Optical storage DC distribution network voltage inertia control method based on variable virtual capacitance

Abstract

An optical storage DC distribution network voltage inertia control method based on variable virtual capacitance provided by the present invention comprises the following steps: determining a topological structure of an optical storage DC system, the optical storage DC system comprising a photovoltaic unit, an energy storage unit, a DC load unit and two VSC grid-connected units, the number of the VSC grid-connected units being equal to that of the photovoltaic unit, the energy storage unit, the DC load unit and the VSC grid-connected units being equal to that of the photovoltaic unit; 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. Determining a direct current side power equation of the VSC grid-connected unit; a fixed virtual capacitor is introduced into the direct current side power equation, and the fixed virtual capacitor is determined; determining variable virtual capacitance based on the fixed virtual capacitance; and determining a voltage inertia control equation based on the variable virtual capacitance, and controlling the light output direct current system to work based on the voltage inertia control equation.

Description

Technical Field

[0001] The present invention relates to a voltage control method, and in particular to a voltage inertia control method for a photovoltaic storage DC distribution network based on variable virtual capacitors. Background Art

[0002] As the utilization rate of distributed energy continues to increase, DC distribution networks have attracted widespread attention due to their high-efficiency distributed energy and DC load access capabilities and their ability to connect to traditional AC power grids to form multi-terminal power grids. Distributed energy such as photovoltaics are connected to the DC distribution network through power electronic converters, resulting in the system's lack of inertial support capabilities. Factors such as parameter uncertainty, external disturbances, switching of converter stations, and unstable power output in the system will affect the stability of the DC bus voltage of the photovoltaic storage DC distribution network.

[0003] In the prior art, in order to solve the above problems, the following methods are generally adopted: first, by using the analogy relationship between AC and DC system variables, a virtual inertia control strategy for the DC system is proposed by analogy with the AC system rotor motion equation; second, the voltage transient quantity is introduced into the droop coefficient to achieve the effect of enhancing the virtual inertia of the system; third, an additional virtual inertia control strategy is proposed to increase the output current of the droop control link; however, the inertial support capacity of the above three methods still cannot meet the requirements of the distributed energy system, and more importantly, the above three methods have poor flexibility, thereby failing to guarantee the quality of the DC voltage.

[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 a voltage inertia control method for a photovoltaic energy storage DC distribution network based on a variable virtual capacitor. During the control process, by setting a fixed virtual capacitor and a variable virtual capacitor, the voltage inertia support capacity in the transient process can be effectively improved, and the voltage inertia support capacity can be flexibly adjusted, thereby reducing the transient overshoot of the system voltage under different disturbance conditions and improving the transient quality of the DC voltage.

[0006] The present invention provides a method for controlling voltage inertia of a photovoltaic storage DC distribution network based on variable virtual capacitors, comprising the following steps:

[0007] S1. Determine the topology of the photovoltaic storage DC system, wherein the photovoltaic storage DC system includes a photovoltaic unit, an energy storage unit, a DC load unit and a VSC grid-connected unit, the VSC grid-connected units are two, 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. Determine the DC side power equation of the VSC grid-connected unit;

[0009] S3. Introducing a fixed virtual capacitor into the DC side power equation and determining the fixed virtual capacitor;

[0010] S4. Determine the variable virtual capacitance based on the fixed virtual capacitance;

[0011] S5. Determine a voltage inertia control equation based on the variable virtual capacitor, and control the operation of the optical output DC system based on the voltage inertia control equation.

[0012] Furthermore, the DC side inertial support equation of the VSC grid-connected unit is determined to include:

[0013] The VSC grid-connected unit 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] Construct the power equation of the VSC grid-connected unit:

[0015]

[0016] Where: P dc P is the actual output power of the VSC converter at the DC side load end; gdc is the DC side capacitance C of the VSC converter g The actual output power; P C is the DC side capacitor C g Power provided; u dc is the DC side output voltage of the VSC converter.

[0017] Furthermore, a fixed virtual capacitor is introduced into the DC side inertial support equation, and the fixed virtual capacitor is determined to include:

[0018] Construct the DC side power equation with a fixed virtual capacitor:

[0019]

[0020] Where: C vir For a given virtual capacitance, P vir The power provided by a given virtual capacitor;

[0021] Solve the DC power equation containing a fixed virtual capacitor and obtain the fixed virtual capacitor C vir The value of .

[0022] Further, determining the variable virtual capacitance based on the fixed virtual capacitance specifically includes:

[0023]

[0024] Where: C avir is the variable virtual capacitor; k1, k2, k3 are the virtual capacitor adaptive coefficients, u dc is the actual output voltage value of the DC side of the VSC converter.

[0025] Further, the voltage inertia control equation is determined based on the variable virtual capacitor, and the operation of the optical DC system is controlled based on the voltage inertia control equation, specifically including:

[0026]

[0027] in: is the reference value of the output power of the VSC converter to the load side of the DC side. is the reference value of the DC side output voltage of the VSC converter, and k is the droop coefficient.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] Beneficial effects of the present invention: Through the present invention, during the control process, by setting a fixed virtual capacitor and a variable virtual capacitor, the voltage inertia support capacity in the transient process can be effectively improved, and the flexible adjustability of the voltage inertia support capacity can be achieved, thereby reducing the transient overshoot of the system voltage under different disturbance conditions and improving the transient quality of the DC voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0033] Figure 1 It is a flow chart of the present invention.

[0034] Figure 2 It is a five-terminal photovoltaic storage DC system structure.

[0035] Figure 3 This is the power relationship diagram of the VSC DC side under inertia-free control.

[0036] Figure 4 This is the power relationship diagram of the VSC DC side under inertia control.

[0037] Figure 5 This is the block diagram of fixed virtual capacitor voltage inertia control.

[0038] Figure 6 This is the block diagram of variable virtual capacitor voltage adaptive inertia control.

[0039] Figure 7 The following are the DC bus voltage curves under different inertia control strategies for simulation conditions.

[0040] Figure 8 Schematic diagram of random fluctuation of load power. DETAILED DESCRIPTION

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

[0042] The present invention provides a method for controlling voltage inertia of a photovoltaic storage DC distribution network based on variable virtual capacitors, comprising the following steps:

[0043] S1. Determine the topology of the photovoltaic storage DC system, wherein the photovoltaic storage DC system includes a photovoltaic unit, an energy storage unit, a DC load unit and a VSC grid-connected unit, the VSC grid-connected units are two, 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] like Figure 2 As shown: wherein 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.

[0045] 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.

[0046] 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 bconnected to the negative DC bus, wherein the DC converter is a bidirectional DC converter (i.e. Figure 2 B-DC in the system), when the photovoltaic array outputs sufficient power, the battery pack can be charged. When the photovoltaic 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 for grid connection, and on the other hand, it can directly supply power to the DC load. Of course, the entire system also includes other control modules, which are all existing technologies. Each converter in the above-mentioned system adopts existing circuits and realizes output adjustment by adjusting the duty cycle of the PWM signal of the adjuster.

[0047] S2. Determine the DC side power equation of the VSC grid-connected unit;

[0048] S3. Introducing a fixed virtual capacitor into the DC side power equation and determining the fixed virtual capacitor;

[0049] S4. Determine the variable virtual capacitance based on the fixed virtual capacitance;

[0050] S5. Determine the voltage inertia control equation based on the variable virtual capacitor, and control the operation of the optical DC system based on the voltage inertia control equation; through the above method, in the control process, by setting the fixed virtual capacitor and the variable virtual capacitor, the voltage inertia support capacity in the transient process can be effectively improved, and the voltage inertia support capacity can be flexibly adjusted, thereby reducing the transient overshoot of the system voltage under different disturbance conditions and improving the transient quality of the DC voltage.

[0051] Furthermore, the DC side inertial support equation of the VSC grid-connected unit is determined to include:

[0052] The VSC grid-connected unit 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;

[0053] Construct the power equation of the VSC grid-connected unit:

[0054]

[0055] Where: P dc P is the actual output power of the VSC converter at the DC side load end; gdc is the DC side capacitance C of the VSC converter g The actual output power; PC is the DC side capacitor C g Power provided; u dc is the DC side output voltage of the VSC converter.

[0056] In DC systems, droop control is usually used to distribute power between VSC sources. The control equation is:

[0057]

[0058] The equivalent circuit of the VSC DC side under traditional droop control is as follows: Figure 3 As shown, according to Figure 3 Then we can get the power equation mentioned above.

[0059] When the power provided by the power generating unit is balanced with the power required by the load unit, the DC side capacitor does not charge or discharge, so P gdc =P dc When the DC power is unbalanced P gdc ≠P dc When the DC side voltage stabilizing capacitor C g By releasing or absorbing power P C To smooth out power fluctuations. Under the same power imbalance, the DC side voltage stabilizing capacitor C g The smaller the voltage, the greater the voltage fluctuation, so the DC side voltage stabilizing capacitor C g It reflects the inertial support capacity of the DC voltage. Under normal circumstances, the DC side parallel capacitance value of the DC distribution network converter with a DC bus voltage of 500V is 2mF, and the inertial time constant is 0.008s. This shows that the DC side voltage stabilizing capacitor value is small, and the inertial support capacity of the DC system under droop control is weak.

[0060] To this end, a fixed virtual capacitor is introduced into the DC side inertial support equation, and the fixed virtual capacitor is determined to include:

[0061] Construct the DC side power equation with a fixed virtual capacitor:

[0062]

[0063] Where: C vir For a given virtual capacitance, P vir The power provided by a given virtual capacitor;

[0064] Solve the DC power equation containing a fixed virtual capacitor and obtain the fixed virtual capacitor C vir After adding a certain virtual capacitor, its power is as follows Figure 4 As shown in the figure, define P g ' dc is the VSC DC side stabilizing capacitor C when there is a virtual capacitor gOutput power value, and from the DC side power equation containing a fixed virtual capacitor, it can be seen that under the same power imbalance, compared with the non-inertia control, the VSC DC side parallel capacitor increases C after the introduction of virtual capacitor vir , which makes the voltage variation smaller and effectively suppresses the DC voltage fluctuation. vir The larger it is, the smaller the voltage change is, which effectively enhances the system voltage inertia support capability.

[0065] In this example, determining the variable virtual capacitance based on the fixed virtual capacitance specifically includes:

[0066]

[0067] Where: C avir is the variable virtual capacitor; k1, k2, k3 are the virtual capacitor adaptive coefficients, u dc is the actual output voltage value of the DC side of the VSC converter.

[0068] The voltage inertia control equation is determined based on the variable virtual capacitor, and the operation of the optical DC system is controlled based on the voltage inertia control equation. Specifically, the following are included:

[0069]

[0070] in: is the reference value of the output power of the VSC converter to the load side of the DC side. is the reference value of the DC output voltage of the VSC converter, and k is the droop coefficient. From the above, we can see that: in the steady state of the system, the voltage change rate du dc / dt is zero, at this time, the steady-state relationship between voltage and power is adjusted according to the droop control equation; in the case of system transient, the voltage change rate du dc / dt, generating auxiliary power through virtual capacitor To smooth out power imbalance Achieve voltage deviation The further reduction of can improve the transient stability of the system DC voltage, and the fixed virtual capacitor voltage inertia control block diagram can be obtained as follows: Figure 5 shown.

[0071] Depend on Figure 5 It can be seen from the control relationship shown that when the system has power fluctuations, the VSC under the fixed virtual capacitor voltage inertia control generates auxiliary power P according to the power transient fluctuations. vir To correct the droop input power The difference between the reference value and the actual value of the output voltage that affects the droop control Δu dc, and then through the subsequent double closed-loop PI control, the effect of connecting a virtual capacitor in parallel on the DC side of the VSC is achieved. The virtual capacitor quickly absorbs or releases power to smooth power fluctuations, prevent voltage mutations, and thus improve the transient stability of the DC bus voltage.

[0072] When the system power increases or decreases suddenly, the voltage change rate is the largest and the voltage deviation also increases rapidly. A larger virtual capacitor is needed during this period. The voltage deviation and the exponential function of the voltage change rate are introduced to achieve the effect of rapidly increasing the virtual capacitor, so as to enhance the inertial support capacity and reduce the power imbalance and smooth the voltage fluctuation. When the voltage change rate gradually decreases and the voltage gradually tends to be stable, a smaller virtual capacitor is needed to speed up the voltage recovery speed. At this time, the exponential function can achieve the effect of rapidly decreasing. When the voltage change rate and the deviation return to zero, the dependent variable of the exponential function is 1. At this time, the adaptive virtual capacitor is a fixed virtual capacitor value, which avoids frequent changes in the virtual capacitor, achieves a more orderly and accurate smoothing of the system's power fluctuations, enhances the inertia of the DC system, and improves the dynamic response quality of the system.

[0073] When there is a large unbalanced power in the system, the voltage deviation |u dc -U n |and rate of change|du dc / dt| is large, the adaptive virtual capacitor C avic is also large, providing the system with sufficient auxiliary power to smooth voltage fluctuations; when the unbalanced power of the system tends to be balanced, the voltage deviation and rate of change tend to zero, and the adaptive virtual capacitor C avic Gradually equal to the fixed virtual capacitance C vir , the inertial quality of the voltage is further improved during the entire dynamic process, achieving the goal of providing the system with flexible and adjustable virtual inertia according to the voltage operating conditions.

[0074] According to the expression of variable virtual capacitance, we can get Figure 6 The voltage adaptive inertia control block diagram structure of the variable virtual capacitor is shown.

[0075] In this embodiment Figure 7 The effect diagram of DC bus output voltage when the source load power changes is shown. 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 8 The load power shown in the figure fluctuates randomly. At 5s, VSC2 stops running and at 5.5s, VSC2 resumes running. Figure 7It can be seen that during the startup process in the interval of 0s to 1s, the DC bus voltage under the fixed virtual capacitor voltage inertia control rises slowly during the startup process, without overshoot and spikes, the overshoot is zero, the adjustment speed is slow, and the adjustment time is 0.75s; compared with the fixed inertia control, the DC bus voltage startup process under the voltage adaptive inertia control is faster, and the voltage reaches a stable value of 780V at 0.71s, and the overshoot is also zero; under the non-inertia control, the DC bus voltage rises faster during the startup process, the inertia is small, and overshoot spikes appear, the spike value reaches 808V, the overshoot is 3.3%, and the voltage drops afterwards, and finally gradually reaches a stable value of 780V at 0.6s. In the interval of 3s to 4s, the system load has random power fluctuations. With inertia-free control, the voltage continues to fluctuate according to the load change and does not enter a stable state. The voltage fluctuation amplitude under the fixed virtual capacitor inertia control is reduced, and it enters a stable state at 4.19s. The voltage inertia under the voltage adaptive inertia control is significantly improved, with smaller overshoot and fluctuation, and it enters a new steady-state value of 793V at 4.1s. The above analysis shows that when the system generates the same power imbalance, only the voltage stabilizing capacitor can provide inertia power under inertia-free control, and the transient quality of the system voltage and power is poor. The fixed virtual capacitor inertia control increases the inertia support capacity of the system, but the inertia power provided is a fixed value, which improves the voltage anti-disturbance and increases the voltage transient adjustment time. The virtual capacitor of the voltage adaptive inertia control is flexible and adjustable, and the output inertia power is flexible, which further reduces the voltage imbalance and reduces the voltage adjustment time. Therefore, when the system has uncertain power disturbances, the voltage adaptive inertia control can provide the system with adjustable inertia support, making the system power and voltage changes more stable, thereby improving the system power quality.

[0076] 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. A method for controlling voltage inertia of a photovoltaic energy storage DC distribution network based on variable virtual capacitor, characterized in that: The following steps are involved: S1. Determine the topology of the photovoltaic storage DC system, wherein the photovoltaic storage DC system includes a photovoltaic unit, an energy storage unit, a DC load unit and a VSC grid-connected unit, the VSC grid-connected units are two, 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. Determine the DC side power equation of the VSC grid-connected unit; S3. Introducing a fixed virtual capacitor into the DC side power equation and determining the fixed virtual capacitor; S4. Determine the variable virtual capacitance based on the fixed virtual capacitance; S5. Determine a voltage inertia control equation based on the variable virtual capacitor, and control the operation of the optical output DC system based on the voltage inertia control equation.

2. According to the method for controlling voltage inertia of photovoltaic energy storage DC distribution network based on variable virtual capacitor according to claim 1, it is characterized by: The DC side inertial support equation for determining the VSC grid-connected unit specifically includes: The VSC grid-connected unit 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; Construct the power equation of the VSC grid-connected unit: Where: P dc P is the actual output power of the VSC converter at the DC side load end; gdc is the DC side capacitance C of the VSC converter g The actual output power; P C is the DC side capacitor C g Power provided; u dc is the DC side output voltage of the VSC converter.

3. According to claim 2, the method for controlling voltage inertia of a photovoltaic energy storage DC distribution network based on variable virtual capacitor is characterized by: Introduce a fixed virtual capacitor into the DC side inertial support equation, and determine that the fixed virtual capacitor specifically includes: Construct the DC side power equation with a fixed virtual capacitor: Where: C vir For a given virtual capacitance, P vir The power provided by a given virtual capacitor; Solve the DC power equation containing a fixed virtual capacitor and obtain the fixed virtual capacitor C vir The value of .

4. According to claim 3, the method for controlling voltage inertia of a photovoltaic energy storage DC distribution network based on variable virtual capacitor is characterized by: Determining the variable virtual capacitance based on the fixed virtual capacitance specifically includes: Where: C avir is the variable virtual capacitor; k1, k2, k3 are the virtual capacitor adaptive coefficients, u dc is the actual output voltage value of the DC side of the VSC converter.

5. According to claim 4, the method for controlling voltage inertia of a photovoltaic energy storage DC distribution network based on variable virtual capacitor is characterized by: The voltage inertia control equation is determined based on the variable virtual capacitor, and the operation of the optical DC system is controlled based on the voltage inertia control equation. Specifically, the following are included: in: is the reference value of the output power of the VSC converter to the load side of the DC side. is the reference value of the DC side output voltage of the VSC converter, and k is the droop coefficient.

6. The voltage inertia control method of photovoltaic energy storage DC distribution network based on variable virtual capacitor 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 method for controlling voltage inertia of a photovoltaic-storage DC distribution network based on variable virtual capacitor according to claim 1 is characterized in that: 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 method for controlling voltage inertia of a photovoltaic energy storage DC distribution network based on variable virtual capacitor according to claim 1 is characterized in that: 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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