CN103915852A - Flexible switching system based on single-phase grid-connected inverter and switching method thereof - Google Patents
Flexible switching system based on single-phase grid-connected inverter and switching method thereof Download PDFInfo
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Abstract
The invention discloses a flexible switching system based on a single-phase grid-connected inverter and a switching method of the flexible switching system based on the single-phase grid-connected inverter. The flexible switching system based on the single-phase grid-connected inverter comprises a mobile switching device and switching sets. Each switching set comprises a switching group and a self-locking circuit, wherein the switching group is composed of contactors on all phases of a power grid, the contactors, on the three phases of the power grids, in the switching group are connected in parallel, an isolation transformer, a voltage acquisition circuit and the switching group are connected to the power grid, the single-phase inverter is connected with the isolation transformer, the voltage acquisition circuit, a current acquisition circuit, a filter and the self-locking circuit, both the voltage acquisition circuit and the filter are connected with a load through grid-connected contactors, and the current acquisition circuit is connected with the load. The voltage acquisition circuits and the current acquisition circuits acquire the voltage signals and the current signals of all the switching sets and the voltage signals and the current signals of all inverters, the voltage signals and the current signals of all the switching sets and the voltage signals and the current signals of all the inverters are gathered in the single-phase inverter, then switching control signals are output to the self-locking circuits of the switching sets, the contacts on all the phases are controlled, and the states of the contactors are then maintained through the self-locking circuits. According to the flexible switching system based on single-phase grid-connected inverter and the switching method of the flexible switching system based on the single-phase grid-connected inverter, currents which can impact the load can not be generated during switching, and jump-free flexible switching is achieved.
Description
Technical field
The present invention relates to a kind of flexible switched system and changing method thereof, especially relate to a kind of flexible switched system and changing method thereof based on single-phase grid-connected inverter.
Background technology
Along with China's economic development, people's living standard is greatly improved, and the type of power consumption equipment gets more and more and power is had nothing in common with each other.Follow the extensive application of single-phase load, and there is the reasons such as ambiguity the service time of each load, cause three-phase four-wire system distribution system to occur serious three-phase imbalance running status.
In the time of threephase load unbalanced operation, negative sequence component bring great harm can to electric power system and user, be mainly reflected in following some: 1, increase the electric energy loss of circuit; 2, increase the electric energy loss of distribution transformer; 3, reducing distribution transformer exerts oneself; 4, reduce motor efficiency; 5, affect the safe operation of power consumption equipment.When threephase load unbalanced operation, three-phase output current is also uneven, causing on the neutral line has electric current to pass through, cause neutral point drifting, each phase phase voltage is changed, so just be easy to cause a phase that voltage is high with user power utilization equipment be burned, and the low phase of voltage with user's power consumption equipment possibly cannot normally use.And the neutral line has electric current to pass through, and so not only phase line is lossy, and the neutral line also produces loss, thereby increased the loss of power network line.For this reason, distribution transforming operation in the time that threephase load is uneven, the capacity of its output just cannot reach rated value, and its reserve capacity is corresponding minimizing also, and overload capacity also reduces.
Along with the fast development of the high frequency modulated technology of full-control type power device and constantly perfect, switch type inverter technology has all been tending towards ripe at the citation form of circuit and the basic sides of control, and utilization and the technological development of inverter in regenerative resource is generated electricity by way of merging two or more grid systems obtained tremendous development, for the design provides sufficient theoretical foundation.
Summary of the invention
In order to solve the problem in background technology, the object of the present invention is to provide a kind of flexible switched system and changing method thereof based on single-phase grid-connected inverter, for three-phase power distribution system, in the time there is serious imbalance in three-phase, equipment is switched in the three alternate flexibilities of carrying out, make it reach three-phase equilibrium as far as possible.When switching, single-phase inverter can be followed the tracks of former phase place, the amplitude that connects mutually and will switch phase, therefore in handoff procedure, can not produce impulse current, realizes " without flexible switching that beat ".
The technical solution used in the present invention is:
One, a kind of changing method of the flexible switched system based on single-phase grid-connected inverter:
Flexible switched system comprises the mobile switching device shifter and the switch groups that are parallel on electrical network, load is connected electrical network through mobile switching device shifter with switch groups respectively, it is characterized in that: mobile switching device shifter comprises isolating transformer, voltage collection circuit, current collection circuit, single-phase inverter, filter, grid-connected contactor, switch groups comprises by being connected in series to the switches set that contactor that electrical network respectively goes up mutually forms and being connected the latching circuit of controlling with switches set; The contactor parallel connection of the A of electrical network, B, C three-phase in switches set, isolating transformer, voltage collection circuit and switches set are connected on electrical network, single-phase inverter is connected with isolating transformer, voltage collection circuit, current collection circuit, filter and latching circuit respectively, voltage collection circuit is all connected with load by grid-connected contactor with filter, and current collection circuit is connected with load;
System voltage Acquisition Circuit, the current collection circuit size of the each phase voltage of Real-Time Monitoring electrical network, electric current respectively, carry out the computing of degree of unbalance and the bearing power of three-phase, suppose that obviously declining appears in B phase power load maximum, voltage, C phase power load minimum, meet three-phase imbalance switching condition, load need to be switched to C phase mutually by B, system is switched according to the following steps:
1) determine that the current place of load is B phase mutually, voltage collection circuit gathers the voltage signal of B phase, current collection circuit gathers the current signal of load, and the voltage signal of B phase and the current signal of load produce filtered voltage, current signal through single-phase inverter and filter filtering;
2) with the voltage signal of B phase, the amplitude to B phase, phase place are followed the tracks of as a reference, using filtered voltage, current signal as feedback signal, form two closed-loop controls, produce the driving signal of PWM, the voltage waveform that makes single-phase inverter output is stable sine wave after filter filtering;
3) when the 2nd) sine wave of step output and the voltage of B phase are during with amplitude same-phase, and closed grid-connected contactor KM, by single-phase inverter and the mutually grid-connected powering load of B;
4) single-phase inverter output switching signal is to latching circuit, and the B phase contact in cut-off switch group, by single-phase inverter powering load;
5) for C phase repeating step 1)～2) adopt the switching mode mutually identical with B, produce the mutually stable sine wave of C;
6) when the 5th) sine wave of C phase of step output and the voltage of C phase are during with amplitude same-phase, and the output switching signal of single-phase inverter is to latching circuit, and the C phase contact in Closing Switch group, by single-phase inverter and the mutually grid-connected powering load of B;
7) disconnect Strategy for Single-Phase Grid-connected Inverter contactor, complete the whole handoff procedure of B-C phase.
For each load being connected in electrical network, described mobile switching device shifter is by monitoring A, B, the voltage of C three-phase, the size of current of each switch groups, the every switch groups watt level of using formula power=voltage * Current calculation, tri-phase unbalance factor, judge whether to need to switch, determine and will switch any group load, then switch; After once having switched, repeat above-mentioned calculation procedure, then switch, until the power load balance of A, B, C three-phase or in a basic balance.
Described single-phase inverter, adopts AC-DC-AC circuit structure, comprises the not control rectifying circuit, starting resistance, DC filter capacitor, inverter circuit and the DSP control board that connect successively, and DSP control board is connected with inverter circuit and controls; And adopting PWM modulation, it is exported through the stable sine wave of filter filtering output, has isolating transformer to play the effect of isolation, in case short circuit is to the significant impact of load output before inverter.
Described voltage collection circuit, gathers the voltage of three-phase voltage for single-phase inverter tracking electrical network; The output current sampling of current collection circuit, for closed-loop control, is controlled Single-Phase Inverter Source output.
Latching circuit Wei Si road relay trigger-type control circuit in described switch groups, has auto-lock function, the state that in control maintained switch group, the contactor of each phase opens or cuts out.
Described filter is LC filter.
Two, a kind of flexible switched system based on single-phase grid-connected inverter:
Comprise the mobile switching device shifter and the switch groups that are parallel on electrical network, load is connected electrical network through mobile switching device shifter with switch groups respectively;
Mobile switching device shifter comprises:
Comprise for single-phase inverter and electrical network are isolated to the isolating transformer that carries out transformation;
Comprise the voltage collection circuit for gathering mains voltage signal;
Comprise the current collection circuit of the current signal for gathering load and single-phase inverter;
Comprise for received current signal and mains voltage signal and then produce synchronizing current and then voltage carry out the single-phase inverter of flexible switching controls, single-phase inverter output switching control signal is carried out switching controls to the latching circuit of switch groups;
Comprise the filter for single-phase inverter output signal being carried out to filtering;
Comprise the grid-connected contactor of the grid-connected control signal for receiving single-phase inverter, grid-connected contactor is connected between filter and load;
Switch groups comprises:
Comprise the switches set forming by being connected in series to the each contactor of going up mutually of electrical network, the contactor output parallel connection of the A of electrical network, B, C three-phase in switches set;
Comprise the latching circuit that is connected and controls each phase contact adhesive with switches set;
Described isolating transformer, voltage collection circuit and switches set are connected on electrical network, single-phase inverter is connected with isolating transformer, voltage collection circuit, current collection circuit, filter and latching circuit respectively, voltage collection circuit is all connected with load by grid-connected contactor with filter, and current collection circuit is connected with load.
Described single-phase inverter, adopts AC-DC-AC circuit structure, comprises the not control rectifying circuit, starting resistance, DC filter capacitor, inverter circuit and the DSP control board that connect successively, and DSP control board is connected with inverter circuit and controls.
Described filter is LC filter.
Described latching circuit Wei Si road relay trigger-type control circuit, has auto-lock function, the state that in control maintained switch group, the contactor of each phase opens or cuts out.
Compared with background technology, the beneficial effect that the present invention has is:
The present invention can make three-phase power supply system finally reach the state of three-phase equilibrium.Owing to being grid-connected after single-phase inverter output voltage and line voltage reach same amplitude same-phase, therefore in handoff procedure, do not have impulse current output, realize " without flexible switching that beat ".
Brief description of the drawings
Fig. 1 is the structural representation of the flexible switched system of the present invention.
Fig. 2 is the packet configuration schematic diagram that the flexible switched system of the present invention is connected with each load.
Fig. 3 is the control structure figure of single-phase inverter of the present invention.
Fig. 4 is the structure chart of single-phase inverter of the present invention.
Fig. 5 is the load 1 switching waveform figure of embodiment.
Fig. 6 is that the load 1 of embodiment is from A to inverter oscillogram.
Fig. 7 is that the load 2 of embodiment is from A to grid-connected oscillogram.
Fig. 8 is that the load 2 of embodiment is from grid-connected to B phase waveform figure.
Fig. 9 is that inverter current voltage oscillogram is switched in the load 2 of embodiment.
A:A phase; B:B phase; C:C phase; N: the neutral line, also claims zero line; 1: load 1; 2: load 2; 3: load 3; KM
11: C phase contact; KM
12: B phase contact; KM
13: A phase contact; KM
14: zero line contactor; T: isolating transformer; Switcher control: flexible switching device shifter; LC: filter; KM: grid-connected inverters contactor; IoS: current collection circuit; VoS: voltage collection circuit; VD1-VD 6: rectifier bridge; VD7-VD 10: inverter bridge; KM1.5: starting resistance bypass relay; Cb: bus main capacitance; L1: filter inductance; C: filter capacitor; R: load; D
pWM: PWM drives; K
i: current regulator; K
u: voltage-regulation; U
c: sinusoidal wave synthesizer; U
s: amplitude is given; ω: line voltage information; δ: phase place is given.
Embodiment
Below in conjunction with drawings and Examples, the invention will be further described.
As shown in Figure 1, the changing method of the flexible switched system of the present invention comprises: wherein flexible switched system comprises the mobile switching device shifter and the switch groups that are parallel on electrical network, load is connected electrical network through mobile switching device shifter with switch groups respectively, mobile switching device shifter comprises isolating transformer, voltage collection circuit, current collection circuit, single-phase inverter, filter, grid-connected contactor KM, and switch groups comprises by being connected in series to the switches set that contactor that electrical network respectively goes up mutually forms and being connected the latching circuit of controlling with switches set; The contactor parallel connection of the A of electrical network, B, C three-phase in switches set, isolating transformer, voltage collection circuit and switches set are connected on electrical network, single-phase inverter is connected with isolating transformer, voltage collection circuit, current collection circuit, filter and latching circuit respectively, voltage collection circuit is all connected with load by grid-connected contactor KM with filter, and current collection circuit is connected with load.
System voltage Acquisition Circuit, the current collection circuit size of the each phase voltage of Real-Time Monitoring electrical network, electric current respectively, carry out the computing of degree of unbalance and the bearing power of three-phase, suppose that obviously declining appears in B phase power load maximum, voltage, C phase power load minimum, meet three-phase imbalance switching condition, load need to be switched to C phase mutually by B, system is switched according to the following steps:
1) determine that the current place of load is B phase mutually, voltage collection circuit gathers the voltage signal of B phase, current collection circuit gathers the current signal of load, and the voltage signal of B phase and the current signal of load produce filtered voltage, current signal through single-phase inverter and filter filtering;
2) with the voltage signal of B phase, the amplitude to B phase, phase place are followed the tracks of as a reference, using filtered voltage, current signal as feedback signal, form two closed-loop controls, produce the driving signal of PWM, the voltage waveform that makes single-phase inverter output is stable sine wave after filter filtering;
3) when the 2nd) sine wave of step output and the voltage of B phase are during with amplitude same-phase, and closed grid-connected contactor KM, by single-phase inverter and the mutually grid-connected powering load of B;
4) single-phase inverter output switching signal is to latching circuit, and the B phase contact in cut-off switch group, by single-phase inverter powering load;
5) for C phase repeating step 1)～2) adopt the switching mode mutually identical with B, produce the mutually stable sine wave of C;
Being the voltage signal of collection C phase amplitude, the phase place to C phase follows the tracks of, using filtered voltage, current signal as feedback signal, form two closed-loop controls, produce the driving signal of PWM, the voltage waveform that makes single-phase inverter output is stable sine wave after filter filtering;
6) when the 5th) sine wave of C phase of step output and the voltage of C phase are during with amplitude same-phase, and the output switching signal of single-phase inverter is to latching circuit, and the C phase contact in Closing Switch group, by single-phase inverter and the mutually grid-connected powering load of B;
7) disconnect Strategy for Single-Phase Grid-connected Inverter contactor KM, complete the whole handoff procedure of B-C phase.
After having switched, mobile switching device shifter can disconnect with switch groups, for the switching of the switch groups under other loads.
For each load being connected in electrical network, described mobile switching device shifter is by monitoring A, B, the voltage of C three-phase, the size of current of each switch groups, the every switch groups watt level of using formula power=voltage * Current calculation, tri-phase unbalance factor, judge whether to need to switch, determine and will switch any group load, then switch; After once having switched, repeat above-mentioned calculation procedure, then switch, until the power load balance of A, B, C three-phase or in a basic balance.
As shown in Figure 3, Figure 4, single-phase inverter, adopts AC-DC-AC circuit structure, comprises the not control rectifying circuit, starting resistance, DC filter capacitor, inverter circuit and the DSP control board that connect successively, and DSP control board is connected with inverter circuit and controls; And adopting full-bridge circuit, PWM modulation, it is exported through the stable sine wave of filter filtering output, has isolating transformer to play the effect of isolation, in case short circuit is to the significant impact of load output before inverter.
Voltage collection circuit, gathers the voltage of three-phase voltage for single-phase inverter tracking electrical network; The output current sampling of current collection circuit, for closed-loop control, is controlled Single-Phase Inverter Source output.
Latching circuit Wei Si road relay trigger-type control circuit in switch groups, has auto-lock function, the state that in control maintained switch group, the contactor of each phase opens or cuts out.
Filter is LC filter.
Comprise the mobile switching device shifter and the switch groups that are parallel on electrical network, load is connected electrical network through mobile switching device shifter with switch groups respectively.
Mobile switching device shifter comprises:
Comprise for single-phase inverter and electrical network are isolated to the isolating transformer that carries out transformation;
Comprise the voltage collection circuit for gathering mains voltage signal;
Comprise the current collection circuit of the current signal for gathering load and single-phase inverter;
Comprise for received current signal and mains voltage signal and then produce synchronizing current and then voltage carry out the single-phase inverter of flexible switching controls, single-phase inverter output switching control signal is carried out switching controls to the latching circuit of switch groups;
Comprise the filter for single-phase inverter output signal being carried out to filtering;
The grid-connected contactor KM that comprises the grid-connected control signal for receiving single-phase inverter, grid-connected contactor KM is connected between filter and load.
Switch groups comprises:
Comprise the switches set forming by being connected in series to the each contactor of going up mutually of electrical network, the contactor parallel connection of the A of electrical network, B, C three-phase in switches set;
Comprise the latching circuit that is connected and controls each phase contact adhesive with switches set;
Isolating transformer, voltage collection circuit and switches set are connected on electrical network, single-phase inverter is connected with isolating transformer, voltage collection circuit, current collection circuit, filter and latching circuit respectively, voltage collection circuit is all connected with load by grid-connected contactor KM with filter, and current collection circuit is connected with load.
As shown in Figure 4, single-phase inverter, adopts AC-DC-AC circuit structure, comprises the not control rectifying circuit, starting resistance, DC filter capacitor, inverter circuit and the DSP control board that connect successively, and DSP control board is connected with inverter circuit and controls; And adopting full-bridge circuit, PWM modulation, it is exported through the stable sine wave of filter filtering output, has isolating transformer to play the effect of isolation, in case short circuit is to the significant impact of load output before inverter.
Filter is LC filter.
Latching circuit Wei Si road relay trigger-type control circuit, has auto-lock function, the state that in control maintained switch group, the contactor of each phase opens or cuts out; Can Wei Si road 12V latching relay module, low and high level triggers.
The present invention is grid-connected in the time that the output voltage of single-phase inverter is identical with amplitude with the phase place of line voltage, therefore in handoff procedure, does not have impulse current output, has realized " without flexible switching that beat ".
Voltage collection circuit is connected with flexible switching device shifter, for gathering A, B, the input voltage of C three-phase and the bus of inverter and output voltage; Current collection circuit gathers the electric current of each grouping and inverter, and collection signal is aggregated into single-phase inverter, realizes in handoff procedure and can not produce impulse current to load, completes " without flexible switching that beat ".
As shown in Figure 2, the switching being common under each load of the present invention, all loads are divided into groups by every group of 4KW, load 1, load 2, load 3, load 4 ... be connected in parallel on the electrical network of three-phase four-wire system, each switch groups can be switched arbitrarily between A, B, C three-phase, is ensured the adhesive of contactor after switching by latching circuit.
In specific embodiment of the invention process:
The size of system IoS current collection circuit, the each phase voltage of VoS voltage collection circuit Real-Time Monitoring, electric current, carry out three-phase equilibrium degree and each load group Power arithmetic, below taking switch groups 1 as example, suppose that obviously declining appears in B phase power load maximum, voltage, C phase power load minimum, meets three-phase imbalance switching condition.So determine load 1 to be switched to mutually C phase by B, as shown in Figure 3, system is switched according to the following steps:
1, determine that the current place of load 1 is B phase mutually, VoS voltage collection circuit gathers B phase voltage, is input to single-phase inverter;
2, with ω voltage signal, δ phase place, the U of B phase
samplitude is followed the tracks of B phase as reference, using the voltage of Single-Phase Inverter Source output, current signal as feedback signal, form two closed-loop controls, produce the driving signal of PWM, make voltage waveform stable sine wave of output after LC filter filtering of single-phase inverter output;
3, when the stable sine wave of the 2nd step output and B phase voltage are during with amplitude same-phase, closed KM grid-connected inverters contactor, mutually grid-connected with B, power to load 1 simultaneously;
4, now, single-phase inverter output switching signal, to latching circuit, disconnects B phase contact KM
12, single-phase inverter is powered separately;
5, in the time of independent power supply, inverter starts to follow the tracks of amplitude, the phase place of C phase, with second step in like manner;
6, when the stable sine wave of the 5th step output and C phase voltage are during with amplitude same-phase, single-phase inverter output switching signal is to latching circuit, closed C phase contact KM
11, inverter is mutually grid-connected with B, powers to load 1 simultaneously;
7, complete the 6th step, disconnect KM grid-connected inverters contactor, complete the whole handoff procedure of B-C phase;
8,, after having switched, mobile switching device shifter can disconnect with switch groups 1, for the switching to other switch groups.
As shown in Figure 3, the present invention adopts phase shifting control strategy, follows the tracks of B phase time, and VoS voltage collection circuit first gathers ω voltage signal, δ phase place, the U of B phase
samplitude, follow the tracks of B phase as reference, detect the zero crossing (voltage is just becoming from negative) of input voltage simultaneously, change a little value at each zero crossing or every several zero crossings by the starting phase angle of the reference signal of single-phase inverter, like this, through after a period of time, the output of single-phase inverter is identical with B.Suppose, each zero crossing changes 2 degree by the starting phase angle of the reference signal of single-phase inverter, just makes output and input homophase so through the time of 1.2 seconds.Because the angle of each phase shift is very little, therefore impulse current can not be produced or harmonic wave is very little.
After switching completes, mobile switching device shifter just can be bypassed, and departs from switch groups 1.Now, mobile switching device shifter (comprise T: isolating transformer, single-phase inverter, LC: filter, KM: grid-connected inverters contactor, IoS: current collection circuit, VoS: voltage collection circuit) continues to detect tri-phase unbalance factor, detect the electric current of each switching controls group, in the time there is three-phase imbalance, proceed the switching of other switch groups.In the time not needing to switch, whole mobile switching device shifter can bypass, from system, departs from.Above-mentioned tri-phase unbalance factor can adopt national standard: the GB-T15543-1995 quality of power supply, three-phase voltage allows degree of unbalance. State Bureau of Technical Supervision, 1994-04-06.
It is all 4KW that described each controlled switch groups maximum power, mobile switching device shifter is by monitoring A, B, the voltage of C three-phase, the size of current of each switch groups, the power of the every switch groups watt level of using formula power=voltage * Current calculation, three-phase is how many, tri-phase unbalance factor, judge whether to need to switch, determine and will switch any group load, then switch; After once having switched, repeat above-mentioned calculation procedure, then switch, until the power load balance of A, B, C three-phase or in a basic balance.
Described single-phase inverter, adopts AC-DC-AC circuit structure, and VD1-VD6 is not controlled rectifier bridge+KM1.5 starting resistance+Cb DC filter capacitor+D7-VD10 inverter bridge+LC filter.
Described inverter, adopts full-bridge circuit, PWM modulation, and it is exported through the stable sine wave of LC filter filtering output, has T isolating transformer to play the effect of isolation, in case short circuit is to the significant impact of load output before inverter.
Described VoS voltage collection circuit, gathers the voltage of three-phase voltage for single-phase inverter tracking electrical network, makes single-phase inverter output and electrical network any have mutually the same voltage of homophase frequently while needs; The output current sampling of IoS current collection circuit, for closed-loop control, is controlled Single-Phase Inverter Source output.
Below the present invention taking specific embodiment as example, because output voltage peak value exceeds oscillographic withstand voltage, so the voltage of surveying is actual 1/3 in figure below.
If Fig. 5 is that flexible switching device shifter is switched to single-phase inverter output voltage and load current condition the mutually whole process of B by load 1 mutually from A, its load 1 is 100 Europe resistance.By scheming, we can see that, in whole handoff procedure, impulse current does not appear in load, and electric current smoothly do not fluctuate, quite stable.Figure 6 shows that inverter starts to follow the tracks of A phase electrical network from closed condition, then power to load 1 with A is mutually grid-connected, through 6 all after dates, disconnect A phase electrical network and start independent power supply by single-phase inverter.In this figure, can see the process of single-phase inverter tracking A phase electrical network, the variation that phase place is adjusted, finally with A phase synchronized.
In actual electric network, there are a large amount of rectification type loads, analyze for this situation below.Load 2 is that 100 Europe resistance add a computer, is illustrated in figure 7 load 2 and supplies power to separately load current, single-phase inverter voltage condition inverter and the grid-connected power supply process of A phase electrical network from A phase electrical network.Fig. 8 is load 2 from single-phase inverter with the grid-connected power supply state of B phase electrical network to disconnecting single-phase inverter, load current, contravarianter voltage situation in the independent power supply process of B phase electrical network.Can see that by two figure in two processes, any fluctuation and impact do not appear in the electric current of load 2.Have the situation of loss although may have during the course the load of one-period rectification type, rectification type load all has large electric capacity, and therefore its load there will not be any fault, can continue normal operation.
Fig. 9 is in handoff procedure, the situation of single-phase inverter output voltage, electric current.In the time that single-phase inverter and electrical network are powered simultaneously, on single-phase inverter, there is circulation (it is too small that this experimental selection circulation suppresses inductance, and therefore circulation is larger).Two and network process, inverter output voltage does not fluctuate, but because circulation affects obviously difference of output current wave.Above-mentioned experimental result explanation is switched in the time of load voltage zero crossing, can not produce impulse current in load, can realize switching without the flexibility of beating of load.But, when grid-connected, on inverter, there is circulation, need to be suppressed, ensure the safety of equipment.
Based on the requirement of three-phase equilibrium degree, the design has proposed a kind of flexible switched system based on single-phase inverter, in the time switching, can not produce impulse current in load, realizes its flexible switching requirement.But when grid-connected, on single-phase inverter, have circulation problem, to this, the later stage need to be solved and be perfect.The danger that the design has existed while having solved manual switching, switching without the flexibility of beating at different electrical network phasetophases while having completed well load on-line operation, make three-phase equilibrium degree meet national standard, improved power supply safety and the power supplying efficiency of three phase network, there is feasibility.
Above-mentioned embodiment is used for the present invention that explains, instead of limits the invention, and in the protection range of spirit of the present invention and claim, any amendment and change that the present invention is made, all fall into protection scope of the present invention.
Claims (10)
1. the changing method of the flexible switched system based on single-phase grid-connected inverter, flexible switched system comprises the mobile switching device shifter and the switch groups that are parallel on electrical network, load is connected electrical network through mobile switching device shifter with switch groups respectively, it is characterized in that: mobile switching device shifter comprises isolating transformer, voltage collection circuit, current collection circuit, single-phase inverter, filter, grid-connected contactor, switch groups comprises by being connected in series to the switches set that contactor that electrical network respectively goes up mutually forms and being connected the latching circuit of controlling with switches set; The contactor parallel connection of the A of electrical network, B, C three-phase in switches set, isolating transformer, voltage collection circuit and switches set are connected on electrical network, single-phase inverter is connected with isolating transformer, voltage collection circuit, current collection circuit, filter and latching circuit respectively, voltage collection circuit is all connected with load by grid-connected contactor with filter, and current collection circuit is connected with load;
System voltage Acquisition Circuit, the current collection circuit size of the each phase voltage of Real-Time Monitoring electrical network, electric current respectively, carry out the computing of degree of unbalance and the bearing power of three-phase, suppose that obviously declining appears in B phase power load maximum, voltage, C phase power load minimum, meet three-phase imbalance switching condition, load need to be switched to C phase mutually by B, system is switched according to the following steps:
1) determine that the current place of load is B phase mutually, voltage collection circuit gathers the voltage signal of B phase, current collection circuit gathers the current signal of load, and the voltage signal of B phase and the current signal of load produce filtered voltage, current signal through single-phase inverter and filter filtering;
2) with the voltage signal of B phase, the amplitude to B phase, phase place are followed the tracks of as a reference, using filtered voltage, current signal as feedback signal, form two closed-loop controls, produce the driving signal of PWM, the voltage waveform that makes single-phase inverter output is stable sine wave after filter filtering;
3) when the 2nd) sine wave of step output and the voltage of B phase are during with amplitude same-phase, and closed grid-connected contactor KM, by single-phase inverter and the mutually grid-connected powering load of B;
4) single-phase inverter output switching signal is to latching circuit, and the B phase contact in cut-off switch group, by single-phase inverter powering load;
5) for C phase repeating step 1)～2) adopt the switching mode mutually identical with B, produce the mutually stable sine wave of C;
6) when the 5th) sine wave of C phase of step output and the voltage of C phase are during with amplitude same-phase, and the output switching signal of single-phase inverter is to latching circuit, and the C phase contact in Closing Switch group, by single-phase inverter and the mutually grid-connected powering load of B;
7) disconnect Strategy for Single-Phase Grid-connected Inverter contactor, complete the whole handoff procedure of B-C phase.
2. the changing method of a kind of flexible switched system based on single-phase grid-connected inverter according to claim 1, it is characterized in that: for each load being connected in electrical network, described mobile switching device shifter is by monitoring A, B, the voltage of C three-phase, the size of current of each switch groups, the every switch groups watt level of using formula power=voltage * Current calculation, tri-phase unbalance factor, judge whether to need to switch, determine and will switch any group load, then switch; After once having switched, repeat above-mentioned calculation procedure, then switch, until the power load balance of A, B, C three-phase or in a basic balance.
3. the changing method of a kind of flexible switched system based on single-phase grid-connected inverter according to claim 1, it is characterized in that: described single-phase inverter, adopt AC-DC-AC circuit structure, comprise the not control rectifying circuit, starting resistance, DC filter capacitor, inverter circuit and the DSP control board that connect successively, DSP control board is connected with inverter circuit and controls; And adopting PWM modulation, it is exported through the stable sine wave of filter filtering output, has isolating transformer to play the effect of isolation, in case short circuit is to the significant impact of load output before inverter.
4. the changing method of a kind of flexible switched system based on single-phase grid-connected inverter according to claim 1, is characterized in that: described voltage collection circuit, gathers the voltage of three-phase voltage for single-phase inverter tracking electrical network; The output current sampling of current collection circuit, for closed-loop control, is controlled Single-Phase Inverter Source output.
5. the changing method of a kind of flexible switched system based on single-phase grid-connected inverter according to claim 1, it is characterized in that: the latching circuit Wei Si road relay trigger-type control circuit in described switch groups, there is auto-lock function, the state that in control maintained switch group, the contactor of each phase opens or cuts out.
6. the changing method of a kind of flexible switched system based on single-phase grid-connected inverter according to claim 1, is characterized in that: described filter is LC filter.
7. the flexible switched system based on single-phase grid-connected inverter, comprises the mobile switching device shifter and the switch groups that are parallel on electrical network, and load is connected electrical network through mobile switching device shifter with switch groups respectively, it is characterized in that:
Mobile switching device shifter comprises:
Comprise for single-phase inverter and electrical network are isolated to the isolating transformer that carries out transformation;
Comprise the voltage collection circuit for gathering mains voltage signal;
Comprise the current collection circuit of the current signal for gathering load and single-phase inverter;
Comprise for received current signal and mains voltage signal and then produce synchronizing current and then voltage carry out the single-phase inverter of flexible switching controls, single-phase inverter output switching control signal is carried out switching controls to the latching circuit of switch groups;
Comprise the filter for single-phase inverter output signal being carried out to filtering;
Comprise the grid-connected contactor of the grid-connected control signal for receiving single-phase inverter, grid-connected contactor is connected between filter and load;
Switch groups comprises:
Comprise the switches set forming by being connected in series to the each contactor of going up mutually of electrical network, the contactor output parallel connection of the A of electrical network, B, C three-phase in switches set;
Comprise the latching circuit that is connected and controls each phase contact adhesive with switches set;
Described isolating transformer, voltage collection circuit and switches set are connected on electrical network, single-phase inverter is connected with isolating transformer, voltage collection circuit, current collection circuit, filter and latching circuit respectively, voltage collection circuit is all connected with load by grid-connected contactor with filter, and current collection circuit is connected with load.
8. a kind of flexible switched system based on single-phase grid-connected inverter according to claim 7, it is characterized in that: described single-phase inverter, adopt AC-DC-AC circuit structure, comprise the not control rectifying circuit, starting resistance, DC filter capacitor, inverter circuit and the DSP control board that connect successively, DSP control board is connected with inverter circuit and controls.
9. a kind of flexible switched system based on single-phase grid-connected inverter according to claim 7, is characterized in that: described filter is LC filter.
10. a kind of flexible switched system based on single-phase grid-connected inverter according to claim 7, it is characterized in that: described latching circuit Wei Si road relay trigger-type control circuit, there is auto-lock function, the state that in control maintained switch group, the contactor of each phase opens or cuts out.
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