An electric spring system capable of separating active and reactive power compensation and a control method thereof

Abstract

The present invention discloses an electric spring system capable of separating active and reactive power compensation and its control method. The electric spring system utilizes two submodules to separate active and reactive power compensation functions from the circuit structure, facilitating separate control of the electric spring's active and reactive power compensation. Furthermore, the lower submodule responsible for active power compensation is effectively connected in parallel with non-critical loads. This eliminates the limitation of non-critical loads on the active power compensation provided by the electric spring, improving both the power compensation capability and the flexibility of the power compensation.

Description

Technical Field

[0001] The present invention belongs to the technical field of power electronics application technology and smart grid, and particularly relates to an electric spring system capable of separating active and reactive power compensation and a control method thereof. Background Art

[0002] Against the backdrop of China's "dual carbon" development strategy and its strong call for energy conservation and emission reduction, renewable energy generation and grid-connected technologies have experienced rapid development. While renewable energy generation systems offer advantages such as renewability and minimal environmental impact, their generation is intermittent. As weather conditions change, the system's power output fluctuates, leading to grid voltage fluctuations that adversely affect the operation of certain voltage-sensitive electrical equipment (critical loads). Static VAR compensators (SVCs) and battery energy storage have been proposed to address this issue, but both have limitations, such as the high cost of communication and battery energy storage required for SVC operation.

[0003] In 2012, by dualizing the laws of mechanical springs to power systems, Professor Xu Shuyuan of the University of Hong Kong proposed the new concept of "electric spring", which maintains the stability of critical load voltage by transferring power fluctuations in the power grid to devices that are insensitive to voltage changes (non-critical loads).

[0004] Current power springs are often connected in series with non-critical loads to form smart loads. In this configuration, the current flowing through the power spring is equal to the current flowing through the non-critical load, which limits the power spring's compensation capability. Furthermore, traditional power springs transfer all power fluctuations to the non-critical load without considering the voltage fluctuation range that the non-critical load can withstand. This can severely affect the operation of non-critical loads due to voltage exceeding the allowable range, or even damage the equipment.

[0005] In the prior art, a patent for an electric spring system and control method that takes into account non-critical loads (2019103780031) takes into account the voltage fluctuation range of non-critical loads. When the voltage of the non-critical load does not exceed the limit, the electric spring only performs reactive power compensation. When the voltage of the non-critical load exceeds the limit, in addition to reactive power compensation, active power compensation is also performed to control the voltage fluctuation range of the non-critical load. However, the patent still uses the traditional second-generation electric spring topology for the electric spring. Because this type of electric spring is directly connected in series with the non-critical load, the current flowing through the electric spring is affected by the non-critical load, and its power compensation capability is limited by the non-critical load. Moreover, because the active and reactive power compensated by this type of electric spring are coupled, power decoupling control is difficult to achieve. Summary of the Invention

[0006] In order to overcome the shortcomings of the existing technology, the present invention provides an electric spring system with separable active and reactive power compensation and a control method thereof, which are used to solve the problems faced in the above background technology that the electric spring compensation capacity is limited by non-critical loads and the non-critical load voltage fluctuations are too large.

[0007] The electric spring system of the present invention separates active power compensation and reactive power compensation from the circuit structure through two submodules, making it easier to control the active and reactive power compensation of the electric spring separately. In addition, the lower submodule responsible for active power compensation is actually connected in parallel with the non-critical load. This means that the active power compensation of the electric spring for the system is no longer restricted by the non-critical load, thereby improving the power compensation capability and flexibility of the electric spring.

[0008] The purpose of the present invention is achieved by at least one of the following technical solutions.

[0009] A separable power spring system for active and reactive power compensation, comprising a DC side energy storage battery, an upper submodule, a lower submodule, a switch S and an isolation transformer;

[0010] Among them, the input ports of the upper submodule and the lower submodule are connected in parallel with the DC side energy storage battery, and the output port of the upper submodule is connected to the non-critical load Z NCL The output port of the lower submodule is connected in series with the switch S and then connected to the non-critical load Z through the isolation transformer. NCL In parallel, the power spring system is combined with non-critical loads and then incorporated into a power grid including a high proportion of renewable energy power generation system to form a smart grid system;

[0011] When the electric spring system is working, the DC side energy storage battery provides a stable DC bus voltage. The upper and lower submodules separate the active compensation and reactive compensation of the electric spring system. The phase difference between the output voltage and output current of the upper submodule is locked to plus or minus 90 degrees, compensating reactive power to the smart grid system and transferring power fluctuations to non-critical loads Z. NCL The phase difference between the output voltage and output current of the upper and lower submodules is locked to 0 degrees or 180 degrees, compensating active power to the smart grid system and controlling the voltage fluctuation range of non-critical loads. The power spring system has two operating modes. Switch S is responsible for switching the operating mode. The isolation transformer isolates the output terminals of the two upper and lower submodules.

[0012] Furthermore, the smart grid system refers to an electric power system that uses power springs as demand-side management technology so that power consumption automatically follows power generation. The smart grid system includes a traditional power grid, a renewable energy power generation system, critical loads, non-critical loads and power springs.

[0013] Furthermore, the upper submodule and the lower submodule have the same structure and both include a power inverter and a filter. The input end of the power inverter is the input end of the upper submodule or the lower submodule, the output end of the power inverter is connected to the input end of the filter, and the output end of the filter is the output end of the upper submodule or the lower submodule.

[0014] Furthermore, the power inverter includes a single-phase full-bridge inverter.

[0015] Furthermore, the filter includes a second-order LC low-pass filter.

[0016] Furthermore, the two working modes include a first working mode and a second working mode, and the working mode is selected according to the degree of fluctuation of the power generation of the renewable energy power generation system;

[0017] Assume P in The sum of the active power injected into the load by the grid and renewable energy generation system in the smart grid system, P CLref is the rated active power of the critical load, P NCLmin and P NCLmax are the minimum and maximum active powers allowed for non-critical loads respectively;

[0018] When the power generation fluctuation of renewable energy power generation system is small, that is, P in ∈(P CLref +P NCLmin , P CLref +P NCLmax ), the power spring is in the first working mode. At this time, the switch S is open, and only the DC side energy storage battery and the upper side submodule in the power spring system are put into operation, compensating the reactive power to the smart grid system and transferring the power fluctuation to the non-critical load Z NCL superior.

[0019] Furthermore, when the power generation of renewable energy power generation system fluctuates greatly, that is, (P CLref +P NCLmin , P CLref +P NCLmax ), the power spring is in the second working mode, at this time the switch S is closed, the DC side energy storage battery, the upper side submodule and the lower side submodule are all put into operation, compensating the reactive power and active power to the smart grid system, and transferring the power fluctuation to the non-critical load Z NCL While controlling the voltage fluctuation range of non-critical loads.

[0020] A control method for an electric spring system capable of separable active and reactive power compensation includes control methods for an upper submodule and a lower submodule that are independent of each other; the control method for the lower submodule specifically includes the following steps:

[0021] S1. Detect non-critical load Z NCL The voltage v o , the non-critical load Z NCL The effective value of the voltage V o With non-critical load Z NCL The reference value V of the switch S and the non-critical load voltage are obtained by comparing the allowable voltage range of the switch S with the reference value V of the non-critical load voltage. oref ;

[0022] S2, set the non-critical load voltage reference value V oref With the actual value V o Difference to get ΔV o , the difference ΔV o After inputting the proportional integral controller, the reference value P of the active power that the lower submodule should compensate for the system is obtained. esref , P esref Divide by V o Then the effective value of the reference current output by the lower submodule is obtained. dref ;

[0023] S3, collect non-critical load Z NCL The voltage v o Input the phase-locked loop and get v o The synchronization phase angle J vo As the phase angle of the reference current Right now

[0024] S4, the phase angle of the reference current and effective value I dref Input the sine signal generator to get the reference current i output by the lower submodule dref ;

[0025] S5, the reference current i output by the lower submodule dref With the actual current i d Take the difference to get Δi d , the difference Δi d Input proportional integral controller to get the output voltage modulation wave v of the lower submodule esd ;

[0026] S6, the obtained voltage modulation wave v esd After comparison with the triangular carrier, the switch tube driving signal of the power inverter in the lower sub-module is obtained.

[0027] Furthermore, the upper submodule adopts pure reactive power control.

[0028] Furthermore, in step S1, when the non-critical load voltage is within the allowable range, a turn-off signal is given to the switch S, V oref =V o When the non-critical load voltage exceeds the allowable range, the switch S is given a conduction signal, V oref Equal to V o Adjacent permissible voltage range boundary value.

[0029] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0030] 1. It overcomes the limitation of non-critical load on the compensation capacity of traditional electric spring and improves the compensation capacity and flexibility of electric spring. Due to the structure of traditional electric spring directly connected in series with non-critical load, the current flowing through the electric spring is affected by the non-critical load Z. NCL This makes the compensation ability and flexibility of traditional electric springs subject to non-critical load Z NCL The power spring of the present invention uses two submodules to separate the active and reactive compensation of the power spring. The lower submodule 2 responsible for active compensation is directly connected in parallel with the non-critical load, overcoming the non-critical load Z from the circuit structure. NCL The limitation of the power spring is improved, and since the control of the two submodules of the power spring of the present invention is independent of each other, the flexibility of the power spring in performing active and reactive compensation on the system is greatly improved.

[0031] 2. Reduce the non-critical load Z NCL The voltage fluctuation degree of the power spring of the present invention is the lower submodule 2 and the non-critical load Z NCL Parallel connection mode, when non-critical load voltage V o When the limit is exceeded, the lower submodule 2 can flexibly compensate the system for active power, making the non-critical load voltage V o Restore to within the allowed range.

[0032] 3. Reduce the energy storage capacity required by the system. Compared with the traditional energy storage system, the power spring of the present invention makes the non-critical load Z NCL The electric spring bears part of the active power fluctuation, so the active power fluctuation that the electric spring needs to bear is smaller than that of the traditional energy storage system. Correspondingly, the battery energy storage capacity required on the DC side of the electric spring is also smaller than that of the traditional energy storage system. Therefore, the electric spring of the present invention also has the beneficial effect of reducing the energy storage capacity required by the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A structural diagram of a power spring system for separable active and reactive power compensation in a smart grid according to the present invention;

[0034] Figure 2 A topological structure diagram of the electric spring in the first working mode according to an embodiment of the present invention;

[0035] Figure 3 2. A topological structure diagram of the electric spring in the second working mode according to an embodiment of the present invention;

[0036] Figure 4 This is a control structure diagram of the lower submodule 2 of the power spring in an embodiment of the present invention;

[0037] Figure 5 1 is a simulation waveform diagram of the electric spring in simulation experiment 1 according to an embodiment of the present invention.

[0038] Figure 6 2 is a simulation waveform diagram of the electric spring in simulation experiment 2 according to an embodiment of the present invention. DETAILED DESCRIPTION

[0039] The present invention will be further described below with reference to specific embodiments.

[0040] Example:

[0041] An electric spring system with separable active and reactive power compensation, such as Figure 1 As shown, it includes a DC side energy storage battery, an upper submodule 1, a lower submodule 2, a switch S and an isolation transformer;

[0042] The input ports of the upper submodule 1 and the lower submodule 2 are connected in parallel with the DC side energy storage battery, and the output port of the upper submodule 1 is connected to the non-critical load Z NCL The output port of the lower submodule 2 is connected in series with the switch S and then connected to the non-critical load Z through the isolation transformer. NCL In parallel, the electric spring system is combined with non-critical loads and then incorporated into a power grid including a high proportion of renewable energy power generation system to form a smart grid system; the smart grid system refers to an electric power system that uses electric springs as a demand-side management technology so that power consumption automatically follows power generation. The smart grid system includes a traditional power grid, a renewable energy power generation system, critical loads, non-critical loads and electric springs.

[0043] When the electric spring system is working, the DC side energy storage battery provides a stable DC bus voltage. The upper submodule 1 and the lower submodule 2 separate the active compensation and reactive compensation of the electric spring system. The phase difference between the output voltage and the output current of the upper submodule 1 is locked to plus or minus 90 degrees, compensating the reactive power to the smart grid system and transferring the power fluctuation to the non-critical load Z. NCLThe phase difference between the output voltage and output current of the upper and lower submodules 2 is locked to 0 degrees or 180 degrees, compensating active power to the smart grid system and controlling the voltage fluctuation range of non-critical loads. The power spring system has two operating modes, and the switch S is responsible for switching the operating mode. The isolation transformer isolates the output ends of the upper submodule 1 and the lower submodule 2.

[0044] Furthermore, the upper submodule 1 and the lower submodule 2 have the same structure, both including a power inverter and a filter. The input end of the power inverter is the input end of the submodule, the output end of the power inverter is connected to the input end of the filter, and the output end of the filter is the output end of the submodule.

[0045] In one embodiment, the power inverter is a typical single-phase full-bridge inverter structure.

[0046] In one embodiment, the filter is a typical second-order LC low-pass filter structure.

[0047] like Figure 2 and Figure 3 As shown, the two working modes include a first working mode and a second working mode, and the working mode is selected according to the degree of fluctuation of the power generation power of the renewable energy power generation system;

[0048] like Figure 2 As shown, assuming P in The sum of the active power injected into the load by the grid and renewable energy generation system in the smart grid system, P CLref is the rated active power of the critical load, P NCLmin and P NCLmax are the minimum and maximum active powers allowed by non-critical loads. in ∈(P CLref +P NCLmin , P CLref +P NCLmax ), the power spring is in the first working mode, at this time the switch S is open, and only the DC side energy storage battery and the upper side submodule 1 in the power spring system are put into operation, compensating the reactive power to the smart grid system and transferring the power fluctuation to the non-critical load Z NCL superior;

[0049] like Figure 3 As shown in Figure 2, when the power generation of renewable energy power generation system fluctuates greatly, that is, (P CLref +P NCLmin , P CLref +P NCLmax), the power spring is in the second working mode, at this time the switch S is closed, the DC side energy storage battery, the upper submodule 1 and the lower submodule 2 are all put into operation, compensating the reactive power and active power to the smart grid system, and transferring the power fluctuation to the non-critical load Z NCL While controlling the voltage fluctuation range of non-critical loads.

[0050] In one embodiment, a control method for an electric spring system with separable active and reactive power compensation includes control methods for an upper submodule 1 and a lower submodule 2 that are independent of each other, wherein the upper submodule 1 adopts pure reactive power control;

[0051] like Figure 4 As shown, the control method of the lower submodule 2 specifically includes the following steps:

[0052] S1. Detect non-critical load Z NCL The voltage v o , the non-critical load Z NCL The effective value of the voltage V o With non-critical load Z NCL The reference value V of the switch S and the non-critical load voltage are obtained by comparing the allowable voltage range of the switch S with the reference value V of the non-critical load voltage. oref ;

[0053] When the non-critical load voltage is within the allowable range, a turn-off signal is given to the switch S, V oref =V o When the non-critical load voltage exceeds the allowable range, the switch S is given a conduction signal, V oref Equal to V o Adjacent permissible voltage range boundary value.

[0054] S2, set the non-critical load voltage reference value V oref With the actual value V o Difference to get ΔV o , the difference ΔV o After inputting the proportional integral controller, the reference value P of the active power that the lower submodule 2 should compensate for the system is obtained. esref , P esref Divide by V o Then the effective value of the reference current output by the lower submodule 2 is obtained. dref ;

[0055] S3, collect non-critical load Z NCL The voltage v o Input the phase-locked loop and get v o The synchronization phase angle J vo As the phase angle of the reference current Right now

[0056] S4, the phase angle of the reference current and effective value I dref Input the sine signal generator to get the reference current i output by the lower submodule 2 dref ;

[0057] S5, the reference current i output by the lower submodule 2 dref With the actual current i d Take the difference to get Δi d , the difference Δi d Input proportional integral controller to get the output voltage modulation wave v of the lower submodule 2 esd ;

[0058] S6, the obtained voltage modulation wave v esd After comparison with the triangular carrier, the switch tube driving signal of the power inverter in the lower submodule 2 is obtained.

[0059] In one embodiment, in order to verify the effect of the lower submodule 2 on the smart grid system, it is assumed that the critical load Z CL =R CL +jX CL , the critical load voltage is equal to the line voltage v s , the effective value is V s , the effective value of the line rated voltage is V sref , non-critical load Z NCL =R NCL +jX NCL , the voltage on non-critical load is v o , the effective value is V o The voltage fluctuation range allowed for non-critical loads is (V omin , V omax ) When the electric spring of the invention is in the first working mode, the electric spring of the invention is equivalent to the traditional electric spring using pure reactive power compensation control. After the system is running, the power generation power P of the new energy RES It can be expressed as:

[0060]

[0061] Because the non-critical load voltage V o The allowable voltage fluctuation range is (V omin , V omax ), so P NCL The minimum value P NCLmin and the maximum value P NCLmax for:

[0062]

[0063] So, P NCL The allowed fluctuation range is:

[0064] P NCL ∈(P NCLmin ,P NCLmax )(3)

[0065] Combining equations (1) and (3), the allowable fluctuation range of renewable energy power generation is:

[0066] P RES ∈(P CLref +P NCLmin ,P CLref +P NCLmax )(4)

[0067] When the electric spring of the invention is in the second working mode, the lower submodule 2 is put into operation. Assuming that the absolute value of the maximum active power that the lower submodule 2 can compensate for the system is |P es |,|P es |Not subject to non-critical loads Z NCL At this time, the allowable fluctuation range of renewable energy power generation becomes

[0068] P′ RES ∈(P CLref +P NCLmin -|P es |,P CLref +P NCLmax +|P es |) (5)

[0069] Comparing formula (4) and formula (5), it is obvious that

[0070]

[0071] From formula (6), it can be seen that after the lower submodule 2 is put into use, the power generation of the new energy can fluctuate within a larger range. In other words, the lower submodule 2 improves the compensation capacity of the power spring.

[0072] The power spring of the present invention realizes active power compensation by the lower submodule 2. The expression of the power spring of the present invention for system active power compensation can be written as:

[0073]

[0074] Among them, i esd is the output current of the lower submodule 2. Since the lower submodule 2 is connected to the non-critical load Z NCL In parallel, the output current i of the lower submodule 2 is esd Not subject to non-critical loads Z NCLTherefore, although the power spring of the present invention adds an inverter and a filter, the power spring of the present invention overcomes the non-critical load Z NCL The impact on the compensation capacity of the electric spring improves the compensation capacity of the electric spring. Since the two sub-modules separate the active and reactive compensation of the electric spring in the circuit structure, and the control of the two sub-modules is independent of each other, the flexibility of the electric spring in power compensation is greatly improved.

[0075] In order to verify the function of the electric spring proposed in the present invention, the present invention conducted two simulation experiments on the system in PLECS:

[0076] Simulation experiment 1 compares the traditional electric spring and the electric spring of the present invention. To make the comparison more vivid, the traditional electric spring adopts the classic pure reactive power compensation control method (other traditional electric spring control methods such as phase control method and RCD structure control method can also be used). The experimental parameters are set as follows: line rated voltage V sref =220V, rated operating frequency f=50Hz, critical load Z CL =(50+j50)Ω, non-critical load Z NCL =(50+j50)Ω, non-critical load voltage V o The allowable voltage fluctuation range is 200V~240V, and the renewable energy power generation power P is set. RES The power fluctuates between 785W and 1150W, with a fluctuation cycle of 5 seconds.

[0077] The simulation results are as follows Figure 5 As shown, when the new energy power generation power P RES When the critical load voltage V s and non-critical load voltage V o Fluctuates between 200V and 240V.

[0078] When a conventional electric spring is applied, the critical load voltage V s is stabilized at the rated value V sref =220V, the power fluctuation is transferred to the non-critical load Z NCL At this time, the non-critical load voltage V o The fluctuation range reaches 175V-260V, which exceeds the allowable voltage range.

[0079] When the electric spring of the present invention is put into operation, the critical load voltage V s is stabilized at the rated value V sref =220V, the actual voltage fluctuation range of non-critical loads is stable within the allowable range of 200~240V.

[0080] The results of simulation experiment 1 show that the power spring of the present invention has the function of regulating the degree of voltage fluctuation of non-critical loads, which can allow the new energy power generation to fluctuate within a wider range.

[0081] Simulation Experiment 2 primarily compared the energy storage capacity required by a traditional energy storage system and the electric spring of the present invention to stabilize fluctuations in renewable energy generation. The experimental parameters were the same as those in Simulation Experiment 1. By detecting the discharge power of the DC-side energy storage batteries of the two systems, integrating it, and taking its absolute value, the two relative energy storage capacities were obtained. By comparing them, the required energy storage capacity of the two systems could be determined.

[0082] The simulation results are as follows Figure 6 As shown, in order to stabilize the fluctuation of renewable energy generation, the battery discharge power of the traditional energy storage system fluctuates between -200W and 200W, and the required relative energy storage capacity is about 245W*s. NCL It bears some power fluctuations, and the active power compensation is not affected by non-critical load Z NCL Influenced by the above, the discharge power of the DC side energy storage battery of the power spring of the present invention is -100W~100W, and the required relative energy storage capacity is about 75W*s, which is only about 30% of the traditional energy storage system.

[0083] The results of simulation experiment 2 show that the electric spring of the present invention has the beneficial effect of reducing the energy storage capacity of the system compared with the traditional energy storage system.

[0084] The above examples are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the examples. Any other changes, modifications, replacements, combinations, simplifications made without departing from the spirit and principles of the present invention should be equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. An electric spring system with separable active and reactive power compensation, characterized in that: It includes a DC side energy storage battery, an upper side submodule (1), a lower side submodule (2), a switch S and an isolation transformer; The input ports of the upper submodule (1) and the lower submodule (2) are connected in parallel with the DC side energy storage battery, and the output port of the upper submodule (1) is connected in parallel with the non-critical load Z NCL The output port of the lower submodule (2) is connected in series with the switch S and then connected to the non-critical load Z through the isolation transformer. NCL In parallel, the power spring system is combined with non-critical loads and then incorporated into a power grid including a renewable energy power generation system to form a smart grid system; When the electric spring system is working, the DC side energy storage battery provides a stable DC bus voltage. The upper submodule (1) and the lower submodule (2) separate the active compensation and reactive compensation of the electric spring system. The phase difference between the output voltage and the output current of the upper submodule (1) is locked to plus or minus 90 degrees, and the reactive power is compensated to the smart grid system, and the power fluctuation is transferred to the non-critical load Z. NCL The phase difference between the output voltage and the output current of the upper and lower submodules (2) is locked to 0 degrees or 180 degrees, active power is compensated to the smart grid system, and the voltage fluctuation range of non-critical loads is controlled. The power spring system has two working modes. The switch S is responsible for switching the working mode. The isolation transformer isolates the output ends of the two upper submodules (1) and the lower submodule (2); the two working modes include a first working mode and a second working mode, and the working mode is selected according to the power generation power fluctuation degree of the renewable energy power generation system. Assume P in The sum of the active power injected into the load by the grid and renewable energy generation system in the smart grid system, P CLref is the rated active power of the critical load, P NCLmin and P NCLmax are the minimum and maximum active powers allowed for non-critical loads respectively; When the power generation fluctuation of renewable energy power generation system is small, that is, P in ∈(P CLref +P NCLmin , P CLref +P NCLmax ), the power spring is in the first working mode, at this time the switch S is open, and only the DC side energy storage battery and the upper side submodule (1) in the power spring system are put into operation, compensating the reactive power to the smart grid system and transferring the power fluctuation to the non-critical load Z NCL superior.

2. The electric spring system with separable active and reactive power compensation according to claim 1, characterized in that: The smart grid system refers to an electric power system that uses power springs as demand-side management technology to automatically adjust power consumption to power generation. The smart grid system includes a traditional power grid, a renewable energy power generation system, critical loads, non-critical loads, and power springs.

3. The electric spring system with separable active and reactive power compensation according to claim 1, characterized in that: The upper submodule (1) and the lower submodule (2) have the same structure and both include a power inverter and a filter. The input end of the power inverter is the input end of the upper submodule (1) or the lower submodule (2). The output end of the power inverter is connected to the input end of the filter. The output end of the filter is the output end of the upper submodule (1) or the lower submodule (2).

4. The electric spring system with separable active and reactive power compensation according to claim 3, characterized in that: The power inverter includes a single-phase full-bridge inverter.

5. The electric spring system with separable active and reactive power compensation according to claim 3, characterized in that: The filter comprises a second-order LC type low-pass filter.

6. The electric spring system with separable active and reactive power compensation according to claim 1, characterized in that: When the power generation of renewable energy power generation system fluctuates greatly, that is, When the power spring is in the second working mode, the switch S is closed, the DC side energy storage battery, the upper side submodule (1) and the lower side submodule (2) are all put into operation, compensating the reactive power and active power to the smart grid system, and transferring the power fluctuation to the non-critical load Z NCL While controlling the voltage fluctuation range of non-critical loads.

7. The control method of the electric spring system capable of separating active and reactive power compensation according to any one of claims 1 to 6, characterized in that: The invention relates to a control method for an upper submodule (1) and a lower submodule (2) which are independent of each other; the control method for the lower submodule (2) specifically comprises the following steps: S1. Detect non-critical load Z NCL The voltage v o , the non-critical load Z NCL The effective value of the voltage V o With non-critical load Z NCL The reference value V of the switch S and the non-critical load voltage are obtained by comparing the allowable voltage range of the switch S with the reference value V of the non-critical load voltage. oref ; S2, set the non-critical load voltage reference value V oref With the actual value V o Difference to get ΔV o , the difference ΔV o After inputting the proportional integral controller, the reference value P of the active power that the lower submodule (2) should compensate for the system is obtained. esref , P esref Divide by V o Then the effective value of the reference current output by the lower submodule (2) is obtained. dref ; S3, collect non-critical load Z NCL The voltage v o Input the phase-locked loop and get v o The synchronization phase angle J vo As the phase angle of the reference current Right now S4, the phase angle of the reference current and effective value I dref Input the sine signal generator to get the reference current i output by the lower submodule (2) dref ; S5, the reference current i output by the lower submodule (2) dref With the actual current i d Take the difference to get Δi d , the difference Δi d Input proportional integral controller to get the output voltage modulation wave v of the lower submodule (2) esd ; S6, the obtained voltage modulation wave v esd After comparison with the triangular carrier, a switch tube driving signal of the power inverter in the lower submodule (2) is obtained.

8. The control method of the electric spring system with separable active and reactive power compensation according to claim 7, characterized in that: The upper submodule (1) adopts pure reactive power control.

9. The control method of the electric spring system with separable active and reactive power compensation according to claim 7, characterized in that: In step S1, when the non-critical load voltage is within the allowable range, a turn-off signal is given to the switch S, V oref =V o When the non-critical load voltage exceeds the allowable range, the switch S is given a conduction signal, V oref Equal to V o Adjacent permissible voltage range boundary value.

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