CN112636392B - Single-stage multi-terminal hybrid micro-grid structure suitable for low-voltage house and control method thereof - Google Patents
Single-stage multi-terminal hybrid micro-grid structure suitable for low-voltage house and control method thereof Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/388—Islanding, i.e. disconnection of local power supply from the network
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/28—Arrangements for balancing of the load in a network by storage of energy
- H02J3/32—Arrangements for balancing of the load in a network by storage of energy using batteries with converting means
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
- H02J2300/20—The dispersed energy generation being of renewable origin
Abstract
The invention discloses a single-stage multi-terminal hybrid micro-grid structure suitable for a low-voltage house and a control method thereof, wherein the single-stage multi-terminal hybrid micro-grid structure is formed by connecting a plurality of power modules in series, the power modules comprise a direct current unit and a direct current/alternating current conversion circuit, and the direct current unit is formed by connecting a direct current bus capacitor and an energy storage system in parallel; the direct current/alternating current conversion circuit comprises a main power conversion circuit and a filter circuit, and also relates to a power and supply voltage electric energy quality control method of the micro-grid structure. The invention has the advantages that: the micro-grid structure only needs single-stage power conversion, improves the efficiency of the converter, simultaneously reduces the system cost by low-bandwidth communication, and the proposed control method can reasonably utilize the power of the direct-current side power supply, automatically realize reasonable power distribution among modules according to the direct-current side state, improve the service life of the direct-current unit, automatically realize overload protection of the basic module and automatically realize stable control of the frequency and amplitude of the power supply voltage.
Description
Technical Field
The invention relates to the technical field of low-voltage house power supply, in particular to a single-stage multi-terminal hybrid micro-grid structure suitable for a low-voltage house and a control method thereof.
Background
The generation proportion of new energy is increased, the distributed renewable energy and the energy storage units thereof are largely connected into the micro-grid, and the development of the island medium-voltage micro-grid is promoted. In the past researches, the micro-grid operated by island is formed by parallel connection of multiple inverters, however, the voltage level of the distributed direct current power supply is smaller than the grid-connected voltage level in common situations, and the parallel inverters can reach the grid-connected voltage level only through two-stage power conversion boosting. The multi-inverter parallel system generally adopts droop control to realize communication-free power sharing, but the droop control has the problems of instability, inaccurate reactive power distribution and the like. On the other hand, a series inverter has been proposed, in which a low-voltage level dc power supply is connected in series to be connected to a grid after primary power conversion, and this has become an important means for connecting renewable energy sources to a power grid.
Past researches have focused on grid-connected operation of an inverter, and a plurality of stages are connected in series and then output by one voltage port, but for house power supply, the output of a plurality of ports may be required at the same time, and load power levels are different; the mere use of inverse power factor droop control may deviate the frequency and amplitude of the output voltage; and for the cascade converter, the available power of the stored energy of each direct current side is different, and the traditional mode of uniform power distribution is not applicable any more.
In order to overcome these difficulties in supplying power to a cascaded converter house, it is highly desirable to provide a structure that requires only a single stage of power conversion, has multiple output ports, and a highly reliable power distribution and supply voltage management control method.
Disclosure of Invention
The invention aims to make up the defects of the prior art, and provides a single-stage multi-terminal hybrid micro-grid structure suitable for a low-voltage house and a control method thereof.
The invention is realized by the following technical scheme:
the invention provides a single-stage multi-terminal hybrid micro-grid structure which is applied to a single-stage micro-grid system which uses an H-bridge unit formed by IGBT as a main power inverter circuit to provide stable and continuous power supply for a load, wherein the structure is formed by mutually connecting three power modules in series, the power modules comprise a direct current unit and a direct current/alternating current conversion circuit, and the direct current unit is formed by connecting a direct current bus capacitor and an energy storage system in parallel; the direct current/alternating current conversion circuit comprises a main power conversion circuit and a filter circuit, wherein the filter circuit consists of a filter inductor and a filter capacitor, the input end of the filter inductor is connected with one end of the main power inverter circuit, the output end of the filter inductor is connected with the input end of the filter capacitor, and is connected with one end of an external heavy load connection point or the output end of the filter capacitor of another power module, and the output end of the filter capacitor is connected with the output end of the filter inductor of the other power module or is connected with the other end of the external heavy load connection point; the sampling circuit of the single-ended multi-port hybrid micro-grid system mainly comprises a basic unit module sampling circuit and a backup unit module sampling circuit. The basic unit module sampling circuit comprises a sampling circuit for outputting total current to the self module, a sampling circuit for self-carrying load current of the basic unit module, a sampling circuit for voltage between load connection points and an energy storage battery information sampling circuit in a corresponding direct current unit, and information obtained by sampling is transmitted into the basic unit module controller; the backup unit module sampling circuit comprises a sampling circuit for outputting total current to the self module, a sampling circuit for supplying power current to the whole load, a sampling circuit for filtering capacitor output voltage and an energy storage battery information sampling circuit in the corresponding direct current unit, and information obtained by sampling is transmitted into the backup unit module controller.
Based on the low-voltage single-stage multi-terminal hybrid micro-grid structure, the invention also provides a control method based on the low-voltage single-stage multi-terminal micro-grid structure, which comprises the following steps: (1) The central controller obtains active power of the unit modules and state of charge (SOC) of the direct-current side battery obtained by the unit module sampling circuit in a low-bandwidth communication mode, reasonably distributes output among cascaded unit modules by the proposed method for distributing power based on the direct-current side functional quantity, and sends the calculated unit module power reference value to a unit module controller of the next layer in the low-bandwidth communication mode. (2) The unit module controller samples the output filter capacitor voltage of the unit module, outputs total current, self-carried load current and outgoing current, calculates the output total apparent power, total active power, outgoing power and power factor of external heavy load of the corresponding unit module, and uploads the output total active power information to the central controller, meanwhile receives the power reference value calculated by the central controller, controls the control quantity by the proposed output power factor adjustment method and the anti-power factor sagging control method, and performs tracking output on the control quantity by utilizing a voltage and current double closed loop so as to achieve the effect of accurate power distribution. (3) The basic unit module calculates the power factor of the corresponding unit module for external heavy load according to the voltage at two ends of the output capacitor of the unit module measured by the voltage measuring circuit and the total current output by the unit module measured by the current sensor, compares the power factor with the set limit power factor in real time, sets the reference power factor value as the limit power factor value and sets the state of charge (SOC) and the total output active power measured by the corresponding unit module as 0 once the real-time power factor is larger than the limit power factor, thereby carrying out the over-power protection of the unit module.
Preferably, the step (1) specifically includes the following steps: the central controller communicates with the unit module controllers by means of low bandwidth communication, and the central controller obtains the total active power of each unit module and the state of charge (SOC) of the direct current battery from the unit module controllers to determine the weighted average of each battery as:
wherein SOC is ，i (i=1, 2, 3) is the SOC of each battery. SOC (State of Charge) ，3 The voltages of the back-up unit module with respect to the other two base unit modules are considered.
Finally, the central controller also receives from three units P si (i=1, 2, 3) collecting active power information and distributing actual power according to the SOC.
Wherein P is soc，i Is the reference active power of the current transformer i.
Preferably, the step (2) includes the steps of: the unit control module receives the reference power from the central controller through low bandwidth communication, and according to the power and inverse power factor droop control method, the angular speed of the instantaneous reference voltage can be calculated:
wherein D is PF Is the inverse sag factor S i And lambda (lambda) i Is the apparent power and power factor of the unit i. P (P) loadi External load work being two basic unit modulesThe rate.
At the same time, the amplitude of the instantaneous reference voltage may also be determined:
E i ＝120(i＝1,2) (1-3)
wherein E is i Is a reference for the magnitude of the output voltage of each basic cell module. To compensate the terminal voltage of the heavy-load interface, the reference voltage and V of the backup unit module c Concerning V c Is the total voltage of the series power cells. k (k) p Is the proportional gain, k i Is the integral gain.
In order to avoid the influence of the power factor caused by the ripple of the line current lambda i Filtering with Low Pass Filter (LPF) with time constant of ω cut
The reference voltage for each unit module is obtained through (1-4) to (1-6) as follows:
finally, voltage and current double closed loop controllers are used for ensuring accurate voltage tracking:
wherein V is c Is the measured output voltage of the unit module, k p，v Is the proportional control gain, k i，v Is the resonant controller gain, ω c Is in radianThe cut-off frequency of the representation. k (k) inner Is the proportional gain of the inner loop controller, I si Is the measured unit module converter output current.
Preferably, the step (3) includes the steps of: the basic unit module measures the voltage of the output capacitor end of the unit module and the total output current of the module, so as to calculate the power factor of the module for external heavy load, and makes a difference with the set limit power factor, when the actual power factor is larger than the limit power factor, the reference power factor is forcedly set as the limit power factor, and the battery state of charge (SOC) and the output active power measured by the corresponding unit module are set as zero, so that the current power output is maintained, and the protected state is as follows:
ω i ＝ω * +D PF ·(λ i -λ i-lim )(i＝1,2) (1-11)
SoC i (i＝1,2)＝0 (1-12)
P si (i＝1,2)＝0 (1-13)
when the power required for heavy load increases, the basic unit module is not increasing the output power, and the power required for increasing is completely provided by the backup unit module.
The invention has the advantages that:
1. the low-voltage single-stage multi-terminal micro-grid structure formed by connecting the power unit modules in series is different from the traditional inverter mode in that a plurality of power modules are connected in series, and the DC/DC boost conversion link in the traditional micro-grid structure is omitted, so that the system cost is reduced, and the operation efficiency of the power modules is improved.
2. The special single-stage power conversion of the series structure reduces the requirement of the power module on the direct-current side input voltage level, improves the utilization rate of new energy and reduces the requirement of the micro-grid system on the new energy.
3. For external reloading, the inherent circuit attribute of the serial connection mode between the power modules enables the output currents of the power modules to be constant, the circulation problem does not exist, the use of the traditional circulation suppression equipment is avoided, and the cost is reduced.
4. The power control and supply voltage management method has the characteristics of simplicity and practicability, does not need communication among power modules, automatically realizes reasonable power distribution among unit modules, automatically realizes supply voltage control, and can protect the power of the basic unit modules from overload, thereby solving the problems of accurate power distribution and supply voltage management of the traditional island micro-grid under low-bandwidth communication.
Drawings
Fig. 1 is a schematic diagram of a low-voltage house power supply micro-grid structure provided by an embodiment of the invention;
FIG. 2 is a hierarchical control flow diagram of a low voltage single stage multi-terminal micro-grid structure provided by an embodiment of the present invention;
fig. 3 is a flowchart of overload protection control of a basic unit module according to an embodiment of the present invention;
fig. 4 is a simulation waveform diagram provided in an embodiment of the present invention.
Detailed Description
The invention is illustrated in further detail below with reference to the accompanying drawings and the specific embodiments shown in fig. 1. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
Referring to fig. 1, fig. 2, and fig. 3 fig. 4, fig. 1 is a schematic diagram of a low-voltage house power supply micro-grid structure according to an embodiment of the present invention; fig. 2 is a layered control flow chart of a low-voltage house power supply micro-grid structure provided by an embodiment of the invention; fig. 3 is a flowchart of overload protection control of a basic unit module according to an embodiment of the present invention. FIG. 4 is a simulated waveform diagram provided by an embodiment of the present invention.
The low-voltage single-stage multi-port micro-grid structure formed by connecting power modules in series as shown in fig. 1 and 2 is formed by connecting two basic unit modules and a standby unit module in series, wherein the unit modules comprise a direct current unit and a direct current/alternating current conversion circuit. The direct current unit is formed by connecting a direct current bus capacitor and an energy storage battery in parallel; the DC/AC conversion circuit comprises a main power conversion circuit and a filter circuit, wherein the filter circuit comprises a filter inductance L and a filter capacitance C f The input end of the filter inductance L is connected with one end of the main power inverter circuitThe output end of the filter inductance L and the filter capacitance C f The input end of the power module is connected with the filter capacitor C of one end of the external heavy load connection point or another power module f An output terminal of (C), a filter capacitor C f Filtering inductance L of the output end of the (C) and another power module f The output end of the external heavy load connecting point is connected or connected with the other end of the external heavy load connecting point; the sampling circuit of the low-voltage single-stage multi-port micro-grid system is divided into a sampling circuit of a basic unit controller and a sampling circuit of a backup unit controller. The basic unit module sampling circuit comprises a sampling circuit for outputting total current to the self module, a sampling circuit for self-carrying load current of the basic unit module, a sampling circuit for voltage between load connection points and an energy storage battery information sampling circuit in a corresponding direct current unit, and information obtained by sampling is transmitted into the basic unit module controller; the backup unit module sampling circuit comprises a sampling circuit for outputting total current to the self module, a sampling circuit for supplying power current to the whole load, a sampling circuit for filtering capacitor output voltage and an energy storage battery information sampling circuit in the corresponding direct current unit, and information obtained by sampling is transmitted into the backup unit module controller.
The invention aims at the low-voltage single-stage multi-terminal micro-grid layering control technology based on the power module serial connection, which comprises the following basic steps:
the first step, the central controller communicates with the basic unit module controller and the backup module controller through low bandwidth communication, and the central controller obtains the total active power of each unit module and the state of charge (SOC) of the direct current battery from the unit module controller to determine the weighted average of each battery as:
wherein SOC is ，i (i=1, 2, 3) is the SOC of each battery. SOC (State of Charge) ，3 The voltages of the back-up unit module with respect to the other two base unit modules are considered.
Finally, the central controller also receives from three units P si (i=1, 2, 3) collectionActive power information, and allocates actual power according to the SOC.
Wherein P is soc，i Is the reference active power of the current transformer i.
The second step, the unit control module receives the reference power from the central controller through low bandwidth communication, and according to the power and anti-power factor droop control method, the angular speed of the instantaneous reference voltage can be calculated:
wherein D is PE Is the inverse sag factor S i And lambda (lambda) i Is the apparent power and power factor of the unit i. P (P) loadi Is the output power of the external heavy load of the two basic unit modules.
At the same time, the amplitude of the instantaneous reference voltage may also be determined:
E i ＝120(i＝1,2) (1-3)
wherein E is i Is a reference for the magnitude of the output voltage of each basic cell module. To compensate for externally reloaded voltages, the reference voltage of the backup cell module is equal to V c Concerning V c Is the total voltage of the series power cells. k (k) p Is the proportional gain, k i Is the integral gain.
In order to avoid the influence of the power factor caused by the ripple of the line current lambda i Filtering with Low Pass Filter (LPF) with time constant of ω cut
The reference voltage for each unit module can be obtained by the formulas (4) to (6) as follows:
finally, voltage and current double closed loop controllers are used for ensuring accurate voltage tracking:
wherein V is c Is the measured output voltage of the unit module, k p，v Is the proportional control gain, k i，v Is the resonant controller gain, ω c Is the cut-off frequency in radians. k (k) inner Is the proportional gain of the inner loop controller, I si Is the measured unit module converter output current.
Thirdly, the basic unit module measures the voltage of the output capacitor end of the unit module and the current output to the external heavy load by the unit module, so as to calculate the power factor of the unit module for the external heavy load, and makes a difference with a preset limit power factor, when the power factor of the actual external heavy load is larger than the limit power factor, the reference power factor is forcibly set as the limit power factor, and the battery charge State (SOC) and the output active power measured by the corresponding unit module are set as zero, so that the current power output is maintained, and the protected state is as follows:
ω i ＝ω * +D PF ·(λ i -λ i-lim )(i＝1,2) (1-11)
SoC i (i＝1,2)＝0 (1-12)
P si (i＝1,2)＝0 (1-13)
when the power required for the heavy load increases, the base unit module maintains the current output power, and the increased power required is completely provided by the backup unit module.
In summary, the method realizes that the multiport voltage is effectively managed under the condition of no high-frequency communication line, particularly the external reloading voltage is effectively compensated, the basic unit modules can be subjected to over-power protection, the direct-current side power supply energy can be reasonably utilized among the power modules, and the reasonable power distribution in the system is automatically realized.
As a simulation waveform shown in fig. 4, the state of charge (SOC) of the direct-current side battery was set to 100% for the basic cell module 1, and 60% for the 80% backup cell module for the basic cell module 2, taking 5 seconds as a limit. The conventional constant amplitude and frequency control was used 5 seconds ago, and the method presented herein was used 5 seconds later. As can be seen from the first row and first column waveform diagrams, the power output during fixed-frequency control is: after the basic unit module 1 outputs 2028W, the basic unit module 2 outputs 2312W and the backup unit module outputs 12W and 5 seconds later the method is executed, the basic unit module 1 outputs 2330W, and the basic unit module 2 outputs 1873W and the backup unit module outputs 86W are basically the same as the direct current side SOC proportion, so that the scheme can effectively realize the accurate power distribution among the unit modules according to the direct current side state; meanwhile, the frequency waveform diagram of the first row and the second row shows that the voltage frequency of the external heavy load end is always kept constant, and the output voltage frequency of the unit module only slightly changes at the switching moment of the control scheme. The second row and the first column are the output voltage of the unit module and the output current of the external heavy load under the traditional control scheme, and the second row and the second column are the module voltage and the output heavy load current under the control of the method provided by the invention, and comparison can be known: the voltages of the basic modules 1 and 2 are basically the same in the traditional control mode, and the output voltage of the backup unit module is smaller; after the method provided by the invention is adopted, the output voltage phases of the basic unit modules are obviously different, and the voltage amplitude value output by the backup unit is obviously improved. The final function is the overload protection waveform of the basic module, so that the output power of the basic unit cannot be increased any more in the later period of overload, the power factor of external heavy load is kept constant, and the operation safety and stability of the basic power unit are ensured.
The invention is not limited to the embodiments described above. The above description of specific embodiments is intended to describe and illustrate the technical aspects of the present invention, and is intended to be illustrative only and not limiting. Numerous specific modifications can be made by those skilled in the art without departing from the spirit of the invention and scope of the claims, which are within the scope of the invention.
Claims (4)
1. A control method of a single-stage multi-terminal hybrid micro-grid structure suitable for a low-voltage house is characterized by comprising the following steps: the single-stage multi-terminal hybrid micro-grid structure suitable for the low-voltage house comprises three power modules and a sampling circuit which are connected in series, wherein two power modules are basic unit modules, the other power module is a backup unit module, the power module comprises a direct current unit and a direct current/alternating current conversion circuit, and the direct current unit is formed by connecting a direct current bus capacitor and an energy storage battery in parallel; the direct current/alternating current conversion circuit comprises a main power conversion circuit and a filter circuit, wherein the filter circuit consists of a filter inductor and a filter capacitor; the input end of the filter inductor of the first basic unit module is connected with one end of the main power conversion circuit of the filter inductor, the output end of the filter inductor is connected with the input end of the filter capacitor of the first basic unit module, and the filter inductor is connected with one end of an external heavy load, and the output end of the filter capacitor of the first basic unit module is connected with the other end of the main power conversion circuit of the filter inductor; the input end of the filter inductor of the second basic unit module is connected with one end of the main power conversion circuit, the output end of the filter inductor is connected with the input end of the filter capacitor of the second basic unit module, the output end of the filter capacitor of the first basic unit module is connected with the input end of the filter capacitor of the second basic unit module, and the output end of the filter capacitor of the second basic unit module is connected with the other end of the main power conversion circuit; the input end of the filter inductor of the backup unit module is connected with one end of the main power conversion circuit of the backup unit module, the output end of the filter inductor of the backup unit module is connected with the input end of the filter capacitor of the backup unit module, and the output end of the filter capacitor of the second basic unit module is connected with the input end of the filter capacitor of the backup unit module;
the sampling circuit comprises a basic unit module sampling circuit and a backup unit module sampling circuit, wherein the basic unit module sampling circuit comprises a sampling circuit for outputting total current to a self module, a sampling circuit for self-carrying load current of the basic unit module, a sampling circuit for voltage between load connection points and an energy storage battery information sampling circuit in a corresponding direct current unit, and information obtained by sampling is transmitted into a basic unit module controller; the backup unit module sampling circuit comprises a sampling circuit for outputting total current to the self module, a sampling circuit for supplying power current to the whole load, a sampling circuit for filtering capacitor output voltage and an energy storage battery information sampling circuit in a corresponding direct current unit, and information obtained by sampling is transmitted into the backup unit module controller;
the control method of the single-stage multi-terminal hybrid micro-grid structure suitable for the low-voltage house specifically comprises the following steps:
(1) The central controller obtains corresponding battery charge states and output power from the basic unit module controller and the backup unit module controller in a low-bandwidth communication mode, determines actual power distribution through weighted average of the charge states, and transmits distributed power reference values to the unit module controller in a low-bandwidth communication mode;
(2) The unit module controller samples the self module output total current, the filter capacitor voltage at the port, the load current carried by the module and the current additionally sent to the public load, and transmits the output total power calculated by the unit module to the upper central controller through the low-bandwidth communication system, meanwhile, the active power reference value is obtained from the central controller, and finally, the power distribution among the series units is realized through the unit module controller, wherein the backup unit module is used for compensating the voltage and the power of the heavy load port, the reference voltage of the basic unit module is a constant value, and the reference voltage of the backup unit module is changed along with the change of the load condition;
(3) The output power of the basic unit module is limited, specific parameters are set, the power of the basic unit module is controlled not to exceed a limiting value, the basic unit module is protected, and the power requirement for continuously increasing the load is provided by the backup unit module.
2. The control method of a single-stage multi-terminal hybrid micro-grid structure adapted to a low voltage house according to claim 1, wherein: the step (1) specifically comprises the following steps:
a) Sampling the output filter capacitor voltage of the unit module by using a voltage sensor, sampling the output total current of the unit module by using a current sensor, simultaneously obtaining the charge state information of the battery at the direct current side, calculating the output total power of each basic unit module and each backup unit module, and finally transmitting the calculated output active power and the battery charge state to a central controller by using a low bandwidth communication mode, wherein the weighted average SOC of each battery is determined as follows:
wherein SOC is ，i (i=1, 2, 3) is the SOC of each battery, SOC ，3 Taking into account the voltage of the backup unit module relative to the other two base unit modules;
b) The central controller transmits the obtained active power information P through the lower unit module controller si (i=1, 2, 3) and performing power distribution between the modules according to the battery state of charge,
wherein P is soc，i Is the reference active power of the current transformer i.
3. The control method of the single-stage multi-terminal hybrid micro-grid structure suitable for the low-voltage house according to claim 2, wherein the control method comprises the following steps: the step (2) specifically comprises the following steps:
a) Power reference P calculated by central controller through bandwidth communication system soc，i Is sent to each unit module controller, and finally the power sharing among the serial units is realized through the unit module controllers; to obtain a voltage transient reference, the voltage amplitude is determined as:
E i ＝120(i＝1,2) (1-3)
wherein E is i Is the reference of the voltage amplitude of the basic unit module, and in order to compensate the heavy-load terminal voltage, the reference voltage and the voltage V of the backup unit module c Concerning V c Is the voltage of the series power unit, K p3 Is a proportional gain, K i3 Is the integral gain;
b) Meanwhile, the reference phase angle obtained by applying the inverse power droop control is as follows:
wherein D is PF Is the inverse sag factor S i And lambda (lambda) i Is the apparent power and power factor, ω, of unit i * Representing a given angular frequency, W SoC，i Represents the weighted average coefficient, P, of each cell loadi Is the internal self-load power of the two basic unit modules;
power factor lambda i Filtering with low-pass filter with time constant omega cut S represents an integral factor
Wherein θ is i Is the power factor angle of the unit module;
the reference voltage of each unit module is determined by formulas (1-4) to (1-5):
c) After the instantaneous reference voltage is obtained, each basic unit module and each backup unit module are combined with the voltage at the two ends of the filter capacitor output by the unit module measured by the voltage sensor and the total current output by the unit module measured by the current sensor, and accurate voltage tracking is realized by adopting voltage-current double closed-loop control;
wherein G is V (s) represents the voltage loop control transfer function, V PC Representing the reference voltage of each unit module, V c Is to measure the voltage at two ends of the filter capacitor, k p，v Is the proportional control gain, k i，v Is the resonant controller gain, ω c Is the cut-off frequency in radians; g I (s) represents a current loop control transfer function, k inner Is the proportional gain of the inner loop controller, I si Is the measured total output current of the unit modules.
4. A control method of a single-stage multi-terminal hybrid micro-grid structure adapted to a low voltage house according to claim 3, wherein: the step (3) specifically comprises the following steps:
from the power distribution, it is concluded that the power factor is positively correlated with the base unit module output current, namely:
λ i-lim ∝I si (1-10)
wherein the method comprises the steps ofλ i For each unit module power factor, I si Outputting the total current for each unit module, and setting a power factor lambda corresponding to the corresponding power limit i-lim I.e. by determining the real-time power factor lambda i Performing over-power protection control according to the size relation; when the real-time power factor is greater than the limit power factor, the instantaneous reference angular velocity calculation formula of the basic unit module becomes:
ω i ＝ω * +D PF ·(λ i -λ i-lim )(i＝1,2) (1-11)
at the same time transmitting the battery charge state and output active power P of the corresponding unit module controller to the central controller s2 And simultaneously set to 0 to realize the over-power protection of the basic unit module, and the part with increased load power is completely provided by the backup unit module.
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| CN110572067A (en) * | 2019-08-19 | 2019-12-13 | 天津大学 | Island energy storage type power unit series micro-grid structure and control method |
| CN110690727A (en) * | 2019-09-20 | 2020-01-14 | 天津大学 | Cascading H-bridge converter flexible grid-connection method based on hierarchical voltage control |
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| CN110572067A (en) * | 2019-08-19 | 2019-12-13 | 天津大学 | Island energy storage type power unit series micro-grid structure and control method |
| CN110571796A (en) * | 2019-08-29 | 2019-12-13 | 天津大学 | Island operation cascade H-bridge micro-grid structure decentralized interleaving and layered harmonic wave treatment method |
| CN110690727A (en) * | 2019-09-20 | 2020-01-14 | 天津大学 | Cascading H-bridge converter flexible grid-connection method based on hierarchical voltage control |
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