Active support type commutation technology

Abstract

The invention relates to the technical field of direct current transmission, in particular to an E-HCC converter station, an E-STATCOM capacity configuration method, a storage medium and equipment, the E-HCC converter station comprises a converter transformer, an HCC converter valve and an E-STATCOM, the converter valve side of the converter transformer is connected with the HCC converter valve, and the alternating current power grid side of the converter transformer is connected to the E-STATCOM. According to the E-HCC converter station, the E-STATCOM is connected to the alternating current power grid side of the converter transformer, the reactive power requirement of the converter station for a receiving end system is reduced, voltage and frequency support can be provided for the receiving end system, and the application scene of the conventional direct current transmission technology is expanded.

Description

Technical Field

[0001] The present invention relates to the technical field of direct current transmission, and in particular to an E-HCC converter station, an E-STATCOM capacity configuration method, a storage medium and a device. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] A typical LCC converter station mainly includes converter transformers, converter valves, AC filters and switches, reactive power compensation equipment, DC filters and switches, grounding electrodes and other equipment and supporting control and protection systems. With the expansion of the scale of new energy development, some converter stations have also added energy storage equipment to meet the needs of large-scale new energy access. Figure 1 , Figure 2 As shown. In an LCC converter station, the AC switchyard is one of the largest areas in the converter station. Usually, the AC filter occupies about 50% of the entire converter station area, and the equipment cost accounts for 10% of the total cost of the converter station. The LCC solution has the advantages of large transmission capacity and low cost, but there are two key problems: one is the phase change failure during operation, and the other is the lack of inertia support capability.

[0004] In response to the commutation failure problem of LCC, the State Grid Economic Research Institute proposed a multi-source adaptive commutation converter (SLCC) solution. This solution connects the STATCOM device to the busbar on the valve side of the converter transformer at the receiving end converter station to reduce the equivalent impedance of the receiving end AC system and provide additional commutation voltage support for the converter valve; at the same time, STATCOM adopts the APF control strategy to achieve AC filtering, effectively reducing the harmonic content injected into the converter transformer. The problem with the SLCC solution is that it uses the method of providing additional commutation voltage to reduce the probability of commutation failure, but it cannot reliably solve the commutation failure problem in the case of severe faults; in addition, this solution uses STATCOM to provide reactive compensation, but due to the large leakage reactance of the converter transformer, its reactive compensation capacity for the receiving end power grid is limited; in addition, this solution completely uses STATCOM to achieve reactive compensation and active filtering. Due to the limited capacity of power electronic equipment, this solution is not easy to apply in UHV projects.

[0005] In response to the commutation failure problem in LCC, the hybrid commutation converter (HCC) solution proposed by Tsinghua University replaces the thyristor in the LCC converter valve with IGCT, which can realize the active shutdown of the valve and use the forced shutdown capability to achieve reliable commutation between valve sections, completely solving the commutation failure problem and ensuring the safe and stable operation of the DC project. The HCC solution can reduce the arc extinction angle of the converter valve and reduce the reactive power demand on the power grid compared with traditional LCC equipment; however, the required reactive capacity is still maintained at about 30% of the rated capacity; and the active support of the receiving power grid of this solution needs to rely on the overload operation of the converter station, and the reactive support needs to rely on the reactive compensation equipment used by the station, which has limited support capacity for the power grid. The basic operating principle of the HCC solution is still similar to that of the LCC. During operation, the reactive power demand is large, and the stability requirement of the receiving power grid is high, which limits the application scenarios of this technology.

[0006] In view of the above-mentioned defects, the present invention makes improvements. Summary of the invention

[0007] In order to overcome the shortcomings of the background technology, the present invention provides an E-HCC converter station, an E-STATCOM capacity configuration method, a storage medium and a device. The E-HCC converter station is connected to the E-STATCOM on the AC power grid side of the converter transformer, which reduces the reactive power demand of the converter station on the receiving system, and can provide voltage and frequency support for the receiving system, thereby expanding the application scenarios of conventional DC transmission technology.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] In a first aspect, an E-HCC converter station is provided, comprising a converter transformer, an HCC converter valve and an E-STATCOM, wherein the converter valve side of the converter transformer is connected to the HCC converter valve, and the AC grid side of the converter transformer is connected to the E-STATCOM.

[0010] Further,

[0011] The E-STATCOM is connected to the AC grid side of the converter transformer using a step-up transformer.

[0012] Further,

[0013] The voltage level of the AC grid side of the converter transformer is 500 kV, and the voltage level of the converter valve side of the converter transformer is 100 kV;

[0014] The E-STATCOM is a 35kV energy storage device and is connected to the receiving-end AC power grid using the step-up transformer.

[0015] Further,

[0016] The E-STATCOM includes a plurality of SM energy storage units connected in series, wherein the SM energy storage unit includes an H-bridge power module and a super capacitor, and the super capacitor forms an energy storage device through the H-bridge power module.

[0017] In a second aspect, a method for configuring the capacity of an E-STATCOM is also provided, which is applied to the aforementioned E-HCC converter station, and the method comprises:

[0018] The capacity of the E-STATCOM is determined according to the reactive power demand of the HCC converter valve and the active and reactive power demand of the receiving-end AC power grid. The capacity of the E-STATCOM includes active capacity and reactive capacity.

[0019] Further,

[0020] Determining the reactive capacity of the E-STATCOM includes:

[0021] Calculate the total capacitive reactive capacity Q of the E-HCC converter station total ;

[0022] Calculate the total inductive reactive capacity Q of the E-HCC converter station r ;

[0023] Compare the total capacitive reactive capacity Q total The total inductive reactive capacity Q r and the larger of the two is taken as the reactive capacity of the E-STATCOM.

[0024] Further,

[0025] The total capacitive reactive capacity Q total satisfy:

[0026]

[0027] in:

[0028] Q total It indicates the total reactive power that E-STATCOM can provide under the normal operating voltage of the AC busbar of E-HCC converter station; Q ac It represents the reactive power demand of the AC system assumed when determining the capacity of the reactive power supply equipment;

[0029] Q dc It represents the reactive power demand of the DC converter equipment assumed when determining the reactive power supply equipment;

[0030] m represents the reserve coefficient;

[0031] k1 represents the corresponding voltage correction coefficient.

[0032] Further,

[0033] The total inductive reactive capacity Q r satisfy:

[0034]

[0035] in:

[0036] Q r It indicates the total reactive power that can be absorbed by E-STATCOM under the normal operating voltage of the AC busbar of E-HCC converter station;

[0037] Q acmax Indicates the maximum reactive power allowed to flow from the converter station into the AC system when calculating reactive power absorption equipment;

[0038] Q fmin Indicates the reactive power generated by other equipment under the normal operating voltage of the AC busbar of the E-HCC converter station;

[0039] Q dc It represents the reactive power demand of the DC converter equipment assumed when determining the reactive power supply equipment;

[0040] k2 represents the corresponding voltage correction coefficient.

[0041] Further,

[0042] Determining the active capacity of the E-STATCOM includes:

[0043] Calculating the virtual inertia of the E-STATCOM, and determining the output power of the E-STATCOM according to the response time of a primary frequency modulation;

[0044] The active capacity of the E-STATCOM is determined according to the output power of the E-STATCOM.

[0045] Further,

[0046] The calculating of the virtual inertia of the E-STATCOM comprises:

[0047] Determine the minimum inertia requirement of the system based on the maximum frequency change rate and maximum frequency deviation of the system;

[0048] The virtual inertia required for the E-STATCOM is obtained by subtracting the inertia of all conventional units in the system from the system's minimum inertia requirement.

[0049] Further,

[0050] Determining the minimum inertia requirement of the system according to the maximum frequency change rate and the maximum frequency deviation of the system includes:

[0051] According to the maximum frequency change rate of the system, the minimum inertia requirement of the system is:

[0052]

[0053] According to the maximum frequency deviation of the system, the minimum inertia requirement of the system is:

[0054]

[0055] Among them, E sys is the energy form of the system equivalent inertia, in MW·s;

[0056] f N is the system rated frequency;

[0057] RoCoF max is the maximum frequency change rate required by the system;

[0058] ΔP loss is the unbalanced active power of the system;

[0059] R N To quickly respond to the maximum output power of a frequency modulation device;

[0060] R G The maximum output power of a synchronous machine with a slower response speed.

[0061] T s With T g They are the response time for a fast-responding primary frequency modulation device and a slower-responding synchronous machine to reach maximum output power;

[0062] Δf max is the maximum frequency deviation allowed by the system;

[0063] According to the two inequalities of the minimum inertia requirement of the system mentioned above, the constraint of the minimum inertia requirement of the system can be obtained, and then the minimum inertia requirement of the system can be determined.

[0064] Further,

[0065] The frequency change of the system satisfies the following formula:

[0066]

[0067] Among them, E sys is the energy form of the system equivalent inertia, in MW·s;

[0068] f N and Δf(t) are the system rated frequency and system frequency deviation respectively;

[0069] t is time; D is damping coefficient; PL is the system load level;

[0070] ΔP G (t) is the primary frequency modulation response power of the unit;

[0071] ΔP loss is the unbalanced active power of the system.

[0072] Further,

[0073] The output power of the E-STATCOM is E E-STATCOM / T s , where E E-STATCOM Indicates the virtual inertia that the E-STATCOM needs to have, T s The time it takes for a frequency modulation device to reach its maximum output power quickly.

[0074] Based on the same inventive concept, the present invention also provides a computer-readable storage medium storing one or more programs, which, when executed, can implement the aforementioned E-STATCOM capacity configuration method.

[0075] Based on the same inventive concept, the present invention also provides an electronic device, including a processor, a communication interface, a computer-readable storage medium as described above, and a communication bus; wherein the processor, the communication interface, and the computer-readable storage medium communicate with each other via the communication bus; and the processor is used to execute the program stored in the computer-readable storage medium.

[0076] Compared with the prior art, the present invention has the following beneficial effects:

[0077] 1. A new hybrid commutation converter technology (Enhanced HCC, E-HCC) with reactive power support capability is proposed. E-STATCOM is used to realize AC filtering, reactive power compensation and active power compensation. On the basis of HCC, inertia support for the receiving power grid is realized, the stability of the receiving power grid is improved, and the traditional AC filtering and reactive power compensation equipment is replaced to realize an integrated AC switch field. At the same time, the reactive power demand of the converter station on the receiving power grid is reduced, and voltage and frequency support can be provided for the receiving power grid, which expands the application scenarios of conventional DC transmission technology;

[0078] 2. A capacity configuration method for an active supported STATCOM (i.e., E-STATCOM) is provided. The capacity of the E-STATCOM is determined by simultaneously considering the reactive power demand of the converter valve and the active and reactive power demand of the receiving power grid, and the configuration methods of the reactive capacity and active capacity are given respectively.

[0079] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description, claims and drawings.

[0080] The present invention will be further described below in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0081] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0082] Figure 1 A schematic diagram of an LCC converter station in the prior art;

[0083] Figure 2 A topological diagram of an LCC converter station in the prior art;

[0084] Figure 3 A topological diagram of an E-HCC converter station according to an embodiment of the present invention;

[0085] Figure 4 A topological diagram of an E-STATCOM according to an embodiment of the present invention;

[0086] Figure 5 The figure is a schematic diagram of the structure of an electronic device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0087] In order to make the purpose, technical solution and advantages of the implementation of the present invention clearer, the technical solution in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is only a part of the embodiment of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0088] like Figure 3 to Figure 4 As shown, an embodiment of the present invention provides an E-HCC converter station, including a converter transformer, an HCC converter valve and an E-STATCOM, wherein the converter valve side of the converter transformer is connected to the HCC converter valve, and the AC power grid side of the converter transformer is connected to the E-STATCOM.

[0089] The basic idea of ​​the above technical solution is to arrange an enhanced STATCOM (Enhanced STATCOM, referred to as E-STATCOM) on the AC side of the existing HCC converter station, and use E-STATCOM to realize AC filtering, reactive power compensation and active power compensation, and realize inertia support for the receiving power grid (i.e., the receiving AC power grid) on the basis of HCC, improve the stability of the receiving power grid, and replace the traditional AC filtering and reactive power compensation equipment to realize an integrated AC switch field. Based on the existing technology, the above technical solution proposes a new hybrid commutation converter technology (EnhancedHCC, E-HCC) with reactive power support capability, which reduces the reactive power demand of the converter station on the receiving system (i.e., the receiving power grid), and can provide voltage and frequency support for the receiving system, expanding the application scenarios of conventional DC transmission technology.

[0090] As a preferred technical solution, the E-STATCOM is connected to the AC grid side of the converter transformer using a step-up transformer. In this embodiment, the use of a step-up transformer can better connect the E-STATCOM to the AC grid side of the converter transformer. E-STATCOM is an energy storage device. The number of power electronic devices and supporting facilities used in ultra-high voltage direct-mounted energy storage devices is large, and the volume is large, which has difficulties in feasibility and economy. The use of a step-up transformer can reduce the voltage level of the equipment and improve the economy of the equipment.

[0091] According to a specific embodiment, the voltage level of the AC grid side of the converter transformer is 500kV, and the voltage level of the converter valve side of the converter transformer is 100kV; the E-STATCOM is a 35kV energy storage device, and is connected to the receiving end AC grid using the step-up transformer.

[0092] The specific location for E-STATCOM access should be selected based on the function of the equipment, the problem to be solved, and the requirements for insulation and other indicators at different locations. Figure 3 As shown in the figure, the receiving AC grid has two locations for E-STATCOM access, namely, the 500kV converter transformer grid side and the 100kV converter transformer valve side. The E-STATCOM grid-connected port is an AC line, and there are only the above two locations available in the converter station (usually, it is not considered to connect the main electrical equipment on the converter station power bus).

[0093] In comparison, E-STATCOM connected to the valve side has a better effect on filtering harmonics transmitted from the converter valve, and has a stronger support capacity for the converter valve commutation process, but the leakage reactance of the converter transformer is large, and the voltage and frequency support capacity of the power grid may decrease; connected to the grid side, its support capacity is stronger, and the harmonic compensation capacity in the grid is better, but the support capacity for the commutation process of the converter valve may be insufficient. Overall, HCC has a stronger ability to resist commutation failure, and it is more necessary to make up for its weak support capacity for the power grid. Therefore, the embodiment of the present invention chooses to use a step-up transformer to connect to E-STATCOM on the AC power grid side.

[0094] Among them, the 500kV converter transformer grid side and the 100kV converter transformer valve side refer to the two sides of the same converter transformer, where the grid side voltage level is 500kV and the converter valve side voltage level is 100kV. The transformer parameters in the same converter station are the same. Figure 3 The four converter transformers on the right are all converter transformers that convert the converter valve AC voltage of 100kV (right side) to the grid voltage of 500kV (left side).

[0095] As a preferred technical solution, the E-STATCOM includes multiple SM energy storage units connected in series, the SM energy storage unit includes an H-bridge power module and a supercapacitor, and the supercapacitor constitutes an energy storage device through the H-bridge power module. In this embodiment, a module cascade solution is adopted, that is, multiple modules (i.e., SM energy storage units) are cascaded to form one phase, and the three phases are connected to the power grid using a step-up transformer.

[0096] The topological design of the E-STATCOM in this embodiment is similar to that of the conventional STATCOM, but there are differences in the energy storage devices used. In contrast, the STATCOM DC side uses capacitors, which can achieve flexible reactive power exchange with the power grid and mainly provide AC voltage support; while the E-STATCOM DC side uses supercapacitors, which has a greatly improved energy storage capacity. In theory, it can provide reactive power exchange and short-term active power feed-in at the same time, and further realize the inertia support capacity based on active power feed-in on the basis of STATCOM to maintain system frequency stability. The difference between supercapacitors and ordinary capacitors is mainly that supercapacitors have stronger energy storage capacity and can store more energy to achieve short-term active power output, rather than reactive power output of STATCOM equipment (actually the periodic input and output changes of instantaneous power); conventional energy storage devices use battery packs, but the response speed is insufficient compared to supercapacitors.

[0097] This embodiment considers the withstand voltage level and cost of power electronic equipment, and recommends that E-STATCOM use supercapacitors to store energy, form a 35kV energy storage device through an H-bridge power module, and use a step-up transformer to connect to the receiving end AC power grid, such as Figure 4In this embodiment, the H-bridge power module is used to achieve the bidirectional access capability of the DC side supercapacitor, and the control is more flexible.

[0098] exist Figure 4 In the SM energy storage unit, C dc As a supporting capacitor, it is used to maintain the DC voltage. This capacitor belongs to the H-bridge power module. At present, the capacity of a single supercapacitor cannot meet the design requirements of the embodiment of the present invention. A supercapacitor with a larger capacity can be implemented in the form of a supercapacitor cluster with multiple modules connected in series and parallel, which can be equivalent to a single larger supercapacitor. The SM energy storage unit of this embodiment adopts a supercapacitor cluster with multiple supercapacitors connected in series to implement the application. In the SM energy storage unit, the resistors on both sides of the series supercapacitors are current limiting resistors, which can prevent excessive charging and discharging currents.

[0099] The solution of the E-STATCOM in this embodiment uses a power module based on power electronic devices (i.e., an H-bridge power module) to connect supercapacitors to the system, and stores a certain amount of energy when the system is operating normally. When the voltage or frequency of the AC side power grid fluctuates, the E-STATCOM can respond quickly, provide reactive and active power support for the system, and maintain the stability of the system voltage and frequency. In addition, the E-STATCOM can also achieve active filtering, which can replace the existing AC filter and achieve better filtering effects for non-characteristic harmonics. The above-mentioned E-STATCOM solution is similar to the H-bridge cascade energy storage device.

[0100] Figure 4 The topology used in the embodiment is an H-bridge cascade topology, which is a solution for connecting multiple DC modules to an AC power grid. The E-STATCOM proposed in the embodiment of the present invention adopts an H-bridge cascade solution to connect to the power grid, and uses supercapacitors as DC side energy storage devices instead of ordinary capacitors of STATCOM or batteries of conventional energy storage devices. Compared with battery devices, it has a faster response speed and a stronger energy storage capacity than ordinary capacitors, and can realize the inertia support function.

[0101] In the second aspect, a method for configuring the capacity of an E-STATCOM is also provided, which is applied to the aforementioned E-HCC converter station, and the method includes: determining the capacity of the E-STATCOM according to the reactive power demand of the HCC converter valve and the active and reactive power demand of the receiving AC power grid, and the capacity of the E-STATCOM includes active capacity and reactive capacity.

[0102] In the above technical solution, to determine the capacity of E-STATCOM, it is necessary to consider both the reactive power demand of the HCC converter valve and the active and reactive power demand of the receiving power grid. The above technical solution provides an overall idea for determining the capacity of E-STATCOM. In this embodiment, the reactive power demand of the HCC converter valve is given by Q in the following formula: dc To reflect, the reactive power demand of the receiving grid is represented by Q ac To reflect, the simultaneous consideration here means that the reactive power compensation equipment needs to consider these two parts of reactive power capacity at the same time, which is the design idea of ​​E-STATCOM. dc With Q ac The detailed configuration method can be further referred to the prior art and will not be introduced here.

[0103] As a preferred technical solution, determining the reactive capacity of the E-STATCOM includes: calculating the total capacitive reactive capacity Q of the E-HCC converter station. total ; Calculate the total inductive reactive capacity Q of the E-HCC converter station r ; Compare the total capacitive reactive capacity Q total The total inductive reactive capacity Q r and the larger of the two is taken as the reactive capacity of the E-STATCOM.

[0104] The reactive capacity of E-STATCOM is symmetrical, so the total capacitive reactive capacity Q is selected. total and total inductive reactive capacity Q r The larger of the two is used as the reactive capacity of E-STATCOM. The reactive capacity of E-STATCOM is the maximum reactive power it can output, which is both the maximum inductive reactive output power and the maximum capacitive output power. Therefore, the reactive capacity of E-STATCOM needs to meet the larger of the two.

[0105] The above technical solution will be further explained below.

[0106] For the reactive capacity of E-STATCOM, the total capacitive reactive capacity Q of E-HCC converter station is total The following formula should be satisfied:

[0107]

[0108] in:

[0109] Q totalIt indicates the total reactive power (Mvar) that E-STATCOM can provide under the normal operating voltage of the AC busbar of the E-HCC converter station. In the E-HCC converter station, E-STATCOM is used to partially or completely replace the traditional capacitors. The total capacitive reactive capacity refers to the reactive capacity of all equipment such as capacitors and E-STATCOM. The embodiment of the present invention adopts a full replacement scheme, and "filter" and "shunt capacitor" can be replaced by "E-STATCOM", so Q here total It means the total reactive power that E-STATCOM can provide under the normal operating voltage of the AC bus of the E-HCC converter station.

[0110] Q ac It represents the reactive power demand of the AC system assumed when determining the capacity of the reactive power supply equipment (if the value is negative, it indicates the ability of the AC system to provide reactive power to the converter station, Mvar); the AC system here and below refers to the entire regional AC power system where the E-HCC converter station of the embodiment of the present invention is located, that is, it refers to the entire receiving end system connected to the AC outgoing line of the E-HCC converter station, which can be equivalent to an AC power source.

[0111] Q dc It represents the reactive power demand (Mvar) of the DC converter equipment assumed when determining the reactive power supply equipment; the DC converter equipment here and below refers to the HCC converter valve that realizes DC-AC inversion, that is, Figure 3 Middle converter valve part.

[0112] m represents the reserve coefficient. In this embodiment, m takes a value greater than 1, and the extra reactive capacity is used to provide additional reactive power to the system;

[0113] k1 represents the corresponding voltage correction coefficient.

[0114] Total inductive reactive capacity Q of E-HCC converter station r The following formula should be satisfied:

[0115]

[0116] in:

[0117] Q r It indicates the total reactive power (Mvar) that can be absorbed by E-STATCOM under the normal operating voltage of the AC busbar of E-HCC converter station;

[0118] Q acmax It indicates the maximum reactive power (Mvar) allowed to flow from the E-HCC converter station into the AC system when calculating the reactive power absorption equipment; here Q acmax It is the maximum boundary of reactive power allowed in an AC system and is the operating boundary value.

[0119] Qfmin Indicates the reactive power (Mvar) generated by other equipment under the normal operating voltage of the AC busbar of the E-HCC converter station;

[0120] Q dc It represents the reactive power demand (Mvar) of the DC converter equipment assumed when determining the reactive power supply equipment;

[0121] k2 represents the corresponding voltage correction coefficient.

[0122] As a preferred technical solution, determining the active capacity of the E-STATCOM includes: calculating the virtual inertia of the E-STATCOM, and determining the output power of the E-STATCOM based on the response time of a frequency modulation; and determining the active capacity of the E-STATCOM based on the output power of the E-STATCOM.

[0123] For the active capacity of E-STATCOM, it is necessary to consider the maximum power and energy storage capacity of the E-STATCOM equipment. Because the main function of E-STATCOM is to achieve inertia support rather than participate in primary frequency modulation, its operating characteristics are that it can respond quickly when disturbances occur in the AC power grid and provide a large amount of active power in a short time, that is, to achieve the access of virtual inertia. Therefore, the size of the virtual inertia of E-STATCOM can be considered first, and then the output power of E-STATCOM can be determined based on the response time of primary frequency modulation.

[0124] After determining the output power of E-STATCOM, it is convenient to further determine the active capacity of E-STATCOM. Simply put, if E-STATCOM is simply regarded as a battery, the output power is the active power P (MW) of the device, and the active capacity refers to the energy E stored in the device that can be used to continuously output active power within a certain period of time (a few tenths of a second or 1-2 seconds), which can be roughly understood as E = Pt (t is the output time).

[0125] The above technical solution will be further explained below.

[0126] For an AC power grid (AC power system), its frequency change satisfies the following formula:

[0127]

[0128] Among them, E sys is the energy form of the equivalent inertia of the system, in MW·s, where E sys Refers to the actual inertia of the system when the power system response model is established; f N and Δf(t) are the system rated frequency and system frequency deviation respectively; t is time; D is the damping coefficient; PL is the system load level; ΔP G (t) is the primary frequency modulation response power of the unit; ΔP loss is the unbalanced active power of the system. The above formula reveals the relationship between the inertia of the power system and the frequency response of the power system, and is an important reference for system capacity design. The essence of this formula is that when there is unbalanced power in the system, the rotor energy of the thermal power unit can supplement this part in a short time to maintain the system frequency. The inertia of the thermal power unit E sys =S N T J , where S N is the rated power of the unit, T J is the inertia time constant, which is the time it takes for the rotor to decelerate to 0 when the unit outputs rated power. The above formula belongs to the prior art and will not be described in detail here.

[0129] It should be noted that the system mentioned in the embodiment of the present invention refers to the entire regional AC power system (grid) where the converter station (ie, E-HCC converter station) concerned in this embodiment is located.

[0130] To determine the minimum inertia requirement of the system, the main indicators are to consider the maximum rate of change of frequency (RoCoF) and the maximum frequency deviation of the system. In this embodiment, the minimum inertia requirement of the system is determined according to the maximum rate of change of frequency and the maximum frequency deviation of the system.

[0131] Usually the maximum frequency change rate occurs at the moment the disturbance occurs, so the minimum inertia requirement of the system is:

[0132]

[0133] Among them, RoCoF max is the maximum frequency change rate required by the system.

[0134] Considering a frequency modulation action, in order to make the maximum frequency deviation of the system not exceed the requirement (that is, the requirement for the maximum change rate of the AC power grid frequency f, the maximum change rate of the frequency f can be understood as df / dt, which is usually determined by the local power grid management department), the minimum inertia requirement of the system is:

[0135]

[0136] Among them, R N R is the maximum output power of a primary frequency modulation device such as an electrochemical energy storage device with a faster response speed (i.e., a fast response primary frequency modulation device). G The maximum output power of a synchronous machine with a slower response speed. s With T gThe response time of the fast-responding primary frequency modulation equipment and the synchronous machine (i.e. the synchronous machine with a slower response speed) to reach the maximum output power; Δf max is the maximum frequency deviation allowed by the system.

[0137] For the two inequalities of the minimum inertia requirement of the above system, although both focus on the frequency stability of the AC power grid, they use different indicators. The first is the maximum rate of change of the frequency f, which can be understood as df / dt, and the second is the maximum deviation of the frequency f, that is, the difference between the frequency f and the rated value f during the whole process of power fluctuation of the power grid. N Considering these two indicators, the minimum requirements for system inertia are given respectively.

[0138] In this embodiment, the constraint of the minimum inertia requirement of the system can be obtained according to the two inequalities of the minimum inertia requirement of the system. Specifically, the minimum inertia requirement of the system must simultaneously satisfy the two inequalities of the minimum inertia requirement of the system. By sorting out these two inequalities, E sys The minimum value constraint of is used to determine the minimum inertia requirement of the system.

[0139] Considering the above-mentioned minimum inertia requirement of the system, deducting the inertia of the existing synchronous machine in the system is the virtual inertia (energy form) that the E-STATCOM needs to have. In this embodiment, the virtual inertia that the E-STATCOM needs to have is obtained by subtracting the inertia of all conventional units in the system from the minimum inertia requirement of the system, which can be expressed as:

[0140] E E-STATCOM =E sys -E g

[0141] Among them, E E-STATCOM It is the virtual inertia required by E-STATCOM. sys is the inertia demand of the system. Here, the above-mentioned power system response model is used to determine the system inertia demand. Here, E sys Refers to the inertia that the system needs to have when meeting the frequency change requirements. It is the result calculated after other parameters in the formula (i.e., the power system response model) are determined. g is the inertia of all conventional units in the system. The inertia of the existing synchronous machines in the system is E g It is related to the grid-connected capacity of existing thermal power units in the system.

[0142] Considering the response time of the fast-response primary frequency modulation equipment, the E-STATCOM needs to continuously provide active power support before it reaches the maximum power. Therefore, the power output time of the E-STATCOM is T s , its maximum output power is E E-STATCOM / Ts , where E E-STATCOM Indicates the virtual inertia that the E-STATCOM needs to have, T s The time it takes for a frequency modulation device to reach its maximum output power quickly.

[0143] Simply put, E-STATCOM has certain similarities with batteries. The inertia of E-STATCOM refers to the total energy (J) stored in E-STATCOM, and the output power of E-STATCOM is the maximum output electric power of the E-STATCOM device P=UI, which actually determines the maximum output current of the E-STATCOM device.

[0144] Based on the same inventive concept, the present invention also provides a computer-readable storage medium storing one or more programs, which, when executed, can implement the aforementioned E-STATCOM capacity configuration method.

[0145] Based on the same inventive concept, Figure 5 As shown, the present invention also provides an electronic device, including a processor, a communication interface, a computer-readable storage medium as described above, and a communication bus; wherein the processor, the communication interface, and the computer-readable storage medium communicate with each other via the communication bus; and the processor is used to execute the program stored in the computer-readable storage medium.

[0146] It should be noted that, for the convenience of description, the aforementioned method embodiments are all described as a series of action combinations, but those skilled in the art should be aware that the present invention is not limited by the described action sequence, because according to the present invention, certain steps can be performed in other sequences or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in the specification are all preferred embodiments, and the actions involved are not necessarily required by the present invention.

[0147] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0148] Parts not involved in the above embodiments are the same as the prior art or can be implemented by using the prior art, and will not be further described here.

[0149] Although the present invention 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 substitutions for some of the technical features therein; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An E-HCC converter station, characterized in that: The system comprises a converter transformer, an HCC converter valve and an E-STATCOM. The converter valve side of the converter transformer is connected to the HCC converter valve, and the AC power grid side of the converter transformer is connected to the E-STATCOM.

2. The E-HCC converter station according to claim 1, characterized in that: The E-STATCOM is connected to the AC grid side of the converter transformer using a step-up transformer.

3. The E-HCC converter station according to claim 2, characterized in that: The voltage level of the AC grid side of the converter transformer is 500 kV, and the voltage level of the converter valve side of the converter transformer is 100 kV; The E-STATCOM is a 35kV energy storage device and is connected to the receiving-end AC power grid using the step-up transformer.

4. An E-HCC converter station according to any one of claims 1 to 3, characterized in that: The E-STATCOM includes a plurality of SM energy storage units connected in series, wherein the SM energy storage unit includes an H-bridge power module and a super capacitor, and the super capacitor forms an energy storage device through the H-bridge power module.

5. An E-STATCOM capacity configuration method, applied to the E-HCC converter station according to any one of claims 1 to 4, characterized in that: The method comprises: The capacity of the E-STATCOM is determined according to the reactive power demand of the HCC converter valve and the active and reactive power demand of the receiving-end AC power grid. The capacity of the E-STATCOM includes active capacity and reactive capacity.

6. The E-STATCOM capacity configuration method according to claim 5, characterized in that: Determining the reactive capacity of the E-STATCOM includes: Calculate the total capacitive reactive capacity Q of the E-HCC converter station total ; Calculate the total inductive reactive capacity Q of the E-HCC converter station r ; Compare the total capacitive reactive capacity Q total The total inductive reactive capacity Q r and the larger of the two is taken as the reactive capacity of the E-STATCOM.

7. The E-STATCOM capacity configuration method according to claim 6, characterized in that: The total capacitive reactive capacity Q total satisfy: in: Q total It indicates the total reactive power that E-STATCOM can provide under the normal operating voltage of the AC busbar of E-HCC converter station; Q ac It represents the reactive power demand of the AC system assumed when determining the capacity of the reactive power supply equipment; Q dc It represents the reactive power demand of the DC converter equipment assumed when determining the reactive power supply equipment; m represents the reserve coefficient; k1 represents the corresponding voltage correction coefficient.

8. The E-STATCOM capacity configuration method according to claim 6, characterized in that: The total inductive reactive capacity Q r satisfy: in: Q r It indicates the total reactive power that can be absorbed by E-STATCOM under the normal operating voltage of the AC busbar of E-HCC converter station; Q acmax It indicates the maximum reactive power allowed to flow from the converter station into the AC system when calculating reactive power absorption equipment; Q fmin Indicates the reactive power generated by other equipment under the normal operating voltage of the AC busbar of the E-HCC converter station; Q dc It represents the reactive power demand of the DC converter equipment assumed when determining the reactive power supply equipment; k2 represents the corresponding voltage correction coefficient.

9. The E-STATCOM capacity configuration method according to claim 5, characterized in that: Determining the active capacity of the E-STATCOM includes: Calculating the virtual inertia of the E-STATCOM, and determining the output power of the E-STATCOM according to the response time of a primary frequency modulation; The active capacity of the E-STATCOM is determined according to the output power of the E-STATCOM.

10. The E-STATCOM capacity configuration method according to claim 9, characterized in that: The calculating of the virtual inertia of the E-STATCOM comprises: Determine the minimum inertia requirement of the system based on the maximum frequency change rate and maximum frequency deviation of the system; The virtual inertia required for the E-STATCOM is obtained by subtracting the inertia of all conventional units in the system from the system's minimum inertia requirement.

11. The E-STATCOM capacity configuration method according to claim 10, characterized in that: Determining the minimum inertia requirement of the system according to the maximum frequency change rate and the maximum frequency deviation of the system includes: According to the maximum frequency change rate of the system, the minimum inertia requirement of the system is: According to the maximum frequency deviation of the system, the minimum inertia requirement of the system is: Among them, E sys is the energy form of the system equivalent inertia, in MW·s; f N is the system rated frequency; RoCoF max is the maximum frequency change rate required by the system; ΔP loss is the unbalanced active power of the system; R N To quickly respond to the maximum output power of a frequency modulation device; R G It is the maximum output power of a synchronous machine with a slower response speed. T s With T g They are the response time for a fast-responding primary frequency modulation device and a slower-responding synchronous machine to reach maximum output power; Δf max is the maximum frequency deviation allowed by the system; According to the two inequalities of the minimum inertia requirement of the system mentioned above, the constraint of the minimum inertia requirement of the system can be obtained, and then the minimum inertia requirement of the system can be determined.

12. The E-STATCOM capacity configuration method according to claim 11, characterized in that: The frequency change of the system satisfies the following formula: Among them, E sys is the energy form of the system equivalent inertia, in MW·s; f N and Δf(t) are the system rated frequency and system frequency deviation respectively; t is time; D is damping coefficient; PL is system load level; ΔP G (t) is the primary frequency modulation response power of the unit; ΔP loss is the unbalanced active power of the system.

13. The E-STATCOM capacity configuration method according to claim 10, characterized in that: The output power of the E-STATCOM is E E-STATCOM / T s , where E E-STATCOM Indicates the virtual inertia that the E-STATCOM needs to have, T s The time it takes for a frequency modulation device to reach its maximum output power quickly.

14. A computer-readable storage medium storing one or more programs, characterized in that: When the one or more programs are executed, the E-STATCOM capacity configuration method described in any one of claims 5-13 can be implemented.

15. An electronic device comprising a processor, a communication interface, the computer-readable storage medium of claim 14, and a communication bus; wherein: The processor, the communication interface, and the computer-readable storage medium communicate with each other via a communication bus; It is characterized in that The processor is configured to execute a program stored in a computer-readable storage medium.

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