Household energy storage system and low-temperature heating control method thereof

Abstract

The invention discloses a household energy storage system which is formed by connecting a battery pack, a direct current converter and a DC / AC inverter in sequence. A low-temperature heating control method of a household energy storage system comprises the steps that 1, whether the state of charge (SOC) of a battery pack is lower than the lowest state of charge (SOCmin or not is judged, and if yes, operation is ended; otherwise, proceeding to step 2; step 2, acquiring the temperature of the battery pack, then judging whether the temperature is lower than a preset temperature lower limit Tmin or not, and if so, entering a low-temperature working mode and executing step 3; otherwise, returning to the step 1; step 3, the DC converter charges a bus capacitor in the DC / AC inverter; step 4, the DC / AC inverter discharges the bus capacitor; 5, rapid heating and smooth power output of the battery pack are achieved; step 6, judging whether the household energy storage system allows power generation to surf the internet or not, if so, returning to the step 3, and otherwise, entering the step 7; and 7, pulse discharge heating is carried out during household electricity utilization.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage, and particularly relates to a household energy storage system and a low-temperature heating control method thereof. Background Art

[0002] A household energy storage system is actually what we often call an electric energy storage product or a "battery energy storage system" (BESS). Simply put, it stores the electric energy that is not used up at home and then uses it when needed. This process sounds a bit like charging a mobile phone, except that we use a household energy storage device.

[0003] The core of household energy storage is a rechargeable energy storage battery, usually a lithium-ion or lead-acid battery. These batteries are controlled by a computer and work together with other intelligent hardware and software to achieve the cycle of charging and discharging.

[0004] From the user's perspective, household energy storage has two main uses:

[0005] 1. Saving money: By increasing the proportion of self-use of generated electricity and participating in the auxiliary service market, etc., the electricity cost is reduced. Simply put, it saves you a sum of money on electricity bills.

[0006] 2. Emergency backup power supply: When facing a major disaster that causes the power grid to lose power, the household energy storage can be used as an emergency backup power supply to improve the reliability of household power supply. For example, you can still use electricity during a power outage, and your life and work will not be affected too much.

[0007] From the perspective of the power grid side, household energy storage can also assist the power grid in balancing the power generation capacity and power consumption demand. A household energy storage device that supports unified dispatching can relieve the power shortage during peak hours and provide frequency correction for the power grid. Simply put, it helps the power grid better manage electricity and ensure the stability of power supply.

[0008] In recent years, with the popular application of household energy storage systems, for example, a Chinese utility model patent CN 208349407U discloses an intelligent heating and ventilation system. The system includes a solar energy workstation, a storage water tank, a water mixing device, and a household heating and ventilation device. Among them, the solar energy workstation is a solar energy conversion device, which is connected to the storage water tank and heats the water in the storage water tank by the solar energy collected by the solar panels. The system also includes an auxiliary heat source wall-mounted boiler, which provides an auxiliary heat source for the storage water tank when the solar energy is insufficient. The storage water tank is connected to the water mixing device, and the high-temperature medium water in the storage water tank is mixed with the low-temperature medium water in the household heating and ventilation device through the water mixing device, and then introduced into the household heating and ventilation device. However, the above-mentioned household energy storage system has the problem that the battery cannot be charged in a low-temperature environment. Common solutions include using heating sheets to heat the household energy storage system, installing the household energy storage system indoors or in a garage, etc., but these solutions have defects such as low thermal efficiency and inconvenience to users.

[0009] The battery has the fast heating characteristic of pulsed discharge. High-rate charging at low temperature can quickly heat the battery from the inside out, and the thermal efficiency is relatively high. However, the pulsed discharge power is not friendly to the power grid and will cause power fluctuations. Therefore, how to eliminate power fluctuations has become a major problem.

[0010] In the prior art, the household energy storage system cannot work properly in a low-temperature environment. The heating method has low efficiency and increases the additional hardware cost. There is an urgent need for a control method that can not only quickly heat the battery but also smoothly output power to improve the performance of the system in a low-temperature environment. Summary of the Invention

[0011] Object of the Invention: In the existing household energy storage system, there are problems such as the battery cannot be quickly and effectively heated to a suitable charging temperature in a low-temperature environment, the heating power consumption is relatively high, and the power fluctuation is relatively large. To solve the above technical problems, the present invention provides a household energy storage system and its low-temperature heating control method.

[0012] Technical Solution: A household energy storage system is composed of the following parts:

[0013] A battery pack, which is formed by sequentially connecting multiple battery cells in series and is used for energy storage;

[0014] A DC converter, which is connected to the battery pack and is used to boost the voltage of the battery pack to form high-voltage direct current to realize the bidirectional flow from the battery pack to the DC bus;

[0015] A DC / AC inverter, which is connected to the DC converter and is used to convert the high-voltage direct current into alternating current for output.

[0016] Further, the battery cell is a lithium-ion battery cell or a lead-acid battery cell.

[0017] Furthermore, a bus capacitor is provided in the DC / AC inverter, and the DC converter is electrically connected to the bus capacitor.

[0018] A low-temperature heating control method for a household energy storage system, where the household energy storage system adopts the household energy storage system described in any one of the above, and the steps are as follows:

[0019] Step 1: Determine whether the state of charge SOC of the battery pack is lower than the preset minimum state of charge SOC min , if it is lower, end this operation; otherwise, proceed to Step 2;

[0020] Step 2: Obtain the temperature of the battery pack, and then determine whether it is lower than the preset lower temperature limit T min , if the temperature of the battery pack is lower than the preset lower temperature limit T min , then the household energy storage system enters the low-temperature working mode and executes Step 3; otherwise, return to Step 1;

[0021] Step 3: The DC converter charges the bus capacitor in the DC / AC inverter in a pulsed manner at the rated power Pe according to the preset duty cycle D, and then proceeds to Step 4;

[0022] Step 4: The DC / AC inverter discharges the bus capacitor at a constant power equal to the preset duty cycle D multiplied by the rated power Pe, and then proceeds to Step 5;

[0023] Step 5: Control the DC converter and the DC / AC inverter respectively to achieve rapid heating of the battery pack and smooth power output;

[0024] Step 6: Determine whether the household energy storage system is allowed to generate electricity and feed it into the grid. If it is allowed, return to Step 3; otherwise, proceed to Step 7;

[0025] Step 7: Perform pulsed discharge heating during household electricity consumption. The power target of the DC / AC inverter follows the load power for adaptive adjustment, and the DC converter adjusts the pulse width according to the power.

[0026] Furthermore, the Step 5 includes:

[0027] Step 501: Control the power response speed of the DC converter within 10 milliseconds;

[0028] Step 502: The control target of the DC / AC inverter is:

[0029] When the bus voltage is lower than the minimum bus voltage U dcmin , control the power target P obj1 of the DC / AC inverter to be equal to 0;

[0030] When the bus voltage is higher than the minimum bus voltage U dcmin , and lower than the maximum bus voltage U dcmax , the power target P obj2 of the controlled DC / AC inverter is equal to the duty ratio D multiplied by the rated power Pe of the DC converter;

[0031] When the bus voltage is higher than the maximum bus voltage U dcmax , the power of the DC / AC inverter is switched to a constant U dc loop control, and the power target of the constant U dc loop control is the maximum bus voltage U dcmax plus the voltage error ΔU;

[0032] When the bus voltage is the maximum bus voltage U dcmax plus the voltage error ΔU, and the output power is lower than the duty ratio D multiplied by the rated power Pe of the DC converter, then the power target of the controlled DC / AC inverter is switched to a constant power target P obj3 equal to the duty ratio D multiplied by the rated power Pe of the DC converter, where:

[0033] The minimum bus voltage U dcmin and the maximum bus voltage U dcmax are respectively the lower limit value and the upper limit value of the bus voltage;

[0034] ΔU is the voltage error and is a positive value.

[0035] Furthermore, in step 501, the power response speed of the controlled DC converter is within 5 milliseconds.

[0036] Furthermore, the duty ratio D is 20% - 60%.

[0037] Further, the minimum state of charge SOC min of the battery pack in step 1 is 35%.

[0038] Further, the lower temperature limit T min of the temperature in step 2 is 0°C.

[0039] The innovation of a home energy storage system and its low-temperature heating control method disclosed by the present invention lies in:

[0040] Utilizing the pulse discharge characteristics of the battery cells in the battery pack to rapidly heat the battery pack, and at the same time realizing smooth power output by controlling the DC converter and the DC / AC inverter, solving the problems of low heating efficiency, high heating power consumption, and large power fluctuations in the prior art, thereby improving the performance of the home energy storage system in a low-temperature environment.

[0041] Beneficial effects: A household energy storage system and its low-temperature heating control method disclosed by the present invention have the following beneficial effects:

[0042] 1. Short heating time and high heating efficiency: By using the pulsed discharge method to rapidly heat the battery, compared with the heating sheet heating method in the prior art, the heating time is greatly shortened and the heating efficiency is significantly improved;

[0043] 2. Low heating power consumption: The energy consumption of pulsed discharge heating is only about 10% of that of heating sheet heating, greatly reducing the heating power consumption and saving energy;

[0044] 3. Power generation can still match the load to obtain benefits: While performing pulsed discharge heating, the power output of the DC / AC inverter can be controlled to follow the load power, realizing power generation and matching the load to obtain benefits;

[0045] 4. No risk of thermal runaway: Different from the heating sheet heating method in the prior art, the present invention adopts the internal heating method of the battery, and there is no risk of external heating element runaway;

[0046] 5. No increase in hardware cost: The present invention utilizes the characteristics of the battery itself for heating, without the need to increase additional hardware costs, reducing the system cost. Description of the Drawings

[0047] Figure 1 It is a schematic diagram of a household energy storage system disclosed by the present invention. Detailed Embodiments

[0048] The following details the specific embodiments of the present invention.

[0049] The "range" disclosed by the present invention is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a specific range. The range defined in this way can include the end values or not include the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 10-50 is listed for a specific parameter, ranges of 10-40 and 20-50 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise specified, the numerical range "a-b" represents the abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been fully listed herein, and "0-5" is only the abbreviated representation of these numerical combinations.

[0050] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions.

[0051] Unless otherwise specified, all technical features and optional technical features of the present application can be combined with each other to form new technical solutions.

[0052] Unless otherwise specified, all steps of the present application can be carried out in sequence or randomly, preferably in sequence. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) carried out in sequence, or may also include steps (b) and (a) carried out in sequence. For example, it is mentioned that the method may further include step (c), which means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may also include steps (a), (c) and (b), or may also include steps (c), (a) and (b), etc.

[0053] Unless otherwise specified, the "including" and "comprising" mentioned in the present application mean open-ended or may also be closed-ended. For example, the "including" and "comprising" may mean that other components not listed may also be included or comprised, or may only include or comprise the listed components.

[0054] Unless otherwise specified, the reaction is carried out under normal temperature and normal pressure conditions.

[0055] Unless otherwise specified, all parts or percentages are by weight or weight percentage.

[0056] In the present invention, the substances used are all known substances, which can be purchased or synthesized by known methods.

[0057] In the present invention, the devices or equipment used are all conventional devices or equipment known in the art and can be purchased.

[0058] Example 1

[0059] A household energy storage system consists of the following parts:

[0060] A battery pack, which is formed by sequentially connecting a plurality of battery cells in series for energy storage;

[0061] A DC converter, connected to the battery pack, for boosting the voltage of the battery pack to form high-voltage direct current to achieve bidirectional flow from the battery pack to the DC bus;

[0062] A DC / AC inverter, connected to the DC converter, for converting high-voltage direct current into alternating current for output.

[0063] Further, the battery cell is a lithium-ion battery cell.

[0064] Further, a bus capacitor is provided in the DC / AC inverter, and the DC converter is electrically connected to the bus capacitor.

[0065] A low-temperature heating control method for a home energy storage system, the home energy storage system adopting the above-mentioned home energy storage system, the steps are as follows:

[0066] Step 1: Determine whether the state of charge SOC of the battery pack is lower than a preset minimum state of charge SOC min , if it is lower, end the current operation; otherwise, go to Step 2;

[0067] Step 2: Obtain the temperature of the battery pack, and then determine whether it is lower than a preset lower temperature limit T min , if the temperature of the battery pack is lower than the preset lower temperature limit T min , then the home energy storage system enters the low-temperature working mode and executes Step 3; otherwise, return to Step 1;

[0068] Step 3: The DC converter charges the bus capacitor in the DC / AC inverter in a pulsed manner at a rated power Pe according to a preset duty cycle D, and then enters Step 4;

[0069] Step 4: The DC / AC inverter discharges the bus capacitor at a constant power equal to the preset duty cycle D multiplied by the rated power Pe, and then enters Step 5;

[0070] Step 5: Control the DC converter and the DC / AC inverter respectively to achieve rapid heating of the battery pack and smooth power output;

[0071] Step 6: Determine whether the home energy storage system is allowed to generate electricity and feed it into the grid. If it is allowed, return to Step 3; otherwise, enter Step 7;

[0072] Step 7: Perform pulsed discharge heating during home electricity consumption. The power target of the DC / AC inverter is adaptively adjusted following the load power, and the DC converter adjusts the pulse width according to the power.

[0073] Further, the Step 5 includes:

[0074] Step 501: Control the power response speed of the DC converter within 10 milliseconds;

[0075] Step 502: The control target of the DC / AC inverter is:

[0076] When the bus voltage is lower than the minimum bus voltage U dcmin , control the power target P of the DC / AC inverter obj1Equal to 0;

[0077] When the bus voltage is higher than the minimum bus voltage U dcmin , and lower than the maximum bus voltage U dcmax , control the power target P of the DC / AC inverter obj2 to be equal to the duty cycle D multiplied by the rated power Pe of the DC converter;

[0078] When the bus voltage is higher than the maximum bus voltage U dcmax , the power of the DC / AC inverter is switched to a constant U dc loop control, and the power target of the constant U dc loop control is the maximum bus voltage U dcmax plus the voltage error ΔU;

[0079] When the bus voltage is the maximum bus voltage U dcmax plus the voltage error ΔU and the output power is lower than the duty cycle D multiplied by the rated power Pe of the DC converter, then control the power target of the DC / AC inverter to switch to a constant power target P obj3 equal to the duty cycle D multiplied by the rated power Pe of the DC converter, where:

[0080] The minimum bus voltage U dcmin and the maximum bus voltage U dcmax are the lower limit value and the upper limit value of the bus voltage respectively;

[0081] ΔU is the voltage error and is a positive value.

[0082] Furthermore, the duty cycle D is 20%.

[0083] Further, the minimum state of charge SOC of the battery pack described in step 1 min is 35%.

[0084] Further, the lower temperature limit T described in step 2 min is 0°C.

[0085] Embodiment 2

[0086] A household energy storage system, which consists of the following parts:

[0087] A battery pack, which is formed by sequentially connecting a plurality of battery cells in series and is used for energy storage;

[0088] A DC converter, connected to the battery pack, is used to boost the voltage of the battery pack to form high-voltage direct current to achieve bidirectional flow from the battery pack to the DC bus;

[0089] A DC / AC inverter, connected to the DC converter, is used to convert high-voltage direct current into alternating current for output.

[0090] Further, the battery cell is a lead-acid battery cell.

[0091] Further, a bus capacitor is provided in the DC / AC inverter, and the DC converter is electrically connected to the bus capacitor.

[0092] A low-temperature heating control method for a home energy storage system, the home energy storage system adopting the above-mentioned home energy storage system, the steps are as follows:

[0093] Step 1, determine whether the state of charge SOC of the battery pack is lower than the preset minimum state of charge SOC min , if it is lower, end this operation; otherwise, enter Step 2;

[0094] Step 2, obtain the temperature of the battery pack, and then determine whether it is lower than the preset lower temperature limit T min , if the temperature of the battery pack is lower than the preset lower temperature limit T min , then the home energy storage system enters the low-temperature working mode and executes Step 3; otherwise, return to Step 1;

[0095] Step 3, the DC converter charges the bus capacitor in the DC / AC inverter in a pulsed manner at the rated power Pe according to the preset duty cycle D, and then enters Step 4;

[0096] Step 4, the DC / AC inverter discharges the bus capacitor at a constant power equal to the preset duty cycle D multiplied by the rated power Pe, and then enters Step 5;

[0097] Step 5, control the DC converter and the DC / AC inverter respectively to achieve rapid heating of the battery pack and smooth power output;

[0098] Step 6, determine whether the home energy storage system allows power generation and grid connection, if it allows, return to Step 3, otherwise enter Step 7;

[0099] Step 7, perform pulsed discharge heating during home power consumption, the power target of the DC / AC inverter follows the load power for adaptive adjustment, and the DC converter adjusts the pulse width according to the power.

[0100] Further, Step 5 includes:

[0101] Step 501, control the power response speed of the DC converter within 5 milliseconds;

[0102] Step 502, the control target of the DC / AC inverter is:

[0103] When the bus voltage is lower than the minimum bus voltage U dcmin , control the power target P of the DC / AC inverterobj1 Equal to 0;

[0104] When the bus voltage is higher than the minimum bus voltage U dcmin , and lower than the maximum bus voltage U dcmax , control the power target P of the DC / AC inverter obj2 Equal to the duty cycle D multiplied by the rated power Pe of the DC converter;

[0105] When the bus voltage is higher than the maximum bus voltage U dcmax , the power of the DC / AC inverter is switched to a constant U dc Loop control, constant U dc The power target of the loop control is the maximum bus voltage U dcmax Plus the voltage error ΔU;

[0106] When the bus voltage is the maximum bus voltage U dcmax Plus the voltage error ΔU and the output power is lower than the duty cycle D multiplied by the rated power Pe of the DC converter, then control the power target of the DC / AC inverter to switch to a constant power target P obj3 Equal to the duty cycle D multiplied by the rated power Pe of the DC converter, where:

[0107] The minimum bus voltage U dcmin And the maximum bus voltage U dcmax Are the lower limit and upper limit of the bus voltage respectively;

[0108] ΔU is the voltage error and is a positive value.

[0109] Furthermore, the duty cycle D is 60%.

[0110] Furthermore, the minimum state of charge SOC of the battery pack described in step 1 min Is 35%.

[0111] Furthermore, the temperature lower limit T described in step 2 min Is 0°C.

[0112] Embodiment 3

[0113] A home energy storage system, which consists of the following parts:

[0114] A battery pack, which is formed by sequentially connecting a plurality of battery cells in series and is used for energy storage;

[0115] A DC converter, connected to the battery pack, for boosting the voltage of the battery pack to form high-voltage direct current to achieve bidirectional flow from the battery pack to the DC bus;

[0116] A DC / AC inverter, connected to the DC converter, for converting high-voltage direct current into alternating current for output.

[0117] Further, the battery cell is a lithium-ion battery cell.

[0118] Further, a bus capacitor is provided in the DC / AC inverter, and the DC converter is electrically connected to the bus capacitor.

[0119] A low-temperature heating control method for a home energy storage system, the home energy storage system adopting the above-mentioned home energy storage system, the steps are as follows:

[0120] Step 1, determine whether the state of charge SOC of the battery pack is lower than the preset minimum state of charge SOC min , if it is lower, end the current operation; otherwise, go to Step 2;

[0121] Step 2, obtain the temperature of the battery pack, and then determine whether it is lower than the preset lower temperature limit T min , if the temperature of the battery pack is lower than the preset lower temperature limit T min , then the home energy storage system enters the low-temperature working mode and executes Step 3; otherwise, return to Step 1;

[0122] Step 3, the DC converter charges the bus capacitor in the DC / AC inverter in a pulsed manner at the rated power Pe according to the preset duty cycle D, and then enters Step 4;

[0123] Step 4, the DC / AC inverter discharges the bus capacitor at a constant power equal to the preset duty cycle D multiplied by the rated power Pe, and then enters Step 5;

[0124] Step 5, control the DC converter and the DC / AC inverter respectively to achieve rapid heating of the battery pack and smooth power output;

[0125] Step 6, determine whether the home energy storage system allows power generation and grid connection. If it allows, return to Step 3; otherwise, enter Step 7;

[0126] Step 7, perform pulsed discharge heating during home electricity consumption. The power target of the DC / AC inverter follows the load power for adaptive adjustment, and the DC converter adjusts the pulse width according to the power.

[0127] Further, Step 5 includes:

[0128] Step 501, control the power response speed of the DC converter within 8 milliseconds;

[0129] Step 502, the control target of the DC / AC inverter is:

[0130] When the bus voltage is lower than the minimum bus voltage U dcminWhen, control the power target P of the DC / AC inverter obj1 equal to 0;

[0131] When the bus voltage is higher than the minimum bus voltage U dcmin , and lower than the maximum bus voltage U dcmax When, control the power target P of the DC / AC inverter obj2 equal to the duty cycle D multiplied by the rated power Pe of the DC converter;

[0132] When the bus voltage is higher than the maximum bus voltage U dcmax When, the power of the DC / AC inverter is switched to a constant U dc Loop control, constant U dc The power target of the loop control is the maximum bus voltage U dcmax plus the voltage error ΔU;

[0133] When the bus voltage is the maximum bus voltage U dcmax plus the voltage error ΔU, and the output power is lower than the duty cycle D multiplied by the rated power Pe of the DC converter, then control the power target of the DC / AC inverter to switch to a constant power target P obj3 equal to the duty cycle D multiplied by the rated power Pe of the DC converter, where:

[0134] The minimum bus voltage U dcmin and the maximum bus voltage U dcmax are the lower limit value and the upper limit value of the bus voltage respectively;

[0135] ΔU is the voltage error and is a positive value.

[0136] Furthermore, the duty cycle D is 30%.

[0137] Further, the minimum state of charge SOC min of the battery pack in step 1 is 35%.

[0138] Further, the temperature lower limit T min in step 2 is 0°C.

[0139] Example 4

[0140] A home energy storage system, which consists of the following parts:

[0141] A battery pack, which is formed by sequentially connecting a plurality of battery cells in series and is used for energy storage;

[0142] A DC converter, connected to the battery pack, for boosting the voltage of the battery pack to form high-voltage direct current to realize the bidirectional flow from the battery pack to the DC bus;

[0143] A DC / AC inverter, which is connected to the DC converter and is used to convert high-voltage direct current into alternating current for output.

[0144] Further, the battery cell is a lead-acid battery cell.

[0145] Further, a bus capacitor is provided in the DC / AC inverter, and the DC converter is electrically connected to the bus capacitor.

[0146] A low-temperature heating control method for a household energy storage system, which uses the above-mentioned household energy storage system, and the steps are as follows:

[0147] Step 1: Determine whether the state of charge SOC of the battery pack is lower than 35%. If it is lower, end the current operation; otherwise, go to Step 2;

[0148] Step 2: Obtain the temperature of the battery pack, and then determine whether it is lower than the preset lower temperature limit T min If the temperature of the battery pack is lower than the preset lower temperature limit T min then the household energy storage system enters the low-temperature working mode and executes Step 3; otherwise, return to Step 1;

[0149] Step 3: The DC converter charges the bus capacitor in the DC / AC inverter in a pulsed manner according to a preset duty ratio D of 50% and a rated power Pe (8 kW), and then enters Step 4;

[0150] Step 4: The DC / AC inverter discharges the bus capacitor according to a constant power equal to the preset 4 kW, and then enters Step 5;

[0151] Step 5: Control the DC converter and the DC / AC inverter respectively to achieve rapid heating of the battery pack and smooth power output;

[0152] Step 6: Determine whether the household energy storage system is allowed to generate electricity and feed it into the grid. If it is allowed, return to Step 3; otherwise, enter Step 7;

[0153] Step 7: Perform pulsed discharge heating during household electricity consumption. The power target of the DC / AC inverter follows the load power for adaptive adjustment, and the DC converter adjusts the pulse width according to the power.

[0154] Further, Step 5 includes:

[0155] Step 501: Control the power response speed of the DC converter within 10 milliseconds;

[0156] Step 502: The control target of the DC / AC inverter is:

[0157] When the bus voltage is lower than the lowest bus voltage Udcmin When the voltage is 350V, control the power target P of the DC / AC inverter obj1 to be equal to 0;

[0158] When the bus voltage is higher than the minimum bus voltage U dcmin of 350V and lower than the maximum bus voltage U dcmax of 480V, control the power target P of the DC / AC inverter obj2 to be equal to 4kW;

[0159] When the bus voltage is higher than the maximum bus voltage U dcmax of 480V, the power of the DC / AC inverter is switched to a constant U dc loop control, and the power target of the constant U dc loop control is the maximum bus voltage U dcmax of 480V plus the voltage error ΔU (5V);

[0160] When the bus voltage is the maximum bus voltage U dcmax plus the voltage error ΔU (485V) and the output power is 3.8V, then control the power target of the DC / AC inverter to switch to a constant power target P obj3 equal to the duty cycle D multiplied by the rated power Pe (4V) of the DC converter, where:

[0161] The minimum bus voltage U dcmin and the maximum bus voltage U dcmax are the lower limit value and the upper limit value of the bus voltage respectively;

[0162] ΔU is the voltage error and is a positive value, which is 5V.

[0163] Furthermore, the lower temperature limit T described in step 2 min is 0°C.

[0164] Through the above steps, the present invention utilizes the pulse discharge characteristics of the battery cells in the battery pack to quickly heat the battery pack, and at the same time realizes smooth power output by controlling the DC converter and the DC / AC inverter, solving the problems of low heating efficiency, high heating power consumption and large power fluctuation in the prior art, thereby improving the performance of the household energy storage system in a low-temperature environment.

[0165] The above has made a detailed description of the embodiments of the present invention. However, the present invention is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present invention within the scope of knowledge possessed by those of ordinary skill in the art.

Claims

1. A household energy storage system, characterized in that: It consists of the following parts: A battery pack, which is composed of multiple cells connected in series and is used for energy storage; a DC converter connected to the battery pack and used to boost the voltage of the battery pack to form high-voltage DC power, so as to achieve a bidirectional flow from the battery pack to the DC bus; The DC / AC inverter is connected to the DC converter and is used to convert high-voltage DC power into AC power output.

2. A household energy storage system according to claim 1, characterized in that: The battery cell is a lithium-ion battery cell or a lead-acid battery cell.

3. A household energy storage system according to claim 1, characterized in that: The DC / AC inverter is provided with a bus capacitor, and the DC converter is electrically connected to the bus capacitor.

4. A low-temperature heating control method for a household energy storage system, using the household energy storage system according to any one of claims 1 to 3, characterized in that: Here are the steps: Step 1: Determine whether the state of charge (SOC) of the battery pack is lower than the preset minimum state of charge (SOC) min , if it is lower than , then end this operation; otherwise, go to step 2; Step 2: Obtain the temperature of the battery pack and determine whether it is lower than a preset lower temperature limit T min If the battery pack temperature is lower than the preset lower temperature limit T min , the household energy storage system enters the low temperature working mode and executes step 3; Otherwise, return to step 1; Step 3, the DC converter charges the bus capacitor in the DC / AC inverter in a pulsed manner at the rated power Pe according to a preset duty cycle D, and then proceeds to step 4; Step 4, the DC / AC inverter discharges the bus capacitor at a constant power equal to a preset duty cycle D multiplied by a rated power Pe, and then proceeds to step 5; Step 5: Control the DC converter and the DC / AC inverter respectively to achieve rapid heating of the battery pack and smooth power output; Step 6: Determine whether the household energy storage system is allowed to generate electricity and access the grid. If so, return to step 3; otherwise, proceed to step 7. Step 7: Pulse discharge heating is performed during household electricity use. The power target of the DC / AC inverter is adaptively adjusted according to the load power, and the DC converter adjusts the pulse width according to the power.

5. A low temperature heating control method for a household energy storage system as claimed in claim 4, characterized in that: The step 5 includes: Step 501, controlling the power response speed of the DC converter to be within 10 milliseconds; Step 502: The control target of the DC / AC inverter is: When the bus voltage is lower than the minimum bus voltage U dcmin When the power target P of the DC / AC inverter is controlled obj1 is equal to 0; When the bus voltage is higher than the minimum bus voltage U dcmin , and lower than the highest bus voltage U dcmax When the power target P of the DC / AC inverter is controlled obj2 It is equal to the duty cycle D multiplied by the rated power Pe of the DC converter; When the bus voltage is higher than the maximum bus voltage U dcmax When the power ring of DC / AC inverter is constant U dc Loop control, constant U dc The power target of the loop control is the maximum bus voltage U dcmax Add the voltage error ΔU; When the bus voltage is the highest bus voltage U dcmax When the output power is lower than the duty cycle D multiplied by the rated power Pe of the DC converter, the power target of the DC / AC inverter is switched to the constant power target P. obj3 It is equal to the duty cycle D multiplied by the rated power Pe of the DC converter, where: Minimum bus voltage U dcmin and the maximum bus voltage U dcmax are the lower limit and upper limit of the bus voltage respectively; ΔU is the voltage error and is a positive value.

6. A low temperature heating control method for a household energy storage system as claimed in claim 5, characterized in that: In step 501, the power response speed of the DC converter is controlled to be within 5 milliseconds.

7. A low temperature heating control method for a household energy storage system as claimed in claim 5, characterized in that: The duty cycle D is 20% to 60%.

8. A low temperature heating control method for a household energy storage system as claimed in claim 4, characterized in that: The minimum state of charge SOC of the battery pack described in step 1 min is 35%.

9. A low temperature heating control method for a household energy storage system as claimed in claim 4, characterized in that: The lower limit of temperature T in step 2 min is 0℃.

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