CN110149044B - 两级式变换器及其启动方法、llc变换器和应用*** - Google Patents
两级式变换器及其启动方法、llc变换器和应用*** Download PDFInfo
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- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/36—Means for starting or stopping converters
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/01—Resonant DC/DC converters
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- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
- H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
- H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
- H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
- H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
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- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
- H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
- H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
- H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
- H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/33538—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only of the forward type
- H02M3/33546—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only of the forward type with automatic control of the output voltage or current
- H02M3/33553—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only of the forward type with automatic control of the output voltage or current with galvanic isolation between input and output of both the power stage and the feedback loop
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- H02M3/00—Conversion of dc power input into dc power output
- H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
- H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
- H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
- H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
- H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/33569—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
- H02M3/33573—Full-bridge at primary side of an isolation transformer
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/4807—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode having a high frequency intermediate AC stage
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
- H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
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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
- H02J2300/22—The renewable source being solar energy
- H02J2300/24—The renewable source being solar energy of photovoltaic origin
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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
- H02J3/381—Dispersed generators
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/0003—Details of control, feedback or regulation circuits
- H02M1/0006—Arrangements for supplying an adequate voltage to the control circuit of converters
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/0067—Converter structures employing plural converter units, other than for parallel operation of the units on a single load
- H02M1/007—Plural converter units in cascade
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/4815—Resonant converters
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- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
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Abstract
本发明提供的两级式变换器及其启动方法、LLC变换器和应用***,通过两级式变换器中LLC变换器的控制器,首先控制其主电路按照预设周期为后级变换器的直流母线进行打嗝充电,使后级变换器的直流母线电压逐渐升高,直至后级变换器的辅助电源开始工作,进而为其控制器供电;待后级变换器的控制器输出检测得到的自身直流母线电压之后,再由LLC变换器的控制器判断LLC变换器的输出电压是否上升到打嗝启动电压;若是,则LLC变换器的控制器控制LLC变换器的主电路进入打嗝稳压阶段,进而通过LLC变换器代替现有技术中增加的开关和缓起电阻来为后级变换器提供稳定的直流母线电压,避免了现有技术中***体积大和成本高的问题。
Description
技术领域
本发明涉及自动控制技术领域,特别涉及一种两级式变换器及其启动方法、LLC变换器和应用***。
背景技术
含有LLC拓扑的两级式变换器,能够实现电能的隔离变换;比如图1所示的三相级联模块化光伏固态变压器,其每一相中的各个模块,分别包括一个隔离型DCDC变换器和一个H桥变换器;该隔离型DCDC变换器采用LLC变换器时,一个模块即为一个含有LLC拓扑的两级式变换器;该含有LLC拓扑的两级式变换器的结构可以是如图2所示的两电平拓扑,也可以是如图3所示的三电平拓扑。
图1所示的***,其隔离由每个模块中前级LLC变换器的高频变压器来实现,并通过配置一定数目的模块,可以实现与35kV中压电网直接连接,从而省去笨重的工频隔离变压器,降低***的重量和体积。但是由于H桥变换器的控制器只能通过相应的辅助电源从H桥变换器的母线电压取电,而不能从LLC变换器的母线电压取电(如图4所示),所以图1所示的整个***启动时,为了使其各个模块中H桥变换器的控制器能够工作,需要先给各个H桥变换器的直流母线充电。
现有技术中通常采用图5a所示的电路结构,在***启动时通过电网为各个H桥变换器的直流母线供电;其具体过程是:先闭环开关S1,由电网通过缓起电阻R和电感L给H桥变换器的直流母线充电;当H桥变换器的直流母线电压达到预设值时,闭合开关S2,进而旁路缓起电阻R、减小***的损耗。这种充电方法虽然简单可靠,但是需要增加开关S2和缓起电阻R,会增大***的体积和成本。
发明内容
本发明提供一种两级式变换器及其启动方法、LLC变换器和应用***,以解决现有技术中由于需要增加开关和缓起电阻来为H桥变换器的直流母线充电,而导致的***体积大和成本高的问题。
为实现上述目的,本申请提供的技术方案如下:
本发明一方面提供一种两级式变换器的启动方法,应用于所述两级式变换器中LLC变换器的控制器,所述两级式变换器的启动方法包括:
控制所述LLC变换器的主电路按照预设周期为后级变换器的直流母线进行打嗝充电,使后级变换器的辅助电源工作、为后级变换器的控制器供电;
根据后级变换器的控制器检测并输出的后级变换器的直流母线电压,判断所述LLC变换器的输出电压是否上升到打嗝启动电压;
若所述LLC变换器的输出电压上升到所述打嗝启动电压,则控制所述LLC变换器的主电路进入打嗝稳压阶段。
优选的,所述预设周期包括:充电阶段和等待阶段;
控制所述LLC变换器的主电路按照预设周期为后级变换器的直流母线进行打嗝充电,包括:
在所述充电阶段,控制所述LLC变换器的主电路为后级变换器的直流母线充电;以及,
在所述等待阶段,对所述LLC变换器的主电路进行封波控制。
优选的,控制所述LLC变换器的主电路为后级变换器的直流母线充电,为以下任意一种:
采用定频调制方式,控制所述LLC变换器主电路中左右两个桥臂的移相角从180°开始逐渐减小,为后级变换器的直流母线充电;
采用定频调制方式,控制所述LLC变换器主电路驱动信号占空比从0逐渐增大,为后级变换器的直流母线充电;
采用变频调制方式,控制所述LLC变换器主电路的开关频率从预设初始值开始逐渐减小,为后级变换器的直流母线充电。
优选的,控制所述LLC变换器的主电路进入打嗝稳压阶段,包括:
若所述LLC变换器的输出电压上升到打嗝峰值电压,则对所述LLC变换器的主电路进行封波控制;
若所述LLC变换器的输出电压下降到打嗝谷值电压,则控制所述LLC变换器的主电路重新启动充电。
优选的,控制所述LLC变换器的主电路重新启动充电,为以下任意一种:
采用定频调制方式,控制所述LLC变换器主电路中左右两个桥臂的移相角重新从180°开始逐渐减小,进而实现启动充电;
采用定频调制方式,控制所述LLC变换器主电路驱动信号占空比重新从0逐渐增大,进而实现启动充电;
采用变频调制方式,控制所述LLC变换器主电路的开关频率重新从预设初始值开始逐渐减小,进而实现启动充电。
优选的,在控制所述LLC变换器的主电路按照预设周期为后级变换器的直流母线进行打嗝充电之后,还包括:
判断是否接收到后级变换器的通讯信息;
若接收到后级变换器的通讯信息,则与后级变换器建立通讯,再执行根据后级变换器的控制器检测并输出的后级变换器的直流母线电压,判断所述LLC变换器的输出电压是否上升到打嗝启动电压的步骤;
若在预设时长内未接收到后级变换器的通讯信息,则对所述LLC变换器的主电路进行封波控制。
优选的,所述预设时长为连续N个预设周期的时长;N为正整数。
本发明另一方面提供一种两级式变换器的LLC变换器,包括:主电路、辅助电源和控制器;
所述控制器用于执行如上述任一所述的两级式变换器的启动方法;
所述主电路的输入端直流母线通过所述辅助电源为所述控制器供电。
本发明第三方面提供一种两级式变换器,包括:如上述所述的两级式变换器的LLC变换器,以及,与所述LLC变换器输出端相连的后级变换器;
所述LLC变换器的控制器与所述后级变换器的控制器之间通讯连接;
所述后级变换器的控制器通过另一辅助电源从所述后级变换器的主电路的输入端直流母线取电。
优选的,所述后级变换器为H桥变换器。
本发明第四方面提供一种两级式变换器的应用***,包括如上述所述的两级式变换器。
本发明提供的两级式变换器的启动方法,通过所述两级式变换器中LLC变换器的控制器,首先控制所述LLC变换器的主电路按照预设周期为后级变换器的直流母线进行打嗝充电,使后级变换器的直流母线电压逐渐升高,直至后级变换器的辅助电源开始工作,进而为后级变换器的控制器供电;待后级变换器的控制器输出检测得到的自身直流母线电压之后,再由LLC变换器的控制器根据接收到的后级变换器的直流母线电压,判断所述LLC变换器的输出电压是否上升到打嗝启动电压;若所述LLC变换器的输出电压上升到所述打嗝启动电压,则LLC变换器的控制器控制所述LLC变换器的主电路进入打嗝稳压阶段,进而通过所述LLC变换器代替现有技术中增加的开关和缓起电阻来为后级变换器提供稳定的直流母线电压,避免了现有技术中***体积大和成本高的问题。
附图说明
为了更清楚地说明本发明实施例或现有技术内的技术方案,下面将对实施例或现有技术描述中所需要使用的附图作简单地介绍,显而易见地,下面描述内的附图仅仅是本发明的一些实施例,对于本领域普通技术人员来讲,在不付出创造性劳动的前提下,还可以根据这些附图获得其他的附图。
图1是现有技术提供的三相级联模块化光伏固态变压器的结构示意图;
图2和图3是现有技术提供的两级式变换器的两种电路图;
图4是现有技术提供的两级式变换器的结构示意图;
图5a至图5c是现有技术提供的H桥变换器的三种充电方式示意图;
图6a和图6b是本发明申请实施例提供的两级式变换器的启动方法的流程图;
图7是本发明申请实施例提供的LLC变换器的输出电压波形示意图。
具体实施方式
下面将结合本申请实施例中的附图,对本申请实施例中的技术方案进行清楚、完整地描述,显然,所描述的实施例仅仅是本申请一部分实施例,而不是全部的实施例。基于本申请中的实施例,本领域普通技术人员在没有作出创造性劳动前提下所获得的所有其他实施例,都属于本申请保护的范围。
两级式变换器的***开始启动时,后级变换器(比如图2和图3中的H桥变换器)输入端的直流母线没有电压或者说达不到其辅助电源的启动电压,因此后级变换器的控制器不能正常工作,后级变换器无法对其直流母线电压进行采样和通讯传输,使得LLC变换器的控制器无法获得LLC变换器的输出电压。在此场景下,LLC变换器和后级变换器的控制器都无法对LLC变换器的输出电压进行采样和软件保护,硬件保护电路也不能正常工作。
此时,LLC变换器工作于空载启动模式,在***没有保护的情况下,若启动方式不合适,很可能造成输出电压过压,损坏设备。为了避免上述情况的发生,同时避免现有技术中由于需要增加开关和缓起电阻来为H桥变换器的直流母线充电,而导致的***体积大和成本高的问题,本发明提供一种两级式变换器的启动方法,应用于两级式变换器中LLC变换器的控制器,该两级式变换器中,位于前级的变换器为含有LLC拓扑的变换器,比如图2或图3所示的形式;当然,也可以为其他形式,此处仅为一种示例,并不仅限于此。
具体的,请参见图6,该两级式变换器的启动方法包括:
S101、控制LLC变换器的主电路按照预设周期为后级变换器的直流母线进行打嗝充电,使后级变换器的辅助电源工作、为后级变换器的控制器供电;
由于后级变换器的控制器的辅助电源需要一定的时间,通常需数秒,才能实现启动,所以本实施例通过步骤S101,采用打嗝充电的方式,按照预设周期为后级变换器的直流母线进行边充边等的间歇式充电,以防止LLC变换器的输出电压充电过快,而后级变换器的辅助电压来不及启动。
该预设周期,如图7所示,包括:充电阶段(如图7中Δt1所示的时间段)和等待阶段(如图7中Δt2所示的时间段);本步骤中的控制LLC变换器的主电路按照预设周期为后级变换器的直流母线进行打嗝充电,具体包括:在充电阶段,控制LLC变换器的主电路为后级变换器的直流母线充电;以及,在等待阶段,对LLC变换器的主电路进行封波控制。对LLC变换器的主电路进行封波控制,是指控制LLC变换器的主电路内全部开关管均关断。
优选的,在充电阶段,控制LLC变换器的主电路为后级变换器的直流母线充电,可以采用以下任意一种具体方式:
采用定频调制方式,控制LLC变换器主电路中左右两个桥臂的移相角从180°开始逐渐减小,为后级变换器的直流母线充电;
采用定频调制方式,控制LLC变换器主电路驱动信号占空比从0逐渐增大,为后级变换器的直流母线充电;
采用变频调制方式,控制LLC变换器主电路的开关频率从预设初始值开始逐渐减小,为后级变换器的直流母线充电。
也就是说,在每个充电阶段之初,若LLC变换器采用定频调制方式,则其主电路左右两个桥臂的移相角要从180°逐渐减小,或者占空比从0逐渐增大;而若LLC变换器采用变频调制方式,则其主电路开关频率要从一个较大的预设初始值开始逐渐减小。这样做的目的是,防止启动之初LLC变换器的谐振电感电流和输出电压会有较大冲击,进而实现对于***启动时的进一步保护。
S102、根据后级变换器的控制器检测并输出的后级变换器的直流母线电压,判断LLC变换器的输出电压是否上升到打嗝启动电压。
通过步骤S101使LLC变换器在每个预设周期内,都先启动Δt1时间,再封波Δt2时间,依次类推,周而复始,使LLC变换器的输出电压,也即后级变换器的直流母线电压,逐渐升高,如图7中前半部分多个Δt1和Δt2所示的台阶状。
后级变换器的直流母线电压逐渐升高,首先达到其控制器的辅助电源的工作电压VST1,过一段时间之后,辅助电源正常启动、为其控制器供电;其控制器开始工作,与LLC变换器的控制器建立通讯;并且,当后级变换器的控制器检测得到后级变换器的直流母线电压之后,通过通讯传输给LLC变换器的控制器,使LLC变换器的控制器得知后级变换器的直流母线电压,也即LLC变换器的输出电压。
在建立通讯之前,LLC变换器的控制器无法获知其输出电压,因此处于图7中所示的盲充阶段。
在LLC变换器的控制器收到后级变换器的控制器上传的信息后,可以根据其上传的信息对LLC变换器的输出电压进行软件保护,即进入图7所示的软件保护起作用阶段。在此阶段,LLC变换器的控制器一直判断LLC变换器的输出电压是否上升到打嗝启动电压VST2;当LLC变换器的输出电压是否上升到打嗝启动电压VST2之后,则执行步骤S103。
S103、控制LLC变换器的主电路进入打嗝稳压阶段。
如图7中的打嗝稳压阶段所示,当LLC变换器的控制器通过通讯检测到其输出电压上升到打嗝峰值电压VP2时,对LLC变换器的主电路进行封波控制。由于后级变换器辅助电源的消耗,LLC变换器的输出电压会有所下降,当其下降到打嗝谷值电压VP1时,LLC变换器的控制器又控制LLC变换器的主电路重新启动充电。如此周而复始,可以把LLC变换器的输出电压稳定到一定的区间内。
与盲充阶段的打嗝充电同样优选的,控制LLC变换器的主电路重新启动充电,可以采用以下任意一种:
采用定频调制方式,控制LLC变换器主电路中左右两个桥臂的移相角重新从180°开始逐渐减小,进而实现启动充电;
采用定频调制方式,控制LLC变换器主电路驱动信号占空比重新从0逐渐增大,进而实现启动充电;
采用变频调制方式,控制LLC变换器主电路的开关频率重新从预设初始值开始逐渐减小,进而实现启动充电。
也就是说,打嗝稳压阶段内,LLC变换器每次重新启动充电时,若采用定频调制方式,则其主电路左右两个桥臂的移相角要从180°逐渐减小,或者占空比从0逐渐增大;而若采用变频调制方式,则其主电路开关频率要从一个较大的预设初始值开始逐渐减小。这样做的目的是,防止启动之初LLC变换器的谐振电感电流和输出电压会有较大冲击。此阶段由于LLC变换器可以通过通讯获知其输出电压,一旦输出过压,可以通过软件来实现***的保护,即也处于该软件保护起作用阶段内。
采用图7所示的打嗝盲充与打嗝稳压两阶段启动方式,可使类似图2和图3这种含有LLC拓扑的两级式变换器,能够安全且平滑地实现启动,并且无需现有技术中增加的开关和缓起电阻,避免了现有技术中***体积大和成本高的问题。
值得说明的是,现有技术中也存在图5b所示的充电方案,即通过前级的LLC变换器来为后级变换器提供直流母线电压,但是该方案由于在H桥变换器的控制器启动前无法获得LLC变换器的输出电压,所以需要额外增加电压检测功能,以实现稳压控制和过压保护,否则LLC变换器在空载或者轻载下直接启动,会由于电路短时大浪涌电流而瞬间会损坏器件,且LLC变换器的输出电压也会在启动瞬间达到较高的值,有可能引起器件过压。因此,现有技术中还存在一种图5c所示的方案,即给LLC变换器的输出侧增加假负载,从而加重LLC变换器的负载,以便在启动时,方便对其输出电压进行控制,并在启动后,把该假负载切除,以降低***不必要的损耗。然而,在做高压大功率变换器时,增加假负载会加大***的体积,不利于整个变换器的功率密度。
而本实施例提供的该两级式变换器的启动方法,无需采取任何硬件措施,即可通过上述过程来为后级变换器提供直流母线电压,不仅无需额外增加电压检测功能,而且也无需增加假负载,避免了现有技术中成本高或者***体积大和功率密度低的问题。
本发明另一实施例还提供了另外一种两级式变换器的启动方法,在上述实施例及图6a和图7的基础之上,优选的,如图6b所示,在步骤S101的控制LLC变换器的主电路按照预设周期为后级变换器的直流母线进行打嗝充电之后,还包括:
S201、判断是否接收到后级变换器的通讯信息;
若接收到后级变换器的通讯信息,则依次执行步骤S202和S102;若在预设时长内未接收到后级变换器的通讯信息,则执行步骤S203。
S202、与后级变换器建立通讯。
S203、对LLC变换器的主电路进行封波控制。
优选的,该预设时长为连续N个预设周期的时长;N为正整数。也就是说,若在连续的多个(Δt1+Δt2)时间,LLC变换器的控制器始终无法接收到后级变换器的控制器发送过来的通讯信息,这有可能是LLC变换器出现故障或者后级变换器的辅助电源或者控制器通讯功能出现故障,所以需要LLC变换器直接进行封波;如果不及时封波,则LLC变换器的输出电压有可能达到较高的值,进而损坏设备。在LLC变换器的控制器收到后级控制器通过通讯上传的信息后,可以根据其上传的信息获得LLC变换器输出电压,进而对其进行软件保护。
本实施例在上述实施例的基础之上,在其盲充阶段不仅进行边充边等的打嗝充电,而且等待一定时间后若LLC变换器的控制器未收到后级变换器的控制器通过通讯上传的信息,则视为***故障,进而保护设备不被损坏。
本发明另一实施例还提供了一种两级式变换器的LLC变换器,包括:主电路、辅助电源和控制器;
其主电路的输入端直流母线通过其辅助电源为其控制器供电(如图4所示);
并且,其主电路的电路结构可以如图2-4所示,也可以采用其他形式,只要包括LLC拓扑的结构均在本申请的保护范围内。
其控制器用于执行上述任一实施例所述的两级式变换器的启动方法;该两级式变换器的启动方法参见上一实施例即可,此处不再一一赘述。
本发明另一实施例还提供了一种两级式变换器,包括:LLC变换器,以及,与LLC变换器输出端相连的后级变换器;
LLC变换器的控制器与后级变换器的控制器之间通讯连接;
后级变换器的控制器通过另一辅助电源从后级变换器的主电路的输入端直流母线取电。
优选的,该后级变换器为H桥变换器。
该LLC变换器的控制器如上述实施例所述,此处不再赘述。
该两级式变换器可以如图2-图4所示,需要说明的是,图3和图4中的M、N和O是为了展示节点连接关系,并且实际应用中图2-图4中各个开关管的形式也不仅限于图中展示的内容,实际应用中可以使用I GBT,也可以使用MOSFET,视其具体应用环境而定,只要包括LLC拓扑且应用上述启动方法的两级式变换器,均在本申请的保护范围内。
另外,任何应用该两级式变换器的***,比如图1所示的三相级联模块化光伏固态变压器,均在本申请的保护范围内。
本发明中各个实施例采用递进的方式描述,每个实施例重点说明的都是与其他实施例的不同之处,各个实施例之间相同相似部分互相参见即可。对于实施例公开的装置而言,由于其与实施例公开的方法相对应,所以描述的比较简单,相关之处参见方法部分说明即可。
以上所述,仅是本发明的较佳实施例而已,并非对本发明作任何形式上的限制。虽然本发明已以较佳实施例揭露如上,然而并非用以限定本发明。任何熟悉本领域的技术人员,在不脱离本发明技术方案范围情况下,都可利用上述揭示的方法和技术内容对本发明技术方案做出许多可能的变动和修饰,或修改为等同变化的等效实施例。因此,凡是未脱离本发明技术方案的内容,依据本发明的技术实质对以上实施例所做的任何简单修改、等同变化及修饰,均仍属于本发明技术方案保护的范围内。
Claims (11)
1.一种两级式变换器的启动方法,其特征在于,应用于所述两级式变换器中LLC变换器的控制器,所述两级式变换器的启动方法包括:
控制所述LLC变换器的主电路按照预设周期为后级变换器的直流母线进行打嗝充电,使后级变换器的辅助电源工作、为后级变换器的控制器供电;
待后级变换器的控制器开始工作且与后级变换器的控制器建立通讯后,根据后级变换器的控制器检测并输出的后级变换器的直流母线电压,判断所述LLC变换器的输出电压是否上升到打嗝启动电压;
若所述LLC变换器的输出电压上升到所述打嗝启动电压,则控制所述LLC变换器的主电路进入打嗝稳压阶段。
2.根据权利要求1所述的两级式变换器的启动方法,其特征在于,所述预设周期包括:充电阶段和等待阶段;
控制所述LLC变换器的主电路按照预设周期为后级变换器的直流母线进行打嗝充电,包括:
在所述充电阶段,控制所述LLC变换器的主电路为后级变换器的直流母线充电;以及,
在所述等待阶段,对所述LLC变换器的主电路进行封波控制。
3.根据权利要求2所述的两级式变换器的启动方法,其特征在于,控制所述LLC变换器的主电路为后级变换器的直流母线充电,为以下任意一种:
采用定频调制方式,控制所述LLC变换器主电路中左右两个桥臂的移相角从180°开始逐渐减小,为后级变换器的直流母线充电;
采用定频调制方式,控制所述LLC变换器主电路驱动信号占空比从0逐渐增大,为后级变换器的直流母线充电;
采用变频调制方式,控制所述LLC变换器主电路的开关频率从预设初始值开始逐渐减小,为后级变换器的直流母线充电。
4.根据权利要求1所述的两级式变换器的启动方法,其特征在于,控制所述LLC变换器的主电路进入打嗝稳压阶段,包括:
若所述LLC变换器的输出电压上升到打嗝峰值电压,则对所述LLC变换器的主电路进行封波控制;
若所述LLC变换器的输出电压下降到打嗝谷值电压,则控制所述LLC变换器的主电路重新启动充电。
5.根据权利要求4所述的两级式变换器的启动方法,其特征在于,控制所述LLC变换器的主电路重新启动充电,为以下任意一种:
采用定频调制方式,控制所述LLC变换器主电路中左右两个桥臂的移相角重新从180°开始逐渐减小,进而实现启动充电;
采用定频调制方式,控制所述LLC变换器主电路驱动信号占空比重新从0逐渐增大,进而实现启动充电;
采用变频调制方式,控制所述LLC变换器主电路的开关频率重新从预设初始值开始逐渐减小,进而实现启动充电。
6.根据权利要求1-5任一所述的两级式变换器的启动方法,其特征在于,在控制所述LLC变换器的主电路按照预设周期为后级变换器的直流母线进行打嗝充电之后,还包括:
判断是否接收到后级变换器的通讯信息;
若接收到后级变换器的通讯信息,则与后级变换器建立通讯,再执行根据后级变换器的控制器检测并输出的后级变换器的直流母线电压,判断所述LLC变换器的输出电压是否上升到打嗝启动电压的步骤;
若在预设时长内未接收到后级变换器的通讯信息,则对所述LLC变换器的主电路进行封波控制。
7.根据权利要求6所述的两级式变换器的启动方法,其特征在于,所述预设时长为连续N个预设周期的时长;N为正整数。
8.一种两级式变换器的LLC变换器,其特征在于,包括:主电路、辅助电源和控制器;
所述控制器用于执行如权利要求1-7任一所述的两级式变换器的启动方法;
所述主电路的输入端直流母线通过所述辅助电源为所述控制器供电。
9.一种两级式变换器,其特征在于,包括:如权利要求8所述的两级式变换器的LLC变换器,以及,与所述LLC变换器输出端相连的后级变换器;
所述LLC变换器的控制器与所述后级变换器的控制器之间通讯连接;
所述后级变换器的控制器通过另一辅助电源从所述后级变换器的主电路的输入端直流母线取电。
10.根据权利要求9所述的两级式变换器,其特征在于,所述后级变换器为H桥变换器。
11.一种两级式变换器的应用***,其特征在于,包括如权利要求9所述的两级式变换器。
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