An integrated energy storage and reactive power compensation system, operation method and design method

Abstract

The present invention provides an integrated energy storage and reactive power compensation system, comprising a new energy generation unit, an energy storage device, a switching capacitor, a switching reactor, and a passive filtering device. The new energy generation unit, energy storage device, switching capacitor, switching reactor, and passive filtering device are respectively connected to the low-voltage side of a main transformer via a collector line bus, and the high-voltage side of the main transformer is connected to the power grid. The energy storage device includes an energy storage battery and an energy storage converter for controlling the charging and discharging of the energy storage battery. The energy storage converter includes an additional controller for controlling the output of reactive power from the energy storage converter and performing harmonic control. During operation, the system preferentially uses switching capacitors, switching reactors, and passive filtering devices to improve the power quality of the new energy power station. When the system is short of power, it coordinates and controls the energy storage device to improve the power quality of the new energy power station, thereby reducing the number of charge and discharge cycles of the energy storage device and increasing the life of the energy storage battery.

Description

Technical Field

[0001] The present invention relates to the technical field of reactive power compensation, and in particular to an integrated energy storage and reactive power compensation system, an operating method and a design method. Background Art

[0002] Currently, after new energy projects are equipped with energy storage, they are still required to configure full-capacity SVG and other reactive compensation devices according to the requirements of the new energy power quality report. Some regions also require the configuration of passive filtering devices to improve power quality. This fails to fully utilize the full-capacity reactive compensation potential and harmonic control functions of the energy storage devices, resulting in not only a waste of energy storage resources but also further increasing the investment cost of new energy power stations. Summary of the Invention

[0003] The purpose of the present invention is to provide an integrated energy storage and reactive power compensation system, an operation method and a design method to address the defects of the prior art.

[0004] The present invention provides an integrated energy storage and reactive power compensation system, comprising a new energy power generation unit, an energy storage device, a switching capacitor, a switching reactor, and a passive filtering device. The new energy power generation unit, the energy storage device, the switching capacitor, the switching reactor, and the passive filtering device are respectively connected to the low-voltage side of a main transformer through a collector line bus, and the high-voltage side of the main transformer is connected to the power grid;

[0005] The energy storage device includes an energy storage battery and an energy storage converter for controlling the charging and discharging of the energy storage battery. The energy storage converter includes an additional controller for controlling the energy storage converter to output reactive power and perform harmonic control.

[0006] Furthermore, the additional controller includes an additional controller 1, the input of the additional controller 1 is the reactive power command value, the output of the additional controller 1 is the q-axis current command value of the energy storage converter, and the output end of the additional controller 1 is directly connected to the input end of the q-axis current controller of the energy storage converter; the additional controller 1 is used to process the reactive power command value and form the q-axis current command value of the q-axis current controller of the energy storage converter, and control the energy storage converter to output reactive current through the q-axis current controller, thereby controlling the energy storage converter to output reactive power.

[0007] Furthermore, the additional controller includes an additional controller 2, the input of which is the voltage at the lower end of the phase-locked dq coordinate system, and the output of which is directly connected to the output of the dq axis current controller of the energy storage converter; the additional controller 2 is used to process the voltage at the lower end of the phase-locked dq coordinate system and feed it back to the output of the current controller, forming active filtering, thereby reducing harmonic current. The present invention also provides an operating method for an integrated energy storage and reactive power compensation system, including:

[0008] S1. Obtain the reactive power compensation capacity and harmonic control requirements required by the power system to which the new energy power station is connected;

[0009] S2, judging whether the switching capacitors, switching reactors and passive filtering devices can meet the reactive power compensation capacity and harmonic control requirements required by the power system; if not, executing step S3;

[0010] S3. Control the energy storage device to participate in reactive power compensation and harmonic control through an additional controller.

[0011] Furthermore, step S3 includes: when the reactive compensation function of the switching capacitor, the switching reactor and the passive filter device is insufficient, the reactive shortage is fed back to the output of the q-axis current controller of the energy storage converter in the form of a command value, and after being processed by the additional controller, a q-axis current command value is formed, and the q-axis current controller controls the output reactive current of the energy storage converter, thereby controlling the output reactive power of the energy storage converter.

[0012] Furthermore, step S3 includes: the additional controller 2 processes the voltage at the lower end of the phase-locked dq coordinate system and feeds it back to the output end of the current controller to form active filtering and reduce the harmonic current of the new energy power station connected to the power system.

[0013] The present invention also provides a design method for an integrated energy storage and reactive power compensation system, comprising:

[0014] S1, according to the reactive power compensation capacity demand of new energy power station [-Q SC , Q SI ] and the reactive compensation capacity of the energy storage device [-S C , S C ], calculate the capacitive reactive compensation capacity S required for switching capacitors and switching reactors ΣC And inductive reactive compensation capacity S ΣI : The energy storage device includes an additional controller; Q SC Q is the capacitive reactive power compensation demand of new energy power station. SI is the inductive reactive power compensation demand of the new energy power station, S C is the capacity of the energy storage device;

[0015] S2. Calculate the parameters of the passive filter device based on the harmonic order n that needs to be controlled by the new energy power station: Where, L n and C n They are the filter capacitor and filter inductor of the nth harmonic passive filter device, f0 is the power frequency, Q fn It is the capacitive reactive power injected into the grid by the nth harmonic passive filter device;

[0016] S3, based on the capacitive reactive compensation capacity S required for switching capacitors and switching reactors ΣC And inductive reactive compensation capacity S ΣI , calculate the capacity Q of the switching capacitor TC and parameter C TC And the capacity Q of the switching reactor TL and parameter L TL :

[0017] Furthermore, in step S2,

[0018] The beneficial effects of the present invention are:

[0019] 1. The present invention uses an additional controller to modify the energy storage converter, so that the energy storage device has the functions of reactive power compensation and harmonic control. When the system is in operation, the switching capacitors, switching reactors and passive filtering devices are preferentially used to improve the power quality of the new energy power station. When the power is insufficient, the energy storage device is coordinated and controlled to improve the power quality of the new energy power station, thereby reducing the number of charge and discharge times of the energy storage device and increasing the life of the energy storage battery.

[0020] 2. This invention eliminates the need for a full-capacity SVG reactive compensation device and provides a design and selection basis for switching capacitors, switching reactors, and filtering devices, significantly reducing the investment cost of new energy power stations.

[0021] 3. The present invention can effectively improve the power quality of new energy power stations connected to the power system and enhance the friendliness of the new energy power station access system. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a topological diagram of the integrated system of energy storage and reactive power compensation in a new energy power station according to the present invention;

[0023] Figure 2 This is a structural diagram of a common energy storage device converter;

[0024] Figure 3 The control block diagram of the energy storage converter of the present invention is attached;

[0025] Figure 4 The coordinated control strategy among the energy storage device, switching capacitors, switching reactors, and passive filtering device of the present invention;

[0026] Figure 5 It is the basic form of the additional controller of the present invention;

[0027] Figure 6 Provides a reactive power compensation simulation schematic diagram for the energy storage device of the present invention;

[0028] Figure 7This is a simulation diagram of the energy storage device of the present invention participating in harmonic control in a new energy power station. DETAILED DESCRIPTION

[0029] In order to make the technical problems, technical solutions and beneficial effects to be solved by this application more clearly understood, this application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0030] like Figure 1 As shown, an integrated energy storage and reactive power compensation system includes a new energy power generation unit, an energy storage device, a switching capacitor, a switching reactor, and a passive filtering device. The new energy power generation unit, the energy storage device, the switching capacitor, the switching reactor, and the passive filtering device are respectively connected to the low-voltage side of the main transformer through the collector line bus, and the high-voltage side of the main transformer is connected to the power grid;

[0031] like Figure 2 As shown, T1 to T6 are IGBT modules of the energy storage converter. abc is the internal potential, v tabc and i abc is the converter terminal voltage and output current, θ p is the phase-locking angle, and is the projection of the terminal voltage in the phase-locked dq coordinate system, and are the projections of the output current in the phase-locked dq coordinate system, and are the projections of the internal potential in the phase-locked dq coordinate system, and are the current command values ​​in the phase-locked dq coordinate system respectively. dc and V dcref The actual value and command value of the DC voltage of the energy storage battery are respectively. By controlling the size of the DC voltage command value, the charging and discharging power of the energy storage battery can be controlled. ref It is the reactive current command value, which can control the reactive power output by the energy storage converter.

[0032] like Figure 3 As shown, the energy storage converter is modified by additional controller 1 and additional controller 2. The output of additional controller 1 is the q-axis current command value of the energy storage converter. The output end of additional controller 1 is directly connected to the input end of the q-axis current controller of the energy storage converter. The input of additional controller 2 is the lower end voltage of the phase-locked dq coordinate system. The output end of additional controller 2 is directly connected to the output end of the dq-axis current controller of the energy storage converter.

[0033] When the reactive power compensation function of the switching capacitors, switching reactors and filters is insufficient, the reactive power shortage is fed back to the output of the q-axis current controller of the energy storage converter in the form of a command value. After being processed by the additional controller, it forms the q-axis current command value. The q-axis current controller controls the output reactive current of the energy storage converter, and further controls the output reactive power of the energy storage converter. Commonly used additional controllers are as follows Figure 5 As shown in (a), the reactive power command value is first converted into a reactive current command value, and then output to the input end of the q-axis current controller after passing through a low-pass filter.

[0034] In order to improve the power quality of the new energy project connected to the power system and reduce the injected harmonics, the voltage at the lower end of the phase-locked dq coordinate system can be fed back to the output end of the current controller after passing through the additional controller 2 to form an active filter device to reduce the harmonic current of the new energy power station connected to the system. Figure 5 As shown in (b) of the figure, it consists of a lead-lag controller. After adding the controller, the energy storage device can have full-capacity reactive power compensation and harmonic control functions.

[0035] In order to verify the feasibility of the solution, an energy storage device model was built in Matlab / Simulink, and the reactive power compensation and harmonic control scenarios were simulated.

[0036] like Figure 6 As shown in the figure, after adopting the additional control, as the reactive power demand of the system increases, the reactive power that the energy storage device can provide increases accordingly, and the maximum output reactive power of the energy storage device is the capacity of the converter of the energy storage device.

[0037] like Figure 7 As shown in Figure 2, after adopting additional control, the harmonics injected into the power system by the new energy power station are reduced from 4.71% to 1.96%, a reduction of about 60%.

[0038] The design method of the integrated energy storage and reactive power compensation system includes:

[0039] S1. According to the power quality report of the new energy power station access system, determine the reactive power compensation capacity demand of the new energy power station [-Q SC , Q SI ], Q SC Q is the capacitive reactive power compensation demand of new energy power station. SI The reactive power compensation demand of the new energy power station is: C , S C ], S C For the capacity of the energy storage device, calculate the capacitive reactive compensation capacity S required for switching capacitors and switching reactors. ΣC And inductive reactive compensation capacity S ΣI :

[0040] If S ΣC ≤0, the new energy power station does not need to be equipped with switching capacitors and passive filtering devices, and only energy storage devices can meet the system's capacitive reactive power compensation needs and harmonic control needs; if S ΣI If the value is ≤0, the new energy power station does not require switching reactors; energy storage alone can meet the system's inductive reactive power compensation needs. Otherwise, the new energy power station will need switching capacitors, switching reactors, and filtering devices to work together with energy storage to improve the power quality of the new energy power station's access system.

[0041] S2. According to the power quality report of the new energy power station access system, determine the harmonic order n that needs to be controlled and calculate the parameters of the passive filter device: Where, L n and C n They are the filter capacitor and filter inductor of the nth harmonic passive filter device, f0 is the power frequency, Q fn It is the capacitive reactive power injected into the grid by the nth harmonic passive filter device;

[0042] Generally, in order to avoid the filter device injecting too much capacitive reactive power into the grid and causing waste of reactive power compensation resources, the following requirements are required when designing the parameters of the passive filter device:

[0043] S3, based on the capacitive reactive compensation capacity S required for switching capacitors and switching reactors ΣC And inductive reactive compensation capacity S ΣI , calculate the capacity Q of the switching capacitor TC and parameter C TC And the capacity Q of the switching reactor TL and parameter L TL :

[0044] like Figure 4 As shown, through coordinated control among various devices, capacitors, reactors, and passive filters are preferentially used to improve the power quality of the new energy power station. When there is a shortage of power, the energy storage devices are coordinated and controlled to improve the power quality of the new energy power station, thereby reducing the number of charge and discharge times of the energy storage device and increasing the life of the energy storage battery.

[0045] First, the reactive power compensation capacity and harmonic control requirements required by the power system are collected, and then it is determined whether the switching capacitors, switching reactors and filtering devices can meet the power quality control needs of the power system. If they can meet the requirements, the energy storage device does not need to participate in reactive power compensation and harmonic control. Otherwise, the energy storage device participates in the system reactive power compensation and harmonic control through an additional controller.

[0046] Let's use an example to illustrate: For a 100MW photovoltaic project configured with 25% reactive power compensation and 10% / 2h of energy storage, the project requires -25MW to 25MW of reactive power compensation and 10MW / 20MWh of energy storage. If the energy storage device does not participate in reactive power compensation, the cost of using the full SVG for reactive power compensation and harmonic control is approximately 2.7 million yuan. If the energy storage device fully participates in reactive power compensation and harmonic control, only a 15MW reactive power compensation and harmonic control device is required, which, after accounting for additional controller costs, is approximately 1.5 million yuan. Therefore, using the full capacity of the energy storage device for reactive power compensation and harmonic control can save 1.2 million yuan in investment costs and reduce harmonics by approximately 60%. This improves the power quality and accessibility of the new energy power station system, thereby reducing the overall investment in the new energy project.

[0047] The above-described embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present application, and should all be included in the scope of protection of the present application.

Claims

1. An integrated energy storage and reactive power compensation system, characterized by: It includes a new energy power generation unit, an energy storage device, a switching capacitor, a switching reactor and a passive filtering device. The new energy power generation unit, the energy storage device, the switching capacitor, the switching reactor and the passive filtering device are respectively connected to the low-voltage side of the main transformer through the collector line bus, and the high-voltage side of the main transformer is connected to the power grid; The energy storage device includes an energy storage battery and an energy storage converter for controlling the charging and discharging of the energy storage battery. The energy storage converter includes an additional controller for controlling the energy storage converter to output reactive power and perform harmonic control. The additional controller includes an additional controller 1, the input of the additional controller 1 is a reactive power command value, the output of the additional controller 1 is a q-axis current command value of the energy storage converter, and the output end of the additional controller 1 is directly connected to the input end of the q-axis current controller of the energy storage converter; the additional controller 1 is used to process the reactive power command value and form a q-axis current command value of the q-axis current controller of the energy storage converter, and control the energy storage converter to output reactive current through the q-axis current controller, thereby controlling the energy storage converter to output reactive power; The additional controller includes an additional controller 2, the input of the additional controller 2 is the voltage at the lower end of the phase-locked dq coordinate system, and the output end of the additional controller 2 is directly connected to the output end of the dq axis current controller of the energy storage converter; the additional controller 2 is used to process the voltage at the lower end of the phase-locked dq coordinate system and feed it back to the output end of the current controller to form active filtering, thereby reducing harmonic current; The operation method of the integrated energy storage and reactive power compensation system includes: S1. Obtain the reactive power compensation capacity and harmonic control requirements required by the power system to which the new energy power station is connected; S2, judging whether the switching capacitors, switching reactors and passive filtering devices can meet the reactive power compensation capacity and harmonic control requirements required by the power system; if not, executing step S3; S3, controlling the energy storage device to participate in reactive power compensation and harmonic control through an additional controller; The step S3 includes: when the reactive power compensation function of the switching capacitor, the switching reactor, and the passive filter device is insufficient, the reactive power shortage is fed back to the output of the q-axis current controller of the energy storage converter in the form of a command value, and after being processed by the additional controller, a q-axis current command value is formed, and the q-axis current controller controls the output of the reactive current of the energy storage converter, thereby controlling the output of the reactive power of the energy storage converter; The second additional controller processes the voltage at the lower end of the phase-locked dq coordinate system and feeds it back to the output end of the current controller to form active filtering and reduce the harmonic current of the new energy power station connected to the power system.

2. A design method for an integrated energy storage and reactive power compensation system according to claim 1, characterized in that: include: S1, according to the reactive power compensation capacity demand of new energy power station [-Q SC , Q SI ] and the reactive compensation capacity of the energy storage device [-S C , S C ], calculate the capacitive reactive compensation capacity S required for switching capacitors and switching reactors ΣC And inductive reactive compensation capacity S ΣI : The energy storage device includes an additional controller; Q SC Q is the capacitive reactive power compensation demand of new energy power station. SI is the inductive reactive power compensation demand of the new energy power station, S C is the capacity of the energy storage device; S2. Calculate the parameters of the passive filter device based on the harmonic order n that needs to be controlled by the new energy power station: Where, L n and C n They are the filter capacitor and filter inductor of the nth harmonic passive filter device, f0 is the power frequency, Q fn It is the capacitive reactive power injected into the grid by the nth harmonic passive filter device; S3, based on the capacitive reactive compensation capacity S required for switching capacitors and switching reactors ΣC And inductive reactive compensation capacity S ΣI , calculate the capacity Q of the switching capacitor TC and parameter C TC And the capacity Q of the switching reactor TL and parameter L TL :

3. The design method of the integrated energy storage and reactive power compensation system according to claim 2, characterized in that: In the step S2,

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