Frequency modulation and voltage regulation method and system

Abstract

The invention discloses a frequency modulation and voltage regulation method and system, and belongs to the field of energy management of energy storage power stations. According to the method, a grid-connected voltage signal and a grid-connected current signal are collected, and the grid-connected frequency, the grid-connected voltage and the grid-connected frequency change rate are determined according to the collected signals. Judging whether the grid-connected frequency is in a set frequency range, calculating a first vacancy according to the judgment result, detecting the harmonic frequency, calculating a second vacancy according to the detection result, judging the change rate of the grid-connected frequency, calculating a third vacancy according to the judgment result, and determining the total active target power of the PCS according to the three vacancies. Judging whether the voltage exceeds a set voltage range or not, calculating reactive vacancy according to a judgment result, and determining the total reactive target power of the PCS according to the reactive vacancy, so as to achieve the adjustment of the grid-connected voltage. According to the invention, voltage and frequency regulation is carried out on each PCS by determining the total active and reactive target power, synchronous regulation of each PCS is realized, and the problem of difficult synchronous response of each PCS of an energy storage power station caused by a PCS autonomous frequency and voltage regulation mode is solved.

Description

Technical Field

[0001] The present invention belongs to the field of energy management of energy storage power stations, and in particular relates to a method and system for frequency and voltage regulation. Background Art

[0002] Changes in frequency and voltage will affect the safe and efficient operation and life of power generation and power-consuming equipment, so frequency and voltage regulation is crucial. Energy storage stations (especially electrochemical energy storage) have fast frequency and voltage regulation speeds, can flexibly switch between charging and discharging states, and actively support the active and reactive output of the power grid, thus becoming high-quality frequency and voltage regulation resources.

[0003] Energy storage stations exist on both the AC and DC sides, and require the energy conversion system PCS (Power Conversion System) to adjust. At the same time, PCS controls the output of energy storage batteries to complete the adjustment function. Since energy storage power stations need to meet certain delay conditions to participate in grid auxiliary services, especially primary frequency regulation and dynamic voltage regulation need to be completed within hundreds of milliseconds. If hundreds of PCSs measure each and autonomously perform charging or discharging based on the measurement results, the measurement errors and action time points of each PCS are different, and the values ​​of each PCS increasing or decreasing power are also different. It is difficult to make hundreds of PCSs synchronously output the corresponding power within hundreds of milliseconds, and the overall response consistency index of the energy storage power station will become poor.

[0004] In summary, the PCS of existing energy storage stations adopts an autonomous frequency and voltage regulation method, which leads to the problem of difficulty in synchronous response of each PCS in the energy storage power station. Summary of the invention

[0005] The purpose of the present invention is to provide a method and system for frequency and voltage regulation to solve the technical problem in the prior art that the PCS of the energy storage station adopts an autonomous frequency and voltage regulation method, which makes it difficult for the PCSs of the energy storage station to respond synchronously.

[0006] To achieve the above-mentioned purpose, the technical solution of the method and system for frequency modulation and voltage regulation provided by the present invention is:

[0007] A frequency modulation and voltage regulation method, which collects the grid connection point voltage signal and current signal on the energy storage power station side, determines the grid connection frequency and grid connection voltage according to the voltage signal; when the grid connection frequency falls within the set frequency range, determines the first active power shortage according to the primary frequency modulation difference rate, the collected grid connection frequency, the rated grid connection frequency, the frequency allowable deviation and the rated active power of the energy storage power station; when the grid connection frequency exceeds the set frequency range, determines the second active power shortage according to the gain current, the grid connection point voltage amplitude, the grid connection point current amplitude, the primary frequency modulation difference rate and the grid connection frequency; when the change rate of the grid connection frequency exceeds the set change rate range, starts the inertia support, and determines the active power shortage according to the grid connection frequency, the inertia time constant and the grid connection frequency. The third active power deficit is determined according to the first active power deficit, the second active power deficit and the third active power deficit; the total active power target of PCS is determined according to the first active power deficit, the second active power deficit and the third active power deficit, and the active power of each PCS is adjusted according to the total active power target of PCS to achieve the balance of grid frequency; when the grid voltage exceeds the set voltage, the reactive power deficit is determined according to the voltage adjustment coefficient, grid voltage, rated voltage, allowable voltage deviation and power factor setting, and the total reactive power target of PCS is determined according to the reactive power deficit, and the reactive power of each PCS is adjusted according to the total reactive power target of PCS to achieve the balance of grid voltage.

[0008] The beneficial effects are: collecting grid-connected voltage signals and current signals, and determining the grid-connected frequency, grid-connected voltage and grid-connected frequency change rate based on the collected signals. Determine whether the grid-connected frequency is within the set frequency range, calculate the first deficit based on the judgment result to adjust the grid-connected frequency, detect the harmonic frequency, calculate the second deficit based on the detection result to suppress the harmonic frequency, determine the rate of change of the grid-connected frequency, calculate the third deficit based on the judgment result to provide inertia support for the rate of change of the grid-connected frequency, and determine the total active power regulation target based on the three deficits. Then determine whether the voltage exceeds the set voltage range, calculate the reactive power deficit based on the judgment result, determine the total reactive power target based on the reactive power deficit, and achieve the regulation of the grid-connected voltage. The present application adjusts the voltage and frequency of each PCS by determining the total active and reactive target power, thereby achieving synchronous regulation of each PCS, and solving the problem of difficult synchronous response of each PCS in the energy storage power station caused by the PCS autonomous frequency and voltage regulation method.

[0009] As a further improvement, when adjusting the active power of each PCS according to the total active target power of the PCS, the ratio of the rated capacity of each PCS to the total rated capacity of all PCSs is calculated, and the total active target power of the PCS is distributed to each PCS according to the ratio; or the total active target power of the PCS is evenly distributed to each PCS according to the total number of PCSs.

[0010] The beneficial effect is that when achieving the total active power target of the PCS, the active power target is allocated to each PCS according to the proportion of the total rated capacity of each PCS station, which is more conducive to achieving the target of the PCS area. Alternatively, the total active power target is allocated to each PCS in an equal distribution mode to ensure that the pressure of achieving the target of each PCS is balanced.

[0011] As a further improvement, when the reactive power of each PCS is adjusted according to the total reactive target power of the PCS, the ratio of the rated capacity of each PCS to the total rated capacity of all PCSs is calculated, and the total reactive target power of the PCS is allocated to each PCS according to the ratio; or the total reactive target power of the PCS is evenly allocated to each PCS according to the total number of PCSs.

[0012] The beneficial effect is that when achieving the total reactive power target of PCS, the reactive power target is allocated to each PCS according to the proportion of the total rated capacity of each PCS station, which is more conducive to achieving the target of the PCS area. Alternatively, the total reactive power target is allocated to each PCS in an equal distribution mode to ensure that the pressure of achieving the target of each PCS is balanced.

[0013] As a further improvement, when the EMS target power sent by the power grid is received, the PCS total active power target power is determined based on the first active power deficit, the second active power deficit, the third active power deficit and the EMS target power.

[0014] The beneficial effect is that when an external EMC target power is received, the target is mixed with a target determined for frequency modulation to form one target for adjustment, thereby improving the efficiency of achieving the EMC target power.

[0015] As a further improvement, when the AVC target power sent by the power grid is received, the PCS total reactive power target is determined based on the reactive power deficit and the AVC target power.

[0016] The beneficial effect is that when receiving the AVC target power of other voltage regulation, the target is mixed with the target for voltage regulation to determine a general target, and reactive power is adjusted according to the general target, thereby improving the efficiency of achieving the AVC target power.

[0017] As a further improvement, the calculation formula for determining the first active power shortage is:

[0018]

[0019] Among them, δ is the primary frequency modulation rate; f is the collected grid-connected frequency; f N is the rated grid-connected frequency, Δf is the allowable frequency deviation; P N is the rated active power of the energy storage power station.

[0020] As a further improvement, the calculation formula for determining the third merit shortage is:

[0021]

[0022] Where t is time, f is grid-connected frequency, T J is the inertia time constant of the energy storage power station; P N is the rated capacity of the energy storage power station; f N is the rated frequency of the system; △f is the change in the grid-connected frequency of the energy storage power station; △P I is the power conversion amount.

[0023] As a further improvement, the calculation formula for determining reactive power shortage is:

[0024] ΔQ=K u N[U-(U N ±ΔU)]

[0025] Among them, K u is the voltage regulation coefficient; U is the actual line voltage of the system; U N is the system rated voltage; ΔU is the allowable voltage deviation; N is the power factor constant.

[0026] The present invention also discloses a frequency modulation and voltage regulation system, which includes a frequency modulation and voltage regulation module, a data acquisition module for collecting grid connection point data, and an energy management system storing basic data of energy storage power stations. The frequency modulation and voltage regulation module obtains frequency modulation instructions and voltage regulation instructions based on the data collected by the data acquisition module and the basic data of energy storage power stations collected by the energy management system using the above-mentioned frequency modulation and voltage regulation method, and controls the PCS according to the frequency modulation instructions and voltage regulation instructions.

[0027] The beneficial effect is that the frequency and voltage regulation module of the system obtains frequency regulation instructions and voltage regulation instructions by utilizing the above-mentioned frequency and voltage regulation method embodiment, thereby ensuring the synchronization of the responses of each PCS in the energy storage station.

[0028] As a further improvement, the frequency and voltage regulation module communicates with the PCS via the GOOSE network.

[0029] The beneficial effect is: improving the communication speed between the frequency modulation and voltage regulation module and the PCS. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A schematic diagram of the energy storage station architecture of the frequency and voltage regulation method of the present invention;

[0031] Figure 2 A schematic diagram of a frequency modulation process of the frequency modulation and voltage regulation method of the present invention;

[0032] Figure 3 It is a schematic diagram of the voltage regulation process of the frequency and voltage regulation method of the present invention;

[0033] Figure 4 A flow chart of the allocation target of the frequency and voltage regulation method of the present invention;

[0034] Figure 5 It is a schematic diagram of the framework of the frequency and voltage regulation system in the present invention;

[0035] Figure 6 It is a schematic diagram of the structure of functional block components of the frequency and voltage modulation system of the present invention. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. The components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0037] Frequency modulation and voltage regulation method embodiment:

[0038] like Figure 1-4 As shown, the method for frequency modulation and voltage regulation includes the following steps:

[0039] First, the voltage and current signals of the grid connection point on the energy storage power station side are collected, the grid connection frequency and grid connection voltage are determined according to the voltage signals, and the EMS target power and AVC target power issued by the power grid are received.

[0040] Secondly, if Figure 2 As shown, the frequency is adjusted according to the collected data. When the grid-connected frequency falls within the set frequency range, the first active power deficit is determined according to the primary frequency modulation difference rate, the collected grid-connected frequency, the rated grid-connected frequency, the frequency allowable deviation and the rated active power of the energy storage station; when the grid-connected frequency exceeds the set frequency range, the second active power deficit is determined according to the gain current, the grid-connected point voltage amplitude, the grid-connected point current amplitude, the primary frequency modulation difference rate and the grid-connected frequency. The set frequency range refers to a range that fluctuates above and below the power frequency 50HZ; when the rate of change of the grid-connected frequency exceeds the set rate of change range, the inertia support is started, and the third active power deficit is determined according to the grid-connected frequency, the inertia time constant, the rated capacity, the rated frequency, the grid-connected frequency change and the power change. The adjustment of abnormal frequency, inertia support and harmonic oscillation suppression are completed. The total active target power of the PCS is determined according to the first active deficit, the second active deficit and the third active deficit, and the active power of each PCS is adjusted according to the total active target power of the PCS to achieve the balance of the grid-connected frequency.

[0041] like Figure 3As shown, the voltage is adjusted according to the collected data. When the grid voltage exceeds the set voltage, the reactive power shortage is determined according to the voltage adjustment coefficient, grid voltage, rated voltage, voltage tolerance and power factor setting value, the total reactive power target of the PCS is determined according to the reactive power shortage, and the reactive power of each PCS is adjusted according to the total reactive power target of the PCS to achieve grid voltage balance.

[0042] When the EMS target power sent by the power grid is received, the PCS total active target power is determined based on the first active power deficit, the second active power deficit, the third active power deficit and the EMS target power.

[0043] When the AVC target power sent by the power grid is received, the total reactive power target of the PCS is determined based on the reactive power deficit and the AVC target power.

[0044] like Figure 4 As shown, when the active power of each PCS is adjusted according to the total active target power of the PCS, there are two allocation methods. Method 1: calculate the ratio of the rated capacity of each PCS to the total rated capacity of all PCSs, and allocate the total active target power of the PCS to each PCS according to the ratio; Method 2: evenly allocate the total active target power of the PCS to each PCS according to the total number of PCSs. Select any allocation method as needed to complete the allocation of the total active target power of the PCS. When the reactive power of each PCS is adjusted according to the total reactive target power of the PCS, the method of allocating the total reactive target power of the PCS refers to any of the two methods of allocating the total active target power of the PCS. As shown in Figure 4 As shown, K M is the distribution coefficient. Taking the total active power distribution of PCS as an example, the active power of each PCS is equal to the corresponding K M Multiply by the PCS total active target power; the calculation method for the corresponding PCS total reactive target power allocation is the same.

[0045] Specifically, the calculation formula for determining the first merit shortage is:

[0046]

[0047] Among them, δ is the primary frequency modulation rate; f is the collected grid-connected frequency; f N is the rated grid-connected frequency, Δf is the allowable frequency deviation; P N is the rated active power of the energy storage power station.

[0048] The calculation formula for determining the second meritorious service shortage is:

[0049] ΔP sso =-I mp ·G comp ·v mp·cos(2πf0t+δ p )

[0050] Among them, I mp is the gain current, G comp is the voltage amplitude at the grid connection point, v mp is the current amplitude at the grid-connected point, t is the delay time, δ is the primary frequency modulation rate, and f is the grid-connected frequency.

[0051] The calculation formula for determining the third meritorious deficiency is:

[0052]

[0053] Where t is time, f is grid-connected frequency, T J is the inertia time constant of the energy storage power station; P N is the rated capacity of the energy storage power station; f N is the rated frequency of the system; △f is the change in the grid-connected frequency of the energy storage power station; △P I is the power conversion amount.

[0054] The calculation formula for determining reactive power shortage is:

[0055] ΔQ=K u N[U-(U N ±ΔU)]

[0056] Among them, K u is the voltage regulation coefficient; U is the actual line voltage of the system; U N is the system rated voltage; ΔU is the allowable voltage deviation; N is the power factor constant.

[0057] This application adjusts the voltage and frequency of each PCS by determining the total active and reactive target power, thereby achieving synchronous regulation of each PCS and solving the problem of difficult synchronous response of each PCS in the energy storage power station caused by the PCS autonomous frequency and voltage regulation method. In addition, through implementation, it is found that this application also has the following beneficial effects: the action time from the frequency step mutation exceeding the primary frequency regulation dead zone to the output of the active power control command is no more than 50ms; the action time from the voltage step mutation exceeding the dynamic voltage regulation dead zone to the output of the reactive power control command is no more than 40ms; the frequency and voltage regulation system can connect to 256 PCS at the same time, which meets the capacity requirements of general energy storage stations and ensures the consistency of PCS output.

[0058] Frequency and voltage regulation system implementation example:

[0059] like Figure 1 , Figure 5As shown, the frequency and voltage regulation system includes a frequency and voltage regulation module, a data acquisition module for collecting grid connection point data, and an energy management system that stores basic data of energy storage power stations. The frequency and voltage regulation module obtains frequency modulation instructions and voltage regulation instructions based on the data collected by the data acquisition module and the basic data of the energy storage power station collected by the energy management system using the above-mentioned frequency and voltage regulation method, and controls the PCS according to the frequency modulation instructions and voltage regulation instructions. The frequency and voltage regulation module communicates with the PCS through the GOOSE network. GOOSE refers to general object-oriented substation events. It is a fast message transmission mechanism in IEC61850 and is used to transmit important real-time signals between IEDs in the substation. The GOOSE protocol is a MAC layer protocol, which greatly reduces latency. When an event occurs, it is sent according to 2-2-4-8 milliseconds, which ensures the speed and integrity of the data from a mechanism perspective. As shown Figure 6 As shown, when developing the operating program of the system, the functional block components of each function are set according to the content of the component library. Input, output and internal variables, a collection of sequentially executed functions that have acted on internal variables, can receive external input and return output results. Internal global variables can be accessed and modified by the outside. Function block configuration information is stored as an XML file in a certain structure, and is tested and published independently. When the processor processes the above-mentioned frequency modulation and voltage regulation method, it samples the form of a loop workspace. It only needs to set the total number of connected PCS according to the project requirements to complete the automatic generation of the PCS model, the GOOSE reception of the PCS, the logical calculation of the sent data, the transmission of telemetry and telesignaling, and the automatic allocation of PCS power. It can support the access of up to 256 PCSs, which is convenient and flexible when expanding the number of PCSs, and improves the expansion efficiency.

[0060] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention is described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions recorded in the aforementioned embodiments without creative work, or replace some of the technical features therein with equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for frequency modulation and voltage regulation, characterized in that: The method comprises the following steps: Collect the voltage and current signals of the grid connection point on the energy storage power station side, and determine the grid connection frequency and grid connection voltage based on the voltage signals; When the grid-connected frequency falls within the set frequency range, the first active power deficit is determined according to the primary frequency modulation difference rate, the collected grid-connected frequency, the rated grid-connected frequency, the allowable frequency deviation and the rated active power of the energy storage power station; when the grid-connected harmonic frequency is detected, the second active power deficit is determined according to the gain current, the grid-connected point voltage amplitude, the grid-connected point current amplitude, the primary frequency modulation difference rate and the grid-connected frequency; when the change rate of the grid-connected frequency exceeds the set change rate range, the inertia support is started, and the third active power deficit is determined according to the grid-connected frequency, the inertia time constant, the rated capacity, the rated frequency, the grid-connected frequency change and the power change; the total active power target of the PCS is determined according to the first active power deficit, the second active power deficit and the third active power deficit, and the active power of each PCS is adjusted according to the total active power target of the PCS to achieve the balance of the grid-connected frequency; When the grid voltage exceeds the set voltage, the reactive power shortage is determined according to the voltage adjustment coefficient, grid voltage, rated voltage, allowable voltage deviation and power factor constant. The total reactive power target of the PCS is determined according to the reactive power shortage. The reactive power of each PCS is adjusted according to the total reactive power target of the PCS to achieve grid voltage balance.

2. The method for frequency modulation and voltage regulation according to claim 1, characterized in that: When adjusting the active power of each PCS according to the total active target power of the PCS, the ratio of the rated capacity of each PCS to the total rated capacity of all PCSs is calculated, and the total active target power of the PCS is allocated to each PCS according to the ratio; or the total active target power of the PCS is evenly allocated to each PCS according to the total number of PCSs.

3. The method for frequency modulation and voltage regulation according to claim 1, characterized in that: When the reactive power of each PCS is adjusted according to the total reactive power target of the PCS, the ratio of the rated capacity of each PCS to the total rated capacity of all PCSs is calculated, and the total reactive power target of the PCS is allocated to each PCS according to the ratio; or the total reactive power target of the PCS is evenly allocated to each PCS according to the total number of PCSs.

4. The method for frequency modulation and voltage regulation according to any one of claims 1 to 3, characterized in that: The method further includes determining the PCS total active power target power according to the first active power deficit, the second active power deficit, the third active power deficit and the EMS target power when the EMS target power sent by the power grid is received.

5. The method for frequency modulation and voltage regulation according to any one of claims 1 to 3, characterized in that: The method also includes determining the PCS total reactive power target power based on the reactive power deficit and the AVC target power when the AVC target power sent by the power grid is received.

6. The method for frequency modulation and voltage regulation according to any one of claims 1 to 3, characterized in that: The calculation formula for determining the first merit shortage is: Among them, δ is the primary frequency modulation rate; f is the collected grid-connected frequency; f N is the rated grid-connected frequency, Δf is the allowable frequency deviation; P N is the rated active power of the energy storage power station.

7. The method for frequency and voltage modulation according to any one of claims 1 to 3, characterized in that: The calculation formula for determining the third meritorious deficiency is: Where t is time, f is grid-connected frequency, T J is the inertia time constant of the energy storage power station; P N is the rated capacity of the energy storage power station; f N is the rated frequency of the system; △f is the change in the grid-connected frequency of the energy storage power station; △P I is the power conversion amount.

8. The method for frequency and voltage modulation according to any one of claims 1 to 3, characterized in that: The calculation formula for determining reactive power shortage is: ΔQ=K u N[U-(U N ±ΔU)] Among them, K u is the voltage regulation coefficient; U is the actual line voltage of the system; U N is the system rated voltage; ΔU is the allowable voltage deviation; N is the power factor constant.

9. A frequency modulation and voltage regulation system, characterized in that: The system includes a frequency modulation and voltage regulation module and a data acquisition module for collecting grid connection point data. The frequency modulation and voltage regulation module obtains frequency modulation instructions and voltage regulation instructions based on the data collected by the data acquisition module and the basic data of the energy storage power station collected by the energy management system using the frequency modulation and voltage regulation method described in any one of claims 1 to 8, and controls the PCS according to the frequency modulation instructions and voltage regulation instructions.

10. The frequency modulation and voltage regulation system according to claim 9, characterized in that: The frequency and voltage regulation module communicates with the PCS through the GOOSE network.

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