Active support control method and system based on energy storage type static synchronous phase modifier

Abstract

The invention belongs to the field of energy storage type static reactive compensation, and particularly relates to an active support control method and system based on an energy storage type static synchronous phase modifier. Comprising the following steps: calculating a voltage reference value according to an MMC AC voltage angle and an MMC voltage reference amplitude; the angle is obtained by performing virtual synchronous control according to the difference between the reference power and the actual power exchanged between the energy storage valve and the power grid during network construction control; obtaining a current reference value by combining the virtual impedance according to the difference between the reference value and the actual voltage; taking the voltage reference value as a feedforward, and superposing the voltage reference value to an output result obtained by carrying out PR control or PI control on the difference between the current reference value and an actual value to obtain the modulation quantity of the internal potential of the alternating current side; taking the current instruction value as a feedforward, superposing the current instruction value to an output result of PI control performed by the difference between the reference voltage and the average voltage, and performing PI control according to the superposition result and the difference between the current of the energy storage valve bus to obtain a reference voltage value; and generating an instruction for controlling the voltage of each bridge arm of the MMC according to the modulation quantity and the reference voltage value.

Description

Technical Field

[0001] The present invention belongs to the field of energy storage type static reactive power compensation, and in particular relates to an active power support control method and system based on an energy storage type static synchronous condenser. Background Art

[0002] A synchronous compensator (SC, sometimes also referred to as an SSC) is a specialized power electronic device that converts DC power into AC power through a power electronic converter and controls the amplitude and phase of the output voltage, thereby enabling continuous and rapid regulation of reactive power in the power grid. When the grid voltage drops, the SC can provide voltage support, preventing voltage collapse and improving power system stability.

[0003] Static synchronous condensers include energy-storage static condensers (also commonly known as static VAR generators (SVGs)). These SVGs can provide or absorb reactive and active power to the power system, effectively regulating the grid voltage. When grid voltage drops, SVGs provide voltage support, preventing voltage collapse and improving power system stability. When grid voltage rises, SVGs absorb reactive power, further balancing the grid voltage. This rapid response to reactive power makes SVGs a crucial tool for grid voltage regulation.

[0004] An existing energy storage type static synchronous condenser topology is as follows Figure 1 As shown, the AC side uses a hybrid bridge / half-bridge / full-bridge cascaded MMC topology. The DC side of the MMC is connected to a half-bridge cascaded energy storage valve. Each link of the energy storage valve consists of a half-bridge power unit and a supercapacitor, which are connected via an interface circuit.

[0005] Currently, nearly all grid-connected energy storage-type static synchronous condensers (SSCs) employ a virtual synchronous control strategy for inertial frequency support. The core of this virtual synchronous control strategy is to simulate the operating characteristics of synchronous generators, including their inertia and damping properties. Through power electronics and advanced control algorithms, distributed energy generation systems (such as solar photovoltaic and wind power) can participate in power system regulation, including frequency regulation, voltage regulation, and power control, just like synchronous generators. However, this approach to inertial frequency support using a virtual synchronous control strategy typically fails to consider the adaptive coordination between supercapacitors, hybrid bridge cascade SSCs, and the power grid to adjust to frequency fluctuations during the frequency support process. This approach significantly impacts the accuracy and reliability of active frequency support, as it involves adaptive coordination between the supercapacitors, hybrid bridge cascade SSCs, and the power grid to adjust to these frequency fluctuations. This means that after frequency fluctuations, the energy exchange and control between each of the three components continues to follow the previous approach, without adaptive adjustments to the frequency fluctuations. Summary of the Invention

[0006] The purpose of the present invention is to provide an active power support control method and system based on an energy storage type static synchronous condenser, which is used to solve the problem in the prior art that when the frequency changes during the inertial frequency support process, it is difficult to adaptively coordinate and adjust the control of active power support between supercapacitors, hybrid bridge cascade static synchronous condensers and the power grid, thereby seriously affecting the accuracy and reliability of active power support.

[0007] In order to achieve the above object, the present invention provides an active power support control method based on an energy storage type static synchronous condenser, the method comprising:

[0008] Calculating a three-phase voltage reference value or a dq-axis voltage reference value based on the MMC AC side voltage angle and the obtained reference amplitude of the MMC AC side voltage of the phase regulator; the angle is obtained by performing virtual synchronization control based on the difference between the required power on the MMC AC side and the actual power exchanged between the energy storage valve of the phase regulator and the grid under grid control;

[0009] Based on the difference between the three-phase voltage reference value or the dq-axis voltage reference value and the actual voltage on the AC side of the MMC, the three-phase current reference value or the dq-axis current reference value on the AC side is obtained in combination with the virtual impedance; the calculated three-phase AC voltage reference value or the dq-axis voltage reference value is used as feedforward and superimposed on the output result of PR control or PI control of the difference between the three-phase current reference value or the dq-axis current reference value on the AC side and the actual three-phase current value or the dq-axis current value on the AC side, to obtain the modulation amount of the internal potential on the AC side;

[0010] A preset DC current command value is used as feedforward, and is superimposed on the output result of PI control based on the difference between the reference voltage of the submodule of the MMC and the average voltage of the submodule. PI control is then performed based on the difference between the superimposed result and the DC current on the bus where the energy storage valve is located to obtain a reference DC voltage value;

[0011] A control instruction for controlling the voltage of each bridge arm of the phase modulator MMC is generated according to the modulation amount and the reference DC voltage value.

[0012] Beneficial effect: The present invention provides a new active support control method based on an energy storage type static synchronous phase regulator. The main idea of ​​the method is to generate a control instruction for controlling the voltage of each bridge arm according to the modulation amount of the acquired internal potential of the AC side and the reference DC voltage value, so as to realize the control of the voltage of each bridge arm, thereby realizing the effect of accurate exchange of energy with the balance of current between the power grid, the MMC of the phase regulator and the energy storage valve when the energy storage type static synchronous phase regulator performs active support (the energy exchange is actually carried out between any two of the above three, that is, between the power grid and the phase regulator MMC; between the phase regulator MMC and the energy storage valve).

[0013] Among them, the modulation amount of the internal potential on the AC side utilizes the result of virtual synchronous control of the difference between the power actually required on the AC side of the MMC and the actual power exchanged between the energy storage valve and the AC power grid, combined with current loop control to obtain; thereby, it can ensure that the actual power exchanged between the energy storage valve of the phase regulator and the power grid is as close as possible to the required power on the AC side, thereby ensuring from the source that the active power support of the power grid is more accurately achieved through the energy storage valve of the phase regulator, so that the energy exchange between the energy storage valve and the MMC (i.e., the DC side) can be accurately and reliably achieved according to the needs of the power grid.

[0014] The reference DC voltage value is obtained by performing PI control using the difference between the reference voltage of the MMC submodule and the average voltage of the submodule, and combining it with the difference between the DC current on the bus where the energy storage valve is located after superimposing the feedforward (i.e., the preset DC current command value) to perform PI control. This ensures that the average voltage of the MMC submodule is as close as possible to the reference voltage of the MMC submodule, thereby minimizing the charging or discharging of the MMC of the phase regulator during the energy exchange between the energy storage valve of the phase regulator and the power grid, thereby affecting the accuracy of the energy exchange power between the energy storage valve of the phase regulator and the power grid. This enables accurate and reliable control of the energy exchange between the MMC and the power grid (i.e., the AC side).

[0015] In summary, the control instructions for controlling the current in each bridge arm are generated based on the reference DC voltage value and the modulation wave of the internal potential on the AC side. That is, the energy control on the DC side and the AC side is comprehensively considered to accurately and reliably control the energy flow of the entire power grid, thereby ensuring the efficient transmission and reasonable distribution of electric energy in the entire power grid, which can help reduce power loss and improve the overall efficiency of the power grid.

[0016] Furthermore, PI control is performed according to the difference between the set rated DC voltage value of the energy storage valve and the DC voltage of the bus where the energy storage valve is located to obtain the number of submodules that have been put into operation;

[0017] The number of submodules initially pre-invested is used as feedforward and added to the number of submodules already invested to obtain the number of submodules that need to be invested;

[0018] According to the number of submodules that need to be put into operation, a control instruction for controlling each submodule of the phase modulator MMC to be put into operation or cut out is generated.

[0019] Furthermore, the method for obtaining the reference amplitude of the AC side voltage of the phase modulator MMC includes: performing droop control based on the difference between the reference voltage of 1 times the per-unit value and the actual voltage of the power grid, and superimposing it with the AC voltage reference value feedforward term to obtain the reference amplitude of the AC side voltage of the phase modulator MMC.

[0020] Furthermore, it also includes: when the system frequency decreases, if the obtained voltage of a single energy storage valve is less than or equal to the voltage value corresponding to the maximum duration of active support of the single energy storage valve, then it is determined that the current control situation is a grid-following control situation; under the grid-following control situation, the angle is obtained by the actual angular velocity of the grid in unit.

[0021] Furthermore, it also includes: when the system frequency rises, if the voltage of a single energy storage valve is greater than or equal to the maximum voltage value of the single energy storage valve, it is determined that the current control situation is a grid-following control situation; under the grid-following control situation, the angle is obtained through the per-unit grid synchronization angular velocity.

[0022] Furthermore, the method for obtaining the voltage of a single energy storage valve includes: correcting the sampled voltage of the single energy storage valve by subtracting the internal resistance voltage drop of the energy storage valve from the sampled voltage of the single energy storage valve, and using the corrected internal potential of the energy storage valve as the voltage of the single energy storage valve.

[0023] The present invention also provides an active power support control system based on an energy storage type static synchronous condenser, comprising a processor for executing a computer program to implement the steps of the above-mentioned active power support control method based on an energy storage type static synchronous condenser.

[0024] The active power support control system based on the energy storage type static synchronous condenser can achieve the same beneficial effects as the active power support control method based on the energy storage type static synchronous condenser described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A system topology diagram of an energy storage type static synchronous condenser in the background technology of the present invention;

[0026] Figure 2 This is a control principle diagram for obtaining the voltage angle of the MMC AC side in an embodiment of the active power support control method based on an energy storage type static synchronous condenser of the present invention;

[0027] Figure 3 This is a control principle diagram for obtaining a reference amplitude of the AC side voltage of the condenser MMC in an embodiment of the active power support control method based on an energy storage type static synchronous condenser of the present invention;

[0028] Figure 4 This is a control principle diagram for obtaining the AC side three-phase current reference value in an embodiment of the active power support control method based on an energy storage type static synchronous condenser of the present invention;

[0029] Figure 5 This is a control principle diagram for obtaining AC side dq axis current reference values ​​in an embodiment of the active power support control method based on an energy storage type static synchronous condenser of the present invention;

[0030] Figure 6 This is a control principle diagram for generating control instructions for controlling the voltages of each bridge arm of the condenser MMC in an embodiment of the active power support control method based on an energy storage type static synchronous condenser of the present invention;

[0031] Figure 7 This is a control principle diagram for generating control instructions for controlling the switching on or off of each submodule of the supercapacitor valve of the energy storage type static synchronous condenser in an embodiment of the active support control method of the present invention. DETAILED DESCRIPTION

[0032] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0033] Active power support control method embodiment based on energy storage type static synchronous condenser

[0034] This embodiment provides a technical solution for a method for controlling active power support of an energy storage-type static synchronous condenser. The method's main concept is to derive control instructions for controlling the voltages of each bridge arm based on the acquired modulation of the AC side internal potential and a reference DC voltage value. This instruction achieves the effect of controlling the balanced flow of energy in the entire power grid system containing the energy storage-type static synchronous condenser by controlling the voltages of each bridge arm. In practice, the modulation of the AC side internal potential accurately represents the energy exchange between the MMC and the power grid, while the reference DC voltage accurately represents the energy exchange between the energy storage valve and the MMC. Therefore, by comprehensively considering these two parameters to obtain the control variable (i.e., calculating the control variable for each bridge arm voltage of the condenser MMC based on these two parameters), this method can achieve balanced control of the energy flow between the MMC and the power grid, and between the energy storage valve and the MMC (actually, representing the energy flow through current flow).

[0035] In this embodiment, the three-phase voltage reference value needs to be calculated based on the MMC AC side voltage angle θ and the obtained reference amplitude U of the phase regulator MMC AC side voltage. Figure 2 As shown, the specific method of obtaining the voltage angle of the MMC AC side includes: the angle θ is in the grid control state (the grid control state is the state when Modef is in ω, and the specific time when the grid control state is in place can be set according to the corresponding judgment conditions or flexibly set by other methods according to actual needs) according to the required power P* of the MMC AC side and the energy storage valve of the phase regulator (i.e. Figure 1 The energy storage submodule in the power grid, which contains supercapacitors, is actually achieved by virtual synchronization control based on the difference between the actual power P exchanged between the supercapacitor valve and the grid. The term "grid" here refers to a different concept than the broader grid, but rather to the grid that provides active power support for the phase-shifting module, or the grid on the AC side of the phase-shifting MMC.

[0036] The MMC AC side voltage angle θ is obtained based on the angular frequency ω output by the virtual synchronous control (i.e., to obtain the angle θ, the angular frequency ω must be calculated first). The equation for calculating the angular frequency ω (i.e., the rotor motion equation) is as follows:

[0037]

[0038] Among them, T J is the inertia time constant of the synchronous condenser; ω is the angular frequency of the stationary synchronous condenser per unit; P m is the reference active power of the synchronous condenser per unit; P e is the actual power of the synchronous condenser per unit; D P=Dω0 is the equivalent damping coefficient of the static synchronous condenser (the damping factor D mainly considers the fitting and adjustment of the overall damping characteristics of the synchronous condenser); ω0 is the per-unit synchronous angular velocity of the power grid.

[0039] After obtaining the angular frequency ω output by the virtual synchronous control, the angular frequency ω is integrated to obtain the voltage angle θ on the AC side of the MMC.

[0040] like Figure 3 As shown, this embodiment obtains the reference amplitude U of the AC side voltage of the phase modulator MMC. The specific acquisition method includes: according to the reference voltage of 1 times the per unit value (ie Figure 3 The reference voltage represented by the input '1' in the input is obtained based on the rated voltage of the AC side) and the actual voltage of the grid U fd The difference between the two is used for droop control (i.e. Figure 3 Ku in the figure represents the droop control), and the AC voltage reference value feedforward term U ref (This reference value is the command value issued by the superior. After the reference value is normalized, it is usually 1 pu, but it can also be 1.1 pu or above. This reference value is also the rated voltage value of the AC side.) The reference amplitude of the AC side voltage of the phase regulator MMC is obtained by adding it. In addition, other control modes can be switched to through Mode U. The control mode shown in the figure is to adjust the reactive power command value Q ref The difference from the actual reactive power Q is controlled by PI control. In other embodiments, ModeU can be switched to any other control mode that can obtain the reference amplitude U of the AC side voltage.

[0041] like Figure 4 as well as Figure 5 As shown, after obtaining the MMC AC side voltage angle θ and the reference amplitude U of the phase regulator MMC AC side voltage, the three-phase voltage reference value or the dq-axis voltage reference value is calculated based on these two parameters (that is, θ and U are used as inputs for calculating the three-phase AC voltage reference value or the dq-axis voltage reference value). gabc Or the actual value of the dq axis voltage U gdq The difference between them is combined with the virtual impedance corresponding to the controller to obtain the AC side three-phase current reference value or the dq axis current reference value.

[0042] Specifically, the virtual impedance is not a real impedance. It is obtained by debugging the active support speed of frequency changes and the reactive current response speed and reactive output value during fault ride-through. If the value of the virtual impedance is set too small, it will lead to unstable current in the system steady state or during fault ride-through. If it is set too large, the fault current response speed will be too slow. Therefore, this value needs to be adaptively set based on engineering experience. It is specifically expressed as Figure 4 as well as Figure 5 1 / (R+sL) in the equation, and then calculate the AC side three-phase current reference value through current vector limiting, which is Figure 4 The A phase current reference value i shown in a_ref , B phase current reference value i b_ref and C phase current reference value i c_ref ,or Figure 5 The dq axis current reference value shown in d_ref and i q_ref .

[0043] like Figure 6 As shown, the calculated three-phase AC voltage reference value (i.e. U a_qk 、U b_qk and U c_qk ) is the feedforward, which is added to the three-phase current reference value on the AC side (i.e. a_ref 、i b_ref and i c_ref ) and the actual value of the three-phase current on the AC side (i.e., ia, ib, and ic) to perform PR control or use the calculated dq axis voltage reference value (i.e., U d_qk 、U q_qk ) as feedforward, superimposed on the dq axis current reference value (i d_ref 、i q_ref ) and the actual value of the AC side dq axis current (i.e., id, iq) are used to perform PI control and then the output result of the dq coordinate system to abc coordinate system transformation is obtained to obtain the modulation amount m of the internal potential of the AC side. abc At the same time, the preset DC current command value I dc * is feedforward, superimposed on the reference voltage U of the submodule according to the MMC smref and the average voltage of the submodule U smavg The difference between the output result of PI control I d *, which is about to dc * and I d * to obtain the corresponding superposition result; then, according to the superposition result and the DC current i on the bus where the energy storage valve is located d The difference between them is PI controlled to obtain the reference DC voltage value U dcref ; According to the modulation amount m abc And the reference DC voltage value U dcref , generating control instructions for controlling the voltage of each bridge arm of the phase regulator MMC.

[0044] Specifically, this embodiment first determines the modulation amount m abc And the reference DC voltage value U dcrefAddition and subtraction operations are performed to output six bridge arm voltage commands, which are then converted through the NLM into control commands PWM1. These control commands are used to control the voltages of each bridge arm of the phase-shifting module (MMC). The reference DC voltage of the hybrid bridge MMC forms a DC voltage difference with the DC voltage of the energy storage valve. The energy storage valve outputs a DC current to the MMC, controlling the flow of active power from the energy storage valve to the MMC. The MMC itself does not store active power, and the active power is then transferred to the grid through the MMC submodule average voltage control loop. This embodiment uses a comprehensive control system to achieve accurate energy exchange across the entire power grid system.

[0045] The above method actually controls the current flow in the power grid system by controlling the voltage of each bridge arm of the phase regulator MMC to achieve accurate transmission of active power (i.e., accurate and reliable active power support). However, since active power not only needs to consider current factors, but also voltage factors; therefore, it is also necessary to Figure 1 The DC voltage U on the bus where the energy storage valve is located (i.e. the bus between the hybrid bridge MMC and the energy storage valve) dc The control method adopted in this embodiment is to accurately switch the MMC submodule on or off after relevant calculations.

[0046] like Figure 7 As shown, the control method specifically includes: according to the set energy storage valve rated DC voltage value U dc_ref The DC voltage U of the busbar where the energy storage valve is located dc The difference between them is controlled by PI to obtain the number N of sub-modules that have been put into use.

[0047] The number of submodules initially pre-invested For feedforward, add it to the number of submodules N that have been put into use to get the number of submodules n that need to be put into use, and limit n to make it less than or equal to the maximum number of submodules N Max , and will soon and N are superimposed to obtain n(n≤N Max ).

[0048] According to the number of submodules n that need to be put into operation, a control instruction PWM2 is generated for controlling the submodules of the energy storage valve of the phase regulator to be put into operation or cut out. The control instruction PWM2 (which is actually the instruction for controlling the submodule to be put into operation or cut out) is used to control the submodule to be put into operation or cut out, so that U dc In summary, combined with the dual control of current and voltage in the power grid system, it is possible to control the energy storage type static synchronous condenser to provide accurate and reliable active power support.

[0049] In addition, due to the limited capacity of the overcapacity valve (i.e., the energy storage valve), the overcapacity voltage value may be too low or too high during the active power support process, resulting in over-discharge or over-charge. Therefore, the following methods are adopted in this embodiment:

[0050] When the system frequency f decreases, if the voltage U of a single energy storage valve is obtained t Less than or equal to the voltage value U corresponding to the maximum duration of active support of a single energy storage valve t1 , the current control situation is determined to be grid-following control; in this case, the MMC AC-side voltage angle θ is obtained using the per-unit actual grid angular velocity ω0. It should be noted that in this embodiment, if the current control situation is not determined to be grid-following control, it indicates that the current control situation is grid-forming control, i.e., θ is determined using the angle method described above for grid-forming control.

[0051] Specifically, when the system frequency changes, the active power value of the static synchronous condenser that provides inertial support to the grid is calculated as follows:

[0052]

[0053] Among them, P N is the rated active power of the synchronous condenser; f0 is the rated frequency of the static synchronous condenser; f is the system change frequency; T J is the inertia time constant of the synchronous condenser. Assuming that when the system frequency decreases, the duration of the static synchronous condenser's active power support is t1, the energy E1 output by the excess capacity valve (i.e., the energy storage valve) during the duration t1 is calculated as follows:

[0054] Where N is the number of submodules of the supercapacitor valve; C is the supercapacitor capacitance value connected to a single submodule of the supercapacitor valve; U0 is the rated supercapacitor voltage value of a single supercapacitor valve; U t1 The voltage value corresponding to the maximum duration of active power support for a single over-capacity valve.

[0055] Specifically, when the frequency drops, the static synchronous condenser outputs active power to the grid. At this time, the voltage U t Gradually decrease, when U t Down to meet U t ≤U t1 If the condition is met, the current control situation is determined to be the grid-following control situation. At this time, the Modef in the virtual synchronization control strategy is switched to the synchronization angular frequency ω0 of the grid, and the virtual synchronization control (i.e., active power support) is no longer performed. Figure 2 As shown, in this case, the MMC AC side voltage angle θ is obtained according to the per-unit grid synchronous angular velocity ω0. Since U t ≤U t1Active power support is stopped when the system frequency rises, thus preventing over-discharge of the over-capacity valve. In this embodiment, when the system frequency rises, if the voltage of a single energy storage valve is greater than or equal to the maximum voltage of the single energy storage valve, the current control state is determined to be grid-following control. In the grid-following control state, the MMC AC-side voltage angle θ is obtained by the per-unit grid synchronization angular velocity.

[0056] Similarly, assuming that when the system frequency rises, the duration of the static synchronous condenser's active power support is t2, then the energy E2 output by the energy storage valve during the duration t2 is calculated as follows:

[0057]

[0058] Among them, U t2 is the maximum voltage value of a single over-capacity valve; the meanings of other parameters are consistent with the above and are not repeated here.

[0059] Specifically, when the frequency rises, the static synchronous condenser absorbs active power from the grid. At this time, the voltage of the over-capacity valve gradually increases. t Rise to meet U t ≥U t2 If the condition is met, the current control situation is determined to be the grid-following control situation. At this time, the Modef in the virtual synchronization control strategy is switched to the synchronization angular frequency ω0 of the grid, and the virtual synchronization control (i.e., active power support) is no longer performed. Figure 2 As shown, in this case, the MMC AC side voltage angle θ is obtained according to the per-unit grid synchronous angular velocity ω0. t ≥U t2 Active power support is stopped at this time, so overcharging of the overcapacity valve can be avoided in this way.

[0060] In this embodiment, the method for obtaining the voltage of a single energy storage valve includes: correcting the sampled voltage of the single energy storage valve (the sampled voltage includes the internal resistance voltage drop) by reducing the internal resistance voltage drop, and using the corrected internal potential of the energy storage valve as the voltage of the single energy storage valve.

[0061] Specifically, since only the sampling voltage U of a single energy storage valve can be collected when sampling the voltage of the supercapacity valve, t , U t The voltage drop across the internal resistance is included in the voltage drop, which will be affected by the current value. Therefore, the sampling voltage U of the over-capacity valve can be t Correction is performed by directly sampling the voltage U of a single energy storage valve t It can be expressed as:

[0062] U t =U t0 +I limR cu

[0063] Among them, U t is the sampling voltage of a single energy storage valve (including the internal resistance voltage drop); I lim is the current value of the over-capacity valve; R cu is the internal resistance of a single over-capacity valve; U t0 is the internal potential of the supercapacitor valve.

[0064] The correction method can be summarized from the above formula (ie, obtaining the internal potential U of the supercapacitor valve t0 The following method is used:

[0065] U t0 =U t -I lim R cu

[0066] The above formula means: subtract the internal resistance voltage drop to get the internal potential U of the supercapacitor. t0 , which is used as the voltage of a single energy storage valve, that is, U t0 For U t Corrected results.

[0067] Active power support control system implementation based on energy storage type static synchronous condenser

[0068] This embodiment provides a technical solution for an active power support control system based on an energy storage type static synchronous condenser. The system includes a processor having executable program instructions stored therein. The executable program instructions are used to implement the active power support control method based on an energy storage type static synchronous condenser as described in the embodiment of the active power support control method based on an energy storage type static synchronous condenser.

[0069] Since the specific working mode and working principle of the active power support control system based on the energy storage type static synchronous condenser of this embodiment have been described in detail in the above-mentioned active power support control method embodiment based on the energy storage type static synchronous condenser, they will not be repeated here.

[0070] It should be understood that the above specific embodiments of the present invention are only used to illustrate or explain the principles of the present invention, and do not constitute a limitation of the present invention.

Claims

1. A method for controlling active power support of an energy storage type static synchronous condenser, characterized in that: include: Calculate the three-phase voltage reference value or the dq-axis voltage reference value according to the MMC AC side voltage angle and the obtained reference amplitude of the AC side voltage of the phase regulator MMC; The angle is obtained by virtual synchronization control based on the difference between the power demand on the MMC AC side and the actual power exchanged between the energy storage valve of the phase regulator and the grid under grid control. Based on the difference between the three-phase voltage reference value or the dq-axis voltage reference value and the actual voltage on the AC side of the MMC, the three-phase current reference value or the dq-axis current reference value on the AC side is obtained in combination with the virtual impedance; the calculated three-phase AC voltage reference value or the dq-axis voltage reference value is used as feedforward and superimposed on the output result of PR control or PI control of the difference between the three-phase current reference value or the dq-axis current reference value on the AC side and the actual three-phase current value or the dq-axis current value on the AC side, to obtain the modulation amount of the internal potential on the AC side; A preset DC current command value is used as feedforward, and is superimposed on the output result of PI control based on the difference between the reference voltage of the submodule of the MMC and the average voltage of the submodule. PI control is then performed based on the difference between the superimposed result and the DC current on the bus where the energy storage valve is located to obtain a reference DC voltage value; A control instruction for controlling the voltage of each bridge arm of the phase modulator MMC is generated according to the modulation amount and the reference DC voltage value.

2. The active power support control method based on the energy storage type static synchronous condenser according to claim 1 is characterized in that: PI control is performed based on the difference between the set rated DC voltage value of the energy storage valve and the DC voltage of the bus where the energy storage valve is located to obtain the number of submodules that have been put into use; The number of submodules initially pre-invested is used as feedforward and added to the number of submodules already invested to obtain the number of submodules that need to be invested; According to the number of submodules that need to be put into operation, a control instruction for controlling each submodule of the phase modulator MMC to be put into operation or cut out is generated.

3. The active power support control method based on the energy storage type static synchronous condenser according to claim 1 or 2, characterized in that: The method of obtaining the reference amplitude of the AC side voltage of the phase modulator MMC includes: performing droop control according to the difference between the reference voltage of 1 times the per-unit value and the actual voltage of the power grid, and superimposing it with the AC voltage reference value feedforward term to obtain the reference amplitude of the AC side voltage of the phase modulator MMC.

4. The active power support control method based on the energy storage type static synchronous condenser according to claim 1 is characterized in that: Also includes: When the system frequency decreases, if the voltage of a single energy storage valve obtained is less than or equal to the voltage value corresponding to the maximum duration of active support of the single energy storage valve, it is determined that the current control situation is the grid-following control situation; In the case of grid-following control, the angle is obtained by the per-unit grid synchronization angular velocity.

5. The active power support control method based on the energy storage type static synchronous condenser according to claim 1 is characterized in that: Also includes: When the system frequency rises, if the voltage of a single energy storage valve is greater than or equal to the maximum voltage value of the single energy storage valve, it is determined that the current control state is the grid-following control state; In the case of grid-following control, the angle is obtained by the actual angular velocity of the grid in unitary form.

6. The active power support control method based on the energy storage type static synchronous condenser according to claim 4 or 5, characterized in that: The method of obtaining the voltage of a single energy storage valve includes: correcting the sampled voltage of the single energy storage valve by subtracting the internal resistance voltage drop of the energy storage valve from the sampled voltage of the single energy storage valve, and using the corrected internal potential of the energy storage valve as the voltage of the single energy storage valve.

7. An active power support control system based on an energy storage type static synchronous condenser, comprising a processor, characterized in that: The processor is used to execute a computer program to implement the steps of the active power support control method based on an energy storage type static synchronous condenser according to any one of claims 1 to 6.

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