Energy storage system power constraint control method, energy storage control device and energy storage system

Abstract

The invention discloses an energy storage system power constraint control method, an energy storage control device and an energy storage system. The method comprises the following steps: acquiring operation parameters of a PCS power module; power information coding is carried out according to the operation parameters, a coding result is obtained, and the direct-current bus voltage is controlled through the coding result; acquiring the real-time voltage of the direct-current bus to obtain a monitoring result; and performing power information decoding according to the monitoring result to obtain a decoding result, and performing constraint control on the operation power of each phase of the PCS power module according to the decoding result. The technical problems that an energy storage system in an existing transformer area interconnection system cannot achieve single-phase power accurate control through direct-current droop control, and overload downtime is likely to be caused when three-phase power is unbalanced are solved, and the purposes that under the non-communication condition, single-phase power accurate control is achieved through periodic change of direct-current bus voltage, and overload downtime is likely to be caused are achieved. And meanwhile, the overload risk caused by three-phase power imbalance is solved, and the technical effect of safe operation of the system is ensured.

Description

Technical Field

[0001] The present application relates to the field of microgrids, and in particular to a power constraint control method for an energy storage system, an energy storage control device, and an energy storage system. Background Art

[0002] With the growth of load demand on distribution networks and the widespread access to distributed energy, the power supply quality of distribution networks has become increasingly prominent. In order to optimize the power supply quality, configuring energy storage systems and substation interconnection systems at the end of the power supply line has become a widely adopted solution.

[0003] At present, the energy storage system applied to the interconnected substation system mainly adopts DC droop control to realize the power transfer between substations. Since voltage management usually adopts single-phase independent control mode, and the total active power is exchanged on the DC side, the energy storage system cannot realize the precise control of each single-phase power through DC droop. Especially when there is coexistence of positive and negative power in single-phase power, the existing method cannot accurately reflect the power operation status between the interconnected substations, which can easily cause the system to shut down due to overload, posing a major safety hazard.

[0004] Therefore, how to achieve precise single-phase power control of the energy storage system in the substation interconnection system without communication conditions, while solving the overload risk caused by three-phase power imbalance, is a technical problem that needs to be solved urgently in this field. Summary of the invention

[0005] The main purpose of this application is to provide a power constraint control method, an energy storage control device and an energy storage system for an energy storage system, aiming to solve the technical problems that the energy storage system in the existing substation interconnection system cannot achieve precise single-phase power control through DC droop control, and is prone to overload and shutdown when the three-phase power is unbalanced.

[0006] To achieve the above-mentioned purpose, the present application provides a power constraint control method for an energy storage system, the method comprising: obtaining operating parameters of a PCS power module; encoding power information according to the operating parameters, obtaining encoding results, and controlling a DC bus voltage by means of the encoding results; wherein the operating parameters at least include the operating power of each phase of the PCS power module; obtaining a real-time voltage of the DC bus to obtain a monitoring result; decoding power information according to the monitoring result to obtain a decoding result, and constraining and controlling the operating power of each phase of the PCS power module according to the decoding result.

[0007] Optionally, the operating parameters also include positive rated power, negative rated power and a first power correction coefficient, the positive rated power is the maximum power supply power of the PCS power module, and the negative rated power is the maximum power consumption of the PCS power module; the power information encoding according to the operating parameters to obtain the encoding result includes: determining the single-phase maximum operating power and the single-phase minimum operating power according to the operating power of each phase; obtaining the positive power correction voltage according to the single-phase maximum operating power, the positive rated operating power and the first power correction coefficient; obtaining the negative power correction voltage according to the single-phase minimum operating power, the negative rated operating power and the first power correction coefficient; encoding information according to the positive power correction voltage, the negative power correction voltage, the rated voltage of the DC bus, a preset period and a preset duty cycle to obtain the encoding result, and the encoding result is a periodically changing voltage modulation waveform.

[0008] Optionally, the forward power correction voltage is obtained according to the single-phase maximum operating power, the forward rated operating power and the first power correction coefficient, including: determining the forward total power according to the single-phase maximum operating power; obtaining the forward power difference according to the forward total power and the forward rated operating power; and obtaining the forward power correction voltage according to the forward power difference and the first power correction coefficient.

[0009] Optionally, the negative power correction voltage is obtained according to the single-phase minimum operating power, the negative rated operating power and the first power correction coefficient, including: determining the negative total power according to the single-phase minimum operating power; obtaining the negative power difference according to the negative total power and the negative rated operating power; and obtaining the negative power correction voltage according to the negative power difference and the first power correction coefficient.

[0010] Optionally, decoding the power information according to the monitoring result to obtain the decoding result includes: extracting the real-time voltage of the DC bus according to the monitoring result; obtaining a maximum voltage difference and a minimum voltage difference according to the real-time voltage and the rated voltage of the DC bus; and obtaining the decoding result according to the maximum voltage difference, the minimum voltage difference and a second power correction coefficient, wherein the second power correction coefficient is the inverse of the first power correction coefficient.

[0011] Optionally, the decoding result includes the maximum positive operating transfer power and the maximum negative operating transfer power; the decoding result is obtained according to the maximum voltage difference, the minimum voltage difference and the second power correction coefficient, including: obtaining the maximum positive operating transfer power based on the maximum voltage difference and the second power correction coefficient; obtaining the maximum negative operating transfer power based on the minimum voltage difference and the second power correction coefficient.

[0012] Optionally, the operating parameters also include power setting values ​​of each phase of the PCS power module; the constraining control of the operating power of each phase of the PCS power module according to the decoding result includes: determining the sum of the power setting values ​​based on the power setting values ​​of each phase; obtaining a preliminary positive power derating coefficient according to the sum of the power setting values ​​and the positive maximum operating transfer power, and constraining the preliminary forward power derating coefficient to obtain the forward power derating coefficient; obtaining a preliminary negative power derating coefficient according to the sum of the power setting values ​​and the negative maximum operating transfer power, and constraining the preliminary negative power derating coefficient to obtain the negative power derating coefficient; adjusting the power setting value of each phase based on the forward power derating coefficient and the negative power derating coefficient to obtain the power adjustment value of each phase; and constraining the operating power of each phase of the PCS power module through the power adjustment value of each phase.

[0013] Optionally, the power setting value of each phase is adjusted based on the forward power derating coefficient and the negative power derating coefficient to obtain the power adjustment value of each phase, including: obtaining a total derating coefficient according to the forward power derating coefficient and the negative power derating coefficient; and adjusting the power setting value of each phase based on the total derating coefficient to obtain the power adjustment value of each phase.

[0014] In addition, to achieve the above-mentioned purpose, the present application also provides an energy storage control device, characterized in that the energy storage control device includes a PCS power module and a controller, the AC side of the PCS power module is connected to a three-phase AC system, the DC side of the PCS power module is connected to the PCS power modules in other energy storage control devices through a DC bus, and the controller is used to control the corresponding PCS power module; when the controller is applied to the power consumption end, the controller is used to obtain the operating parameters of the PCS power module; according to the operating parameters, power information is encoded to obtain the encoding results, and the DC bus voltage is controlled by the encoding results; wherein the operating parameters include at least the operating power of each phase of the PCS power module; when the controller is applied to the power supply end, the controller is used to obtain the real-time voltage of the DC bus to obtain a monitoring result; according to the monitoring result, the power information is decoded to obtain the decoding result, and the operating power of each phase of the PCS power module is constrained and controlled according to the decoding result.

[0015] In addition, the present application also provides an energy storage system, which is applied to a substation interconnection system, and the substation interconnection system includes multiple distribution substations, and each distribution substation is provided with an energy storage control device; wherein the AC side of the PCS power module is connected to the three-phase AC system of the distribution substation, and the DC side of the PCS power module is interconnected with the PCS power module of the adjacent distribution substation through a DC bus.

[0016] The beneficial effects that this application can achieve are as follows:

[0017] By acquiring the operating parameters of the PCS power module, encoding the operating power of each phase of the PCS power module according to the operating parameters of the PCS power module, and controlling the periodic change of the DC bus voltage, the energy storage system can convert the single-phase power information into the voltage characteristics on the DC bus, realizing the power information transmission without communication conditions; by monitoring the real-time voltage of the DC bus to obtain power information and based on this, constraining and controlling the operating power of each phase of the PCS power module respectively, the energy storage system can parse the power information contained in the voltage characteristics, and perform accurate single-phase power constraints accordingly to prevent overload.

[0018] In summary, this application breaks through the limitation that the existing DC droop control can only adjust the total power, and realizes the independent adjustment of each phase power. Since this application can constrain each phase power separately, the overload risk caused by three-phase power imbalance is effectively avoided. At the same time, this application does not need to add a dedicated communication line, which reduces the system cost and improves the system reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A schematic diagram of a flow chart of a power constraint control method for an energy storage system provided in an embodiment of the present application;

[0020] Figure 2 A schematic diagram of a substation interconnection system formed by two distribution substations provided in an embodiment of the present application;

[0021] Figure 3 A schematic diagram of the calculation of power information encoding provided in an embodiment of the present application;

[0022] Figure 4 A schematic diagram of a waveform of a DC bus voltage provided in an embodiment of the present application;

[0023] Figure 5 A schematic diagram of calculation of power information decoding provided in an embodiment of the present application;

[0024] Figure 6 A schematic diagram of the calculation of power constraint control provided in an embodiment of the present application.

[0025] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of 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.

[0027] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain preset posture (as shown in the accompanying drawings). If the preset posture changes, the directional indication will also change accordingly.

[0028] In the present invention, unless otherwise clearly specified and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0029] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the meaning of "and / or" appearing in the full text includes three parallel schemes. Taking "A and / or B" as an example, it includes scheme A, or scheme B, or a scheme that satisfies both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in the field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0030] The first embodiment of the present application provides a power constraint control method for an energy storage system, referring to Figure 1 , the method comprising:

[0031] S1: Obtain the operating parameters of the PCS power module;

[0032] S2: Encoding power information according to the operating parameters, obtaining encoding results, and controlling the DC bus voltage according to the encoding results; wherein the operating parameters at least include the operating power of each phase of the PCS power module;

[0033] S3: Obtain the real-time voltage of the DC bus and obtain the monitoring result;

[0034] S4: Decoding the power information according to the monitoring result, acquiring the decoding result, and performing constraint control on the operating power of each phase of the controlled PCS power module according to the decoding result.

[0035] Specifically, the energy storage system power constraint control method provided in the embodiment of the present application is applied to the substation interconnection system. Among them, the substation interconnection system includes a plurality of distribution substations, and each distribution substation is provided with a PCS power module and a controller. In each distribution substation, the AC side of the PCS power module is connected to the three-phase AC system of the distribution substation to realize power exchange with the three-phase AC system; the DC side of the PCS power module is interconnected with the PCS power module of the adjacent distribution substation through a DC bus to realize power transmission between substations; the controller is connected to its corresponding PCS power module to control the operating status of the PCS power module.

[0036] When the area where the controller is located is the power consumption end, first, the controller obtains the operating parameters of the PCS power module it controls, which at least includes the operating power of each phase of the PCS power module, reflecting the actual power demand of each phase of the distribution area. Subsequently, the controller performs power information encoding processing on the acquired operating power of each phase, and converts the power information into coded information that can be transmitted through the DC bus. After that, the controller controls the DC bus voltage according to the encoding result, so that the voltage value changes accordingly with the coded information, thereby transmitting the power demand information to the power supply end.

[0037] When the controller is located at the power supply end, first, the controller monitors and obtains the real-time voltage of the DC bus in real time to obtain the monitoring result, such as obtaining the DC bus voltage through a voltage sensor as the monitoring result. Subsequently, the controller decodes the power information of the monitoring result and restores the power information transmitted by the power consumption end from the voltage change of the monitoring result. After that, the controller constrains and controls the operating power of each phase of the PCS power module it controls according to the power information obtained by decoding, ensuring that the power of each phase is transmitted within the safe operating range.

[0038] Through the above control method, it is possible to transmit power information by utilizing the change of DC bus voltage without the need for a dedicated communication line, and to independently constrain and control the power of each phase, effectively avoiding the risk of overload caused by three-phase power imbalance.

[0039] like Figure 2 As shown in the figure, taking two adjacent distribution substations as an example, when the average three-phase voltage of substation 1 is lower than the allowable operating voltage, PCS1 needs to discharge and PCS2 needs to charge to achieve voltage management of substation 1. At this time, substation 1 is the power consumption end and substation 2 is the power supply end.

[0040] At the power consumption end (substation 1), the controller of substation 1 obtains the operating parameters of the PCS power module it controls, which include the operating power of each phase of the PCS power module, and encodes and processes the power information, and transmits the power demand information to the power supply end by controlling the DC bus voltage to form a specific periodic waveform.

[0041] At the power supply end (station 2), the controller of station 2 monitors the DC bus voltage in real time to obtain the monitoring result, that is, the change information of the DC bus voltage. Then, the controller of station 2 decodes the monitoring result to obtain the corresponding power constraint control value, and constrains the operating power of each phase of the PCS power module of station 2 according to the decoding result.

[0042] In this way, electric energy can be converted from the three-phase AC system of substation 2 into DC power through the PCS power module of substation 2, transmitted to the PCS power module of substation 1 through the DC bus, and then converted into AC power by the PCS power module and input into the three-phase AC system of substation 1, thereby realizing power-constrained transmission between substations.

[0043] It can be seen that by using the control method of encoding at the power consumption end and decoding at the power supply end, the power information is transmitted by using the change of DC bus voltage, and the independent constraint control of each phase power is realized. The embodiment of the present application breaks through the limitation that the existing DC droop control can only adjust the total power, effectively avoiding the risk of overload caused by three-phase power imbalance, and at the same time, there is no need to add a dedicated communication line, which reduces the system cost and improves the system reliability.

[0044] As an optional implementation manner, the operating parameters further include a positive rated power, a negative rated power and a first power correction coefficient, the positive rated power is the maximum power supply power of the PCS power module, and the negative rated power is the maximum power consumption of the PCS power module; encoding the power information according to the operating parameters to obtain the encoding result includes:

[0045] S21: Determine the single-phase maximum operating power and the single-phase minimum operating power according to the operating power of each phase;

[0046] S22: Obtaining a forward power correction voltage according to the single-phase maximum operating power, the forward rated operating power and the first power correction coefficient;

[0047] S23: Obtaining a negative power correction voltage according to the single-phase minimum operating power, the negative rated operating power and the first power correction coefficient;

[0048] S24: Encode information according to the positive power correction voltage, the negative power correction voltage, the rated voltage of the DC bus, a preset period and a preset duty cycle to obtain the encoding result, which is a periodically changing voltage modulation waveform.

[0049] Specifically, the operating parameters also include positive rated power, negative rated power and a first power correction factor. The positive rated power is the maximum power that the PCS power module can supply; the negative rated power is the maximum power that the PCS power module can absorb; and the first power correction factor is a correction parameter determined according to the actual characteristics of the PCS power module.

[0050] When the substation where the control area is located is the power consumption end, the controller determines the single-phase maximum operating power and the single-phase minimum operating power of the three phases according to the operating power of each phase of the PCS power module. For each phase operating power, the maximum value is selected as the single-phase maximum operating power, and the minimum value is selected as the single-phase minimum operating power. Secondly, the controller uses the single-phase maximum operating power, the positive rated operating power and the first power correction coefficient to calculate and obtain the positive power correction voltage. Similarly, the single-phase minimum operating power, the negative rated operating power and the first power correction coefficient are used to calculate and obtain the negative power correction voltage. After that, the controller combines the positive power correction voltage, the negative power correction voltage and the rated voltage of the DC bus, and generates a periodically changing voltage modulation waveform according to the preset period and duty cycle parameters. This waveform is the final encoding result.

[0051] like Figure 3 As shown, the calculation method of the power allowed to be transferred by the periodic voltage regulation of PCS1 is demonstrated. Specifically, first, the controller collects the three-phase real-time operating power of PCS1, which are PowA_pcs1_run, PowB_pcs1_run, and PowC_pcs1_run. Then, the maximum value among PowA_pcs1_run, PowB_pcs1_run, and PowC_pcs1_run is selected as the single-phase maximum operating power; the minimum value among PowA_pcs1_run, PowB_pcs1_run, and PowC_pcs1_run is selected as the single-phase minimum operating power.

[0052] Next, the controller obtains the positive power correction voltage, namely Udc_pcs1_crt1, according to the single-phase maximum operating power, the positive rated operating power (+Pow_pcs1_rate) and the first power correction coefficient (PowStep_pcs1_crt). At the same time, the negative power correction voltage, namely Udc_pcs1_crt2, is obtained according to the single-phase minimum operating power, the negative rated operating power (-Pow_pcs1_rate) and the first power correction coefficient (PowStep_pcs1_crt).

[0053] Afterwards, the obtained positive power correction voltage (Udc_pcs1_crt1) and negative power correction voltage (Udc_pcs1_crt2) are combined with the rated voltage (Udc_pcs1_rate), preset period (TimePeriod_pcs1_rate) and preset duty cycle (DutyCycle_pcs1_rate) of the DC bus to generate the final DC bus voltage, namely, Udc_pcs1_ref. Figure 4 , in each cycle TimePeriod, the voltage value switches between the positive power correction voltage and the negative power correction voltage according to the preset duty cycle DutyCycle based on the rated voltage of the DC bus. Specifically, in the first half of a cycle, the voltage value is the rated voltage of the DC bus minus the negative power correction voltage, that is, Udc_pcsl_run_min; in the second half, the voltage value is the rated voltage of the DC bus plus the negative power correction voltage, that is, Udc_pcsl_run_max, thus forming a periodically changing voltage modulation waveform.

[0054] By selecting the single-phase maximum operating power and the single-phase minimum operating power, and then combining the positive rated operating power, the negative rated operating power and the power correction coefficient, the power information is converted into the corresponding voltage correction value, and then the preset period and duty cycle are used to generate a periodically changing voltage modulation waveform, so that the power information can be reliably transmitted to the power supply end through the DC bus.

[0055] As an optional implementation manner, obtaining the forward power correction voltage according to the single-phase maximum operating power, the forward rated operating power and the first power correction coefficient includes:

[0056] S221: Determine the total forward power according to the single-phase maximum operating power;

[0057] S222: Obtain a forward power difference according to the forward total power and the forward rated operating power;

[0058] S223: Obtain the forward power correction voltage according to the forward power difference and the first power correction coefficient.

[0059] Specifically, when obtaining the forward power correction voltage, first, the controller determines the forward total power based on the single-phase maximum operating power. Specifically, the single-phase maximum operating power is multiplied by the number of three-phase electrical phases (i.e., 3) to obtain the forward total power. Secondly, the controller performs a difference operation on the calculated forward total power and the forward rated operating power of the PCS power module to obtain the forward power difference. After that, the controller multiplies the forward power difference by the first power correction coefficient to obtain the forward power correction voltage.

[0060] like Figure 3 As shown, first, the selected single-phase maximum operating power is multiplied by 3 to obtain the forward total power; then, the forward power difference is obtained by subtracting the forward total power from the forward rated operating power + Pow_pcs1_rate; after that, the forward power difference is multiplied by the first power correction coefficient PowStep_pcs1_crt to obtain the forward power correction voltage Udc_pcs1_crt1, which provides support for the subsequent generation of a DC voltage modulation waveform.

[0061] As an optional implementation manner, obtaining the negative power correction voltage according to the single-phase minimum operating power, the negative rated operating power and the first power correction coefficient includes:

[0062] S231: Determine the negative total power according to the single-phase minimum operating power;

[0063] S232: Obtaining a negative power difference according to the negative total power and the negative rated operating power;

[0064] S233: Obtain the negative power correction voltage according to the negative power difference and the first power correction coefficient.

[0065] Specifically, when obtaining the negative power correction voltage, first, the controller determines the negative total power based on the single-phase minimum operating power. Specifically, the single-phase minimum operating power is multiplied by the number of three-phase electrical phases (i.e., 3) to obtain the negative total power. Secondly, the controller performs a difference operation on the calculated negative total power and the negative rated operating power of the PCS power module to obtain the negative power difference. After that, the controller multiplies the negative power difference by the first power correction coefficient to obtain the negative power correction voltage.

[0066] like Figure 3As shown, first, the selected single-phase minimum operating power is multiplied by 3 to obtain the negative total power; then, the negative power difference is obtained by subtracting the negative total power from the negative rated operating power - Pow_pcs1_rate; then, the obtained negative power difference is multiplied by the first power correction coefficient PowStep_pcs1_crt to obtain the negative power correction voltage Udc_pcs1_crt2, which provides support for the subsequent generation of a DC voltage modulation waveform.

[0067] The following example illustrates the operation process of the corresponding controller when the substation is the power consumption end.

[0068] Assume that the area 1 is the power consumption end, and the corresponding PCS1 parameters are configured as follows: the positive rated operating power +Pow_pcs1_rate is 100kW, the negative rated operating power -Pow_pcs1_rate is -100kW, and the first power correction coefficient PowStep_pcs1_crt is 0.4. The rated voltage of the DC bus is 750V.

[0069] At a certain moment, the real-time operating power of the three phases of PCS1 is: PowA_pcs1_run is 20kW, PowB_pcs1_run is 10kW, and PowC_pcs1_run is -5kW. When selecting the single-phase maximum operating power and the single-phase minimum operating power, according to the actual value of the operating power of each phase, the single-phase maximum operating power is 20kW and the single-phase minimum operating power is -5kW.

[0070] Subsequently, the forward power correction voltage is calculated. Specifically, first, the single-phase maximum operating power of 20kW is multiplied by the number of three-phase electrical phases 3 to obtain a forward total power of 60kW; secondly, the forward rated operating power of 100kW is subtracted from the forward total power of 60kW to obtain a forward power difference of 40kW; then, the forward power difference of 40kW is multiplied by the first power correction coefficient of 0.4 to obtain a forward power correction voltage of 16V.

[0071] At the same time, the negative power correction voltage is calculated. Specifically, first, the single-phase minimum operating power -5kW is multiplied by the number of three-phase electrical phases 3 to obtain the negative total power -15kW; secondly, the negative rated operating power -100kW minus the negative total power -15kW is obtained to obtain the negative total power of -85kW; then, the negative total power -85kW is multiplied by the first power correction coefficient 0.4 to obtain the negative power correction voltage -34V.

[0072] Among them, since the positive rated operating power of PCS1 is 100kW and the negative rated operating power is -100kW, the allowable operating power range of each phase is -33.3kW to +33.33kW. Therefore, for the A phase with a maximum operating power of 20kW, it can be increased by 13.3kW, and the three phases can increase by 40kW in total; for the C phase with a minimum operating power of -5kW, it can be reduced by 28.3kW, and the three phases can reduce by 85kW in total.

[0073] After that, the obtained positive power correction voltage 16V, negative power correction voltage -34V and rated voltage 750V of DC bus are combined to obtain the maximum operating DC bus voltage of 766V (i.e. 750V+16V) and the minimum operating DC bus voltage of 716V (i.e. 750V-34V). Subsequently, the encoding result is generated based on the obtained maximum operating DC bus voltage and minimum operating DC bus voltage. Among them, in the first half of a cycle, the voltage value is 716V; in the second half, the voltage value is 766V, thereby forming a periodically changing voltage modulation waveform, which is the final encoding result Udc_pcs1_ref, realizing the encoding of each phase operating power into a periodically changing waveform of DC bus voltage.

[0074] As an optional implementation manner, the decoding of power information according to the monitoring result to obtain the decoding result includes:

[0075] S41: extracting the real-time voltage of the DC bus according to the monitoring result;

[0076] S42: Obtaining a maximum voltage difference and a minimum voltage difference according to the real-time voltage and the rated voltage of the DC bus;

[0077] S43: Obtain the decoding result according to the maximum voltage difference, the minimum voltage difference and a second power correction coefficient, wherein the second power correction coefficient is the inverse of the first power correction coefficient.

[0078] Specifically, when the distribution station area where the controller is located serves as the power supply end, first, the controller extracts the real-time voltage value of the DC bus according to the monitoring results. The real-time voltage value contains the power information encoded at the power consumption end. Secondly, the controller compares the acquired real-time voltage value with the rated voltage of the DC bus to obtain the maximum voltage difference and the minimum voltage difference. These differences reflect the power demand information of the power consumption end. Then, the controller calculates the maximum voltage difference and the minimum voltage difference obtained in combination with the second power correction coefficient to obtain a decoding result. Among them, the second power correction coefficient is the opposite of the first power correction coefficient, which is used to restore the voltage information to power information. For example, if the first power correction coefficient is 0.4, the second power correction coefficient is -0.4.

[0079] Through the above decoding process, the power supply end can accurately obtain the power demand information encoded in the DC bus voltage of the power consumption end.

[0080] As an optional implementation manner, the decoding result includes a maximum positive operating transfer power and a maximum negative operating transfer power; the decoding result is obtained according to the maximum voltage difference, the minimum voltage difference and the second power correction coefficient, and the decoding result includes the maximum positive operating transfer power and the maximum negative operating transfer power, including:

[0081] S431: Obtaining the forward maximum operating transfer power based on the maximum voltage difference and the second power correction coefficient;

[0082] S432: Based on the minimum voltage difference and the second power correction coefficient, the negative maximum operating transfer power is obtained.

[0083] Specifically, the decoding results obtained include the maximum positive operating transfer power and the maximum negative operating transfer power, and these two parameters will be used for subsequent power constraint control. After the controller at the power supply end obtains the maximum voltage difference, the minimum voltage difference and the second power correction coefficient, the controller first divides the maximum voltage difference by the second power correction coefficient to obtain the maximum positive operating transfer power, which reflects the maximum power supply power allowed to be received by the power consumption end. At the same time, the controller divides the minimum voltage difference by the second power correction coefficient to obtain the maximum negative operating transfer power, which reflects the maximum power consumption allowed to be received by the power consumption end.

[0084] By calculating the maximum positive operating transfer power and the maximum negative operating transfer power, the power supply end obtains the power operating range that the power consumption end can accept, providing a specific control basis for subsequent power constraint control.

[0085] For example, Figure 2 The middle area 2 is used as the power supply end, and its corresponding PCS power module is PCS2, which explains the decoding process. Figure 5As shown, first, the controller of substation 2 extracts the real-time voltage value Udc_pcs2_run of the DC bus from the monitoring results. At the same time, the controller obtains the rated voltage Udc_pcs2_rate and the second power correction coefficient PowStep_pcs2_crt of the DC bus. Then, the maximum voltage difference and the minimum voltage difference are obtained by subtracting the rated voltage Udc_pcs2_rate of the DC bus from the real-time voltage value Udc_pcs2_run. The maximum voltage difference and the minimum voltage difference are respectively processed with the second power correction coefficient PowStep_pcs2_crt to obtain a decoding result, including the maximum positive operating transfer power Pow_pcs2_allow1 and the maximum negative operating transfer power Pow_pcs2_allow2. These power values ​​will serve as the basis for power constraint control at the power supply end.

[0086] Through the above decoding method, PCS2 can accurately obtain the power demand information encoded in the DC bus voltage by PCS1 at the power consumption end without communication, laying the foundation for subsequent power constraint control.

[0087] like Figure 5 As shown, the maximum difference between the DC bus voltage and the rated voltage Udc_pcs2_rate of the DC bus is divided by the second power correction coefficient PowStep_pcs2_crt to obtain the maximum positive operation transfer power Pow_pcs2_allow1; similarly, the minimum difference is divided by the second power correction coefficient to obtain the maximum negative operation transfer power Pow_pcs2_allow2. In this way, decoding from voltage information to power information is achieved.

[0088] The following example illustrates the decoding process of the corresponding controller when the station area is the power supply end.

[0089] Assume that the substation 2 is the power supply end, and set the second power correction coefficient PowStep_pcs2_crt of PCS2 corresponding to the power supply end to -0.4. The rated voltage Udc_pcs2_rate of the DC bus is 750V. At a certain moment, the DC bus voltage monitored by the controller of substation 2 changes between 766V and 716V in one cycle as the monitoring result.

[0090] Subsequently, the controller of substation 2 calculates the maximum forward operating transfer power based on the monitoring results. Specifically, the maximum voltage value 766V monitored is subtracted from the rated voltage 750V of the DC bus to obtain the maximum voltage difference of 16V; then, the maximum voltage difference 16V is divided by the second power correction coefficient -0.4 to obtain the maximum forward operating transfer power Pow_pcs2_allow1 of -40kW. At the same time, the controller of substation 2 calculates the maximum negative operating transfer power based on the monitoring results. Specifically, the rated voltage 750V of the DC bus is subtracted from the minimum voltage value 716V monitored to obtain the minimum voltage difference of -34V; then, the minimum voltage difference of -34V is divided by the second power correction coefficient -0.4 to obtain the maximum negative operating transfer power Pow_pcs2_allow2 of 85kW. Through this decoding process, the power supply end successfully obtains the power demand information of the power consumption end from the periodic changes of the DC bus voltage, providing a basis for subsequent power constraint control.

[0091] As an optional implementation manner, the operating parameters further include power setting values ​​of each phase of the PCS power module; and the constraining and controlling the operating power of each phase of the PCS power module according to the decoding result includes:

[0092] S44: Determine a total power setting value based on the power setting value of each phase;

[0093] S45: obtaining a preliminary forward power derating coefficient according to the sum of the power setting values ​​and the forward maximum operating transfer power, and performing constraint processing on the preliminary forward power derating coefficient to obtain the forward power derating coefficient;

[0094] S46: obtaining a preliminary negative power derating factor according to the sum of the power setting values ​​and the negative maximum operating transfer power, and performing constraint processing on the preliminary negative power derating factor to obtain a negative power derating factor;

[0095] S47: adjusting the power setting value of each phase based on the positive power derating coefficient and the negative power derating coefficient to obtain a power adjustment value of each phase;

[0096] S48: Constraining and controlling the operating power of each phase of the PCS power module through the power adjustment value of each phase.

[0097] Specifically, the operating parameters also include the power setting values ​​of each phase of the PCS power module. After obtaining the decoding result, the controller at the power supply end performs constraint control on the operating power of each phase of the PCS power module.

[0098] First, the sum of the power setting values ​​is calculated based on the power setting values ​​of each phase of the PCS power module, that is, the power setting values ​​of each phase are added to obtain the sum of the power setting values. The sum of the power setting values ​​reflects the current expected overall operating power of the PCS power module. Secondly, the controller calculates the preliminary positive power derating coefficient based on the sum of the power setting values ​​and the decoded positive maximum operating transfer power, and constrains the preliminary positive power derating coefficient to the range of [0, 1], thereby obtaining the positive power derating coefficient. Similarly, the preliminary negative power derating coefficient is calculated based on the sum of the power setting values ​​and the decoded negative maximum operating transfer power, and constrains the preliminary negative power derating coefficient to the range of [0, 1], thereby obtaining the negative power derating coefficient. Then, based on the obtained positive power derating coefficient and negative power derating coefficient, the controller adjusts the power setting values ​​of each phase accordingly to obtain the power adjustment values ​​of each phase. This adjustment ensures that the actual operating power does not exceed the allowable range. Afterwards, the controller constrains the operating power of each phase of the PCS power module according to the calculated power adjustment value of each phase, thereby achieving precise control of power transmission.

[0099] like Figure 6 As shown, first, the power setting values ​​of each phase PowA_pcs2_set, PowB_pcs2_set and PowC_pcs2_set are added to obtain the total power setting value PowTotal_pcs2_set, and then, the positive maximum operating transfer power Pow_pcs2_allow1 is divided by the total power setting value PowTotal_pcs2_set to obtain the preliminary positive power derating factor, and at the same time, the negative maximum operating transfer power Pow_pcs2_allow2 is divided by the total power setting value PowTotal_pcs2_set to obtain the preliminary negative power derating factor.

[0100] Subsequently, the controller performs constraint processing on the obtained preliminary positive power derating coefficient and preliminary negative power derating coefficient, and constrains them within the range of [0, 1]. If the preliminary positive power derating coefficient or the preliminary negative power derating coefficient is within the range of [0, 1], its original value is maintained; when it is greater than 1, it is constrained to 1; when it is less than 0, it is constrained to 0. After constraint processing, the preliminary positive power derating coefficient and the preliminary negative power derating coefficient are converted into the final positive power derating coefficient and the negative power derating coefficient.

[0101] As an optional implementation manner, adjusting the power setting value of each phase based on the positive power derating coefficient and the negative power derating coefficient to obtain the power adjustment value of each phase includes:

[0102] S471: Obtain a total derating factor according to the forward power derating factor and the negative power derating factor;

[0103] S472: Adjust the power setting value of each phase based on the total derating factor to obtain the power adjustment value of each phase.

[0104] Specifically, after obtaining the positive power derating coefficient and the negative power derating coefficient, the controller first adds the positive power derating coefficient and the negative power derating coefficient to obtain the total derating coefficient. The total derating coefficient comprehensively reflects the power constraints in the positive and negative directions. Then, the controller multiplies the total derating coefficient by the power setting value of each phase to obtain the power adjustment value of each phase. Through this adjustment, it is ensured that the actual operating power meets the power constraint requirements of the power consumption end.

[0105] like Figure 6 As shown, the controller adds the calculated positive power derating factor and negative power derating factor to obtain the total derating factor PowPara_pcs2_set, and then multiplies the obtained total derating factor by the power setting value of each phase to finally obtain the actual power control value. This control method ensures that the power output of the power supply end does not exceed the allowable range of the power consumption end.

[0106] like Figure 2 As shown, the station area 2 is the power supply end, which is used as an example to illustrate the power constraint control process.

[0107] Assume that the power setting values ​​of each phase of the PCS power module PCS2 of the substation 2 at time t0 are: PowA_pcs2_set is 10kW, PowB_pcs2_set is 20kW, and PowC_pcs2_set is 30kW. Adding these setting values ​​together, the total power setting value PowTotal_pcs2_set is 60kW. According to the above decoding results, the maximum positive operating transfer power Pow_pcs2_allow1 at this time is -40kW, and the maximum negative operating transfer power Pow_pcs2_allow2 is 85kW. Then, calculate the total derating factor. First, the maximum forward operating transfer power of -40kW is divided by the total power setting value of 60kW, and the initial forward power derating coefficient is -0.667. Since this value is less than 0, it is constrained to 0 as the forward power derating coefficient; at the same time, the maximum negative operating transfer power of 85kW is divided by the total power setting value of 60kW, and the initial negative power derating coefficient is 1.41. Since this value is greater than 1, it is constrained to 1 as the negative power derating coefficient. Add the obtained positive power derating coefficient of 0 and the negative power derating coefficient of 1 to obtain a total derating coefficient of 1. Then, multiply the power setting value of each phase at time t0 by the total derating coefficient of 1, and obtain the power adjustment values ​​of each phase, which are PowA_pcs2_set of 10kW, PowB_pcs2_set of 20kW, and PowC_pcs2_set of 30kW. This is because when the total power of PCS2 is 60kW at this time, the corresponding power change of PCS1 is -60kW. The current minimum single-phase operating power of PCS1 is -5kW. Considering that each phase can be reduced by 28.3kW (a total of -85kW for three phases), it can fully meet the power transmission needs at this time.

[0108] Assume that the power setting values ​​of each phase of PCS power module PCS2 in substation 2 at time t1 are: PowA_pcs2_set is -10kW, PowB_pcs2_set is -20kW, PowC_pcs2_set is -30kW, and the total power setting value PowTotal_pcs2_set is -60kW. Assume that PCS1 has not changed at this time, the maximum positive operating transfer power and the maximum negative operating transfer power remain unchanged, and the maximum positive operating transfer power is still -40kW, and the maximum negative operating transfer power is 85kW. Then, calculate the total derating factor. First, the maximum positive operating transfer power -40kW is divided by the total power setting value -60kW to obtain the preliminary positive power derating coefficient of 0.667, which is in the range of [0,1] and remains unchanged as the positive power derating coefficient; at the same time, the maximum negative operating transfer power 85kW is divided by the total power setting value -60kW to obtain the preliminary negative power derating coefficient of -1.41. Since this value is less than 0, it is constrained to 0 as the negative power derating coefficient. The obtained positive power derating coefficient of 0.667 and the negative power derating coefficient of 0 are added together to obtain the total derating coefficient of 0.667. Subsequently, the power setting value of each phase at time t1 is multiplied by the total derating coefficient of 0.667 for adjustment, and the power adjustment values ​​of each phase are obtained as follows: PowA_pcs2_set is -6.67kW, PowB_pcs2_set is -13.33kW, and PowC_pcs2_set is -20kW. This is because when the total power of PCS2 is -60kW, the corresponding power change of PCS1 needs to increase by 60kW. The current maximum operating power of PCS1 per phase is 20kW. Considering that each phase can increase by 13.3kW (a total of 40kW for three phases), it cannot meet the power setting requirement of increasing by 60kW. Therefore, it is necessary to adjust according to the total derating factor to ensure that the power transmission does not exceed the power limit of PCS1.

[0109] Through the power constraint control of the energy storage system, power information transmission and constraint control between adjacent stations can be achieved only through changes in DC bus voltage without the need to add special communication lines. At the same time, unlike the traditional DC droop control method that can only adjust the total power, the embodiment of the present application realizes independent and precise adjustment of the three-phase power, effectively avoiding the risk of overload caused by three-phase power imbalance, and ensuring the safe and stable operation of the entire system.

[0110] A second embodiment of the present application provides an energy storage control device, the energy storage control device comprising a PCS power module and a controller, the AC side of the PCS power module is connected to a three-phase AC system, the DC side of the PCS power module is connected to the PCS power modules in other energy storage control devices through a DC bus, and the controller is used to control the corresponding PCS power module;

[0111] When the controller is applied to the power consumption end, the controller is used to obtain the operating parameters of the PCS power module; encode the power information according to the operating parameters, obtain the encoding result, and control the DC bus voltage according to the encoding result; wherein the operating parameters at least include the operating power of each phase of the PCS power module;

[0112] When the controller is applied to the power supply end, the controller is used to obtain the real-time voltage of the DC bus and obtain monitoring results; decode the power information according to the monitoring results to obtain the decoding results, and constrain the operating power of each phase of the PCS power module according to the decoding results.

[0113] The third embodiment of the present application is an energy storage system, which is applied to a substation interconnection system, wherein the substation interconnection system includes multiple distribution substations, and each distribution substation is provided with an energy storage control device; wherein the AC side of the PCS power module is connected to the three-phase AC system of the distribution substation, and the DC side of the PCS power module is interconnected with the PCS power module of the adjacent distribution substation through a DC bus.

[0114] The above are only preferred embodiments of the present application, and are not intended to limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A power constraint control method for an energy storage system, characterized in that: The method comprises: Get the operating parameters of the PCS power module; Encoding power information according to the operating parameters, obtaining encoding results, and controlling the DC bus voltage according to the encoding results; wherein the operating parameters at least include the operating power of each phase of the PCS power module; Obtain the real-time voltage of the DC bus and obtain the monitoring results; The power information is decoded according to the monitoring result, a decoding result is obtained, and the operating power of each phase of the PCS power module is constrained and controlled according to the decoding result.

2. The method according to claim 1, characterized in that The operating parameters further include a positive rated power, a negative rated power and a first power correction coefficient, the positive rated power is the maximum power supply power of the PCS power module, and the negative rated power is the maximum power consumption of the PCS power module; encoding the power information according to the operating parameters to obtain the encoding result includes: Determine the single-phase maximum operating power and the single-phase minimum operating power according to the operating power of each phase; Obtaining a forward power correction voltage according to the single-phase maximum operating power, the forward rated operating power and the first power correction coefficient; Obtaining a negative power correction voltage according to the single-phase minimum operating power, the negative rated operating power and the first power correction coefficient; Information encoding is performed according to the positive power correction voltage, the negative power correction voltage, the rated voltage of the DC bus, a preset period and a preset duty cycle to obtain the encoding result, which is a periodically changing voltage modulation waveform.

3. The method according to claim 2, characterized in that The step of obtaining a forward power correction voltage according to the single-phase maximum operating power, the forward rated operating power and the first power correction coefficient includes: Determining the total forward power according to the single-phase maximum operating power; Obtaining a forward power difference according to the forward total power and the forward rated operating power; The forward power correction voltage is obtained according to the forward power difference and the first power correction coefficient.

4. The method according to claim 2, characterized in that: The step of obtaining a negative power correction voltage according to the single-phase minimum operating power, the negative rated operating power and the first power correction coefficient includes: Determining the negative total power according to the single-phase minimum operating power; Obtaining a negative power difference according to the negative total power and the negative rated operating power; The negative power correction voltage is obtained according to the negative power difference and the first power correction coefficient.

5. The method according to claim 2, characterized in that: The step of decoding the power information according to the monitoring result and obtaining the decoding result includes: According to the monitoring result, extracting the real-time voltage of the DC bus; According to the real-time voltage and the rated voltage of the DC bus, a maximum voltage difference and a minimum voltage difference are obtained; The decoding result is obtained according to the maximum voltage difference, the minimum voltage difference and a second power correction coefficient, wherein the second power correction coefficient is the inverse of the first power correction coefficient.

6. The method according to claim 5, characterized in that The decoding result includes the maximum positive operating transfer power and the maximum negative operating transfer power; the decoding result is obtained according to the maximum voltage difference, the minimum voltage difference, and the second power correction coefficient, including: Based on the maximum voltage difference and the second power correction coefficient, the forward maximum operating transfer power is obtained; Based on the minimum voltage difference and the second power correction coefficient, the negative maximum operating transfer power is obtained.

7. The method according to claim 6, characterized in that The operating parameters also include power setting values ​​of each phase of the PCS power module; and the constraining and controlling the operating power of each phase of the PCS power module according to the decoding result includes: Determining a total power setting value based on the power setting values ​​of each phase; Obtaining a preliminary forward power derating coefficient according to the sum of the power setting values ​​and the forward maximum operating transfer power, and performing constraint processing on the preliminary forward power derating coefficient to obtain the forward power derating coefficient; Obtaining a preliminary negative power derating factor according to the sum of the power setting values ​​and the negative maximum operating transfer power, and performing constraint processing on the preliminary negative power derating factor to obtain a negative power derating factor; Adjusting the power setting value of each phase based on the positive power derating coefficient and the negative power derating coefficient to obtain the power adjustment value of each phase; The operating power of each phase of the PCS power module is constrained and controlled through the power adjustment value of each phase.

8. The method according to claim 7, characterized in that The adjusting the power setting value of each phase based on the positive power derating coefficient and the negative power derating coefficient to obtain the power adjustment value of each phase includes: Obtaining a total derating factor according to the forward power derating factor and the negative power derating factor; The power setting value of each phase is adjusted based on the total derating factor to obtain the power adjustment value of each phase.

9. An energy storage control device, characterized in that: The energy storage control device includes a PCS power module and a controller, wherein the AC side of the PCS power module is connected to a three-phase AC system, the DC side of the PCS power module is connected to PCS power modules in other energy storage control devices via a DC bus, and the controller is used to control the corresponding PCS power module; When the controller is applied to the power consumption end, the controller is used to obtain the operating parameters of the PCS power module; encode the power information according to the operating parameters, obtain the encoding result, and control the DC bus voltage according to the encoding result; wherein the operating parameters at least include the operating power of each phase of the PCS power module; When the controller is applied to the power supply end, the controller is used to obtain the real-time voltage of the DC bus and obtain monitoring results; decode the power information according to the monitoring results to obtain the decoding results, and constrain the operating power of each phase of the PCS power module according to the decoding results.

10. An energy storage system, characterized in that: The energy storage system is applied to a substation interconnection system, the substation interconnection system includes a plurality of distribution substations, each of which is provided with an energy storage control device according to claim 9; The AC side of the PCS power module is connected to the three-phase AC system of the power distribution station area, and the DC side of the PCS power module is interconnected with the PCS power module of the adjacent power distribution station area through a DC bus.

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