i of the photovoltaic output current. pviref , and then compared with the actual current value i pvi Subtract the phase and obtain the modulated wave signal through the PI controller 2, and the modulated wave signal is modulated by the carrier phase shift modulation to control the first dual active bridge DAB pvi The switching angle is turned on; The total DC voltage reference value v dcref With the first H bridge H pvi Actual voltage on DC side v dcpi and the second H-bridge H bi Actual voltage on DC side v dcbi The average value of is subtracted, and after passing through PI controller 3, the third dual active bridge DAB is obtained. bi The current reference value i biref , and then with the third dual active bridge DAB bi The actual value of the current i bi Subtract the phase and obtain the modulated wave signal through the PI controller 4, and the modulated wave signal is modulated by the carrier phase shift modulation to control the third dual active bridge DAB bi The switching angle is turned on; The actual value of the DC bus current i oi Multiply by the droop coefficient d i The voltage disturbance Δv is obtained oi , the disturbance value and the DC bus voltage reference value v oref Subtract the difference and the actual value of the DC bus voltage v oi After the difference is made, the reference value i of the DC bus current is obtained through the PI controller 5. oiref , and then compared with the actual current value i oi Subtract the phase and get the modulated wave signal through PI controller 6, which is modulated by carrier phase shift to control the second dual active bridge DAB di The switching angle is turned on; Grid voltage v gsi The phase signal θ of the AC power grid is obtained by phase tracking through a phase-locked loop; According to the AC power grid phase signal θ, the grid voltage v gsi And grid-connected current i gsi Perform αβ / dq coordinate transformation to obtain the grid-connected voltage v gsi And grid-connected current i gsi The active and reactive components u dsi 、u qsi and dsi 、i qsi ; Voltage active component u dsi Add the reactive component i qsi Multiply the value after the AC grid angular frequency ω and the AC grid inductance L, and then add it to the reference value i of the current active component dsiref with i dsi After subtraction, the value of the PI controller is subtracted to obtain the first H bridge pvi AC terminal voltage u ab_di ; Voltage reactive component u qsi With the active component of current i dsi The value after multiplying by ωL is subtracted from the reference value i of the reactive component of the current. qsiref with i qsi After subtraction, the value of the PI controller is subtracted to obtain the second H bridge H bi AC terminal voltage u ab_qi ; First H Bridge pvi AC terminal voltage u ab_di After multiplying by 1 / 2, we get u ab_pid As the first H bridge H pvi The d-axis component for dq / αβ coordinate transformation and the second H-bridge H bi The q-axis component of the dq / αβ coordinate transformation is taken as the second H bridge H bi AC terminal voltage u ab_qi After multiplying by 1 / 2, we get u ab_biq As the second H bridge H bi The d-axis component of the dq / αβ coordinate transformation and the first H bridge H pvi The q-axis component of the dq / αβ coordinate transformation is used to transform the first H bridge according to the obtained component. pvi Second H Bridge H bi Perform dq / αβ coordinate transformation to output voltage modulation wave signal u ab_pi 、u ab_di , the voltage modulation wave signal is modulated by PWM to control the first H bridge H pvi and the second H-bridge H bi The switching angle is turned on.

4. The flexible power routing method according to claim 3, characterized in that: Calculate the AC grid power P gi , Photovoltaic output power P pvi , DC bus power P o 、Battery power P bi The specific formula is: P gi =v g i g cosθ,P pvi =v pvi i pvi ,P o =v o i o ,P bi =v bi i bi Where θ is the phase signal of the AC power grid.

5. The flexible power routing method according to claim 3, characterized in that: When the relationship between load power, maximum photovoltaic output power, grid power, and battery power meets the following conditions: Where P L is the load power, P pvimax Hybrid Power Module (HPM) i The maximum output power of photovoltaic power, P chiref For HPM i Medium battery charging power reference, P gaimax For AC grid from hybrid power module HPM i The maximum power that can be absorbed; The hybrid modular energy storage system is in the first working mode, at which time the load is light, the distributed power source injects power into the AC grid, the load and the energy storage battery at the same time, the AC grid absorbs active power, and the battery is in a charging state; When the relationship between load power, maximum photovoltaic output power, grid power, and battery power meets the following conditions: The hybrid modular energy storage system is in the second working mode. At this time, the power provided by photovoltaic can only meet the load demand. The distributed power supply directly supplies power to the load, and the battery is charged by the distributed power supply and the AC grid. gdimax Hybrid Power Module (HPM) i The maximum power that can be absorbed from the AC grid; When the relationship between load power, maximum photovoltaic output power, grid power, and battery power meets the following conditions: The hybrid modular energy storage system is in the third working mode. At this time, the load increases, and the photovoltaic power generation is insufficient to provide the power required by the load. The distributed power supply and the AC power grid both supply power to the load, and the AC power grid charges the energy storage battery. When the relationship between load power, maximum photovoltaic output power, grid power, and battery power meets the following conditions: The hybrid modular energy storage system is in the fourth working mode. At this time, the load is overloaded or the solar power is insufficient. The photovoltaic, AC power grid and battery jointly supply power to the load. The grid provides active power and the battery is in a discharging state.

6. The flexible power routing method according to claim 5, characterized in that: When the hybrid modular energy storage system is in the first working mode, the HPM i The droop coefficient d i The specific determination formula is: Where P pv_max is the larger of the two HPMs’ maximum photovoltaic output power, and i represents the i-th HPM.

7. The flexible power routing method according to claim 5, characterized in that: When the hybrid modular energy storage system is in the second working mode, the specific determination formulas of the droop coefficients d1 and d2 of HPM1 and HPM2 are: Where P gi_d Indicates HPM i Power absorbed from the AC grid, P pv1max Indicates the maximum photovoltaic output power of HPM1, P pv_max The larger of the two HPM maximum photovoltaic output powers.

8. The flexible power routing method according to claim 5, characterized in that: When the hybrid modular energy storage system is in the third working mode, the specific formula for determining the droop coefficients of HPM1 and HPM2 is: Where P gi_d Indicates HPM i Power absorbed from the AC grid, P pv_max is the larger of the two HPMs’ maximum photovoltaic output powers, P pv1max Indicates the maximum photovoltaic output power of HPM1.

9. The flexible power routing method according to claim 5, characterized in that: When the hybrid modular energy storage system is in the fourth working mode, the specific formula for determining the droop coefficients of HPM1 and HPM2 is: Where P bi Indicates HPM i The battery power, P gdimax Indicates the maximum power generated by the AC power grid, P pv_max is the larger of the two HPMs’ maximum photovoltaic output powers, P pv1max Indicates the maximum photovoltaic output power of HPM1.

10. The flexible power routing method according to claim 3, characterized in that: Photovoltaic output voltage reference value v pviref And the reference value P of the AC grid power fed back by the hybrid power module giref The specific calculation formula is: v pviref =v MPP -Δv MPP In the formula, v MPP Indicates the photovoltaic voltage when the photovoltaic is running at MPPT, Δv MPP is the optimal voltage increment across the photovoltaic, P chiref is the battery charging power reference, P L is the load power, P pvi is the photovoltaic output power, Among them, the battery charging power reference P chiref According to the battery state of charge and battery charging curve, the reference and actual power P bi The difference is calculated and the optimal voltage increment Δv is obtained after the difference passes through the proportional integral controller. MPP , whose lower limit is zero. If the battery power is less than the reference value of the battery charging power, the controller outputs Δv MPP =0.

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