Photovoltaic utilization rate-based improved control method for optical storage DC distribution network

Abstract

The invention provides a photovoltaic utilization rate-based improved control method for an optical storage DC distribution network, and the method comprises the following steps: S1, determining the topological structure of a photovoltaic DC distribution network which comprises a photovoltaic unit, an energy storage unit, a DC load unit and two VSC grid-connected units, the input ends of the two VSC grid-connected units are connected with an alternating current power grid, and the output ends of the two VSC grid-connected units are connected to a direct current bus; the energy storage unit, the DC load unit and the photovoltaic unit are connected with the DC bus. S2, calculating the average power of a VSC grid-connected unit in the photovoltaic DC distribution network; s3, determining virtual compensation impedance based on the average power; s4, determining the photovoltaic utilization rate of the photovoltaic DC distribution network; and S5, constructing a droop control equation based on the virtual compensation impedance and the photovoltaic utilization rate, and controlling the photovoltaic DC distribution network to work based on the droop control equation.

Description

Technical Field

[0001] The present invention relates to a photovoltaic-storage direct current distribution network control method, and in particular to an improved photovoltaic-storage direct current distribution network control method based on photovoltaic utilization rate. Background Art

[0002] As the utilization rate of distributed energy continues to increase, DC distribution networks have attracted widespread attention due to their efficient distributed energy and DC load access capabilities and their ability to connect to traditional AC power grids to form multi-terminal power grids. Droop control is often used between source converters in photovoltaic and energy storage DC distribution networks to achieve voltage and power coordination control, but traditional droop control has a contradiction between power distribution accuracy and voltage deviation.

[0003] In the prior art, the following three solutions are proposed to solve the above problems: one is to improve the droop coefficient and realize the accurate distribution of power of each source load by correcting the droop coefficient; the second is to compensate the droop intercept to compensate for the steady-state deviation of DC voltage; the third is a hybrid improved droop control based on the first and second methods. However, the above control methods still cannot effectively solve the contradiction between power distribution accuracy and voltage deviation. This is because the disturbance is not fixed, but changes at any time, and the above cannot adapt to different disturbance requirements.

[0004] Therefore, in order to solve the above technical problems, it is urgent to propose a new technical means. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide an improved control method for a photovoltaic-storage DC distribution network based on photovoltaic utilization. Based on the average power value of each line of the VSC grid-connected unit and based on a PI controller, the output power tracks the average power, and the difference is used as a virtual impedance compensation droop coefficient, so that the droop coefficient of the source with a smaller original power sharing is adjusted to a smaller one, and it bears more load and gradually approaches the average value, thereby achieving an improvement in power distribution accuracy; while improving the power distribution accuracy of each source load of the photovoltaic-storage DC distribution network, the DC voltage steady-state deviation is reduced, and the photovoltaic utilization rate is also taken into account, so that the photovoltaic utilization rate is improved, the system voltage steady-state deviation under different disturbance conditions is smaller and the power distribution accuracy is higher, and the DC voltage steady-state quality is effectively improved.

[0006] The present invention provides a photovoltaic energy storage DC distribution network improvement control method based on photovoltaic utilization, comprising the following steps:

[0007] S1. Determine the topological structure of the photovoltaic DC distribution network, wherein the photovoltaic DC distribution network includes a photovoltaic unit, an energy storage unit, a DC load unit and a VSC grid-connected unit, wherein there are two VSC grid-connected units, the input ends of the two VSC grid-connected units are connected to the AC grid, and the output ends of the two VSC grid-connected units are connected to the DC bus; the energy storage unit, the DC load unit and the photovoltaic unit are all connected to the DC bus;

[0008] S2. Calculate the average power of the VSC grid-connected unit in the photovoltaic DC distribution network;

[0009] S3. Determine the virtual compensation impedance based on the average power;

[0010] S4. Determine the photovoltaic utilization rate of the photovoltaic DC distribution network;

[0011] S5. Construct a droop control equation based on the virtual compensation impedance and the photovoltaic utilization rate, and control the operation of the photovoltaic DC distribution network based on the droop control equation.

[0012] Further, determining the virtual compensation impedance based on the average power specifically includes:

[0013] The VSC grid-connected unit includes at least two grid-connected loops, each of which includes a VSC converter and an LRC circuit, wherein the LRC circuit includes a capacitor C g , resistor R l And the inductor L l The input end of the VSC converter is connected to the AC grid, and the positive output end of the VSC converter is connected to the AC grid through the capacitor C g Connected to the negative DC bus, the positive output of the VSC converter is connected to the negative DC bus through the resistor R l and inductor L l After being connected in series, they are connected to the positive DC bus;

[0014] The output power of each grid-connected circuit of the VSC grid-connected unit is tracked to the average power by using a PI controller;

[0015]

[0016] Where: Δr i is the virtual compensation impedance; α is the adjustment coefficient of the virtual compensation impedance; k pd , k id are the proportional coefficient and integral coefficient of the virtual compensation impedance PI controller, P dci is the output power of the i-th grid-connected circuit, i=1,2,…,n; P dci is the average power of the VSC grid-connected unit.

[0017] Furthermore, the photovoltaic utilization rate of the photovoltaic DC distribution network is determined to include:

[0018]

[0019] Among them: F pv (t) is the photovoltaic utilization rate, P pv (t) is the photovoltaic output power at time t, P pvmax is the maximum photovoltaic output power.

[0020] Furthermore, the improved droop control equation based on the virtual compensation impedance and photovoltaic utilization rate specifically includes:

[0021]

[0022] Where: R d is the droop coefficient, P gdc is the actual output power of the VSC converter DC side; is the reference value of the DC side output power of the VSC converter, is the reference value of the DC side output voltage of the VSC converter, u dc is the actual output voltage value of the DC side of the VSC converter, and g is the photovoltaic regulation coefficient.

[0023] Furthermore, the photovoltaic regulation coefficient g is determined as follows:

[0024]

[0025] Among them: U max , U min are the maximum and minimum values ​​of DC voltage respectively, is the rated output power of the photovoltaic power plant.

[0026] Furthermore, the photovoltaic unit includes a photovoltaic array, a Boost converter and an LRC circuit, wherein the LRC circuit includes a capacitor C pv , resistor R lpv And the inductor L lpv The input of the Boost converter is connected to the output of the photovoltaic array, and the positive output of the Boost converter is connected to the output of the photovoltaic array through the capacitor C pv Connected to the negative DC bus, the positive output of the Boost converter is connected to the negative DC bus through the resistor R lpv And the inductor L lpv After being connected in series, they are connected to the positive DC bus.

[0027] Furthermore, the DC load unit includes a DC load, a DC converter and an LRC circuit, wherein the LRC circuit includes a capacitor C L , resistor R lL And the inductor L lL ; Inductance L lL One end of the inductor is connected to the positive DC bus. lL The other end is connected through the resistor R lL Connected to the input of the DC converter, the output of the DC converter supplies power to the DC load, the resistor R lL The common connection point between the input terminal of the DC converter is connected through a capacitor C L Connect to the negative DC bus.

[0028] Furthermore, the energy storage unit includes a battery pack, a DC converter and an LRC circuit, wherein the LRC circuit includes a capacitor C b , resistor R lb And the inductor L lb ; Inductance L lb One end of the inductor is connected to the positive DC bus, and the inductor L lb The other end is connected through the resistor R lb Connected to one end of the DC converter, the other end of the DC converter is connected to the battery pack, the resistor R lL The common connection point between the DC converter and the b Connect to the negative DC bus.

[0029] The beneficial effects of the present invention are as follows: through the present invention, based on the average power value of each path of the VSC grid-connected unit and based on the PI controller, the output power tracks the average power, and the difference is used as the virtual impedance compensation droop coefficient, so that the droop coefficient of the source with a smaller original power sharing is adjusted to a smaller value, and bears more load and gradually approaches the average value, thereby realizing the improvement of power distribution accuracy; while improving the power distribution accuracy of each source load of the photovoltaic storage DC distribution network, the DC voltage steady-state deviation is reduced, and the photovoltaic utilization rate is also taken into account, so that the photovoltaic utilization rate is improved, the system voltage steady-state deviation under different disturbance conditions is smaller and the power distribution accuracy is higher, and the DC voltage steady-state quality is effectively improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0031] Figure 1 It is a flow chart of the present invention.

[0032] Figure 2 It is a five-terminal photovoltaic storage DC system structure.

[0033] Figure 3 It is the traditional droop control characteristic curve.

[0034] Figure 4 Block diagram of improved droop control taking into account PV utilization.

[0035] Figure 5 The following are the power curves of each source under different control strategies for simulation conditions.

[0036] Figure 6 The following are the DC bus voltage curves under different control strategies for simulation conditions.

[0037] Figure 7 The load power random fluctuation diagram designed for simulation condition 1.

[0038] Figure 8The power curves of each source under different control strategies in simulation condition 2.

[0039] Fig. 9 The DC bus voltage curve under different control strategies in simulation condition 2.

[0040] Fig.10 Photovoltaic output variation curve designed for simulation condition 2. DETAILED DESCRIPTION

[0041] The present invention is further described in detail below:

[0042] The present invention provides a photovoltaic energy storage DC distribution network improvement control method based on photovoltaic utilization, comprising the following steps:

[0043] S1. Determine the topological structure of the photovoltaic DC distribution network, wherein the photovoltaic DC distribution network includes a photovoltaic unit, an energy storage unit, a DC load unit and a VSC grid-connected unit, wherein there are two VSC grid-connected units, the input ends of the two VSC grid-connected units are connected to the AC grid, and the output ends of the two VSC grid-connected units are connected to the DC bus; the energy storage unit, the DC load unit and the photovoltaic unit are all connected to the DC bus;

[0044] S2. Calculate the average power of the VSC grid-connected unit in the photovoltaic DC distribution network;

[0045] S3. Determine the virtual compensation impedance based on the average power;

[0046] S4. Determine the photovoltaic utilization rate of the photovoltaic DC distribution network;

[0047] S5. A droop control equation is constructed based on the virtual compensation impedance and the photovoltaic utilization rate, and the photovoltaic DC distribution network is controlled based on the droop control equation. Through the above method, due to the addition of the droop coefficient compensation link and the voltage deviation compensation link, the power distribution accuracy of each source load of the photovoltaic storage DC distribution network is improved while the DC voltage steady-state deviation is reduced, and the photovoltaic utilization rate is improved, so that the system voltage steady-state deviation under different disturbance conditions is smaller and the power distribution accuracy is higher, which effectively improves the DC voltage steady-state quality.

[0048] In this embodiment, determining the virtual compensation impedance based on the average power specifically includes:

[0049] The VSC grid-connected unit includes at least two grid-connected loops, each of which includes a VSC converter and an LRC circuit, wherein the LRC circuit includes a capacitor C g , resistor R l And the inductor L l The input end of the VSC converter is connected to the AC grid, and the positive output end of the VSC converter is connected to the AC grid through the capacitor C gConnected to the negative DC bus, the positive output of the VSC converter is connected to the negative DC bus through the resistor R l and inductor L l After being connected in series, they are connected to the positive DC bus;

[0050] The output power of each grid-connected circuit of the VSC grid-connected unit is tracked to the average power by using a PI controller;

[0051]

[0052] Where: Δr i is the virtual compensation impedance; α is the adjustment coefficient of the virtual compensation impedance; k pd , k id are the proportional coefficient and integral coefficient of the virtual compensation impedance PI controller, P dci is the output power of the i-th grid-connected circuit, i=1,2,…,n; is the average power of the VSC grid-connected unit.

[0053] in: In this embodiment, two grid-connected loops are used, so the value of n is 2.

[0054] exist Figure 2 Based on the structure in , after considering the VSC output impedance and DC side line impedance, the droop control characteristic curve is as follows Figure 3 As shown in the figure, U bus is the DC bus voltage; I1 and I2 are the output currents of VSC1 and VSC2 respectively; curves ① and ③ correspond to VSC1, and curves ② and ④ correspond to VSC2. Figure 3 Analysis shows that when a smaller droop coefficient is used, curves ① and ② show that the voltage deviation between the DC bus voltage and the set value is ΔU. At this time, due to different line impedances, VSC1 and VSC2 operate at points A and B respectively, and the current deviation between the two is ΔI. When the droop coefficient increases, corresponding to characteristic curves ③ and ④, the DC bus voltage will drop to U' bus , the corresponding voltage deviation is ΔU', VSC1 and VSC2 operate at points C and D respectively, and the current deviation between the two is ΔI'. Figure 3It can be seen that ΔU' is greater than ΔU, and ΔI' is less than ΔI, that is, the larger the droop coefficient, the greater the voltage drop of the DC system, and the smaller the load current distribution deviation of each converter station. Therefore, affected by the DC line impedance, the traditional droop control has a contradiction between the expected smaller DC voltage deviation of the converter station and the more accurate load power distribution; while the PI controller is used to track the average value of the output power of each grid-connected loop, weaken the influence of the line impedance on the power distribution accuracy of each source, and realize the power distribution of each source according to its rated capacity. The difference between the actual output power of each line and the power average value is used as the virtual impedance compensation droop coefficient, so that the droop coefficient of the source with a smaller original power sharing is adjusted to a smaller value, and it bears more load and gradually approaches the average value, thereby improving the power distribution accuracy.

[0055] In this embodiment, determining the photovoltaic utilization rate of the photovoltaic DC distribution network specifically includes:

[0056]

[0057] Among them: F pv (t) is the photovoltaic utilization rate, P pv (t) is the photovoltaic output power at time t, P pvmax is the maximum photovoltaic output power.

[0058] The improved droop control equation based on virtual compensation impedance and photovoltaic utilization rate includes:

[0059]

[0060] Where: R d is the droop coefficient, P gdc is the actual output power of the VSC converter DC side; is the reference value of the DC side output power of the VSC converter, is the reference value of the DC side output voltage of the VSC converter, u dc is the actual output voltage value of the DC side of the VSC converter, and g is the photovoltaic regulation coefficient.

[0061] The photovoltaic regulation coefficient g is determined as follows:

[0062]

[0063] Among them: U max , U min are the maximum and minimum values ​​of DC voltage respectively, is the rated output power of the photovoltaic power plant. The improved droop control equation can be used to determine Figure 4 The improved droop control block diagram structure of the photovoltaic storage DC distribution network with medium photovoltaic utilization rate; in this embodiment Figure 5 and Figure 6The output power curves of each source and the effect diagram of the DC bus output voltage when the photovoltaic output is constant are shown respectively. The design simulation condition 1 is: the total simulation time is 8s, a single-phase grounding fault occurs on the AC side VSC2 in the 1s-2s interval, and a single-phase grounding fault occurs in the 3s-4s interval. Figure 7 The load power shown in the figure fluctuates randomly. At 5s, VSC2 stops running and at 5.5s, VSC2 resumes running. Figure 5 It can be seen that under different disturbances, the improved droop control can achieve VSC load power distribution according to capacity. Taking the steady-state recovery process after a single-phase grounding fault on the AC side as an example, corresponding to the 2nd to 3rd second, Figure 5 (a) It can be seen that in this time interval, the output power of VSC1 and VSC2 under droop control is stable at 16.51kW and 12.79kW respectively, while the rated capacity of VSC1 and VSC2 set in this paper is the same. The data shows that under droop control, VSC does not distribute load power according to capacity. Figure 5 (b) It can be seen that after the single-phase grounding fault on the AC side disappears, the output powers of VSC1 and VSC2 return to the steady-state value and stabilize at 22.47 kW and 22.02 kW, respectively. The ratio of the output powers is basically consistent with the ratio of the rated capacities of the two. This shows that the improved droop control strategy can realize the distribution of load power between VSCs according to the rated capacity, effectively improving the power distribution accuracy between VSCs and eliminating the influence of line impedance on the load power distribution accuracy.

[0064] Depend on Figure 6 It can be seen that the DC bus voltage operating value of the photovoltaic storage DC distribution network under the improved droop control is closer to the rated value than the traditional droop control. In the time period from 5s to 5.5s, VSC2 exits operation, resulting in voltage drop. Under the traditional droop control, the voltage steady-state deviation value is 43.98V, and the voltage deviation rate reaches 5.6%. The "Guidelines for Medium and Low Voltage DC Distribution Network Voltages" stipulates that the voltage deviation range of DC systems below 1.5kV is -20% to +5%, so the power quality under traditional droop control does not meet the requirements. Under the improved droop control, the voltage steady-state deviation value is reduced to 12.93V, and the voltage deviation rate is 1.6%, which meets the requirements of the guidelines, indicating that the use of voltage feedforward compensation control can effectively compensate for the voltage deviation value, so that the voltage operates within a reasonable range and significantly improves the power quality.

[0065] In this embodiment Figure 8 and Fig. 9 The output power curves of each source and the effect diagram of the DC bus output voltage are shown respectively when the photovoltaic output is different. In order to further analyze the impact of photovoltaic output changes on the system control performance, the measured data of different photovoltaic power generation outputs are selected, and the light change curve is as follows Fig.10 Combined with the disturbance and Fig.10The photovoltaic output change curve shown in Figure 2 is considered as simulation condition 2. Figure 8 It can be seen that when the photovoltaic unit output suddenly changes, compared with the traditional droop control, the power borne by VSC1 and VSC2 under the improved droop control tends to be consistent, and both are allocated according to the rated capacity. At the same time, it is found that when the photovoltaic power suddenly changes, the photovoltaic unit under the traditional droop control does not quickly reach the maximum power output. 2 Sudden change to 1500W / m 2 For example, the time required for the photovoltaic unit to achieve maximum power output under traditional droop control is 0.18s, and the transition time for the photovoltaic unit to reach maximum power output under improved droop control is 0.05s, indicating that the photovoltaic power utilization rate is higher under improved droop control.

[0066] Depend on Fig. 9 It can be seen that with the change of light intensity, the DC voltage under the traditional droop control has a large fluctuation, and the fluctuation range is 94.6% to 101.8% of the steady-state value. When VSC2 is out of operation, there is still a voltage deviation of 46V, and the power quality is poor; when the improved droop control is adopted, the voltage regulation time is shortened by 0.15s, the voltage fluctuation amplitude is significantly reduced, the voltage fluctuation range is 98.1% to 100.9% of the steady-state value, and the output voltage curve is smoother and the voltage deviation is reduced to 20V, indicating that the voltage deviation has been effectively compensated. The improved droop control further improves the voltage steady-state quality.

[0067] In this embodiment, the photovoltaic unit includes a photovoltaic array, a Boost converter and an LRC circuit, wherein the LRC circuit includes a capacitor C pv , resistor R lpv And the inductor L lpv The input of the Boost converter is connected to the output of the photovoltaic array, and the positive output of the Boost converter is connected to the output of the photovoltaic array through the capacitor C pv Connected to the negative DC bus, the positive output of the Boost converter is connected to the negative DC bus through the resistor R lpv And the inductor L lpv After being connected in series, they are connected to the positive DC bus.

[0068] The DC load unit includes a DC load, a DC converter and an LRC circuit, wherein the LRC circuit includes a capacitor C L , resistor R lL And the inductor L lL ; Inductance L lL One end of the inductor is connected to the positive DC bus. lL The other end is connected through the resistor R lL Connected to the input of the DC converter, the output of the DC converter supplies power to the DC load, the resistor R lLThe common connection point between the input terminal of the DC converter is connected through a capacitor C L Connect to the negative DC bus.

[0069] The energy storage unit includes a battery pack, a DC converter and an LRC circuit, wherein the LRC circuit includes a capacitor C b , resistor R lb And the inductor L lb ; Inductance L lb One end of the inductor is connected to the positive DC bus. lb The other end is connected through the resistor R lb Connected to one end of the DC converter, the other end of the DC converter is connected to the battery pack, the resistor R lL The common connection point between the DC converter and the b Connected to the negative DC bus. The DC converter is a bidirectional DC converter (i.e. Figure 2 When the PV array outputs sufficient power, the battery pack can be charged. When the PV array outputs insufficient power, the battery pack can inject power into the DC bus. On the one hand, it can be injected into the AC grid through the grid-connected loop for grid connection, and on the other hand, it can directly supply power to the DC load.

[0070] Of course, the whole system also includes other control modules, which are all existing technologies. Each converter mentioned above adopts existing circuits and realizes output adjustment by adjusting the duty cycle of the PWM signal.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. An improved control method for photovoltaic storage DC distribution network based on photovoltaic utilization, characterized in that: The following steps are involved: S1. Determine the topological structure of the photovoltaic DC distribution network, wherein the photovoltaic DC distribution network includes a photovoltaic unit, an energy storage unit, a DC load unit and a VSC grid-connected unit, wherein there are two VSC grid-connected units, the input ends of the two VSC grid-connected units are connected to the AC grid, and the output ends of the two VSC grid-connected units are connected to the DC bus; the energy storage unit, the DC load unit and the photovoltaic unit are all connected to the DC bus; S2. Calculate the average power of the VSC grid-connected unit in the photovoltaic DC distribution network; S3. Determine the virtual compensation impedance based on the average power; S4. Determine the photovoltaic utilization rate of the photovoltaic DC distribution network; S5. Construct a droop control equation based on the virtual compensation impedance and the photovoltaic utilization rate, and control the operation of the photovoltaic DC distribution network based on the droop control equation.

2. According to the improved control method of photovoltaic energy storage DC distribution network based on photovoltaic utilization rate of claim 1, it is characterized by: Determining the virtual compensation impedance based on the average power specifically includes: The VSC grid-connected unit includes at least two grid-connected loops, each of which includes a VSC converter and an LRC circuit, wherein the LRC circuit includes a capacitor C g , resistor R l And the inductor L l The input end of the VSC converter is connected to the AC grid, and the positive output end of the VSC converter is connected to the AC grid through the capacitor C g Connected to the negative DC bus, the positive output of the VSC converter is connected to the negative DC bus through the resistor R l and inductor L l After being connected in series, they are connected to the positive DC bus; The output power of each grid-connected circuit of the VSC grid-connected unit is tracked to the average power by using a PI controller; Where: Δr i is the virtual compensation impedance; α is the adjustment coefficient of the virtual compensation impedance; k pd , k id are the proportional coefficient and integral coefficient of the virtual compensation impedance PI controller, P dci is the output power of the i-th grid-connected circuit, i=1,2,…,n; is the average power of the VSC grid-connected unit.

3. The improved control method for photovoltaic energy storage DC distribution network based on photovoltaic utilization rate according to claim 2 is characterized by: Determining the photovoltaic utilization rate of the photovoltaic DC distribution network specifically includes: Among them: F pv (t) is the photovoltaic utilization rate, P pv (t) is the photovoltaic output power at time t, P pvmax is the maximum photovoltaic output power.

4. The improved control method for photovoltaic energy storage DC distribution network based on photovoltaic utilization rate according to claim 3 is characterized by: The improved droop control equation based on virtual compensation impedance and photovoltaic utilization rate includes: Where: R d is the droop coefficient, P gdc is the actual output power of the VSC converter DC side; is the reference value of the DC side output power of the VSC converter, is the reference value of the DC side output voltage of the VSC converter, u dc is the actual output voltage value of the DC side of the VSC converter, and g is the photovoltaic regulation coefficient.

5. The improved control method for photovoltaic energy storage DC distribution network based on photovoltaic utilization rate according to claim 4 is characterized in that: The photovoltaic regulation coefficient g is determined as follows: Among them: U max , U min are the maximum and minimum values ​​of DC voltage respectively, is the rated output power of the photovoltaic power plant.

6. The improved control method for photovoltaic energy storage DC distribution network based on photovoltaic utilization rate according to claim 1 is characterized by: The photovoltaic unit includes a photovoltaic array, a Boost converter and an LRC circuit, wherein the LRC circuit includes a capacitor C pv , resistor R lpv And the inductor L lpv The input of the Boost converter is connected to the output of the photovoltaic array, and the positive output of the Boost converter is connected to the output of the photovoltaic array through the capacitor C pv Connected to the negative DC bus, the positive output of the Boost converter is connected to the negative DC bus through the resistor R lpv And the inductor L lpv After being connected in series, they are connected to the positive DC bus.

7. The improved control method for photovoltaic energy storage DC distribution network based on photovoltaic utilization rate according to claim 1 is characterized by: The DC load unit includes a DC load, a DC converter and an LRC circuit, wherein the LRC circuit includes a capacitor C L , resistor R lL And the inductor L lL ; Inductance L lL One end of the inductor is connected to the positive DC bus, and the inductor L lL The other end is connected through the resistor R lL Connected to the input of the DC converter, the output of the DC converter supplies power to the DC load, the resistor R lL The common connection point between the input terminal of the DC converter is connected through a capacitor C L Connect to the negative DC bus.

8. The improved control method for photovoltaic energy storage DC distribution network based on photovoltaic utilization rate according to claim 1 is characterized by: The energy storage unit includes a battery pack, a DC converter and an LRC circuit, wherein the LRC circuit includes a capacitor C b , resistor R lb And the inductor L lb ; Inductance L lb One end of the inductor is connected to the positive DC bus. lb The other end is connected through the resistor R lb Connected to one end of the DC converter, the other end of the DC converter is connected to the battery pack, the resistor R lL The common connection point between the DC converter and the b Connect to the negative DC bus.

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